So heres my question. The renesis, hows it making 238hp(@crack I'm guessing). I've been contemplating this motor in my FC. But that seems like a lot of headache just to be the first one with it. So how about the next best thing, swapping parts

Heres my basic mission. I want a quick naturally aspirated rotary that is still streetable & still reliable for everyday use. Turbo people, hold your spool driven minds for a sec because I know you all will jump on me. But hear me out, my car doesn't need to kill off everything it sees(which seems to be the point of have a turbocharger these days). I don't want or need that right now. Maybe later i'll buy a Turbo 2 & then build it for street cred. But, right now I just need something to have fun with & be reliable. Not to mention i've wanted to build a drifter since I sae Initial D way long ago. Yes, I know most people in that scene are running turbos. But most of them have been in that scene for god knows how long.

I will also be polishing my skills with this car. So it being super fast will do nothing but make me uneasy when that turn comes up at me. As far as numbers go. Over 230 @ the crank would be nice, as long as it wont be too unreliable. I guess this phrase says it all "I want to build a daily drivern drifter". One that can still have some people wondering how they lost to a an N/A RX-7 on the street.

Any replys, suggestions, or ideas are welcome. Any negative replys will be laughed at & ignored. Only because i've explained what I want. Oh yeah, as far as money goes. It's basically dependant on what is needed. This will be my project for the year+. So when I go to Nopi Nationals next year & you see the Daytona blue FC drifting around the track. You know who it is

 

Well, for starters it does not quite live up to 238 HP either. Every dyno chart posted online has been around 180 RWHP, maybe a little more. Even if you could get your hands on a crate motor, it is probably frightfully expensive. You can make 200 HP with a ported 13B and bolt-ons. Is a few more HP worth $3-4K to you?

 

I agree... the RX-8 engine sucks and doesn't make 238 hp. I'd say it's around 210. If you ask me, you should just mod a boring old 89+ RX-7 engine.

 

U can do weight reduction and mod / port an old 86-88 S4 NA engine and spank GT Mustangs . . I've seen it happen at the dragstrip.

 

I read in a Renesis swap thread on here that it makes 238hp after a certain mile. They also backed it up with saying Mazda dynoed it after that specific point & that is what lead to the hp gain from 180. It does kind of make sense in a backwards way.

I can have my motor rebuilt & street ported for $2,050. So $3-4K really wouldn't be happening from my car. My real question is what would be the better parts to go into the motor during the rebuild, as far as performance goes? Like I said, I really don't expect much from this motor. Don't get me wrong, it can perform with the rest(stock) of them. I just want a quicker car. I know opening up it's lungs will be happening. Such as, Racing Beat exhaust from the header back, air intake, large Street port, & after that I really am not to sure as to what else can be done to make an N/A faster. Sorry, i'm still am pretty much new to the Rotary Revolution. But, I am all for it. I love my car even though it's given me problems since I bought it.

If I was to do any kind of serious n/a swap it'd be a 20B. But before that is even considered. I want to understand rotaries completly, as far as internals go. I have the general idea of how the motor works. I just don't know what really needs to be done to make the n/a faster, other than simple bolt-ons.

 

Dude that was a very blunt statement. What personal experiance do you have with the engine?

 

It has a higher redline.


-Ted

 

I'm glad you mentioned that. I was thinking about the Renesis rotors(I hear they are lighter which causes them to rev so high). What are your thoughts on those? Revving higher is something I was shooting for with this N/A build up. Like I said, I want to make around 230hp with no boost.

 

Serious engine builders that I've talked to have told me 270-280 with a bridge, 51ida's, open exhaust, etc.. Scale that down a bit for a streetable car (exhaust mainly), and you could probably expect 250. You'll need to get the harder gears, good bearing, oil mods, rotor clearancing, engine balanced, carbon apex seals. And don't expect it to last for a long time. RPM's in my projected setup are 11,000.

 

Why not try a bridge port instead of the street port if you want that horse power and don't won't the boost. You could also think of lightning the rotors and investing in a lighter flywheel for quicker response.

 

Bridge ports are kool, dont get me wrong, But, for everyday use they aren't to practical. The half & half bridge/street port sounds pretty kool, but I never really have been able to wrap my mind around that. Which one should I have street ported & which should be bridged. I know a guy with a bridge port. He says he has to change out plugs pretty frequently.

I talked about lighter rotors, thats is why I asked about the Renesis rotors. I hear that they are hella light. Which causes them to rev much higher. The flywheel was probably going to be replaced with the ACT clutch.

 

they are light. They are also big $$, and from what I've researched, 5-10hp over 91NA rotors seems to be the norm. Fine for racing, but what do they cost again each?...kinda impractical for the street.

HA! Don't waste your $$ on an ACT or other lightweight flywheel. If you want reduced rotating mass, step up to the plate. Go buy the tilton double carbon disc 5.5" clutch, and accompaning flywheel. I've done the weight calculations on those parts... 14lbs. Thats for the clutch AND the fly!

If you are going to all-out NA HP, I think practicallity goes out the window.

never mind, I just read your streetable aspect of the first post again. Get a good street port, some side-draft carbs, a good header and exhaust, and call it a day. Unfortunatly, I don't think you can have your cake and eat it too.

 

I have zero personal experience with it... all I do know is that on the dyno it really doesn't make much more power than an 89 engine except by revving out another 1000 rpm.

If an 89 and an 04 engine cost exactly the same, I might say give the 04 engine a try. As it is, you can pick up used 89 engines for almost nothing and rebulid them.

