MegaSquirt tuning: lean AFR limits?

I think I finally got all of my sensor/wiring issues sorted out and I am now ready to tune my Miata. This is for a 2001 VVT motor swapped into a 94 chassis.

The basic idea, I think, is to try and drive the car at different RPMs and engine loads, and let the laptop take feedback from the wideband and try to hit the target AFRs I've given it.

Problem is, I don't have a great starting map. I have something, so it runs, but I'm definitely seeing some lean AFR in places. 17:1, etc. Now, I'm not applying much load yet, and nothing seems catastrophically detonation-y, but realistically, how bad is it to be seeing such lean AFRs?

Anyone have experience with this and able to either calm my nerves, or tell me how to stay fat?

Shouldn't be too bad. I see 17s while cruising at part throttle at times. If you want to richen it up just make sure you set the AFR targets conservatively and send new data to the ECU often as you run the auto-tune.

If you are nervous about it you can open the VE table and increase the fuel a bit so it is initially richer and the auto tune leans it out.

I had great success getting totally in the ball park with a registered version of tuner studio so you can get the auto-tune feature happening. Then, whilst driving around in "auto-tune" mode, I set the AFR table to follow in "tuning," and fiddle with the AFR in each bin and seeing how the engine likes it.

Turns out my 4AGE doesn't like to go very lean at all.

Megasquirt will try its best to match the AFR's you pull out of your bum. If you pulled good ones, it's happy. If you pulled bad ones, it will do its darnedest to try and match those bad AFR's. Not a fault of MegaSquirt, it's just the way it is. I really like MegaSquirt and TunerStudio.

So I do have a license for VE Analyze Live, and I've been using that to tune. I have a decent (I hope!) AFR target table, but my VE table is off enough that the target seems to get missed a bunch. I suspect it gets missed both rich and lean, but I'm obviously more concerned about the lean mistakes.

Since I only have a little bit of tuning done, I'm thinking of turning on "Incorporate AFR" and going back to square one with my VE table. I haven't looked yet to see if anyone has shared a "pure" VE table that uses this setting, but the idea of being able to change target AFRs without retuning is appealing.

I'm not sure how one goes about "tuning" these numbers when there's no baseline to go off.

I'm gonna follow this as I'm having similar issues in High RPM's. Does the Fuel VE Table need to tweeked if the "Incorporate AFR" is selected?

Without more info about your particular setup and your goals for it, it is very hard to say if your AFR numbers are dangerous.

Is it a track only car, auto-x car, DD?

Do you care about MPG's

When do you see those lean situations?

Are you running a knock sensor or EGT probe?

What is the state of the engine? Any carbon deposits? Did you check?

If you are unsure about any of it, then yes enrich your targets until you see no leaner than 14:1, just to be on the safe side.

This is what I would do. But I am no Miata or MS expert.

dansxr2 wrote: I'm gonna follow this as I'm having similar issues in High RPM's. Does the Fuel VE Table need to tweeked if the "Incorporate AFR" is selected?

I had a completely different response prepared, then I realized I think you're asking a completely different question.

Going from "Incorporate AFR" off to "Incorporate AFR" on requires a complete rebuild of the VE table.

fanfoy wrote: Without more info about your particular setup and your goals for it, it is very hard to say if your AFR numbers are dangerous. Is it a track only car, auto-x car, DD? Do you care about MPG's When do you see those lean situations? Are you running a knock sensor or EGT probe? What is the state of the engine? Any carbon deposits? Did you check? If you are unsure about any of it, then yes enrich your targets until you see no leaner than 14:1, just to be on the safe side. This is what I would do. But I am no Miata or MS expert.

This is a fun weekend car, where fun can mean anything from zipping around the back roads of New England to thrashing around the track at a HPDE.

These are not target AFRs, they're fairly transient and at this point, during times of pretty light load. I'm just concerned that repeatedly hitting those numbers might do damage.

I'm struggling with the idea of just "enrich your targets" as my targets aren't all that lean, 15.5 at worst. The problem is my auto tune misses those targets and I don't know how to make it not do that while it "learns".

Here. This is my target AFR table

This is my mostly untuned VE Table (Incorporate AFR is OFF)

^^^ the last time you posted, I thought you were a regular user mocking the canoes. Now I'm leaning towards water sports enthusiast who is too dumb to paddle. Please add a link to your next post so it can be dealt with appropriately.

For the parts that autotune misses, just go back and manually adjust the table. Generally going up and right add fuel, lower and left remove fuel (ps: very general advice!) when in doubt err on the richer side.

And one other thing to add to what Paul said: Try smoothing the table out a bit - big peaks and valleys typically are a sign it's a bit out of tune. Abrupt changes in color, or craigy mountain ranges in the 3D view, are a sign you need to smooth it out a bit.

What Paul and MSM said. Go back and adjust your table manually. There is definitely some weirdness in your VE table, with some values jumping all over the place.

Also, while I have no miata experience, that AFR table looks pretty lean and steep to me. You have some pretty massive steps, especially RPM wise. I would try to smooth out that table, and see if you still get those lean conditions.

So... yes, I trashed the table I posted above and started afresh, this time with "incorporate AFR" on, as I guess this makes changing AFR targets a no-tune operation.

What I've done today is give myself progressively higher RPM limits. As I start in on a new column, I look at the general trend for that column. The first time I was tuning 2500 area for instance, it started adding 10 to most cells. So I stopped and did +10 to the 2500 column and all columns to the right. The next column then wanted +5, so I did that. What pretty much ended up happening has been that VEAL has gone from adding to subtracting from the table, and my AFRs stay nice and fat.

The other big deal is I turned off VVT control. I looked at a log and realized I was nowhere near hitting my VVT angle targets and that was probably throwing things off. I have to research how to tune the VVT control properly, I had mistakenly thought I could get away with using some other folks values.

Anyone want to weigh in on my methods/madness?

Sounds like you are working the problem. I agree to not mess with vvt if you dont think its adjusting the cam angle properly.

Felt much better about today's tuning than yesterday's.

Also, based on your advices, I copied my post-VEAL VE table into an Excel spreadsheet the MiataTurbo guys have that smoothes maps. I didn't get much chance to play with it, but the result was quite drivable. I still haven't tuned above about 4000rpm, that's for another weekend.

I also found the VVT info I needed:

y8s create gauges on the dashboard for VVT angle 1. enable the test output. set test output duty to 0% start the car. look at the VVT angle 1 and write it down. note this as "minimum". open up the VVT dialog again and hold your RPM at 2000 set the vvt duty to 100% look at the VVT angle 1 and write it down. note this as "maximum". turn off the car and enter these values in the min and max fields. disable VVT test output disable Use Hold Duty. start up.

This stuff is all so simple, if it could just be condensed down into a coherent document. Unfortunately the rate of change is such that I'm not sure this is possible, especially because "howtos" aren't always labeled as to what generation of hardware/software they apply to.

This post is talking about MS3. Which firmware version, I have no idea!