The shape minus the blips is about the same but it slopes down a little bit starting at 6000 RPM and it is not supposed to. This is why it doesn't make all the power it should at 8500 RPM

Not everyone knows that the HP curve is derived from the torque curve by the equation:

HP = RPM X Torque / 5250

where torque is in lb-ft. (This is also why the torque and the HP are always equal at 5250 RPM.)

It is the upper RPM HP that 1stRX8's 8 is missing. Hopefully that will be returned as time goes by.

-Mr. Wigggles

Considering the comparible results between the two dyno runs, I doubt that there is anything wrong with either dynos. It's very consistent.

For all we know, the DSC might not be completely defeatable. But at the same time, I would think that the car wouldn't have gotten THAT much power if the DSC was trying to hold it back for traction reasons.

I don't think it's a matter of the engine putting out less HP than advertised. That's a huge chunk, and Mazda has already been burned by some 5 hp in the 2001 Miata. It is highly doubtful that they would try and cover this big of a deficit. Like someone already pointed out, they decreased the rating from 250 to 247. Why mention a 3 hp drop when there is a 30 some hp drop?

Engines still need to break in, but I've noticed that many cars nowadays "don't require" a break-in period (not just the RX8). Customers are told to "drive it normally". The contention that the ECU is tuned differently until the car reaches a certain mileage makes perfect sense. Imagine how many customers nowadays wouldn't be responsible enough to break-in the engine. Putting such a setup in the ECU will protect the manufacturer from warranty issues down the line from an engine that is run too hard too early.

That's my take, anyway.

---jps

Sputnik,

To clarify, they did not decrease the rating of the actual engine output power from 250 to 247.

The presskit says 250 PS

250 PS (international Horsepower) = 247 HP (American Horsepower)

So the car is still speced at what the press kit says it is, they just put the 250 on the US site in error since we have a different definition of horsepower.

So it is semantics. They didn't decrease the rating. They changed the units of measurement from one type of horsepower to another

-Mr. Wigggles

That sounds like a good theory. But surely the break-in would only be about 1000 miles or so. And Mazda would be keen to make this fact known, otherwise they would get car magazines testing new cars and publishing poor performance figures, which could hurt sales. We should be able to get confirmation from Mazda on this if it is true.

Alright,

I just got back from test driving the RX-8.

When a car has predominantly flat torque curve, the car will accelerate (g's) at uniform rate while in the same gear. (wind resistance is only a considerable factor at 60 MPH+)

Well anyway that appeared to be true from say 4500 RPM to 6000RPM. But from 6000 RPM to redline, I didn't get as much "kick" as I was expecting. Power was increasing but not at linear rate that would allow for g's to remain constant.

Bottom line: I think the dyno is for the most part correct. The car is missing some of its top end power. I would say about 10% or so. (it might be missing some low end power as well but not as much)

The test drive was a blast but I had ridden in one of the RX-8's at Rev-it-up and it seemed faster and that was with two soccer moms in the back seats (screaming their heads off like they were on a rollercoaster).

I'm with Yaw Power, the car is detuned for whatever reason and hopefully it dedetunes itself in a few more thousand miles.

-Mr. Wigggles

i would also agree with this,i work with hi pref toys (watercraft,snowgos,motorcycles,etc)and most all manufactures of these toys do the same thing.retard timing curves 4 to 6 deg for the period of 10 hrs.this is to allow proper break in time cause customers will just hammer on these toys from day 1.i hope this is the case with this car too.

Yes, I've seen people say that. But way before the numbers were "officially" released, even before the Detroit Auto Show days, we were told 250 HP. And while even that was admittedly a "target" or "estimate", my point was that they did "split that hair" between 250 and 247 HP.

---jps

To help illustrate the point of my previous post, note the air fuel ratio below 4,000 rpm. The engine runs quite lean for mileage purposes.

When you drive the car you can feel this quite clearly. The motor really wakes up at about 4K.

Don't worry guys! All is well in Mazda's engineering department.

Paul Yaw
Yaw Power Products

The Gsl-se motor had the smallest 6-ports made. They closed 10 degrees earlier, and had ~30% less area then the second gen's 6-port motor. The renesis has (suposidly) 30% more area, and probably stays open a little longer than the second gen. It can also be seen in the fact that they open around 6k insted of 4k rpm. Not to mention, that at 9000 rpm the motor has much more air demands then the gsl-se at 6500. Also 1 ftlb of torque is worth 1.73hp at 9000, where as its worth 1.3 at 7000 youve got a HUGE differance between the two.

Also the blips are not changes in the map. Map changes would be instentanious, and show up on the A/F curve. All of he renesis's variable intake path and 6-port actuators are electric, actuated by the ecu, which is why the blips occur at the same rpm allways. they are also mechanical, which explains why they take a fraction of a second to engadge, and arnt instentanious lke a map would be. Also im pretty sure you cant get at the 6-port actuators on the renesis unless you pull the intake manifold. And i believe the actuators on the gsl-se were pressure actuated, not vacume.

