From RN - more info on dyno
 

Did anyone see this yet?

http://rotarynews.com/view.php?id=212

This should answer a lot of questions. Straight from Mazda

"In addition, we have determined that, in order to prevent damage to the catalytic converter and the entire driveline, when the PCM determines unusual operating parameters such as excessive slip in the drivetrain from the front to the rear wheels, it causes a rich high-RPM mixture and retardation of the timing. All these items combine to cause apparent considerable horsepower loss. "

thanks
good info

Wow very interesting awsome post now i have a whole other slew of questions in my head now.

Good News: Horsepower Issue Explained By Mazda
 

Check it out:

http://rotarynews.com/view.php?id=212

I guess this confirms some of our speculations.

It confirms it for me, but you know you will hear the Nay-sayers in the next few posts

If you read the bottom of the RN article its mentions that it on vehicles with DSC and traction control and that fulling turning off DSC will disable brake functions but DSC engine management is still active. So doesn't this mean that the base model RX8's that are not equipped with DSC should be able to produce on the dyno? Have any base models been dynoed yet?

Am I imagining it or did I read that holding the button in for 10~15 seconds turns both off?

Yes it does.

Glad RN got some good info on this situation.



Stupid cats. :)

No, because the engine management system is the one thats still active. You dont need DSC installed to have the engine management system in place.

I think :)

That is what I read. TCS/DSC cars CAN disable the feature but the engine management is still active and will do what they say to "self preserve" the engine and cat convertor

I wonder if there is a way to trick the ECU into thinking that the front wheels are moving in order to dyno. If it's getting input from a sensor, then maybe applying a certain voltage to that sensor wire, applying a resistor, or simply pulling certain fuses somewhere could do the trick. I know for the M3, which couldn't be dynoed at first, but then it was determined that certain fuses could be pulled before starting the car which allowed the car to be dynoed.

The explaination is potentially valid, but it doesn't explain everything.

1. All of the in-car dynos (i.e. gtech pro) show the car not having the proper torque curve and thus not having the proper horsepower at high RPMs. If the torque curve is flat, then the acceleration in g's should be linear and it is not.

2. In Japan, the 210 HP (or PS) RX-8 does 0-63 mph and the quareter mile in almost the same time as the 250 HP (or PS) RX-8. The 210 HP does 0-63 in 7.10 secs while the 250 HP does 0-63 in 7.04.

3. The results from 1 and 2 above coincide with the dyno results people are getting on normal dynos.

Wether the ports are still "stuck" or wether emissions killed the RX-8's high RPM output I don't know, but the extra two ports in the high power car aren't buying us much.

I don't why telling a forum member that his RX-8 doesn't make 247 or even 238 is the same as calling his girlfriend ugly, but some members are taking it that way.

For me personally I am buying the car today (finally came in) and I happy with the purchasing decision. In my opinion, the $500 and free service more than compensates for the drop in power.

Wether we are happy with the cars and wether Mazda is still fibbing with their 238 claim are totally seperate issues and should be debated seperately but often aren't. I don't think car is making 238 peak horsepower (but I also think that mid-RPM HP is as good as the initial claims from Mazda). I am a Mazda basher for that belief? Some (not necessarily Rotorgeek) lump me into that category and that is so far from the truth.

Zoom Zoom,

-Mr. Wigggles

MrWigggles you might be mistaken there. I for one don't count you as a Mazda basher for having an opinion. You obviously have seen some of the data, have thought about it, and you have formed an opinion. You're not slamming it down people's throats, being aggressive, rude or ignoring people.

I'm kind of with Mr. Wiggles on this one. What Mazda is saying just doesn't add up when you look at the info. Part of me believes them, the sceptic in me thinks they're trying to avoid more HP contraversy and another buyback. I wish there were some experienced tuners on this board to comment on Mazda's statement. I think if the ECU was doing things to retard the cars performance on the dyno, it would lead to some funny looking dyno graphs and the tuners running the dynos would notice something isn't right.


Ike

Ike I know you once described the higher rpm section of the dyno as "scrambled eggs". Wouldn't that qualify as something funny on the dyno? I'm no expert so its just a thought :)

But the dyno runs to date are funny looking when they hit 6500 rpm or so, and the A/F is always too rich...

Maybe when the CAN code reader project is ready, they'll be able to see if any codes are occurring at high rpm on a dyno. The other option will be to run an 8 on a 4 wheel dyno with two runs, one with the front roller free (stationary) and one with the front roller driven by the rear to get the front wheels spinning. I suppose a signal generator to fool the ECU into thinking that the front wheels are turning the same speed as the rears would also work with a dynojet!

Regards,
Gordon

I don't think that was me, I'll have to take a peek at some old dynos again but the only thing I noticed was the dropoff in power at around 6500 RPMs, which is something I felt when driving the car. Who knows, but we can argue all day about this and get nowhere, time and more info is the only thing that will really clear things up.

Ike

I will beleive that the ECU does that on the dyno... It's possible, and I'm not teh engineer who programmed it...

my question was with teh statement; "Under heavy load acceleration, the timing is retarded and the fuel mixture richened to reduce the likelihood of pre-ignition or spark knock. If spark knock is encountered, a knock sensor senses the condition and further retards the timing. Gradually timing is advanced and fuel mixture leaned after the load is reduced."

