Synopsis of Dyno/Horsepower Issue

Summary:

Rear wheel dyno runs by owners of 'showroom' purchased cars show a lower than expected power output of the North American spec RENESIS 'high power' engine.

Dyno Run #1:
http://www.rx8forum.com/showthread.php?s=&threadid=6890
By 'adamp316' Boca Raton, FL
HP: 173.8 @ NL Tq: NL

Dyno Run #2:
http://www.rx8forum.com/showthread.php?s=&threadid=7533
By '1stRX8' Houston, TX
HP: 184 @ 8500 Tq: 130.7 @ (estimated) 6200

Dyno Run #3:
http://www.rx8forum.com/showthread.php?s=&threadid=7863
By 'compaddict' Auburn, CA
HP: 178.02 @ 8500 Tq: 123.23 @ (estimated) 6000

Torque RPM is estimated because the curve is very flat and it's difficult to see the peak.

Average rear wheel horsepower (rwhp): 178.61

Parasitic loss from published 247 bhp SAE
Run #1: 29.64%
Run #2: 25.50%
Run #3: 27.93%

Average of 3 runs: 27.69%

Assumptions and Averages:

The most COMMON parasitic loss for a manual transmission, rear-wheel drive car is between 15% - 20%.

Assuming an average (rounded up) of 18% and a rwhp rating of 179, then we ASSUME the RENESIS is making 211bhp SAE 'at the crank.'

Adding in the 5% loss that is common of new piston engines we arrive at: 222bhp SAE

Looking at torque only: Average of 127lb-ft which would equate to 157lb-ft 'at the crank.' 159lb-ft is the listed rating.

This torques suggests the issue is at the top of the RPM band, above 6000 RPM.

Possible Root Causes Stated:

· Improper dyno operation
· The DSC was left on or improperly disengaged
· 'Tight' engines that require a 'break-in' period
· A 'break-in' engine control software cutting engine power deliberately until a certain mileage is reached
· A deliberate change of engine control software for emission purposes
· A mechanical defect or design flaw
· The engine never made nor was designed to make 247bhp SAE
· There is no problem as the amount of parasitic loss is not excessive


Relevant Statements:

· Listed on dyno run #3 is a '93 RX-7 showing 207.57 rwhp. The '93 RX-7 is listed at 255bhp giving a parasitic loss of 18.6%

· It has been stated that the Miata has had around 23% parasitic loss.

· Wheels dynos are difficult to operate and mistakes are common

· Stated on Rotarynews.com: http://rotarynews.com/view.php?id=193
Q:How much horsepower does it make to the rear wheels?
A: About 204-207

· A Japanese 210PS 5MT and 250PS 6MT show similar performance
http://www.artex.co.jp/Pages/Car/RX-8/magazine/Image/BestCar_03_6-26_03.jpg

· There was a Japanese tuning company that dyno'd a hi-power with their exhaust on , 212bhp at the wheels.
http://www.rx8forum.com/showthread.php?threadid=6259

· Air/Fuel graph shows a 'rich' running engine at the upper RPM range

· Torque reading on the dyno is not excessively low

Relevant Threads and Links:
http://www.rx8forum.com/showthread.php?s=&threadid=6890
http://www.rx8forum.com/showthread.php?s=&threadid=7533
http://www.rx8forum.com/showthread.php?s=&threadid=7863
http://rotarynews.com/view.php?id=193
http://www.rx8forum.com/showthread.php?s=&threadid=7976
http://www.rx8forum.com/showthread....90711#post90711
http://www.rx8forum.com/showthread.php?threadid=6259
http://www.rx8forum.com/showthread.php?s=&threadid=8579



Mazda issued Power/Torque curve as measured at the flywheel

http://mysite.verizon.net/romano.michael/3.jpg

Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you!

RomanoM's POST could concisely show Mazda or whom ever what we are concerned about, what we want an explaination for. I was getting Soooo frustrated and confused reading all the speculation on all the many threads. I hope any who post here follow your lead.

Thank you RomanoM!!

Very good summary. I will be contacting Mazda. I have been waiting on my car to arrive, but am hesitant after reading the multple threads about this. I hope we get a definite answer from Mazda, wether it is break in or the ECU that changes over. Also If it is the ECU I hope it doesn't wait until 20,000 to kick over. That would not be good.

Originally posted by Spin9k
Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you!

