Drac0nic

Double. Delete.

Drac0nic

Don't under estimate the ability of turbulence to cause flow restriction. If you're measuring at the flange that's where you're likely to see the most pressure. I hijacked this from an eng-tips page.

"
General Flow Restrictor Model Equation:

Q = K(r)*A(r)*deltaP^n

where:
Q = flow
K(r) = flow coefficient
A(r) = flow area
deltaP = pressure differential
n = exponent (0.5 for turbulent and 1 for laminar)
"

If you notice, you basically get a square root as your deltaP for laminar versus turbluent. That's a huge difference. You're dealing with a double whammy here too because you're reducing A(r) as well as increasing turbulence. I suspect that if you cut this out you're going to see a bare minimum of 30% decrease in pressure maybe 40%.

ZZ3Astro

Wow that is interesting to see. It makes another interesting thing come to light as well. In each of the exhuast runners there is a boss for a.i.r. tubes. This boss is basically a short piece of threaded thick-wall tubing inserted into each runner basically facing the cyl head exhaust port. They go straigh in where the runner turns up to go into the log. Kind of like this: -(- The point being they protrude INTO the runner just as much as they stick out for the fitting. I was looking at that yesterday wondering how that might affect flow. I think now I will take the time to cut those down flush as well.

Manifold is at my friend's shop. They are going to machine the flange that bolts to the head. It has a slight twist from one end to the other and seems worst on cylinder #2. He is also going to try machining the turbo flange out as close to T4 as the design will allow. I'll then follow up with a grinder to port match to the new turbo. I also found two cracks that I need to weld up.

My wastegate is smaller than I realized as well. Tempted to go ahead and cut the wastegate flange off the manifold, put a larger opening v-band there and mount the wastegate on a short extension tube forward of its current location. This is required to clear the compressor if I want a larger wastegate.

DIGGLER

iTrader: (1)

updates?

ZZ3Astro

Still waiting on them. Might be done tomorrow. Would be nice to have something to do for the weekend!

ZZ3Astro

And.... still waiting

ZZ3Astro

:-(

sailtexas186548

iTrader: (2)

time to grab your stuff and hit a new machine shop!

ZZ3Astro

It's the price of freeee lol. Thinking about it though, although this shop is the best around here by a long shot. They're just super busy with some navy contract work.

sailtexas186548

iTrader: (2)

you know, after reading all of the work you having done to that manifold you could probably get some thick wall weld els, one thick header flange, and a t4 flange and just make a new one that's exactly what you want, the time would be about the same I imagine but it will cost you $120+ probably

project89

iTrader: (1)

i have the right weld els if u wanna go that route, flange set is 35 bucks from summit, t4 flange off ebay is about 12 and id can shoot ya a price on the weld els if u want would now but not sure if u would want 4 or all 8 that i have as leftovers

ZZ3Astro

Finally got the manifold back. I'm pretty disappointed in the fact that the cylinder head flange was not "welded up and machined down" which was the reason given for the length of time taken. It wasn't even milled. I'm not sure what they used but the lines run lengthwise. I can see where material was removed, but it still is not flush when placed on the head. I was able to pull it flush with bolts on cyl #8 but was unable to verify for cylinders 2,4 and 6. My old head had a buggered thread for some reason so my only option was to go ahead and bolt it back on the car to see what happens. Cyl #2 leaks audibly. Ok a minor exhaust leak, screw it, let's at least go drive it and watch the exhaust pressure..

Precision said that opening up the flange from T3 to T4 they would expect the boost to drop as the back pressure is relieved, along with a power increase. Seeing the same 21-22 psi it made on my very last test drive last month. AFR is 11.0. The one time I really stretched it out I went into overboost protection on the Megasquirt. Of course! It's only good for 1.5 bars so 22 psi is the limit with the internal MAP sensor. When I did this first drive, I was alone so couldn't watch the gauge real good, but it looked a bit lower (still over a 2:1 ratio at least though).

