Rote8

I am seeing higher MAF numbers at lower rpms.
The boost pressure can force more air into the chamber.
I am sure a turbo would respond the same.

stinksause

iTrader: (5)

Wat engine management are you running?

sinned2545

Theres a company on 7club doing these rotors. but i think there like 3k each.... but i believe u can have what ever compression u want
heres the thread
http://www.rx7club.com/showthread.ph...t=lopez+racing

Heres there site
http://eastcoastparts.com/html/billet_rotor.html

khronus79

iTrader: (1)

Ahh yessss, 6lbs billet aluminum rotors, 2k each.

TeamRX8

iTrader: (25)

yes, except they don't offer them with the Renesis keystone side seal arrangement "yet", so they're a no-go if you intend to have functional Renesis side exhaust ports.

That weight is stripped, it's about 7.5 lbs fully functional with side gear etc. as I recall and while they can be made lighter, they don't have the capability to balance the rotating assembly out below that weight. They do include the Renesis side cutoff seal groove though. It supposedly helps when running methanol in high boost 13B applications.

unless they changed the price recently they're $4,000/pair which includes you providing the rest of the rotating assembly for them to balance it

it will be interesting to see how long the side seals function in that 13B rotor/Renesis hybrid, not onbly will they take a beating from the heat and lacking support over the side port openings, there's the carbon issue ...


.

Bastage

iTrader: (1)

Since Cam is letting us let cats out of bags, I will mention that Cam has also been machining RX-8 rotors to fit RX-7 apex/corner seals. Mine is his first build with these rotors.

1500 miles so far and running strong. I will be taking my car to a dyno sometime in the beginning of February.

sinned2545

this is a great thread.... its good to see that Rx8 is really taking off with power upgrades..... Seems like acouple years ago every body blew there motor cause of boost.... now theres so many fun little tings going on

khronus79

iTrader: (1)

any more updates on this???

bowser

what he said

stinksause

iTrader: (5)

^ what both of them said

Brettus

iTrader: (2)

what seals did they use - stock or aftermarket ?

stinksause

iTrader: (5)

so I got an update ... after some of my own digging this can be done by using an rx7 gsl-se center housings as the coolant seals match the renesis design ... 2 problems though
1) Those housings have been discontinued I believe and are hard to come by
2) You will be adding a BUTLOAD of overlap between intake and exhaust and kinda defeating the purpose of the renesis (good luck getting it to idle for a street car...) ... a better solution would be to put a small pp into the renesis center housings to minimize overlap and improve the flow

you obviously need a new manifold etc

OP, the original renesis is not the best candidate for turbo for 3 main reasons

1) higher compression
2) shorter apex seals
3) side seals too close to the edge of the rotor

You can remedy the first two by using billet rotors with taller seals.
You can use a double spring behind the side seals, but that is more of a band-aid than a solution

IMHO, It is much easier to put an FD motor in and call it a day
OR put in a 6 port w.o the turbo and get him to learn stick ... he will be just as fast as the turbo auto

OP, I do realize this thread is over 2 years old ... what did you end up doing

ZumnRx8

lmao

stinksause

iTrader: (5)

ok ... its like 1.5 years old ... my response does add to the general knowledge base of the forum so plz dont hate and provide a meaningful discussion

zoom44

we'll start here.


this is wrong

stinksause

iTrader: (5)

1. You are an admin so don't be mean, you hold an almost deity-like status with absolute power when it comes to these boards, hence you should be above this, educating lowly peons such as I in the ways of the rotor.
2. What is your side of the discussion?

I have talked with Dave @ KDR at quite an extent regarding boosted Renesis motors with a 300, 350+ whp goal. (It sound like the kit OP was working on was in the 300ish+ range) According to him it is very hard to make the msp be reliable under boost like the 13B for three big reasons that I have listed above.

The compression reasoning is that the shallower tub simply does not allow you enough room to cram the air and fuel into.

After all this thread is not about making an engine that will put out 300+ whp for a couple of months and then puke. This is about putting down that power consistently for an extended period.

The Esmril kit has shown that 400+whp is achievable, but for how long? How many people have run that set-up for over a year without having to rebuild the motor? There are plenty FD's putting down that kind of power and more consistently for multiple years before doing a rebuild.

So what is the difference between the two engines? Exhaust ports, seals, and compression. All of which I have addressed. So please point out the whole in my logic.

reddozen

iTrader: (1)

The compression issue is more an issue of detonation, not that there's "not enough room". The more the air is squeezed the hotter it gets, and the less it takes to ignite. So the compression ratio itself is a moot point. The solution is better cooling and better tuning.

I would agree that the exhaust ports are restrictive, however, not enough to restrict the power to under 400 HP.

