Grim Reaper

For those that have been following this board for a couple of months, a discussion came up as to whether the MAT affected the injector pulse width, and if so where is it affected and how can we change this.

I believe we are now in agreement that the MAT does effect injector pulse width (it does); but I have also found the tables that effect it and how to modify them.

There are two specific tables that affect are the "MAT COMP BIN COUNTS" at address x'07FD' and "MAT Delta Multiplier for Inverse Term Look Up" at address x'0880E'.

First, I have found the EGR has a profound effect on how this calculation works, so if you want to make the calculation as "consistent" as possible, you should adjust the "EGR Enable temperature" as soon as possible if you have an EGR - use x'05'. If you don't have an EGR, don't enable the EGR but putting x'FF' in the enable temperature.

As for the tables, I find the "Delta table" has the greatest effect whereas the "MAT comp BIN" is for adjusting boundaries between the "steps". As the "Delta Table's" name implies it is an "inverse lookup". That is for a particular range, increasing the multiplier leans the mixture and decreasing the multiplier richens the mixture.

Also, I noticed that when I defined the tables in my customized version of 8D tdf that I have created, that the "multiplier" values for my AUJP eprom (plus the others available for the public) have lower multiplier (richer) than the ANHT Y-body 8D hack has. In fact, I found the values in the ANHT Y-body's hack gave closer MAT readings in colder temperatures than my AUJP settings.

Right now we are in a bit of a cold snap where I live and I have initially developed a BIN with VE values that keeps me very close to 128/128. This BIN was developed at 10*C (about 50*F). Recently our temperature has dropped to -10*C (about 14*F) and this is when I began testing this; and I now get basically the same BLM/INT values from -10*C to +10*C. As the temperature warms up, I will have further correction values to offer for this "Delta Multiplier Table".

But it looks like I can now use a relocated MAT and get excellent correction values; instead of the "over richness" problem that I encountered as the temperature dropped.

Grumpy, I know that you have a "bench-test", if you are interested in what my original Multiplier Table values were, and what my new values are to test the -10*C to +10*C range, drop me an e-mail. I even have a few tools like my previous version of BINs and my custom TDF; to save you from doing the setup for yourself. But I think that if you do a "benchtest" with only adjusting the "MAT Delta Inverse Look Up Table"; you will find that it indeed works as I have stated and that higher values lean and lower values richen.

Now, I can reuse my relocated MAT and have it do more than act like a fancy thermometer.

Grim Reaper

PS: This information is based on the SD TPI 8D calibration. While a similar table probably exists in the other calibrations, I do not know where the location in the eprom is or have a means to test it. So MAF cars will have to do a little detective work themselves.

TRAXION

Glenn,

Good rundown of the MAT! BTW - seeing as how most of us seem to be focusing on EGR and MAT behaviors lately, I suggested to TunerCat to include the EGR enable temp AND the two MAT tables in the next $8D TDF release. Cooooooooo.

Tim

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• Program your own PROMs!. Read my article to get started!
• Research and Experiment before asking questions.
• This is not a chip store. Go to the classifieds if you want someone to sell you a chip or give you a BIN.

TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

Grim Reaper

Yes, Tunercat should do that. Or they could contact me and I could give them my current "revised" 8D TDF. I have also notice a "KPA Pressure factor table for the EGR". I realize this is one of the factors that seems to cause a problem too, if a person hasn't caused the "enable temperature" to be set lower than what is listed at.

I still question GM's calculation of the "enable" temperature for the EGR. According to the "hack" it is 30* (F or C??), using the standard Celsius to "code" alogrith, it works out to -5*C for decimal 30 or x'1B'; but in reality it is +5*C based on my tests.

But I am just so damn happy to have a MAT correction factor that maintains my 128/128 readings no matter what the temperature is (from -10*C to +10*C). As I build up more "corrections" come the spring and summer, I will be able to tell people what the real correction numbers in the "MAT Delta Multiplier Inverse Table".

I plan to play a bit with the other table too, I think that is useful to adjust the "boundaries" from one temperature range to the next.

Grumpy

I gotta get caught up on some stuff, and revisit this. Just hate it when I miss something.
BUT, bottom line to it all is learning, and I enjoy that.
But even more so is sharing new info..
Thanks
From all of us at CSH, HQ

Grim Reaper

And thank you Grumpy and Traxion for all of your great information. Your absolutely right about the REAL spirit of this board; to share information. I hope I will be able to offer more as I am "fanatical" about testing things and I see a lot of things I want to "play" with.

LBSZ28BLOWN

Glenn91L98,
I'm confused about the MAT tables.
In Tunnercat 8D The MAT Delta Multiplier table is in gm/sec & the multiplier.
The MAT Compensation Counts is in MAT deg C & Counts.
How do I use the Delta table there's no temps in the table.
or am I to use the MAT Compensation table.
My car runs at 128/128 at 24deg in the 124's @ 20deg and in the 132's @ 32deg.
Any help greatly appreciated.


