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Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

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Old 08-10-2017, 12:05 PM   #301
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

I wouldnt worry to much on the 9". Its not that bad. What tranny you going with? Th400 does eat power but strangely doesnt always mean car slows down alot. If converter multiplies torque correctly it will make up for it some
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Old 08-10-2017, 12:25 PM   #302
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

I concur about the LQ's. my stock bottom end 5.3 has been trouble free and I got the early 99 version and doesnt even have the floating rods. With an Lq4 or LQ9 you wouldnt have to pull anything, just the front cover for a cam and your done (plus valve springs).

To make it even more entising... Fitech just releases self tuning boost capable EFI system for $795. Complete bolt on for custom cams, uses all the stock sensors and is 30psi boost capable with no add ons. 70050 is non tranny controlled $795 and 70051 is tranny controlled for any 4l60E or 4L80e and only costs $995 i think.

I just orderd the 70050 for my 5.3 with 11psi and hoping it will work flawlessly. The stock system is suck a PITA to tune.
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Old 08-10-2017, 12:26 PM   #303
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

If Going to upgrade the tranny, get a 4l80e, Fitech 70051 and a junk yard Lq4 and throw 20+psi at it
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Old 08-10-2017, 07:06 PM   #304
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Definitely going 80e because I plan to do 1/2 mile events. I was already looking at computer options and leaning back towards the MS3. I like the Holley Dominator but it is huge and there is no place to conceal it in my dash. Also the Holley system really adds up in costs. Looking at harness options for the Gen1, I'll be stuck building the harness again. Another point to the LS option, because both the Megasquirt and the FiTech have a plug and play harness. I really like the fact that the FiTech does it all in one box that is able to fit in the stock ECM location (unlike the Holley). As a final bonus to going LS, I can sell my gen 1 parts to cover a good portion of the base costs to acquire the engine etc.

The cheapest I can stay gen1 is to keep the MS2, add a CAN connector and buy a microsquirt to run the Transmission. I'd be stuck with batch fire. I'd still need to shell out a lot of money on the shortblock to make this thing live. I'll be at least $7000 into the shortblock and transmission controller. I would potentially have 400+ cubic inches though and a bottom end that is absolutely capable of withstanding 1000 crank hp.


Going LQ if I stay super cheap and simply file the rings and upgrade to studs and head gaskets, get some ported stock heads and upgrade the springs and cam, add the FBody required pan and accessories, and buy the FiTech I'll be at $4000. I could sell the Gen1 Fastburn heads, intake, shortblock, MS2, etc for at least 2500 so a net of $1500. On the plus side I'd have sequential, coil per cylinder, and a better computer. On the negative I'd have a bottom end that could let go if I push 1000 through it too much. But I'd have a $5500 to upgrade the bottom end.


Seems like a no-brainer doesn't it?
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Old 08-10-2017, 07:21 PM   #305
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

I mean... Duh!

personally people always say u can build the bottom end for 1000hp but it could let go at 800 or 600 or **** just idling, it's always a crap shoot. I would say go cheapest route the stock LS stuff is pushed so hard it's ridiculous. Plus you won't be making 1000hp all the time lol.

The MS has a ton more options and features it's crazy but really they aren't a tuning/engine company... more software. Just like HP tuners. I've read too many people having issues with the MS stuff chasing there tails in tuning and it being bad hardware. I'm giving FItech a whirl and ill let you know how it goes. I won't be pushing it as hard as you but I can let u know how it's performing and tuning with a laptop. I can say the HP custom OS (2bar) has been perfect and glitch free. So I'm sure the 3 bar OS is also good but u just loose the resolution. I just don't have the knowledge to tune **** like airflow tables and tables that modify other tables. And I don't have the time. Hopefully the self tuning will take care of that and I'll hard tune the timing and boost fuel tables.
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Old 08-10-2017, 09:09 PM   #306
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Yes I am very interested to see how the FiTech does. Honestly I am probably one of those people who the LQ engine would last a long time for. I don't venture to the track all that often (1.5 hr minimum drive each way) and most of my street blasts are short. The 1/2 mile events I usually get 3-6 runs and did maybe 2 events per year in the GT-R. I know this much though, I don't want to dump a bottom end on the far end of the half mile (oil!).


I hate to re-do it all over but this year I can afford to buy all that I need to convert and do it right. Last year I was busy trying to pay for the shop build so I went the cheaper route of upgrading the existing engine. Also I get a lot of my money back on the stuff I bought last year. It just occurred to me I can sell this gen 1 header/turbo setup for a few dollars to further offset costs.

