Problem adding MAT to $0D TBI 7427, Not pulling timing.

Most of you guys have seen that I am successfully running boost on a 7427 with a 2 BAR map. The truck is running great. I added a MAT sensor to the setup so that when the air coming in gets hot, I can rely on the sensor to pull some timing. For some reason that function is not working. The MAT itself is working, because I can log the temp. This "MAT & CTS Blend Multiplier vs. Airflow" is working as well. I have the MAT sensor flag set.

I have the MAT Bias set to 9.8

As a test I populated the entire "MAT Spark Advance Compensation vs. MAP vs. Temperature" table with -10 degrees, and drove the truck. My timing showed the same as what is in my Main Spark tables. the ECM never pulled any timing base on MAT. I am trying to figure out whats going on. I did find a flag that the CPI bins have set that the TBI does not, that has to do with the MAT, I tried both ways, didn't make a difference. Its at 442F "LD SELECT, ( 0 = VACUUM 1 = RPM) MAT". Could it be something with the Negative or Positive multipliers?

I just noticed the CPI bins do not have anything in the Main spark bias? They are zeroed out.

Cool build...wish i could help..
I did notice you had a malf code 25 Mat HI set in the log, I don't know if this would cause the mat compensation not to run..or when it was set.
as for the biases and how they all play together :mad1:

Quote:

---

Originally Posted by CFI Z51

Cool build...wish i could help..
I did notice you had a malf code 25 Mat HI set in the log, I don't know if this would cause the mat compensation not to run..or when it was set.
as for the biases and how they all play together :mad1:

---

Huh....I didn't even notice that. I don't have a SES light. I will take a look at it. I zerod out the MAin Spark Bias, which I knew would screw up my timing tables. So I copied them first, zeroed the bias, saved, then copied the table back in. Set it up like the CPI bin. I don't think it did anything.

I don't know where everyone is on this forum lately, I am hearing a lot of crickets chirping. Sometimes I wonder if I am one of the only ones left messing with these old PCM's. Probably should have upgraded the 411 LS1 computer and use my HP Tuners.

Quote:

---

Originally Posted by 96lt4c4

I don't know where everyone is on this forum lately, I am hearing a lot of crickets chirping. Sometimes I wonder if I am one of the only ones left messing with these old PCM's. Probably should have upgraded the 411 LS1 computer and use my HP Tuners.

---

I don't think its lack of people on the site, its a shortage of people who know enough to help on the more advanced topics. I have been watching some of these threads as I am interested in using the MAT also when I go to MPFI.

Every time the MAT subject comes up on here it goes about 4-5 post then dies. I'd really like to get in working in my truck but the first time I tried it my BLMs went nuts. Wish I had time to figure it out...

Quote:

---

Originally Posted by PJG1173

I don't think its lack of people on the site, its a shortage of people who know enough to help on the more advanced topics. I have been watching some of these threads as I am interested in using the MAT also when I go to MPFI.

---

Yeah, I thought about that too....I guess I am in uncharted territory here...LOL. Might take me a while to figure it out. Not sure why I am throwing a code and the light is not coming on though. The sensor seems to be working and reading air temp. Maybe that code 25 is part of my problem.

Quote:

---

Originally Posted by brian617

Every time the MAT subject comes up on here it goes about 4-5 post then dies. I'd really like to get in working in my truck but the first time I tried it my BLMs went nuts. Wish I had time to figure it out...

---

I have not seen that. Do you have a MAT or IAT? I have a MAT in the intake.

I know when i switched last fall from a 7747 to the 7427 on my tbi vette i had to 0 the altitude bias in order to get the timing table anywhere near reasonable ,(missing 10* degrees of timing.. ) 30*in the bin(and dash) only read 20ish* on the crank, the timing light doesn't lie.

Also i dont see pe timing added to tunerpro dash or history tables in my logs.? pretty sure its working , pings if i add more then 4*, no knock sensor..

All im saying... you wont know for sure untill you put a light on it.

FYI Im a noob when it comes to EFI ...no experience with tuning mat...but been turning wrenches for 30 years.


