put in 550s, now im bogging down at WOT

[Sephroth57]

i installed a big 16g turbo and a 255 walbro HP pump about a week ago and its been running very good. i just put in 550 injectors today and now when im WOT and hitting boost im bogging down and the car is barely accelerating. im guessing now im getting too much fuel? i dont have a air/fuel gauge or EGT so im not sure how to tune this. im getting a datalogger in about 2 weeks but thats a long time off to be driving like this. anyone have any recomendations for SAFC tuning? right now i have it at base 0% fuel add (it was around +4% when i had 450s) and its still bogging, should i try to lean it out a little go like -3% fuel or even a little more? need some help from an experienced tuner


and yes i know all cars are different.. but with my given situation i really have no way to monitor so im looking for someone with experience

 

[Silver98GSX]

I would start out by putting all your setting at high throttle on the S-AFC from 1000rpms - 3000rpms put the setting to -10. From 4000rpms & up to about -8 on the high throttle. low throttle start off at -5 at every rpm. See how that does and work with it. If it starts to bog, pull some more fuel out. If you feel like its pulling time and getting slower, add fuel where needed. Hope this helps.

Johnathon

 

[Sephroth57]

thx, ill try that on my lunch break today =)

 

[FearceDSM]

I have the same dilemna. But I have not installed the injectors yet. I figured that 550's flow 22% more fuel than 450's. What I am trying to figure out is if this number applies overall througout the whole injector duty. If so, then wouldn't setting the afc (-22%) across the board for the low and hi throttle settings be equivalent to 450's with the afc set to (0%) for the low and hi settings. Wouldn't that bring it all back down to stock fuel delivery levels? I have heard that the AFC has trouble controlling injectors larger than 660's, I would assume that because 660's are 46% more fuel than 450's, the afc would not be able to compensate because the AFC can only take away 50% so the headroom for tuning is not that high. At 46% you would only be able to lean out 4% more. Someone please shed some light on this for us. Thanks.

 

[kpt4321]

Fearce DSM, you are right on.

 

[Sephroth57]

hmm yeah that is good logic fearce, ill try doing like -15% im a little scared i might lean it out too much. and ill see how it goes from there

 

[FearceDSM]

Sephroth57
It says you have a Walbro 255. Fuel delivery wise, I have the same setup as you. I did rewire my pump and I have the high pressure pump. Do you have a aftermarket AFPR? If not, you will have a hard time tuning your afc because the pump itself will make you run rich and the 550 injectors will make it even worse. You fuel pressure will not be linear from idle to WOT. I know this because I just went through the same problems with this setup.

 

[Sephroth57]

well i just went on lunch and tuned my AFC down to -10% across the board and it made a huge difference, feels much better and doesnt bog down anymore. Im sure it could be optimized a little more but as long as stuff isnt gonna break it should be ok till i get my logger in about 2 weeks.

fearce, yeah i dont have a AFPR i ordered the B&M FPR and fuel pressure gauge that goes with it from DSMparts.com a couple days ago, ill probably wait to put that in at the same time as my logger.

 

[FearceDSM]

Sephroth57
B&M Command Flo will not work. You need one that will let you lower or raise the fuel pressure. The B&M will only let you raise pressure and it uses the bottom half of the stock diaphram. That means you are still trying to regulate fuel pressure with the stock diaphram which is useless because that is what is being overrun in the first place. I just got one from fullthrottlespeed.com It was a direct bolt on to the 2g fuel rail and it even had a port for a fuel pressure gauge. It cost me around $150, which is more than you spent on the B&M unit, but it makes a world of difference for tuning and dialing in your base fuel pressure.It made a world of a difference for tuning as well. PM me. I know someone that might be getting rid of his and it is the same AFPR that I am using now.

 

[hostile]

Really you should be able to tune around a walbro 255 in a 2g.

I wouldnt worry about it for now...

Also -18% across the board is the corrected fuel map for 550's.

 

[FearceDSM]

Since he was looking to change the AFPR, I just figured I could save him the time and money by suggesting something that he can expand with. If he had no plans to change it, I would still suggest it. No sense in spending money on the part twice if he could get it done in one shot since he is buying an aftermarket FPR already.

