luke4907

iTrader: (5)

HI, I just swapped out my stock runners and plenum for a set of SLP runners and plenum (which I did some mild smoothing up on, opened the plenum walls up) and am now running into a wall above 5000+ RPM. I also upped the fuel pressure regulator a few turns anticipating that the engine would need more fuel to match the extra air. I never could run above 5000 RPM before, but when I used to go that high with stock runners, it would slowly lose power approaching 5k rpm. I was using a 89 corvette chip (ARAP bin?) to run in my car to use with the old runners etc. and it's still setup that way.

Now, it's like hitting a brick wall. RPMs still go up slowly, no backfire or sputtering. I have a feeling that my cam/heads are just don't flow enough air to utilize the higher rpm capability of the runners. Does this sound right to you all? Aside from that, how many RPM is the stock ignition good for? I plan on doing some datalogging to see what the computer is seeing, and maybe putting the fuel pressure back to stock. I'll let you know my results when I get the chance to work on it some more. Any quick ideas would be greatly appreciated. Thanks!

1989GTATransAm

iTrader: (3)

I misread your post. Thought you did more to your SLP runners. Anyways the stock ignition system if in good shape should be fine. That is what I'm running on my combination up to 6000rpm.

Datalogging will help. Make sure your timing base is at 6 degrees with the wire disconnected. The cam on the 1989 GTA is a little more agressive than most factory cams of that era but we are not talking much.

GuitarJunki17

iTrader: (1)

Need a reason to show off your numbers GTA? lol just messing with you, very nice. What's your setup?

Back on topic:
Well, seeing as the TPIs never really made much power after 4,000, I would say that the SLP runners and your plenum (You do mean the stock plenum that you ported out right?) getting you to above 5,000rpm sounds just about right to me. As far as not knowing what your fuel pressure is, I would find out as soon as possible so you can actually fine tune that, and maybe you can squeeze some more power out. That's worse than adjusting your timing by eye from scratch and calling it a day. You can get fuel pressure guages that hook right up to the Schrader valve on your fuel line.

_Clark

b's90cam

there might be a slight difference between your runners allen and a set of cleaned up slp's.

b's90cam

just a slight one though

Red Devil

Dollars to doghnuts your 5K probably isn't really 5K. The stocktach sucks blue donkey *****. That said, how is the condition of the ignition system? I've seen some fall on their face after 5500.

luke4907

iTrader: (5)

sorry I'll clarify myself. 1st, I didn't go log data tonight because of $.35 wings and $5 pitchers tonight at a local bar. so I'll get it tomorrow,

aside from that: I basically ported the plenum walls between the two runners, so there's 2 holes on each side of the plenum. Nothing incredibly drastic, but i tried to port at an angle to get ehe best "velocity stack" effect that I could.

having said this, I took the included gaskets, matched them to the plenum, then matched the runners to the gaskets to try to keep aerodynemic drag down. The bottom looked pretty clean and I have heard of horror stories of people siamesing the runners and base too far, so I didn't do anything there.

So guitarjunk, we are talking about a stock plenum that I ported out the middle portion between the individual ports. You think the cam and heads are too small to flow above 5k rpm?

Red Devil, even if my 5k isn't really 5k on a stock tach, it is immaterial: my engine runs into a wall at 5k or so. I use a stock ignition with an MSD blaster coil, going through a cap and rotor I replaced < a year ago. Cap and rotor were in bad in condition when I replaced them, I'll pull the cap and rotor to check the connections as well, although I think I'd be having misfiring and sputtering if there was a problem with my ignition system.

Maybe I just need a tune considering the TPI computer is only capable of adjusting timing up to 4800 rpm? Thanks for all the help, I'll get more info up here ASAP.

V6camaroman

could be a number of thing stopping you from pulling past 5k, i would first check into your stock coil, or possibly your ignition timing. with the work you have done now it should quit pulling at 5. although even with all the work done to mine it quits pulling dramatically around 5 but she dont fall on her face. just try some fine tuning, and i do recomend a good aftermarket coil in there

Shagwell

...to put it simple, you have just completely run out of cam...