I'll be doing a lot of math this week. I have to make my choice asap before this 700 lets go and I'll be out of a running race car again.
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Old 08-11-2017, 05:29 PM   #307
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

I went the route of ditching the sbc and buying a 6.0 LS and I bought a MS3Pro. That sucker does everything and it has a drop on ls harness
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Old 08-27-2017, 06:13 PM   #308
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Ugh.. haven't driven it in two weeks due to working on the house and an eclipse vacation to Tennessee. Today I took it to lunch and the grocery store and on the way back opened up the cutout and let it hit 12.5 psi in third twice. It felt ok but I almost feel like it should be stronger at 12.5. Mixture was dead on at 11.0. Anyway the second time I let out I heard a big exhaust leak on one cylinder. Upon inspection at home, it blew out a 2 inch long section of the Remflex gasket. I find that hard to even imagine happening. Those gaskets are tough as nails. It hasn't had any leaks at all up to this point (other than a hole forming in the other header primary tube where I welded the center tubes together). Big job, expensive gasket and no idea why it did this. The only variable is my front end is lower and the K Member crossmember is not as prominent as the oem one. I scraped something on the ground lightly today and it could have been the crossover exhaust tube.


Oh well I was going to pull the passenger header off to deal with the hole so I guess I'll just take everything off now so I can deal with it.


Also today an old friend visited me. Hot start lean conditions. After driving around with the coolant at 200-205 and shutting down for lunch, the restart brought A/F of 14.9 to 15.9 instead of the usual 14.2 to 14.8. Considering this is the third engine combo (including rails, intake, etc) and the 4th or 5th fuel pump/fuel line/regulator combination, I'm sure the only possible cause of this is the Megasquirt 2. Frustrating to see that back but overall it was fun driving around today.
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Old 08-27-2017, 09:04 PM   #309
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Can't see the remflex gasket blowing out unless u got a ton of exhaust pressure. That could also be why it doesn't feel fast at 12.5psi. I run about that and mines only at redline and it's fast lol. This is the first time I've ever used the remflex and have to say I'm impressed and I've run a lot of different gaskets Over the years. But I'd try to figure out why it blew out and if you got some kind of restriction on the hot side or maybe the turbo is too small?

Sucks to hear about the MS. Maybe you just need to take fuel out at higher engine temps? Reason is if you shut off at 200-205 and go to start up its prob closer to 220-225 until you circulate the coolant alittle.
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Old 08-28-2017, 04:31 AM   #310
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

I checked the flange bolts last night but the end bolt is a socket head and all I had handy was a box end wrench. All of the other bolts were tight. I'll wait for it to cool down before trying to get to the socket head in that tight space. It looks tight or at least it hasn't backed out any. I'm certain there was no damage to the gasket during installation. Definitely no back pressure with this turbo compared to my last and the cutout was wide open when it happened.


You mean add fuel at higher temps. I've always thought the problem was a result of the MS built in MAT based fuel correction. The following information is given in the MS2/Extra instructions:


"If the engine runs lean and roughly after hot starts for about a minute or two, then settles to normal, check your air temperature sensor readings. Often, this is caused by sensor heat soak, where the sensor absorbs more heat from the intake manifold than the air does. There are several approaches you can take to fixing this.
  • If using a closed element air temperature sensor, switch to an open element type.
  • Sensors located in the intake manifold are especially prone to this – try relocating the sensor to the intake piping.
  • Use the “Ignore MAT correction during ASE” option to turn off the air density correction for the time when after start enricment is active.
  • Adjust the MAT correction curve to add more fuel at high air temperatures."

The only thing I'm not sure about is the Ignore MAT correction setting. I've probably done that already since I've done everything else listed. MS has a built in fuel correction algorithm based on IAT and CLT Temp and the only adjustment you get is 50 to 100% correction. I've always felt that correction was a little too aggressive and was the main factor in this problem. I've just learned to live with it.
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Old 08-28-2017, 07:54 AM   #311
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Yea sorry, I meant richen it up for hot starts. I'm having a similar problem with my LS PCM. Cold and hot I have a 15-30s extreme lean condition where I can barely get it to idle and have my foot on the pedal a smudge to keep it idling. Then it's like he fuel kicks in and it will go from 19:1 to 14:1 and idle fine. It sounds extremely dead through the exhaust like it's super lean and then you can hear it add fuel and sounds like a normal engine. I have yet to find the culprit and it seems like afterstart doesn't help and cranking fuel doesn't seem to be the issue. It's that first 15-30s like it's keeping fuel out for some reason. And all the tables have so many modifiers that everything I do makes it worse I guess. This is why I'm going FItech and I got my harness like 2 weeks ago. Waiting to install tho as the season is almost over in a month or so.

Are you running an open element IAT?

