Hey everyone. Ive seen a couple threads like this before...but not exactly the same. I was going to put my PCM inside...but couldnt decide where to make the hole, or how to mount the PCM under the dash. Cant seem to find any pics of how people positioned it under the dash.

With my "unique" solution for keeping the A/C, I have a pretty neat little space for it next to the pass. side fender. Ive seen it in this area before...but usually up further. If I use this spot, with the LTs, will I meltdown the PCM??? Here is a pic.





I was thinkin of building a small shield for it... Maybe out of aluminum, and possible put some heat barrier insulation on the inside. The only thing I thought with that was maybe it wouldnt allow air to flow around the PCM...and Im not sure if that will mess up its heat sink properties...

Any ideas or suggestions?? Its pretty close to the headers...but this is the only clean place to put it besides inside the car. And with the limited amount of info on doing that, I dont think Ill be going that route. I think there are a few of Mr Dude's pics of the location for the running the wires inside...but I remember it being a pretty vauge picture. Thanks in advance for any insight!

Justin

 

Im pretty sure the 2004 GTO ECU is in the same spot, except on the driver side. It uses a metal heat sheild. I have not heard of any problems, but 05-06 ECU was moved to the top of the wheelwell.

 

Thanks for the info... I think I definetly better make a shield around it.

Does anyone know how much "open air" space the PCM needs so that it can cool properly??? I dont want to seal it up from the headers only to have it overheat on its own...

Justin

 

How hot can headers get - 1,000 degrees? Higher? I don't believe putting the brains for the engine about an inch away from that much heat can be good for them at all. Solder melts at 460 degrees and many of the parts in the computer will probably go bad at half that temperature. I'd recommend finding a cooler location.

 

I agree... I was just thinking about the solder thing actually. Im starting to not like my spot more and more.

I wish someone could take a pic of how they have it positioned under the dash on a thirdgen. I just dont see where I need to make the hole and how far the wires will reach.

Justin

 

If you relocate it under the dash you will have to extend ALL of the PCM wires. It takes alot of time and patients but definately worth it than having a toasted PCM.

 

1000 degrees? i dont think so.

 

put on top of the wheelwell and it will not get hot.

 

In General, anything Electrical and heat are not a good mix.. Computer are no different.

A sample, Do you have a PC at home or work, The CPU in a PC will slow down it's operation of the PC if it start to overheat... PC and Server have FANS to cool the CPU and it's internal's.

A Auto PCM, ECM, etc is no different, just without any fans. Good cool air flow will help keep the PCM working at it's best. The PCM is well build to handle the vary condition of both Heat and Cold, but what ever you can do to keep the PCM at a good stable operating temp and not at the extereme would help.

I have moved my PCM inside on top of the Trans Tunnel just behind the Firewall, You should have enough Wire to relocate it there.

ECM/PCM will fail, I've had to replace my 84' Z28 ECM twice now in 22 years.

That's my two cents, Good luck.

 

Thanks for the posts guys! Ive heard confirmation that the PCM wires will reach without extensions...but its close. Thats why I wanted to see a pic of how the people who have them inside have them positioned.

I was thinking about putting it on top of the wheel well. I dont have the stock coolant bottle anymore, so its free space.

Im just trying to put it somewhere where it will look clean and be safe. Ive been doing good by keeping things pretty clean under the hood so far, and I just want the PCM to be the same way.

bczee: Do you have a pic or can you tell me alittle better as to where you put your PCM on the tunnel inside??/ I think I have an idea as to where you are talking about...

I looked at the area where mr dude and others have drilled a hole and passed the wires inside. But it looks like ide be drilling right through the inside part of the hvac box. and once iniside, i cant see where the pcm will even remotly tuck up under the dash...

Too bad they dont make plug in extentions for the PCM. So you can plug the C1 and C2 connectors in, then have an extension cord type deal, with the correct C1 & C2 connectors to go into the PCM once inside.

Justin

 

I don't have an picture of it yet.. I only have it mocked up at this point. Got to finish rebuilding the Trans Tunnel (had to hack on it to get the T56 to sit right)

I drilled and use a large Firewall grommet. The hole was almost directly behind and below the MAP Sensor/port. It came out just below the HVAC box. I had to remove he lower directional port (it comes off, 1 screw) and I will be modifing it to only redirect air to the sides and away from the PCM.

I will be building a console to cover the PCM and may have some Gauges, ODBII port and some warning light (and maybe a cup holder or two.. LOL) etc.. ???

I will post later.

 

I've never run EGT probes on gasoline, but on natural gas at 11:1 w/ 6psi boost, I was seeing 1900F. On M85 (methanol) at 12:1 I was barely breaking 1000F. From what I read on the web, normal EGT for gasoline is 1100F-1400F, but it depends on a lot of factors (compression, timing, cam profile...).

 

What car are we talking about here?

how about the space behind the the top shock mount and infront of the firewall? ( assuming you have that space available)

 

True the egt can reach above 1000 degrees, but the surface temp of the header I bet wont get over 400-500 degress f. I have put a infrared heat gun on them before and they dont even come close to 1000 degrees. Just my 2 cents.

 

thank you.

 

That's about what I would expect to see with the car sitting still, unless you're running REAL fast alongside the car.... :-)

I'm sure that a WOT run will get the headers much, much hotter. Highway RPMs will also generate a significant amount of heat. But then even 400-500 degrees is hot enough to worry about.

just my 2 degrees
Mike R.

 

I beg to differ on the highway rpms generating more heat. I do agree that 400 to 500 degrees is to hot for a pcm to be that close to. On the highway you do have airflow across the headers and rpms are usually in the 2000- 2500 range pending. At idle with the car sitting is the only place, obvisouly, that you can put an infrared gun to a header. A egt probe will give you the exhaust gas temp, but wont give you the surface temp. So finding out the surface temp at cruising speeds goes into the file of things we just dont know.

 

Hey guys. Well... I solved my PCM location problem today. Friggin hot outside, so I got as much done as I could without sweating all over the car.

First...I couldnt figure out a place to mount the PCM in the engine bay without doing some hacking on the car or making it look like poop. Here is the PCM trying to fit down by the blower motor...just didnt see this happening.



Ide have to cut that brace for it to not hit the hood.

So... Im mounting it inside. Here are a few pics of the hole I made. I dont think I made it in the same place that others have... I didnt make my hole above the frame rail, I made it more towards the center of the car...





I didnt leave the hole this size...I actually used the hole saw and moved it over about 1/2 inch...and made the hole into an oval. Everything passes through real easy and I know where I can get an oval grommet to fit.

Here is how the PCM sits...right were the original ECM sat..


Here are the C1 and C2 plugs plugged in with the computer in place.. Plenty of slack actually. Right now...the 3 "C" plugs are in through that same hole...Im either going to leave them inside, or lengthen some of the wires and plug them in out in the engine bay.





Finally...here are the wires from the engine bay...Once they are loomed and organized.


Im glad that it actually worked out...I wasnt sure until after I made the huge hole. haha. I kind of eyeballed things up first, and thought it would work that way. Shouldnt have an overheating problem with it inside.

Any questions???

Justin

 

Justin

That is what it is all about, making it work! as we all have different problems and configurations.

Good going.. keep us posted.

 

If you build a heatshield make it out of steel and not AL.

You PCM is packaged as so it has a good transfer of heat into the surrounding enviroment and it is built with componets manufactured to higher standards than the PC. It should be ok as is.