Adding MAT to 350 TBI $0D/7247

[woody80z28]

I've gone with Vortec heads on my TBI with a carb intake (no coolant passage under the runners) and headers (no heat pipe to air cleaner) so even with my AE dialed in when up to temp, in cold weather and especially with a cold engine I get a nasty lean stumble on accel. When I add AE, I get a rich bog when up to temp at moderate ambient temp.

So...the plan is to add a MAT sensor and more AE when the manifold temp is very cold. I bought a MAT from Napa to go in the #8 runner (#ECH TS5100) http://napaonline.com/Catalog/CatalogItemDetail.aspx?A=ECHTS5100_0060260652&An=0&Ar=AND%28P_RecType%3aA%29 and modified a CTS plug to wire it in.

From what I read, 1 wire goes to pin B-9 and the other to ground. I grabbed the BPLH 4.3 bin from here and copied these settings:
MAT Sensor flag
Error 23 Low flag
Error 25 High flag
MAT Spark vs Vac vs Temp table
MAT Spark Multiplier vs MAP
MAT/CTS Nultiplier vs Airflow
TPS Difference AE Correction factor vs MAT

I dont know if anyone else here has done this yet, but I'm gonna wire it in soon and see how it works. If you have any tips/tricks I should know about before I do it, give a hollar. I have a 1-mile drive to work and the lean stumble during cold mornings drives me nuts! haha

[JeepsAndGuns]

I dont have any info that can help, but I will be watching this thread and watching your results closely. If it goes well, works, and you have good results, I may add one to mine.

[PJG1173]

I'm watching this one too.

[EagleMark]

So the option is in $OD but never came on a truck? I think I have seen it in my sons $OE we are doing right now and wanted to add this.

I had a 1993 Caprice 9C1 option cop car (NotaCop) 1228746 ECM I think and it ran well, got great fuel mileage compared to TBI trucks I have had without but I attributed that to aerodynamics? It is another measure of further calculating mixture by adding air desity so I don't see that as a bad thing.

Now IAT and MAT are very different and location of MAT can change temps dramatically, so need to see what bin says for temps and check location of MAT mounting in intake manifold. Where were MAT sensors placed on car engines then? Since truck did not have it? Strange it is in bin?

IAT would be in air coming in engine and less temp, closer to ambient temps. The old caprice above and my LT1 are both IAT. MAT, Manifold temps are much hotter. I am curious what scalers and tables or? say for adjustments...

[gregs78cam]

"Title: MAT Sensor
Location: 400B-Bit 6
Usage: Air Fuel Mode Words
Tips: Enables MAT sensor calibrations. Checkmark to enable MAT sensor calibrations. This can also be used for a IAT sensor. "

And I would think that the two parameters that would have the most impact on fueling would be:

Title: MAT & CTS Blend Multiplier vs. Airflow
Location: 4AE1
Usage: BPW Parameters
Tips: Larger multiplier = more CTS blended into MAT. Used only if L400B Bit 6 "MAT Sensor" is enabled.
Conversion: Multiplier = X / 128

Title: TPS Difference AE Correction Factor vs. MAT
Location: 4B80
Usage: Acceleration Enrichment Tables
Tips:
Conversion: Factor = X / 128

Now these are for $0E, but $0D should be the same, in almost the same location. I wouldn't necessarily say that MAT temps would be hotter, but they would vary over a much LARGER range.
In TP go over to tools and click on "parameter finder". type in MAT.

[EagleMark]

MAT temps are much hotter than IAT temps. I've done this research.

Now didn't you just find some diesel boost error codes in this PCM too? Well guess what? 1995 6.5L turbo diesel has a MAT when I looked it up on Rock Auto. You can tell by the way they mount they go into intake manifold.
http://www.gearhead-efi.com/Fuel-Injection/attachment.php?attachmentid=1650&stc=1&d=1329375713

The only other sensor for that year period, so far I can find is all IAT sensors which usually look something like this and go in incoming air tube usually air cleaner or tubing from MAF.
http://www.gearhead-efi.com/Fuel-Injection/attachment.php?attachmentid=1651&stc=1&d=1329375713

I'll go one step further and say that you can use a CTS which is way cheaper because the ohm meter tests are identical. But response time from CTS is not as fast. But half price and last forever in air... I already did that years ago with a 1228746 ECM conversion on a Scout II.

