Hi Guys,

Sorry bout this, but I have to ask the same question. I just added an FPR and was planning another dyno, but need help working this out. See:

http://www.s2000online.com/forums/showthre...p?threadid=7071

I'm not sure anyone here seems to really know what the ecu is doing, or if FPR is better at rich (mingster) or lean (luis) settings.
I know things are variable between dynos, but we are talking about two different theories of why fpr helps.


1. Too rich because ECU is changing injector pulse over time? Thus leaning out helped Luis.

2. Too Lean, as mingster found out with his runs?thus running rich (but will change over time via computer learning?)

So where does that leave someone with an FPR, and the Mugen ECU that leans things out? (see- scotts reply) A dyno won't help with fpr setting if ecu changes things over time even with sports/mapping. Am I missing something here?


p.s. A very interesting trait my car has BTW is better performance with very low gas levels. Does that signify a lean or rich enviroment because of the vacum?


Thanks

[Edited by viscreal2000 on 06-04-2001 at 07:17 AM]

 

It could be the lower weight when you have less gas.

Also, from what I remember reading on the forum, the factory FPR can vary +/- 5%? If that's the case, cause be Mingster was running too lean and Luis too rich initially.

As for rich or lean... when I dyno'd my car, I also asked for the AF ratio. It was very clear that on the run where I made the most power, the car was leaner compared to the other two runs and the lowest run being the most rich. Here's my dyno chart:



-Shing

 

i'll let you know soon. got FPR installed yesterday (thanks Prolene!), and will dyno soon. the goal is the removal of the dip in power at 6250RPMs.

 

It is my understanding that adjusting the fuel pressure only makes a difference at WOT since at all other throttle openings the ECU is handling mixture with pulse duration.

My experience trying to tune with the FPR was not on a dyno but by using timing from one rpm to another in third gear at WOT. My conclusion was that it must be tuned as the temperature changes and is at best a compromise because of changes in atmospheric conditions.. and of course the safest compromise in on the rich side.

After getting a baseline timing with the stock FPR (unknown pressure) I started at the lean setting that was working for Fito, but found the car was slower so went with a richer setting. Some months later I tried it again and found a setting a bit lower gave a slightly better time.

I have concluded that staying in the bottom half of the factory range worked best for me, but until now I have not seen good results going leaner than the factory range as some as suggested.

I may fool with this again in the heat of summer, but thus far this mod has been more trouble than it was worth to me.

 

Hmmmm, thanks for the response. I guess I might not have worded that correctly. My main concern is that regardless of what pressure I set on the FPR after a dyno, am I going to lose the gained power after the ecu thinks no way? If so, whats the stable pressure I want? Well, if I set it to spec, at least it won't vary.

p.s. are you guys SURE about more pressure via regulator means rich or lean neccessarily?

Thanks.

 

i dyno'd mine two weeks ago with the neuspeed exhaust. i had the highest power setting it at 38.5psi. a little less and it dropped, a little more and it dropped. tuned in 0.5psi increments.

when i was driving across country, i noticed definate performace change by changing the fuel pressure based on ambient temp. in the east it was snowing, i richened the mixture and it felt better. in the west it was very hot, i leaned it back out and again felt better. around here the 30-50 degree daily heat cycle makes things veeeeery interesting.

 

hmmm...more fuel to the fire eh? (sorry) anyway josh thanks for the info. BTW, when you guys say lean do you mean as in less fuel in air/fuel mixture, or in the pressure before the injectors? Thanks.

P.S.
whats factory pressure again?
note-our search function sucks

 

you're safe setting pressure at 41psi if you're unsure.

 

Factory pressure is 47-54 psi with the vacuum line to the FPR disconnected and plugged. You should always adjust pressure this way because otherwise you're looking at manifold adjusted pressure, which varies with engine speed, ambient conditions, etc.

The whole fuel pressure issue is a touchy one. Viscreal, your concern that the ECU will remove the changes over time is a valid one. In tuning Prolene's car, we found that adding pressure actually created a leaner mixture, as though the ECU was adding too much pulsewidth to overcompensate for a lean mixture. Thus, if you get the FPR set properly, what you really seem to be doing is avoiding the ECU's wrath, so to speak. Mingster's testing will provide mroe data still, but until we decode the ECU and/or put in a V-AFC controller and do some precise experimenting, it's hard to tell how things really work.

UL

[Edited by ultimate lurker on 06-04-2001 at 10:44 AM]

 

thanks for you valuable (as usual) input UL