1G Relocate power transistor to inside cabin?

[We're on Boost]

I'm thinking about relocating my power transistor (PTU) to someplace inside the cabin, probably in the passenger footwell. Can anybody think of a reason not to do this?

It would be only a few inches from the ecu, but the 2 wires that go from the PTU to the coil would be a lot longer, maybe 5 or 6 feet long.

It would never get very hot. Does this thing need some temperature to make its full output? (current gain vs temperature, or whatever).

I'm replacing my old PTU anyway - it seems to have that failure mode where it quits when it gets hot. I'm using the regular 1990 stuff - 5 pin connector on the PTU and 4 pin connector on the coil.

 

[92AWDHX40]

It's been done before it can go anywhere in the cabin. Under the radio.

 

[We're on Boost]

It's been done before it can go anywhere in the cabin. Under the radio.

And there we have it! New power transistor in the cabin, under the center stack.
New connectors on the PTU and the coil, and all new wiring between ecu, PTU, and coil.

The old wires from ecu #109 and #110 are still there, they just don't connect to the coil pack anymore. I left them there to preserve their connection to the ignition switch, the MPI relay, and the 1990 tach filter. The wires that actually go all the way from ecu to PTU and coil pack are all new. That idea I checked out with 19Eclipse90. It all works!

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[luv2rallye]

Any radio static from that new 5-6' broadcasting antenna?

 

[We're on Boost]

Any radio static from that new 5-6' broadcasting antenna?

I don't know, if anybody pulls up next to me at a stop light maybe I'll ask them!
Oh wait, I do have a 2000 BMW with a radio. So I guess I could test it myself.
Anyway, there's no radio in this car. Would you expect that the car next to me would get some radio static?
BTW I'm a fan of your PTU test article which is one of the clues I had that my old PTU might be what was causing my car to quit running about 15 minutes after startup.

 

[luv2rallye]

Probably would only hear it in your radio (through car's wiring).

Thanx for the kudos - I never hear back from anyone on my articles. The 2g PTU backing should be bolted (and electrically conductive) to a heavy ground (intake manifold on a 2g) to act as a heat sink (also provide a heavier ground then the smaller connector wires ground, although it can flow through there also). Don't know about the 1g (haven't seen one). You may want to consider if it needs to be mounted to heavy metal to act as a heat sink if the stock location is, especially on hot summer days (or you may get more heating up failures).

 

[We're on Boost]

You may want to consider if it needs to be mounted to heavy metal to act as a heat sink if the stock location is, especially on hot summer days (or you may get more heating up failures).

Are you saying that where I have it mounted it might need more heat sink? Or is it just in the engine bay that it needs heat sink because of the high ambient temps?
I have a Milwaukee infrared temp gun that I can use to check temps on it while I'm in the car. So I guess I'll make that part of my normal procedure for a while.
I really like that thick steel base plate that the plastic module is screwed onto, and I have the steel plate bolted to the hanger like thing that's made out of 1/8" thick aluminum, which goes vertically to that slot where it bolts to the center stack sheet metal with a 6mm bolt.
The ground wire is that white wire with green heat shrink on the end with a ring connector with a 5mm bolt through it to some extremely clean internal threads that were there just waiting for me after I took the OEM screw out. That is near the top of the picture.
The ground wire at the PTU is blue but that is just a pigtail. The rest of the ground wire is white.
Here's a cropped pic that shows these things better, with the white ground wire ending near the upper right corner of the pic. If you make this go full size it gives you a good look at it.

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[luv2rallye]

You may be fine as others have moved it inside and claim no problems. You'll never know until you have run it awhile which heats the PTU up (from the high coil primary current flowing through it). You can feel its heat with your finger while engine is running. And of course a hot engine bay contributes to make it worse. However a poor quality PTU brand is what I'VE ALWAYS SEEN TO BE THE SOURCE OF FAILURE. Think about it - any PTU must be designed to operate under ALL THAT HEAT from EVERYWHERE! Change to a better quality brand (like a factory one) and I've always seen PTU heat problems go away. Just something to be aware of should you start getting similiar heat ignition problems like what you had. As I said I've never seen a 1g PTU so I haven't seen how it's mounted. I wouldn't worry about now however until any problems start happening.

 

[We're on Boost]

Ok that's good stuff to know. I'll keep an eye (a lens) on the temp and I'm thinking now about attaching more heat sink to it. I have a good selection of 1/8" and 1/16" thick aluminum flat sheet, and some 3/16" thick aluminum angle. The steel plate that the plastic module is on has 3 attach holes which I am only using one right now. I could attach some aluminum to the other 2 holes. I have a few retired CPU heat sinks too.

