Out of pure cuirosity- have read countless times that the renesis engine is thus far teh best desinged rotary engine. Although there is much talk bout it being under powered- well lets compare the turbo end of it-

i think may of us rotory fans (no pun intended) are comparing the NA renesis to the 13b rew twin turbo rx-7 and are disapointed. with that thought-

what power is being made via dyno results on mild built twin turbo (as the rx7 was) renesis motor.

if one compars the NA rx7 (fd) to the na rx8 what is the true power difference on the dyno?

Is the renesis that much better of a performer- or is it just more reliable? This is the question.

http://en.wikipedia.org/wiki/Mazda_W...gine#13B-Turbo

as you can see the 13b dei is making less power from the start as an NA motor (160hp max stock) vs teh suposed 190-200hp rwhp btw out of the renesis- this is why i am curious about a twin turbo renesis motor. how much power does it make mildly built (not to be redundent)?

 

there was no N/A FD, you would have to go back to the FC days fpor a N/A RX-7

but I think the N/A S5 FC was like 165 h.p. if I remember right (S4 was 148 I belive)


so yes, compared to a N/A 13B the RENESIS is MUCH better! this is nothing new.
I agree people are comparing the RENESIS to the 13BREW (which is the twin turbo 255 h.p. FD RX-7). wihch in this case, yeah it's less H.P. but it's also missing 2 turbos.

 

'86-'88 was 146hp
'89-'91 was 160hp

We have plenty of tech threads on this topic. The Renesis is easily capable of some very nice numbers when boosted but the ultimate limiting factor is the high comression ratio. It still isn't a factor on a well tuned engine until about 400hp or so.

With today's technology, there isn't much point to twin turbos. 2 isn't necessarily better and the stock twins in the RX-7 were just pathetic.

The Renesis is truly a much better performing engine. It does everything better than the 13B. Don't try to tell that to people on the 7 forum. They disagree but none of them really understand the Renesis either. It is a cleaner, more efficient, and far more powerful engine than the nonturbo 13B is. The 13B needs to be ported to get near the power of a Renesis but even then it lacks every other good trait. The 13B's day has come and gone. It's an obsolete thing of the past. In the piston world it would be like comparing a modern engine to one from the 70's. Not even close and actually that comparison is accurate as for the most part the 13B didn't appreciably change in over 30 years.

 

You're wrong about it.

Renesis is Still part of the 13B family

Hehehehehehe ...

Another thing that 7 owners dont get is that, their car has been out for how many years? It would be sad for them NOT to get higher HP number than Renesis does today. but give it another year or 2 Im pretty sure Renesis can reach if not better than the performance level of the earlier 13-B family engines.

 

Only from a displacement standpoint. Then again that would make any piston engines of the same size in the same family as well!

 

Rotary God.... well put.

I just didnt feel like going into as much detail as you. good job.

my h.p. number were close. it's been a few years since I have needed to access that part of my memory.



if someone were to make a low compression rotor that you could put in a RENESIS, that would open the doors for boost levels!

off hand I cant think of any reason why you couldent put REW rotors in a RENESIS??? I know the renesis rotos have the side seal moved way out towrds the face of the rotor, and other small things like that, but nothing on the rotor housings or irons that would keep you form putting in differant rotors right?

 

The side seal issue pretty much makes any long term reliabilty issues moot with 13B rotors. We're stuck with the Renesis rotors unless someone casts and machines new ones. I have no doubt that you could put 13B rotors in a Renesis and have it run... for a while. My advanced Renesis tech thread gets into the reasons why they wouldn't work for long.

 

that's what I thought.... although I cant think of any reasons off the top of my head why it wouldent work for long??? hmmm???


didnt they put the side seal out furthar to help keep the rotor from "walking" at high RPMs?

 

The side seals do't affect rotor walking. That's a high rpm issue and that's what Racing Beat takes care of by installing a snap ring on the rotor gear. The Renesis side seals are farther out to help minimize any area on the sides of the rotors where gasses can hide. By pushing them outward they also allowed themselves to use a larger intake port as the edge of the side seals isn't as likely to drop into an intake port and break. The older 13B side seals are not far enough out and will suffer this fate in the longterm. Not to mention the fact that the 13B side seals are mcuh skinnier and lack a wedge shape that the Renesis side seals have. The wedge shape is what works carbon out of the grooves and was the reason that the side exhaust port failed back in the 70's. They tried it but found carbon buildup would stick the side seals and ultimately break them. It would run in the short term but not for too long.

