S54 + FD RX-7?

First of all, 13b-REW is great, but that isn't the point here.

I've been scratching my head, wondering why this hasn't been done. An LS motor just doesn't rev like a rotary. The S54 on the other hand has an even higher rev limit, and produces just about the same amount of power as a lightly tuned 13b on OEM turbos. An FD is lighter than an M Coupe and much more affordable now that S54 coupes are $40k-$80k cars. The FD chassis is miles ahead of an E30, the S54 M Coupe alternative.

Let's explore this, I'm genuinely interested to see if this is doable for ~$20k, the going rate of an LS FD.

It's not impossible, but a good condition S54 lump with all accessories and electronics is going to set you back a pretty penny of that budget. It's also much more electronically integrated than an LS, so if your electrical troubleshooting and circuitry skills are not up to snuff, it could be a very challenging project, especially if you want a working FD tach. I love the S54. They're just not nearly as easy to swap as an LS.

A full S54 swap will run about the same as proper rotary rebuild, but then there's the cost of the swap itself, so yeah, it's not a cheap choice. As for all the wiring issues E30 S54 swaps are becoming increasingly popular so those challenges have been met.

Not as light an engine, and like most DOHC inlines, quite tall and with a lot of length ahead of the front axle. An LS weighs less, is more compact and lower and can be set mostly behind the front axle without much effort. You might be able to do it (I've seen 2JZs in there with no hood) but it'll be tight.

Good point on the length. Plenty of 1/2jz swaps have been done, but they all seem to be drag or drift cars with little regard to weight balance. S65 is lighter and shorter than an S54, higher redline, but it's sure to blow the budget. Hmm.

I'd be more interested to see a 2.3 Ecoboost swap.

Chris_V wrote:

That is horrible.

In reply to dculberson:

I wouldn't say horrible but not very becoming at least.

I want a 7500rpm engine with a 6 speed in my RX8. I'll settle for a 450hp 5000rpm torque monster

Isn't the s54 slanted so it's not as tall in a car as most i6 engines?

dculberson wrote:

Chris_V wrote:

That is horrible.

Yes, it is. But what's necessary to get an inline 6 under the "hood" of an FD.

yupididit wrote: Isn't the s54 slanted so it's not as tall in a car as most i6 engines?

Barely slanted and it's still quite tall. And it's still 2 cyl longer than an LS V8 so that height is way out in the front of the engine where the hood of the FD is VERY low.

If I'm giving up the 13b, I want something that produces at least as much power, and that revs at least as high. I would also like to keep the smoothness of a rotary. What else fits these requirements?

20B

I'm actually slightly serious. A lightly ported non-turbo 20B could make the same power as the turbo 13B at similar weight with none of the twin turbo issues.

Turbo Hayabusa motor. 1000BHP.

What do I win?

Brett_Murphy wrote: I'd be more interested to see a 2.3 Ecoboost swap.

Grab the mazda valve cover and the ford controls pack for 310 horsepower at 5,500 RPM, and 320 lb. ft at 3k.

Gross. I don't know which would leave me stranded first but I'll take my chance with a rotary before anything German.

mr2peak wrote: If I'm giving up the 13b, I want something that produces at least as much power, and that revs at least as high. I would also like to keep the smoothness of a rotary. What else fits these requirements?

Interestingly, my 13B turned 7500 rpm in my FC. The Ford 302 I replaced it with ALSO revved to 7500 (thanks to the cam, Chevy valves, intake manifold and large carb). It merely doubled the output in every portion of the rpm band.

I wanted to put in a mildly modded, aluminum head and intake Chevy DZ 302 engine and have a 9000 rpm redline street engine, like the ones we built for my buddy's '69 Camaro, '70 El Camino, and a couple 914s. Sweet engines and easy to build.

Chris_V wrote:

dculberson wrote:

Chris_V wrote:

That is horrible.

Yes, it is. But what's necessary to get an inline 6 under the "hood" of an FD.

It looked immediately to me like a later TVR... I think the inline six and that general body shape may not be entirely compatible...

The F/K family of Honda Engines seems in the neighborhood.

Ransom wrote:

Chris_V wrote:

dculberson wrote:

Chris_V wrote:

That is horrible.

Yes, it is. But what's necessary to get an inline 6 under the "hood" of an FD.

It looked immediately to me like a later TVR... I think the inline six and that general body shape may not be entirely compatible...

YUCK. Why not some sort of aluminum block 4.8/5.3 short stroke, high revving LS hybrid that was discussed in another thread here?

I wish people would stop wasting 2jzs on cars that they aren't good for. 2j rx7 ruins both imho. Put them in yotas where they belong.

The weight is going to ruin the car's balance.

You can get plenty of power out of a built Renesis.

But in all honesty the most reliable build would be a 13b with a single turbo. That's what I had in my FD and it put out plenty of linear power from a Garrett GT3540R and revved to 8,000 rpm.

Well it's 2021. I own an FD, and it's getting a nice single turbo for Christmas.

Meanwhile, right after I bought the new turbo and supporting bits, my dad is saying he is going to sell his S54 Z3M Coupe. I think I need to buy it and put it in storage, I can't have it where I am now overseas. Letting it out of the family would be a mistake. Kind of in shock actually, never ever thought it would happen.

Funny how after all these years the cars are here and both are appreciating in a way that would make a swap a complete mistake

FD with a Renesis. Does losing the turbo system leave you with a higher power-to-weight ratio?