Any guesses on rwhp and torque gains?

mto502 · Apr 1, 2004

Mods are in my sig. I'm presently running with the stock FPR. My A/F is a fairly consistent 13.5 across the board so she's a bit lean. The plugs are all white as well.

A friend mentioned to me that he gained 10 rwhp by increasing his fuel pressure by only 1 psi to 40 psi over the stock 39 psi. I'm going to start with this before going to a custom chip.

Anyone want to take a stab at whether, if any, gains I'll see with an adjustable FPR?

Where I dyno my car, the owner of the shops assistant figures I'll see at least 10 rwhp increase.

Zero Signal · Apr 1, 2004

It's hard to tell is an adjustable FPR will do anything since the computer will compensate. But I'd rather have the computer trying to lean it out than struggle to richen it, so it may be worth it to help out your adaptive fuel trim. DO you have some kind of chip? I assume you measured the 13.5 on a wideband? Without a chip, I think that's close to the computer's target for WOT, I'm at work so I can't double check that.

mto502 · Apr 1, 2004

Zero Signal said:
It's hard to tell is an adjustable FPR will do anything since the computer will compensate. But I'd rather have the computer trying to lean it out than struggle to richen it, so it may be worth it to help out your adaptive fuel trim. DO you have some kind of chip? I assume you measured the 13.5 on a wideband? Without a chip, I think that's close to the computer's target for WOT, I'm at work so I can't double check that.

Yes it was done on a wideband.
I don't have a chip; I'm just using the stock computer right now. I was going to get a Diablo custom chip but even the Diablo dealer recommended I try the AFPR prior to going for the chip.

GTJake · Apr 1, 2004

You may gain somehting initially, but the computer is just going to put it back where it wants it. The only way to really change it is with a chip/twEECer/PMS.

Jake

mto502 · Apr 1, 2004

I just got off the phone with my local Diablo dealer and he gave me the head programers cell number in Florida. I suppose I'll call him and ask him this same question about using the AFPR with out a chip and the stock EEC's effect on that.
I'll also ask him if the chip takes care of timing retard during shifting, and throttle reponse improvement.
What else does a custom chip help with ?

mto502 · Apr 1, 2004

I spoke to the programmer in Florida and he said the stock computer won't reset everything exactly like it was. He mentioned something about the closed loop at lower rpms making the car running rich but at WOT I'd still be getting the added hp from the extra fuel pressure however I'd be using a lot more fuel and the car would be running rich when not at WOT, thus the AFPR and a chip would be the best. He said to dyno test the chip and if any adjustments were necessary with the AFPR then they could recalibrate that with adjustments to the program and the fuel pressure could be readjusted back to where it was and then the chip would take care of it. He also mentioned the timing retard for shifting could be taken care of. He didn't think the computer retards the timing for shifting other than maybe backing things down on the torque side of things for the tranny. It all sounded very confusing and I hope I understood fully what he said..lol

S/CBlack95GT · Apr 1, 2004

GTJake said:
You may gain somehting initially, but the computer is just going to put it back where it wants it. The only way to really change it is with a chip/twEECer/PMS.

Jake

Not true. The computer does not control the AF/R via the O2 readings under WOT. If you bump up the fuel pressure your AF/R will become richer under WOT. At part throttle your AF/R will always be what the stock computer setting is b/c the computer reverts back to the O2 readings. If you go too lean or too rich then under part throttle the computer will throw the check engine light to tell you this. Typically N/A stangs like to have around a 12.8-13.4 AF/R. I really doubt you will pick up 10rwhp just from richening your engine up, unless it likes to run really rich, which some do. Its always fun to run them on the dyno to find out though.

S/CBlack95GT · Apr 1, 2004

mto502 said:
I spoke to the programmer in Florida, [he said] I'd be using a lot more fuel and the car would be running rich when not at WOT, thus the AFPR and a chip would be the best.

