Kiyokix,
When I started this thread, I was not trying to bash mazda just stating that the initial numbers were dissapointing and people who paid over 30K for the car were disgusted. If it was detuned on purpose then how come no mazda dealer could confirm that? They had a special training program for the dealer service techs according to my local dealer and there was no mention of such a thing. Btw, pre-production models also had HP problems and it was attributed to 5 & 6 ports not opening up. These dyno charts do show the ports opening up though.
Man, I really want the renesis to be a commercial success because I love rotaries. But I would not swap it into an rx-7 just yet. I have heard some 3rd gen guys were trying to buy some crate motors for better reliability, that is why I brought it up on this forum.

 

Note: Didn't say anything about larger displacement, just a smaller eccentricity and wider rotors to compensate.

Also note that between the 10A to the 12A to the 13B in the 70's, torque was rising out of proportion to displacement. I wonder why that is.....

 

If that were the case then they would lose 35hp to the drivetrain at any HP level. If you let the clutch out from an idle in 1st gear, does it stall the car and refuse to move? It should, if the 35hp drivetrain loss was fixed. Think about it.

Drivetrain losses are due to friction. This friction converts power into heat. The more power you send through the drivetrain, the more friction there is from forcing the gears against each other harder and forcing the bearings harder, so the more heat you generate and the more power you lose.

About 10 years ago my stepdad (engineer) have me a big gear on a precision bearing, a souvenir from his days with Timken. If you stuck it on your finger and spun it it would spin for MINUTES. I noted this when he gave it to me and I'll never forget what he said... "Yeah, but what about when it is *under load*?"

 

People shouldn't be dynoing their cars with so few miles on them anyways. Got to get them broken in first.

I drove an RX-8 2 days ago. I also drove a prototype car back in January. My initial impressions back in January were that the car had almost no power. It felt like my Civic. I am proud to say that the production car is much faster everywhere in the powerband. It still isn't a rocket by any means but it feels very nice. Anyone used to the turbos on the 3rd gen will be dissappointed but it will still outrun any stock T-II.

 

if you compare apples to apples the torque doesnt rise. the cosmo 10a is 128hp 103lbs ft, a 79 12a is 100hp 105lbsft, and a 74-78 13b is 110hp and ? torque.
the torque rises out of proportion when you add the 6 ports (133hp and 133lbsft) or a turbo

mike

 

Remeber that the early engines back in the early 70's weren't choked by emissions standards that they are now. Power started falling off when emissions standards came along. Torque is directly proportional to horspower so to accurately compare numbers we really need all of the specs to be at the same rpm and with each engine set up identically to the other minus the displacement differences.

 

yeah that wont happen, because its hard enough even finding that and the older engines peak at different rpms(usually lower)

mike

 

Actually the 10A's had peak power at 7000rpm.

The Cosmo 10A's also had no emissions equipment.

Torque is directly related to displacement, HP is directly related to displacement and RPM range. Things like thermal efficiency and volumetric efficiency trim it up or down.

 

Ya'll are forgetting a very important thing.... horsepower is a fictional number. It is a number that is derived from torque mathmatically. Im not saying that horsepower is a bad number but you can make 1000rwhp but if your only making 5lbs/ft of torque your not going to go anyplace fast even at 9k.

 

Um,..........no

5 ft/lbs of torque at 9000 rpm would be 8 hp,..

If you had 1000 rwhp you would be going somewhere very fast, no matter what rpm/torque it occurs at.

Thats why they invented a little device we like to call the transmission. If you had 5 ft/lb of torque, you would need ~1,000,000 rpm to make 1000 HP, now you run that thru your transmission with a 500:1 gear ratio and you get 2500 ft/lbs of torque with a very useable 2000 rpm shaft output to go into the rear end 4:1 sound good? that makes 10,000 ft/lbs of torque, with the wheels spinning at 500 rpm
that gear would be good for 65 mph btw, youd get more effective torque if it was lower.

f1 cars only make about 240 ft/lbs and id say their pretty fast.

HP is not fictional, it is a measure of power, which is work over time, torque is a measure of work alone.

power is a much more useful rating then work, because power is a good representation of how much work a motor can do, where as torque is an instantanious measurement of its rotational force, which would only really be useful if no one had invented transmissions.

 

You're both right.

As the RPM range goes up, your ability to accelerate is increasingly affected by the rotational inertia of the engine and drivetrain. Meaning, if you have two 500hp engines but one of them has less rotational inertia, the "lighter" one will accelerate the car harder. Pull a steady load up a hill, and they will be identical, though, because they both make the same HP.

Power is work over time. Torque is not work, however. Torque is force. Picture this - you have a ratchet on a difficult bolt. Let's say you have a 2' long ratchet on an RX-7 flywheel nut, and you are applying 100 pounds of force on the end of the ratchet. This is 200lb-ft of torque, which is force. But the nut is not turning, because they are complete bastards, so no work is done because there is no motion, so you are putting out zero HP. For an example of work, imagine pushing a wheelbarrow up a hill. No matter how fast or how slow you do it, it takes the same total amount of work to move it up the hill. How *fast* you do it, is power. To move that wheelbarrow up twice as fast, you need twice as much power.

Break the figures down... Torque times revolutions per minute is horsepower. Torque is rotational force, revolutions are rotational distance, minutes are time. Force times distance is work. Force times distance per unit of time is a measure of power. (One horsepower, in fact, is the ability to lift 550 pounds one foot in one second)

This turned out longer than I thought, but I hope this helps...