The power transistor quality - I'm hoping that the one I got is actually one of those same-as-OEM in a different box things. It's beautiful. It says "Mitsubishi" on the plastic module, "MD127742" on the steel plate, and "Made in Japan" on the box. It's an "Intermotor" brand (Standard Motor Products) from Rock Auto. Take a look! Now that I think about it, JNZ probably has a "white box" item for this part.

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[luv2rallye]

Well it says Mitsubishi on it and has a MDxxxxxx part number which is good.

What year, model, engine size, turbo/not do you have because I don't recognize that part number for a 1990 turbo. [Mitsubishi's ASA database 1g 2.0 turbo lists MD126461 for up to year 90.06.1 and MD158956 for years 90.06.2 - 94.05.1. But maybe you have a different engine?].

 

[We're on Boost]

Oh man, my engine is so far from stock ....... it is a 6-bolt that was built by English Racing in 2015-2016. From what I've seen they have stuck with 1990 sensors and electrical stuff. Most of that stuff they put on new but the coil pack and the power transistor they used were not new, I think they were the ones they took off of my old engine. My ECU for sure is a 1990. It's the one that was in the car originally. My "Specs and Photos" in the profile you get from the left thumbnail is most of what I know about the engine.

I don't know how to access the ASA database so I never look there. But I look at the website for mitsu dealers like Mitsubishi Parts Now (or Capitol City Mitsubishi). And there I get MD127742 for the 1990 Eclipse GSX. Here's what their web page for it looks like right now (2 shots):

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[luv2rallye]

Sounds like you should be fine.

 

[19Eclipse90]

Well it says Mitsubishi on it and has a MDxxxxxx part number which is good.

What year, model, engine size, turbo/not do you have because I don't recognize that part number for a 1990 turbo. [Mitsubishi's ASA database 1g 2.0 turbo lists MD126461 for up to year 90.06.1 and MD158956 for years 90.06.2 - 94.05.1. But maybe you have a different engine?].

Those are coil pack part numbers.

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Here's the PTU:

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[1990TSIAWDTALON]

Mount that PTU in the heater duct so you have a heater again
JK, the metal bracket that the PTU is mounted too should be sufficient heat transfer to keep it cool. Of course if you can dissipate more with an aluminum plate or such, its just that much easier on the component. A dab of themal heat paste between them is also good.
I like the idea!

 

[luv2rallye]

Those are coil pack part numbers.

Ha, ha, my old age is interfering. Yes I clicked on the wrong item. Thanx for pointing that out.

 

[We're on Boost]

Ha, ha, my old age is interfering. Yes I clicked on the wrong item. Thanx for pointing that out.

Thanks for all the input though, which is what I wanted in this thread since I wasn't too sure what all would happen!
And thanks @iugrad92turbo @19Eclipse90 and @1990TSIAWDTALON
With @19Eclipse90 I had PMs that went, 28 posts I think ? about the wiring just to make sure that I wasn't going to seriously screw anything up.
Along the way with that he helped me look for my 1990 tach filter which I had never even seen, and we found it! And I was able to fish it out from where it was hiding without taking half the car apart, and made up a sturdy ground wire for it (it wasn't attached to anything!) connecting the module case to the firewall.

So all in all it was a heck of a deal haha!

In the PMs with Brian, we started out by looking at this schematic of what I wanted to do with the wires that come from #109 and #110 on the ECU. I showed in red the new wires I wanted to add. The original black wires I showed truncated in the engine bay just before they get to the plugs at the end. This might seem a little weird but the idea was to minimize the amount of work I would have to do under the intake manifold. And it was that downstream end of the old wires that was all hacked up and mangled and needed to be replaced. The rest of the old harness as you go upstream towards the ecu seems good, and my wiring and plugs right into the ECU was all new just a few years ago.

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[1990TSIAWDTALON]

Us 90 guys gotta stick together!!!

 

[ist dwa]

MY PT has been inside my cabin for a decade, it should have been there in the first place, plus it stays much cooler in the cabin.

 

[We're on Boost]

The transistor in the cabin is working out really well!
I'm not getting any kind of misbehavior from the ignition system.
No misfire at any operating condition up to 27 psi of boost on ~E50 which is my normal summer config.

I check it for temperature at the end of every drive, with the engine still running.
I've never shot a temp higher than 92 degrees F on it so far, with the infrared temp shooter. It seems to be staying within about 20 degrees of the ambient temp in the cabin. It only feels warm to the touch, not hot. I haven't added any more heatsink to it. For heat sink it just has the steel plate that it comes on from the factory, plus the 1/8" thick aluminum bar that I bolted the steel plate to, plus the air around it.

I haven't checked if for radio interference yet.

Thanks for the input everyone!