So during my monthly perusing of JDM motor tranny combos on EBay I noticed RX8 engine/tranny combos are really cheap.
So is it the perception that these motors are horribly unreliable and going to grenade at any moment or some other factor?
It intrigues me because these might make the little Datsun go like mad.
Generally they're S1 motors which had oiling issues if you didn't take care of them. The S2 motors have extra oilers and are a bit more expensive.
S1 motors seem to be pretty ok if you take care of them in that weird way rotaries need to be looked after. Mazda redesigning it and warrantying the engines that failed makes people suspicious.
I looked into one for my RX3 but ended up with an S4 13b.
In reply to Tom1200 :
How cheap? Broken RX8s are abundant & cheap around here.
$1000 to $1400 with trans and ECU.
The other plus is even with the extra weight the Datsun would only be 1800lbs. I seem to recall RX8s make around 170-180 at the rear wheels.
Are you looking at engines with manual transmissions? The ones that came bolted to automatics are a lot less desirable.
In reply to obsolete :
Manual trans; I saw one for $900.
Renesis gets a bad rap. Buying a used one would prove to be pretty risky. But you could get lucky.
All of the cheap ones are 4 port engines.
The RX-8 was sold with 4-port engines and 5 speed transmissions in the home market. In the US, all 4 ports were automatic, and all series 1 6 ports were 6 speed manuals. (All Series 2s are 6 port, and S2 engines are not cheap)
The 4 port is not nearly as powerful, because it is essentially a 6 port engine without the high RPM auxiliary ports. They're only good for automatic models, and the manual trans was never used here. So, it's not that valuable for re-engining an RX-8.
I do understand that there is an IT7 subclass where they use these cheap 4 port engines as a substitute for the impossible-to-find 12As. In this case, power or compatibility is not as important as consistency and availability for a spec class.
In reply to Pete. (l33t FS) :
Keep in mind a Datsun 1200 is a 1600lb car so even 150hp at the rear wheels would make it fly.
In reply to Tom1200 :
I once literally did contemplate putting a rotary in a 1200, but I actually dropped into this thread to say "a better than average example of market forces."
In reply to Tom1200 :
No doubt. But bear in mind, they are not high RPM engines, at least not compared to the 6 port units.
They are also very wide, mounting is strange because they use the vestigial peripheral exhaust studs to hang an engine mount from, and the electronics are not terribly swap friendly, so you'd need some form of engine computer.
It's a lot of weight and a lot of hassle to end up with something that is fairly unreliable because Mazda was running the hot exhaust gases past the super thin side seals. Apparently the exhaust heat also warps the snot out of the side housings over time.
In reply to Pete. (l33t FS) :
Good to know.
At a Cars & Coffee 2 years ago I saw a guy that had a turbo K20 with an RX8 trans in his Datsun, so the trans must be decently strong...but it may have blown up on the way home also.
Pete covered it pretty well, but I will add my own cliff's notes from researching this:
- Can't realistically use stock ECU. Megasquirt is pretty straightforward but does not support the oil metering system (must run pre-mix without it) or the 3 stage induction system (this system helps torque at low rpm).
- Lots of Series 1 motors had early failures in the 20k to 60k miles range. Low compression issues. Rotor housings tend to have a lot of wear, so rebuilds are expensive. Bearings are also subject to wear which is not so much a thing with the 12A and 13B motors.
- For S1 motors, the remedies to improve longevity seem to be running higher oil pressure (cheap FD rx7 regulator bolts in) to reduce bearing wear and running pre-mix to reduce housing wear. Not sure how effective these things are. I also heard that removing the cat helps with heat issues that affect side seals.
All that being said, they seem to do really well as race motors. I have 3 friends who have been racing the SCCA "IT7R" class for 5-6 years that Pete referred to above. 1st gen RX7 with stock 6 port renesis motors run by megasquirt backed by a 1st gen transmission. They have had pretty good luck buying S1 motors off craigslist for a few hundred dollars and running them without a rebuild. The guy who has done the most events started with a 90k mile motor 5 years ago, and is just now looking to replace it because a coolant seal failed. The engines make about 190 hp to the wheels.
So, for your racing application, it might still be worth considering. You can also get factory remans from Mazda motorsports for ~$3300 if you can't source a good used unit.
And just a note from Pete's comment above - when IT7R was conceived as a way to solve the lack of 12A engines problem, there were 2 competing ideas - the first is what I described above (which won out in the end) plus another solution using the 4 port Renesis motor with a 12A front cover, an adapter plate for the oil pan, and an adapter plate for the 12A intake manifold and carb. So you essentially could just swap out the 12A block for a Renesis 4 port block. At least one car was built, and ran a few events, but people latched on to the other spec. I'm not sure how much power it made, but it was definitely faster than my 12A car.
In reply to sevenracer :
Thanks for the info; it appears the little 1200 will be doing mostly track day duty as I've gone to the F500 as my primary vintage race car, so things like premixing or mixing and matching parts wouldn't be an issue.
I go round and round with various swaps (because I'm a flake like that) and either I end up with something that requires more care & feeding than I want, is expensive, or they are heavy. Most of the twin cam 4 cylinder motors come within 50lbs of a V8 swap. I could simply build a proper race engine but those are 6-10K. For 8-10K I could install a Cosworth BDA-BDG rally spec engine that would make the same power and would need less maintenance.
And so I keep running the ever gutless moderately tuned A series engines and dreaming of an easy button. Motor that's less than 300lbs, makes 150hp at the wheels and doesn't cost more than 2K.
With regards to Jim Croce: Don't tug on Superman's cape, don't spit into wind, don't pull the mask off the ol' Lone Ranger and don't waste your time with Rotary Engines.
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