- stock cam only makes power to around 42-4500, so at 5k, she's done done.

GuitarJunki17

iTrader: (1)

Yes, that's what I am thinking, because they have such a low duration. You'll pull for longer with a better cam, but after that point, your heads are going to be your weak point and they wont be able to support the extra air thats wanting to get pulled in.

So yes, upgrading your ignition system will help some, but your cam is really holding you back.

D's89IROCZ

Not only that , but modified TPI's aren;t known for topping out much more than 5200 ish , even with an optimal cam and better heads. I ported my intake runners ( siamesed in 4 ") then the base was just smoothed . I couldn't get it to make power over 4900 . But the power fall off is not so harsh. This was with a ZZ4 camshaft and a stock 305 .bin in the 353.

Shagwell

exactly
- before, you weren't making as much power before 5, so the "wall" wasn't so drastic. - anyhow, since you're not making power up there, why are you worried about turning it there?

ZEEYAA

HI D'S89IROCZ, Just currious, looks like something fishy on the dyno sheet you posted. Why dosent your HP/TQ cross at 5250rpm? If the dyno is correct it should always cross at that RPM just dosent look right. Was that a chassis dyno or did you do it off the crank? Those look like some good numbers but I think his dyno was shy, you more than likley made more power than is showing. Have you made any passes in the car, if so does it work out to what it shows? Thanks.

GuitarJunki17

iTrader: (1)

Correct me if I am wrong, but I believe it's because he has HP on the Y_1 axis and TQ on the Y_2 axis (which is scaled differently)

_Clark

ZEEYAA

GUITAR, looks to me that the HP is aprox 230 / TQ is aprox 315 at 5250 RPM, I was not trying to be literal about the crossing, I was talking about HP/TQ should alway be the same at 5250 RPM, and from the graph those numbers do not intersect. So even if you follow the graph lines it still comes out to be different at the given RPM. Just currious, cause it just dosent seem to jive.

RednGold86Z

iTrader: (1)

Guitar is right. The torque at 5252 is about 243 (use the RIGHT SIDE NUMBERS!), and the hp is about 243 at 5252 (use the LEFT SIDE NUMBERS).

ZEEYAA

Sorry, BRAIN malfunction. I guess im just not used to seeing a graph in that style like that one. Thanks for your patiance.

Shagwell

why would hp/tq always intersect at the same rpm? different cam, different heads, etc... make for totally different power bands. Doesn't make any since to me....

Duts87ss

iTrader: (10)

Dynos dont measure HP, they measure torque; horsepower is calculated:

(TQ*RPM)/5252 = HP

So, at 5252 RPM, TQ=HP.

D's89IROCZ

Yeah the graph is scalled wierd . I ran it with 3 people in the car and bald tires and NO tune ( well I was useing the 305 .bin for it then ) and got a 14.4@95 with a 2.3 60 ft. Then I blew the slave cylinder.I expect when all is said and done to be around 13.8ish

Thanx

Shagwell

now everything makes more sense... "X" load takes "X" power to pull, so the load of the dyno stays constant, how fast you're able to pull that load translates to "X" amount of torque. then calculate for HP. Now I understand how a dyno works. - also explains why different dyno's show different numbers.

Thank you.

RednGold86Z

iTrader: (1)

A mustang dyno can be set up to do any form of acceleration. It can load it properly to get a constant acceleration (if desired). It can simulate a 0-60, or even a 1/4 mile run, and it can make a dyno "pull" happen in 6 seconds if desired. It changes the load with its PAU (power absorbtion unit), but it knows the load (via a reaction arm and load cell on that PAU) and speed, and thus calculates torque and power. It back calculates an engine based torque and power due to the rear gears and transmission. It actually takes torque & RPM (which is power), and then converts it back to torque by dividing out its calculated or measured RPM.