(funny you say old PCM its worlds ahead of the 7747 that ive tuned in the past)

Using the diesel IAT in the #8 runner wet manifold TBI.

I added a MAT to mine (7427, mpfi) but I could never really get it to do anything worthwhile. I copied in the CPI parameters and fiddled around with them some, but most of the time, it never really did anything. It seems like for some reason I was having some type of issue that went away when I disabled it. So I just left it disabled and said heck with it. Its still installed in my intake and hooked up, can even still see the temp in the data stream, I just have it disabled in the bin.

Like said above, your probably in uncharted territory, as I do not think many people have fooled around with adding a MAT to the 7427 non cpi bins.

Well, I've kinda given up on the "old" PCMs myself because of shit like this. They are supposed to do something and don't, or the results are the opposite of expected. I know if this gen VI timing cover fits on my gen V like I believe it will, I'm going to retrofit cam and crank sensors in and run a full sequential coil on plug setup.

Quote:

---

Originally Posted by 1BadAction

Well, I've kinda given up on the "old" PCMs myself because of shit like this. They are supposed to do something and don't, or the results are the opposite of expected. I know if this gen VI timing cover fits on my gen V like I believe it will, I'm going to retrofit cam and crank sensors in and run a full sequential coil on plug setup.

---

Did you ever figure out while your 80E was shifting soft? I built a 4L80E for a buddy of mine. It was a 91 model tranny, and he was going to run it on a LS1 PCM in his 68 Camaro, LS2 402 Stroker. Installed the tranny and shifted soft, checked line pressure and it would not go over 150 psi. The problem is in 1994 they changed the Force Motor Solenoid and valve body, it is not compatible with the older electronics, vice versa, new electronic not compatible with old solenoid, which would be the case in your setup. We changed the valve body and Force Motor to a 94 version. Fixed it, firm shifts, line pressure shot up to over 250-275 psi.

Off topic but thought I would mention that, so if you go to the LS1 style PCM, on your 91 4L80E, it will still shift soft, until you change the valve body. You can not just change the solenoid either. They operate at different frequencies.

Part of the reason you get unexpected results is because the code in the 7427 is more complex than the simpler machines like the 747. This complexity increases on an order of magnitude when you get to OBDII and I can promise there are plenty of cases floating around where a newer pcm doesn't do as expected, either.

Sorry for the crickets. You're not the only one left playing with the old pcm's. I just don't have the time that I used to.

CPI trucks use air temp as a compensation. IAT or MAT, it's really no different from the ecm perspective. Sensor generates data, code responds (or doesn't). First, ensure the air temp sensor code is not a current code. ECM will fall back to default temp if there's an error. Then look for minimum temps to enable / disable compensation, or timers that have to expire before compensation begins. Are you certain that the definition file you're using is configured to display timing correctly? Did you notice any performance changes?

Quick edit: It looks like there may be two tables for MAT spark correction. One is a $44A4 and one is at $4493. Not sure how they work... hac says one is negative advance and one is positive. Also a table ID'ed as "base MAT SPK ADV CORR" at $442F. Data obtained at $0041, bit 1 will indicate if MAT spark correction is negative or positive... can be viewed in data stream by altering definition file.

Quote:

---

Originally Posted by 1BadAction

Well, I've kinda given up on the "old" PCMs myself because of shit like this. They are supposed to do something and don't, or the results are the opposite of expected. I know if this gen VI timing cover fits on my gen V like I believe it will, I'm going to retrofit cam and crank sensors in and run a full sequential coil on plug setup.

---

If I could afford it I would be right there with you, but until then I gots what I got....

Quote:

---

Originally Posted by 1project2many

Part of the reason you get unexpected results is because the code in the 7427 is more complex than the simpler machines like the 747. This complexity increases on an order of magnitude when you get to OBDII and I can promise there are plenty of cases floating around where a newer pcm doesn't do as expected, either.

Sorry for the crickets. You're not the only one left playing with the old pcm's. I just don't have the time that I used to.