A chip and AFPR would be best true, but your car will not run rich under part throttle. That is what the O2s are for. Under part throttle,they will reset the mix to a preprogrammed setting as long as the pressure isnt too low or too high. For example, if you set your pressure at 60psi you may be running a 10:1 AF/R under wot, but then the computer will try to reset that back to a 13.5-14.0:1 under part thottle. Since you have so much fuel pressure dialed in the computer will not be able to cut the injector pulse enough to achieve that 13.5-14.0:1 AF/R under part throttle. Therefore, it will throw a check engine light telling you it has reached the lean adaptive limit.

mto502 · Apr 1, 2004

Thankyou for clearing that up S/C Black95GT.
So with the use of an AFPR I will be able to adjust the pressure while I have the chip in the car, and if the car likes anything than stock fuel pressure I can tell the chip company to reprogram the chip? Or would I just leave the fuel pressure trhe way it likes it best with the chip?

I don't want to set off any check engine lights. Diablo figures I will gain at least 15 rwhp with the use of their chip. How much horsepower do you think I'd gain with just the AFPR, and do you feel it's worth getting the chip or should I just use the AFPR and see what happens on the dyno ?

Thanks again, Rick

S/CBlack95GT · Apr 1, 2004

Personally I dont think chips are worth it, b/c you may want to install nitrous, a turbo, or an S/C later. Chips really don't help that much to gain peak power, but they do help gain power throughout the range. With a chip you must get the fuel pressure setting somewhat close then have a chip burnt to fine tune the fuel and timing curves. I would not just call and order a chip though. If you get one you need to go somewhere that offers the burning right there at the dyno. That way they can try setting after setting in order to get the car dialed in.

mto502 · Apr 1, 2004

S/CBlack95GT said:
Personally I dont think chips are worth it, b/c you may want to install nitrous, a turbo, or an S/C later. Chips really don't help that much to gain peak power, but they do help gain power throughout the range. With a chip you must get the fuel pressure setting somewhat close then have a chip burnt to fine tune the fuel and timing curves. I would not just call and order a chip though. If you get one you need to go somewhere that offers the burning right there at the dyno. That way they can try setting after setting in order to get the car dialed in.

I agree however with Diablo, if I don't like what I see I don't have to buy it because it's guaranteed. They claim to have the proper tune for all the modifications on my car. They say they've done so many programs that if there are any adjustments needed they will be very small if any at all. It's not through the mail but rather a local dealer, and the dyno place is just down the road so I can drive right back and get my money back if I'm not happy. The head programmer is in Florida but he just sents the program up to the dealer and he flashes the chip. It's pretty much all done in seconds.

S/CBlack95GT · Apr 1, 2004

mto502 said:
I agree however with Diablo, if I don't like what I see I don't have to buy it because it's guaranteed. They claim to have the proper tune for all the modifications on my car. They say they've done so many programs that if there are any adjustments needed they will be very small if any at all. It's not through the mail but rather a local dealer, and the dyno place is just down the road so I can drive right back and get my money back if I'm not happy. The head programmer is in Florida but he just sents the program up to the dealer and he flashes the chip. It's pretty much all done in seconds.

Good deal. That is how Anderson Ford Motorsport does it near me, so that will work just fine.

Zero Signal · Apr 1, 2004

Not true. The computer does not control the AF/R via the O2 readings under WOT

Yeah the computer doesn't continuously update the fuel trim at WOT, but it does use the last values it saw before going into WOT.

Correction: I don't know that it's the last KAMRF seen, but I'm almost 100% positive that there is a long term trim applied to OL which is somehow based on the short term KAMRF's.

mto502 · Apr 2, 2004

Zero Signal said:
Yeah the computer doesn't continuously update the fuel trim at WOT, but it does use the last values it saw before going into WOT.

Correction: I don't know that it's the last KAMRF seen, but I'm almost 100% positive that there is a long term trim applied to OL which is somehow based on the short term KAMRF's.

This is the question I'd really like to clear up. Does the computer actually readjust the AF during WOT or will that tune remain the same. I've had some people say the computer will readjust itself for the added fuel pressure during WOT over time, and others have said that once it's in WOT the computer can do nothing about the added fuel pressure and the AF will always remain the same. I wish I knew for sure.

