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Dec. 24, 2010 9:25 a.m. ReverendDexter SuperDork

Okay, pardon me on this as I drive a Mustang

I was looking at some dyno charts for RX8s online, and, while I know that power isn't everything, it really shocks me how low the power output of these cars is. The charts I saw are showing numbers like 148hp/112tq at the tires for stock cars... how is that possible? Even the really, really good runs for stock cars weren't pushing 150/120 at the tires. That, and the at-the-crank numbers are around 230hp... how is there so much drivetrain loss? I mean, I just dyno'd my 5.0, and with VERY light modification (cat-back, K&N, synthetic fluids) it's putting 194/269 to the ground, and peak power is at a crawling 4200 rpm.
I understand the torque being low, it's a 1.3L N/A rotary engine... but isn't the point that you can wind those things to the moon, and with all those extra firing events per revolution (3events/rotor/rev vs 1event/2pistons/rev), shouldn't it at least make a better horsepower number than my 20 year old truck motor'd behemoth?

Just based on those numbers, it seems like RX8s would get spanked by MX-5s around a road course. What am I missing?
Dec. 24, 2010 9:29 a.m. John Brown SuperDork

I dream of an RX8 with a 3.7L 2011 Mustang V6 engine and transmission.
Dec. 24, 2010 9:39 a.m. rotard New Reader

They usually dyno closer to 190hp at the wheels. They also have very broad torque peaks, which helps make up for it. The coils are a weak point, and cause all sorts of losses when they degrade, such as: fouling plugs, ruining cats, killing fuel economy (or lack thereof,) and power. I also remember reading about how the stability system in the car will activate on a dyno, since the rear wheels are spinning so much faster than the front wheels, effectively throwing the reading way off. I'm not sure how true this is (internet hearsay.) The early automatic cars had 4 port engines with 4 speed (i think) transmissions and much less power. The manuals and later automatics (6 speed) have 6 port engines and much more power.
Dec. 24, 2010 9:42 a.m. T.J. SuperDork

"C Stock: This is one of the more confusing of the stock classes and it just got 100% more full of BS... Nobody thats ever driven a Mazda RX-8 can possibly understand A) How a car with 14.77 lb-ft. of torque can be that much faster than the 350z, B) Why nobody can beat that Isley guy C) How they convince their tire guy to spend an entire workweek mounting those Kumhos and D)Why SCCA would allow a class where two different Mazdas can win. That's just bad business. Also, if your car has ever been referred to as a "Girl's Car", this is where you belong. "

(quoted from here)
Dec. 24, 2010 9:48 a.m. pilotbraden Reader

I have never put mine on a dyno but it pulls pretty hard. I am happy with it. The automatics also have a lower rpm redline. Perhaps they also limit rpm due to having only 1 oil cooler on the automatic. Anyone that wants to drive mine can.
Dec. 24, 2010 10:03 a.m. ZOO Dork

I have never, ever been bored with the amount of power or its delivery in any RX8 that I've driven.
Dec. 24, 2010 10:37 a.m. rotard New Reader

You would think that this demographic would love the Rx8. They offer outstanding performance for the price you can pick them up at. It's almost like a Miata on steroids.
Dec. 24, 2010 10:46 a.m. JtspellS Reader

I love every minute i get to drive one, but i would really like to see a renesis out of the car on a dyno than back in the same car just to see numbers.

Now you can all ways boost it and have some more fun........
Dec. 24, 2010 10:57 a.m. Weedburner New Reader

ReverendDexter wrote:

Okay, pardon me on this as I drive a Mustang I understand the torque being low, it's a 1.3L N/A rotary engine... but isn't the point that you can wind those things to the moon, and with all those extra firing events per revolution (3events/rotor/rev vs 1event/2pistons/rev), shouldn't it at least make a better horsepower number than my 20 year old truck motor'd behemoth?
If you were counting rotor revolutions, yea, 3 firings per rotor per rotor rev. RPM numbers are typically crankshaft or eccentric shaft rpm. What most people don't realize is that on a Mazda rotary, the only thing going "10,000 rpm" is the eccentric shaft...the rotors are only doing 1/3 that speed. 10,000 rpm from a rotary is not so amazing when armed with that info.
Dec. 24, 2010 10:59 a.m. pilotbraden Reader

In reply to rotard:

Well said. It is one of my favorites.
Dec. 24, 2010 2:01 p.m. Nitroracer SuperDork

Someone in a local club has an RX8 daily driver that he took to the dyno with some disappointing results. Poor car has had issues with coils, compression, catalytic converters, etc. And the guy doesn't beat the crap out of it either. Still looks and handles great though.