[JeepsAndGuns]

I'm cheap, so I would probably go grab a couple of the IAT's from the pull a part with their connectors. I remember seeing crapload of them on diffrent GM cars while going through there the last time.

One thing that makes me interested, is woody's discription of his engine. My MPFI intake does not have a exhaust crossover like my old one does, plus I am seriously concidering a set of headers after seeing a back to back dyno run with stock manifolds and two diffrent types of headers.

[PJG1173]

So the option is in $OD but never came on a truck? I think I have seen it in my sons $OE we are doing right now and wanted to add this.

I had a 1993 Caprice 9C1 option cop car (NotaCop) 1228746 ECM I think and it ran well, got great fuel mileage compared to TBI trucks I have had without but I attributed that to aerodynamics? It is another measure of further calculating mixture by adding air desity so I don't see that as a bad thing.

Now IAT and MAT are very different and location of MAT can change temps dramatically, so need to see what bin says for temps and check location of MAT mounting in intake manifold. Where were MAT sensors placed on car engines then? Since truck did not have it? Strange it is in bin?

IAT would be in air coming in engine and less temp, closer to ambient temps. The old caprice above and my LT1 are both IAT. MAT, Manifold temps are much hotter. I am curious what scalers and tables or? say for adjustments...

the 93-94 CPI 4.3L found in S10's and blazers had a MAT using $E6 and $0D. I'm still trying to get the basics down before venturing into this. I have been courious about this for a while since I am in the same boat. aftermarket intake with no crossover under the plentum. I've noticed this motor is sensitive to changes in temperatures and was hoping I could use this to counter that. BTW what is the BCC for the cop car option? I have a set of cop car injectors I'd like to lookup the settings for.

[EagleMark]

I'm cheap, so I would probably go grab a couple of the IAT's from the pull a part with their connectors. I remember seeing crapload of them on diffrent GM cars while going through there the last time.

One thing that makes me interested, is woody's discription of his engine. My MPFI intake does not have a exhaust crossover like my old one does, plus I am seriously concidering a set of headers after seeing a back to back dyno run with stock manifolds and two diffrent types of headers.That exhaust crossover is to help engine and intake warm up faster for drivibuity. The crossover works in conjunction with heat riser valve in one side of V engine that is closed when cold, spring loaded and forces exhaust through intake. Opens when hot.

Another thing that is part of that and could help you guys is a hot air tube off header to intake. GM designed air filters are plentiful that require no valve or vacuum hoses. It sucks hot air when cold and opens when warm. Helps engine run better when cold but was installed to prevent icing of TB or carb back then...

Dyno numbers are WOT high measures of HP and tourqe. So yes you can get more at WOT high RPM but you give up drivability in all situations except 1/4 mile...


the 93-94 CPI 4.3L found in S10's and blazers had a MAT using $E6 and $0D. I'm still trying to get the basics down before venturing into this. I have been courious about this for a while since I am in the same boat. aftermarket intake with no crossover under the plentum. I've noticed this motor is sensitive to changes in temperatures and was hoping I could use this to counter that. BTW what is the BCC for the cop car option? I have a set of cop car injectors I'd like to lookup the settings for.Thanks I'll look one up.

I don't remeber the bin to TBI 9C1 Cop car, it was in a laptop lost with coffee through keyboard incedent... the 9C1 RPO code option was so much more than just bigger injectors! Cool Car! I miss NotaCop...

[woody80z28]

I love this site already! Glad to get some more brains on this subject.

I looked at IAT vs MAT and decided on MAT for a couple of reasons. The TBI runners are wet flow, so the atomized fuel also plays a part in the air temp. I read (I think on TGO) that TBI runners under certain circumstances can actually be 20-40* colder than ambient temp...and the runners are right where the fuel wants to stick to when cold, so that's gotta be the best place to get a reading.

IAT seems like a better match for MPFI engines where the runners are mostly dry and the fuel does not skew the air temp. (My Beretta is MPFI/IAT.)

[woody80z28]

I'm cheap, so I would probably go grab a couple of the IAT's from the pull a part with their connectors. I remember seeing crapload of them on diffrent GM cars while going through there the last time.

One thing that makes me interested, is woody's discription of his engine. My MPFI intake does not have a exhaust crossover like my old one does, plus I am seriously concidering a set of headers after seeing a back to back dyno run with stock manifolds and two diffrent types of headers.

