MAT/CLT Correction table
 

Hi,

I've been autotuning my car and it's working well, but there always seem to be a lot of cells still changing between my AM drive (Cool 65deg, cold start) and evening drive (warmer - 80deg) and I'm thinking it might be because the MAT/CLT correction has not been setup yet..? I've searched and the only references to this setting I can find use different axis than I have in my version and I'm not sure exactly where to start and how to tune this.

Can anybody shed some light on how to set this up - I have a 2001 manifold/head on a 94 block, N/A.

Thanks !

https://www.miataturbo.net/attachmen...ine=1410381625

Which way have the cells been changing and which cells? If cells close to idle end up consistently decreasing (by auto tuning) as coolant temp increases, I can see this table helping. However, it won't help cells going up/down all over your map.

Are you sure you aren't really looking for the MAT table? It is commonly setup and needs at least the default values for a MS3 to work correctly.

The MAT/CLT table will effectively lean out the amount of fuel being injected, as it adds the coolant temp to the real air temp, in the ratios you set in the table. Theoretically, the coolant temp added represents the heat transfer into the air by the intake piping and intake manifold that is downstream from your IAT sensor. The % contribution should decrease as the air flow increases, as the air will be traveling faster than at idle. So if your idle cells end up being too rich (VE too high) from auto tuning, this table could help lean the final fuel amount out when idling with a hotter than usual engine.

All that being said, I too see the same behavior that you bring up auto tuning... The cells all over the VE map never quite reach a point that they remain consistent with large changes in outside air temps. However, since my engine temp only fluctuates by maybe 20 degrees, once up to full temp and running hard, I believe that standard VE auto tuning ends up taking the majority of this heat transfer into account without an extra modifying table.

I am convinced that we need much better data on the OEM injectors, assuming that is what you are running. Either the injectors or some other part of the fuel system causes lean conditions on hot restarts. However, the lean behavior isn't a consistent factor based on CLT and airflow... Rather time spent heat soaking and engine bay temps seem to be the main inputs. In any case, the MAT/CLT table won't fix the lean on hot restarts problem.

I have searched a lot for a good example of the MAT/CLT table and have yet to find one, especially for a Miata. I am not personally convinced that tuning this table brings much value, unless your engine temp varies enough to cause the mixture to go too rich at high engine temps. However, I would love for someone to show me the way to a 'perfect' MS3 tune outside having access to an engine test cell ☺

If that can be of any help...I tuned the MAT map on my MS'ed MX-6 and it made a big difference in how much EGO correction needed to compensate for temperature fluctuation. I fine tuned the map with a couple weeks of driving but here's how I made my base map. I chose a hot day where it would be 80+ outside. In the morning when it's cooler, I'd start the car and let it idle. Since it is not moving, the engine bay gets heat soaked with allowed me to tune each area of the map while the IATs where climbing. You adjust the values to keep the AFR at idle steady. I did this until it didn't climb and repeated the same thing in the afternoon where it was hotter. That gave me a real good base map that I then tuned by monitoring and datalogging in the next weeks...

ive never used the MAT/CLT table, but I hear it's supossed to do something.

And your AFRs are the same everyday, no matter what the weather is outside? I'd imagine you rely a good bit on EGO correction?

yes, because I tuned the MAT corrections table away from the "ideal gas law" and for the "ideal real life situation law"

You mean you scaled the MAT correction value? I know that a 100% value (ideal gas law) was too high but even by tweaking it, I had no choice but to somewhat tune the table as it was linear...at least in my case.

Yes, tune MAT.

Here is my theory on MAT/CLT. It moves the MAT temp
value used for MAT correction.

When it was added, the ideal gas law was in the base code. To make things right, you had to have a positive slope on MAT correction. Then, the FW guys took the gas law out of the code and you put in what you need, as Scott just said, in MAT correction. Now the right side of that correction will be nearly flat or negative slope. This obsoleted the value of MAT/CLT before anyone ever even tried it.

Totally worthless, it will pull fuel where you want to add it.

That's my theory. And if you go to the MS forums, no-one figured a good way to use MAT/ CLT %.

What Braneak said, use MAT correction only.