Ok, you say it may turn out the car can not be measured at the dyno because the ECU retards smth knowing it is not moving.

What about a GTechPro Competition? :)
The car is moving in real world, and the GTechPro Comp is a quite accurate device. Or you say the RX-8 smart ECU even detects our thoughts about attaching g-meters to the car and hides the horsepower just like on a dyno.

I can't say more but check an upcoming issue of Sport Compact Car related to GTech and RX-8 :P

Has anyone seen Paul Yaw's post on his experiences with dynoing the RX-8 engine. He said that the onboard computer is really giving him a hard time. Apparently the ECU does strange things if it doesn't detect front wheels moving.

Anyways here is his post.
http://www.rx8forum.com/showthread.php?threadid=10823


There was another thread that had Japanese dyno results. 217ps at the wheels, 180 ps when its at 6200, and max torque of 20.1kg-m at 6370.
http://www.rx8forum.com/showthread.php?threadid=11170



Magic8

Saw the posts and the thing I find interesting is that the Japan dyno test doesn't seem to have a problem with the computer.
On the other side we really don't have any information on the test so maybe they did something to compensate.

Vince

Sorry, I missed that statement about the ECU or car detecting if the front wheels are moving or not.
Who made it?

There is no sensor to the front wheels that would be needed to detect this.

Look at the wiring diagrams to verify this.
I just did.

There IS a brake sensor, but it only engages when the brakes are on.

It was Paul Yaw, in the thread referenced above ( this one ). He said:I was reading your other posts about investigating the ECU - interesting work, canzoomer. I appreciate your efforts toward understanding the RX-8 systems!

Regards,
Gordon

there would HAVE to be a wheelspin sensor on every wheel, its used for ABS (to see if the wheels are locked up) and I bet it is used for the DSC/TCS systems, so it can figure out which wheel to apply brakes to... maybe you're looking at the wrong wiring diagram canzoomer ?

In here lies the whole mystery to the, emmissions related, USA ECU re-calibration issue.


This is a correct assumption. The ECU does use the ABS sensors in this role.


Based on research we gathered at Mazda and information from folks like Paul Yaw (which mentioned his research to me a few days ago), we did know that the 8 potentially defaults with up to 3 protection codes while on a dyno.

DISCLAIMER: I will not claim to know, how much exactly this protection mode effects performance #'s on a dyno, only that it does. The % is what is not known at this time.

-Bern

btw, no one has to believe me if they don't want, it's ok.

Off my chest!
 

Since thigs are out in the open now, I won't have to explain this to a thousand people at SevenStock. I guess we should have just play the 20 questions game from the start.

To reiterate: 3 know faults on the Dyno cause the car to go into Safe Mode. This is not a guess, it is a fact, and can be verified by someone with a code reader (how's that project coming along, anyhow?). You can also verify this by seeing the upper end of the dyno "spazz out" ... and look at the AF readings.

Now as to the why on the power reduction: Cat Core temp... By federal law, emmission equipment has to last for 100,000 miles. At the rotary's high exhaust temperature, the cat will destroy itself. (any previous RX-7 owner can tell you cheap cats will be destroyed by the rotary's hot-hot-hot exhaust in a matter of months... causing a neato flaming/shooting of little peices of converter material out the tail pipes... Happend on both my 1st gen (12a) and 2nd gen (13b) )

So there is hope: The engine is able to produce the orig promised HP, at the cost of cat longevity. Or, if anyone know a good chemical engineer with specialization in thermal calalistic reactions, have them see if there is anything they can recommed for a long-life, high-flow cat that can last under the extreme heat of a rotary's exhaust.



And to the Mazda folks who we promised not to reveal the causes( that read this forum), we are simply restating what someone else on the forum has mentioned.

Finally some real confirmation of what is happening with the odd dyno results. I wonder why Mazda couldn't come out and just say that the car goes into "safe mode" when it is dynoed? It would have saved a lot of us a ton of frustration.