I think a MAT would be more functional than IAT, but that's another option to try and test.

My setup, from a cold-drivability standpoint is a big step back from stock I've come to realize. Stock TBI has the exhaust through the intake to the EGR and a coolant passage under the runners with a heater pipe from the exhaust to the air cleaner. I have none of that. I assume this is why the MAT wasnt needed stock and mine is a bear.

[EagleMark]

IAT seems like a better match for MPFI engines where the runners are mostly dry and the fuel does not skew the air temp. (My Beretta is MPFI/IAT.) That would seem to be correct and I agree that MAT could be better choice. But my 1993 TBI car had IAT. But id had exhaust crossover, heat riser and hot air tube, stock! Your's I believe would be better with MAT because of all those things removed.

The programming of parameters used would be different for both I assume because temps would be different. Although tests I have done show ohm readings same as coolant CTS sensor. So it's what the ECM/PCM is programmed to do with that reading.

[gregs78cam]

I think a MAT would be more functional than IAT, but that's another option to try and test.

My setup, from a cold-drivability standpoint is a big step back from stock I've come to realize. Stock TBI has the exhaust through the intake to the EGR and a coolant passage under the runners with a heater pipe from the exhaust to the air cleaner. I have none of that. I assume this is why the MAT wasnt needed stock and mine is a bear.

That's the way the Camaro is, 2 TBIs on a RPM AirGap manifold. I just don't know if I will get the MAT sensor put in before I go MPFI, or not.

[EagleMark]

G1 has brought up another point. Does the intake have somwhere to put a MAT sensor? If not you need to drill and tap, with manifold off and big job.

But in thinking this through intake manifold temps are differant/higher than IAT temps becuae the intake is bolted to engine, engine is behind radiator getting warm, attached to heads etc... but you guys have eliminated major heat sources like exhaust heat crossover, EGR into intake and coolant passages? So not even coolant flow now?

So MAT are probably a lot closer to IAT temps. Without a place to put MAT sensor then IAT would be better than nothing and in your cases not as far off as regular engine.

So it boils down to what the mask has in it's paremeters it's looking for and adjusting to.

[EagleMark]

I was just looking through $OE and found "MAT & CTS Blend Multiplier vs. Airflow" since we have been told CPI uses MAT sensor, does it also use MAF sensor? In V8 TBI it is set to all 0s. So would have to know what vs. Airflow is?

Now this one looks promissing for AE which seems to be issue with cold engines. In V8 TBI $OE it is set to all 1.0 for all temps.
"TPS Difference AE Correction Factor vs. MAT"

[EagleMark]

Also found this but would not have noticed it had anything to do with MAT if it weren't for comments written by 93V8S10!

"MAP Difference AE Correction Factor vs. Temperature" "Tips: Used to make corrections to TPS AE in relation to MAT/ IAT sensor data."

[woody80z28]

That's the way the Camaro is, 2 TBIs on a RPM AirGap manifold. I just don't know if I will get the MAT sensor put in before I go MPFI, or not.
Do you have a thread about said Camaro? Mine also has an RPM Airgap and it is a cold-blooded son-of-a... One more reason I'd like to go MPFI with a single plane and dump the 750.



Also found this but would not have noticed it had anything to do with MAT if it weren't for comments written by 93V8S10!

"MAP Difference AE Correction Factor vs. Temperature" "Tips: Used to make corrections to TPS AE in relation to MAT/ IAT sensor data."
Good catch, Mark. I'll take a look at that table on the 4.3 BIN and see how far off it is from the 5.7 one.

[EagleMark]

Here's Gregs thread:
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?164-My-Dual-TBI-Camaro-Project&highlight=dual

There were 2 other options I noticed in post on last page too that should be compared to CPI bin. Maybe more but that is all I saw at the time. The CPI settings should be a good start point.

[93V8S10]

Sorry, but that was a mistake.

The correct comment for "MAP Difference AE Correction Factor vs. Temperature" is "Used to make corrections to MAP AE in relation to temperature."
The correct comment for "TPS Difference AE Correction Factor vs. MAT" is "Used to make corrections to TPS AE in relation to MAT/ IAT sensor data."

[woody80z28]

G1 has brought up another point. Does the intake have somwhere to put a MAT sensor? If not you need to drill and tap, with manifold off and big job.

