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

 

Since your headers are ceramic coated I wouldn't think it would be a problem mounting it there. These computers withstand alot of heat even mounted under the cowl area in the factory location. I don't want to tell you wrong but on my 98 with the ceramic coated LT's, I can lay my hand on the frame rail right next to the header after a long drive and it'll be cool. They flow heat out of the tailpipe pretty well. I moved my battery to the trunk and mounted my PCM on the passenger side where the battery once sat, I made a aluminum box that covers the PCM in case the car overheats and boils over. It still is open on the far side so the computer can get air, it looks really clean and slick. The wires run right down the frame rail and to the back of the motor. I'd say you'll be fine though because it should get good airflow there and well, there just ain't many places to mount a computer under the hood. Lookin good BTW

 

Hey man thanks for the info and the compliment. Things are moving along good. Rear suspension and brakes are buttoned up.

My headers arent ceramic coated. They are the stainless steel headers from hawks. I wish I could move the PCM foward some, but because of my A/C set up, the drier is right there... Like it is in the 4th gen.

This may see overboard...but I wonder if I built an aluminum cover, put heat insulation in it, and mounted a small 12v fan to vent air from the PCM space out towards the motor. That would cause it to suck cooler air from the open side of the PCM gaurd. I have plenty of 12v fans from PCs laying around.

Now that I think about it..that sounds really overboard. I guess today Ill look at putting it inside again. I wish I would have lengthened the wires back when I thought about doing it. haha.

Justin

 

were about to install my pcm under the dash, should have pictures this weekend.

 

Under the passenger side of the dash? are you extending wires? If you can get some pics to me that would be great!!! Once I located my PCM I can finally start to clean up the wiring more and get to hooking things up.

Justin

 

im not 100% sure if we have to extend the wires or not... the wiring is a mrdude1 project.

 

I remember you telling me they are stainless now, I can't remember anything anymore! Guess I'm getting alzheimers. Let me know if you are able to mount it inside the car, I was wanting to do that myself but the wires weren't long enough for me and I wasn't about to start hacking and slicing wires. If I was a little more electically inclined then I might but I'm not the worlds greatest at it. Your getting it done fairly quick, let me know how the car drives with that beast of a motor tucked in there! I just finished up the fuel lines and installing the 4th gen rear this past week, got the new spohn LCA's, Panhard rod and Koni shocks out back. All I have left is finding a transmission and the little bit of wiring, oh and the battery is mounted in the trunk now with a painless power shutoff. Thank goodness for someone here telling me to run a constant hot wire to the computer while the ignition wiring stays on the kill switch, it worked out great.

 

Yeah its comin together fairly easy. I dont get to work on it during the weekend... just during the evenings after work. So its taking longer than I want. All I have to do is run a brake line to the back...and Im done with the rear of the car.

Im feeling adventurous, so I might cut the PCM wires and extend them about a foot..maybe more. I have plenty of left over wire from cleaning up the harness, so I might even be able to keep the colors matched up. Thats going to take a while tho... Cut, strip ends, solder, heat sink, repeat 50 times. haha.

Im using some of the body harness from the 4th gen. Mainly the two fuse blocks. Im doing this more or less for the fan relays, fuel pump relays, a/c relay, and to have some fuses for my line lock and other little things. So...Im hoping that when I hook power to the fuse blocks, and send a "key on" signal to the IGN relay, that all my little pink wires that need switched 12v will get what they need, and the car will start.

Im still keeping my fingers crossed that the previous owner disabled VATS so that it will start. He did it with HP tuners while I was watching and it looked right.

Dont worry..when it does run and drive, Ill post up. Maybe do a vid or two. Seeing other people's finished cars motivates me quite a bit...so maybe my posting will too.

Justin

 

I had mine mounted there (ls1 + hawk lt's).. it got freakin hot drivin around town.. i had it sheilded as well.. i then moved it back by the blower motor.. it did work.. for how long it woulda worked at those temps i couldnt tell ya...

ill grab some pics.. maybe you can make it work there with a/c.. unsure

 

 

is your heater box modified at all or is that stock? My heater box sticks way out there, almost to the strut tower with the A/C equipment.

 

He has the A/C delete box... which is why I think that may not work for me... He is missing the part of the box that houses the evaporator for the A/C system.

This is where my car is different. I have half a 3rd gen box, and half a 4th gen box... I havent had it all together and in the car yet to see if the PCM will fit over there. But I dont want to totally assemble the HVAC box, find out the PCM wont fit like I want it to, then have to take the whole HVAC box back out to try to fish things inside. Im trying to do it once and once only. haha...which so far hasnt worked out all that great.

I think Ive abandoned the idea of putting the PCM that close to the headers though. Ide rather put it inside... But that looks to be like quite a task. I gotta go away for the weekend, but when I get back the first thing Im doing is figuring out the PCM location...even if it takes me all day. haha. Worse comes to worse Ill break out the solder gun and heat shrink and get to extending.

Justin

 

I remember reading that the PCM can mount under the dash without extending the wires. The hole has to be bored right against the framerail under the a/c condenser. The wires are just long enough for it to reach.

I had my LT1 PCM mounted in the same place and tossed that idea for two reasons, one it did get hot there and two, I had no way to run my a/c lines to the evaporator with it in the way.

 

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

 

Looks great man, you really are on the right track with that car! I have been modding my 98 Z-28 this past two weeks so I haven't had time to finish my 87 but hopefully by next spring I will. I did manage to stretch the wires through the passenger side fender and through the kick panel so I will be mounting my computer inside as well. I just feel safer doing it that way. Looks great and keep us informed!


Mike

 

I believe the idea of going above the frame rail was to keep water out, if you went in the frame rail water will get in and that is baad.

The link below has some pics from where I moved my PCM inside.

https://www.thirdgen.org/forums/show...5&postcount=13

 

Here are some pics I took of where I mounted mine.. It definitely looks much better with the PCM inside and hidden away.

 

Great pics dingle! Not many pics like that floating around... I got my car running, and the wires loomed and in place. I ended up extending the wires for the plugs that belong outside the car... The PCM will still sit in the factory location...I think. I kind of like how yours sits... Makes the wires tuck nicer. I have to see how my underdash panel will sit if I try to do it my way. I think the bundle of wires running under the HVAC box will protrude down too far...but we'll see. Im getting close to dealing with that now...

Justin

 

Well I tried to get mine to the factory ECM location but I was about an inch too short and I was not liking the idea of extending some of the harness (where mine is at, NO wires were lengthend from the stock 99 harness, we actually had to shorten maybe 10 or so because they were obscenely long). This spot worked out pretty well it only took me maybe 30 minutes to mount it. That's including making the aluminum strap and drilling the holes. I'm thinking of a way to coverup the small ammount of wire showing from the back of the PCM. I will keep you posted.

 

this post just made my day. Thanks for the great pics of the PCM reaching the stock location