Tha was not referring to a dyno situation... So does this mean that each time the car is floored it pulls timing for a bit? Doesn't sound liek a very helpful reaction for throttle response...

Ok. Here it is - few weeks ago.

RX-8 provided for testing by Mazda themselves.
That car then went for cornerweighting on racescales - for finding the real weight of the car + fuel + 2 particular folks in it -> it was total 3344lbs on the race scales.

Then 14 pulls GTech Competition dyno runs were made. Experiments include the car as it is - so everything is supposed to work correct.
Then GTech dyno runs with front wheel rotation sensors disconnected when the ECU was off, front wheel rotation sensors disconnected when the ECU was on and the car running, etc. - to try to upset the ECU thinking the car is not moving or that only the fronts are not moving like on a dyno - so the GTech should measure less power in such situations - as was suggested by Mazda providing the car at that time (and this was not publicly announced to everyone back then).

The results - it was measured about the same horsepower - no matter if all the wheels were moving, or with sensors disconnected so the ECU doesn't register front wheels movement (both with initially the car running or shut off).

Yup the same horsepower. The runs show about 165 hp peak number.

So it didn't work with Mazda's own production car given for testing. Now what will the next Mazda's marketing folks excuse gonna be? That they suddenly "learned" that the car has some optical tracking if the ground under the car is moving? LOL What else? :)

They need something new - because this didn't work as Mazda said:
Alas, as I said the car did the same GTech graphs with and without the ECU detecting the front wheels moving. So either the ECU doesn't detect the front wheels not moving to richen the mixture or either the the ECU is broken and decides always to richen the mixture - even when the car is driven normally


I am sorry, but I can't post the dyno graphs online for public viewing. I hope they will appear in the media soon

This has been raised in the tech garage under the thread title hesitation at WOT, and probably other threads. Curious to see the hard info come out and confirm that as normal operation. At least one person said in the tech garage post that this was noticed on other cars, but not to the degree in the 8. Now I don't know what's objectively valid from that statement, but I would ponder the question of a) how normal this is, and b) how much the timing is retarded compared to other cars that do the same thing. Of course, back to the CAN readers to provide cold data :)

They say if knock is detected, the KS will further retard timing. The question I'd just throw out to the wind is, really...why all the pre-caution? I know about concerns with how a KS operates, being that it's a reactionary device and knock would have to occur before it retards the timing, but if the timing is that advanced forward to where caution has to be taken when the acceleration approaches WOT, then to me, the timing should not be that far advanced from the factory.

Would this level of caution have anything to do with accepting lower-octane fuel with open arms, or are there other cars that retard on WOT that specify premium recommended/required? I know that's not the only factor in pre-detonation, but I would think in my mind, I should generally be able to go WOT if I'm using premium gas knowing my knock sensor is there at my side to protect me without having the ECU step in the way, even if they think "the average everyday driver would not notice".

Well, I sure did miss you on your recent hiatus. Now that you are back, I think you should look those dynos over again, and review the yaw thread. Note the unusual readings as the car hits higher RPM, EXACTLY what happened to the M3 dynos and what you would expect from a computer override. It was Mr. yaw who first alerted us to the dyno issues, and unlike the other dyno posts, he is a KNOWN EXPERT.

Does anyone really think mazda is going to play with numbers at this point, with the amount of attention being paid to the HP/DYNO issues?

The real reason mazda delayed with this, I would think, is uncertainty as to the life of the cat: If they start failing in say, 70,000 miles, who would think to blame mazda? Unless a concern about it was public knowledge!! (which it now is) Our hopes for a ECM upgrade are really dashed now, I think.

Well, I sure did miss you on your recent hiatus. Now that you are back, I think you should look those dynos over again, and review the yaw thread. Note the unusual readings as the car hits higher RPM, EXACTLY what happened to the M3 dynos and what you would expect from a computer override. It was Mr. yaw who first alerted us to the dyno issues, and unlike the other dyno posts, he is a KNOWN TUNING EXPERT.

Does anyone really think mazda is going to play with numbers at this point, with the amount of attention being paid to the HP/DYNO issues?

The real reason mazda delayed with this, I would think, is uncertainty as to the life of the cat: If they start failing in say, 70,000 miles, who would think to blame mazda? Unless a concern about it was public knowledge!! (which it now is) Our hopes for a ECM upgrade are really dashed now, I think.

Now read my post about 3 posts above. The case with the M3 is when moving on the road it makes more horsepower and revs all the way to 8K rpm.
Alas when the RX8 is in motion - no matter the ECU detecting the front wheels moving or not - the measured GTech horsepower was the same. Which means either the ECU is not using the information from the front wheels to change the mixture, either it is always in some crazy mode!
The GTech numbers may be a little bit off dyno numbers (because there is air drag when the car is moving) and can't be used for exact comparison vs dyno numbers.

But for relative HP change measurements, the GTech is very accurate device. Also the GTech catches the M3 case and it really exists!
Read my post above.

Also I don't think Mazda will lower the 238hp number more, because if they do it, even 237hp is over the 5% tolerance limit from the original 250 hp and people might jump into going legally after Mazda. I am not sure how strictly this exact 5% tolerances are followed in court
But the 238 hp is the minimum number which is within 5% of the initial 250 hp announcement. This just my opinion

Is this referring to the upcoming SCC article you hinted about before?

Yes. I hope SCC will write about it in their next issue