How is the MAT relocated?
How is the IAC bypassed?
What will this do for my car?

Thanks, Doug

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'91 Z28 - 50,000 miles. All power options leather. 350 TPI:
K&N; Fastchip; Airfoil; Custom 'Ram-Air'; SLP Headers; Slp Runners; Borla Catback 50% open; Dual factory Cats; Poweraid TB spacer; March underdrive pulleys; Accel Extreme 9000 wires, Accel coil; Hypertech rotor & cap; NGK platinum plugs; manual fan switch; TB coolant bypass; Pirelli P7000 Z245/50/R16 all season tires; Energy suspention motor mounts; smog pump delete.
S Cobra Radar Detector; Z28 SS Floormats

 

The MAT is bypassed by removing the sensor from the plenum, and physically locating it in a cooler place. You'll have to plug the hole with something.

The IAC can be eliminated by buying a 4.7k ohm resistor at Radio Shack, it tells the ECM that the incoming air is 58 degrees all the time, you gain a little more timing, I heard once that it's good for 2 HP.

I've been running the resistor on my RS for years with no problems

 

So you cut the wires to the IAC and place a 4.7k resistor between the wires, but should you remove the IAC or jsut leave it in the throttle body?

Has anyone seen the TPIS MAT relocation kit? Is it worth the price? ($30) or is it easier to just do it myself? What should the hole be plugged with?

Thanks, Doug

 

You don't even have to cut the IAC wires.

You just unplug the weatherpak connector and shove the resistor into the contacts.

The MAT relocation, I'm not real familiar with, but I'm 99% sure it's just a male and female weatherpak connector and some long wire..

 

So on the MAT will i want the coolest reading possible for the most power?

 

top

 

Ummm....Just a little cleaification of terms here.

I think it's the IAT that you are talking about bypassing. Inlet Air Temperature sensor.

The IAC is the little stepper motor that controls the idle speed, called the Idle Air Control valve.

The MAT snesor is the Manifold Air Temperature sensors. I believe the MAT is what they call it when it is in the plenum (TPI cars), and IAT when in the air inlet hose, or air cleaner assembly (TBI cars)

I hope I'm not right on anything here to add to the confusion!

------------------
Working on:
'84 Z28 LG4 305 with 200,000 original miles!
Added dual elec fans.
145 MPH IROC Speedo
Building 430 HP 350 (ZZ430)
using primarily GMPP parts.
Short block sitting on a stand. (Man, those Fast-Burn heads sitting on it look good!)

Starting to look like the Kicker poster child!

ASE Certified Master Tech

 

ROFLMFAO - bypass the IAC. Bwahahahah hahaha hahaha.

The IAC (Idle Air Control Motor) is what controls your car's idle and stall saver functions. LOL.

Tim

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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

 

Regarding the MAT/IACT relocation, I suggest picking up the TPIS relocation kit. It includes the newer MAT/IAT along with an extended harness. You then leave your old MAT/IAT in the plenum (to avoid a vacuum leak) and disconnect it at the harness (NOT the MAT/IAT itself..its a bitch to get at and reconnect if you decide to reuse it).

By just swapping at the harness, it takes less than a minute to swap between the two. I will tell you that if you live in a climate where there is a great difference in temperature between summer and winter, that the relocated MAT WILL cause you to run too rich.

Until I adjusted my eprom's MAT Inverse Look UP tables, I found it better to run the stock MAT/IAT during winter and the relocated during the summer. Now that I've adjusted the eprom, I run the relocated all year round.

As for the 4.7K resistor in the harness....DON'T DO IT. It causes more problems than it cures. You will loose a valuable piece of information for the ecm and run too lean in winter and too rich in summer @ WOT. If the MAT was unneccessary (which the 4.7K resistor suggests), then GM would have NEVER put one in. The 4.7K resistor trick is one of the worst mods going. You will also have driveability problems even at part throttle when in closed loop. Your BLMs/INTs will be way off (except when the temperature is around 60*).

 

Doh! I'm retarded, IAC, IAT, lol, they're all the same

Thats what happens when you have too much on your mind.

I wasn't sure about the MAT/IAT thing, TBI just has an IAT, that's what I'm used too.

 

MAT is the proper technical term in my 1991 GM Shop Manual for my TPI car. They never even use the phrase "IAT".

Either this is an older term or for a different engine. I don't get hung up on the terms like others do. MAT = IAT as far as I'm concerned.

