I would love to try. I can drive a compny car while mine is being worked on. Where, When, How much?

Because people want to see what the engine makes at a engine dyno with the US spec ECU and the emmisions equipment and to compare it to the 238hp number Mazda North America is giving now. The japanese engines may make 250hp run by the Japanese ECU or aftermarket ones but this is another story

THANK YOU!!! Now we are getting somewhere. We could see if we can get one of our members in Japan to talk to their dealer about getting one and then getting it shipped over here. Finally somebody is wanting to take some action to find out exactly what the problem is. Lets get the US spec RX-8 out of the hospital and see what it can really do. :D

Edit: Ohh ok i didnt know about the ECU Still governing the engine on the engine dyno...lets get a JDM ECU over here and put it in somebodies car....great idea

So the dynographs at the beginning of this thread show 170 hp at the wheels.

The closest car mechanically to the RX-8 is the Miata. The current Miatas have the same gearbox as the RX-8. Probably a bit different (gear ratios, etc.) but it is the same unit. RX-8 has driveshaft probably lighter than the metal one in the Miata. The rear ends are probably comparable too.

Miatas dynoing 170 hp at the wheels make about 196 hp at the crank. It is about 26 hp drivetrain loss at these power levels. Miata builders have pulled out engines for engine dyno sessions and compared them to the wheel hp to come to this 26 hp number for this power levels - so is not a guess.

You probably can assume that the two 6sp MT RX8 whose dyno charts were posted in this thread are making 196 hp at the crank neighbourhood which is far away from the 238 hp announced.

I hope with the miles when engines get broken in, they will gain the missing ~ 40hp to 238 hp, but who knows ...

Something I realized...
 

Most people here seems to think that the last dip in power and how crazy it gets at the top end is due to the third port opening. I think different. Look at the dyno plots, the last dip in power (which is never recovered) occurs around 7300 rpms. Thats when the fresh air duct and the variable intake valve open changing the resonance of the intake. It seems to me that there lays the reason for the drop in top end power. Why? I don't know. Maybe the K/N intake gets its 16hp gains because of this.

Re: Something I realized...
 

I wish this were the case. I have tested the system without the variable valve and just straight open with direct fan air and it almost laid down on top of the stock graph.

Re: Re: Something I realized...
 

You're talking about the fesh air duct on the airbox right? The variable valve is part of the intake manifold and opens at the same time as the fresh air duct, its purpose is to shorten the intake lenght causing a change in resonance for the high rpm resonance supercharging effect. Maybe it's not working as it should.

no the sticking port valve was an actual verified problem with pre-production cars. this is no lie. the lie here is when you say the cars were all getting awful performance, which can be proven a lie by just reading the pre-prod test articles, for instance the ones written by dan and bern from rotarynews.com after the ran the cars at the laguna seca event.

Re: Re: Re: Something I realized...
 

yeah this struck me earlier. the tertiary ports openat 6250 its the variable valve/fresh airduct we're seeing there. so lets try some more logical speculation here with some of our more engineering minded forum members. how could the stateside emission parts effect the resonance tuning on the intake side and if it could what would that effect be.

Does anyone here know for sure if the j-spec rx-8 is indeed putting out 250 hp or is it just "wishful" thinking?

Turbo SE
 

That is an EXCELLENT question!!!!! Mazda??? The clock is ticking.....

Re: Turbo SE
 

Some of us have been trying to find a Japonese contac twho has had a dyno run on theirs.
Unfortunately the guys on this forum in the Asia section all seem to be from Singapore.

in regards to the Japanese Spec Dyno Data Sheet
--- Re Amemiya ran one for the exhaust which can be seen in the Autoexe and Re Amemiya article someone posted not long ago. It shows the dyno graph of the horsepower.

I dont know about you guys, but I think the RX-8 is damn fast and doesnt feel like 190whp... I've floored it and gotten to 94 mph before I even got to fifth gear... I mean it rockets up there like no other!

I'd have to agree. Some cars may dyno far better than others. Currently, some owners are getting 13 mpg while others are getting 19+ all the time (see my sig) I think it's safe to say that some cars have broken in better/faster than others. I am considering dynoing my car, just to see if I lucked out somehow. My car is very powerful, and "economical."

What someone needs to do is:

a. Get a S-afc, see if it works with the rx8, and try leaning it out. Most NA FC owners should have one. If it doesnt work, firgure out a way to mess with the mixture somehow, be it by modifying the hot wire afms output, or putting a resistor on the air intake temp sensor that make the car think its 150 degrees out.

b. disconnect the vacume/pressure/electrically actuated solenoids that control the 6-ports, and the VDI(for lack of a better word ill use the fc3s termenology, (thing that opens at 7250 rpm)) and dyno the car with both closed, then with just the 6-ports, then with the 6-ports and vdi, and then with just the vdi., compare them all and see where they stand.

c. Dyno a motor out of the car with full exhaust and intake to see where we really are on power, then take that to mazda


Does anyone know if the 6-ports have there own separate intake track, and if the preproduction cars did or not? I seem to remember the preporduction cars having 2 sets of throttle plates, one for ports 1-4 and another for ports 5-6. Is it true that the current production rx8 is 1 throttle plate? If they siamesed the 3,4,5 and 6 ports together into one intake track to allow for the single throttle bodie(cost cutting?) the intake manifold would have to be completely redesigned to keep the tunning right. With siameased ports the intake would have to be longer to be tuned for the same RPM, the VDI effectivly shortens the path, which could be why were seeing a power drop when its opening. But we wont know untill soemone tests the car with it closed and sees if we pick up any power.