Zero Signal · Apr 2, 2004

It's hard to find solid information on that really. If you go to the tweecer forums and do some searches you can find some pretty good threads on the topic.

Here is another explanation I took from the tweecer forums. . .

Daren Woodall wrote:

This is my understanding. It is an accumulation of things read on this topic combined with personal observation.

There are two components to adaptive strategy, short-term and long-term fuel correction (trim). KAMFR is the representation of short-term fuel correction. Short-term trims are only occuring during closed-loop. Now, these short-term numbers are applied to the long-term fuel trim, probably averaged for given load/RPM intersections. It is the long-term fuel trims that are applied during some open-loop modes. From what I've read, WOT does not have any adaptive correct applied to it. Also, there is no representation of long-term fuel correction displayed in CalCon.

That sums up what I know,

Daren

Then Joshua Teixeira's (Shonut's) reply:

One other interpretation is that the short term fuel trim is the ratio of 14.64 to Lambse at any given time when in closed loop. I.e. if Lambse is 13.31, your short term fuel trim is 14.64/13.31 = 1.1, i.e. the EEC has added 10% more fuel to acheive stoich (I may have this backwards, i.e. Lambse/14.64 to give lower numbers for more fuel added). This trim is only applied to the fueling at hand for the purposes of approaching stoich, i.e. short term, in both derivation and use. The EEC remembers these corrections (or their averages) at given conditions and uses them, over time, to update the long term fuel trim table (KAMFR). The KAMFR table is recorded and applied according to the axes of the KAMFR table (RPM and load?), and is kept for a long time (hence long term fuel trims). This process of updating the KAMFR table is otherwise known as adaptive fuel control, and turning off adaptive will force KAMFR to stay at 1.000, and you have effectively disabled the development of long term fuel trims. If adaptive is enabled, then once KAMFR is properly updated, the short term fuel trims will be very close to 1, i.e. Lambse will be close to 14.64 in closed loop, while KAMFR will be something other than 1, with different values based on the position in the table based on load and RPM as developed by the EEC's observation results of closed loop. In other words, closed loop is used to calculate short term fuel trims required to acheive stoich, and adaptive fuel control takes these short term fuel trims, and by also observing the RPM and load they were obtained at (with averaging), develops the long term fuel trims, otherwise known as KAMFR.

I still haven't decided which to believe. I like the latter, since everything is well defined However, it presumes that KAMFR is applied TO the Lambse value to determine the pulsewidth (as opposed to being used to determine Lambse). People have also observed that if adaptive is disabled (and KAMFR is fixed at 1), that their WOT tunes stay more stable, i.e. don't get rich or lean over time, suggesting that 'long term fuel trims' have been disabled.

If, perhaps, Lambse was expressed as 1 instead of 14.64, then it would be more intuitive - you would see two numbers that vary up or down around the value of 1.000 - i.e. Lambse would run up and down during closed loop - and it would be easier to call that Lambse value near 1.000 a ' short term fuel trim', while KAMFR would vary around 1.000, according to the axes of the KAMFR table, and be called 'long term fuel trim'.

Comments? I've never heard anyone definitively state what the correct method is. What does the Ford documentation say?

And even through more searching, I have yet to find a real answer as well. I like the last explanation better. I have a hard time believing that the computer has no adaptive fuel trim strategy for OL and WOT. ALthough it doesn't change it in OL, it still does something. I found a few more articles that pretty much described that strategy as well whic leads me to believe it to be the better theory.

mto502 · Apr 2, 2004

That straightened me out........... just like a pretzel

The programmer from Diablo mentioned that the computer will make small changes to WOT over time but it won't change it completely back to the AFR it was prior to adding fuel pressure with an AFPR. He said that once the AFR is set at WOT it will pretty much always remain the same.

Geeze... this is a tricky one. Thanks for the research you did Zero Signal.

Rick

Any guesses on rwhp and torque gains?

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