I need to know what issues I'll run into doing this swap.

I have everything from the s5 long block, OMP, injector, UIM/LIM,
I have the s5 ECU

I also will have everything I need from the s4 motor except the ECU, and fuel injectors.

Since the s4 rotors have less compression, what issues might I have with the s5 ECU?
Do I need to use the S4 ECU?

I searched through 7 pages of results and got nothing helpful.
If you have links to a similar write up, I'd appreciate it.

If you have done this swap, I'd appreciate your feedback even more.

Thanks

 

Is it a turbo or an N/A?

 

I was contemplating doing this too; I have a low mileage rebuilt S4 turbo engine sitting around, and an S5 TII with a blown engine, so I thought I could save myself a few grand and just swap it in...

 

ya, i won't really mess with NA rx-7s, so it's an S4 T2 motor and an s5 T2 car/ECU.

Anyone got anything?

 

Be easier just to swap everything on the S5 motor onto the S4 block, gotta switch out the front cover too....

S5 ecu will run the S4 block just fine, with all the S5 stuff swapped over.

GL

 

Thanks HAI-TEK7,

By saying you mean just take the s4 short block, and use s5 ecu, omp, injectors, front cover UIM/LIM?

Will there be a fuel issue with the s5 ecu managing the s4 rotors, since they are lower compression? Will the motor be running fat?

 

I just did it, but im really no help since its only ran for about 2 minutes.. my turbo seals are toast but it started right up!

 

yes.
I have never had an issue of an ecu running different b/c of different compression. you should be fine.

 

alright, thanks to both of you.

I'll give it a try and let you know what happens.

 

You don't have to change the front timing cover if you decide to pre mix. I've had a lot less problems pre mixing.

 

i think i might still run into issues if I premix, won't the S5 ECU be looking for a signal from the S5 oil metering pump?

 

It will throw a code, but you can "trick" it with a resistor. Do search, i've seen a thread recently.

GL

 

that is what I've been told.

The biggest part is getting it to run smooth, then I'll worry about reliability mods.

 

I have a s4 TII ecu. I'm willing to do an even trade for your s5 TII ecu. I think having the s4 ecu will make things alot easier.

 

how?

 

FYI, the S5 engine wiring harnesses won't bolt up to the S4 chassis harnesses, and vice versa. I've read about these in the archives and other links.

 

so, i'll just stick with the s5 ecu.
My biggest worry was the fiel management.