CPI trucks use air temp as a compensation. IAT or MAT, it's really no different from the ecm perspective. Sensor generates data, code responds (or doesn't). First, ensure the air temp sensor code is not a current code. ECM will fall back to default temp if there's an error. Then look for minimum temps to enable / disable compensation, or timers that have to expire before compensation begins. Are you certain that the definition file you're using is configured to display timing correctly? Did you notice any performance changes?

---

My tune is based off of the stock bin that came with the truck. 1994 TBI BJLF $0D. The base timing is set to zero and has been verified at idle with an adjustable timing light. The only initial performance changes I noticed when enabling the MAT was that, the truck fell on its face under boost from going extremely rich due to the MAT & CTS Blend Multiplier vs. Airflow table. I copied the table out of a stock CPI bin. The fix was to just enter all 1's in the table to make the PCM bias ECT instead of MAT. I think this would only have an effect on AFR and not timing, I may be wrong. I plan on looking at this again later, but for right now its working. The truck's VE tables are pretty close and I am getting the AFR I am commanding in the PE AFR table, under WOT, via my wide-band/boost controller.

I am 99% sure the timing I am logging and commanding is what the motor is seeing. I added a degree to the PE timing table, and the log shows 1 degree added to my timing table during PE. The test that I tried with the -10 degrees in the entire MAT Spark Advance Compensation vs. MAP vs. Temperature table did not pull any timing at all anywhere and did not change performance. Thats one of the reasons I used -10, because I knew I would be able to feel it happen but nothing changed. I may start looking back through the hack to see if I can find something that has been missed.

You are right about that code, when I noticed the overly rich condition and suspected the MAT, I unplugged it and the truck ran great, so that may be an old code.

There are the 2 MAT Spark multiplier, Neagtive and Postive, tables. The way I understand these are, there has to be a value in the table for the MAT Spark Advance Compensation vs. MAP vs. Temperature table to work. So if the negative and positive tables are zeroed out, it basically deactivates the MAT Spark Advance Compensation vs. MAP vs. Temperature table. So I have all 1's in from 55 KPA up to 100 KPA. Which in my case is actually 100 KPA up to 200 KPA, 2 BAR MAP for boost. I need to change my .xdf to show this. I have been trying to change tables to show the 2 BAR MAP readings as I come across them, just have not done these yet.

It sounds like MAT is being used by the code so the question is why isn't spark changing. Check the two additional tables I mentioned. Are they included in your definition file? I haven't had a chance to try and work out how they are actually used but I'm sure they matter.

Quote:

---

Originally Posted by 96lt4c4

Did you ever figure out while your 80E was shifting soft?

---

I changed the voltage curve in the force motor tables to get the pressures in line with what was being commanded. I have about 15 thousand miles on it like that and works perfect.

IF (a big if) I do decide to go late model ECM/Trans control, I would either do it in conjunction with a fresh 80e and a triple disc converter, or the most likely scenario is I would use a MS3 Pro for engine control and a microsquirt trans controller, the microsquirt can be adjusted for any of the 80s, and can also be used to control up to an 8 speed, which would allow me to swap to an 8L90 in the future. The only thing I don't like about aftermarket is the fact that if one shits the bed, I'll be waiting a few days minimum to get another. That could be a huge problem if I'm somewhere away from home, and my truck is a driver not a weekend track vehicle.

Quote:

---

Originally Posted by 1project2many

Part of the reason you get unexpected results is because the code in the 7427 is more complex than the simpler machines like the 747. This complexity increases on an order of magnitude when you get to OBDII and I can promise there are plenty of cases floating around where a newer pcm doesn't do as expected, either.

---

Correct, but with a late model controller, you're paying for it to be supported by HPTuners and EFILive, there is no time where you are out hanging by yourself. If you have an issue all it takes is to ask there, and those guys will give you rock solid info, or they will take the time to figure it out. This isn't a bash against the guys who keep these old boxes alive and viable, I'm just saying that sometimes it gets old being 100% on your own with something that should be really simple.

Quote:

---

Originally Posted by PJG1173

If I could afford it I would be right there with you, but until then I gots what I got....