RomanoM's POST could concisely show Mazda or whom ever what we are concerned about, what we want an explaination for. I was getting Soooo frustrated and confused reading all the speculation on all the many threads. I hope any who post here follow your lead.

Thank you RomanoM!!

No problem.

I too was getting confused with all the threads and posts.

Admin/Moderators how about putting this as a sticky on the appropriate Topic.

Thanks

Do all US cars have the DSC/TSC? I have a GS in Canada with no such thing. It's only on the GT in Canada..... hmmm, maybe I'll get a better run?

Originally posted by Wing
Do all US cars have the DSC/TSC? I have a GS in Canada with no such thing. It's only on the GT in Canada..... hmmm, maybe I'll get a better run?

All but the base car gets DSC (which includes TC).

Originally posted by Spin9k
T
RomanoM's POST could concisely show Mazda or whom ever what we are concerned about, what we want an explaination for.Do you really think they don't know?

Mazda's investigating, but I suspect it will be a frustratingly long time before they say anything one way or another (probably more like months than weeks or days...)

You know IF the high-power is making around 220bhp SAE that's equal to 223bhp DIN(PS) or close to the Euro engine.

Just thinking out loud, that's all.



BTW: 228bhp DIN is 225bhp SAE

a few questions:

1) has ANYONE with a J-Spec Hi-Power Renesis dynoed their car yet? there has to be quite a few out there that have that also have over 2000 miles by now...

2) does anyone know what REALLY happened at the port when they were held?

3) there are still some advertisements i see with the Hi-Power Renesis putting out 250hp NOT 247hp...since it was a fuel emission thing, could it be that they lowered the hp a little too much?

There was a Japanese tuning company that dyno'd a hi-power with their exhaust on , 212bhp at the wheels.

Scans were posted here with the data+pic of the car on the rolling road etc. dunno under what title.

Originally posted by RobDickinson
There was a Japanese tuning company that dyno'd a hi-power with their exhaust on , 212bhp at the wheels.

Scans were posted here with the data+pic of the car on the rolling road etc. dunno under what title.

http://www.rx8forum.com/showthread.php?threadid=6259
I think this is what you're talking about?

Yep

Looking at torque only: Average of 127lb-ft which would equate to 157lb-ft 'at the crank' assuming the 18% plus 5% for 'tightness' in the engine. 159lb-ft is the listed rating.

This torques suggests the issue is at the top of the RPM band, above 6000 RPM.

Originally posted by RomanoM
This torques suggests the issue is at the top of the RPM band, above 6000 RPM.

...which is precisely where the ECU decides to run AF ratios of 11:1, and who knows what kind of ignition timing.

BOOSTD7 brought evidence that it's not mechanically related as the Star Mazda car (for next season) is having no trouble getting the power down, further entrenching my belief that this is an extremely fixable "problem", if it wasn't intended in the first place.

Originally posted by wakeech


...which is precisely where the ECU decides to run AF ratios of 11:1, and who knows what kind of ignition timing.

BOOSTD7 brought evidence that it's not mechanically related as the Star Mazda car (for next season) is having no trouble getting the power down, further entrenching my belief that this is an extremely fixable "problem", if it wasn't intended in the first place.

I have come to the same conclusion after finally putting all the info in a form easy for me to digest.

Very good summary. I also think that this is probably an ECU map issue. Wether it's an incorrect fuel map or a "break in" map, I guess we'll see when/if Mazda decides to provide some feedback.

Originally posted by RomanoM


I have come to the same conclusion after finally putting all the info in a form easy for me to digest.

hahaha... yes yes, and kudos to you Romano.

I really think it would be of great use to see some automatic rx8 dyno results, because although i drive the 6 speed, it the automatic indeed makes similar rwhp as the hipower then we will have a new piece of evidence.

Well we all know that the Renesis is certainly capable of generating the claimed 247bhp because the early reviews of the pre production cars stated performance figures that could only have been attained with that output. The question perhaps is can the Renesis be made to produce that power and still be LEGAL?

Now that is a very good question.

Originally posted by Lensman
The question perhaps is can the Renesis be made to produce that power and still be LEGAL? And if a reflash was available that unleashed the full potential but wasn't CARB/EPA/whatever legal, would we care? ;)

Yes because at least in Canada we have emission testing after 3 years I think. Also, I wouldn't want to pollute the environment anymore than I have to.