150hp/120ft-lbs
Dec. 24, 2010 2:34 p.m. JohnGalt Reader

Weedburner wrote:

ReverendDexter wrote:

Okay, pardon me on this as I drive a Mustang I understand the torque being low, it's a 1.3L N/A rotary engine... but isn't the point that you can wind those things to the moon, and with all those extra firing events per revolution (3events/rotor/rev vs 1event/2pistons/rev), shouldn't it at least make a better horsepower number than my 20 year old truck motor'd behemoth?
If you were counting rotor revolutions, yea, 3 firings per rotor per rotor rev. RPM numbers are typically crankshaft or eccentric shaft rpm. What most people don't realize is that on a Mazda rotary, the only thing going "10,000 rpm" is the eccentric shaft...the rotors are only doing 1/3 that speed. 10,000 rpm from a rotary is not so amazing when armed with that info.

But you can't fill a 6 inch tachometer with 3333 rpm so we get this

and no one is the wiser.
Dec. 24, 2010 3:15 p.m. ReverendDexter SuperDork

Well, in the rotary's defense, if the eccentric shaft is turning 10k rpm, doesn't that mean that the flywheel, clutch, and transmission input shaft are all turning 10k rpm, too?
Dec. 24, 2010 9:30 p.m. Rufledt Reader

Yeah i've never been dissatisfied with high rpm power of my RX-8. 3k rpm is a bit weak, but it pulls pretty good from 5-9, and extra hard the last 2k RPM. I was quite surprized a 3k lb car with only 230hp could accelerate as fast, too. It just keeps wanting to rev and accelerate. so strange, it taunts me to find the redline beeper constantly. That evo never did that, and neither did the challanger srt8, or the genesis coupe, or the 370z. that's why i got rx8.
Dec. 24, 2010 11:21 p.m. nderwater HalfDork

The RX-7 is one of my favorite Japanese cars ever, but I've never really felt anything the RX-8. The fit and finish are nice, but exterior styling is... polarizing. Having flogged an RX-8 on the street and autocrossed an RX-8 back to back with a Miata, I just can't agree that the car's handling is that remarkable. The Miata is much more tossable and rewarding at the limit, and on the street there are too many other cars which I felt were more compelling to drive - some while also being more practical.
Dec. 25, 2010 8:56 a.m. belteshazzar SuperDork

The RX-8 is just so hideous. And I even like ugly cars.

I'd really like to see more renesis swaps into other cars. Is there a reason you do not find them put into FC's and FB/SA's?
Dec. 25, 2010 9:31 a.m. mistanfo SuperDork

I just wish my head weren't tilted forty-five degrees to sit in one. Then I might be qualified to offer an opinion on it's driving dynamics.
Dec. 25, 2010 9:50 a.m. Rustspecs13 New Reader

You dont see a lot of renesis swaps because of all the issues. And the complexity.

Ive heard they can make really good HP fully tuned (like 250-300 in racing trim), but at that point they have pherphial sp? intake and exhaust ports insted of coming in the side like stock and they are highly modifed. IE not much is stock.

The only thing thats really desireable out of them is the high compression light weight rotors. And even then its only .3:1 higher and slightly lighter.

Its cheaper and easier to get performance out of a basic single turbo 13b or built NA's. Then again my friend/boss has 230+WHP 13b in a FB, and a 423rwhp NA 20B in an FD. So, im kinda jaded.

Nitroracer- they actually need to be beaten on regularly. Thats part of the problem.

~Alex
Dec. 25, 2010 12:29 p.m. wlkelley3 Dork

belteshazzar wrote:

The RX-8 is just so hideous. And I even like ugly cars.

I'd really like to see more renesis swaps into other cars. Is there a reason you do not find them put into FC's and FB/SA's?

I guess it a matter of who is doing the beholding. The none car guys at work like the looks of my RX8. They think it's a nice looking car. I think so too but maybe I'm biased.

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