Renesis and rx7 FD 13B Hybrid engine
 

Recently in North Borneo we had a 4AT rx8 blown. since i am the representative of the RX8 Club Malaysia in North Borneo, of course i tried to source out engines and options with the lowest price.

But i had a Problem, The Owner insist to put back his Bolt-on Greddy Turbo kit. Which according to many parties that, the turbo was the reason that cause the engine blow in hot climate in malaysia.

After a lot of searching, we found someone in japan who can supply a Hyibrid of 2 13B engine.

REASONS:
for this assembly is because it could provide a realiable 13B engine that is suitable and sustainble for a turbo.

ASSEMBLY:

Front Engine Housing (1)
Renesis 13B
+
Rotor and Rotor Housing (2)
RX7 FD 13BT rotor and housing with special Apex seal
+
Mid Engine Housing (3)
Renesis 13B
+
Rotor and Rotor Housing (4)
RX7 FD 13BT rotor and housing with special Apex seal
+
Rear Engine Housing (5)
Renesis 13B
+
Side Seals & O-Ring
Fix type without spring (not sure whast this)

UNCERTAINTY:
1. How they put this 2 engine together, since the gasket is not the same.
2. Side seals type and source.
3. how would the injectors fits.
4. They promise 1 bar boost, could this be possible on rx7 FD engine? and realiability on RX7?

THE COMPANY that offers to do this:
http://www.topfuel.info/

***I would really appriciate if anyone with answers and more info to post here***

UNCERTAINTY:
1. How they put this 2 engine together,

It seems impossible to me, the FD rotor housing has a peripheral exhaust port.
Atleast he won't be able to put the Greddy kit back on, the exhaust is in the wrong place!
....but they claim to do it, ask them. Why ask anyone else?

S

Cause this is where RX8 tech comes in. but thanks for the feedback though, its important cause we now know the exhaust port is on the rotor housing for FD engine.

By the way, just to input more info, we had a guy here had 2 engine blown after bolt on turbo, what he did was deepen the compression area on the rotor, he had no problem then til now.

I actually had this idea about a year ago. Using the fd rotor housings and the renny end plates. From what i understand the housings will match up. The point was to fix the exhaust ports. However i didnt plan on blocking off the renesis exhaust ports. It would run both renesis and fd exhaust ports and they would be unported or ported very little. The 6 intake ports from the renesis would be ported fairly heavily due the fact thet the renny ports are the only intake ports. I didnt figure the rotors out because fd rotors dont gel with the renny housings. I was hoping for some after market rotors. The exhaust manifold would be composed 5 pipes which obviously lead to a good size turbo. I would really like to see this vision running. I hope someone can find more info about it cuz it sounds kinda like my vision.

Red_Devil, thanks for your precious info.




mike1324, this really clearify most of the structure. Thanks a lot.

Use a 84-85 13B rotor housing, that will solve the soft seal issue, Pre 86 had their coolant seals in rotor housings like the 13B-MSP (renesis) engine.

I don't want to bring this back from the dead, but what keeps you from using rx7 9.0 compression rotors in a renesis .... you just need to rebalance the e-shaft and then you are good right? .... I know people use the lighter rx8 e-shaft in some rx7 rotors, they just need to rebalance it.

If you intend to keep the exhaust side ports you'll have to use Renesis rotors due to the required side seal setup.

Several companies can add the coolant seal grooves to later 13B rotor housings. Guru Motorsports down under is one that comes to mind.




.

Citation needed.

:dunno:

Sorry, I don't school n00bs in Renesis 101 basic facts

try searching Renesis side seals, there's a reason they were changed from the 13B side seals

He's not asking for schooling , he's asking where you got your information (in case you just pulled it out of your ass). Big difference.

Help us out, man. ;)

The RX-8 rotor can be modified to accept the 13B 2mm apex seal and by using the RX-8 rotor I was referring to the entire seal configuration on the sides. The compression is only an issue for very high boost FI applications.