After dinner tonight, I turned the boost down to 13.5 psi and took it for a spin with my wife watching the gauge. Seeing 35-36 psi at 13.5 psi of boost. That's 2.6:1 and insane. That is measured right in the center of the T4 flange. Previous ratio was also 2.6:1 -> 55 psi at 21 psi boost!!! So effectively, as I expected, no change at all.

Putting the Ebay turbo back on tomorrow tonight for comparison. Either way, this PT is going back for some changes. I expect to see a big reduction in back pressure. Last runs with the ebay T70 only made 16 psi, but the car also ran 7.71 with that turbo compared to the PT at 7.92 - albeit with fueling issues (which were present with the old turbo as well so..)

I'm at the point where you start seriously considering selling and moving on to something you can enjoy playing with. I expected various issues but this has really run its course and I'm pretty much over it all. Cut and run. Very close to it.

Orr89RocZ

iTrader: (20)

Well quoted my previous post...didnt think the flange would make serious changes and it looks like thats correct.

I refer to the other 2 comments. Change manifold design or turbine wheel perhaps with a larger exhaust pipe. Run 3.5" for a little ways if you can to see if that helps.

Not what you want to do i'm sure but it could reduce the pressure.

At this point it seems it should be making power but perhaps backpressure is keeping it from producing such power. Too much pumping loss.

Maybe a reverse pattern cam will help? I forget whats in it now.

Turbo is not an issue really, local guy just made over 720whp thru a single master power T70 p trim on a 4.6L 4v mustang motor...I was shocked. I have 2 of these turbos thought they would only be good for 600whp. I think I still have too large of turbos. Their shop used precision 6262's on twins for 1000whp thru th400 in a mach I 4.6 motor. But that 720whp car they say would not have made those numbers with the previous turbo kit that was on the car, the manifold design and piping layout was hurting power production.

89RS_82Z

iTrader: (2)

who did you machine work??

I kenw the guy who ran John-John's in Santa Rosa Beach, used to deliver to him when I drove trucks out to that area ....... seen some of his work and it looked good, dont know how much he charged or what not

ZZ3Astro

Crazy numbers! I always hear about insanely small turbos making power like that. And also about stock engines with a lot of boost doing insane numbers. Well all I can say is the pressure ratio sucks on mine.. that narrows it down to:

1> compressor side has some kind of crazy restriction or major leak, causing turbine side to do too much work to get the boost where it needs to be by the time it reaches the intake... However this is pretty well ruled out as there is minimal change when referencing the wastegate at the intake vs on the snail.

2> downpipe restriction. Not possible though, as removing all of the exhaust except the downpipe from turbo to just in front of the cat results in less than 1 psi increase in boost. I can pressure tap the downpipe to verify the backpressure here but it's pretty much ruled out.

3> the turbine itself. This will be mostly verified tomorrow night (except if it rains all night as forecast) when I put the old turbo back on for a test run.

Cam specs are 224/224 114 deg and .538" in/.531" ex

DIGGLER

iTrader: (1)

back in the day my car had an issue where one of the turbos would seize up when the engine was running. turbo wouldnt even spin until 2000 rpms or so. with the car off the turbo would spin fine by hand.

ZZ3Astro

New test results:

Installed the old Ebay turbo. Interesting side note: the ebay turbo does NOT have a pressure tap for the wastegate, so the wastegate line comes from the intake. In THEORY, this should result in higher boost as measured at the MAP sensor than when the wastegate is referenced directly from the turbo as with the PT. Assuming an expected pressure drop thru the IC and tubing of course. Instead though, now it makes 1 psi LESS boost. ??

Pressure ratio is about the same. 31 psi exhaust for 11.5 actual, although the peak was 12.5 and I wasn't able to watch that during testing of the PT turbo. Figuring on the peak figure as I did when measuring the PT, the ratio is 2.5:1. Based on the actual it is 2.7:1 so we're in the same boat with either turbo.

