Yet another surging/bucking question

[muncie21]

I'm running a SC C5 with stock cam. After installing SVO 42lb injectors and LS6 heads I'm getting slight surging or bucking on light throttle acceleration and decel. The surging is definately due to leaning out the AFR, which I'm seeing on my wideband.

Question is, what would cause this to happen? My impression is the injectors are reacting too fast and putting in too much, then too little fuel. I updated all my injector related tables to compensate for the change from disk to pintle injectors. Do I drop the proportional fueling table in the affected airflow modes?

[ninobrn99]

i know it hasnt been established as the thing to do, but since we have modified injectors, wouldnt we want to change the inj. PW?

[WS6FirebirdTA00]

no need to change the PW as i have never seen it do anything. yes you can lower the prop fuel tables to help the o2s react better. its more or less trial and error until you get it dialed in

[muncie21]

Thanks. Just wanted to make sure I was on the right track with fuel and it wasn't some crazy dynamic airflow setting.

[muncie21]

Here's a picture of my surging. Going to drop the proportional fueling tables by 50% tonight and see if that's at least going in the right direction.

[WS6FirebirdTA00]

actually your o2s look liike they are switching pretty good

[muncie21]

Any thoughts on the crazy AFR swings then? If I have the car at steady speed and load (no hills, valleys) the WB is right on track with the Commanded AFR.

FWIW, I didn't get these swings with the delphi/lucas 42#'ers. Of course they gave me other problems.

[WS6FirebirdTA00]

post the actual log, its hard to read that pic

[muncie21]

Yea, good point. Both of these are from today.

[torchredfrc2]

I'm seeing the same issue with the 42# SVO injectors i recently installed. I'll put up a log in a little bit.

[torchredfrc2]

Have you tried adjusting the minimum injector pulse width? It looks like I see surging when my pulse width drops below 1.9ms.

[muncie21]

I put the Delphi units back in. For me, they are much easier to tune. Poof, no more surging, idle AFRs look good. No complaints.

[torchredfrc2]

Dang, I was hoping that you got this issue resolved & I could learn from you.

[muncie21]

Dang, I was hoping that you got this issue resolved & I could learn from you.

Buy some Delphi's LOL.
Seriously, if you figure yours out, post up. I'd like to know how to fix this should it come up in the future also.

[WS6FirebirdTA00]

Have you done the basics like retune the VE?

[muncie21]

Have you done the basics like retune the VE?

I don't know the details of Torch's issues, but mine was definately fueling related. AFRs were dead-on with both type of injectors (Delphi and SVO) but the SVOs would cause the car to jerk on part throttle decel. After a couple of days trying to straighten those out, I decided to just put the Delphis back in.

BTW, I originally took the Delphis out cause I thought I had one sticking injector.

[WS6FirebirdTA00]

So the car would just jump on decel? Any certain range? Could be throttle cracker airflow is too high or the car is too rich on decel, prob need to reduce the offset table

[muncie21]

I posted some logs and pics a few post up. Basically on part throttle decel my AFRs would bounce up/down, causing the car to surge.

[WS6FirebirdTA00]

I will take a look later, but if you didnt find anything, then you have to look further, instead of thinking the fuel going back and forth is causing the surge, you have to find out what is making the fuel swing like that. What did you change in an attempt to fix it?

[WS6FirebirdTA00]

Plus, something can be making the car surge which then makes the fuel jump around.