 

I just did my TBI engine swap and I replaced the CTS. Car parts gave me the wrong sensor, it was the "IAT" (on box) for TPI cars. It looks exactly like the TBI CTS but has different resistance at different temps. So IAT is still being used by part stores and it's also the term they use in my Chiltons manual (was good for only 2 out of 13 reference questions during engine swap).

------------------
, Jon (350 TBI! getting 23mpg highway)
91 Red RS w/grey int, sq stereo (Alpine v12, kicker solo, MB quart premium etc)

• Holley 670 TB unit w/ 1/2" spacer/adapter
• Edelbrock RPM vortec intake
• 350ho 330hp vortec crate motor
• 8" harm. balancer
• Stewart stage 2 water pump w/160 thermo
• SLP tri-y headers to full 3"
• Rebuilt trans w/ SLP shift kit
• Centerline 16x8's all around
• 36/24 mm sway bars
• Full poly bushings, even motor mounts
• SLP LCA and panhard
• Alston SFCs
• Edelbrock 3 point STB
• Global west steering brace aka wonderbar
• Eibach pro kit springs
• Bilstien high perf. struts and shocks
• All this and I still have AC

My websiteAny questions?

 

Same here, Glenn- my '86 GM Book always references the MAT. AFAIK, the "IAT" term started with the 4th gen f-bodies.

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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

JP, not to be a bad guy, but I don't consider Chilton's a manual. 20 years ago I learnt that Chilton's (and Haynes) leave a lot to be desired. GM Shop Manual is the ONLY way to go.

 

Well, thanks for everything guys. I think i'll just leave everything alone for now. Doug

 

Considering I'm a poor college kid....the Chiltons IS the only manual right now in my life . Like I said before, it was 2 for 13, kind of pathetic I know but that is what this site is for. I ask a guestion, you guys look in your manuals or what have you...and I get a free answer!
By the way, Chiltons did make it clear that the TPI IAT looks the same as the TBI CTS and then showed why they were different.

------------------
, Jon (350 TBI! getting 23mpg highway)
91 Red RS w/grey int, sq stereo (Alpine v12, kicker solo, MB quart premium etc)

• Holley 670 TB unit w/ 1/2" spacer/adapter
• Edelbrock RPM vortec intake
• 350ho 330hp vortec crate motor
• 8" harm. balancer
• Stewart stage 2 water pump w/160 thermo
• SLP tri-y headers to full 3"
• Rebuilt trans w/ SLP shift kit
• Centerline 16x8's all around
• 36/24 mm sway bars
• Full poly bushings, even motor mounts
• SLP LCA and panhard
• Alston SFCs
• Edelbrock 3 point STB
• Global west steering brace aka wonderbar
• Eibach pro kit springs
• Bilstien high perf. struts and shocks
• All this and I still have AC

My websiteAny questions?

 

JP, my bitch with those books are that when you get into anything REAL technical, they always say "Consult your manufacturer's Shop Manual".

The worst the GM Shop Manual does is say "Using special tool J######".

But MAT is the proper GM term. Even the error codes (for high MAT or low MAT refers to it as an MAT for all cars, not IAT). The only thing part that GM seems to use "multiple terms" is the memcal/calpak. The GM shop manual switches between those terms constantly. For a while I thought GM might have meant the memcal = eprom and calpak = the eprom plus the ESC circuitry, but they appear to use memcal interchangeably with calpak.

This is probably the only part of the manual that says "Consult your local GM dealer" when it talks about a problem with the memcal. Guess they didn't want to discuss the eprom code.

[This message has been edited by Glenn91L98GTA (edited April 05, 2001).]

 

MAT stand for Manifold Absolute temperature right?

TBI's "MAT" is located in the air cleaner.

IAT, Intake Air Temperature.

CTS, is the coolant temperature sensor, not even close to the same as an IAT or MAT..

Not saying you are wrong, just saying I might be right

 

MAT means "Manifold Air Temperature". You are confusing it with MAP which is Manifold Absolute Pressure, which is the "inverse compliment" of engine vacuum, ie. at Sea Level WOT = .5" Hg of Vacuum and 29.5" Hg MAP and vice versa under severe deceleration (though you cannot hit 29.5" Hg Vacuum/.5" Hg MAP).

 

Well, I'm getting out of this before I make myself look worse

I was close enough, I know what it does.

 

Yes Mac, you do know what the part is and I have grown to accept the IAT and MAT as meaning the same thing, which is the important part.

Glad you didn't confuse it with the IAC. Far too much "alphabet soup" with cars today. FYI, GM seems to spell "gauge" as "gage". Don't ask me why on that one.