Strange 1-2 shift behavior 22 Mach 1

[veeefour]

MBT is a physical characteristic of the engine, being the timing at which it's most efficient and makes the most torque. It's not just some theoretical number. The tune should be calibrated to match the physical characteristics and the more accurate it is, the better the tune works. I can't figure out why someone would be a proponent of intentionally putting inaccurate numbers in and modifying the torque model to make it work.

No, MBT is a theoretical boundary where the factory tuner saw no gain over - PCM does not know your engine characteristic...not even doable.
That is given specific conditions were met and what someone(regarding his personal believe) decided was safe or necessery.
This is just a number - used or not used to create a spark cap. Some vehicles like GT willl never reach MBT, some will base on cyl pressure limit like GT500.

Borderline + knock does not need to = MBT. It will stop at MBT even if knock adders put it above MBT..

Of course it needs to - this is the proper way to create a safe and efficient tune. Basing solely on MBT is just stupid and dangerous. Even GT500 does not run like this from factory but I guess you know better.

MBT is where your 100% brake torque is, at lambda 1(minus AFR multipiler.)

[Pistol_91]

I'm not saying you can't and it's bad. Just saying is really not necessary with his mods. I have modified mbt tables too lol

[veeefour]

Preface with the car

22 Mach 1 A10
Long tubes, no cats
E85

But this issue has apparently been present before the mods and stated its just became a annoyance

The car when it shifts from 1st to 2nd will bog down incredibly and fall flat on its face. Almost like it?s lost all power. The rpms will drop to 1500ish and then it picks up and drives normal. The issue happens on the 1-2 shift in sport/track/drag. Doesn?t happen in normal because of the 1-3 skip. Seems to be related to lower pedal inputs < 20 percent and slower speeds related to normal driving, taking off from a dead stop. The crazy part is it?s completely random, and impossible to recreate on demand, the once or twice I?ve managed to actually catch it on a log, what I was logging I do t think is what I need to be logging. I?ve tried to dig out those logs with little avail since I?ve been trying to recreate it more reliably they?ve just been lost. From what I saw here are some cliff notes.

Throttle and pedal are constant and throttle doesn?t close

No errors shown

Only thing I?ve managed to catch is spark plummet then come up.

The source says trans shift and one other says torque control.


So my initial question is ideas on what to log?

So I can go out and get one and then maybe diag it better.

Thanks as always everyone.

100% trans tune...cant say what exactly without logs

[engineermike]

No, MBT is a theoretical boundary where the factory tuner saw no gain over -

Which is what I said, minus the theoretical part. Theoretical means it can't or hasn't been proven. MBT can and has easily been proven. By definition, it is NOT just a theoretical number.

PCM does not know your engine characteristic...not even doable.

That is the entire purpose of the calibration...to inform, if you will, the PCM of the engine characteristics. Its just like displacement, for instance. The actual number is entered into the PCM so the PCM will know the engine characteristic.

....what someone(regarding his personal believe) decided was safe or necessery.

MBT isn't personal belief either. Just earlier you admitted that MBT is where the tuner saw no gain over, which is true. It wasn't his personal belief that there was no gain over that. It can and has been proven on the dyno. MBT is also, as I said, when the engine is the most efficient by definition.

Some vehicles like GT willl never reach MBT,

A stock GT will run at MBT at low loads, no problem unless you're running horrible fuel. WOT obviously is a different story.

some will base on cyl pressure limit like GT500.

What year GT500 are you referring to? Ive logged and tuned several 2020+ and they all ran at MBT at light loads and Borderline at WOT. But the 2020+ GT500 also uses a different knock advance algorithm than GT and ecoboost, etc.

Of course it needs to - this is the proper way to create a safe and efficient tune.

So your idea of a safe tune is one that attempts to advance timing all the way to MBT at WOT and just let it ride on the knock sensors? And you believe this to be the proper way to create a safe tune?

Basing solely on MBT is just stupid and dangerous.

Who is doing this? From what you are saying, it sounds like you are the only one.

Even GT500 does not run like this from factory but I guess you know better.

Who said it does?

MBT is where your 100% brake torque is, at lambda 1(minus AFR multipiler.)

Totally agree, plus ethanol multiplier. Its just that in the same post you said that its only a theoretical number and then said its someones personal belief, neither are which can be true with it being where maximum brake torque occurs.

[bkg06gto]

Update: found Maf curve to be wonky. Lots of strange stuff.

Finally bit the bullet and went completely stock. Added the relevant changes for the E content. This is one of the Mach 1s that has the carbon filter sleeve removed. I took the factory curve and scaled it to the change in size (5 percent). Fuel trims look good. Desired/actual load and MAF are virtually dead even. Spark shows it wanting to add in areas .

Car runs amazing. Could use a little more timing I feel at wide open. It still did the 1-2 shift behavior but only once and at a low load small pedal input. My personal opinion is it?s hitting the torque modulation as we previously discussed.

[Pistol_91]

Post another log with the new tune.

[bkg06gto]

More than happy too. Is there any PIDS you would like me to include

[engineermike]

More than happy too. Is there any PIDS you would like me to include

If you post a WOT log, then add Borderline Timing, MBT, Timing, and Knock Advance and make sure the data rate is high. If you're running E85 then you can generally add a lot to the borderline tables and it can ride MBT basically all the time.