So now I have to ask if this could possibly be a symptom of the wastegate and/or return line design. I do have a small wastegate. My local turbo friend says having too small of a wastegate is the issue. It's unable to let out excess pressure. In one way I can understand what he's saying, but in another it just doesn't seem plausible. The way I see it, if I can adjust the boost down to 10, 12, 13 psi then how can it be too small? Not to mention the HUGE manifold leaks I had during previous testing. Or am I missing the bigger picture here?

Next test - plumb a pressure fitting into the downpipe and confirm no excessive pressure there. In the absence of excessive pressure there, WTF would you do next?

Drac0nic

The excessive back pressure isn't going to be because of the wastegate. It will let the pressure build until it sees the allowed boost on the other side. If you were overboosting then yes I would think a small wastegate issue.

I will be interested to see your down pipe results. Could be something odd with the system if you're running down pipe only. The only way to know 100% for sure is to get measurements and eliminate variables. It seems like you are really running out of them tbh.

By the way, on the PT unit did you get the 66 or 76mm turbine? I am hoping you have the 76mm turbine.

Orr89RocZ

iTrader: (20)

The PT is a 66 turbine. I'd go with the larger option and see what that does for your boost back pressure but I would think the manifold design is one cause of excessive back pressure. Turbine will help reduce it but its not the root cause.

As noted, the P trim sized wheels have supported more power without any issues so they can produce power even tho they seem small for a single turbo application. No idea what the back pressure levels were on the stangs dyno'd at this local pa shop but it obviously wasnt too high to cause reduction in power.

sailtexas186548

iTrader: (2)

a bigger wastegate is NOT a solution to excessive pre-turbo exhaust back pressure, I forget the exact reasoning but it wont work - there are some big write ups about it floating around online somewhere.

can you post up some better pics of your hotside? I looked through this thread and there aren't any great pics of it that really show the design - specifically the merge from the drivers side. Considering people have made twice the power you are making on a single 3" downpipe that runs all the way to the back bumper so I doubt it's a post turbo issue, and since you have pretty much eliminated the cold side and turbo as issues it's probably some weird issue with that cast manifold

ZZ3Astro

The manifold can't really be the problem because the difference in pressure measured at the #7 cylinder was within 1 psi of that on the opposite side right at the turbo flange. Here is a pic of the manifold.. this week's pressure testing was done on the front port right on the center of the T4 flange. Both ports are plugged in this old pic:



And I agree 100% about the exhaust. My friend's turbo tpi in his 89 corvette put down well over 500 hp and 600 ft/lb through a stockish C4 exhaust.. single 3" all the way back to the split. In my case we're talking about a car that has never put down over 350 rwhp. It's not like I'm to the point of having to really worry about a 3" straight through exhaust causing issues yet! But I'm going to pressure check it just to be able to answer to that suggestion.

I'm pretty much done with the idea of building a whole new turbo system. I'd be willing to build a new header to solve the sealing issues but I'm not about to invest weeks of work and hundreds of dollars on headers "hoping" it will solve this problem. If the pressure has made it to the inlet of the turbine then the turbo itself is the plug. Now it could be something about the turbo, or something affecting the turbo. BUt the trick is to figure out which and do so cheaply, as I'm done spending money on this pos project.

Thanks for all input though because this needs to get figured out. I'm about two problems away from putting the stock engine back in and just selling everything.

ZZ3Astro

On the question of the turbo.. I had to go 6766 because of mounting limitations. The 67 compressor is the absolute max. It rubs the head insulation. The 66 turbine is what Precision came up with for my application. If I built a new header than I might as well go to a 72 or 76mm but the whole idea was to keep the current config. I was assured the 67 would do what I was asking for, with the understanding that future upgrades in the output would require a larger turbo. I requested to make ~625 crank hp.

ZZ3Astro

Test results are in. With the car making right around 12 psi and a peak of 12.8, no measurable back pressure immediately behind the turbo in the downpipe. I was using a 100 psi gauge so it is possible there is 1 or 2 psi but I saw zero movement of the needle and I absolutely thrashed on the car like I haven't in forever.

