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I currently already have a running rx8 with 104k miles on first motor & i know the compression wont last much longer. ive Been saving for a little bit of time now but i cannot make up my mind on which path i want to take. If anyone has any recommendations or opinions i would appreciate them.
(For those who dont know what hybrid is, I want to take gslse housings from a rx7 and put them together with the rx8 plates.) (Everything should be plug and play except i will need the rotors cut to take rx7 apex seals and possibly a new PnP ECU)
THE MOTOR WILL BE BOOSTED
-What does the REW offer that a hybrid wouldnt? - Would the extra exhaust ports from the hybrid help with reliability over the REW?
Why wouldn't you just rebuild the Renesis ?
Neither of your options will make more power although the rew is the best turbo engine if that was what you were thinking.
Why wouldn't you just rebuild the Renesis ?
Neither of your options will make more power although the rew is the best turbo engine if that was what you were thinking.
i Probably should of put that in the post, i definitely plan on going turbo.
If you want over 400whp ...rew is the logical choice.
Under 350 and you have to consider the Renesis as well.
Hybrid is a poor choice at any power level.
If you want over 400whp ...rew is the logical choice.
Under 350 and you have to consider the Renesis as well.
Hybrid is a poor choice at any power level.
what makes you say hybrid is a bad choice?
ive actually heard that alot of the rx8 internals are pretty good, Only thing ive seen is the block cracking on the rear plate corner but studs should help with tht
ive actually heard that alot of the rx8 internals are pretty good, Only thing ive seen is the block cracking on the rear plate corner but studs should help with tht
Another thing is i already have a rx8 block it would save me alot of money
ive actually heard that alot of the rx8 internals are pretty good, Only thing ive seen is the block cracking on the rear plate corner but studs should help with tht
Originally Posted by Brettus
Because a hybrid performs worse than an rew over 400 and worse than a Renesis up to 350 .....
Sounds expensive and if you don't have the pockets or knowledge, why not lfx? 300-350whp on an n/a engine sounds pretty neato speedo to me. If you really want a boosted rotary I say rebuild your renesis and build/boost that, cause I don't want to wait 3 years to see your project done, way too many unfinished projects around here.
I gave it to you simply but it obviously wasn't what you wanted to hear.
There are multiple threads on hybrids on this site...read them ..... If you find anything that challenges what I said above, let me know and we can have a discussion.
Well ....you started with a thread title 'REW or Hybrid Renesis'. So that's how I addressed it.
Look at REW dynos over in the rx7 forum and compare them with the lone mazdatrix hybrid dyno from many years ago (still the only decent hybrid turbo dyno we've seen on here). Sure the Mazdatrix made ok peak power and if you were only looking at peak power you'd be concluding that it's a good thing . It's nothing special by comparison though. The REW easily makes the same power and also has been shown to make double that without much fuss.
Sure a lot more development has gone into making high power REWs vs hybrid Renesis but and when you also consider response (IE spoolup ) you realise what a POS the hybrid engine really is. Until that is addressed, there is absolutely zero advantage in a Renesis hybrid vs using an REW.
Then you have the engineering side of it : a hybrid using a Renesis rotor will always be handicapped by the high compression ratio and the relatively light/weak rotor . A hybrid using an REW rotor will be handicapped by the inferior sealing capability of the oil/scraper seals and the likelihood of the side seals eventually colliding with the side of the intake ports.
So if it's a no for over 400 vs the REW it's a resounding no vs a stock Renesis turbo for under 350 as well for much the same reasons mentioned above.
Well ....you started with a thread title 'REW or Hybrid Renesis'. So that's how I addressed it.
Look at REW dynos over in the rx7 forum and compare them with the lone mazdatrix hybrid dyno from many years ago (still the only decent hybrid turbo dyno we've seen on here). Sure the Mazdatrix made ok peak power and if you were only looking at peak power you'd be concluding that it's a good thing . It's nothing special by comparison though. The REW easily makes the same power and also has been shown to make double that without much fuss.
Sure a lot more development has gone into making high power REWs vs hybrid Renesis but and when you also consider response (IE spoolup ) you realise what a POS the hybrid engine really is. Until that is addressed, there is absolutely zero advantage in a Renesis hybrid vs using an REW.
Then you have the engineering side of it : a hybrid using a Renesis rotor will always be handicapped by the high compression ratio and the relatively light/weak rotor . A hybrid using an REW rotor will be handicapped by the inferior sealing capability of the oil/scraper seals and the likelihood of the side seals eventually colliding with the side of the intake ports.
So if it's a no for over 400 vs the REW it's a resounding no vs a stock Renesis turbo for under 350 as well for much the same reasons mentioned above.
Thats fair, i know i wouldnt be able to push the boost with the rx8 rotors.
Maybe a better question i should of asked is renesis vs Hybrid.
I guess the REW is only worth it if im really trying to get past the 400hp point.
Thats fair, i know i wouldnt be able to push the boost with the rx8 rotors.
Maybe a better question i should of asked is renesis vs Hybrid.
I guess the REW is only worth it if im really trying to get past the 400hp point.
Hybrid Renesis SHOULD make more peak power than a stock Renesis no question (although after 20 years we have yet to see anything truly impressive).
BUT ................... I'd wager my current 340whp bone stock Renesis would crush any hybrid making the same peak power in terms of performance AND reliability AND driveability AND any other measure you care to judge it by.
Hybrid Renesis SHOULD make more peak power than a stock Renesis no question (although after 20 years we have yet to see anything truly impressive).