No I'm not trying to be an ass, but if you want a citation go to Wiki. Otherwise the seal configuration relative to the Renesis rotor and side exhaust ports is very basic info. I'm not going to respond to prove it requests over such basic info.

it's an issue for every boosted rotary application. take it from someone with 8.5:1 rotors, it makes a huge difference in reliability. there's a much bigger margin for error in terms of fuel quality or human error.

I can run almost 17psi on a good sized turbo (T04R) running the same ignition advance that a typical Renesis is running at 7psi. It's not that more ignition advance is always the best thing, but it shows how much more forgiving the low compression rotors are. And it doesn't affect spool much, proper turbo and manifold choices are the key to that besides tuning.

That's on normal 93 octane, no methanol injection, preturbo EGT's over 1700 degrees yet no detonation problems.

if you are running highish boost, first thing to do is lower compression .. I dont care if you have a push rod, a four banger, or a rotary ... once people figure out how to do that, renesis engines over 400 hp wont be a novelty anymore


TEAMRX8, thanks for the response nonetheless, I am still noob at the more specific things


Also, could a temporary solution be to make a late closing intake port so that it closes somewhat into the compression stroke resulting in a lower compression ratio be a valid idea?

It's an issue, but one that can and has been addressed through setup to some degree. It ultimately depends on how much you're going to push the boost/engine output. Beyond a certain HP limit is uncharted territory for the Renesis. That doesn't mean it can't be done, it's just uncharted territory relative to the history of the 13B.

The below was taken from two RotaryGod posts on the subject.

The rotors themselves are the same physical size. There are some diferences with the seals though. The Renesis rotors have a cutoff seal in between the side seals and the oil control rings that the 13B's do not have. The shape and size of the seals is also different between rotors. Due to this fact the RX-8 rotor can be used in an RX-7 but not the other way around. You'll just have to trust me on that one. The casting thickness of the RX-8 rotors is also thinner than the 13B which makes them less strong but lighter. I'm not sure where you can get any dimensional drawings. I'll start digging.


While they will physically fit, the RX-7 rotors do not have the cutoff seal that the Renesis rotors do. As I learned from Ray's motor, this seal is in place to protect the oil seals from exposure to direct heat from the exhaust. Without these seals, your oil control rings will fail prematurely. Who knows how long that may be but these seals were added for a very good reason. I personally would not use a 13B rotor in a Renesis for this reason.

Uh yeah, let's just cut out the baloney and go to the source

http://www.rotarydevelopment.net/Rot...790_Rotary.pdf


.

Hey, all I asked was why it will not work. :dunno:
I really did just want a reason why it doesn't work. :yesnod:

great article !

OK, I have checked with my builder and was given the OK to let the cat from the bag....

I AM running low compression RX7 rotors in my Renesis.
Rotary god is also correct that this cannot be done without the RX8 gas control rings.
The rings slots were machined into the FD rotors.

Running the 12 PSI Pettit pulley, now results in 10 PSI boost, the engine is smooth and pulls HARD.
I have not dyno'd yet, until I can get tuned properly, as I am still running too rich.


Sorry I could not tell before, but it was/is a prototype.

Yes, Cam.
Why would you say not Cam?

:icon5:

Was making a guess based on previous conversations between myself and him. Either way, pretty cool. Can you give any further details - how many miles or how long ago was the engine built? Any plans to up the boost?

Very interesting . So you now get lower boost on the same pulley ?

Awesome. :mdrmed:

Lower boost; from more chamber volume is a guess.
MAF numbers look good though, and not really pushing it yet.

One more thing, the engine runs much cooler, I thought my fans were broken when I first started driving it.
I can drive it hard, stop, idle a minute, shut down and the fans just run a second and turn off, they used to run for a while.
I barely get over the thermostat temp.

/\ similar maf numbers or is it higher ?

would be very interested to see the effect on a turbo engine .....

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.

:beer05::beer05::beer05::beer05:

Wat engine management are you running?

Billet Aluminum Low Compression Rotors
 

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

http://img11.imageshack.us/img11/1684/img6454.jpg

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

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 ...


.

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.

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

any more updates on this???

what he said

^ what both of them said

what seals did they use - stock or aftermarket ?

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

lmao

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

we'll start here.


this is wrong

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.

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.

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.

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.

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???

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?

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!

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.

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.

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