There's always going to be 'gremlins' when a new car is first released. I think as long as Mazda keeps people informed and updated, then I don't think the image of the car will be hurt any. Yes, I'll be holding back until I see what happens, but for those of you who have already purchased yours, I wouldn't worry too much about it, as Mazda will set it right in time, I'm sure.

i think there should be a CSI episode about this :D

Originally posted by Lensman
Well we all know that the Renesis is certainly capable of generating the claimed 247bhp because the early reviews of the pre production cars stated performance figures that could only have been attained with that output. The question perhaps is can the Renesis be made to produce that power and still be LEGAL? The Euro version was originally advertised as 240 ps, but then down graded to 228 hp due to emissions. Mazda knows the US is its largest market, they would have to get the emissions right here as well. With all the years spent engineering this thing, I find an 11th hour port ECU mapping change due to US emissions highly unlikely.

But I also agree that this is all probably due to the ECU map, my feeling is that it is by design. Either the cars are still too green (even with 2K miles) and/or the dyno environment has something to do with it. I'm at peace with the situation, but like all, would like the definitive answer.

I don't quite understand.... if the NA Renesis is not capable of making the claimed 250hp and follow emission regulations, then exactly what is the point of moving to NA Renesis rather than turbo? Either way, I think all the 6MT RX-8 owners deserve an explanation and apology from Mazda USA for this embarassing screw up. Write to automobile medias and magazines about this, complain to your dealership and spread the words. Make it perfectly clear that Mazda's reputation is going to drop like bird poo unless they fix this issue RIGHT NOW!

Originally posted by Skyline Maniac
I don't quite understand.... if the NA Renesis is not capable of making the claimed 250hp and follow emission regulations, then exactly what is the point of moving to NA Renesis rather than turbo? Either way, I think all the 6MT RX-8 owners deserve an explanation and apology from Mazda USA for this embarassing screw up. Write to automobile medias and magazines about this, complain to your dealership and spread the words. Make it perfectly clear that Mazda's reputation is going to drop like bird poo unless they fix this issue RIGHT NOW!

Well for the moment let's assume it can and that this is either a non issue or easily fixable. Nevertheless Mazda need to get it together and speak to the masses. If there's no problem then it's an easy P.R, job, if there IS a problem then the P.R. needs to be swift and surgical. Mazda's rep can suffer just as much from a continuing rumour as from a genuine issue.

Having said that: the engine clearly can't meet UK emissions laws in it's 247bhp form. Much to my annoyance.

Originally posted by RX-Hachi
With all the years spent engineering this thing, I find an 11th hour port ECU mapping change due to US emissions highly unlikely.
Yet that is the case. Cars usually stay in port 1-2 weeks. The RX8 was in port for a month and the official reason given to dealers was updating the ECUs to meet emission requirements.

was that indeed for mazda or just for porshe? i remember there was speculation about it for the 8's, but dont recall anything definative.

the reason i say porshe is because someone posted a scan of something that said the new porshes couldnt meet emissions and had to be held for remapping.

Originally posted by PUR NRG

Yet that is the case. Cars usually stay in port 1-2 weeks. The RX8 was in port for a month and the official reason given to dealers was updating the ECUs to meet emission requirements. What I meant was I doubt there was a last minute engineering change to the ECU map. The ECUs may have very well been updated to US emission standards at the port, but I have to believe the engineering design of the ECU was already completed months before the cars ever left Japan. But if I'm wrong, and there was a last minute change that detuned the engine too far, it should be an easy fix for Mazda.

All this "dyno" stuff is way over my head. I undertans that the dyno is suppose to adjust for conditions present at the time of test. BUT, what about air flow at the intake? I've crawled all over the one at my dealer (mine is still 2-3wks away) and it seems to me that there would be some sort of "ram" air induction when the car is underway. When they dyno, do they put a big fan in front of the car? Or is this something the dyno is supposed to adjust for? But how? If there is no air being crammed into the intake... But I'm repeating myself. If it's wrong, Mazda will fix it I'm sure. I ain't cancelling my order!:cool:

I am interested to see that the calculated power appears to be more inline with the UK(Europe) Spec car, which they have revised to 228-230 or whatever it is. Have you guys got the same engine as us perhaps????

Also, are the problems with Dyno's down to the fact that they are designed for "normal" piston engines? Does the fact that the car has a lighter than normal carbon prop shaft have anything to do with the results??? (I am not an expert, as this statement may or may not prove!)