Besides, if side ports are so great, why does the 787B use peripheral porting? Why not this fantastic new multi side port? That's right, because the main thing good about it is emissions.

I still say the RX-8 engine is not as good as a modded 89+ engine.



Brian

 

You grossly over simplify. Check out exactly where you have to be on the tach to get big power out of a peripheral port and just how ugly the lower RPM range is...

 

Key word...Emissions.......I will prob get flamed for this, but when Mazda came out with the Renesis Engine, they didnt have high hp numbers in mind, they wanted to build a Rotary that would do well with emissions testing. And with that goal in mind, they did a pretty damn good job. The Renesis is a good everyday, reliable, Emissions passing Rotary......Why it has slightly more HP than a 13b I honeslty dont know, im not an expert on either....my guess would be better sealing, Better compression and maybe something to do with better porting....but as i said, i dont know any of that for a fact...just my 2 cents.

 

Thanks for defending the 13B-MSP. It's a great engine. In fact, Judge Ito has recently dyno'ed the car at 239.7 rwhp. How did he get it? I'm not sure myself. Also, a friend of mine has a nitrous-powered 13B-MSP in his RX-8, and it ran an impressive 13.322 in the 1/4, with 235 rwhp on the G-Tech, which I know is inaccurate (is anything really?). The engine is a great piece of technology, and it has the awards to back it up.

As for better compression, what does that mean? The 13B-MSP is already at 10:1, and the ports are much larger than previous motors. Personally, I don't think there is much to be gained with a street port. A bridge port, on the other hand, would seriously up the power, but will sacrifice it on the low-end unfortunately. For a naturally aspirated rotary that has almost as much power as the REW, especially the JDM motor, I wouldn't be too quick to judge.

 

OK here's what I'm saying... a modded OLD engine is better than a Renesis when you factor in price. If price were no object ... well I still think it's close...

Here's some evidence showing a stock RX-8 from Rotary Performance and a dyno of a modded car I pulled of the forum after a quick search here....

The old engine had the following mods:

Cone intake
Port matched intake
Pineapple 6-port sleeves
Street ported S5 engine
Turbo II rotor housings
RB Header
Bonez High Flow Cat
RB Mufflers
Chipped 1986 ECU - moves fuel cut to 8000 RPM, modified timing
Apexi Super AFC
460 primary - 550 secondary injectors
S5 Turbo II fuel pump.

I'm still running the Air Pump and all emissions. The car is street legal and would pass most state sniffer tests.


*edit* forgot to say the red is the rx-8 and the blue is the modded rx-7. I used photoshop to sort of overlay them. Notice that there are some gains for the rx-8, but if you factor in price... is it worth it?

 

Yeah around 9000-9500... that's close to where the stock RX-8 redlines.... so I still say... it sucks.

 

The renesis gets it's extra power from the two extra ports that open higher in the RPM range.That's how it stays civil down low. It's like a porting that only opens higher up. I think that answers your original question.

 

True, the RX-8 employs tertiary ports that open at high rpm using slide valves. Still, I would love to see someone bridge, or p-port the housing. A friend of mine suggested p-porting the intake, and leave the side exhaust.

 

You guys are still smoking crack...
I don't understand how mentioning NOS has any application in this thread when you mentioned "naturally aspirated" at the same time???

There is nothing fancy about the engine.
It won awards cause THERE IS NOTHING ELSE NEW OUT THERE TO COMPETE WITH.
The 13B-MSP makes more power cause of the higher redline, period (in addition to higher compression and revised manifolds, duh).
The exhaust timing was radically changed over the older 13B DUE TO EMISSIONS.
This also create a little more torque down low, but for all out horsepower (which you guys seem to love to mention), the conservative exhaust port timing CHOKES the engine.

Adding forced induction to this motor will NOT yield greater power gains over the older 13B.
You're fighting against physics.
Producing power with forced induction is all about air flow.
The 13B-MSP doesn't have it.
Don't expect huge gains.

Our 20B NA produced 232hp and 193lb-ft of torque at the wheels (DynoJet) on an unopened block.
With a crappy custom header and a restrictive filter, it made more than 200lb-ft of torque at the flywheel.
I'd like to see the 13B-MSP do that on the stock block...


-Ted

 

2 rotor vs 3 rotor when it comes to torque hmmm... let me think about the logic of that comparison...

 

Hey, I didn't start that; the original poster did...

UnderConstruction7 said...

-Ted

 

Well yeah, there isn't much to gain with an N/A rotary. When Mazda had that RX-01 concept back in the 1990's, their 13B only spat out 220 hp. THe 13B-MSP is 238, in the States that is. My guess is the engine's power is limited partly by it's displacement. Displacement, of course, has much to do with producing power.

Okay, let's neglect emissions and mess with the exhaust port timing. Still, little gain. Maybe if Mazda employed a larger displacement rotary engine, we'd be able to see more power, assuming you're going with the idea of more airflow, which is true. Otherwise, I can **** on my engineering degree.

Ted, do you think airflow is the only thing stopping this engine from producing serious power, especially with FI?

 

This link compares a fresh (1K miles) 89 engine to same for the Renesis engine (800miles).

Are you comparing it to the TII motor or the NA motor since looking at the graph on the page below, the NA version is a lot better than the 89-91 NA motor in stock form. Even with the higher redline, which does make it's final hp number seem high, the engine was making over 50 rwhp more than the 89 engine at it's peak rwhp rpm.

even if the engine isn't making the 238 flywheel mark it is indeed a lot better than the 89 -91 NA motor.

http://rx7.com/rx7rx8comparo.html

Tim