Relocate MAT after performing TB coolant Bypass??
Thread Starter
Racer
Joined: Jun 2017
Posts: 343
Likes: 18
From: Newport News VA
Relocate MAT after performing TB coolant Bypass??
I have an 89 L98 TPI, aluminum heads and mild aftermarket cam. I've been restoring the car and have been working through the engine bay. I noticed how hot the plenum would get during normal idle and quick revs; so I bypassed the coolant around throttle body. Plenum is cool to the touch even after warming up and hitting 4k revs. I also was breaking down the plenum to upgrade the injectors to some Bosch D3s and noticed the PO had removed the MAT sensor and plugged the hole as well as removed the little extension harness. Harness connector is still intact behind the distributor.
So the question is: now that the plenum is not as much of a heat sink, should I just replace the little extension harness and sensor or pop for the relocation kit?? Between buying the extension harness and sensor vs. the relocation kit, its basically the same money. Performance improvement? Thoughts?
So the question is: now that the plenum is not as much of a heat sink, should I just replace the little extension harness and sensor or pop for the relocation kit?? Between buying the extension harness and sensor vs. the relocation kit, its basically the same money. Performance improvement? Thoughts?
Thread Starter
Racer
Joined: Jun 2017
Posts: 343
Likes: 18
From: Newport News VA
I'm just going to replace the stock size extension harness and unplug the MAT sensor hole in the plenum and put a new sensor in there. I can always revisit it later down the road.
I'm curious though, how much does the MAT play in fueling in a MAF car? I see so many posts talking about people removing the MAT since it is "not needed in MAF cars" and that a MAF can tell the CPU everything. Sure a MAF can tell flow, but it cannot tell density of air based on flow alone. The MAT would be needed to get a temp and the computer can extrapolate density of air based on temp and flow. Also other logic, GM wouldn't have put it there unless it had a purpose
Team Owner
Joined: Jul 2004
Posts: 28,357
Likes: 3,253
From: Hartford WI
I have an 89 L98 TPI, aluminum heads and mild aftermarket cam. I've been restoring the car and have been working through the engine bay. I noticed how hot the plenum would get during normal idle and quick revs; so I bypassed the coolant around throttle body. Plenum is cool to the touch even after warming up and hitting 4k revs. I also was breaking down the plenum to upgrade the injectors to some Bosch D3s and noticed the PO had removed the MAT sensor and plugged the hole as well as removed the little extension harness. Harness connector is still intact behind the distributor.
So the question is: now that the plenum is not as much of a heat sink, should I just replace the little extension harness and sensor or pop for the relocation kit?? Between buying the extension harness and sensor vs. the relocation kit, its basically the same money. Performance improvement? Thoughts?
So the question is: now that the plenum is not as much of a heat sink, should I just replace the little extension harness and sensor or pop for the relocation kit?? Between buying the extension harness and sensor vs. the relocation kit, its basically the same money. Performance improvement? Thoughts?
What the PO tried to do is fool the ECM into thinking that it is cooler than it is so the ECM will dump more fuel. Theory is nice but you can gain, and this is the important part, "UP TO X HP". I wouldn't buy that. Up to means anything from negative gains to whatever they promise. Is it worth the hassle of taking it out and doing it again? Doubtful. Save it for the next time you are there. Just remember, it has to work as a system, whatever that system is, be it the stuff GM hands us or a reputable professional that redesigned the system.
Race Director
Joined: Oct 2008
Posts: 17,982
Likes: 1,072
From: Lansing MI
Blocked off coolant passages? I'm sorry, i'm not following. The only thing coolant related was bypassing the throttle body which has made a noticeable difference in engine performance.
I'm just going to replace the stock size extension harness and unplug the MAT sensor hole in the plenum and put a new sensor in there. I can always revisit it later down the road.
I'm curious though, how much does the MAT play in fueling in a MAF car? I see so many posts talking about people removing the MAT since it is "not needed in MAF cars" and that a MAF can tell the CPU everything. Sure a MAF can tell flow, but it cannot tell density of air based on flow alone. The MAT would be needed to get a temp and the computer can extrapolate density of air based on temp and flow. Also other logic, GM wouldn't have put it there unless it had a purpose
I'm just going to replace the stock size extension harness and unplug the MAT sensor hole in the plenum and put a new sensor in there. I can always revisit it later down the road.
I'm curious though, how much does the MAT play in fueling in a MAF car? I see so many posts talking about people removing the MAT since it is "not needed in MAF cars" and that a MAF can tell the CPU everything. Sure a MAF can tell flow, but it cannot tell density of air based on flow alone. The MAT would be needed to get a temp and the computer can extrapolate density of air based on temp and flow. Also other logic, GM wouldn't have put it there unless it had a purpose
MAT doesn't mean much of anything because the ECM/PCM relies so heavily on coolant temp. Air temp is a variable but its almost meaningless.
In spite of this, I would put the sensor back in where it belongs with whatever harness you need. If nothing else I would think it would eliminate a trouble code.
Thread Starter
Racer
Joined: Jun 2017
Posts: 343
Likes: 18
From: Newport News VA
Right now, the issue is that the TB is easier to remove without coolant spills or extra work so bypassing it is a good thing.
What the PO tried to do is fool the ECM into thinking that it is cooler than it is so the ECM will dump more fuel. Theory is nice but you can gain, and this is the important part, "UP TO X HP". I wouldn't buy that. Up to means anything from negative gains to whatever they promise. Is it worth the hassle of taking it out and doing it again? Doubtful. Save it for the next time you are there. Just remember, it has to work as a system, whatever that system is, be it the stuff GM hands us or a reputable professional that redesigned the system.
What the PO tried to do is fool the ECM into thinking that it is cooler than it is so the ECM will dump more fuel. Theory is nice but you can gain, and this is the important part, "UP TO X HP". I wouldn't buy that. Up to means anything from negative gains to whatever they promise. Is it worth the hassle of taking it out and doing it again? Doubtful. Save it for the next time you are there. Just remember, it has to work as a system, whatever that system is, be it the stuff GM hands us or a reputable professional that redesigned the system.
Team Owner
Joined: Jul 2004
Posts: 28,357
Likes: 3,253
From: Hartford WI
Interesting, I hadn't thought about it that way. As always, I appreciate your input, bailing me out as usual. It's no problem getting that plenum off at this point, i've got it down to a science as much as i've been in that intake... I've got a few wires to clean up while i'm in there. PO/engine shop that did the rebuild did a slack job of routing and securing the wiring correctly and a few of them have melted through. I'm beginning to think it was a miracle this thing was running as much as it was.
If you are going in there, practice, practice and practice soldering. Replace the burnt sections with new plugs and solder them on with heat shrink wrap. You'd find getting the plenum off completely is less messy than having coolant spill. Take the TB out and have it cleaned since you are there. Top plate off, IAC off, IAC housing off. Spray gentle mist on the IAC pintle and wipe off GENTLY. NO PUSHING. Reinstall with fresh gaskets.
https://www.tpis.com/parts/view/27
Team Owner
Joined: Jul 2004
Posts: 28,357
Likes: 3,253
From: Hartford WI
https://www.corvetteforum.com/forums...post1596109052
That hose could be replaced too from what he is saying.
That hose could be replaced too from what he is saying.
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