1990 rx7 motor swap
 

So I need help, I have a series 5 shell. That's the car I plan to use, it's a 1990 rx7 convertible. I bought a series 4 motor running from an 88 convertible. I just need to know if I can use to series 4 ecu and wiring harness to do the swap. Or do I need to get series 5 wiring harness and ecu?

I should think you'd want the harness/ecu that matches the engine.

Correct, you will need to reuse all your intakes, exhaust manifold, throttle body, wiring, and ecu.

However, I am a little unsure as to how well the s5 ecu is going to run the engine as the compression ratio differs between the two. I imagine it'd be fine.

It'd be a good idea to search next time, before you buy an engine from a different series... To know more accurately what you're in for.

Also curious... The higher compression and lighter rotors in the s5 engines allows for that higher recline. So if you're using an s4 engine with s5 long block components, I'd hazard a guess that you would not necessarily want to Rev it that extra grand.

I mostly just wanna have the car as a nice cruiser. Nothing crazy. So I should just try and hook the s4 harness and ecu to the s5 shell and see what happens?

No... You should not.

So an s5 harness and ecu will work if put into the s4 motor, or do I have to change anything

Read my first post again...

You would need to use your s5 ecu and wiring harness, and bolt all of your current s5 intakes, throttle body, exhaust manifold, front cover, etc.. And that is with no guarantee that the ecu will safely or properly run the s4 engine.

You need to do your research.. Searching is your best friend if you are new to these cars, which it seems apparent to me that you are. It's fine, but almost any question you have has been answered a million times before.. You just have to find them.

Before purchasing another engine, you should have already armed yourself with the basic differences between the series engines.. For example, all the manifolds are different, the front cover and oil metering pump are different, engine and ecu are different, etc.

Running s4 in s5 can be done. But it's a lot of work. Somebody here just recently wrote up a s5 into s4 wiring schematic.

It's easier to run the s5 ecu, throttle body, tps, and s5 sensors though

swap the front cover to the S4 engine and swap everything over, done.

don't bother trying to run the S4 ECU and harness, it's more work than it's worth. the S5 is a better intake system anyways.

the suggestion to delete the rats nest is BS