rx8 engine in a 5 - someone tell me its a nightmare quickly

[jamhow79]

Seems logical enough; lightweight, compact engine with a reliable (!?!?!?) 231 horses and their getting cheap(ish) to pick up from breakers yards. The earlier thread about the highs and lows of forced induction have dented my enthusiasm for superchargers - why does no one appear to go down the rotary path ???

[MX-5 Lazza]

Because over here we prefer FI due to it being fairly straight-forward, reliable and very effective. In the states they do a lot of engine swaps but they prefer V8s to rotaries. It has been done - There is a Mk3 with an RX8 engine and I'm sure I've seen a Mk1 with an RX7 engine but the gains over a boosted MX5 engine are minimal - the weight difference isn't as useful as you'd expect as all the weight saving is just over the front wheels which will change the balance of the car, one of the cars strongest points and the more power you have the less weight is a problem.

[OnlyMX5ives]

Erm because the worst thing about an RX8 is the engine.

They are very thirsty for oil and water and the reliabilty is still suspect.

As has been proven by literally thousands of us, FI is perfectly reliable IF IT'S DONE CORRECTLY.

[itiejim]

Rather a short sighted and old fashioned view IMHO. They certainly like fuel and are designed to use some oil. However, over the past 40 years or so they've managed to make the rotary engine very reliable. It's extremely powerful for it's weight and can be made to produce miles more power than you ever see out of an MX5 - FI or not!

The FI is obviously a well trodden path, however, if you're looking to be a bit more adventurous I think it sounds like a great conversion.

OnlyMX5ives said:

Erm because the worst thing about an RX8 is the engine.

They are very thirsty for oil and water and the reliabilty is still suspect.

As has been proven by literally thousands of us, FI is perfectly reliable IF IT'S DONE CORRECTLY.

[bluetone]

Because you could just buy an S2000 (or similar) instead?

[OnlyMX5ives]

Someone on Nutz is just about to do it.

Budget is £4k on labour alone IIRC.

I'd rather have a V8.

[MX-5 Lazza]

I'm not so sure you could get "miles more power" from an RX8 engine as they don't take well to being boosted and aren't that tweakable na without expensive rebuilds. An MX5 engine boosted and well tuned can make a safe 270bhp. Can an RX8 engine match that at a similar cost? An RX7 engine, now that's a different story...

[itiejim]

http://www.turbo-kits.com/rx-8_turbo_kits.html

326 WBHP - 400 ish at the crank?

Not cheap, but then no engine swap is going to be. Personally I think I'd look at a 3 litre Alfa V6, 240 reliable bhp in a fantastically refined package with no lag, great throttle response and a good soundtrack.

[GravelBen]

I've always liked the idea of slotting the Mazda KL-ZE 2.5 V6 into one - nice revvy 200bhp as standard with a sweet V6 sound to go with it, and no heavier than the original engine apparently. Would suit the character of an MX5 perfectly IMO I don't know why Mazda didn't build one themselves! Not wanting to tread on the RX7's feet perhaps.

Edited by GravelBen on Friday 12th February 12:18

[franv8]

GravelBen said:

I've always liked the idea of slotting the Mazda KL-ZE 2.5 V6 into one - nice revvy 200bhp as standard with a sweet V6 sound to go with it, and no heavier than the original engine apparently. Would suit the character of an MX5 perfectly IMO I don't know why Mazda didn't build one themselves! Not wanting to tread on the RX7's feet perhaps.

Edited by GravelBen on Friday 12th February 12:18

I had the 160hp version in an MX6 (KL-Z) - so basically it was a different inlet manifold and cams from memory to give it the extra go.

This was the most unreliable car I ever owned (and I'd had a few old fords too - although apart from the modded ones they were actually pretty good) - the thing that really taints me about this engine is that a con rod let go at 65 (I was in 5th at the time!) - and the engine munched EVERYTHING inside it. There was a crack running down from the front corner of the block by one of the heads all the way down the side at a 60 degree angle down to the sump, and this crack was a half inch gap. So time for an ex-Jap crate engine, and, because I was practising exceptionally bad luck at the time, the con rod stopped itself leaving the vehicle by lodging itself in the downpipe that runs under the sump.

And, considering it had all the multivalve toys, cams and variable inlet manifold, why it liked to drink so much (20-24mpg even driven carefully) - when at the time I could get something not a milion miles off that range with a 50's derived small block, I was not amused.

It was very smooth though, and I actually moved over to the 5 from it since it would sit a bit too easily at 120 leptons on the A1. (clearly those speeds weren't going to improve economy by the way!)

Trouble is with the Mazda, it's such a carefully crafted car from the factory changing anything has a high chance of spoiling its 'togetherness'

(Sorry for post length - sometimes I think I'm paid by the word...)

[GravelBen]

Thats interesting, never heard much bad about them before from owners - maybe you had a lemon?

Apparently the fundamentals of them are very good and they'll happily go to 600+ bhp with a couple of hairdriers bolted on.

[Busa_Rush]

GravelBen said:

Thats interesting, never heard much bad about them before from owners - maybe you had a lemon?

Apparently the fundamentals of them are very good and they'll happily go to 600+ bhp with a couple of hairdriers bolted on.

If it's the same engine that was used in the Ford Probe then it's not worth bothering with, not very powerful, poor torque and unreliable. Nasty when compared to what else is out there. It was smooth though, I'll agree to that.

[GravelBen]

The 160bhp KL-DE was used in the Probe etc, the KL-ZE is the 200bhp version with a lot of differences - completely different heads for a start, but the same block.

They also used a destroked(IIRC) 2L version in the BTCC Mondeos as it was considered better than anything Ford had.

Edited by GravelBen on Sunday 14th February 08:32