Maybe relocate it out of the engine bay if you have piping that runs to the bumper area.
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Old 08-28-2017, 05:10 PM   #312
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Yep it is open element and in the charge tubing instead of intake, though I have it not too far ahead of the throttle body. I should have looked to see what the IAT was when it was acting up this time.


As for the gasket.. the socket head bolt on the back side of the cylinder 7 exhaust flange was the naughty one.. loose as a goose. No fun taking that header off with that silly power steering/AC bracket that goes to the front bolt on these cars.
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Old 08-28-2017, 06:49 PM   #313
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

I use allen head bolts with a shaved down swivel allen socket. Makes headers short work.

As for the MS, i have IAT sensor in the fender where the blower inlet filter is - The blower outlet to throttle body pipe heat soaked every time. even then i got a occasional hot start, so i just added a bit more ASE to compensate for it, and by the time the ASE turns off EGO and closed loop IAC takes over. I usually like mine to idle at 13.5-14.0 AFR - provides a smoother idle with my setup.
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Old 08-29-2017, 09:10 AM   #314
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

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I use allen head bolts with a shaved down swivel allen socket. Makes headers short work.

As for the MS, i have IAT sensor in the fender where the blower inlet filter is - The blower outlet to throttle body pipe heat soaked every time. even then i got a occasional hot start, so i just added a bit more ASE to compensate for it, and by the time the ASE turns off EGO and closed loop IAC takes over. I usually like mine to idle at 13.5-14.0 AFR - provides a smoother idle with my setup.

Agreed on the IAT placement. Anything I put over the front of the engine gets heat soaked especially when your not moving and shut the engine off. I would see a 50*F increase shutting a 180*F engine off and letting it sit for just a few min. After startup IATs would gradually drop back after airflow starts moving. But even as your moving hot air from the radiator is blowing all over the front of the motor and up into the intake tube thus still causing some form of heat soak. So moving it out and over to the fender areas will help.

I thought the Remflex was designed to crush and keep tension on the exhaust bolts? Reason I ask is I run SS header studs with a serated nut only (nothing special) and they haven't loosened up after weeks of starting and running and cooling. Perhaps a better header bolt is required on your setup? I'm not a fan of stage 8, but even something with a lock washer might help especially if its loosening up on you and hard to get at.

Side note... just remove those triangular brackets. I haven't run mine in years I dont think they do a whole lot. But I do run a TDS wonderbar, STB and a moly Kmember.
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Old 08-29-2017, 09:27 AM   #315
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Remflex will crush to fill voids in uneven surfaces but bolts will back out. Mine have but i usually catch it before it hurts a gasket. Seems to happen with all headers and gaskets
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Old 09-13-2017, 05:26 AM   #316
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

New gasket is in.. Thank goodness I built these headers and made everything easily accessible. Also welded up the hole that developed in a primary tube. It looked like a plasma torch where it was hitting the next primary tube. The second tube has even rainbowed a 2-3 inch area from the heat in that area. Crazy.


Also added in v-band gaskets on the 2.5's. I misplaced the 3 inch gaskets yesterday so today I'll go on the hunt so I can put the downpipe back in. And I had to hack up a 3" silicone coupler clamp and weld the threaded portion to one of my v-band clamps that broke off. Looks like it will work fine but order some new ones since my stock has depleted. Along with that I ordered a Remflex T4 gaskets. I'm sick of leaks! Somewhere I have a leak and I want it gone.


Would have already had it back on the road if not for being in the middle of a complete kitchen remodel and dealing with a hurricane! Luckily it stayed to my east and all is well in my area.
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Old 09-13-2017, 08:29 AM   #317
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Sounds good! I jumped on the turbo bandwagon. got my CX kit on the way with the small 76/65 turbo, the 5.3 should spool it super quick but not run out of steam with the 5.3 till 6+k which is my limit. Hoping for 600whp as my 72lb injectors are maxed at 800ish hp.

Didnt realize remflex had a T4 gasket... going to have to get one of those! Love my remflex header gasket, ordered a new one for the turbo headers.

Glad you made out with the storm, my parents vacation property survived as well supposedly.
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Old 09-13-2017, 11:08 AM   #318
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

I hope you get that combo together soon. I'm once again at the crossroads and would love to see what it does for you.


Meanwhile I'm hoping to take this one to the track in the next few weekends to see what it will do for a mph. I just want to see 100+ in the 1/8 and I'll feel like I'm on the right path. If it's in the 90's I'm out of this setup. The transmission of course is slipping on the 2-3 shift so that will hurt some, but it still should easily make 100+.


I've always felt this DIY megasquirt is part of the lower than expected numbers but LS engines have such great ecm options (with a plug and play harness to boot!). If I see one more stock 5.3 make better numbers than me I'm going LS!!
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Old 09-14-2017, 07:21 PM   #319
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

I continue to be disappointed with performance. I'm not feeling the 'scary' feeling that I've always felt in other turbo v8 cars. Quick it is.. damn quick. Not fast though.