---

I figure its a lot cheaper than a new truck and can do the jobs I ask it without breaking a sweat. I hope to get paint on it before the winter rolls around but not sure if I'll have the time. I doubt I'll ever sell it after its painted.

Quote:

---

Originally Posted by 1BadAction

I know if this gen VI timing cover fits on my gen V like I believe it will, I'm going to retrofit cam and crank sensors in and run a full sequential coil on plug setup.

---

It will not , even after drilling and tapping the 6 holes for the Gen VI cover (which can be done) , it will put the front seal in a different position than the Gen V cover . Some have grafted portions of a Gen VI pan to the Gen V pan to make it work , but it is a time consuming task.

Short of swapping to a gen VI block or aftermarket , there are these fine folks : http://www.eficonnection.com , but they seem to base everything on a Gen VI setup.


TOM

Quote:

---

Originally Posted by brian617

Every time the MAT subject comes up on here it goes about 4-5 post then dies. I'd really like to get in working in my truck but the first time I tried it my BLMs went nuts. Wish I had time to figure it out...

---

I'm guilty of this. :innocent2: I am wanting to add this to my 93 K1500 too. I see a post or two, and no real progress, then nothing. What searches I have done have been weak.

Any particular MAT sensor part number better than others?

Quote:

---

Correct, but with a late model controller, you're paying for it to be supported by HPTuners and EFILive, there is no time where you are out hanging by yourself. If you have an issue all it takes is to ask there, and those guys will give you rock solid info, or they will take the time to figure it out. This isn't a bash against the guys who keep these old boxes alive and viable, I'm just saying that sometimes it gets old being 100% on your own with something that should be really simple.

---

I can understand this. I'm used to being on my own so I guess I don't really think about it. It's good to get support when you need it.

Quote:

---

Originally Posted by bybyc5

I'm guilty of this. :innocent2: I am wanting to add this to my 93 K1500 too. I see a post or two, and no real progress, then nothing. What searches I have done have been weak.

Any particular MAT sensor part number better than others?

---

I used a 95 model 6.5L Diesel IAT.

Quote:

---

Originally Posted by 1project2many

It sounds like MAT is being used by the code so the question is why isn't spark changing. Check the two additional tables I mentioned. Are they included in your definition file? I haven't had a chance to try and work out how they are actually used but I'm sure they matter.

---

Yes it looks like I have all those addresses populated in my .xdf file. I added the switch at $442f bit 1. The CPI bins had this set, TBI did not. I set it in my bin, still did not work.

My question has always been, what numbers go in this table? I understand it as a blend percentage, but what number is 100% MAT and what number is 100% CTS.

Quote:

---

Originally Posted by brian617

My question has always been, what numbers go in this table? I understand it as a blend percentage, but what number is 100% MAT and what number is 100% CTS.

---

Its kind of hard to explain, but this is the way I understand it. The air moving through the intake at low speed, low air flow, has more time in the intake to heat soak and becomes the same temp as the ECT. As air flow increases, the air has less time to heat soak in the intake as it moves through, so you would in theory want the PCM to bias more toward the MAT sensor, while calculating AFR. This number is a multiplier I have all 1's in it currently, anything less than 1 will richen the mixture up.

Edit--I think I told you guys wrong here. Because of code 25 being set, the PCM was using -40 C as the intake air temp all the time. So this is the reason I was going extremely rich with anything other than 1 in this table. So 1 gives all control to the ECT and 0 gives all control to MAT. This is why anything lower than 1 in my tune at all was way rich, PCM using -40 C as temp to calculate fuel.

Quote:

---

Originally Posted by Nasty-Z

It will not , even after drilling and tapping the 6 holes for the Gen VI cover (which can be done) , it will put the front seal in a different position than the Gen V cover . Some have grafted portions of a Gen VI pan to the Gen V pan to make it work , but it is a time consuming task.

Short of swapping to a gen VI block or aftermarket , there are these fine folks : http://www.eficonnection.com , but they seem to base everything on a Gen VI setup.


TOM

---

:sad: guess the next step is to cut up the cast aluminum vortec cover and graft it on a cast GenV cover, or buy the distributor adapter and external reluctor.