Ed

Originally posted by TybeeRX-8
All this "dyno" stuff is way over my head. I undertans that the dyno is suppose to adjust for conditions present at the time of test. BUT, what about air flow at the intake? I've crawled all over the one at my dealer (mine is still 2-3wks away) and it seems to me that there would be some sort of "ram" air induction when the car is underway. When they dyno, do they put a big fan in front of the car? Or is this something the dyno is supposed to adjust for? But how? If there is no air being crammed into the intake... But I'm repeating myself. If it's wrong, Mazda will fix it I'm sure. I ain't cancelling my order!:cool:
Yes a big fan is usually placed right beneath the intake to simulate driving conditions.

Originally posted by PUR NRG

Yet that is the case. Cars usually stay in port 1-2 weeks. The RX8 was in port for a month and the official reason given to dealers was updating the ECUs to meet emission requirements. Thumtimes i feel tho thtupid! :confused:

How can you improve emissions by making an engine run richer? Is it NOX?

Also, if it helps to ease anyone's mind, there was significant dyno testing done on the 03 cobra's by their owners when they first came out. Many people took them straight from the dealership to the rollers. 340-350rwhp was the average. After a few thousand miles of break-in, many people began to report feeling an improvement in power. Returning to the dyno, the same cars were putting out closer to 360-370rwhp with no modifications at all.

Now obviously there's going to be differences with air temperature and dyno variances, no matter how closely they are controlled, but there was enough people going to the dyno to uncover a conservative 15rwhp gain average.

I know NOTHING about rotary engines, so I can't say that the same thing is happening here with the RX-8, but I wouldn't be suprised to hear you guys finding 200rwhp numbers once your cars are broken in.

I feel compelled to point out that a break in period rarely exceeds 5k miles, and often occurs after just 1k. Not after the 20k that I've read theorized somewhere on this board.

Originally posted by Racer X-8
Thumtimes i feel tho thtupid! :confused:

How can you improve emissions by making an engine run richer? Is it NOX?

You don't

Richer will cause higher emissions

Originally posted by Skyline Maniac
I don't quite understand.... if the NA Renesis is not capable of making the claimed 250hp and follow emission regulations, then exactly what is the point of moving to NA Renesis rather than turbo? Either way, I think all the 6MT RX-8 owners deserve an explanation and apology from Mazda USA for this embarassing screw up. Write to automobile medias and magazines about this, complain to your dealership and spread the words. Make it perfectly clear that Mazda's reputation is going to drop like bird poo unless they fix this issue RIGHT NOW!

What a great idea! Let's all jump to the conclusion the dyno results are perfectly fine and that ALL of our ASSUMPTIONS are correct. Forget about waiting a REASONABLE time period for the actual makers of the car to respond - let's start pumping this speculation to the mass media ASAP! That way, even if we're wrong, it won't matter because we've already done the maximum damage!

Perfect! Really winning!

Is everyone taking into account the cat and how it affects Wideband O2 readings?

Originally posted by PUR NRG

Yet that is the case. Cars usually stay in port 1-2 weeks. The RX8 was in port for a month and the official reason given to dealers was updating the ECUs to meet emission requirements.

Has anyone noticed the little sticker on the underside of the hood to the right of the latch?? It's a sticker with hand written stuff on it that says on mine:

PORT CAMPAIGN
Rework# 03F02, 03F04
7/8/2003

Could this be anything about what was done re: emissions or something to the engine, or was it my port installed options? (splashgards frt/rear and rotary appearance pkg?)

Sounds a little interesting. Does anyone else have this, any idea what is is?

someone noted exhaust pipes dripping something (black and gooey id assume, possibly fuel or something), RodsterinFL i think it was

Originally posted by Shamus


What a great idea! Let's all jump to the conclusion the dyno results are perfectly fine and that ALL of our ASSUMPTIONS are correct. Forget about waiting a REASONABLE time period for the actual makers of the car to respond - let's start pumping this speculation to the mass media ASAP! That way, even if we're wrong, it won't matter because we've already done the maximum damage!

Perfect! Really winning! Aw now, there you went & done it. You've acknowledged his presence. Darn.

