SD2 and 160lb injector Off Idle Stumble

[TT/Ameasap]

I keep getting a really bad off idle stumble with the new 160's. I have fuel enrichment at 255 and that seems to work better, but I cant shake this problem by myself. I tried VE table corrections and injector pw to try and get this gone. Any suggestions? fp is 32 line on.

 

[Eric Stage I]

Pay close attention to where the VE bubble is going when you blip the throttle. It might need changes there.

Also, experiment with fuel pressure to see which way is better.

If you want, log the stumble, and attach it so we can look.

 

[TT/Ameasap]

I tried lean and rich in the area where it happens. IDK.
I will get a log of it tomorrow and post it.

 

[TurboBob]

what kind of throttle body? experiment with the injector offset also, as it will affect tip-in fuel.

Bob

 

[TT/Ameasap]

JJ 62mm
I noticed this when I changed my heads to the TA heads. My 120's did it too, but I didnt have but a few miles on them before I seen DC at 85% and decided to go with the 160's.
This log below shows that I tried leaning out the spot where it happens 1100-1600 or around there somwhere. I added fuel to the lean spike to no avail. I played with this on the old tune and never got it out either. All other areas seem to work fine tho.

 

[TurboBuRick]

The timing table can play a role as well. Timing should curve up on tip in.

I've also corrected this problem on other cars by slightly moving the cam sensor.

 

[BEATAV8]

Take a look at your wideband data. A massive lean spike or a piggy rich droop, either one will stumble and you can tell the difference between the two. If both, then it'll really be a mess. The lean spike you can tune with FP, cam sensor timing, injector offset like the old pros here have already said. The rich droop you can tune with the AE setting. Also make sure your TPS data looks good and works good, if the TPS is flakey better get a fresh one. A good throttle body also makes all the difference in the world.

in the end, if it looks like this consistently you will be in good shape: (this is with 160's)
if this lean spike went up to 16, you'd probably feel it. If it drooped to 10, you'd feel that too.

 

[TT/Ameasap]

The timing table can play a role as well. Timing should curve up on tip in.

I've also corrected this problem on other cars by slightly moving the cam sensor.

I'll check the timing curve ....Which way did you move the cam sensor?

 

[TT/Ameasap]

Steve, that is exactly where it is happening. cell 6 seems to be very rich in the beginning of the cell and very lean on the last half before going to cell 7.
I played with this when I had the 120's and still couldnt get it out. I wanted a real smooth tranition as soon as I hit the accelerator.

 

[czimpel]

I corrected a tip in stumble with fuel pressure. Not SD2, but it fixed the problem. In my case I had to lower it.

 

[TT/Ameasap]

After reviewing some of my logs, Im almost positive that it is due to the rich spike. I had been pulling fuel from 90kpa in the 1000-1600 rpm range where the bubble sweeps across the cells quickly, but I think I need more taken out to lessen that dip.

 

[TT/Ameasap]

Ok. Im pretty sure I have it. I had to pull a lot of fuel from those cells I mentioned above. From 80 to 60 and now I have a clean and crisp throttle. When I engage the Tbrake I have no more hesitation.

thanks for the help guys.

 

[czimpel]

Good to hear.

 

[007gn]

Ok. Im pretty sure I have it. I had to pull a lot of fuel from those cells I mentioned above. From 80 to 60 and now I have a clean and crisp throttle. When I engage the Tbrake I have no more hesitation.

thanks for the help guys.

Overall do you like your sd set up better a 6.1 set up? & does the car make more power? I have a 5.7 tt chip currently and I was thinking of switching to the sd2 set up.

 

[TT/Ameasap]

I have been running SD for around 3 yrs now and I wouldn't trade it for anything. It is a mini Xfi so to speak, and the tuning aspect of this chip is awesome. Initially, I liked the fact of loosing the MAF sensor because finding a good OEM used one was too hard anymore these days. I believe this in itself increases airflow. I also knew that I wouldnt be using the same injectors the whole time and the SD2 allows for you to simply type what inj. you want into the software. Getting used to the VE table is not too bad. I definatly think more power is unleashed using an SD2 vs an off the shelf chip because of the VE table. I can custom tune my car to the custom parts I have. Having a gas tune one minute and then E85 the next is very nice. No more worrying about E85 stations and having to swap your chip back over and retune. No chip will match that, and for the price, you just cant beat it.