Ignition Advance/Timing Help

[Spencan]

Here are the links in from my google drive:

[Tom]

Can you try posting a cvs file now?

Just the ones with the 1st/2nd WOT runs.....

[Tom]

I think you have a couple things going on in those logs....

1. I think you are maxing out your AFM. The AFM has a big flap inside that opens as more air volume enters. Once the door is fully open, it has no way to measure how much more air is entering. Your car is going quite rich (too rich) up to a certain point, and then when the AFM maxes out, the car starts running leaner and leaner as you approach redline. There are times when you are running 17 or 18psi of boost with AFRs well above 14, which puts your head gasket at HIGH risk of blowing (on pump gas anyway). (As an aside, I don't know if the A-Tune tries to use its MAP sensor to extend the measurable range of the AFM, but based on the injector times, it would appear not.)

2. I have a hunch you are hitting overboost protection on the A-tune chips, which is why you are feeling the cut-out in second. The turbo produces less boost in first gear (in general and as seen in your logs) and so you are able to get through 1st without hitting the limit. In second, under longer sustained load, the turbo is producing more boost (I saw a high over 19psi in there) so the car is probably triggering the overboost protection (and cutting fuel as you noticed). I can't find a published overboost limit on the Rogue site -- just that one exists -- but an overboost protection around 18psi would make sense for a car running stock injectors/AFM, etc. and lines up with your logs and seat of the pants.

To start, I'd turn the boost down to 14psi and do the same logs again. Hopefully, that will fix the 2nd gear cut out, and keep you under the max limit of your AFM. If so, then it would be time to better dial in the AFR curve. Can you adjust your fuel maps? If not, you may be able to improve things with fuel pressure or FQS, etc., but since Rogue is out of business and not able to help, you may want to consider a Vitesse AFM chip from @Fast951. His chips are the gold-standard in my opinion, are fully dialed in, and would eliminate some of the guess work.

[Spencan]

Thanks Tom for the advice. This was the first time did a WOT/fully floored run. I usually do a 3/4 or so throttle run just because how responsive it was. I just checked a log of when I had the FQS setting at 3 and I noticed the same thing.



So it looks like I need to turn the boost down and contact Vitesse then. Thanks again everyone and let me know if anyone sees something else that I need to address.

[danmartinic]

A-Tune cut-off for boost is 19 psi

[Tom]

A-Tune cut-off for boost is 19 psi

I've read that it varied from chip to chip, with some saying 18, but either way his boost did hit 19 at one point....

[cda951]

Hey Spencer, I think cda951 was thrown off by your data sorted out of order like that. That first chart makes it look like the AFM signal is jumping all over the place, but that's because you sorted the data and presented it out of chronological order. I peeked at the very long pdf and admit it was too long to review fully in any meaningful way, but the few pages I looked at showed AFM data moving up and down as expected. I doubt your AFM is bad, or if it is, it's just a coincidence. cda951 can correct me if he saw something I missed. If still suspect your AFM, we have a good/easy test DIY here:

That is 100% what threw me off, please disregard my comments about the AFM.

The timing map you saw with 40deg advance, that must have been in the high vacuum area?

When I calibrated my 951 engine (all stock internals, intake, intercooler, downpipe, etc.) on a dynapack I found MBT at 2500rpm to be ~20deg at 140kpa (WOT), and ~ 25deg at 60kpa (part throttle). If you extrapolate that out to the high vacuum area that's still only ~30deg...

Methodically tuning an engine to MBT takes a decent amount of time and effort. Dyno time is expensive and there are a lot of unqualified and/or lazy "tuners" out there. If you take the time to hold conditions as constant as possible and perform steady state calibration on a dyno capable of accurately displaying torque, you can find where MBT actually is quite well. As I said, in my case that was ~20deg at WOT. Meaning I could keep adding all the advance I want past that value, but no torque increase would result. In fact, I bet at 40deg torque would have started decreasing...

@SirLapsalot Your observations about MBT under full load are 100% correct, but (as you probably know) during light load/high vacuum conditions, a lot of ignition timing is desirable because it helps to light the very sparse air/fuel mixture that is present during these conditions. This is why OEMs installed vacuum advance distributors during the carburetor and mechanical fuel injection era (increased engine efficiency and fuel economy during freeway cruising). EFI made this way better and eminently tunable.

Attached is a screenshot of one of my recent VEMS timing maps for my 951, all road tuned, no dyno time yet---- the light load/high vacuum ranges are all in the high 30s and low 40s, engine runs great and gets same fuel economy as a bone-stock 951 in those ranges.

Interestingly, my max timing values in the higher load range aren't far off your measured MBT values

EDIT: to anyone reading this, do NOT assume my posted timing map is ideal, as every engine is different! I know that I have refined mine since I took this pic, but it is the only one I could find on my computer.

[Spencan]

On your MAP I can tell that RPM is on the X-Axis but what is on the Y-Axis?

Also, I was wondering initially about Off Idle responsiveness and if it was related the ignition advance under that light load/off idle scenario. According to my logs, is there anything to be concerned about?

[Tom]

On your MAP I can tell that RPM is on the X-Axis but what is on the Y-Axis?

Also, I was wondering initially about Off Idle responsiveness and if it was related the ignition advance under that light load/off idle scenario. According to my logs, is there anything to be concerned about?

Most likely absolute manifold pressure expressed in kPa. 1 kPa is equal to .145038 PSI. So in the graph, assuming its kPa, basically everything up to 100 is vacuum, and everything over 100 is boost.

[cda951]

On your MAP I can tell that RPM is on the X-Axis but what is on the Y-Axis?

Also, I was wondering initially about Off Idle responsiveness and if it was related the ignition advance under that light load/off idle scenario. According to my logs, is there anything to be concerned about?

As Tom surmised, the Y-axis of the VEMS timing map is MAP in kPa.

I doubt your problem is with ignition timing, because that is set by the map on the chip, and I am almost certain that the A-Tune would have a reasonable timing map for a stock-ish 951 engine, especially in the light-load/high vacuum range. Maybe not the perfect map for every engine or modification, but within the ballpark.

I would take a closer look at your ignition components. I question the need for an MSD 6AL ignition in a street-driven 951 with a near-stock engine----these are usually only necessary in applications that run quite rich mixtures and with imprecise fuel control (carb or mechanical fuel injection in a drag or land speed application, for example). The multiple spark events at lower RPM are necessary for complete combustion because the spark duration of the CD system is very brief. A downside of the multiple sparks per cycle is the secondary ignition components wear out faster. Check your distributor cap and rotor to start.