I raised boost another 2-3 psi today and it didn't 'come alive'. I would think it should already be shredding the tires at 10 psi (closed cutout) and certainly at 12 (open). These are old, worn and narrow ET Streets. Not the case before and still not the case with the added boost. It is rich at the new boost (10.6:1) so there is a bit of power to be picked up with leaning but I don't think that's going to bridge the gap. The car just feels too slow for the combo and 12-14 psi.

According to my MS timing table I'm requesting 32 degrees at 6000 rpm at 13 psi. That means I'm getting 25 degrees, which is still pretty high for 93 at those parameters. High compared to any timing tables I've seen posted for any turbo v8's at least. I don't think I want to risk adding timing to that range.


Once again feeling at a loss. I want to track it but I'm going to be so incredibly disappointed if I see a 9x mph that I will probably end up hurting the car in anger. It is not nosing over or doing anything to indicate ignition problems (not like I'm running a ton of boost to cause that). I just have the feeling it isn't going to get there from here.


Going to go datalog now and see if I spot a trend.
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Old 09-14-2017, 10:00 PM   #320
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Well scratch that 13 psi thing.. it actually is making 18.5 and that's with the cutout closed. It went immediately into over-boost protection - 21.75 psi - when we opened the cutout. I mean instantly too. Wow I have to say this turbo moves a lot of air and it spools incredibly fast!


But it is making 18.5 psi. That is even worse because now I don't have the option of just increasing the boost to make the power I want. I mean I can increase it but there isn't as much left as I thought. We drove around with the cutout open quite a bit and I am starting to think the ignition is suspect. I think coil per cylinder and sequential injection would make a huge improvement on this thing too. For now I may need to consider better plug wires and coil.


I did shoot some video during tonight's drive so I'll upload and link that soon.
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Old 09-15-2017, 07:35 AM   #321
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

I yearn for the day 18lbs feels slow. lol
PS are your rings gapped and whats your PCV system consist of?

Last edited by 86CamaroDan; 09-15-2017 at 07:42 AM.
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Old 09-15-2017, 08:47 AM   #322
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

what size spring are you running in the Wastegate? IS your wastegate too undersized and thus your PSI is so high?

Honestly if your way higher in boost than you want you need to lower the PSI on the wastegate spring, or increase the size of the WG so it can flow the amount of exhaust needed to lower boost. The high boost could be blowing out the spark. I think you should prob lower it to 12-15psi and get the tune dialed in (check your IATs) and then put a manual or electronic boost controller and turn it up and tune. Then you can lower it back down and turn it up when you need it. All that extra PSI is just creating heat if your not getting extra power out of it. Basically if your engine feels just as fast at the 18.5psi with the cutout closed and it doesnt feel noticeably faster at 21.5psi then your out of the efficiency range of that 76/75 turbo. Might need to step it up to a billet wheel or go with a larger unit like the 83 or something.
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Old 09-15-2017, 05:41 PM   #323
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

I have a T in the boost reference line.. without the T is makes 10.5 psi with the cutout closed and 12.5 with it open. If I tied the wastegate back into the downpipe it would not have the difference. I put in the T expecting 2-3 psi but ended up getting 8+. I can adjust that with a length of hose but the point isn't that it's making so much boost, it is that the car should be much faster at that boost level than it seems to be.
Turbo is definitely not out of air at all. It's CEA Gen 2 BB rated to 1300 hp (1000 for v8). I think the power is being limited by something as it always has with this car. The one thing that has been consistent since the early days is the DIY Megasquirt 2 and the coil isn't anything too special (low end MSD external HEI). Might be time for a Blaster coil equivalent.
I wasn't planning to have to run 18-20 psi any more. I expected to easily be in the mid 6 1/8 by 15 psi.
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Old 09-15-2017, 05:43 PM   #324
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Yes everything in the bottom end was set up for 25 psi except the block itself and the rods being pretty weak. Rings are total seal gapped to whatever I did at the time with high boost in mind.


Nothing special on the PCV, no vacuum pump or anything fancy.
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Old 09-15-2017, 05:44 PM   #325
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

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Old 09-15-2017, 09:22 PM   #326
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

do you think your actual timing could be wrong? (retarded) something in the megasquirt screwing it up or possibly something else?

any way to lock timing in place to test a wot pull?

on engine masters they just put 25psi through a cast piston 350 sbc using a non intercooled procharger with 116 fuel. made around 750 at the flywheel.