Quote:

---

Originally Posted by 96lt4c4

Its kind of hard to explain, but this is the way I understand it. The air moving through the intake at low speed, low air flow, has more time in the intake to heat soak and becomes the same temp as the ECT. As air flow increases, the air has less time to heat soak in the intake as it moves through, so you would in theory want the PCM to bias more toward the MAT sensor, while calculating AFR. This number is a multiplier I have all 1's in it currently, anything less than 1 will richen the mixture up.

---

I understand airflow the same way, its the numbers (multipler) that doesnt make any sense to me. Example, how would you know how fast your'e going if your speedometer used chinese numbers lol. If anything less than one will richen the mixture, would numbers above 1 lean it out?

Quote:

---

Originally Posted by brian617

I understand airflow the same way, its the numbers (multipler) that doesnt make any sense to me. Example, how would you know how fast your'e going if your speedometer used chinese numbers lol. If anything less than one will richen the mixture, would numbers above 1 lean it out?

---

:mad1:

This is hurting my brain, but I think if 1 is no blend from CTS to MAT and 0 is all MAT control? A number less than 1 wouldnt necessarily richen the mixture but give more control to the MAT which is typically cooler than the CTS. That sound right? Is 1-0 the only range of numbers?

Quote:

---

Originally Posted by brian617

:mad1:

This is hurting my brain, but I think if 1 is no blend from CTS to MAT and 0 is all MAT control? A number less than 1 wouldnt necessarily richen the mixture but give more control to the MAT which is typically cooler than the CTS. That sound right? Is 1-0 the only range of numbers?

---

I have not tried anything over 1, I think the issue I am having is that a turbo really heats the air up, even though I have an intercooler, I am probably still ingesting hotter air than an NA motor. I am seeing what I am comanding on my wideband so I am not really interested in going any richer than 11 - 11.5:1 AFR. I tried scaling the table from 1 at low air flow down to .75 at max air flow and it was still going pretty rich. You will just have to play around with it and see what works.

Quote:

---

Originally Posted by 96lt4c4

I have not tried anything over 1, I think the issue I am having is that a turbo really heats the air up, even though I have an intercooler, I am probably still ingesting hotter air than an NA motor. I am seeing what I am comanding on my wideband so I am not really interested in going any richer than 11 - 11.5:1 AFR. I tried scaling the table from 1 at low air flow down to .75 at max air flow and it was still going pretty rich. You will just have to play around with it and see what works.

---

What kind of intake air temps are you seeing under boost?

Quote:

---

Originally Posted by brian617

What kind of intake air temps are you seeing under boost?

---

Depends how hot it is outside, most I have seen so far is 160*F. Its been pretty cool here for the last couple weeks so they have been running in the 100-120 degree range. I just installed a Meth Injection kit so that will help cool them down under boost. Have not had a chance to run it yet.

This truck has become a plumbing nightmare..LOL

As far as the "Old PCM" comment. It really is amazing what I have been able to do with the stock PCM in this truck. For what it is, its a really powerful PCM that allows you to do a lot of stuff. For one I do not know of anyone running one with boost and a 2 bar map. I was told it could not be done, or that it would be hard to make it work. I have been messing with this thing since February and I have it running great, granted I had to build a new motor, but just learned the hard way.

http://i105.photobucket.com/albums/m...ps6xrpsnlm.jpg

http://i105.photobucket.com/albums/m...psqv3bk3vm.jpg

http://i105.photobucket.com/albums/m...psfxndomih.jpg

http://i105.photobucket.com/albums/m...psguvz9puy.jpg

http://i105.photobucket.com/albums/m...psb3799pws.jpg

Wow. Nice work. Way to stick with it and get it done! Just how much boost are you able to get?
One really nice feature with these older Chevy's is plenty of room under the hood!! Unlike many other vehicles...like our F-Bodies..Ha Ha. At least the corvettes have a fold up front cap.

