I was thinking about the TPI'S. Was there a noticable difference? Did it change gas milaege alot I drive my car 45 miles everyday and it is getting expensive, but that will not stop me just curious. What is the stock pressure and what do you bump it up to? My car seemed to stop pulling at the track at around 4500. I have 3 inch catback and SLP 1 3/4 headers so i know I have that covered, just figured I was not getting enough fuel.
Thanks, Gary

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1990 Formula 350

 

Adjusting the fuel pressure will probably give you worse gas mileage, since I assume you want to raise it. I believe stock pressure is 40-42psi, to bump it up you just twist the top of the FPR counter-clockwise to raise the diaphram(I don't have one, Im just assuming this), this is why putting pennies and dimes in your stock FPR raises the pressure(raises the diaphram). I think a quarter is 57psi or something :P

TPI isn't much good over 4500, stock. It tends to die off there.

 

https://www.thirdgen.org/messgboard/...ML/011430.html

Here you go bud read this. Glen knows what he is talking about. This should help you just fine. Also my setting is there as well if that means anything.

 

The 4,500 rpm limitation is more a function of the intake and cam.

SD is especially notorious for being overly rich BTW. I initially "played" with fuel pressure and discovered I need LESS not MORE fuel for the proper mixture. That is why I got into eprom burning, because I do believe in running higher fuel pressure (around 46 psi), but I had to reduce the amount of fuel in the VE Tables to run 46 psi and get max performance.

When done TOGETHER, it will help and your fuel economy will actually increase slightly due to the better atomization.

 

DON'T get TPIS, the vacuum port breaks off real easy,,not worth the $
i think Holley makes the one you can adjust by hand, someone back me up here.

 

I will back you up Ron that is what I have is the Holley and I am really glad that I bought this one. You can adj it with your fingers so it makes it really really easy to adj. Def. worth the money.

 

Crane makes a decent one too.

 

crane sucks the vaccum port broke off on mine used super glue epoxy to glue it back.accel's looks like it is a good design dont know of anyone thhat has one.f i was to do it all over again i would not bother with one and take out the scraeder valve and use a plug by blocking off the return line the fuel pressure increase 10psi if you want less i would think to not bottom out the plug and let a fraction of the amount back to the tank!!!

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87 trans am 350,L98 aluminum heads,LT4 hot cam,slp runners,slp 1 5/8 headers,3in.y-pipe,edelbrock base,hi flo cat,air foil,afpr,as&m ported plenum,t-5 tranny w/centerforce clutch and a 3.27 9bolt(11.9in. brakes),ed wright's fastchip,relocated iat sensor,tb bypass,accel supercoil,hollowed maf,slp 3in. catback,a/c delete.
oh!no!i think my maf is going!!!!!!!!!!!!

14.10@97mph w/2.01 60'

slp catback is finally on!!!
fastchip prom is in.OH!MAN!
FLOWMASTER S.U.C.K.S

 

Thanks guys, I will check out the Holley.
Glenn what do you mean by the VE tables. So you are saying I do not need one that I should get a chip instead. Or should I put a coin in the stock one instead?
Thanks, Gary


[This message has been edited by 90FormulaL98 (edited July 18, 2001).]

[This message has been edited by 90FormulaL98 (edited July 18, 2001).]

 

BTTT

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1990 Formula 350

 

The amount of fuel delivered to an engine is dependent on the size of your injectors, the amount of fuel pressure and eprom. You want an injector size that will be large enough to not exceed to 80% duty cycle (open more than 80% of the time) yet small enough to not cause the pulse width to be less than 1 ms @ idle.

Your fuel pressure should (desireably) be somewhere between 40 - 50 psi. Too low and the gas will not properly atomize, too high and you will prematurely burn out your fuel pump. I like 46-48 psi.

Lastly, the eprom has to deliver the proper "pulse width" to the injector to ensure the mixture is 14.7:1 @ closed loop and between 12.5-13.0:1 @ WOT (the actual mixture depends on what your engine wants).

But to get the proper VE tables means having the eprom made for your specific motor. If the above are not in harmony you will either be too rich (and kill performance) or too lean (risk detonation).

On SD cars, the fuel is controlled by the Volumetric Efficiency tables. These tables have "factors" based on a specific RPM and Load (the MAP reference in Kilopascals). The goal is to get BLM/INT values at 128/128 throughout the RPM/Load range.

At part throttle, the O2 sensor is the final umpire that will adjust these pulse width for any inaccuracies in the VE tables but at WOT you run based on the table values. If the tables are incorrect, then the ecm will not deliver the proper amount of fuel.

Most eprom writers concentrate on WOT and do little (or nothing) with part throttle, letting the O2 sensor take car of everything. At WOT (or Power Enrichment, which is the proper term inside the eprom) the eprom adds more fuel to VE amount. Eprom writers work with the PE adjustment @ 100 KPA (your MAP reading @ sea level), but as you increase in elevation, you will not get 100 kpa @ WOT. If you live in a mountainous area, or above sea level; your WOT will use maybe 90 kpa...if 90 kpa is not adjusted, then the mixture will be incorrect.

Also, the eprom does not need 100% TPS to go into PE. It can occur as low as 50-70% (depending on your RPM and the value selected in your eprom...that is why I do not recommend screwing with the TPS to adjust the voltage to go into PE sooner...the eprom is the proper place to adjust this).

But, if you go into PE @ 50%, you will start adding fuel possibly at 60-70 kpa. Thus if your VE tables are not correct, you will have an improper mixture.

That is why I am not a fan of eproms that have not been tuned to your engine...and not just on a dyno. You should adjust the eprom THROUGHOUT the RPM/Load range of the VE tables to give you 128/128, AND then adjust for WOT (or PE), because you go into PE at other Loads than just 100 KPA.

If you want to learn more about eprom buring, go to the DIY PROM Board and start reading the link on the top of the page called "Traxion's Prom Burning Introduction". Burning an eprom is a lot easier than you think. And, in all actualality, SD is easier to tune than MAF. SD is "time consuming" to get all the VE values correctly, but it gives a more precise reading (when tuned right) throughout the RPM/Load range. That is one of the main reasons guys convert from MAF to SD.

 

The Crane piece is pretty good.

What the hell are you guys doing to break off the vaucuum port?

BTW, I first bought an Accell AFPR, total piece of crap. I sent it back to Summit and got the Crane.