Thoughts on FUEL & SPARK

[Coz_KB95]

First and foremost, want to thank Decipha! Mike, I can imagine just how busy you are, but your taking the time to chime in on my questions here is truly appreciated and has helped steer me in the right direction, especially when I was going down some fairly deep and twisted rabbit holes.

I feel like I've made fairly good progress, and I've learned more than I ever thought I would know not just about what the ECU is doing, but about what these engines are doing. Each time I read the writeups, I learn something or realize something ... and I've read them what feels like a thousand times :)

With that said, I finally worked up the courage to take the car out for a drive with the supercharger belted up. The tune was in a place where I felt fuel was 99% dialed in when warm and spark was in a safe place based on previous NA test runs. Idle still needed some work (which I have since done and gotten much better, amazing what installing a few MAF screens will do!) and I do still have an intermittent issue with stall on declutch coming to a stop. I feel that issue is Dashpot decaying a bit too quickly in the lower RPMs. I've made some tweaks and am waiting for some decent weather to prove them out.

With all that said, here's why I'm posting. I think I've setup Fuel and Spark to be relatively safe. I'm running a 2.2L Kenne Bell. Boost is coming in at 9-10psi and it comes in suddenly, which is a ton of fun on the street, but also makes me very nervous in terms of Fuel and Spark coming to target values when I nail the skinny pedal. So far, no pinging or misbehavior I can hear or feel. I'm looking for anyone's opinion related to maybe tightening up Fuel and Spark specifically for the boost behavior on these Positive Displacement blowers. The ramp up on Perload for Fuel seems to take me immediately to the top of the Base Fuel table and .800 Lambse. I've touched 2.00 perload on more than a few occasions which I believe is safe. I'm wondering if I might be leaving anything on the table with the way I have Lambses set at .90 and 1.05 perload.

For Spark ... I have basically flattened everything above .50 LOAD to head straight to 19 degrees max total. I've done this because I know it's safe as this setup ran 19 degrees locked out at the distributor for 4-5 years. No concerns for scaling load as I'm maxing out at 1.4 -1.5 which leaves me some headspace ... Is there some guidance to tweaking or dialing spark further with these Positive Displacement blowers. Is it safe to add a degree or two as RPMs increase? I'm not trying to milk numbers out of her, she gets up a goes really well. Just wondering what makes sense and would make the engine 'happier' as it transitions into Boost and pulls through the RPM range.

One thing to note: ACTs are expectedly on the hot side. I have my ACT sensor plumbed into the discharge manifold on the Kenne Bell and I do not have my Water/Meth kit setup as of yet. That will be a project for next summer, as the car will be parked for the winter.

Attaching my recent drive log with a few WOT runs (and corresponding stalls coming to a stop) and the tune file that corresponds to that drive. Inviting folks here to take a look and provide their thoughts.

Drive_Log~v2.3_T4M2_95KB_10_18_2025~.xdl

(1.82 MiB) Downloaded 45 times

~v2.3_T4M2_95KB_10_18_2025~.bin

(56 KiB) Downloaded 48 times

Thanks in advance!

[decipha]

I'm surprised with 28 downloads no one has replied yet.

Tune looks ok. You don't have boosted load values plugged in to fn1036. If the maf fails or pegs it'll go lean and if the maf fails you won't be able to drive her unless you dial that in.

You have over a 16% fuel variance at idle, thats not good. Verify you don't have any exhaust, vacuum or air leaks.

stalling is because bank 1 passenger side is dumping fuel on decel. I disabled it for now but definitely need to figure out whats up with that.

I don't know what wideband you have since its not listed in your profile so I just assumed your wot fuel is correct.

You left out the 0 on in the act retard function. That's pretty major. -2 removes 0.2 deg of spark. -20 removes 2 degrees.

This should make her a touch happier.

[Coz_KB95]

Thank you so much for your reply, and taking the time to review the log and adjust the tune Mike. I realize how busy you are and your taking the time speaks volumes ...

With that said, few things have changed since I uploaded those files so I will try to give you a snapshot of where I am at now and hopefully you can give me an idea of what changes I could/should incorporate from the bin you adjusted and sent over.

I decided to update a few things along the intake tract, and that translated into a new MAF, which is an SCT BA-3000. There is now proper screens for straightening airflow before and after the MAF.

The fuel variance at idle and the lower MAF points was troubling for me as well so I went ahead and did a variety of tests looking for air/vacuum and exhaust leaks. Everything seems to check out. I did clean up some of the connections around the Bypass for the Kenne Bell ... I have a suspicion that the bypass valve could be playing into the variance in some way as it does divert and recirculate some of that air in the manifold while under vacuum. The bypass plumbing/opening is closest to the intake port on Cyl#1 ... could be the diversion of air at idle and part throttle is affecting the cylinder fill on bank #1. Just a theory in any case, not sure if you have ever experienced anything similar.

Alongside the new MAF transfer for the BA-3000 I did play with some of the settings in the tune as it relates to Injectors. I reduced the low slope to initially get fueling close at the lower MAF points. This seemed to work really well and brought my low slope pretty close to my high slope (43.763). I also tweaked some of the Injector Timing Settings to values from the Stock T4M0 calibration to see if it made any measurable change in the fuel variance. Below are the related settings I changed:
- Injector Timing SW - CIxxSW: There are two of these, I disabled both
- Injector Timing Value x - xIDTV = 280
- Injector Timing x - xIDTV = 280
- FN1315: All set to 280 below 60.00 Load ... 420 from 60.00 and above

Fuel variance has trimmed down to 10-11% Max and the majority of the variance is related to smaller number of samples that hover around the maf points I'm hitting in transition from Closed to Part Throttle. At closed throttle idling, variances are below 8%. All of this is in the log file from the last drive which I've attached below, along with an updated bin file from that drive.

Coz_KB95-251101_DriveLog.xdl

(1.72 MiB) Downloaded 7 times

Coz_KB95-251101.bin

(56 KiB) Downloaded 8 times

I have not run the car in Boost yet, just did a drive to get a feel for fueling up to half throttle. Trims look fairly minimal and some dialing in of the MAF should get me spot on. She did still stall a few times after coasting at completely closed throttle and declutching. If I declutch with the throttle even ever so slightly open, she comes down to idle relatively well.

Unfortunately, I won't be driving or testing much as winter is here, we've already had our first snowfall and the roads are already covered in road salt and brine.

I did a compare and had a look at the adjustments you made and I had a few questions related to what I should port over to the new calibration:

1) Change to Air_MAN_Vol and Tip-In and TSEIF Transients, looks like they were reduced by ~70% & ~30% respectively. Assuming those are to help with the lean decels and possibly the dump of fuel on Decel, do you suggest I port those over?

2) The change over to Bank #2 for fuel PW control instead of Bank #1 ... I would appreciate your opinion after having a look at the histograms in the new log ... based on the improvement in Fuel Variance is it still necessary?

3) Thank you for the other changes made to Spark and Fuel. The resolution of the tables fits much better with her manners. My first take is that all of those changes are safe to include, yes?

Look forward to your thoughts and really appreciate your knowledge and insight!!

Coz

[Coz_KB95]

... Just to add, the WBo2 readings are from an AEM 30-4110 wideband installed in the passenger bank of the exhaust.