Mustang5L5’s progress thread - Rear window fun

FastDriver said:

All of that sounds solid. Do you know if you can program MS to add air/IAC with the A/C on signal? If not, like Father Time, I'm relegated to building in enough RPM & timing ramp from the idle RPM delta to catch it. In otherwords, the tune is stable enough and reactive in Father Time, whereas Black Jack hits the motor with more air (and therefore fuel) the moment the a/c switches on.

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Yes. You can program an A/C idle up with a delay if necessary. Same with fan.

I just remembered i changed a bunch of idle IAC settings to "see what it does" and then forgot about it. Reverted back to my original settings so we will see if that gets me back to where my baseline was.


Right now i'm chasing this issue on my startup.

The little yellow dip on the top row is injector pulsewidth. RPM is the white curve in the top row. AFR is green and goes lean right after start. For some reason it drops out and I get a little stumble on startup before it catches. It's like my cranking pulse wants to go to normal VE a bit too early, and then goes back to crank.

What i'm trying to see is what is the trigger and/or what is this reacting to. Unfortunately I only get one cold start a day, so I need to think, make a change and try it and when it doesn't work I need to wait til the next day.

Right now i'm thinking my cranking taper is not long enough, but looking through the data it should go another 20 ignition cycles beyond this. I'll get it...eventually.

crank RPM is when the ecu transitions from cranking fuel to WUE and ASE fuel combined with the normal VE table.

I made some changes to crank taper, and less cranking fuel and the next restart was better, but I have to wait another 24 hours for a full cold-restart again. I eliminated the dip but still think i'm too rich on restart. I want to try a much leaner tune fine.

I also need to work through hot start a bit. Steve has a really good video on ASE tuning here

View: https://youtu.be/b5xwmIMHyqU?si=NVgXzhaC5We6Griz



Like i said, car is much more drivable and stable, although probably not fully optimized yet as i haven't done any WOT 3rd and 4th gear pulls on a long stretch of road yet. But now i can dig into the finer details like dialing in my cold and hot starts and PID tuning idle a bit better to eliminate any surge tendency..which there is very little of already.

This graphic is gold with regards to the above video





Let me explain. When you start a cold engine, fuel may not immediately or efficiently atomize. It may pool in the boundary layer of air flowing near the intake/cylinder inlet walls. Because of this, you need extra fuel during cold start, and a little boost of it even during hot start.

Without it, you go lean. Do even if you nail your VE table perfectly, when you cold start or hot start, you tend to run lean. The point of WUE (warmup enrichment) and ASE (After start enrichment) is to add that extra fuel in the form of a multiplier on top of your VE table.

With megasquirt, you can control the amount of fuel, and the taper rate with ASE. WUE taper is controlled by coolant temp. The goal (as seen in steve's video) is to balance this out so that you provide just enough fuel to maintain proper AFR, and taper it off before you start going too rich due to no longer needing that additional fuel. SO you are adjusting your ASE % and your ASE taper rate by watching (or logging) the AFR and making adjustments.

Priming pulse and cranking pulse are also two different fuel modifiers. Priming pulse squirts fuel in prior to crank, and cranking pulse is your fuel added during the crank. You then set a crank RPM value as the transition between cranking fuel and when your VE, WUE and ASE take over...the big vertical jump in the above pic. In my case, i bumped it to 450RPM.

That's summing it up quickly. I spent a hour or so today doing what Steve did and just starting and restarting the car as it warmed up, and then let it cool down and did some starts in the 120-150 degree range. Essentially I watched the AFR and made my adjustments. If it lean spiked right after start, i adjusted the WUE and ASE as needed in that temp range. WHen it started with a good AFR, but then ran a bit rich, i would shorten the ASE taper a bit to bleed that extra fuel off quicker. Was cool to watch this happen. When i got my WUE and ASE right, car would start and settle in right at target AFR. As you watch, you can see it slowly richen up indicating I had to reduce the taper and wean the extra fuel off quicker. Really good feeling to know what changes you instantly need to make.

Once again, made some good progress.

WIll attempt to go for a longer drive this weekend to let the autotune see if it will hit more data cells on the VE table. I did pretty well under 3500RPM but I need to do some 3rd and 4th gear WOT pulls....or shift to 4th at 30MPH and vary pedal load.

Put some more miles on the car this weekend. Tweaking things to the point that it's really nice driving right now. Idle is pretty solid, off-idle torque is there. And the VE table is shaping up. Some good WOT pulls and this thing pulls hard right at 3000-3500RPM+. Slowly tweaking the Accel enrichment to the point where it no longer bucks on light tip-in in higher gears.

That might have to do it for this year. Temps are getting cold, and i'm on summer tires. Now there are leaves and such on the road. This thing makes torque and I need to do a few long pulls in 2nd and 3rd gear. Probably not worth the risk of getting up on a road and getting into it. But cars in a good state to park for the winter. Will just add the 2nd wide-band and that's like it for now. I do have the carbon fiber differential pack to do as well this winter

Here's how the VE table is shaping up.


Interesting observation is the VE dip right around 2300-2900 RPM. Might not have hit that part enough times in autotune so we will see how it shapes up. I need to do more work at the top left corner of the table. More WOT from a dead stop tuning. I avoided this for now to avoid spinning up the tires too much in cold temps. But this table is looking like 3500 is my peak TQ area and HP climbs to right around 5200RPM before dropping off.


In comparison, this is the stock 5.0 base map for a 302 Mustang i started with. You can see how much fuel I had to add for my combo. I remember driving on this setup and it was lean all over.

I lied. Another drive today. I’ve driven it more this fall than I have in the last few years. It’s driving pretty damn nice now. A few things to work out in the tune, but I’m 80-90% there. Working on my Accel enrich. Goes a little lean when I jump on it but I’ll get that.

Couple pics.



Haven’t popped my hatch in a while. Was surprised to see what I have in there.

AeroCoupe said:

You know it doesn’t panhard without that bar….

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I know. I took it off because I wanted to install the carbon fiber clutch packs (box on right side of hatch with gear oil) last winter...and then just never did. On my agenda for this winter.

Well, was decent out weather wise so I snuck out again to do some more driving/tuning. VE table is coming together nicely. Needdd to add more fuel to WOT upper RPMs but I’m close. Had a nice 1-2 WOT pull and then remembered summer tires don’t grab well when it’s cold. But car feels good.


Got it home, and decided to start pulling the rear apart to rebuild the diff. There really wasn’t anything wrong with the diff. Still original clutches and works, but the clutches in my ‘00 are smoked and I wanted two good extra clutches to do the “every other” stack on that car. So I figure I spring for the CF clutch pack for this car, and bought the standard pack for the SN95 to add two used clutches from my ‘88 to.



Called it a night there. Figure let it drain a but and also didn’t feel like getting diff fluid on my tonight.