Bigger Turbo

[benl1981]

I have a 450hp high flow with stock BOV.

IT hasn't been tuned, still running standard turbo tune.

I find sometimes when giving a little throttle around 3000rpm accelerating, then backing slowly off the throttle I get a jerk from the car.

If you look at the Map tracer it jumps up and down..

SK reckons that you can add more timing and fuel to get rid of this, however I have added more timing and it seems to be a little better.

I spoke to another tuner and he reckons it's normal with the bigger turbos and can't really be tuned out.

Wondering if anone else gets this.

It's not real bad, it depends on your driving style. You could drive and not notice it but if you do a lot of bringing it up onto boost and esing off slowly you can definately feel it.

Anyone with 2530, or slide or GCG had this problem?

Thanks

[STATUS]

it would be the injector fuel cut tripping between on and off. Bit of a PFC niggle.... if you are real careful you can sit on this ON/OFF point on decell and it will burble and pop away.

Edited May 3, 2007 by URAS

[benl1981]

Thanks URAS, but I don't think it is as you can also get the problem when not backing off I think. I'll try it again and watch the injector duty when it is happening, but I still don't think it would jerk like this..

[MANWHORE]

it would be the injector fuel cut tripping between on and off. Bit of a PFC niggle.... if you are real careful you can sit on this ON/OFF point on decell and it will burble and pop away.

I can sit on a point when decelerating on the stock ecu, and do the burble popping. is that only powerfc related?

[paulr33]

everything can be tuned out its just a matter of how long it takes

it would be interesting to see datalogit logs of it

[STATUS]

I can sit on a point when decelerating on the stock ecu, and do the burble popping. is that only powerfc related?

no but it gets a little bit more pronounced on the FC.

[STATUS]

Thanks URAS, but I don't think it is as you can also get the problem when not backing off I think. I'll try it again and watch the injector duty when it is happening, but I still don't think it would jerk like this..

it is probally a simple timing step then, as paul said it should be a simple tune issue.

[NYTSKY]

it would be the injector fuel cut tripping between on and off. Bit of a PFC niggle.... if you are real careful you can sit on this ON/OFF point on decell and it will burble and pop away.

HAHAHA i do that all the time.The other week i went on a long cruz down the coast with a few lines.Going down Bulli pass in third with my foot only very slightly on the pedal,the thing was burbling and popping like a race car lol

Love it

[Bass Junky]

If somebody has performed the "Grub Screw in the Blow Off Valve" modification, you will get this little jerk.

I got it when I put the grub screw in mine.

Remove Grub screw and the jerk goes away.

[bradsm87]

everything can be tuned out its just a matter of how long it takes

it would be interesting to see datalogit logs of it

I disagree. Some things are still physically limited. Like turbo flutter happens because air travels backwards out of the turbo and out of the AFM. There is no way for an ecu to know which way the air is travelling through the AFM.