Stumbling off idle.

[gtmdriver]

I've just taken my car out (air cooled VW Beetle 1600) for it's first drive after fitting the MS2 v3 controlled port injection with a single throttle body.

I began by using the VE and AFR tables generated by the tools in TunerStudio and I have to say that I'm very impressed with those and especially with VE Analyse Live.

When I set off the car was understandably running a little rough but it was very interesting to feel the car improving dramatically as I drove.

I realise I will ultimately need to get the car properly set up on a rolling road but at the moment I am over the moon with these early results.

The only area which is still iffy is the region just coming off a closed throttle. The area which would be covered by the progression circuit in a carburettor. The engine tries to die, coughs and occasionally backfires when pulling away from a closed throttle. It feels like it's running weak there and, because this is a transient state rather than a steady state, VE Analyse Live hasn't been able to pick it up yet.

I'm quite happy to adjust it manually but I need to check which table and which area of the table I should be adjusting.

First of all, since I am using 'Incorporate AFR' should I make the changes on the AFR or the VE table?

Secondly is the outlined area on this (sample) table the area I should be looking at or am I looking in the wrong place?

[risk]

You need to tune Accel Enrich (acceleration wizard), not the main fuel table. This feature is just like the accelerator pump in a carburetor as you described. Depending on how you tune it, it will add fuel based on the TPS change or MAP change, and give and extra "squirt" of fuel when you mash the gas pedal.

Open the acceleration wizard dialog box with the key on, engine off.. you should be able to push the gas pedal and see the result on the graph. You can tune it off TPSdot (speed of throttle pedal being pushed)-right graph, or MAP change (manifold vacuum)-left graph, or a mixture of the two. I have had better luck just going off the throttle pedal.

You will also use this to tune the "tip in", ie: when you are cruising and mash the gas pedal to accelerate.

One problem I had tuning this, is that my car rides pretty rough.. my foot bouncing up and down bumping the pedal a bit caused issues. Took some time but I was able to tune that out.

[gtmdriver]

The acceleration enrichment is in use using TPS.dot and seems to be fine over almost all of the range. It's just that one specific circumstance when setting off from pure idle and opening the throttle gently that the engine stutters.

[ps2375]

You may need to adjust the timing in those areas for when you leave from a stop. My guess is that you'll actually be above and to the left of the area you highlighted, as the rpm will droop and the kPa will increase as you open throttle.

[Max Welton]

Maybe I missed it ... Have you checked the logs to see if your spiking lean? Also possible you have to much acell enrichment and are pushing it rich.

Check your logs.

Max

[gtmdriver]

That obviously needs to be next on my "to do list.