I have an 86 FC S3 and a 90 FC S5. My S5 needs a motor as well as everything else under the hood, and my S3 needs nothing. If I were to take the ECU, motor, coils, block fuses, relays and such and put them in the S5, umm...well...will it work? Will it bolt up and such, or are there other issues that I need to be aware of?

Thanks.

-mac

 

First of all the second gens were Series 4 from 86 to 88 and were Series 5 from 89 to 91. S3 was the last years of the FB, ending in 85.

If it is in fact an 86 then yeah you can pull everything out and put it in the S5, but it will take a fair amount of work. First the OMP (oil metering pump, it squirts oil into the rotor housings and the into the combustion chamber) the S5s had a electronic OMP and the S4s had a manual OMP. So the ECU in the S5 will go nuts unless there is an electronic OMP plugged in. You can swap it if you want to, but its not easy.

now the S5s had an 8k red line and the S4s had a 7k red line so you would have to address that, and I believe the fuel map in the ECU is different, too.

I imagine you could modify the S5s harness to take an S4 ECU, and you could swap the guages and everything, but after all that work, you will still end up with a frankenstein FC and one that will be slower too.

I say get an old S5 motor and rebuild it. Or do a turbo swap. Unless you are planning to modify it quite a bit I would personally not recommend putting a stock S4 motor into an S5 FC. Then end result will not be equal to your efforts.

 

1. 86 were S4.

2. Read this. http://www.rotaryresurrection.com/2n..._s5_diffs.html

 

Yeah, I knew I was going to make some stupid error in my post! LOL I know it will be slower, but I can't find any S5 anything for a fair price. All I find is complete cars, or nothing, and the complete cars have tags of 6 grand!

I just wanted to get it on the road until I can find the crap I need for it.

So, change out ECU, the gauges will have to be replaced as well? Humph!

Thanks for the help.

-mac