But in thinking this through intake manifold temps are differant/higher than IAT temps becuae the intake is bolted to engine, engine is behind radiator getting warm, attached to heads etc... but you guys have eliminated major heat sources like exhaust heat crossover, EGR into intake and coolant passages? So not even coolant flow now?

So MAT are probably a lot closer to IAT temps. Without a place to put MAT sensor then IAT would be better than nothing and in your cases not as far off as regular engine.

So it boils down to what the mask has in it's paremeters it's looking for and adjusting to.

My biggest issues are when the truck is cold started on my 1mi trip to work in the morning. And from what I understand, in that situation the MAT will actually be colder than ambient temp due to the atomized fuel until the engine starts to get up to temp. I have noticed (even when up to temp) that the TBI itself is much colder than the runners and the runners are colder than the valve covers, for example. I think the closer my reading is to the combustion chamber, the more accurate I can be with the calibration.

Stock TBI intakes and also my Edelbrock Vortec carb intake have a provision for the sensor in the #8 runner with a plug. Piece of cake. (Visible in this pic:)
http://www.motortopia.com/files/cars/album_drivetrainoverhaul/4e4c9765ec441/IMG_6615JPG_Thumbnail1.jpg

[EagleMark]

True if your engine was stock and using stock calibration. But your engine is not stock.

We found enough paermeters to change that I beleive it can be tuned by adding this IAT/MAT part to the equation!

NY is pretty cold in winter. A hot air tube from header to air cleaner with GM valve and cold air intake would help too! You start to get warmer air within a minute. When watching IAT temps with mine in winter it would stay closed at start and half way, blend most of day. Was shut very fast in summer.

[JeepsAndGuns]

That exhaust crossover is to help engine and intake warm up faster for drivibuity. The crossover works in conjunction with heat riser valve in one side of V engine that is closed when cold, spring loaded and forces exhaust through intake. Opens when hot.

Another thing that is part of that and could help you guys is a hot air tube off header to intake. GM designed air filters are plentiful that require no valve or vacuum hoses. It sucks hot air when cold and opens when warm. Helps engine run better when cold but was installed to prevent icing of TB or carb back then...

I have one of those large open element air filters setting on top of my TB. It sucks the air in from directly under the hood. There has been no heat riser valve or anything of the like on this old jeep probably since the 80's....:laugh:
When I install my MPFI intake, I will not be able to reuse this air cleaner. I am currently working on a intake system made up of some elbows and pipe and will install a cone style K&N on the end of it, and will be drawing air from behind the grille. Would be hard to draw hot air from there.
Down here in bama, we usally have (for the most part) mild winters. It gets down into the 30's, and sometimes even the 20's, but rarely less. But it get well over 100 in late summer down here, and high humidity. So I dont think I will have as much problem as you guys do up north.

But on the note of MAT being better suited for TBI, and IAT better for MPFI. The funny part is, the factory 4.0 SMPFI on my wranger, uses a MAT.

[93V8S10]

In my opinion the hot air tube is not needed at all with MPFI in a southern climate. I used to have my old carberated V8 S10 set-up with a duel snorkel air cleaner with hot air tube on both sides, but after I build this MPFI truck, I can find no difference with or without.

[gregs78cam]

Quote from my Dual TBI thread: just didn't want to type it all out. but should illustrate the major swing in wetflow intake temps.



My next step. After driving it a few days ago and idling up my half mile driveway as usual I got out and the TBI adapter was so cold it had moisture condensing on it when it was about 70 outside and the engine fully up to temp. I then let it idle while looking over the DL and making a few changes and the idle started to creep up with the IAC completely closed. Got out and the adapter had warmed up from the fan blowing on it.


Intake warmed up which causes the fuel to atomize better which brought Idle up.

[EagleMark]

In my opinion the hot air tube is not needed at all with MPFI in a southern climate. I used to have my old carberated V8 S10 set-up with a duel snorkel air cleaner with hot air tube on both sides, but after I build this MPFI truck, I can find no difference with or without.I would agree. But the GM one is fully functional without sensors or vacuum hoses and would mechanically sense hot air and close. But I still agree, not needed down south. Up here it's a great thing!


Quote from my Dual TBI thread: just didn't want to type it all out. but should illustrate the major swing in wetflow intake temps.

Intake warmed up which causes the fuel to atomize better which brought Idle up.Wonder if adding the MAT/IAT parameter to fueling equation would cure that issue?