Kudos :rockon:

Quote:

---

Originally Posted by bybyc5

Wow. Nice work. Way to stick with it and get it done! Just how much boost are you able to get?
One really nice feature with these older Chevy's is plenty of room under the hood!! Unlike many other vehicles...like our F-Bodies..Ha Ha. At least the corvettes have a fold up front cap.

Kudos :rockon:

---

Thanks, right now I am at 8 psi, just changed my waste gate springs, should go up to around 10 now. I wont go any higher than 15 when its all said and done. There are guys getting 15 on 6 liter LS motors with this same turbo. Its a blast to drive on 8 pounds, talk about a sleeper...LOL. Yeah this may be my Guinea pig for my F Body. If I do decide to turbo the Camaro, it will get twins, on E85, should make 1000 HP no problem.

I think I found my problem, was looking through the hack last night and found about 5 MAT thresholds that need to be changed in order to keep code 25 from setting. There is a HI Temp setting that will set code 25, which in my stock TBI bin is set to -40 degrees C. Which in turn effects the Default MAT temp if error 23/25 setting, which is set to -40 degrees as well. So since I have code 25 set, the PCM is using -40 C for MAT calculations. Changing this to match a CPI or 4 cylinder s-10 bin should fix it.

Here is a screen shot, and I attached an updated .xdf file below. Hopefully this works and can help others who want to add MAT.

http://i105.photobucket.com/albums/m...psn5allffm.jpg

Good work finding these. I caught something yesterday and ended up spending all night shivering under blankets.

Quote:

---

So since I have code 25 set, the PCM is using -40 C for MAT calculations.

---

I thought you said you could see MAT on the scantool? You would see -40C if it went to default temp.

Quote:

---

Originally Posted by 1project2many

Good work finding these. I caught something yesterday and ended up spending all night shivering under blankets.



I thought you said you could see MAT on the scantool? You would see -40C if it went to default temp.

---

That is true, the MAT shows the correct temp. If you download and watch a little bit of the log I posted in the first post, you can see that code 25 is set, but the MAT is still showing the correct temperature. Maybe that's why I have no light on...LOL. Either way my bin is set to -40 C as the "HI" temp that would set 25, so I know for sure that is not right. We will have to see what happens when I get a chance to change it, and drive it. Hopefully this is the fix.

Its fixed! That did it. I am going to have to go back and look at the CTS and MAT blend table.

I think I told you guys wrong here. Because of code 25 being set, the PCM was using -40 C as the intake air temp all the time. So this is the reason I was going extremely rich with anything other than 1 in this table. So 1 gives all control to the ECT and 0 gives all control to MAT. This is why anything lower than 1 in my tune at all was way rich, PCM using -40 C as temp to calculate fuel.

Just looking around and found a thread on Fullsize chevy talking about adding MAT.

http://www.fullsizechevy.com/forum/g...-sensor-7.html

Basically anybody that has added MAT to a TBI bin, and did not fix the code 25 issue, is not getting correct fueling.

Quote:

---

Originally Posted by 96lt4c4

Its fixed! That did it. I am going to have to go back and look at the CTS and MAT blend table.

I think I told you guys wrong here. Because of code 25 being set, the PCM was using -40 C as the intake air temp all the time. So this is the reason I was going extremely rich with anything other than 1 in this table. So 1 gives all control to the ECT and 0 gives all control to MAT. This is why anything lower than 1 in my tune at all was way rich, PCM using -40 C as temp to calculate fuel.

Just looking around and found a thread on Fullsize chevy talking about adding MAT.

http://www.fullsizechevy.com/forum/g...-sensor-7.html

Basically anybody that has added MAT to a TBI bin, and did not fix the code 25 issue, is not getting correct fueling.

---

That does sound like the problem, now I have to figure out how to add those items to my XDF

Quote:

---

Originally Posted by brian617

That does sound like the problem, now I have to figure out how to add those items to my XDF

---

I did it for you man! A couple posts up. My .xdf is setup for boost, but you can still use it to change the settings in your .bin file.

Thats cheating lol. I'd like to learn how.

Catch a fish for a man and he can have one meal, teach him how to fish and he wont go hungry?

I'm also using $OE, so locations are different.