bigempty12

We just tuned 620whp on E85 last weekend using PT&E 1600cc injectors on Hondata S300. Fuel is great on the dyno, and on boost is great on the street, but off boost driveability and idle was terrible. I went out and did some street tuning, and got great drivability out of it with NA fuel at Lambda 1, and got a decent idle out of it. However, I have no fuel at what I assume is throttle tip in. Up until about 17% throttle, after that it's great. If I release the accelerator and then get into it lightly, there is hesistation and bog until greater than 17% throttle, then I get fuel readings on my wideband, and everything is fine. Also starting the car is a mother f@#$%. It just doesn't want to start until it gets fuel. On hondata s300 there is fuel trim for cranking, and throttle tip in, so my question is, is that where I need to be looking for adjustment, and will adjusting throttle tip in alter my high speed fuel settings at all. I know that if anything it would make me run a little rich, but my lambda values are right were we want it for boost, or is throttle tip in trim just going to help that 0-17% thottle posisition. Thanks

SOHC_MShue

throttle tip in deals more with fuel enrichment on a sudden stab of the throttle from almost closed to 100% open. The air will flow faster than the fuel so you will need to inject extra fuel to keep up with the rush of air. It sounds like you may just have issues with the tune in the first few partial throttle columns.

bigempty12

I was thinking that at first, so I kept adding fuel in what appeared to be the troublesome areas, and it did nothing. If I held just a touch more throttle (20%) then my lambda readings got richer and richer. This doesn't seem to be rpm related at all as it does the same thing all the way through the rpm band at low throttle position. I suspect throttle tip in because it only does it when I transisition from 0% throttle to very minimal throttle (17%) Basically what is needed to maintain a speed. Although maybe I am misunderstanding you, if what you are saying is that throttle tip in (essenstially) trims for the sudden on and off of the accerator, then maybe throttle tip in is my issue. If you're saying that it's trim is effective even if I press the accelerator to 100% and hold it there all the way through redline, then maybe I just need to tune more, or deal with it. It just seemed that no matter what I did with the fuel, it didn't affect the 17% throttle position or less at all. Just made above 17% throttle richer regardless of rpm. Thanks again

SOHC_MShue

yea i dont believe throttle tip in is your issue in this situation. Maybe you just need an aftermarket injector drive to pulse the injectors faster at those low load conditions. It will at least help out with idle.

bigbadboy

yea its not throttle tip. i have precision 1600's in mine i don't have quite the issues you do. the only thing i had a problem with was setting the idle so that it was smooth at 800 but it just took a lot of my time. my drivability is good too. check and make sure that you scaled the TPS reading. that might also cause it run funny. at part throttle. also where do you have the map sensor reading signal from??

bigempty12

I scaled the TPS and it's fine, I have my map signal coming from the stock map sensor vacuume line on the throttle body. Is that an ok place to run a GM 3bar, or should I try pulling from the intake manifold? My tuner mentioned an injector driver, so that is what I am planning on getting, but at the time we weren't able to get an idle out of it, after street tuning for a while I was able to get decent idle and decent drivability, so I thought maybe I could tune this issue out, but maybe not.

bigbadboy

you should be able to tune it out. how does you map look around the idle cells?? your values should be pretty high in those areas compared to the rest of your map. do you have a vaccume manifold?? if so try running your map sensor off of there. i was running my map sensor directly off the intake manifold and it wasn't sensitive enought to pick up the difference in vaccume change when cruising so it cause the AF to do some crazy things and run like crap.