[93V8S10]

I would agree. But the GM one is fully functional without sensors or vacuum hoses and would mechanically sense hot air and close. But I still agree, not needed down south. Up here it's a great thing!
I agree that the GM design is great, and that is what I was using with my custom air cleaner. I mainly wanted to point out that there is a big difference in TB temperature between TBI and MPFI.

[woody80z28]

Anyone have a pic of the stock thermac setup? I googled without success. Mine was already removed when I bought the truck.

[EagleMark]

I agree that the GM design is great, and that is what I was using with my custom air cleaner. I mainly wanted to point out that there is a big difference in TB temperature between TBI and MPFI.Ah! Missed that part, yes from evaporting fuel!

Just thought, my LT1 has no hot air tube! But does have a heater hose to TB which guys remove... but I don't remember any MPFI having hot air tubes? Now I'll have to start looking at other MPFI as I don't remember any others having heater hose water running through them... why would there be icing issue in MPFI TB if no gas evaporating making it colder like TBI or carb.

[FSJ Guy]

What about using the MAT/IAT to adjust timing? There is a MAT spark bias @ 0x4140 and a MAT Spark Advance Compensation vs. Vacuum vs. Temperature table at 0x4433. I understand what that table will do and how the bias compensation will allow for negative numbers in the table.

However, what about the MAT Multiplier for Negative Spark Advance vs. MAP? And there's also a similar table for POSITIVE Spark Advance vs. MAP. (locations 0x4493 and 0x44A4)

Do all THREE of these tables interact with each other? If so, HOW?? :D

I like the idea of being able to adjust timing depending on intake air temp. I have found that during the summer weather, I get more knocking versus cooler days if I am more aggressive with my spark advance.

[EagleMark]

I like the idea of being able to adjust timing depending on intake air temp. I have found that during the summer weather, I get more knocking versus cooler days if I am more aggressive with my spark advance.That is because of air density. MAT/IAC adds that to equation!

[JeepsAndGuns]

So those spark tables could be set up/adjusted to remove or add a few degrees of advance across the board when temps are high or low? That does seem like a very handy feature, as back in my carb days, I would get a little part throttle ping in the summer, that wasnt there when colder.
I have a feeling this is going to be a good thread!

[JeepsAndGuns]

Ah! Missed that part, yes from evaporting fuel!

Just thought, my LT1 has no hot air tube! But does have a heater hose to TB which guys remove... but I don't remember any MPFI having hot air tubes? Now I'll have to start looking at other MPFI as I don't remember any others having heater hose water running through them... why would there be icing issue in MPFI TB if no gas evaporating making it colder like TBI or carb.

The mpi in my wrangler has no hot air inlet or any type of coolant going to the tb or the intake.
I have seen some of those GM TB's and wondered why they had coolant running through them, any idea?

[woody80z28]

The mpi in my wrangler has no hot air inlet or any type of coolant going to the tb or the intake.
I have seen some of those GM TB's and wondered why they had coolant running through them, any idea?

I've wondered that myself...because IIRC (haven't had either stock TB for some time now) the 3100 in my '95 Beretta had the coolant pipe to the TB, but the 3400 from a '04 Impala did not. And both engines are nearly identical aside from displacement...both SFI.

There is no doubt though that once the truck is running, the TBI unit is colder than ambient temp under most - if not all - circumstances.

[PJG1173]

The mpi in my wrangler has no hot air inlet or any type of coolant going to the tb or the intake.
I have seen some of those GM TB's and wondered why they had coolant running through them, any idea?

my TBI jeep has/had a hot air tube going to the airbox from the manifold. I'm almost positive my buddy's MPI had one too.

Wondered why the TBI adapter I took off a 454 had coolant lines going to it. I'm still on the fence on whether or not I should hook the lines up to it when I put it on my other truck with the air gap intake. if I can ever find time to convert it to EFI.

[EagleMark]

Strange finding as to why MPFI/TPI/CPI had hot water tubes and some did not? Don't see the need as icing would not occur with just air? Or maybe it did? But now they do not? But having a hot air tube could be for drivibility on earlier ECM/PCM. Or did the ones with hot air tubes not have MAT/IAT? Guess it's just all part of the evolution of EFI...

But we do know adding MAT/IAT sensor input to the equation will be a benefit!