Thanks
 

thanks for the good work, maybe now we will put to rest the Dyno guys on here that have been crying about HP...........

newb question

It's running rich, so that the excess hydrocarbon will "cool" the catalytic converter to meet the operational life requirement. Is that why it runs so rich?


Magic8

No kidding! We would have loved to give out this information when we first go it.. I'm sure Mazda has a good reason for asking us to keep quiet about it...

How about speculation for the reason they didn't want us to release the information :D

thank you paul yaw, dan and bern!!

Thanks for the update!

So does this explain why for the first few thousand miles or so, we're saying really low mpg due to the cat. issue?

Phew!

Finally something substantial. I'm deliberating on getting one and this is interesting news indeed. However, I'm a little confused here. I thought the lowered HP was due to last minute changes in emissions. Is the 'too hot for the cat' issue behind the official claimed emissions issue? So can I assume the cats' on the JDM version of the RX-8 is going to go out sooner since their power is not reduced and they don't have that federal emissions rule?

Any word on the low MPG seen by some people or is this still shrouded in secrecy because Paul Yaw haven't figured it out yet? :D

Well, here's my uneducated 2 cents...

Can anyone validate if these assumptions are feasible enough for us to put rest the hp/mpg issue(s):

1. Mazda engineers reprogrammed the ECU (to lower hp) on all the cars at port during that few weeks to comply to ensure the cat converter survives the federal emission law 100k mi requirements.

2. At the same time, to ensure longetivity of the cat converter, the ECU was programmed to allow only 'rich' burning of the fuel in the engine so that the excess hydrocarbon will 'burn-in' the cat converter slowly (therefore slowly getting use to excess heat generated by the renesis engine). This is why we are getting low mpgs in the first few thousand miles of driving the car.

3. In the future, the 2005 model will probably include a higher quality cat converter capable of withstanding all the excess heat the renesis is generating, and will provide the stated mpg right of the bat.

Do you think these assumptions are valid?

I can tell you about the gas issue from my own experience... WE ARE LEAD FOOTS! I'm had PB injected into my foot when I was 16. I love to have the engine rev... floor it to redline through 1st and 2nd on almost every traffic light. I was seeing 14.8 or so MPG.
Then I started driving like a granny... shifting before 3500, using cruise on the freeway, obeying all speed limits... 18 MPG.

On a trip from LA to Las Vegas, in 120F heat, with the AC on, cruise set around 80-85, 22MPG from Victorville to a gas station in the southern end of the valley.

We'll see how well I do next fill up, and from Vegas to SoCal for SevenStock!

cool
see ya in irvine

Re: Off my chest!
 

OK, this could explain a lot of things...but I have a couple related questions. First...why the comments that they probably would not be adding a turbo to the Renesis because it would be difficult getting the cats up to operating temps? Hell...sounds like adding a turbo would fix some of their problems :-) (Those comments may not have come from Mazda...for some reason I thought they did).

Second...several people have posted G-Tech "dyno charts" that appear to match the torque characteristics of the chassis dynos. I doubt the G-Tech tests were causing the car to enter any kind of safe mode...why wouldn't they show a nice flat torque curve in the upper revs?

jds

Late Haikus

Dyno dunno why;
Still loving my RX8;
It is so much fun.

glad to hear the news;
waiting to hear some more stuff;
yes I want the truth.

Not when the DSC is disabled.
Then the sensors are out of circuit. They are UNPOWERED in this state.
The circuit is clearly marked on the diagrams.

I know, we hooked a meter to them. No voltage, no current, no signal.

ALL the dyno runs we have seen come from people who claim they turned off the DSC.

Re: Re: Off my chest!
 

The turbo temp issue is a "cold" start related problem. On the other side of the spectrum. It would not allow the cat to fire off quick enough to meet emission requirements, and maybe, rob too much heat from the cat during normal engine operation!! It seems like we can't win. What we need is, a super-duper Rotary only cat! ;)

-Bern

Re: Off my chest!
 

