Tune 'n' 'charge 'n' tune

[Loren]

Yeah. Disabling it while you're doing base fuel tunings is a good idea. (even though the latest iteration of auto tune is supposed to account for it) That's what you're missing, though. It can take some fiddling to get just right. You want to let it go a bit rich on tip-in, and try to get ride of the lean spike.

It all just takes time.

[Native]

Indeed it does.
Started experimenting with it today. It was entertaining. At one point didn't think I was going to get the car restarted when I killed it. At another point it seemed as if it was running on 3 cylinders. And, the most enjoyable time was when I learned that setting the enrichment threshold too low, and then incidentally crossing it when shifting, makes a car, shall we say, momentarily undriveable. I think I pulled some neck muscles on that one...

At least I know where to pick up from next time!

[Loren]

Cheap entertainment.

[Native]

Well, it's drivable again. But still bogs momentarily on any throttle addition. Stupid car (-tuner).
Loren, gonna hit you up for a little help. I'm stuck, I've run out of ideas, and have been thru the entire internet on acceleration enrichment.

[Loren]

We'll have to devote 2-3 hours to it one day. Let me know when you have time.

[Loren]

Alternately, you could leave the car with me for a while, and I could play with it. But, you wouldn't learn as much doing it that way.

[Native]

Yeah, I wanna get schooled...
We'll talk.
Thanks!

[jbrannon7]

Yeah, I wanna get schooled...

Too easy, I will pass.

[Native]

[Native]

Pulled Loren away from his control arms and bump steer today, and worked on the Megasquirt for a few hours. Vastly improved idle, made some major, and effective, timing and fuel changes, and attacked the throttle-bog I've been trying to figure out. It's far better.

The lean spike on throttle input, which was followed by a big rich spike the other way, is now just a rich spike/bog. By looking at the AFR gauge, the lean is gone. Loren - I noticed this on the way home. Still, any touch of the throttle - at idle, at speed, high or low rpm, beyond "very gently and slowly" results in a bog and the AFR drops. So, perhaps another tweak of raising the AE .dot threshold, and further reducing the amount of added fuel is in order (after trying to finish rounding out the new fuel map with autotune).

Thanks, Loren! Solid eduation, and a far more driveable car.

[Lava Speed 05]

Pulled Loren away from his control arms and bump steer today, and worked on the Megasquirt for a few hours. Vastly improved idle, made some major, and effective, timing and fuel changes, and attacked the throttle-bog I've been trying to figure out. It's far better.

The lean spike on throttle input, which was followed by a big rich spike the other way, is now just a rich spike/bog. By looking at the AFR gauge, the lean is gone. Loren - I noticed this on the way home. Still, any touch of the throttle - at idle, at speed, high or low rpm, beyond "very gently and slowly" results in a bog and the AFR drops. So, perhaps another tweak of raising the AE .dot threshold, and further reducing the amount of added fuel is in order (after trying to finish rounding out the new fuel map with autotune).

Thanks, Loren! Solid eduation, and a far more driveable car.

Have you checked your throttle plate adjustment? Mine was closed too much and caused me all sorts of issues.

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[Native]

No, I haven't checked it, but I can say that the car was running tip-top before I started making any changes. If it had throttle plate/throttle body issues, they would've made themselves known before I ever started. Right? <---- sincere question...

[Loren]

Glad we were able to make some progress today.

I think I found Publio's "best" tune after I spent the better part of two days working on it a few years ago. I can send it to you if you want to poke around in it. It'll be a little different both because it's an earlier firmware, and his car was different. (1.6, turbo, sequential injection, sequential coil-on-plug) But, here's the timing map. It was delightfully responsive, yet still safe under boost. Might be a good place for you to start, or at least give you some ideas.

Two of the fundamental (and sort of opposite) things that I learned in researching how to set up a timing map:
1. For peak power, you typically want to ramp up to around 30-32 degrees advance by around 3,000 rpm and stay there. Advancing more than that, even though you might be spinning the engine twice as fast, is not required or beneficial. There's some crazy math/science behind that. Something to do with the maximum speed of the flame front, I think.
2. For better economy, you can run more timing advance and less fuel. The two work together. Less fuel gives you a mixture that burns slower. So, you advance the timing to give it time to complete its slow burn. So, for the places you want to get away with "lean", you run more advance, and a lower AFR.

You can sort of think of this in terms of old-school distributors, if you're familiar with them. (just like a lot of the fundamentals of how MS handles fuel can be related to the equivalent parts of a carburettor) You set base timing to something like 10 degrees, just like you would a distributor. And you ramp up to around 30 degrees by 3k rpm... that's equivalent to centrifugal advance on the distributor. And then your fancy distributor might have had vacuum advance. At low load (such as when you're cruising), the engine is making more vacuum. More vacuum would pull on the vacuum advance diaphragm and advance the timing accordingly. Same thing you're doing with the MS... more vacuum = lower kPa = more advance in the cruising area of your table.

Very similar to what you could do with a distributor, but much more tunable and repeatable.

[Lava Speed 05]

No, I haven't checked it, but I can say that the car was running tip-top before I started making any changes. If it had throttle plate/throttle body issues, they would've made themselves known before I ever started. Right? <---- sincere question...

Mine ran fine on the factory tune, the throttle was the cause of all my Megasquirt woes... Once we opened it up a little the car started running fine.

I always figured it was my tune till I loaded Stephen's tune and it was still being finicky. It's a simple thing to try and open it up and count rotations to see if it helps. If it doesn't help, you can just put it right back to where it was.

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[Native]

Matt - Just to be sure, you are referring to the screw that acts as the stop for the actual range of movement of the throttle plate, and not the idle adjustment screw, yes?

Loren - that's one tidy timing table! Not sure if looking at a tune for such a different beast will be of any good, to me, but sure send it over!

[Lava Speed 05]

Matt - Just to be sure, you are referring to the screw that acts as the stop for the actual range of movement of the throttle plate, and not the idle adjustment screw, yes?

Loren - that's one tidy timing table! Not sure if looking at a tune for such a different beast will be of any good, to me, but sure send it over!

https://photos.app.goo.gl/RNp7xygyaboBJK0S2

This screw...

I could always send you what I'm using too. 1.8 turbo with factory 27xish injectors.

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[twistedwankel]

Matt have you ever found that torx socket yet?

[Native]

This screw...

Oh yes. Yah, that screw is open. At one point in my messing around, I had it opened fully to get the car to idle. Fixed some settings, and was able to close it some, but not all - just a turn or two. After today, idle is much much better.

[Lava Speed 05]

Matt have you ever found that torx socket yet? [emoji38]

No, I never did. 🤯

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[Native]

I could always send you what I'm using too. 1.8 turbo with factory 27xish injectors.

Sure thing!