As for the Truck TBI to spread bore intake adapter having hot water. The engines at that time were used in HD trucks with a carb and light duty trucks with TBI. So they made an adapter for that time period. I was told by an GM engineer at that time the hot water was added during testing on there in house engine dynos, climate controlled, because TBI truck engines at highway speed were still getting icing as they were running higher RPM and pulling more load, hence using more fuel and air, causing more icing. Hot air tube from exhaust was insufficient at highway speed do to wind in engine compartment blowing hot air past hot air tube, instead of being drawn through hot air tube to incoming air to TBI. So they warmed the TBI this way. Later improvements to intake design cured this and the adapter was no longer needed as they now had a TBI intake manifold.

[woody80z28]

Strange finding as to why MPFI/TPI/CPI had hot water tubes and some did not? Don't see the need as icing would not occur with just air? Or maybe it did? But now they do not? But having a hot air tube could be for drivibility on earlier ECM/PCM. Or did the ones with hot air tubes not have MAT/IAT? Guess it's just all part of the evolution of EFI...

But we do know adding MAT/IAT sensor input to the equation will be a benefit!

As for the Truck TBI to spread bore intake adapter having hot water. The engines at that time were used in HD trucks with a carb and light duty trucks with TBI. So they made an adapter for that time period. I was told by an GM engineer at that time the hot water was added during testing on there in house engine dynos, climate controlled, because TBI truck engines at highway speed were still getting icing as they were running higher RPM and pulling more load, hence using more fuel and air, causing more icing. Hot air tube from exhaust was insufficient at highway speed do to wind in engine compartment blowing hot air past hot air tube, instead of being drawn through hot air tube to incoming air to TBI. So they warmed the TBI this way. Later improvements to intake design cured this and the adapter was no longer needed as they now had a TBI intake manifold.

I played around with the idea of swapping in a BBC TBI adapter since my manifold is spreadbore. My thoughts were that it wouldn't make any difference for my short 1-mile trips and might actually hurt max power on a loaded hill climb, etc. but maybe during cruise at low temps it would help.

[JeepsAndGuns]

my TBI jeep has/had a hot air tube going to the airbox from the manifold. I'm almost positive my buddy's MPI had one too.

Yea the TBI ones were diffrent, they were older. But all of the 91 and up 4.0's I have ever seen (in YJ's, ZJ's, and XJ's) I have never seen a hot air inlet. Now the pre 91 XJ 4.0's with the renix injection might be diffrent, I have not worked on or really seen any of those.

[FSJ Guy]

If you look up a 92 Chevy Astro Van with the 4.3L TBI engine, you will find an "Air Charge Temperature Sensor" for under $20. BWD part # WT3036 or the O'Reilley's house brand (Master Pro) # 2ATS7.

The plug looks SIMILAR to the coolant temp sender plug, but it is NOT THE SAME!!! Look at the different pictures on the parts store website and you'll see that the plug you want has two rectangular channels on the short side of the plug. One channel is wider than the other. The CTS plug has channels that are half-round. This is the sender that the plug needs to fit:

http://images.oreillyauto.com/parts/img/large/mpi/ats7-4.jpg
You can get the pigtail for $20 or from a junkyard. I found several simply wandering around the mid to late 90's TBI Chevy's in the yard.

[EagleMark]

Found a thread on Thirgen by RBob on exactly what we are looking for when using or changing MAT/IAT has all the numbers ! :happy:

http://www.thirdgen.org/techboard/diy-prom/265869-mat-pw-compensation-8d.html

[woody80z28]

I went to the local jy and found nothing with a MAT, so I just snipped the half rounds off a CTS plug and it works fine. The pins engage and the clip holds it together, so I don't forsee any issues.

[woody80z28]

Found a thread on Thirgen by RBob on exactly what we are looking for when using or changing MAT/IAT has all the numbers ! :happy:

http://www.thirdgen.org/techboard/diy-prom/265869-mat-pw-compensation-8d.html

I got the table from the 4.3 bin for mine as a starting point since it is TBI and not MPFI, so I think it should be closer. I'll post it up when I get back to my home PC.

[EagleMark]

4.3L came as TBI and CPI. In the $OD bin there seems to be numbers for both depending on what bimasks are selected determines what is used. As mentioned MAT and IAT would be 2 differant sets of numbers. If using as IAT I would start with IAT numbers. If using MAT I would start with MAT numbers. Now because TBI is wet intake and MPFI/TPI/CPI are dry intake numbers would be differant because intake manifold temps would be differant. So IAT numbers from a TBI engine would be best starting point!

