performance

[JayLashua]

trying to get this thing to cook, so far I have done the following:

ATR 2.5" dual cat-back with gutted cat
87 ECM/MAF/Coil (stock chip)
K&N
Adj. wastegate actuator (Set to apx 13 PSI)
Adj. FPR set to 42# (line off/idle)
Oil cooler adapter in stock '87 radiator
external tranny cooler (pretty decent one)
160* tstat (water temp stays around 162-165)

Stock injectors/intake
'87 long block stock
open rear

dont get much tire spin actually, tps is set to 4.5v at WOT

TV is set to shift a bit higher.

when I floor it off the line it'll go to about 4400 rpm or so and shift, if im moving, it'll just slowly climb in 3rd gear and it almost feels like its being held back.

the fuel is probably a little rich, but I am not hearing any knock ( dont have a knock gauge/scan tool)

while my boost was at 13 psi, the fuel pressure was right about 52 PSI

I'm trying to find its sweet spot i guess i really need at the very least some type of O2 meter, i cant find anyone with a laptop/scan tool to borrow around here, which is rather sad considering the amount of GN owners lol

ideas/advice appreciated

 

[1984grandnat]

Sounds like you are probably getting a little knock in third gear, and the ECM is retarding the timing. Even though you don't hear the knock, it is there. May want to try setting TPS a little higher at WOT, say 4.6 or so. It should read around .42 to .43 at idle. Really, about all you can do without a scan tool, is to adjust fuel pressure to get the best performance. A knock gauge would be a real good thing to have at this point, at the very least. If your fuel press is only going from 42 to 52, that may not be enough. Your pressure should go up 1 psi per lb of boost. In other words, you should show 13 psi difference at 13 psi boost. I assume you are not judging by the stock boost gauge, right? That difference in fuel pressure COULD be causing it to knock a little in 3rd. Have you done any fuel system upgrades? At the very least, install a fuel pump hotwire kit. This will ensure that the pump is getting proper voltage. Change the fuel filter if you haven't done so lately. Tha can also limit fuel supply.

Well, these are a few ideas. Hope it helps.

 

[JayLashua]

yea i do have a caspers hotwire, stock pump i think ...

its 38 psi idle, so 52 is 14 psi increase, and i said i was prolly around 13 psi boost, which seems about right, i got a VDO gauge but its marked in increments of 5 psi so im not quite sure EXACTLY what its reading.. anyhow.. i shall try and tweak the tps a bit better and see about a fuel filter as well.

thanks

any other people care to chime in /

 

[1984grandnat]

38 psi at idle is with prolly 15 in vacuum. Add about 3 or 4 psi to get it at static pressure. That should set you about 42, which is what it is without the hose connected (static pressure). It is from the static pressure which you add 1 psi per lb of boost. For example, STATIC pressure is 42 psi, with 13 psi boost, fuel pressure should be at 55 psi.

 

[JayLashua]

that makes sense, should I just set it back to 38 static then like stock, since the FP obviously isnt where it should be up there, until i get my hands on a walbro ... . reading from the "saucy" recipe on gnttype, i got everything cept FP and headers =p

 

[1984grandnat]

You could try turning up FP a little, to help suppress detonation, and see if it performs better in 3rd (if you have an adj fuel press reg). Or simply turn your boost down a pound. You may find that it performs better with 12 psi boost and less (or no) knock than it does at 13 psi. 13 psi was a little high in my car, even at higher fuel pressures. I can't seem to run much more than 10 psi without knock, but each car is a little different. I would still say that 13 psi is still a little high on pump gas. You could also try adding some race fuel (not octane booster) and see if the performance improves at the current settings. This will tell you if you are getting knock. In my experience, the stock downpipe is the worst part of the exhaust system, and I think it is the most limiting factor. I really don't think the stock downpipe is good for anything quicker than a mid 13 or so, no matter what headers or turbo you are running, so first thing, change that downpipe!

 

[FJM568]

Okay...STOP!!! With an 87 ecm/chip and no intercooler, set your fuel pressure at about 38-39# with the vacuum line OFF...Then when you hook up the vacuum line, see what the fuel fuel pressure reads...Then add the boost that you are running and that answer is what your fuel pressure should be when you are under boost...Is that clear???