A dynojet with the big rollers and no power absorbtion unit is completely different. It's a large mass that gets accelerated. From that, calculate torque and power. BUT, the original designer of the dynojet was getting low numbers, so, he took a (yamaha, iirc) bike and compared it's reading to accepted engine dyno data, and gave it a FUDGE FACTOR so that it reads the same (against his engineers' discretion)!

luke4907

iTrader: (5)

good info guys, now I'll give you a bit of more information on my situation and thanks for everyone's help and opinions...

I realized my fuel pressure was 55+ psi. Not only that, but that 55+psi dropped to <20psi in about 1 minute. Yes, one minute. My car is difficult to start from 10min-36hours after I shut it down (except when I have opened the intake up). I have a walbro pump in the tank, and the pressure regulator is a BBK, a year or two old for both of those parts. Injectors are original. Does leaky injectors sound right?

Anyways, so I dropped the psi down to 50 and I'm gonna program my chip for 24# injectors (24=22*sqrt[50/42]) and find some replacements immediately. How do ls1/lt1 injectors compare to the multech crap our cars have? Cheap injector recommendations?

Another thing I noticed before changing the fuel pressure was that my car appeared to be running pretty happily (128int/128blm) crusing >70mph, yet idled and drove like crap (lean) in low rpm. I think I need to increase the low voltage MAF values so the computer gives more fuel and maybe pull some from the mid-high voltage MAF values. Does this sound right?

Another thing I've been trying to do is get my car to stop knocking at a medium press of the accelerator. I think I'm losing power from this as well. Does anyone know if PE is kicking in this early and causing my problem?

Finally, I changed my O2 in case all the hard-start conditions have fouled it up beyond acceptable use. Thanks for all the help guys

superGMman

Haha "engine falls on it's face 5000+ rpm" welcome to TPI

Glad you fixed the kinks out.

luke4907

iTrader: (5)

haha ya I know it shouldn't be worth much more than that in stock trim, but it just feels like it's hitting a brick wall, much harder than it used to with stock runners on there. also, your opinions on the questions I posted above would be appreciated. thanks!

ZEEYAA

Luke, isnt 55lbs way high for fuel pressure, even 50 seems a bit much for your application, I dont think much over 48 would do you any good with stock injectors. Someone should be able to post here to back me up, that just seems way high. Did you set your pressure with vaccume line removed?

superGMman

FWIW Multech injectors were supposedly the best injectors for Third Gen's, and IIRC were available in 89 only. If getting new ingectors get the Ford SVO Injectors, there are many threads about them, they work, and are easy on the wallet(as far as injectors go).

IMHO opinion you shouldn't have to be altering low voltage values to the MAF to get your car running right and the MAF is working correctly.

Possible probs:

For the knocking is the timing too advanced?

For the fuel pressure thing maybe:
BBK AFPR is messed up somehow
Fule pump gone bad somehow (maybe fuel filter?)
Injectors could be leaky. And You may be due to get the injectors replaced sometime anyways depending on how many miles your car has. just some thoughts to run through your brain, man.

luke4907

iTrader: (5)

55psi is way too high for a stock program, but I changed the psi to 50 (vac line removed) which will make my stock injectors run like 24#ers, and burned a chip for 24# injectors. I used a formula to calculate fluidic flow at different psi:
(24 # injectors)=(22 # injectors) x (square root of [50psi/42psi]).
So I could run 30psi if I wanted to, I'd just have to burn a new chip for x# injectors (=22*sqrt[30/42]). Someone please correct me if I have that formula wrong.

thx for the help & info on the injectors, I'm sure they probably were good or the best in '89, but I'm thinkin mine need replacing and a set of LS1s would probably work great if they fit. and I could probably find a low-mileage set for a fraction of the SVOs or anything else. I know the SVOs are inexpensive and probably work fine. Call me vain but I have a problem putting a Ford part on my car.

I did change my O2 and oil when I burned a new chip, so maybe that is playing a part in this too. But I drove to Tampa this weekend and made it on 1 tank of gas (something I've never done before). MPG was about 18.5, up from about 14.5 or so. It's probably due to a combination of new O2, and enabled highway fuel and spark mode in the computer.