[woody80z28]

I am going TBI MAT though, not IAT. So I'll probably just have some tweaking to do.

[EagleMark]

Probaly more then you think! MAT numbers are all from dry intake, TBI is wet intake. So you would have to find numbers from a MAT TBI bin. Does anyone know of a MAT factory on TBI engine?

The only TBI I know of that used this was B and F body $61 and that is IAT.

[woody80z28]

I guess that makes it a good thing to play with, so it can be helpful to the whole community!

[EagleMark]

I guess that makes it a good thing to play with, so it can be helpful to the whole community!:thumbsup:

I'm trying to find the patch for $61 that expands that table. It is IAT but from factory only has like 4 entries in warm areas, expanded covers from cold to hot. I'd like to add IAT to my kids $OE conversion on his IH engine.

[907 Chevy]

I think it would be beneficial to add an mat sensor,however I'll add to what others have said earlier in the thread and say that most of your issues would be alleviated by going back to a stock air cleaner setup with a heat riser off your headers.
I'm having the exact same issues with my engine running a single plane manifold...crappy cold start idling,throttle icing,low idle,and atrocious fuel economy in cold weather.
With ambient temps around 0d F down to around -15d F during a recent cold snap,fuel economy was down to around 5 mpg. When ambient temps increased to around 30d F average,fuel economy improved by almost 3 mpg. A 60% improvement from just an increase in ambient air temps and the throttle icing issues went away as well.
I'm guessing when I find a stock air cleaner setup,fuel economy and driveability in general will improve greatly. As I said before,it would be beneficial to add an mat sensor,but in this instance,you're trying to tune around what amounts to a mechanical issue. My 0.02 cents

[woody80z28]

Do you know of anyone who has made a heat pipe work with headers? I'm open to trying that out for a winter solution, but my heat pipe was already gone on my truck and my parts truck...so I'm a little in the dark on what I'd have to fabricate.

Anyone have pics of a stock thermac or one made to work with headers?

[EagleMark]

Just find a stock GM air cleaner for your car/truck and grab the cold air tube too! Then look at Summit Racing for the part to clamp on headers for hot air.

[PJG1173]

I would imagine you could just wrap a sheet of aluminum around a couple primarys with some sort of bung to attach the heat tube to.

[EagleMark]

That's basically what they sell...

[93V8S10]

When I had this on my truck, I just made my own, wasn't hard to do. Unfortunately, I don't have any pictures. Doesn't have to be fancy, unless you want it to be, it would work even if you just stuffed the heat pipe in between a couple of tubes.

[gregs78cam]

I have thought about making a heatshield to go around the headers similar to the new LS exhaust system, it wouldn't be hard to then duct it up the air filter.

[woody80z28]

This is about the best I've found...which is nothing special from what I can see. It will only take air off one tube...will it be enough to actually do anything?

http://www.summitracing.com/parts/HED-24510/
http://static.summitracing.com/global/images/prod/large/hed-24510_w.jpg

[EagleMark]

Yes! It will! Done that been there! :thumbsup:

I have also seen shields made like Greg described which get heat from 2 to 4 cylinders. Don't know if they were made or aftermarket. More heat more better, the valve will just close or half close sooner. More heat more better at highway speeds to as air blowing by headers is not only cooling air coming in it is blowing it by the hot air intake tube.

When I used one like you pictured I pointed it back, so air from fan or air at highway speed blew hot air in tube instead of, like being striaght up fan air or highway air would blow hot air past it.

You will notice a difference in how engine runs when cold within 1 minute of starting a cold engine. Think about how long you could hold your hand on a header tube when engine was started...

For summer time you can just block it off? But I have checked mine and it is always closed when warm. Pretty slick the new ones are with no vacuum hoses or thermac valve in air cleaner needed. But they still work well, just more stuff. If you look at older chevy trucks you will see they have one with vacuum hoses and thermac valve inside air cleaner. Newer, like my 1987 and 1990 Chevy trucks had the new flapper with thermac valve built in (no vacuum hoses).

[woody80z28]

Ok. I have two stock air cleaner housings so one of them should still have a good thermac on it. I'll have to modify my TBi studs a little to make it work, but that should be easy. Or wasn't there a single stud lid for early TBI trucks? That would be even better.

