what kind of numers are you running at wot on the pe vs. rpm table? i am running a 383 with 12 lbs of boost. my multiplyer right now is 2 and it is still leaning out on the tiop side. does this # sound high or low? just wondering if i am wasting my time. any info would be greatful.

 

high or low is relative to if you are subtracting or adding fuel somewhere else that throws this number off.

first, are you maintaining, losing or increasing fuel pressure under load?

 

not sure i dont have an in car fuel pressure gauge. i know unloaded (in nuetral) it maintains pressure. but it will differ under load correct?

 

it may be dropping off, and if it is dropping off hard it is affecting how much fuel is getting in the engine.. and making you crank the multiplyier over to (unsuccesfully) fix the lean condidtion.

 

i agree, is there any way to check the fuel pressure with logging software?

 

there is no fuel pressure sensor in the stock system.

you can borrow a mechanical gauge from some places and tape it to your widnshield

this is a very important gauge (most important i say) with forced induction.. i would invest in a nice in car gauge.

 

yeah i am looking for one now cause all i have is a gauge on the rail. what gauge do you recommend?

 

Whoa, something is not right. With a mulitplier of 2 you are commanding (assuming the car is tuned well) a WOT a/f of 7.4:1

Like said, I would definitely check your fuel pressure. Has your car been tuned?

 

If you are talking about the PE vs RPM table, this should be a table where you "command" the desired equilivence ratio.

For example, if you want a 12.0 airfuel ratio you take.

14.6 (stoich for gasoline) and then your commanded airfuel of 12.0 you can come up with your PE value.

14.6/12.0= 1.216

I hope this helps.

Ryan

 

This is what my PE table looks like with 75lb injectors @ 55psi, as you can see it uses a lot of fuel up top

If you are just using the stock OS and MAP sensor the PE is the only way to add fuel, commanded fuel means nothing once you peg the MAF and MAP. Crude but it works for me..

 

yeah i thought a multiplyer of 2 was high. what can cause loss of fuel pressure at wot?

 

I thought this is when you really should be running a 2 or 3 bar MAP sensor and custom OS for a SD tune? I was under the impression running the stock OS while pegging the MAF and MAP is not exactly....safe???

 

I dunno, I have over 300 passes on my car, never hurt a thing. Not to mention its one of the fastest 346 D1SC cars out there and has won quite a few bracket and heads up races - doesnt mean much on the internet though lol.

 

supercharger cars always have the same airflow during wide open at a given rpm, so it is far more safe to use this method to cheat the system than on a turbo car, where your fuel demands are independent of rpm.

that being said, if you tune with a maxed maf on a cold day, on a hot day with the same tune the car will run rich, and the opposite.

 

here's the kicker: if you're measuring air with MAF or 1bar MAP you're working against a fake ceiling. that's why all the 1bar FI people have insanly high PE values--what you can't measure with air, you gotta overdump fuel on.
while it's a valiant effort, i will never understand the reasoning behind it--if you have a FI setup, you've invested at least 10-15k in your car already, so why not buy that 2barMAP and 2barSD setup (300bux?) and just get it done right?

so here's how the math works, i'll do it with easy numbers so it's easy to see:
if a 5.7L engine flows 45lb/min of air at 90% VE (a typical NA number) then running about 13-14psi will get you in 180-190% VE (~90lb/min of air), effectively flowing twice the amount of air in the base case. but the only thing you can account for is the 45lb/min due to limitations of hardware (1barMAP) or software (MAF).
the NA case needs about 26lb/hr of fuel. the boosted case needs ~59lb/hr of fuel (extra rich for FI)
the problem is that the pcm will only 'see' about 56lb/min of airflow. then how do we deliever 59lb/hr of fuel? well, we dictate almost twice the amount of fuel to dump. since such needs are only happening during WOT, you can approximate your boost to your rpm and go by that to create nice fake PE numbers.

so if airflow is 90lb/min and you want 11:1 AFR, you will need 8.18lb/min of fuel. but you dont know that you have 90lb/min of airflow, your pcm only registers 56, which means you want to dictate 56/8.18= 6.84AFR, which in PE terms means 14.62/6.84= 2.13 EQ ridiculous, isn't it? but it works!
the problems can happen, because with everything being thrown off so much, the tiniest error gets blown out of proportion, and under high load and boost it can have a catastrophic effect. Also, you cannot quantify improvements of your setup, as you dont see any additional airflow, as it's been maxed out for a long time.

so go ahead, save your 300 dollars, and wait to granade your engine which will cost you thousands to replace. but i'm not amazed, if you can't do the math for airflow and fuelflow, forseeing financial consequences is a bit out of your reach as well.

 

Got to love the internet. You are pretty clueless for someone who acts so smart..

 

i'm not dissing your achievements, i think they're amazing, especially considering what an 'eyeball' tune that has to be. what i'm trying to understand is the stubborn resistance to doing things right, especially at such low of a cost, and with so much at risk. that's all.

 

I own HPT 2BAR for 98s (ask Keith), I have tried it and its out, on a 98 I just cant get rid of the IAT headaches with SD - a big factor whe you go from 79 to 130 dehrees IAT in 9 seconds, if I have to shut off the car on the line after a burnout I am plain screwed. I have also repinned a harness and ran the EFIlive custom OS and after nearly a month of fooling with it the car never ran any better.

I am not stupid and have invested more in various tuning solutions then most have in their entire car. But the bottom line is using the PE flat out works. You can call it hacked, cobbled, stupid whatever but it works and is very easy to touch up at the track. Plus with the MAF still active at lower rpm it drives like stock and gets excellent fuel mileage. Throttle response? 1.308 60's off idle footbraking it isnt so bad for a 3450lb car is it?

I'm not reluctant to try anything, matter of fact I'm stupid for dumping thousands of dollars trying to fix what isnt broke Here is this months pile of stuff, notice the two leaking 500.00 water pumps also lol.

 

I must say I agree here... With a 1 bar setup there are too many variables. Dont get me wrong I am guilty of doing this myself. But I am on the right track now and just looking at the 2barSDtune it makes more sense. Just something to think about...

My friend lives in the mountains, out there my car was at 4psi max. I come back home and I am at 9psi. With a 1bar tune my car is so far off because its just looking at PEvs.RPM. What you really need is adequate fuel to provide for the boost level. So what you all are saying is a 1bar is adequate but how??? In PE my car is providing enough fuel for 9psi but what if I am not getting 9 psi?

 

if you're having IAT related issues, the GTO guys have figured out that you can replace our IAT with another IAT that gives the same output, but it does react much quicker to temp changes. $15 is worth a try, i'd say, especially if your IAT issues are so pronounced.