Feedback on Megasquirt Tune?

[Rojoryu]

Yikes, I see 0.8 to ~0.85 lambda (at peak torque) in that chart which corresponds to 11.8 to ~12.5 AFR.

WAY too lean at 20psi IMO. Like I said, I'd be down in the 10s at that boost level.

I was afraid that was the case. So that could be my head gasket issues? I really need to learn how to tune it myself lol. They are replacing the HG now and are going to re tune it. I told the tuner to put a very conservative, low power tune on it for now.

[Panici]

Did they set base timing and verify (with a timing light) that it matches in fixed timing mode on your ECU?
Was the dyno operator/tuner wearing DET cans (assuming you don't have a knock sensor?)

If you answered no to either of these, I wouldn't be going back to that same tuner.


I could see running that lean on a racecar application where fuel consumption is a concern. But I'd want both EGT & knock sensors to do it.

[Dj Buttchug]

You want to calculate a number for req fuel that makes sense for your engine and injector size. Maybe someone else can chime in here... I am not certain this could be the whole reason the HG failed because it could be from other factors however, when I look at your fuel table it doesn't seem scaled right. In vacuum at idle the VE table is adding 66% fuel. This should be in the 20's

If you are running 775 CC injectors on a 2.5L engine you should be putting somewhere between a required fuel of 8-10 ISH

* agree with panici it is definitely lean* For comparison, on my M42 and my M50 engine my AFR target in full boost is in the mid to high 10s

[Dj Buttchug]

If you answered no to either of these, I wouldn't be going back to that same tuner.

Also this. How reputable is the tuner you took the car to?

[Rojoryu]

Also this. How reputable is the tuner you took the car to?

Thanks for all of the insight from DJ and Panici. He is a very reputable tuner but has not tuned many turbo M20s from what I gather. He focuses mainly on NA builds, not sure if that should matter though. I do not have knock sensors and I cannot confirm if he used DET cans or not. I do know that it was timed with a light for verification before tuning.

[Panici]

You want to calculate a number for req fuel that makes sense for your engine and injector size. Maybe someone else can chime in here... I am not certain this could be the whole reason the HG failed because it could be from other factors however, when I look at your fuel table it doesn't seem scaled right. In vacuum at idle the VE table is adding 66% fuel. This should be in the 20's

If you are running 775 CC injectors on a 2.5L engine you should be putting somewhere between a required fuel of 8-10 ISH

* agree with panici it is definitely lean* For comparison, on my M42 and my M50 engine my AFR target in full boost is in the mid to high 10s

Required fuel might be off for his physical setup, but if the VE table was tuned with this wrong injector size it doesn't matter as long as the AFRs are on target (and you aren't running into the upper numerical value limit [255?] )


The table numbers will be skewed, just as turning off "incorporate AFR" will change the table away from what would be a real approximation of volumetric efficiency.
Some tuners don't know better, just like how you see poor acceleration enrichment compensated for in a VE table.

Thanks for all of the insight from DJ and Panici. He is a very reputable tuner but has not tuned many turbo M20s from what I gather. He focuses mainly on NA builds, not sure if that should matter though. I do not have knock sensors and I cannot confirm if he used DET cans or not. I do know that it was timed with a light for verification before tuning.

You're welcome.

This begs the question, if he isn't used to the platform and wasn't wearing DET cans, how did he arrive at that timing table?

[Dj Buttchug]

Required fuel might be off for his physical setup, but if the VE table was tuned with this wrong injector size it doesn't matter as long as the AFRs are on target (and you aren't running into the upper numerical value limit [255?] )


The table numbers will be skewed, just as turning off "incorporate AFR" will change the table away from what would be a real approximation of volumetric efficiency.
Some tuners don't know better, just like how you see poor acceleration enrichment compensated for in a VE table.

Ah yes.

The VE and timing tables look to be far from finished to me IMO. OP Did the HG fail during the tuning process? * Edit re-read on dyno. I would assume more tuning work needs to be done then.

[Rojoryu]

Ah yes.

The VE and timing tables look to be far from finished to me IMO. OP Did the HG fail during the tuning process? * Edit re-read on dyno. I would assume more tuning work needs to be done then.

It’s actually failed twice. First on the street then again on the dyno.

[Dj Buttchug]

Did you get a peek at the HG point of failure? Alot of times this is a good way to get clues on what is going on.

[varg]

The ignition map matters more. I can't tell you a good opinion on your timing advance table without knowing whether it's accurate or not, what's your tooth #1 angle? Was it verified before tuning? Do you have logs from the dyno pulls?

What I can tell you is that you're leaner than your AFR table on that dyno graph. Why even have an AFR target table if you can't get it consistent on a simple dyno pull? I've tuned a lot of cars, and there's no excuse for that from a tuner. I'm street tuned and my AFR is flatter across a pull than your was on that dyno pull, mine does drop a couple of tenths around peak torque but that is deliberate and it tracks my target so well that I can go do a few pulls with auto tune on and I won't even see the suggested VE numbers change most of the time. You're around 12:1 AFR at peak torque, and at that boost level I'd be around 11 flat. You need a conservative tune to be running that kind of boost with that kind of turbo long term, the turbo is probably fairly close to maxed out. Req fuel and raw VE numbers are less important than your ignition map accuracy, if the AFR is right and the correction factors (MAT, AE, EGO) are working right the VE numbers aren't really critical, you just risk losing resolution at the low end if they're wrong and too small or running out of numbers at the top end if the VE numbers are too big. If you run incorporate AFR target in your tune like I do for example your VE numbers will be way different than someone who doesn't.

what are you using for head gaskets ? maybe time for a cometic or other mls gasket.

Not necessary if the tune is solid. I've run 20psi on an M20 which has good compression and leak down but I later discovered has some pitted cylinder walls and my turbo about the same size. All I have is a conservative tune, ARP studs and a stock head gasket. With a fresh forged build and a conservative tune it shouldn't blow the head gasket.

[Rojoryu]

Did you get a peek at the HG point of failure? Alot of times this is a good way to get clues on what is going on.

Yes, the HG was pushed out a bit on cylinder 4.

I just made it home from being on the road for work. I am going to start digging through the tune and look for things based on what the group here has suggested. The shop still has the car and should have the head back on next week.

[Rojoryu]

It appears AFR Target setting is off...

[varg]

That's not a cause, it's just something that will affect VE values. If you change it, the fuel table needs to be re-tuned. Not holding a consistent AFR during a dyno pull is a tuning problem not a settings problem. The ignition settings are, as mentioned before, more important.

[Rojoryu]

That's not a cause, it's just something that will affect VE values. If you change it, the fuel table needs to be re-tuned. Not holding a consistent AFR during a dyno pull is a tuning problem not a settings problem. The ignition settings are, as mentioned before, more important.

Understood. I posted it since Panici has mentioned it in a previous post. That would mean that the AFR table I posted isn't being used correct? Thanks again everyone for all the insight. I’m learning lol.

[Panici]

Understood. I posted it since Panici has mentioned it in a previous post. That would mean that the AFR table I posted isn't being used correct? Thanks again everyone for all the insight. I’m learning lol.

You got it, that AFR table isn't being used in the fueling calculations if Incorporate AFR is off.
In other words, if you were to change the AFR table values right now, how rich/lean the car is running would not change.

With the caveat that with EGO correction turned on, it would use the AFR table to try and trim the fuel appropriately.



But as Varg said, it's not the cause of your lean condition. That's a result of an improperly tuned VE table.

It does however seem like an amateur move to have the option turned off when it's available for use.