Strange. My car is giving me a stumble at low rpm transitions to WOT.
Example- if I'm driving at 2000 rpm's in 3rd gear, and I punch it, it stumbles for a half second, then catches and goes smoothly again.
I can exagerate it by putting it in 4rth and punching it at 1500 rpms (very low) It bucks for a second. It does it every time I floor it at low rpms.


It's exactly analagous to a malfunctioning accelerator pump on a carb.
I've checked the a/f ratio, and it's steady.... but maybejust the o2 sensor doesn't react quickly enough to detect a half second change.

Any ideas?? It's just annoying for it to be coughing like that when you are doing things like backing out of a drivway or doing three point turns or something.


I'm thinking it MAY be because of the intercooler and piping.... when the throttle is opened suddenly, the AFM, being in front of the turbo and such, is delayed at sensing the sudden vacuum behind it.... just a thought. I'll be putting in on the upper IC pipe tomorrow anyways, 8" away from the right at the TB.

 

Hm, nobody taking a stab?

 

my rx-7 does the same thing, maybe an engine torque brace would fix it

 

Are you running a modded tb?

 

dude..... My GTU had a VERY slight bit of stumble at low rpms if you stand on it suddenly... with what you got going on, i can imagine its exaggerated!!! I think you are right in your theory... as you juice it, the injectors automatically dump some fuel in.. your A/F meter isn't going to catch up right away, because there is no immediate change in pressure.... the turbo won't increase the boost until the exhaust gas pressure increases..... with all that piping.... an A/F meter is like hampster trying to run on a flywheel,,, always trying to catch up!!! A possibility could be that the wastegate isn't function correctly.. what are you using as a boost controller???.... Also.. that DYI wideband (tech edge i assume) might not be reading correctly a couple of people have already nuked their motors cause they were not reading correctly... they also dont seem to react quick enough, you might be missing a rich or lean spike when you tromp on it....

Also.. check your ignition... the spark might be off just a tad and can't handle the sudden rich condition...

Something is definately "catching up" with the throttle.. you just need to find out what.

My advice.... don't tromp on it at low RPMS.... its a Rotary DUDE!!!!!! however, I must applaud you for turboing an N/A.. NICE!!!

Finally... you really need to ditch that MAF sensor and switch to a MAP sensor, much better in a turbo application.... but i know its hard to pony up the 1500 or so to switch over to a Haltech!!!!

 

I had that problem...Found a small vac leak. Once I fixed the leak, the stumble went away.

God, that stumble was annoying.

Jarrett