Last edited by DIGGLER; 09-15-2017 at 09:30 PM.
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Old 09-15-2017, 10:30 PM   #327
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

I'm going to try something new tomorrow.. I don't like free revving engines to high rpm but I'm going to see what the timing is doing at 6000 rpm. I'm estimating 7 degrees of error at 6000 rpm based on when I've seen in the past at 4000 rpm.


With the cutout open I can definitely hear a breakup but it wasn't there at 12 psi.. no surprise at 20+ psi.


Ignition related issues are the only likely thing going wrong here. I think I can get it sorted out.
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Old 09-15-2017, 11:12 PM   #328
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

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I'm going to try something new tomorrow.. I don't like free revving engines to high rpm but I'm going to see what the timing is doing at 6000 rpm. I'm estimating 7 degrees of error at 6000 rpm based on when I've seen in the past at 4000 rpm.


With the cutout open I can definitely hear a breakup but it wasn't there at 12 psi.. no surprise at 20+ psi.


Ignition related issues are the only likely thing going wrong here. I think I can get it sorted out.
stay with it. i think the car should really rip at that boost level like you said. also, in the higher boost you might need some more spark oompfh as mentioned.
i ran a ms2 in my car, but i controlled all my ignition stuff with a msd dig.7, crank trigger, billet distributor, and HVC-2 coil. pretty simple setup in that the crank trigger told the box when to fire the coil, and i had the ms2 triggering off one of the tach outputs from the ignition box.
my ms2 only fired the injectors, and seemed to do a pretty good job at that.
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Old 09-16-2017, 11:18 PM   #329
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Is there a way to put a crank trigger on a gen1 without having to move accessories forward 1/8 inch? That would require a complete reworking of the power steering/AC brackets on mine.


Always a damned uphill battle with this project. LS looks better every day but that's a whole other battle.
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Old 09-17-2017, 02:13 PM   #330
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

could possibly machine 1/8" off the neck of the balancer. also, you can buy a balancer from ati with magnet/s installed for a crank trigger. would be a pricier option, though.
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Old 09-18-2017, 08:44 AM   #331
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

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Originally Posted by ZZ3Astro View Post
Is there a way to put a crank trigger on a gen1 without having to move accessories forward 1/8 inch? That would require a complete reworking of the power steering/AC brackets on mine.


Always a damned uphill battle with this project. LS looks better every day but that's a whole other battle.
Are you running an OEM balancer or aftermarket/SFI? If OEM look and see if a Vortec one will do the trick since it is already spaced.

I hate to ask this because I think it may have been answered before, but did you ever measure back pressure?

Also, what springs are you running in the valvetrain? Wondering if you could be conflating ignition issues for valve float.
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Old 09-18-2017, 11:37 AM   #332
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

I'm running an aftermarket SFI balancer. I don't recall the brand, nothing fancy though for this stockish bottom end.


Springs are a good topic now that I'm running more boost than I expected. I don't have enough spring for the 18+psi. I didn't plan to run more than 10-12 psi on the stock bottom end because that should be plenty with this head/intake combo. It was all part of my plan to keep the power down to a reasonable level that this relatively weak bottom end could withstand until funding was in place for a real short block.


So yes Drac0nic, your idea of valve float is a very good point that I was not considering.

Specs for the current valve springs:


GM 12625033 Beehive
Seat Pressure: 90 lbs @ 1.800'' 1.800"
Open Pressure: 295 lbs @ 1.150''
Max lift .570"
Spring Rate: 332 lbs/in

Specs for the beehive springs I had on the old setup (113 heads) are:


Comp Cams 26918-16 Beehive
Seat Pressure: 125 lbs @ 1.800''
Open Pressure: 367 lbs @ 1.150''
Coil Bind: 1.100"
Max lift .625"
Spring Rate: 372 lbs/in


Looks like I need to move those over to the Fastburn heads now.


Also I was looking way back into my posts.. I found where I tested my timing error in 2012 with the following results:


850 RPM - dead on the table
3000 RPM - 5 degrees behind table
5000 RPM - 9 degrees behind table


Based on that I am calculating 11.25 degrees behind the table at 6000 rpm. I was scratching my head over these same issues 5 years and two engine combos ago!
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Old 09-18-2017, 01:21 PM   #333
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

When I was running a 36-1 wheel I had a SFI balancer machined down so the wheel would sandwich behind the crank pulley and have no alignment issues.

I actually still have the wheel, trigger, balancer, oil pump driver, etc in the shop.
I didn't like the ignition module (EDIS) and coil packs. One day I'll try it out again with LS2 coils.