Orr89RocZ

iTrader: (20)

Reason i was considering the manifold as a problem since its a straight log with all the ports entering at 90 deg angles instead of a more gradual transition like a 45 going in direction of the flow. I think this creates turbulence in the header and thus builds up pressure. Pressure will be uniform in the system. All the gas is going to the same place, so once it backs up, the entire system is choked out.

DIGGLER

iTrader: (1)

your manifold looks similar to one of my twin manifolds. but you are routing twice the amount of exhaust through the flange area.

ZZ3Astro

Orr, if the manifold itself were the restriction causing the high pressure, and not the turbo itself, the pressure would be much lower at the turbo because it's on the opposite side of the theoretical restriction. I agree the angles of this manifold are not great for performance but we're not talking about a 700+ hp build. We're not even at 450 hp yet and it's completely choked.

Diggler, that is true but a set of those manifolds supports 1100 hp according to the Banks site. I'm only trying to make half that much power and in fact not even making 40% of that much power and have this crazy 2.6:1 pressure ratio.

I talked with Pete at Precision Turbo today and he is baffled as well. He requested pics of my setup so I should have his input soon. They don't have an undivided 66mm turbine housing with a higher a/r than mine.. I do see they have a divided one with 1.0, 1.15 and 1.32. Other than that, they have a 6768 which is a 68mm turbine available in a .96. And they have a 7075 but the 70mm compressor is a 3" outlet which will likely cause some clearance issues. That turbine is 75mm and available in .96. That is a turbo that might possibly fit but it may not. I can barely get to the bolts with the 67mm housing. The larger turbine wouldn't be much of an issue though.

Street Lethal

iTrader: (16)

Steve, can you put up a video of you holding the video camera facing the turbo's compressor wheel at idle, and hold the camera in that position while someone revs the engine...

zz17iroc

iTrader: (4)

Hey DIGGER, I have the same ones on the shelf. How are they working for you?

Orr89RocZ

iTrader: (20)

Well it may but I'm thinking it wouldnt be. The whole system gets pressurized. You should beable to put the waste gate anywhere in the system before the turbo and get good control. It doesnt have to be right at the turbo T4 flange although that makes most sense to me. My buddy is putting his in the crossover pipe and expects good control.

I was just thinking the piping entering in a flat 90 deg way like that is causing excessive turbulence and increasing pressure due to backing up flow. I'd be curious to see what precision says after they see your setup. If thats not it and the larger turbine wont help, then I'm at a loss.

ZZ3Astro

I can make a new video of the old turbo but I'm not putting the PT back on for now. I do have a video of the Precision from the first start that shows this pretty well:

http://www.youtube.com/watch?feature...k1G2lnI#t=289s

Keep in mind this was with more serious manifold leaks which you can hear in the background.

Street Lethal

iTrader: (16)

Thanks for the video. Regarding that turbo header, do you know anyone that can modify it for you? The first thing I would do, if you plan on keeping it that is, is open the area where the crossover reaches the header to increase the volume all the way until underneath the turbo flange. It is an essentially easy process to weld. Like this...;

Street Lethal

iTrader: (16)

I'm watching the video. Just a couple of questions, how is the oil supply to the turbo, is your pressure good? Any pressure (resistance) from the oil return line? How is your coolant temps at your boost range, is it increasing? What was your final torque for your cylinder heads? Where are your EGT's...?

ZZ3Astro

It has excellent oil supply for sure. The return line fitting worked its way loose a while back and it looked like the gulf oil spill round 2 in just a couple of minutes of driving. Coolant temps are now very stable after I found a bad fan relay and upgraded to better fans. Runs cold except for extended abuse, where temps will climb a bit (stall converter is the main source of that heat though). Cylinder head bolts are ARP, torqued to spec provided in the box using the ARP lube under the bolt heads and washers. Seems like the torque spec was 10 over oem but I'd have to find the data sheet to confirm. No idea on EGT.