I didn't know there was a replacement interval on injectors as part of normal maintainence. I try running Lucasoil Injector cleaner / upper cylinder lubricant every few tanks of gas to prevent buildup of junk. Other than that the injectors are probably the originals with 227k miles on them. Again, pump and regulator has been replaced (not to solve this problem, but pump died 2 years ago so it had to be replaced, and I heard of power gains by setting psi higher so I got the bbk afpr). That's what makes me suspect the injectors.

As far as the knocking is concerned, I've used a stock chip and a corvette (more advanced timing) and both knock when I get on the pedal. My base timing is set at 6* on the motor and in the burns I've done. I've pulled back some of the timing that power enrichment puts in thinking it might just be too much, but I haven't had the chance to log some more data. Or my 227k motor is slowly letting lose. I'll let you all know how it goes once I see if the computer is still pulling timing from knock. Again thanks for all the input.

superGMman

Yeah if your motor has 227k on it it definitly needs new injectors, and good idea on the LS1 ones. For the knocking, it could be that the motor is just worn out and if like you say the timing is not too advanced then that is probably the case. Could it be piston slap? Just throwing stuff out there, if you can afford to have it done I would look to see if you need the engine to be rebuilt.

Shagwell

The SVO's are bosch, just like many aftermarket injectors. - Good injectors, especially for the money, but I agree on the LS1 injectors. There's several people on this board running them. If you can find a set, go for it.
- also, 18.5 mpg/227k? probably getting wore out. My buddies 87 GTA is Stealthrammed, 497/502 cam, mild port work on heads, +.030 freshened, and he's getting 22 highway on the stock tune.

luke4907

iTrader: (5)

ahh ok that figures about the bosch part... I think part of the problem with the 18.5mpg (which is best it has been in a while) is because my torque converter doesn't lockup. so crusing at 80mph is 2600-2700 or so rpm. I'm sure there's a couple mpg locked away in that problem alone.

in any case, I think once this dies I'll be throwing an LS1/T56 in the car and calling it a day. I can't really spare the time to have the engine rebuilt and don't have the time/workspace to do it myself. it never ends, does it? haha

superGMman

It definitly never does/will end, but that's a bad and a good thing!

Rob Wade

in any case, I think once this dies I'll be throwing an LS1/T56 in the car and calling it a day. I can't really spare the time to have the engine rebuilt and don't have the time/workspace to do it myself.

So retro fitting an LS1/T56 would be faster, with no workspace?

It does sound like the injectors are leaking down when it sits. I have the bosch/ford 22's in mine. Very happy.

luke4907

iTrader: (5)

it won't necessarily be faster getting it done like that. i'll either find a place that will do it for me or the car will sit until I have the change to fix it, and in that case I'd have to buy something else to drive for work.

sach712003

If you are hitting a wall harder than before with your stock runners maybe you are experiencing valve float. Stock heads and high miles your springs could be shot

Red Devil

Multecs are pieces of fecal matter. There are some places that won't even touch them for cleaning. If the search worked, you'd be able to find a slew of info.

luke4907

iTrader: (5)

I've come across an LT1 intake, which I was considering trying the injectors on my car. LT1 injectors are 24lb at 42psi, correct? Are these just as useless as "good" TPI injectors? Thanks for your input considering I can't search here right now...

CrazyHawaiian

Halarious! Thats the first thing that came to mind when I read the title!

I agree with the rest, its probably the heads/cam. Valvesprings is another good posibility, especially with that many miles. If you distrust the engine run a compression/leakdown test and find out for sure. Even if its not acting broken, might give you some insight to the condition of the engine.

Shagwell

note: you can search, go to google, go advanced search, use TGO as the search location and type in what you're looking for - heard this from several people

luke4907

iTrader: (5)

compression test about 2 years ago yielded 150-175psi across the board. might be different now... I think I'll just ride it out for now.. I expect to have a new motor for it in the next few months.

thanks! forgot about that