-- Joe
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Old 09-18-2017, 05:00 PM   #334
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Thats intresting. Wonder whats doing that and if mines doing the same thing.
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Old 09-18-2017, 05:27 PM   #335
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Found this posted in another forum:


"A typical OEM 4 pin module is limited to 5 amps output so as to avoid overheating the coil and module itself. This is more than enough amperage IF you have enough time. If you do not allow sufficient charge time (High RPM) then you must push additional amperage through the module and into the coil to assure the coil is charged up enough to provide the level of spark you need. Most high performance aftermarket HEI modules are available in a 7.5 amp output version. Now it is important to realize this additional current may cause problems (excess heat) in the coil and there for it is wise to upgrade to a matched coil also. With these two upgrades there should be adequate spark energy through the13:1 compression ratio and 6000 RPM range.
There is a timing retard that occurs at a rate of approximately 1* to 1.5* per 1000 RPM after full advance is reached. This is due to the Magnetic pick up trigger and not the module. I do not interpret this as a problem for most of us and I believe that high speed retard devices are becoming popular for a little more MPH. Hmm We have a built in device….The reason the HEI system retards the total timing the way it does is this: as the pole piece spins inside the magnet (pick up coil) it creates an AC voltage signal (looks like a wave).The module uses this signal to trigger the coil. The module looks for the back side of the wave to cross the zero point to fire. As the pole piece spins faster it creates a larger AC wave and that larger wave crosses zero a little later and we have a later firing time (retarded timing)."


http://www.chevelles.com/forums/13-p...ve-3k-rpm.html


I haven't dug into this problem lately but I'm going to do some more reading on it now.
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Old 09-18-2017, 05:34 PM   #336
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Seeing a number of posts referencing a GM official acknowledgment of 1 to 1.5 degrees per 1000 rpm HEI retard due to the design of the pickup coil and electronics slew rate. I think with my DIY MS2 being consumer grade off the shelf components, it has its own slew rate issues which are multiplying the "normal" slew rate of the HEI pickup by the MS slew rate.
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Old 09-18-2017, 07:39 PM   #337
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Quote:
Originally Posted by anesthes
When I was running a 36-1 wheel I had a SFI balancer machined down so the wheel would sandwich behind the crank pulley and have no alignment issues.

I actually still have the wheel, trigger, balancer, oil pump driver, etc in the shop.
I didn't like the ignition module (EDIS) and coil packs. One day I'll try it out again with LS2 coils.

-- Joe
Joe you're actually agreeing with everyone and are thinking it is related to ignition lol?

He already answered his problem in the video, but is overlooking it. If his duty cycle, air/fuel and RPM sum up on a targeted horsepower, but he is not "breaking the tires loose", or "has to let go of the throttle so the trans can shift", then this clearly points to the transmission. Either he is blowing through the converter, or his detent is completely off because of the newer style throttle body, or the trans is just toast. If the RPM is there, if his duty cycle and air fuel are there, but he is not feeling the "scary fast" sensation, then the power he is making is not reaching the wheels...

- Rob
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Old 09-19-2017, 08:10 AM   #338
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

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Originally Posted by Street Lethal View Post
Joe you're actually agreeing with everyone and are thinking it is related to ignition lol?

He already answered his problem in the video, but is overlooking it. If his duty cycle, air/fuel and RPM sum up on a targeted horsepower, but he is not "breaking the tires loose", or "has to let go of the throttle so the trans can shift", then this clearly points to the transmission. Either he is blowing through the converter, or his detent is completely off because of the newer style throttle body, or the trans is just toast. If the RPM is there, if his duty cycle and air fuel are there, but he is not feeling the "scary fast" sensation, then the power he is making is not reaching the wheels...

- Rob
from the vids i watched, it didnt seem an obvious trans slippage issue, imo. not discounting the trans altogether, but im leaning away from it at this point. and blowing through the converter would be more of a going straight to 5k+ and staying there.

im no tuning guru whatsoever... but if you pull 11 degrees out and then adjust your a/f.... you are still 11 degrees out, right?
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Old 09-19-2017, 08:25 AM   #339
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Quote:
Originally Posted by Street Lethal View Post
Joe you're actually agreeing with everyone and are thinking it is related to ignition lol?
It's possible. A lot of problems exist with the trigger on HEI, especially the small cap with the 8 pin module. That's why we use thunderbolt ignitions on our boats, we need dead reliable advance curves. Try pulling 5 skiers out of the water from a dead stop with a faulty ignition system..

I've brought this up a few times before, but guys seem to not quite comprehend the difference in reliability requirements between a drag car and a boat. The faster a drag car goes, the less time you need it to be reliable for. If it runs @ WOT, doesn't overheat, etc for 10 seconds you are happy as pie. In a boat, we need to hold 6,000 rpm ALL DAY lol. To go 80mph in a 6500lb boat, holeshot, etc requires a lot more power than a 3200lb drag car too.


Anyhow, most aftermarket ECU's have a spark error correction feature, so he could take advantage of that if needed.