 

[Sephroth57]

hmm i didnt know it couldnt lower the pressure also, its kinda too late as i already ordered the parts but with the AFC i can just tune it down from there right?

 

[FearceDSM]

You cannot turn down base fuel pressure or tune fuel pressure at all with the afc. I was just down the same road as you. I have the same fuel delivery set up as you and I have spent many hours researching and it was the same conclusion everytime. If you want to tune your afc as accurately as you can, you have to get the fuel pressure under control.

 

[Sephroth57]

so whats the point of having a command flo?

 

[FearceDSM]

IMHO Command Flo is really for stock fuel pumps. Its for people that want to get a little more out of there stock FP's. The stock FPR is designed to regulate the pressure out of a stock FP. An aftermarket pump outflows a stock pump. In essence, the stock FPR was not designed to regulate a pump with hi flow capacity. Like i said before the B&M uses part of the stock FPR. I would see if you could return the part. Many people that have gone your route end up selling the B&M at a loss and buying something that has the capabilities to raise nad lower. Add the difference of the loss and the new FPR, you end up spending more than if you just get the right AFPR now. Keep the gauge because it will bolt onto the AFPR.
Do a search and you will find plenty of info that supports my advice. My terminology may be off, but the AFPR advice is what I got from reading and firsthand experience. Tuning is way more accurate.

 

[lowridin2g]

while wer eon the subject of safc's, im wondering what i should set my safc to. i have it all zeroed out right now. i tried going like -2 across the boards in high throttle point and i felt as though i was pulling timing. is this right? i only have a 190 lph and 450's with stock t25 on 16 psi for right now. like i said i went back to zeroing everything out, thinking of leaving it like that for now. fp big28 ported turbo on the way, soon greddy big fmic, and 550's. but im just wondering what u guys would suggest for some sort of reasonable setting for now. thanks

 

[FearceDSM]

Originally posted by lowridin2g
while wer eon the subject of safc's, im wondering what i should set my safc to. i have it all zeroed out right now. i tried going like -2 across the boards in high throttle point and i felt as though i was pulling timing. is this right? i only have a 190 lph and 450's with stock t25 on 16 psi for right now. like i said i went back to zeroing everything out, thinking of leaving it like that for now. fp big28 ported turbo on the way, soon greddy big fmic, and 550's. but im just wondering what u guys would suggest for some sort of reasonable setting for now. thanks

It all depends if your fuel pressure is under control. I have read that some people with the 190 pump have pressure issues and some don't. Do you have a fuel pressure gauge? From what I gathered reading and personal experience, when I had the rewired Walbro 255 hp pump without an aftermarket AFPR I was running rich my base pressure was higher than stock. But when punched it there was a drop in fuel pressure below what stock pressure should be thus causing a slight lean condition up top. My car ran like crap. It is possible that your ECU is pulling timing because of that as well. I would just leave the settings at 0 for the hi throttle on the AFC until you can verify that you have consistant fuel delivery to tune with.If you feel the car runs bad at -2 then put it back to 0. You need to datalog the car if you want to tune it. Without that you are tuning blindly and you might not see disaster before it strikes. It's better to be safe than sorry with a busted ass ride. Make sure everything is consistant before tuning.

 

[lowridin2g]

I have the same dilemna. But I have not installed the injectors yet. I figured that 550's flow 22% more fuel than 450's. What I am trying to figure out is if this number applies overall througout the whole injector duty. If so, then wouldn't setting the afc (-22%) across the board for the low and hi throttle settings be equivalent to 450's with the afc set to (0%) for the low and hi settings. Wouldn't that bring it all back down to stock fuel delivery levels? I have heard that the AFC has trouble controlling injectors larger than 660's, I would assume that because 660's are 46% more fuel than 450's, the afc would not be able to compensate because the AFC can only take away 50% so the headroom for tuning is not that high. At 46% you would only be able to lean out 4% more. Someone please shed some light on this for us. Thanks.

wiseman..........i need your help, is what hes saying true? i mean is he dead on or not? someone please clear this up for me. thanks alot

 

[ITSME4G63]

Use a datalogger, it is most likely knock, i had the same problem, give some more fuel (youll need an afc for that).