Misses on idle S6 2.2t VEMS

[Wrath]

Hello,

After driven a firends car (same model but chiptuned and 1.8t coils)
I came to the conclusion that my car dosent idle correct.

Or the idle is fine (~850-900) but it has some engine judder, looks like its misses every 2-3s. or so. He´s engine runs much smoother, and if I raise the idle with the throttle to say 1500rpm from 850-900 it dosent miss and runs smooth, you can feel with your hand that it shakes on idle.

what can be the sympton for this?

The car is stock except exhaust and VEMS for now... don´t have any MAF

Have changed the coilpack with some used coils as it run on 4 cylinders after a enginewash half a year ago... have also two spare POS but don´t think they could cause this as it runs great on 1,35 bars boost and runs smooth on cruise speed aswell...

[prj]

Wrong dwell timing, injection angle, clogged injectors, screwed up coils, wrong ignition timing etc...

[Wrath]

Can also say that it was like this before it got tuned with vems, but then i ran bad instead... believe it was the lambda probe as it was white as snow

injectors has been cleaned and they flow the same... tried that as I thought they where the fault for high HC value but it was bad cats

Also the coilpack Ive bought was from the friend with 1.8t coils, he just changed cause he thought they where a better option when chiptuning his car... he didn´t have any problem with them but hey they have layed in a box for some month... Thought I just give you experts som more meat to the bone...

[prj]

I told you what can be wrong with it. It's up to you to check all of those things.

[Wrath]

of course, thanks mate, just rememberd som more stuff... but the POS I can rule out then...

whats the optimal ignition timing on idle for these engine PRJ,~got around 15-17 degrees on 850 rpm

[Wrath]

double post...

[prj]

You got it set up wrong then.

On idle you must have a timing reserve, which regulates idle using timing.
You should have about 9 degrees timing on 800 RPM and 12 degrees at 650, then 15 degrees at 550.

That way it'll regulate idle properly. I suggest reading "Designing and Tuning High-Performance Fuel Injection Systems" by Greg Banish, it is the perfect book if you are trying to learn mapping and doing it with a speed density ECU.

He explains everything very well.

[Wrath]

I see, yes im very green with this, have a base map you can call it mapped by a friend of mine Mattias a VEMS guru, but can´t run to him every day with stupid question... was reading about dwell time earlier before I posted this topic, just checked with a old config and the dwell charge time @ 13,2V is 1.98ms and coil charge map scale is 5 maybe the dwell time is to low and the ignition is set to high. In general you can say that I have to get the car on the Dynopack and have it tuned for real first, but as im not finnished with the turbo,injector,clutch switch yet I havent botherd. Just fiddling to make my Idle as stabile as I can.

Good advise on the book... maybe there is a Swedish copy of that otherwise I can read up on my technical english aswell... thanks Dmitri

[Wrath]

Found pop´s thread where you explain similar to what you already been doing here, did search for 20 minutes about this problem before posting my own thread... bummer... compared my timing reserve to his and they almost looks the same only thing is that Ive got 17 degrees in first 9 colums from the bottom left (3 up and 3 to the right)... that´s kinda off then...

[prj]

1.98ms is adequate for 2.0 TFSI coils.

These coils need more like 4-4.5ms tapering to 2.7 ms at 7000 rpm.

[Jamo]

If Mattias is your friend pay him to map the car!

[Wrath]

He don´t have any dyno, and map it on the road aint ideal. He just based map it and it runs really good, just a tweak with idle is left...

[Wrath]

Dmitri: I see, thought that it was to low, but can´t change that until understand how that works...

[Jamo]

The car can be mapped on the road perfectly well obviously dyno tuning is better but having Mattias map it is better than you trying to learn to map using vems on a newly built spec
Don't understand the logic even I paid for my car to be mapped until I knew more about mapping and tweaking

[Wrath]

True, just want a perfect idle, and that was hard even for Mattias, of course he could fix it but takes a lot of time and money, just wanted to test for myself, as the idle setting seems to be the easiest tuning for a newbie like me... don´t want to fiddle with anything else...