BUT ................... I'd wager my current 340whp bone stock Renesis would crush any hybrid making the same peak power in terms of performance AND reliability AND driveability AND any other measure you care to judge it by.
Question: Are you wanting your RX8 to be fast, or are you simply desperate to own a turbo rotary? Dare I say if the answer is the first, then there are more cost effective options IMO than turboing a rotary.
The challenges swapping in a REW are not much different than swapping in a piston combo. I've swapped in an LS1 in my RX8. I did the swap myself, and the total project cost to get the car back on the road and running, cost me less than it would have to buy and rebuild an REW block alone. My car still maintains a 48/52 weight distribution, handles great, and it laid down 392rwhp with just a cam upgrade and decent exhaust. I've just about finished rear mounting a turbo to the car now, and with nothing more than adding some extra gap in the rings, low boost, I'll easily achieve a reliable 550-600rwhp. You won't get anywhere near that reliability or power with a turbo Renesis.
Those Honda K24 motors seem to be the popular motor choice to swap at the moment. Have you considered something other than the Rotary to make power?
Question: Are you wanting your RX8 to be fast, or are you simply desperate to own a turbo rotary? Dare I say if the answer is the first, then there are more cost effective options IMO than turboing a rotary.
The challenges swapping in a REW are not much different than swapping in a piston combo. I've swapped in an LS1 in my RX8. I did the swap myself, and the total project cost to get the car back on the road and running, cost me less than it would have to buy and rebuild an REW block alone. My car still maintains a 48/52 weight distribution, handles great, and it laid down 392rwhp with just a cam upgrade and decent exhaust. I've just about finished rear mounting a turbo to the car now, and with nothing more than adding some extra gap in the rings, low boost, I'll easily achieve a reliable 550-600rwhp. You won't get anywhere near that reliability or power with a turbo Renesis.
Those Honda K24 motors seem to be the popular motor choice to swap at the moment. Have you considered something other than the Rotary to make power?
To be honest i want to keep the rotary no matter which route i go. I know there are alot of good swaps out there but none of that has never really caught my eye. Rotary just sounds too good to me.
If you want to go turbo and plan to just rebuild the engine, I would honestly just go with a REW swap because they can last quite a while when built correctly. You're also going to be pulling it out anyways so might as well go with the REW, or if you want turbo the renesis like Brettus(?) has.
I rebuilt my renesis and honestly even with everything stock its still a really fun and quick car to go on the twisties on. A well built engine will probably be the best thing you can do whether it be REW or renesis.
There's also a couple of people on here and I know several others that have REW swapped their RX8's and made a lot of power while keeping things simple. Hybrids are not the way to go- trust me.
Turbo = REW
Non-Turbo = RENESIS
And im sure theres a ton of information on doing REW swaps too.
Anyone with some real info on hubrids? seems like no ones knows what they are saying
So to give some context, there are I think 3 or 4 threads talking of the hybrid motor. Not many have been documented as running or running great. As a community its pretty easy to come to the conclusion that they aren't good. Even with Mazdatrix's hybrid motor, the dyno chart they have shown is a bit lacking benefits over a renesis or REW. Also, any more informed members please correct me if I am wrong below:
There are two main reasons the hybrid motor isn't a proper option if you are considering an REW or another variation of a rotary. First of all, the exhaust flow from a hybrid is too open for this small of an engine. Exhaust flow is going to be very slow. Slow exhaust = slow spool = absolutely no low end torque.
Second is due to the fact that any chance of overlap and scavenging of the exhaust is gone. Aka, no assists of extracting exhaust from the combustion chamber aside from the initial pressure differences once the single combustion chamber is open.
I won't get into further detail as I do agree, this topic has been brought up multiple times (I have I believe twice in the group already) and it ultimately isn't worth the risk. If you have piles of money you want to soak with lighter fluid and watch it burn, they by all means try it! And document it please. But I assume you don't (like most of us) so the real question should be what are your power goals, and what is your budget. Simply having a block laying around will be a fraction of the total cost of a build.
Primarily cost is going to be the determining factor.
1-For a turbo Rx8 your talking 6-8k for the new engine another 5-7k on turbo, plumbing, ECU, injectors. Then another 2k+ on various other components you run into.
2-A REW you are talking about that with the addition of a lot more custom fabrication (your time or money/trust). Then complete standalone which wouldn't pass emissions. Engine mounting. Transmission. Exhaust. Fuel. etc.
3-A questionable hybrid is all the above with the addition of custom engine building with parts that may not all be happy together.
The amount of knowledge alone will take you months of reading and can't be summed up to make a simple decision.
-How to rebuild and inspect the individual components. Likely at 100k+ miles your components are already toast.
-Different porting and intake manifold design pros and cons for both the REN, REW, and Turbo versions
-How/why mazda designed the REN vs the REW. Why didn't they do hybrid already? Patents?
-REN NA and Turbo build threads
-RX8 and RX7 REW turbo threads.
-REN hybrid threads mostly based on the above combined knowledge.
Maybe someone else has another more in depth source of knowledge, but look into the FC generations and compare the NA vs Turbo engine designs. If you want to draw any knowledge from mazda released design wise, why they made different choices when it comes to porting and intake setup. Otherwise its generally accepted that the REN is the best NA 2 rotor and the REW is the best Turbo 2 rotor currently available. Turboing the REN with a few engine mods could get you to 350hp, but after that the REW would be far more reliable power wise if you have the money. Considering most stock Rx8s are probably around 180hp reaching 300 to 350 may be all you want.
07-24-2022, 02:56 AM
