Thanks to Steven, I managed to get ahold of a 3.1L Turbo engine from a 1990 Turbo Grand Prix. If you haven't heard of it, that's cuz only a few thousand or less were made in the couple years they were built, they're quite a rare find - especially in a Pick-N-Pull half price sale weekend!! We pulled the whole engine, intercooler and piping, transmission, complete wiring harness, and ECM for 279 bucks. Score! The oil and fluids looked very fresh and I didn't see any metal bits, and the axles in the tranny turned without any strange noises or behavior, so we'll see.

This engine has several things that set it apart from the millions of ordinary 3.1s, such as a special block casting using a high nickel/tin alloy (probably 2% nickel for strength, and 1% tin to improve pouring characteristics during casting, like SBC HP blocks, not the 20% that has been stated). It also supposedly has a tough crank casting that's also nitrided as well. The plenum is obviously unique to the application, and the most obvious part is the turbo system that comes with it. It's not the most efficient turbo setup, nor the most powerful, but will form the basis of a California smog legal turbo V6 engine swap into my 86 2m4 automatic. Once through BAR inspection, I may later swap in a 3400 in it's place with a custom turbo setup with a much more efficient, larger turbo. The possibilities are endless.






California legal turbo V6 engine swap!



No, that isn't my hand. One of the things I realized, is that the style and location of the stock engine mounts looks very close to the mounts in my 86 4 cyl automatic, for which this drivetrain is destined. Could it be possible that with the right mounts, this thing could drop into my stock cradle? I'm not a big fan of the wimpy 2 point and a dogbone mounting system on my stock duke, so some extra reinforcements will be needed, but that'd be a nice start.


Intercooler and some of the piping.


The transmission is supposedly a 440T4 aka 4T60 non E, heavy duty. It's unique to this engine in a couple ways, including the vacuum modulator being designed to operate properly with boost. It's non E, so dropping in a 4T65HD may be a challenge without a solution for transmission control since this ECM doesn't have that functionality. A manual tranny would be too easy, though.

I already have my hands full with a 3.4L DOHC swap into my 87GT, but progress is coming along. Once it's done and good to go, I'll start work on this beast! Gonna be sweet.

Nice find. Great price. I'd a been all over that one. If you can will you get some or post some turbo measurments for us? There are quite a few 3.1/3.4's out here that would love to know the details. Oh and I think a build thread is manditory in this one.

I agree, a build thread would be very good. You might be stuck with that trans though because the shift cables on the manuals are right where the turbo is located.

The cool thing is the crossover. If one could get the exhaust manifolds and crossover new it would make for an instant turbo manifold with no fabrication work needed.

Could I ask for a pic of the turbine side of the GT25? I am curious how the exhaust is routed.

That turbo has a water-cooled center section? Very nice.

[This message has been edited by Hudini (edited 08-26-2007).]

You should easily be able to bolt the drivetrain in the 84-87 cradle. The block should have the front bosses for the "L" bracket, I don't recall but either, one of the 3 spd tranny mounts will work or both of the four speed mounts from an earlier model four speed that mounts to the cradle the way the Fiero 3 speed does unless some of the mount holes have been removed from that particular transmission that were present on the earlier trannies.

That itty bitty T25 or whatever it is shouldn't be difficult to swap out for the larger T3 with minimal fabrication possibly by welding a T3 flange to the one on the crossover. That particular turbo is not much bigger than the one found on the old 2.0 turbo Sunbird so you would gain a lot with the upgrade. Then you can remove the CalPak from the ECM and install it in a 730 ECM which will fit the Fiero harness plugs and save a lot of room over the four plug 727 that came with the engine. Ryan has an excellent thread on converting to the 730 ECM already. You have to wire it for a ~91 V6 engine that uses the 730 ecm so installing the chip will work properly. I'll have to check but to confirm it but I believe that's what I was told for my project. I started with the 727 which is about 98% complete but intend to start over with another Fiero harness and the 730 ECM.

I believe it's much easier to start with the Fiero harness and add any missing extra wires.

my daughter has a'90 turbo gp. they made approx 7000 '89-'90 model years the cross over is famous for getting cracks , look on tgp forums(turbo grand prix) for lots of info on improving the power output. it has been a very trouble free car 107,000 miles and it can get almost 27mpg on hi way. it is not super fast but a lot better than stock 3.1

a 4t65e-hd would be a fairly easy swap, a transmission controler is not hard to make out of a stock 3800 PCM, as it doesnt really need to know that much about the motor to shift the trans.

quote Originally posted by darkhorizon: a 4t65e-hd would be a fairly easy swap, a transmission controler is not hard to make out of a stock 3800 PCM, as it doesnt really need to know that much about the motor to shift the trans.

Interesting, it must use rpm, mph, MAP and TPS input to shift at the appropriate time.

quote Originally posted by darkhorizon: a 4t65e-hd would be a fairly easy swap, a transmission controler is not hard to make out of a stock 3800 PCM, as it doesnt really need to know that much about the motor to shift the trans.

Does anybody have a schematic for this or does anyone on the forum do this mod? I haven't seen anything about this on any threads in my search.

I have my reasons not to use another ECM just to run the transmission unless it's a small, purpose built unit, but those are expensive. I do wonder though if one could properly run the TGP code on another ECM that will also control a 4T65E? For now, if this 440T4 works, I'll probaby run the entire setup completely stock to get California BAR approval, then start modifying things later.

Does anybody know of any inexpensive aftermarket electronic transmission controllers? How about the possibility of running the TGP code, and adding transmission control to another similar ECM? What about all the new transmission and engine control modules that are used on recent GM vehicles?