Umm, so why are the catalytic converters in Japan not at risk of melting down??

I am not arguing what you said about cats. Get em too hot and they can cook.
Some makers now do dual cats, a Rhodium catalyst pre-cat, which can take high heat, right by the exhaust manifold, and a secondary ( Palladium catalyst I believe) further back where it is cooler.

Another big risk with a too-rich mixture is backfiring, where unburned fuel detonates in the exhaust right after the exhasut ports. The shock waves can shatter the catalyst bricks.

This happened to Nissan with the Altima and Sentra SE-R Spec V.
They have a massive recall on the Spec V and the Altima right now to inspect, replace cats, re-calibrate the ECU, and replace engines as needed. The shattered cats released small bits which got sucked up into the engines via the exhaust valves.
About 1 in 3 cars inspectedin the recall are getting new engines, I hear.

I used to own one, so I have been watching this with interest.
Fortunately I changed the entire exhasut system on mine at 3200km, and put in a Stillen header, and a Vibrant cat way further back down the pipe. Met Canada emissions regs, but would never have passsed in California. I used to hear the backfiring all the time on decelleration. Classic stupid use of too-rich conditions to make the cats work "better" at the detriment of the performance economy and parts life.

Oh, and cats use more fuel to make more heat, to do their jobs.
This is a problem as it makes more heat and nitrous oxide coming from the exhaust.
How big a problem?
The EPA says it is contributing to global warming in a major way.
See:
http://media.fastclick.net/w/get.med...atalyt.htm&d=f

Re: Re: Re: Off my chest!
 

Maybe. I doubt we can add much boost to the Renesis.
It is what, 10:1 compression ratio?
Add too much boost and you create a knock condition.

The earlier turbo'ed RX-7's use a much lower compression ratio.

Re: Re: Off my chest!
 

They are not per se' in risk of melting down, but I do bet they don't have to last the US federal emissions mandated 100K miles. I think Mazda was forced to play it safe with RX-8 here.

Longevity is the key thought here.

-Bern

Boosting an RX-8
 

I have been looking at boost options for the RX-8.
Turbo or compressor, it seems that there is not a lot of room for boost.
The RX-8 Renesis uses a 10:1 compression ratio.

This is quite a bit higher than earlier RX-7's with Turbos start with.
On the turbo models they typically started with a compression ratio that is down from the naturally aspirated models by about .7 to .9.

See:
http://www.atkinsrotary.com/enginepart.htm

Rotor Weight & Compression Ratio
Year Engine Compression Ratio
79-82 12A 9.4
83-85 12A 9.4
84-85 13B 9.4
86-88 13B 9.4
87-88 13B Turbo 8.5
89-91 13B 9.7
89-91 13B Turbo 9.0
93-95 13B Turbo 9.0

Re: Re: Re: Off my chest!
 

Good point. With the mandatory inspections in Japan, not many people even keep their cars that long!

Off my chest!
 

Well the FD used a 9.0:1 ratio lower agreed, but not extremely. I will agree with you on your points though.. boost would be very limited. I'm very excited to see what the Greddy low-boost kit comes out like.

I happen to run a 13B 9.4:1 turbo motor in my 1st gen. I can safely boost 11lbs or so on pump gas. I love my ride with race gas and more boost. :). I run a Electromotive TEC-2 ECU.


BTW, on my prior comments, I wasn't addressing the merits of turbo'ing a RENESIS, just addressing the "heat and emissions issue" associated with a turbo on RENESIS and it's exisiting cat set-up.

-Bern

Re: Off my chest!
 

Please, now explain why does the car show the same low results when dynoed with GTech Competition? The car is at speed so the problems with safe mode because of standing on dyno machine should be missing.

Why does the RX8 show lower hp and tq results compared to other cars of similar horsepower?