I'm going to guess that without the vdi open, but with the 6-ports open the motor will dyno the highest. However, the engineers at mazda would have had to have been really dumb to overlook this, so its still just a guess.

Re: Something I realized...
 

At the risk of stating the obvious, something is limiting flow in the Renesis. Based on the dyno graph provided by neit_inf, we can see than no additional hp is gained above 7,000 rpms -- in fact, the hp curve is essentially flat (barring the drop due to the intake valve operation), and TQ continues to drop. This is exactly the same kind of dyno curve one would observe on a turbocharged motor when the turbo was "maxed out," that is, out of mass flow.

Becuase hp is proportional to air mass burned, we know by observing the graph, that from 7000-9000 rpm the air mass being processed by the engine is constant, even though the motor is sweeping significantly more volume per unit time at 9000 rpm than it is at 7000 rpm. In other words, the VE of the motor is falling rapidly above 7000 rpms.

The is interesting becuase I expected the Renesis to breathe extremely well above 7000 rpm -- in fact, that's how I figured Mazda would get 247 hp out of a small NA motor that runs relatively low combustion chamber pressures (as is evident by the low TQ output of the motor). But instead, just as the motor is reaching the point where it would really start making power, breathing suffers, TQ falls, and hp stays constant.

So the question is, what's limiting air flow through the Renesis. Perhaps a poorly constructed airbox, an incredibly restrictive exhaust, or a more fundamental problem with the intake system or port design. I simply don't know. Hopefully Mazda will be able to identify the problem, and find the missing hp instead of further revising their advertised hp rating, which is still FAR too aggressive.

FWIW,
-Dave

RX-8 has to be 190-200hp range
 

As a previous RX-7 owner I was dying to get my hands on an 8, no longer...

There is absolutely NO WAY the RX-8 produces 238hp. There have been a couple of other dyno's posted here: RSX and miata. There should only be around 30hp driveline loss. RX-8 should be producing dyno's of just over 200hp, not 170's.

Here's more fuel, check out this dyno of a 2002 C230. 192hp manufacturer advertised, results in 167.9hp. 24hp driveline loss.

The top number of 197hp is from a simple supercharger pulley change (couple hundred bucks). Tuners claim 235hp, so if Mazda claims 238hp, dyno's should be doing high 190's or 200's not 170's.

I'm sad to say with all this talk of low HP numbers, I think I'm keeping my Benz C230. I still got my back seats + RWD + I get GREAT mileage (35 mpg highway)

I think Mazda is getting a black eye blowing all this smoke and mirrors.

Does it look like ignition break up after 6250 to anyone else?

also someone please pull the vac line, or plug to the valve that opens at 7k, not the fresh air duct, but the actuall manifold tunning vaslve, and then dyno.

OK, I am out of here.
I just looked at the Mercedes Canada site.
C230 Kompressor ( supercharged) coupe.
6 speed, 189hp
As mentioned, a $200 fix to get 235hp
That's more than our RX-8 by about 15-20hp
$34,450 Canadian

With anti-theft, bi-xenon headlights, leather wrapped goodies, Bose stereo, Evolution package ( wheels, skirting, etc.)
$38,905

That is $1,000 change on my 8, and by the time I add the upgrade on the blower and a few minor things it ends up the same price.
A heck of a lot bettter retention of value.

Or, for about $3600 more you can get the C320 sport coupe.
Same stuff, but V6-215HP, 221ft.-lb. of torque, etc.

And what else do you get from Mercedes?

Integrity.

Re: Something I realized...
 

I'm also with you on this. The rotary engine is exceptionally similar to a 2 stroke engine in regards to power characteristics (ie high revving, rather low torque output), air flow and response to modifications (port configuration, port timing, port shape, etc). I have been around 2 stroke engines all my life and have built some of the fastest 2 strokers in the United States and after looking at the dyno plot, i honestly feel that the dip in power at 7250 or wherever it is, is due to turbulent air flow. It seems that for whatever reason, whatever is "opening" or "closing" is actually upsetting the flow of air through the engine. I'm not sure where this fresh air valve or duct is, but if it is upstream of the air metering sensor, then perhaps even the sensor is seeing this turbulent air condition and trying to compensate for it, adding to the deterioration of power. Either way my vote goes for turbulent air condition :)

I'd like to also add that i feel that there may be other things contributing to the low power condition, like the emissions equipment, etc.

Darril

Surely the C230C is a great value, but I wouldn't want to be seen in one. The styling is on the borderline of funky and fugly. (referring to the rear end alone) Also, C230C got a downgrade after introduction, it no uses a smaller engine and produces less power, which is really ashame. The handling on the C230C is not pretty either. If you Canadians can pay $3600 more and get a C320 sedan though, then that is a great deal.

Here's one time I'll agree with you though, I wouldn't take the C320 because it's bloody automatic only :(

let him do as he pleases. let's not get off topic about Mercedes.

sorry to hear about your love lost for the wankel canzoomer.

Actually, the C320 SPORT COUPE as sold here in Canada comes with a 6 speed stick, 17x7.5" alloy wheels, 225/45R17 tires, and so on.

See:
http://www.mbusa.com/brand/container...odelCode=C320C

Specs:
http://www.mbusa.com/brand/container...pec=0&menu=3_1

$28,370 list in USA inc freight/PDI

I would cite the Canadian URLs, but they seem to be not available right this moment..
Bottom line with the security, Bose, leather, and so on for Canada it is $42,500 MSRP