 

see, that's why they call you the rotary god!

makes sence.


of course I am sure it would have been done by now if it were possible, but could you machine new side seal grooves into the REW rotors to make them match the RENESIS rotors. (leaving the old side seal groovs empty or filled)

seems like this would be a good idea untill someone decides to cast a new rotor.

 

If the grooves were in the same physical location that would theoretically be possible. They aren't though. You could get them really close though. You might be able to work with the side seals a little bit but you may have to rebend them slightly and definitely clearance them differently. Of course you still don't have the cutoff seals. He are a couple of comparison pictures I took:

https://www.rx8club.com/showpost.php...&postcount=137

 

nice lightened rotor on the right!


if you machined a new groove where the RENESIS side seal would go on a REW rotor, and used RENESIS side seals, wouldnt that be the exact same a a RENESIS rotor, just lower compression like the REW?

you can tell me to shut up at any time. this is comming from a guy that has only built one rotary engine, and torn apart maybe 5 or 6. (all S4 & S5 N/A engines)

 

The problem is that you aren't going to quite have the grooves in the same location. They will be close but close doesn't usually cut it. It "could" work though.

Both of those rotors are lightened. The Renesis rotor is lightened a very small bit internally. The 13B rotor is lightened internally and externally. Neither of those are mine though. I took those pictures at Racing Beat a couple of weeks ago.

 

NICE!


I will take your word for it. I dont see why it could not be in the same place. but I am sure I am simply overlooking something. you know what your talking about. I sure as hell dont.


maybe it would help if I could lay a RENESIS side seal up agains an REW rotor.

 

i have a question about the history of thought on the rotary. It in early 90's when the fd appear for the 3 or less years in the U.S. did many FC owners proclaim that the new twin turbo engine isn't as good as the last generation FC's, mainly the TII's? I would think so due to the engine seal trouble that occured, but i was only 13 to 15 years old during its sale in 93 to 95.

It seems that the fd has such a cult following (mainly by non-fd owners) that its hard to recognize the superior tech in the renesis. Also i believe a quality aftermarket for the FD didn't arise till the late 90's, mainly a new cheap computer for the many owners who thought it was wise to boost over 12psi on a stock CPU (and fuel system for that matter.)

 

but I see *13B* on the engine itself !

j/k

ok, enough jokes. Well I love your post, I learned alot from you.

 

Wait, how exactly does the side seal groove stop you from running FD rotors? Mill the seal groove out and trim / slightly reshape ( if nessicery, I know sideseals can be a little brittle) and your good.


The port interference "Issue" is a non issue if you have the motor appart anyhow, just do a blend/polish/radius on the port closing edge to gently guide the leading edge of the seal back up onto the housing instead of colliding. Engine builders have been doing this for years on "Monster/Super/huge/mega/stage 9/whatever you wanna call your big *** port, streetports" which are ported farther on the opening edge than the rx8, almost the the point of corner seal ingestion.

 

There's one forum member who I believe is using the old 13B-T 8.5:1 compression rotors in his Renesis. Don't know how it's been working out as I haven't seen him post much lately. I'll see if I can find the thread...

Conversely, I think Amemiya tried REW 9:1 rotors and abandoned that project.

 

Even the biggest streetports on 13B's don't open as early as the Renesis intake ports. You really need to see them in person. You wonder how the corner seal has any support at all. Even the Renesis side seal and it's outward position are on the verge of collision with the closing edge. The seal actually does have it's leading edge cross over the open area of the port but there is enough support left that it can't fall in. Anyone who opens a 13B port that early is crazy for doing so. I've seen people do the radius to the closing edge of the intake port. Its ghetto. If you have enough seal support, you shouldn't need to do that. It isn't doing anything for flow either. You can only go so large before you start to make some big compromises. All they do is make the seal to housing collison very gentle so they hope they don't break. You can actually still see the scars. There is long term wear in that area though and most of those guys don't think about that. I suspect they don't really care either. Just because people do it and have been doing it for years doesn't mean they've been doing it correctly that whole time. Mazda has long term concerns.

 

Yeah I'm going to have to go slap Mazda for that one!

 

they should have called it a 13R

1.3 liter RENESIS



Yup for now on, I will call it a 13R. let's see if it catches on!

 

It was technically called the 13B-MSP (multi side port) until the RX-8 prototype appeared.

 

I stand by my 13R...

 

Let's just call it "Bob". "Bob the rotary"

 

"hey what kinda engine you got in that thing?"..... "it's got a Bob."