Or toss a vortec cover and run CNP, which is what I would do if I didn't have a freaking 400 block

His MS can use just about ANY ignition trigger that exists. If he can't get the error correction sufficient for his HEI, toss it and go with something else.

-- Joe
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Old 09-19-2017, 02:50 PM   #340
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Spark has always been an issue with this ecm/hei combo for me. I've always had to compensate in the spark tables but it was easier when I was barely turning 5k. Now with 6200+ and the error being exponential, it's just silly. Also my timing has never looked stable with a timing light when turning up the rpm. It has always moved around a few degrees while watching it even with the timing locked in the various tables.


Transmission slip in 3rd gear is possible but it is definitely not slipping in 1st or 2nd at all. The 3rd gear clutches were showing signs of slippage when I had it apart a couple thousand miles ago. Fluid still looks/smells perfect. It is clearly not engaging 3rd gear under WOT but if I let out and get back in it the rpm locks down and does not flare upward.


Am I wrong to think this car should be out of control in at least 1st gear? These ET's are almost to the wear bar and I bought them USED about three years ago. If it was making 700 at the crank I'd think even 2nd gear would be spin happy on certain pavement types given the condition of the tires and zero traction enhancements to the car (aside from rear mounting the battery). Now I can stomp it from a stop and yes it will spin 1st and 2nd but it has yet to break traction under a rolling start.


I'm thinking crank trigger but I'd really like coil per cylinder and my MS2 won't do that. Also if I do a crank trigger don't I still need a cam position signal reference as well even if I still use the distributor? And if so, won't the built in retard of that still have negative effects on the timing? Or is that only needed for CPC? I just need to bite the bullet on the Holley system so I can control a 4L80e anyway. But not in the mood to spend an extra 3k at the moment.
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Old 09-19-2017, 02:51 PM   #341
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

ZZ3Astro,
GM used a latency table in the GM ECMs which is for the HEI trigger and Module. Apply this table (advance) to your new ECM.

Stock and aftermarket HEI modules are not that impressive. The only GM single coil / module pair I found worth using is is the LT1 & Vortec setup. It is an external module with heatsink (7.5 AMPs) and has a coil with great Inductance and internal resistance (as good as aftermarket coils).

At your RPMs, you need a good module and coil, or you need more coils.

EDIT: As for the trans, it may or may not be slipping. I would get the ignition retard, and low spark output fixed first.

Last edited by junkcltr; 09-19-2017 at 02:58 PM.
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Old 09-19-2017, 03:59 PM   #342
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

As junk and I both mentioned, a spark error table exists to tune around the limitations of hei.

Your ms2 will drive 8 LS2 coils wasted spark. LS2 coils are nice because they have built in dwell.

You don't need a cam sensor unless doing sequential injection.
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Old 09-19-2017, 04:07 PM   #343
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Bingo! But Ive also read about a good bit of MS hardware issues. I'm sure you wouldnt have issues with some of the better LS hardware/software. Or through a MSD LS1/2 controller box with preset timing curves and boost capability and call it a day lol.
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Old 09-19-2017, 04:08 PM   #344
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

I went with a relatively low cost attempt at a solution. Since I'm on the fence about LS I didn't want to put big money into this until I see some improvement. I ordered a crank trigger wheel and hall effect sensor from DIYAutoTune ($83 total shipped). I will have to fabricate a bracket but no big deal.


I should see improvement in the timing accuracy with that. If it feels like an improvement I'm going to start digging through my piggy banks for a better ECM solution. I will be coil per cylinder on this car at some point, LS or not.
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Old 09-19-2017, 04:33 PM   #345
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Quote:
Originally Posted by customblackbird View Post
Bingo! But Ive also read about a good bit of MS hardware issues. I'm sure you wouldnt have issues with some of the better LS hardware/software. Or through a MSD LS1/2 controller box with preset timing curves and boost capability and call it a day lol.
Most of the hardware issues are from people who assemble them and shouldn't, or wiring issues that blow out a component. (Like driving a 20amp device through a 5amp circuit).

The Holley stuff is nice, but expensive for what you get. What's nice about the Holley is it's somewhat idiot proof, like an Iphone, whereas the MS stuff requires more of a seasoned user.

The MS3 stuff is outright fantastic, but still more complex than the Holley stuff.

The LS stuff is quite limited, unfortunately. But it's cheap and plentiful.


-- Joe
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Old 09-19-2017, 05:19 PM   #346
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

I like the MS3 platform.. and Holley is certainly overpriced for the individual parts. I guess it's worth it if you just want to buy it and plug it in without building harnesses and tweaking. In my old age, time is worth more than money so I guess I fit their demographic.