If you have it set at 42# line off, you are probably a little rich, which is why you are not getting any wheel spin and it spools slow off the line until the rpms are higher...Back the fuel pressure down to 38-39# with the line off and see how it runs...

On the TPS, anything over 4.2v at WOT is fine...

1984grandnat, if you can't get anymore than 12-13# boost on 92-3 oct pump gas, something is wrong with your car...You should be able to get 15-16# boost with virtually no knock on 93 oct pump gas, period...If not, your car isn't tuned right, or you have some kind of problem somewhere...

There is such a thing as "rich" knock...If the car is too rich, you can get some detonation...So don't assume that more fuel will cure detonation...He is having a slow spool-up problem off the line, and adding more fuel pressure will just make it worse...

Yes, the stock DP sucks, but I was able to get my car to run high 13s with stock everything, and it wasn't even running right...It didn't have the right head gaskets, I was getting some blowby, there was a lot more in that motor, but popped a head gasket, so I wasn't able to find out...Don't worry about the DP right now...

Jay, do you not have an upgraded fuel pump(Walbro) in there yet??? If it's the stock pump still in your car, you might be okay on the fuel pressure, but it might not be flowing enough volume...If you don't have a hotwire yet, that would help, BUT if I only had enough money for either a hotwire or a Walbro and not both, then get the Walbro...If you can afford both, then get both...

 

[1984grandnat]

Well, the TRUTH is...we could all sit here and make SPECULATIONS about why the car isn't doing what he wants, and I'm sure we all have OPINIONS as to what will work in his case based on our past experience...

HOWEVER, without a scantool or the proper gauges, all we can do is offer speculations. It is hard to criticize someone else's advice without hard evidence in the form of O2 numbers, knock counts, etc...

The information that he provided is pretty vague, but without knowing how much the car is knocking, I just don't feel right about recommending that he lower fuel pressure (better safe than sorry). That's the reason I recommended that he raise FP slightly, and if that doesn't help THEN try going down with it. I am just going by the description that the car feels like it is being "held back", and safely assuming that it is suffering from knock. If this assumption is true, then lowering fuel pressure could be detrimental.

...but these are all just assumptions without the proper data.

 

[1984grandnat]

BTW...here is the proper way to figure fuel pressure:

http://gnttype.org/techarea/fuelsystem/fpsys_check.html

I think this will look familiar to my post above.

You know...if you have 42 psi static pressure (vac line off), then with 13 psi boost, fuel pressure should show 55.

 

[JayLashua]

Ok heres the deal.

I purchased an AutoMeter air/fuel gauge and loweredt he FP to 38# static

in drive, i just about floor it boost reaches 9-10, or 11-12 psi if i mat it.

A/F gauge is reading a little into the rich area.

When im boosting I want to be stoich correct? so if im at 10-12 PSI boost, it should be little more to the middle than rich/lean right? perhaps i need to lean it more? I dont get any severe audible knock but who knows.. I can get a knock gauge tonight and put it in to check things.

 

[1984grandnat]

Get that knock gauge, and if there is little or no knock, by all means, lower that fuel pressure!

 

[1984grandnat]

Once you get the gauges in there, THEN you can start increasing boost levels and fuel pressure IN SMALL STEPS, to maintain a proper AF ratio (and keeping an eye on knock). Obviously, there will be a limit to how far you can go on pump gas (everyone's car is different), and also generally, the more ignition advance you run, the less boost you can make with the same octane.

My car will start to knock at just under 10 psi, but I am running a 24 degree chip (which is a little hot for a non-IC'd car on pump gas, especially in 90+ degree weather). This chip was actually set up when I had the alcohol running.

Anyway, I think you get the idea. More boost requires more fuel/octane or less timing. You just gotta find the right combination of the above through the use of the gauges. It is also interesting to note that the stock turbo is only good for about 20 psi. I ran mine all the way up to 26 psi a few times, with no increase in performance after about 20-22.

Well, I hope this information helps you in some way.

 

[BlackBuick84]

what is the stock timing for our cars?

 

[FJM568]

Originally posted by 1984grandnat


You know...if you have 42 psi static pressure (vac line off), then with 13 psi boost, fuel pressure should show 55.