[907 Chevy]

EagleMark is right on the money. I just tracked down a stock aircleaner and installed it yesterday. Driveability is much better and the engine warms up much faster. I don't have a pipe attached to a header tube right now so I just have the heat riser tube sitting on top of a header tube. It'll have to work for the time being.
It'll be a couple weeks before I'll see if any fuel economy gains were realized as a result,but the swap has already proved worthwhile for me.

It's my understanding that the thermac valve is basically just a thermostat,is it not? It seems that its designed to keep a constant temperature of air entering the engine by either taking in warmer air off the manifold or cooler air off the fender to add to the mix depending on the temp of air flowing over the temperature sensing element.

If so,it seems running a stock setup would make tuning VE much more predictable and easier by keeping a constant temp(density) of air entering the manifold.

I'm pretty positive that if I put an 02 sensor in every header primary and watched the AFR values while the engine idled on a cold day without any sort of air preheater,I'd see wildly fluctuating AFR values between cylinders as a result of poor vaporization,fuel falling out of suspension,and fuel puddling in the intake.
Before adding the stock intake my truck smelled uber rich at cold start idle and even warm idle. I think the reason was that there was raw fuel literally running into the cylinders and getting blown out the exhaust. If anything,most of the cylinders were probably running lean as a result.

[EagleMark]

That's how it works. Where your at has a lot to do with how well it works too! I had a 1228746 $61 system on a Scout. It is from a Caprice and the Camaro of those years used it too. It was basically a 1227747 with IAT and you could see temps changing. I watched the valve and it was closed at cold start, open when hot in summer and you could see it in the middle sometimes too blending cold and warm air!

Glad someone listens to me and tried it! :thumbsup:

[woody80z28]

So, I've been super busy lately and haven't even had a chance to do the MAT or heat riser on the truck yet. I have noticed as ambient temps have increased that the truck runs much better! It's an animal now...the throttle response is much more crisp! So by this fall you can bet that I'll have this done for when colder weather arrives. I've always assumed colder air was always better (magazines will brainwash you of this)...but in this application that is definitely wrong.

[jameslleary]

I was under the same impression, until I started reading about the projects that Smokey Yunik was doing.

[EagleMark]

Been a long time since I read that, wonder if a kit or manufacturer has ever used it?

http://www.circletrack.com/enginetech/ctrp_1004_pontiac_fiero_hot_air_engine/viewall.html

[jameslleary]

Been a long time since I read that, wonder if a kit or manufacturer has ever used it?

http://www.circletrack.com/enginetech/ctrp_1004_pontiac_fiero_hot_air_engine/viewall.htmlThey are probably afraid to try it. If "Big Oil" found out there was a kit out there, I can almost guarantee that all 50 states would be subject to California Smog regualations real soon. Cant have a 3 ton Burb getting 32 mpg now, can we!?

[woody80z28]

Interesting read...and it does make some sense. With the emergence of port injection and higher fuel pressures I wonder how much we have gained back.

[EagleMark]

Just a guess that big oil would buy all patent rights to put on a shelf?

Does not work with port injection... so gains there did not address this theory?

[woody80z28]

Resurrecting this thread from the depths of the board. I have my Beretta apart in pieces right now, but the truck will finally get a MAT this summer. I've been running a stock air cleaner with the thermac already and it has helped some, but a MAT will definitely be an improvement.

[JeepsAndGuns]

Not sure if you read this thread or not, but I ended up adding one to my $0D MPFI system with pretty good results.
Not sure what page I started talking about a MAT, but I think its more twards the end.
http://www.gearhead-efi.com/Fuel-Injection/showthread.php?1317-All-O2-sensors-created-equal

[EagleMark]

Resurrecting this thread from the depths of the board. I have my Beretta apart in pieces right now, but the truck will finally get a MAT this summer. I've been running a stock air cleaner with the thermac already and it has helped some, but a MAT will definitely be an improvement.When you hook up the MAT, enable the MAT, fill in MAT tables, spark bias from a CPI bin because it's the only one that had MAT. Make sure you don't loose 10 degrees timing in Main Spark Table! For some reason on one I am working on when MAT was added, it added Main Spark Bias and Altitude Spark Bias to Main Spark Table? This was MPFI. Not sure if it will do same on TBI...

[woody80z28]

I dont have any spark bias in my BIN. Can I just zero out the MAT spark table? Maybe add a couple when really cold.