Believe me, I've considered exactly that mod to the manifold, but it is already nearly impossible to access the rear bolt for cyl #2. I had considered running a separate smaller tube across the gray area to leave an opening for the socket, but the waste gate return runs through that area. Not many options short of a complete rede$ign.

Street Lethal

iTrader: (16)

The reason why I asked you about your cylinder head torque specs is because I had a similar problem with my old T76. The cylinder heads kept lifting on me, and although the boost pressure increased on the gauge, most of the boost pressure went right out of the engine before even reaching the turbo, which would give the same symptoms, no back pressure, and essentially no power. Either some type of resistance is keeping the turbo from spinning during a load (heat binding, oil return buildup, etc.), or not enough exhaust gases are reaching the turbine (lifting a head, no power, and no backpressure). You would know if you had too much backpressure, believe me, as engine pinging and a glowing header would be an understatement...

ZZ3Astro

Update... or should I say lack thereof. I'm getting rather pissed at Precision Turbo right now. Never heard back from Pete at Precision. No email no phone call. Twice I've called and once left my name and number upon the answering person's request. If that's the level of courtesy they extend to someone who just paid $1000+ for something they could have gotten from Ebay for $250 (sans the name), well I'll just stick with Ebay in the future.

sailtexas186548

iTrader: (2)

what cam are you running?

ZZ3Astro

It's a comp cams hydraulic roller (custom grind). Specs off the cam card:

224/224 @ .050"
114 separation
.538"/.531" lift

Installed it straight up but beginning to wonder if there could be an issue with their grind. After-all, they did send me a non step-nose cam when I specified factory roller. No I did not degree it.

I found a post from another third genner on another forum who had an even higher pre-turbo exhaust pressure ratio than I do. He still put down 490 rwhp and then 530 rwhp with a cut-out on his 3" downpipe.. and he did it at 12 psi! I'd be completely done with my setup if I saw 490, so obviously the 3" dp is sufficient for my goals.

Here are the timing figures:

@ .050"

Intake open 2- BTDC close 46 ABDC
Exhaust open 46 BBDC close 2- ATDC

(assumes 114 deg int centerline)

sailtexas186548

iTrader: (2)

so your installed a cam that wasn't exactly what you ordered instead of sending it back? I'm not sure how possible it would be but could you have a very unfriendly cam for a turbo setup and thats causing all of your problems? I'm grasping at straws here but your problem isn't the obvious things, so maybe thinking outside the box now is your best option

Street Lethal

iTrader: (16)

Steve, I just watched most of your video's, and before I even comment on a few things, I have to say that the way you elaborated for everyone during the build was very enjoyable. You were quite thorough with everything, and I enjoyed watching them. I watched them, then watched them so more, then again some more. First of all, in regards to your coolant overheating problem, have you checked for a collapsing lower radiator hose? If so, did you go back and re-torque the cometic head gaskets after getting some heat into them? You still may be lifting a head and heating up the coolant. In terms of the backpressure issue, I'm almost convinced there is a flaw somewhere in that precision turbo. With your fuel drop under a heavy load, it is obviously a voltage issue. Is your alternator up to the task in handling the demand under heavy loads...?

Orr89RocZ

iTrader: (20)

I believe the fuel pressure drop problem was a bad line of walbro pumps and it would have issues when at hot running temps. Correct me if I'm wrong.

Street Lethal

iTrader: (16)

Looking through the videos I couldn't find anything that indicated a bad pump, but then again he has so many videos it is hard to keep track. Everytime something was fixed, it went bad again, and I didn't find anything finalized. So just to make things clear because I am basing this on the video's and not this thread, is the only problem needing to be addressed now the backpressure issue...?

Street Lethal

iTrader: (16)

Still seems like there is a fuel pressure problem. Watch the most recent video, at 11:25 just when he mentions Precision Turbo telling him boost pressure should go down. Watch the gauge, at part throttle, fuel pressure is in the low 20's, even dipping in the high teens, and at full throttle it's not even averaging in the 30's...

