better VE table but has a few quirks that go full lean

[Will Powered]

So after much discussion I went back and began tuning out the VE table from practically scratch. Some of the changes that led to this were,
Setting the correct injector dead time and required fuel
Turning off EAE correction
Setting the AFR table to 13.0 across the board, turning off EGO correction

I then set out to streat tune the Turbo VR6 Beetle starting in the lower cruise cells and slowly working my way up to the mid range and then into the higher RPM mid Vac areas. Eventually made it into some of the high map and then into light boost. All was going well, the car was running smooth and for the first time I was able to run the car with EGO correction on. I drove the car around the usual loop under various driving conditions. all seams well.

Now to the quirks, When driving down the road if you let off the Accelerator for a few seconds, say like coming up to a traffic light that then turns green. In the 1900 to 2500 RPM range getting back on the accelerator suddenly causes the car to go full lean and hang up there. You have to let off again, free rev the motor quick and then can get back on and it all is fine.

The other is after the car is allowed to cool off, say below 165. the car is already out of Warm up idle is smooth, but as soon as you go to take off the car goes full lean and hangs up there. Same thing, blip the throttle causes it to come back to normal. It will continue to do this when shifting until the car gets over 170 then it is some what normal aside from the condition I described above.

I now don't know where or what I should adjust, To me it seams that its not getting enough initial transiate fuel, and when in Decel its pulling all the fuel off the wall and that's why its going full lean. Any help here would be greatly appreciated.

[elutionsdesign]

It is a tuning issue and I'd say its related to your ignition table and acceleration enrichment settings. First, I really don't like your ignition table. Second, you're not using your accel enrichment very often because the threshold is so high but when it does come on your adding so much fuel the AFR's are dropping below 10. Example, idling at 2-2.5 mS pulse width, good and normal, but if you stab the gas hard enough you activate the accel and its adding 6 mS to the pulse width, like 300% more fuel which is way too much. Set your threshold much lower so it comes on more (use it for what its intended to be used for) and set your added fuel to a fraction of the pulse width, not a multiple of it. And extend the accel time to 0.7-0.8 Seconds.

Now the lean you are seeing is caused by the engine wanting more fuel at that point but part of that is the timing is so high right there and very much lower approaching it. If you just add more fuel to that spot in the VE it would help but the real answer is to fix your timing table, timing is so important that it needs to be the first thing done before you start doing a lot of VE tuning. Small timing changes make a big impact on VE. Think of the timing table like this, the x-axis (rpm) is the centrifugal advance, named after the days of distributors with weights that forced the timing to increase the faster it spun. This should move from roughly 10 BTDC all the way at idle (left side of the table) to whatever the maximum timing specification for the motor all the way to the right, SMOOTHLY INCREASING as you move left to right. Yours does not smoothly increase and it actually decreases past 3700 rpm. The idea is to have the peak cylinder pressure happening between 15 and 18 degrees ATDC, as rpm's increase everything is moving faster therefore the plug needs to fire sooner. You can look up the peak advance for your motor on line somewhere I'm sure. Also see if it has a vacuum advance specification, that can be overlayed on the table once you've worked out the centrifugal advance but DON'T ADD THEM TOGETHER, that's not how it works.

[elutionsdesign]

I did a quick review of the internet, it seems VW specified 6 degrees BTDC at idle timing, full centrifugal advance 33 degrees for the VR6. Most "vacuum" advances are around 20 degrees maximum, boost retard 1 degree per psi or 7 KPa.

[Will Powered]

I did a quick review of the internet, it seems VW specified 6 degrees BTDC at idle timing, full centrifugal advance 33 degrees for the VR6. Most "vacuum" advances are around 20 degrees maximum, boost retard 1 degree per psi or 7 KPa.

I have looked many times over the Inter Web for a reasonable ignition map for this engine. What I did when the car still had MS1 was take a few of the ones I had found an extrapolate them to create my own. A lot of things changed when I switched to MS2 and the ignition map is one that did not translate well.

Also, I have not Dyno tuned the car yet. Ive been trying to get a good base tune so that Im not on the dyne for hours. Thats mostly why the spark map is a bit funky, The higher resolution of MS2 made it look crazy. I never thought it to be to much concern because I never had any indication of detonation or loss of power ( at least that you can detect on the street)

So if you could provide me with where you found the VW ignition information. And as for the map I found that the car idles best with the ignition set to around 12-14. Are you saying the I should be gradually increasing timing up to a max of 33 degrees while going up in both x and y axis? Then dropping boost after 100Kpa ranges?


Thanks for all your help so far.

Will

[elutionsdesign]

I sent you a PM.

[nathanhardy]

I have a don't blow it up spark map from Paul who is a kill vr6 tuner I can send u if you want the only thing I change was idle timing!

[Will Powered]

So I did massive VE table changes once again. IT is getting better and better each time we drive the car, and tweak out or ignore the anoying full lean spikes. I'm attaching the latest MSQ so everyone can see it. Here are a list of some of the changes I made

With help from elutionsdesign I adjust my timing map, not exactly like factory or but a combination of his and mine. The timing map is now smother and responds well. I deff noticed a loss of power but that is expected when cutting timing by almost 8deg.

Set the AFR table a bit closer to realistic numbers and once again used elutionsdesign table and combined them to mine.

Finally made adjustments to the Accel wizard I lowered the TPS DOT down to 85% and set decel fuel to 100. I was not finally seeing the car go rich with throttle changes and lower the accel enrichment to a more reasonable m/s addition.

All these changes made the car run smoother and stayed almost spot on 13.1 afr with the EGO correction on. I still get a full lean condition while driving in the 1800-2100 rpm range. If i am in decel ( lower vac cells in that RPM range and then hit the accelerator to accelerate again the car will spike up to 16.1 and beyond . I immediately let off the throttle and it will resume normally. Like it never even happened. I just have no clue what I could be. The other thing is , it does not always do it. Its like the throttle has to be hit just right. Then it goes nuts.

Any and all help is always great. Thanks

[elutionsdesign]

Can you post up a log obtained with that tune?