Intrestingly enough, Mazda 6 dyno's look exactly like this - all the torque is there but the car runs too rich up top and is missing a good 10% of its power. So either the TC is not fully turning off (the 6 doesn't have DSC) or there is some software fuel mapping issues... given both the cars do the same thing, I think Mazda is limiting power for the first couple thousand miles.

The "switch" has been talked about before

http://www.rx-8forum.com/showthread....o&pagenumber=6

FRICTION
 

EVERY NEW CAR AFTER A REASONABLE PERIOD OF TIME, SURELY PERFORMS BETTER, PRODUCING A SLIGHTLY BETTER HORSEPOWER AND FUEL CONSUMPTION. ALL THIS HOWEVER APPLIES TO THE TYPICAL FOUR STOKE ENGINE DUE TO THE REDUCTION OF FRICTION BETWEEN THE MOVING PARTS OF THE ENGINE. AS WE ALL KNOW THE ROTARY ENGINES HAS VERY FEW MOVING PARTS AND MUCH LESS FRICTION SO I REALLY DON’T THINK THAT THERE IS GOING TO BE ANY SIGNIFICANT IMPROVEMENT AFTER 10K OR 20K OF MILES.

Re: FRICTION
 

...but also, it doesn't take 15hp for me to turn a piston engine by hand ("moving parts"), 'cause i can do that by hand

Re: FRICTION
 

Who said anything about friction? We were talkign about ecu maps. And pistons make more power because the rings are seated after break in, the same goes for apex/side seals to a certain extent.

P.S. Please press the little key on the far left of your keyboard, three up from the bottom. Thank you.

Re: Re: FRICTION
 

ROFL! :D

BLAHAhHHAhhHAHAHAHAHAhAAHahAhahAHahAHHa


wak, what were you talking about with the 15hp by hand thing?

excuse the weridness of my post, i'd litterally only gotten up (groggily) 3 or 4 minutes before i posted that...

what i was referring to was the internal friction of your average engine, while it reduces after break in probably some very small amount, doens't equate to the (sometimes) large difference in power pre-and-post break in... the amount of friction is low enough that anyone can hand-turn a crank.

Ya know, *if* the ECU is holding the engine back during the break-in period, and is causing the over-rich situation that Paul mentioned to help with the break-in, then that might make up for some of the poor mileage that the owners are reporting.

---jps

Where's Bern and Rotarynews.com? Maybe he can rattle a few cages at Mazda and ask them. I would guess he would be one of the best people to ask..

I only have 263 miles on the car but the lower lip of both exhaust is already black. That's rich.

Same here.. Getting ~ 15-16 mpg in the city and I have ~700 miles on the car.

I think when the 3rd Gen RX-7 crossed the 20k mark it would switch to a more aggressive the fuel map. Again, I not sure.

I have put almost 700 miles on the car and noticed how black the exhaust has turned as well.

I have also heard that the loss of power is due to the ECU and the car running very rich but that the Mazda USA guys haven't been able to tell anyone when the ECU is scheduled to change the fuel mixture, or any other details about the mapping.

Is it possible for one of our Japanese or Asian forum members to see if they can get more detailed information out of Mazda Japan?

I am not as active in the forum as most of you so I am not sure which members we could ask?

The ECU issue may be concerning if you think about the aftermarket companies that may be developing parts. I may be incorrect but wouldn't some of the products being developed potentialy have design issues based on the fact that the fuel ratio is not optimized or may change when a certain number of miles are put on the car?

Those of you that are more technical tell me if this should even be a consideration?

Remember when T2's came out. Somebody did a long-term of it. New it did 0-60 in like 6.7 ... then after 30,000 miles it did it in 6.3. Still, that dyno chart is a little disappointing. That's a lot of lost power from conservative mapping.

Somebody needs to buy one and rip out the ECU, go full stand-alone. Then see what it can make! :D

i went 2 englishtown
 

ok i was at raceway park in NJ at a drifting race today. Damm there was alot of rx7s and alot of mazdas.there was about 3 3rd gen rx7s and like 15 20 1 gen and sec genrx7s. But no rx8s well hopefuly soon.

Now at raceway park i talked to alot of rotary peeps and mechanics and they said that with rotarys it takes them longer to reach ther full potenial meaning hp # it takes more miles to reach full compression. And they also said that the fuel mapping sounds correct that after a certain amount of miles it will make its true power.

ps. this is what people told me it can be true or can be false just dont flame the messenger:D = me

Re: i went 2 englishtown
 

i was kinda thinking that the rotary might just take longer to get worn in and produce it's correct power, maybe less friction is the suspect or the ecu or both, but i'm honestly saying be paitent with it