RotaryNews/Bern/Mazda:

The HP data from multiple sources seem to coincide with the dyno runs that some of us have done.

What HP are we really putting to the wheels ITRW according to your sources?

Vince

Re: Re: Off my chest!
 

I respect everyone doing G-Tech runs on this forum, but it goes both ways .. what do you say about these GTech runs posted by SPEED RACER today?

http://www.rx8forum.com/attachment.php?s=&postid=123174

Please read his post at:

SPEED RACER POST


I can't comment, cause I don't have an answer, but why does it show greater performance... again, can't comment cause I don't have the answer.

-Bern

Since we have a number of experts on this forum, I would like to get an explanation on the Peter Yaw article.

It makes sense to me that you can 'increase' the torque by gearing (half torque with 2x gear is the same). SO, how come the measured torque on the RX8 is so low. If it is being multiplied should it not be higher.

This is a serious question, I do not know the answer, so please don't give me a flame answer.

Thanks

You can not "increase torque"

You CAN increase mechanical advantage.

Look at it this way:

With a rope and a 1000 lb weight you can not lift the weight off the ground.
Add 2 pulleys ( called a block and tackle), and when you get a 3:1 mechanical advantage and you CAN lift it. Much more slowly.

If you pull the rope faster you lift it ifaster.

So, strong man who can lift the weight on rope by pulling rope at 1 foot per sec. Lots of "torque"

Wekaer man who pulls rope, thriough two pulleys, with a 2:1 mechanical advantage.
Lifts weight at half speed if pulling same amount of rope.

Double the rate you pull rope, and you keep up with the "strong man"

In both cases the same amount of WORK is done.
Both are making the same HORSEPOWER.


On big V8 we use less pullies, as it is "stronger" ( has more torque) and needs less revs to do the job.

The total job is "horsepower".
Basically revs ( of feet of rope) x torque (strength).

Below is a quote from Mr. Yaw's article. As you can see, he clearly states that the torque will be higher at the output shaft in first gear than in fourth gear.

So my question is still the same. What is the torque advantage with the RX8 gearing. Does it equal other higher torque cars, come close etc.

And why would the dyno NOT measure this increase. This is what I am trying to get my mind around.

But thanks for the reply Canzoomer.



"If the transmission is in 4th gear, one complete revolution of the input shaft will result in one complete revolution of the output shaft, just as if there were a solid shaft running all the way through. If we attach a 1-ft. lever to the input shaft with a 10-lb. weight on the end, the torque at the input shaft will equal 10 ft.-lbs. as we have already determined. Since we have a 1 to 1 ratio from input to output, we will also have 10 ft.-lbs. at the output shaft.

If we were to keep the same weight and lever on the input shaft, but switch the transmission to third gear, we would still have 10 ft.-lbs. at the input shaft, but we would now have 13.91 ft.-lbs. at the output shaft. This value is the product of the input torque and the gear ratio. (10-ft.-lbs. times 1.391 gear ratio equals 13.91 ft.-lbs.) If we were to switch the transmission into 1st gear, the result would be 34.83 ft.-lbs. at the output shaft.

As you can see, a gearbox gives us a simple way to vary the torque through leverage, and it is equivalent to changing the length of the lever. Thanks to gears, we can have any amount of torque that we want! In fact, a bone stock 12A making only 100 ft.-lbs. of torque could be geared to pull an 18-wheeler up a steep hill, as long as we are not in any big hurry to get the job done."

The dyno measures torque TIMES rpm.
This is power.

Torque, times motion, equals work performed.

You can reduce gear the output to make more torque.

The input speed in rpm is the same, but the output speed is REDUCED.

Again, speed times torque equals work performed.

There is no such thing as a free lunch.
You can pull more , but more slowly, through gear reduction, or pull less, but faster with less reduction, and even less more quickly, by gear multiplication.
In the case of your car, in 1st gear it reduces the ratio, and in 6th it actually increses it, so is basically an overdrive gear.