Those are the only real obvious reasons why I think it's pointless.

stinksause

iTrader: (5)

Therefore, would lower compression not give you a better buffer against detonation? And by extension, make the engine more reliable in the long run?

We all know that there are an almost infinite amount of variables that come into question regarding tunning: Elevation, temperature, atmospheric pressure, humidity, the particular gasoline blend being used to name a few ...

High compression lowers the margin of error that you can have with tunning, and it is impossible to tune for all the different conditions that a vehicle will face in the real world perfectly.

I agree, that for a track car, these variables are greatly reduced as the environment is more consistent, but in OP's case this is street driven from what I can gather.

For a street car, lower compression will allow for a larger margin of error in terms of the inputs and how much they can be off from ideal values... as the environment and fuel will be far from consistent

An interesting point is that one of the engines that I saw waiting for a rebuild was running the esmril kit and have upgraded 1 piece rx7 style seals. It failed due to blow-by through the side seal. I do not know if it failed due to a detonation event or not.

reddozen

iTrader: (1)

Still not the solution. It's a patch job. For the wasted money spent on lower compression rotors you could more effectively beef up the cooling systems.

For what this thread proposes, you're better off with just doing an engine swap. If the Renesis doesn't fit your needs, then don't use it. now, if you were to actually be fixing the shortcomings of the motor, then that's a different issue, and that would include resolving the detonation issues, and not patching it up with a compression drop, because you will still have an internal heat limit that will limit the maximum potential. So you may push that line out a little further, but I would imagine that it wouldn't be much before you would have to upgrade the cooling systems, which is what you're apparently trying to avoid...

You're also looking at about a 10HP drop from the compression change, and less efficient fuel usage. The compression is high because it's more efficient at generating power and burning fuel.

I'll never agree that lowering compression is the be all / end all solution. The solution in my opinion is better heat management and lubrication in the engine. Solve that, and you can boost till the dowel pins pull apart.

Red Devil

You should have done yourself a favor and stopped right there at that conversation. Guys like Dave or Cam have literally spent decades racing and building these engines. I have the pleasure of knowing both pretty well, and both have built 400+whp Renesis engines on the 10:1 rotors, and yet you are still getting Dave's commentary as you wrote above...why would that be???

stinksause

iTrader: (5)

I agree with you, but given the OP's situation this would probably be an effective solution. By no means am I claiming that it is an end-all.

Personally, I think that a good engine configuration would be to improve cooling through a better radiator/ polished and vaned cooling galleries, mazmart waterpump and do a semi pp exhaust port on the housings to improve flow.

If the figure 8 on pg 6 in this article http://www.rotarydevelopment.net/Rot...790_Rotary.pdf is correct, then you should be able to add a small pp port without jeopardizing no-overlap and improving exhaust flow. What else would you do? What about lube? Premix, or are you thinking something else?

stinksause

iTrader: (5)

That is true. They are great guys with many years of experience. I get their opinion to make up for the lack of my own experience. I concede that I am new to the scene and I am doing a lot in my power to make up and take on the steep learning curve. This is why I am having this discussion. However, I miss your point.

They have built 400+ Renesises but how long do they last? I am focusing on reliability that is required of a street driven car that can still perform at track events. I guess it boils down to one statement: FD's can do it, what is it specifically about our engine that prevents us from doing it?

You spend 6 grand, build an FD motor to 400+ whp and it will last you a few years. With an rx8, you would be lucky to last 1 year, and that is exactly what Dave told me.

Dave: "If that was my rx8, I personally would not turbo it. The engine cannot handle over 300 whp and be reliable." He then suggested that I do some suspension mods, flywheel, exhaust, etc ... and maybe play with the diff ratio or street port it.

After I asked why, he took me into the engine building room and showed me failed boosted rx8 motors torn apart. The reasons he gave were the ones I listed above, although perhaps some may have been lost in translation/ my understanding, as I was not taking notes. Although I am pretty sure that I got the gist of it out here.

As I have seen plenty of evidence of rx8s running reliable a little over 300whp on these boards, I decided to take it here to get a second opinion.

He did concede that the only reliable boost to be had is the greddy turbo kit in stock form at stock boost, with the fixes of course!

zoom44

where was i mean? i simply said "this is wrong".

above what? pointing out where someone is wrong. no not going to stop doing that.

my side? this exact topic has been covered half a dozen times in the last half a dozen years. my side is already on record in THOSE conversations. i gave you an opportunity to go out and look for the reasoning or simply ASK

so i dont have to re-type things i have typed before( and to save everyone from my poor typing) re-read what reddozen wrote. thats basically it in a nutshell. or go read the axial flow supercharger thread.

stinksause

iTrader: (5)

exactly what I was looking for ... thanks

I apologize for mistaking your comments for hostility as this was a hankering back to my Honda days.

Red Devil

You didn't miss my point, I just didn't want to put the words into Dave's mouth.