CompanyXPaladin

I don't mean to sound like a complete noob, there a difference between the ECUs or engines in S5's and S4's? I noticed the redline was 8k on the S5 as opposed to 7k on the S4.

In any case, heres my deal: I have an '89 RX7 GTU and an '88 RX7 Convertible. The GTU is a junkyard deal - seized engine. Otherwise, its in near-perfect shape. The Vert is kind of a fixer-upper, and I'm working on it rapidly.

So, I have a couple of questions regarding these two, with the intent of basically using the GTU as a parts *****. (Have already moved the taillights over.) Is the S5 ECU better? Is there any reason to move it to the Vert? If there is, is it a simple hookup? Are there any other parts I should use from the GTU?

Also, I had a lot of slop in the shifter on the Vert.. I decided to get a short shifter and bushings kit for it (ebay special ~$80), and now my transmission makes a hell of a lot of noise when I drive it. It sounds like maybe metal vibrating on metal, or possibly grinding. I am hesitant to drive it. Is it safe to drive that way? What can I do to get rid of the noise?

And finally, what should I do with these cars in your opinion - were you in my shoes, what would you do?

Thanks for all your help and advice!

fluffysheap

The ECU and engine are both different from S4 to S5. The engine has lighter rotors and higher compression, a different intake, as well as an electronic oil metering pump, and the ECU is different. You have to use the metering pump that matches the ECU. The S5 NA rotors are pretty much the "best" rotors out there, but if the engine is damaged, there's no guarantee the rotors are in good shape. You can swap the intake without doing anything special but the ECU and engine should go as a unit. You could rebuild and put the S5 rotors + flywheel and intake with the S4 metering pump + ECU but you wouldn't be able to take full advantage of the extra RPM since you'd get fuel cut.

If you're lucky, there's nothing seriously wrong with the GTU engine. It might just be carbon locked in which case you can probably get it unstuck and it'll be good as new. Or, who knows, maybe it blew a coolant seal and the whole inside is rusted.

Are you sure you have enough oil in your transmission? I'd be looking at "something you might have screwed up while you were working on it" since I don't think just bushings would make it sound really bad. I wouldn't want to drive it with grinding sounds coming out. In a pinch, you can swap it with the GTU transmission, they are mostly compatible.

CompanyXPaladin

How would I go about 'unsticking' the engine? The manufacturer of the short shifter says that this is a known problem, and to fix it I should hammer out the transmission tunnel to make additional room. Thanks for the advice, fluffysheap.

fluffysheap

To unstick seized engine: Squirt some mild solvent, like seafoam or ATF, in the spark plugs, intake ports, anywhere you can get it into the combustion chambers. Let it soak. Using the flywheel teeth (not the flywheel nut or front pulley!) try to turn the engine backwards, then forwards, try to work it loose. Backwards is really the only way but once it starts to move forwards is ok. Eventually it either will come loose or it won't. Definitely no guarantees.