The main reason I like Holley is the Dominator having integrated transmission control, built-in WB02 controllers and the option for drive by wire (for a $180 harness upgrade). I wouldn't totally rule out the MS3 because I have not yet sat down to add up a full cost sheet for either system.
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Old 09-19-2017, 06:13 PM   #347
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Quote:
Originally Posted by DIGGLER
from the vids i watched, it didnt seem an obvious trans slippage issue, imo. not discounting the trans altogether, but im leaning away from it at this point. and blowing through the converter would be more of a going straight to 5k+ and staying there.
Dig, what would essentially underline everything is if we were given a full time slip. I mean we can calculate the power he is making with the data provided, and the numbers won't lie, but looking at where he is throughout the 60', 330', 660 and 1320', you can find the culprit pretty easy that way. He may be feeling the byproduct of a higher RPM band by opening up the intake tubing to 3" from 2 1/2", larger throttle body and better intake manifold, whereas he was used to more torque down low with the TPI system and 2 1/2" tubing. He needs to understand that opening up the intake tubing to 3" with a bigger throttle body and intake not only raised his RPM band, but his boost pressure will drop while making the same power. So... at 15-psi on the old setup, he is more than likely seeing those same power numbers at only 10-psi with the new setup, and jumping up to 18-psi is now astronomical. The trans simply can't handle the power. His trans is definitely on the way out, so if I could make a suggestion I would throw in a 4L60 or 4L80 before getting an LS engine, either way it is the better choice in terms of transmissions. Being relegated to a detent cable and weak transmission, you can't really expect it to hold past 500 horsepower, and his boost numbers with the new setup are up there, so is his spark advance. I mean at 20 plus degrees and 18 pounds of boost pressure, I'm surprised nothing broke yet...

- Rob
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Old 09-19-2017, 10:18 PM   #348
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

I forget. What brand module and coil is in it?

The timing error is "exponential" because of a fixed timing latency and the time per degree is a 1/x function.

The GM latency table can be approximated at a 300 usec fixed latency.
Since the usec per degree is this function: time_per_degree = (1/(RPM/60)) / 360
It is clear that as RPM increases, the time per degree decreases as 1/x.

Here is a table so you can ignore the math and see how the timing error due to the 300 usec delay increases due to the RPM increasing.

Code:
rpm	rev/sec	msec/rev	usec/degree	timing error due to 300usec latency
1000.00	16.67	60.00	166.67	1.83
2000.00	33.33	30.00	83.33	3.66
3000.00	50.00	20.00	55.56	5.49
4000.00	66.67	15.00	41.67	7.32
5000.00	83.33	12.00	33.33	9.15
6000.00	100.00	10.00	27.78	10.98
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Old 09-20-2017, 06:03 AM   #349
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Quote:
Originally Posted by ZZ3Astro View Post
I like the MS3 platform.. and Holley is certainly overpriced for the individual parts. I guess it's worth it if you just want to buy it and plug it in without building harnesses and tweaking. In my old age, time is worth more than money so I guess I fit their demographic.


The main reason I like Holley is the Dominator having integrated transmission control, built-in WB02 controllers and the option for drive by wire (for a $180 harness upgrade). I wouldn't totally rule out the MS3 because I have not yet sat down to add up a full cost sheet for either system.
If you want e-trans control, go with the Holley. With MS you need a second device (megashift) which communicates via CAN. Some people don't dig having two boxes, so I get that.

The only thing I don't like about the Holley is it's weird fuel maps. Quite different from anything else, but as a system it works flawlessly.

-- Joe
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Old 09-20-2017, 06:11 AM   #350
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Re: Turbo Iroc - Round Four (Edit: Staying Gen1, new PT7675, heads, intake)

Quote:
Originally Posted by junkcltr View Post
I forget. What brand module and coil is in it?

The timing error is "exponential" because of a fixed timing latency and the time per degree is a 1/x function.

The GM latency table can be approximated at a 300 usec fixed latency.
Since the usec per degree is this function: time_per_degree = (1/(RPM/60)) / 360
It is clear that as RPM increases, the time per degree decreases as 1/x.

Here is a table so you can ignore the math and see how the timing error due to the 300 usec delay increases due to the RPM increasing.

Code:
rpm	rev/sec	msec/rev	usec/degree	timing error due to 300usec latency
1000.00	16.67	60.00	166.67	1.83
2000.00	33.33	30.00	83.33	3.66
3000.00	50.00	20.00	55.56	5.49
4000.00	66.67	15.00	41.67	7.32
5000.00	83.33	12.00	33.33	9.15
6000.00	100.00	10.00	27.78	10.98
Just looked at my tune, and the spark hardware latency isn't a table it's a constant. I have mine set to 38 usec. I don't know what math is being performed behind the scenes, but I thought it was a table in MS too..


-- Joe
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