Problem with that is, when you reconnect the vac line, the fuel pressure will read different, so what he will have to do is, for example, if pressure is set to 42# line off, reconnect the vac line, and read the fuel pressure, then with 13# boost added to that, get the fuel pressure that he should get when WOT at 13#...

Personally, I think you wasted your money on the air/fuel ratio gauge...You would've gotten more info by using that $50 towards buying either the proper scantool or even a knock indicator...That's just my opinion...

Now, back to your problem...With the fp lowered to 38#, does it accelerate off the line better??? Have you had any transmission work done, ie, different torque converter??? etc... Have the valve springs been changed??? That is one thing right there that would limit your boost level or make your car lie down at higher rpms...

Give us some more info on your setup...

 

[WFO]

Originally posted by FJM568


Problem with that is, when you reconnect the vac line, the fuel pressure will read different, so what he will have to do is, for example, if pressure is set to 42# line off, reconnect the vac line, and read the fuel pressure, then with 13# boost added to that, get the fuel pressure that he should get when WOT at 13#...

wrong.the static(line off) fp reading plus the boost level will be the final fuel psi.

the regulators reduce fp ~.5 psi per in/hg,and increase psi ~1 psi per lb of boost.

in the example above he should have 55# at full boost.

later,sean

 

[FJM568]

DOH!!! brain fart...sorry about that, chief!!!

But my other points are okay...

 

[6SENSE]

Was trying to stay out of it, but........
dont want anyone to get misled when it comes to facts. 1984grandnat is correct as far as the FP deal. If you have ever had a boost/vacuum gauge you could see what is really going on.

With our turbo engines, look at it as 2 parts: vac and boost pressure (they opposite each other)with a imaginary middle ground between them. Until you are boosting (i.e. idle, lower rpm driving) you are in the vac range (vac gauge would read anywhere from 8-20 usually at idle). As soon as you get on the pedal and are about to give any type of boost that vac immediately moves towards zero. You are now moving to the other side of the spectrum, boost/pressure.

In relation to that situation, when you set your FP at static (w/ the vac line off) you are setting for that middle ground (between vac and boost pressure). When you put the line back on the vac causes the regulator to pull pressure down slightly. As you reach higher vac #s the FP will go down even lower (i.e. like when you stop giving gas when getting off the highway and your rpms are still up).
On the other end of the spectrum, as soon as you get on the pedal and are about to make boost, as the vac is going down to zero THE FP IS GOING UP TO YOUR STATIC SETTING (0 vac = static FP). NOW YOUR ON THE BOOST SIDE AND FOR EACH 1lb OF BOOST YOU MAKE YOUR FP IS RAISING UP 1lb, STARTING FROM YOUR STATIC # (i.e. 42psi static + 13psi boost = 55psi is what you should see on your gauge).

P.S. With hotair cars I have had better success with FP set lower than with coldair cars. With the intercooler you need more fuel for the denser (colder) air intake.
Even with this said, it is better to be careful then sorry when guessing if your detonating and trying to decide what to do with FP. Even those who know these cars inside out use scantools, get one! You can only get so far without one, or sometimes nowhere at all. Also, should have boost, FP, oil press, and coolant temp gauges.
Need to learn as much about your car as possible, the more info you have the better. These cars are too darn picky and can get frustrating when they dont act the way you want. Check out gnttype.org tech files for info too.

 

[JayLashua]

WElp I got a knock gauge installed and made a run at 38# and got a little det. I turned the FP down 1/4 turn and that toned the knock down, havent seen any red yet, and at WOT i get about 14-15 PSI boost. Knock totally goes away at the 2-3 shift and remains gone in 3rd.. most of the knock (3-4 yellow LEDs) occurs mid-high in 2nd

intrestingly enough doing 70 down the highway cruising my knock gauge was showing like 3-4 into the yellow randomly... i do have a loose converter on the downpipe which is being fixed monday...

I'm going to have a custom chip burned by dave schmucker for my car with different timing values for tip in, part-throttle, WOT .

and I'm going to probably see about returning that A/F gauge as ive been told by other people as well its kind of a waste =/

IT LOOKS COOL THOUGH!!
;p