 

This is the worst subject to argue about EVER! Check this link out:

http://www.stanford.edu/~voloshin/lhowwhy.html

Blake

 

Just to clarify guys we have a Dyno Dynamics Dyno here at Vishnu, not a Dynapack(we don't have a pit crew here or the time to mess with that dyno) You can read about the dyno at www.dyno.com.au. This dyno does read lower than the dynojet by approx 17% in 2WD mode. For Rice Racing the RX-8 made 117KW at the wheels on our Dyno Dynamics Dyno. I am sure that you have used plenty of those back home in Australia.

For comparison a Acura Integra Type R made 153 wheel horsepower, and a Honda S2000 made 185 wheel horsepower with both cars being stock on our dyno. Just wanted to clear that up fella's. Take care guys.


Brett Payne
Vishnu Performance

 

As i mentioned b4 in a previous thread i was going to buy one to have ...but when i drove it it was VERY SOFT...

 

hmmm......that is queer.

 

Yeah well here is my argument.

When are youg guys gonna get over the fact the rx8 isnt a dragger or a sports car? It is a sporty sedan.

Who cares how fast it goes down the strip?It's not made for that.You all sound like a bunch of Honda Accord owners trying to race your 4 door grocery getter.

Now when someone needs to get mad or upset is if the rx7 comes out andit cant even produce 250 hp,280,or 300.

And the only thing that the rx7 needs to compete with is the same car its been competing with its whole life, the Supra.

What i want to hurry up and see is a decked out Renesis Turbo and see how it compares with a 13b-rew.
Please do not say anything about compression being to high. I will slap you.compression can be lowered.

Say for instance a streetported t78 13b-rew versus a street intake and exhuast ported t78 13-msp-re.Seeing as the new engine does not have a peripheral exhuast,not as much heat, but has better "piston like" effeciency. I'm sure the exhuast ports can have different style porting(i.e. street, bridge) for different flow characteristics.You also gotta look at if a huge turbo is placed on the engine, it may not spool the turbo as fast as a peripheral exhuast 13b-rew, but the stock rpm band 2k rpms higher. Plus that is limited by ecu.The stock redline was 10k.More of a power band to play with.

 

They have a DynoJet.

 

I'm not quite sure on the point you were trying to make there, but it wasn't made because that made little sense. The argument at hand is not about what the RX-8 is made for, it's about the evidence at hand which so far seems to point to the notion that Mazda overrated the car and is not making the advertised HP. Now when you go out and spend your hard earned money on something you expect it to work as adverstised no? If you went out and bought a nice receiver and one of the surround channels wasn't working would you not be upset and return it? I hope you wouldn't make excuses like: "well, the receiver was designed for high frequency output and not center channel operation." The fact is that the product DID NOT deliver as advertised, you were persuaded into buying something that was not what you thought.

 

Just to add to the whole mess, somebody drag race a RX8 in PR...

I won't even say the ET, but the MPH at the end were a wooping 86MPH

 

I did better than that with a stock port 12a...it's got to be something else.

 

Wow...86 mph thats pretty strange. Here is what someone got with their gtech.

http://www.rx8forum.com/showthread.p...&pagenumber=18

I really dont know how inaccurate it could possibly be. Even half a second off would still yield the fastest time any magazine got. I dont konw about the 101.4 mph trap speed though, im guessing he would need around 215ish at the wheels? Anyway, some of the other things that it calculated are strange but worth looking at.

nearly forgot...its at the bottom.

 

Well, it's official. Mazda downgraded the hp to 238 BHP. They lied again!!!! I am convinced they inflated the actual HP by 5% or so to arrive at 238HP. They are still trying to get away with whatever they can.

 

Even with 238hp it should still be over 200rw....actually with 15% loss it would be 202rwhp. Thats still 20-30RWhp off from what people are actually getting. If they are averaging 180rw on the dyno that would be right around 210hp.

Supposedly they had to change the ecu's out at the last minute when they went thru customs. Sounds like the 250hp wasnt measuring up to the emmissions standards and they had to change the tuning or something.

STEPHEN

 

The fact that the European spec RX-8 is rated at 228 hp in the latest Evo magazine from England should be noted. If the RX-8 is making 175 wheel horsepower on a dynojet dyno and 157 wheel horsepower on a dyno dynamics dyno then this leads me to beleive that the car is only delivering around 210 horsepower to the flywheel. 115 pound foot of torque at the wheels at 6300 rpm is not very impressive either, and certainly not what was quoted by Mazda.
Overall Mazda has once again screwed the pooch and the fact that they are not offering to fix the lost horsepower and once again throwing $500 to owners is quite pathetic. What happened to the 280 horsepower this motor was making in pre-production cars? Thank goodness the new RX-7 will have a 1.6 litre motor as it is "rated" at 300 horsepower. Perhaps that motor will make the 250 horsepower this Renesis is rated at.

But we will probably never get to see the RX-7 as the RX-8 will likely die a quick death because of this scandal. The 6 speed RX-8 is not making 250 or even 239 horsepower, but 210 just like the automatic. That is unacceptable and Mazda should find the missing ponies. Or tell everyone that it made a huge mistake and drop the price $5000 and try to sell it as a 210 horsepower car. That would at least be honest.

Brett.

 

Does anyone know what the RX8s in Japan are doing?

Remember that the Japs have 100 octane fuel on the pump, would be very interesting to see what they are up to....