For those that have used an adjustable FPR to more or less tune your afr. how much does the fuel pressure affect the a/f ratio. for example if i lower the pressure by 3psi, how much should i expect the afr to move up (leaner)?

 

most of us also use an SAFC or VAFC to tune after raising the fuel pressure .5 bar

 

yea thats what 90% of everyone uses, but I dont want a afc right now and i already have an adjustable fpr so mineswell learn about it. maybe i can lean my mixture out a lil with it.

 

if ur just tuning with AFPR then u might want to get a wide band O2 to monitior those readings...spend the extra 150 an get an afc that way u can get timing too

 

you cant do timing with afc unless its EU.

 

With an SAFC/VAFC you can lower your MAF voltage which will trick the ECU into advancing timing. This is no where near as accurate as EMU, but it can still give you something.

 

ok. but back on topic. lol.

 

get a wideband if your goin to play with the fuel pressure

 

cant i just dyno and do the same? i kno u need to see the a/f i just want a simple yes or no. can you tune with fuel pressure regulator?

 

dyno us and tell us.
What are your mods?

 

Hope this helps best I can offer, I have a s10 with a 350 and 650 holley and when I add fuel pressure at the fpr it gained a few hp in the upper rpm range, but on the other side you can go too far and start to lose power. I know the example I used is not a max and a 350 with a holley is alot simpler but hope this helps

 

you could lean it out with an fpr, but not every rpm needs fuel taken out. on my old ae, lower rpms were fine and it was the upper that needed the tuning. of course, i had a vafc2 and wideband o2 going so it was safe to pull a certain amount of fuel from different rpms. i would not just lower the fuel pressure and hope its safe. if you get on a dyno, make sure they are using a wideband and not a less accurate tail pipe sniffer to determine your a/f. even then, i think you will find not all rpms need the fuel taken out which is what will happen if you just lower the fuel pressure with an adjustable fpr. so can you do it? yes. do you necessarily want to? i would say no.

 

My mods are: Ypipe, catback 2.5, 00vi (with 4thgen lower IM), CAI, UDP (useless), walbro 190 (for nitrous), nismo afpr, and tranny stuff (auto).

I did dyno, but the dyno was before 00vi and before 190 walbro. So I dont kno how accurate it would be, the a/f ratio curve was pretty smooth and almost same ratio across the entire rpm range. was at 12.5 then dropped too about 12 at 4.5K and back up to 12.5 to redline.

 

Arrgghh ... Since when?

 

Is that a/f during spray or a motor run? I advised against blindly removing fuel when it was motor, I certainly would not pull fuel with the fpr if you are going to spray on it.

 

that was during n/a, also during spray it was same a/f pretty much. and yea i agree, im not going to spray if i lower the pressure. thats for certain.

 

The AFC is a very raw tune. What you're taking about is even more raw.


These are very important points and should be added to your mental cliff notes. Do not ignore this information.

Quoted for truth

 

ok fine. ill just put pressure back to 43 and leave it alone till i can get a tuning device. thanx all for ur input.

 

stoburn ****

 

DIAF!!! lol