ZZ3Astro

Hi guys... to review the problems I had, everything has been corrected as follows:

1> Over-heating was a combination of things. The aluminum heads transfer more of the combustion heat into the coolant. This uncovered a big problem with my cooling system, which I first addressed with LS1 fans (with no resolution). Next a new radiator and of course the usual (thermostat changes, searching for collapsing lower hose, etc). Next I went to the Intrepid fans which helped but still lacked. Both fans worked upon command. During static testing I noticed the left fan wasn't loud and I discovered a cracked relay housing supplying that fan power. Opened the casing and it was all rusted and corroded. New relay, no more cooling issues.

2> Fuel pressure is a non issue now. The real problem is the digital gauge's sensor only works properly in absence of the injector pulses. As soon as you start it up, the numbers drop 10-20 psi from actual. There was an actual drop at full boost, which was resolved with the Aeromotive Steal 340. All results confirmed by using a mechanical gauge, which I regret not just going to in the first place... but I was trying to keep the install extremely stealthy and keep a single gauge (the PLX). So, sadly, much of the fuel system troubleshooting work was in vain and un-needed. I'm still trying to figure out what I should hook that pos sensor up to now that I spent $150 for it.

3> The non step nose was the only issue on the cam. The card described it right, they just sold me a retrofit hyd roller cam instead of an oem hyd roller. Wasn't happy when I went through so much trouble to describe my block and setup. But after waiting for weeks to get it from Comp in the first place, and with a busy show schedule I wanted to be in, I just sourced the parts I needed to make it work.
-----

Finally got in touch with Pete. He asked me if there is any chance of it breaking up because of the plug gaps, etc. During previous testing I did experience breaking up at high boost (no at 12 or 14 though). Also found it is impossible to hear any breaking up with my exhaust on... so tonight i'm going to run downpipe only and do some more testing of that. Might as well put the 67 back on too.

ZZ3Astro

And I recently gapped them to .025" but he is suggesting .018-0.20". Pain the the butt and I can't see the need at 14 psi but might as well do it when I can.

Orr89RocZ

iTrader: (20)

Seems awfullly tight for just 15-18 psi with good ignition system. I run .028-.030 in my car, and i'll be gapping to .025 shortly to be sure it stays lit at 6800 rpm

ZZ3Astro

Well I have to give it to Pete... it IS still breaking up! Now I wonder why. I did 'skimp' on the coil a bit because I wanted to keep a stock location so I used an MSD street fire replacement coil with oem plugs. So tonight I went out and borrowed an MSD Blaster 3 coil but I'm somewhat doubtful this will resolve it. Hopefully will though.

Kept the gaps at .025", don't want to run tighter or I think mileage will suffer. Running 8mm wires, 6AL.. msd box is wired direct to battery... maybe something to do with the MS dwell settings? Or will this Blaster fix things?

ZZ3Astro

Blaster 3 = no difference.

Back to square ZERO

junkcltr

iTrader: (1)

I think it is your ECM causing the break up. Your ignition system sounds decent if the MSD is not junk.

If you couple any noise into that MS-II you can false trigger and/or miss pulses. What type of input pickup ckt did you install? Some are a lot better than others. How is the MSD wired with the ECM?

Your plug gaps should be fine. No exotic plugs right?

ECM friendly wires? None close to the ECM pickup wires?

Drac0nic

I suspect if that were the case it would show up in the data logs. My MS-II would have 30,000 RPM spots in the logs when it had ignition noise. Turned out to be a bad HEI module.

ED:something I didn't mention was to get a timing light and be sure that the system is "unlocking" properly and timing is changing with increased RPM. Besides that, what did the old plugs look like? What valve springs are you running? I've heard that high back pressure can cause float. It makes sense since you're effectively "pushing" on the back of the valve head.

Orr89RocZ

iTrader: (20)

What comp lobes are those and what valve springs are you using? How high you turning?