TheCollector

Are the renisis engines harder to rebuild? I want to buy a car to rebuild to learn how to build rotaries. I see a local Craig's list ad for an 04 rx-8 with a blown motor for like $2500... But I bet I could get it for 2000. So good idea/buy or not?

diabolical1

iTrader: (3)

it shouldn't be any harder to build. there are some differences, but at the end of the day it's still a 2 rotor engine. that sticks to the basic physical design. if you're mechanically inclined and if you understand how engines work, building it should be fairly straightforward.

your question regarding the car really comes down to budget. after buying this car in question, do you have the resources to build an engine (that may require hard parts in addition to the basic rebuild kit)? the next question is do you have the resources to go through it again if you happen to screw it up the first time?

TheCollector

Thanks for the reply! My plan is to sell a car I have for 3500-4000 then buy this car for say....$2000 then build the motor. Is it easy to screw up? I've watched several hours of rebuild footage on YouTube and such. But I've never rebuilt an engine at all before. Seems like most of this is changing gaskets and the seals. And looks like the hardest part is grinding down those oversized parts. How expensive are new rotors if needed or new housings?

TheCollector

Also can't I just buy a template and do a port jobs or something while I'm in there? Sorry for all the questions

diabolical1

iTrader: (3)

so best case scenario is you'll have $1500-2000 ... definitely doable. if you end up needing hard parts, buying them NEW will leave with nothing. your best bet would be to look for them used. as for the rebuilding process, it's more complicated than just replacing gaskets and seals. a lot of it is cleaning and checking the specs, looking for signs of actual or imminent damage, etc. you really NEED to have some sort of idea of what each part does in the functioning engine.

i'm not giving you advice, but if you'll need the use of the car for school or work or some other important recurring engagement, then you may want to consider getting a used, functioning engine to make sure the car is driveable and then focus on rebuilding the one you take out. the bottomline is you have no way of knowing why the engine in it is bad and you won't know until you pull it apart. that way you're not running against a clock because trying to learn as you go can end badly.

as for porting, i'm not aware of pre-made templates for the Renesis (which is not to say they don't exist). also, as i understand it, it also takes a bit more finesse to port them compared to the older engines. they are basically already ported from the factory. you can easily FUBAR a housing if you're not completely aware of what it is you're doing.

TheCollector

Thanks for your info. I actually have 4 cars so this thing can sit for a year if I need it to. No imminent need for the car. Just a toy. And I'm dying to learn more about thes engines anyway. I had a 85 gsl a few years ago that ran but literally could hardly pull a hill at 20 mph. If I knew then what I do now I think I could have fixed that car cheap....it was a cherry car but I think the cat was terribly clogged... Anyway I think the one I found has sold already but I'm gonna keep looking for one.

RotaryEvolution

iTrader: (30)

no, the renesis engines with close to 100k or more miles usually have a handful of parts that are worn beyond reusable, unlike the older RX7 engines which usually weren't that bad unless abused.

which is why a rebuild on a renesis costs $2k and up, anything less and you're most likely buying junk.

TheCollector

Well if u find a car with a blown motor it's hardly worth the build? likely to have bad rotors or eccentric shaft?

RotaryEvolution

iTrader: (30)

if you're basing this all off of buying an RX8 with a known low compression engine then i think your reasoning is flawed. the prices in the $2000-3000 range for them are for the car, not the engine. you might salvage half a good engine from one on average, then you will spend at least $1000, likely more to cobble together a rebuilt one even if you do all the work yourself.

or if you want just the engine, buy one from a wrecked RX8 that obviously was driving before it went to scrap. then at least you're only into it $1500 for a used running engine versus a gutted car and junk engine for $3k.

the early renesis engines are just bad by design, worse than any rotary that came out between 1973 and 2002. reliability is horrible with the series 1's, many cars never make it to 100k without at least one engine replacement, the last time the engines were that unreliable was when mazda was still experimenting with carbon apex seals in the 60's and early 70's. mazda's credibility with the rotary engine again took a major blow with them and could be one major reason why production of the rotary engine was halted completely for the first time since the company went bankrupt nearly half a century ago(now they have a partner company to answer to, who can say enough is enough).

my '04 has 93k, compression is dropping to the point that it is getting very difficult to start after fully warmed up and i know all the tricks to keep a rotary going. they just don't work here(if i can manage 125k out of it then that will have met the average lifespan. probably better because this car was abused before i got it).

if you can find a S2 or later engine then those are much better than the '04-05s which IMO are destined to be scrap piles without ever reaching a decent lifespan, you could drive it like an econo box and get over 200k. it has been done but that kind of defeats the purpose.

not all rotary engines were created equal, though even the S1 renesis was still the most power efficient non turbo rotary engine and equal to the later renesis even if the longevity sucked on them. i love driving our 8 but i know it is destined to have an empty engine bay soon enough.


so engine lifespan is something to consider, since the renesis is also the most costly to rebuild compared to any previous rotary engine design as well.

TheCollector

Well thank you for this shocking input. I knew they weren't real high engines but had no idea they were THAT BAD! I guess it's back to looking at project rx-7s