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Louis
Convertable
92 Z28 305tpi Auto
1/4 at 13.23 @ 106.1mph w/Paxton 10psi, Ram air mod,Water methanol inj.,52mm T/B,ASM Large tube runners, ported upper & lower intakes,AFPR,23# injectors,1.6 roller rockers,slp tri-y headers,3in. cat,3in. gale banks cat back system,3.42 gears,17x9 camaro SS wheels, 285x40x17 tires,and much more.
http://www.lbsz28blown.cz28.com

Grim Reaper

You must have "Version P" .

The tables are a tad misleading. Basically the "MAT Compensation Comparison vs MAT" correlate the MAT temp to BIN counts. Then the "Inverse MAT Term LookUp Delta Multiplier Vs Airflow" table correlates the BIN counts (shown as gm/sec) to a "factor" from 1.000 to .125. The BIN counts is the same as the "gm/sec".

The first table is the "boundary" for the BIN counts to a corresponding temperature. You would seldom change this table other than to "tweak" the boundary for the correction table. It's the second table that you actually need to modify.

In the second table, you find BIN count (shown as gm/sec) that corresponded to the MAT *C temp in the first table and then adjust the factor upward to lean or downward to richen.

Let me give you an example, assume from -4*C to +8*C you notice you are running a bit rich. The bin count for -4 is 36 and for +8 its 48. You then look at the second table and notice that 32 has a factor and so does 48. The factor you want to adjust is 32 as 48 is just outside the boundary. Since it is a bit rich you would increase the factor for gm/sec 32 upward.

Conversely, assume in the 20*C to 32*C range your are running a bit lean. 20*C has a bin count of 60 and 32*C has a bin range of 72.

Looking at the second table, you would adjust the factor for 64 downward to richen it.

Now adjusting the "bin counts" for table one is to compensate for temperature boundaries. This occurs when the temperaturee seems "weird" for a very narrow range (eg 10*C to 12*C), then you would adjust the BIN count for 8*C in the first table either upward to lean it or downward to richen it. You seldom have to play with table 1, but you could use it if you chose since the table sort of maxex out at 128 while the second table allows you to define up to 256. You could, conceivably "broaden" the table to give a better definition.

Now for the killer, what my "perfect" MAT tables are and what yours are may very well be different. It really depends at what temperature I started to "perfect" my eprom to 128/128 and at what temperature you did.

If I started setting my eprom at -20*C and then started to compensate my MAT tables, then -20*C is my "perfect" base and all temperature tables will be adjusted from that temp. Conversely, if you started to adjust your eprom at 30*C, then that will be your base. Most likely, over a course of a year, our correction factors will be different because of our "starting" points when we attempted to attain 128/128 perfection.

Bottom line, determine with BIN count corresponds from table one to a temperature and then adjust the factor in table to the corresponding BIN count (shown as gm/sec) for larger temperature ranges, and adjust the bin count in table one only when the boundary appears to give weird results.

TRAXION

Very important further reading on this subject ...

Changes for different weather
MAT tables - taking advantage of cold air box
MAT question

Tim

hvymtl

in relocating the (mat) sensor from the plenum to the plasic air horn (v-6 model), i noticed it is more responsive to air temp changes. i believe the v-6 (mat) sensor is an actual air temp sensor and not a coolant temp sensor that is located in the plenum. my question is, did i thorw off the stock chip calibrations by relocating the MAT sensor on my 87 IROC 350 tpi car, or did i make a change for the better?

11sORbust

I think you made a change for the better. I have used a v6 sensor for about 1.5 years. I believe that it is a air intake temp sensor not a mat. It has a plastic basket with two wires in it and what appears to be a bit of solder connecting the two wires. The air hits the little "thing" inside that "plastic mesh cage" VS a mat sensor that is filled with what seem to be liquid and is a solid piece of metal.

I ran back to back test on both sensors(in a cold air tract). The results was a shorter reaction time to to air temp. The v6 sensor also stayed cooler indicating real air temp. The MAT sensor liked to hold the heat of the engine compartment(bad heat soak). Another thing was the air temp actually will change under wot with the v6 sensor. The MAT was too heat soaked to report a drop in air temp,generally. Don't think the v6 sensor would live on a turbo car or inside the plunum..

I am going to brush up on all this mat stuff then I'll have some good questions on modifying the tables.

TRAXION

FWIW, I am running the V6 airbox, the V6 IAT and Glenn's MAT table that he posted awhile ago. He posted 2 over the history of this board. It's the second one he posted.

Tim