SM - as his moniker would imply, has been a genuine pain in this forum for many moons. Now you know. ;)

COMPADDICT - I dunno about the others, but you got me hangin' here. Care to expound just a little more???:)

Originally posted by wakeech


...which is precisely where the ECU decides to run AF ratios of 11:1, and who knows what kind of ignition timing.

...

I think the a/f is more like 12.2

-Mr. Wigggles

Originally posted by eccles
And if a reflash was available that unleashed the full potential but wasn't CARB/EPA/whatever legal, would we care? ;) I don't know about your state, but Colorado (OK, the Front Range of Colorado) has mandatory emissions inspections after the first four years of ownership of a new car or upon transfer of ownership, then every other year thereafter...

Originally posted by MrWigggles


I think the a/f is more like 12.2

-Mr. Wigggles

looked even lower on that first Dynojet that was published... just from visual memory of the curve, it really really went south about half way through the band.

Originally posted by BillK
I don't know about your state, but Colorado (OK, the Front Range of Colorado) has mandatory emissions inspections after the first four years of ownership of a new car or upon transfer of ownership, then every other year thereafter... The beauty of flash memory: a program for every occasion. ;)

Originally posted by Lethalchem
340-350rwhp was the average. After a few thousand miles of break-in, many people began to report feeling an improvement in power. Returning to the dyno, the same cars were putting out closer to 360-370rwhp with no modifications at all.

Keep in mind, that's a 20hp increase over 340-350hp or about a 6% increase. 20hp over 180 is an 11% increase, or almost twice as large. I don't think the Renesis would "find" 20hp after "break in".

lol
how very true

edit:
woah, i was refering to the thing about flash memory
although i suppose "finding" 20hp is perhaps a little far fetched also, though i dont believe that it is even gone

Originally posted by eccles
The beauty of flash memory: a program for every occasion. ;)
You're still polluting the environment terrible.. and for what? An extra 10hp? 20hp? :confused:

Besides, do we know that the ECU is flash programmable?

Thanks Romano m for your summary of the power dyno saga , i have downloaded the info and sent it to mazda australias managing director hopefully they may be able to shed extra light on this issue .

Yes, all of the literature that I've seen says that the ECU IS Flash-programmable!

I can just imagine:

Yup, that's a damn fine looking engine. Look how shiny and small it is...

Originally posted by Racer X-8
Aw now, there you went & done it. You've acknowledged his presence. Darn.

SM - as his moniker would imply, has been a genuine pain in this forum for many moons. Now you know.

COMPADDICT - I dunno about the others, but you got me hangin' here. Care to expound just a little more???

Hold on a second, please. I didn't know about Skyline Maniac's reputation before you mentioned it, but I think his comment has a point.

Given:
- Mazda knows of the issue, and has since the first dyno, around July 18th.
http://www.rx8forum.com/showthread.php?s=&threadid=7976&perpage=15&pagenumber=3
http://www.rx8forum.com/showthread.php?s=&threadid=6890

- The power at the wheels should be about 204hp to 207hp.
http://rotarynews.com/view.php?id=193

- There have been three dynos, in three different areas, showing the car to be 20hp to 30hp underpowered.
http://www.rx8forum.com/showthread.php?s=&threadid=6890
http://www.rx8forum.com/showthread.php?s=&threadid=7533
http://www.rx8forum.com/showthread.php?s=&threadid=7863

Speculation:
Let's review the responses Mazda is likely to make for the three scenarios regarding the low hp dynos:

1) Design Flaw
If the car is indeed supposed to be producing 247hp at the flywheel, and it is instead producing 20 or 30 less, Mazda will hold out on breaking the news until (a) they have a fix, or (b) the media threatens their sales. It's possible they'd even preform the fix at a scheduled service and not tell the car owner, and wait for the media to pick up on it. I also wouldn't put it past them to stifle internet communities' reaction via anonymous interjection.

2) Design Feature
It's possible the car underperforms on dynos which are not specially designed to test it (like the bmws with front wheel sensors). Another possibility is the ECU that is designed to remove a cap or change air/fuel ratios at a certain mileage or at a scheduled maintenance, to aid engine break-in. In this scenario, Mazda will tell people ASAP, at the least to avoid misconceptions in the media, or even better, to keep their enthusiasts happy (they hope to cater to the enthusiasts for the new RX-7 if their flagship RX-8 does well).

3) Dyno Flaw
This is the easiest for Mazda, because they have a dyno at their disposal, which they know is in perfect working condition, and you can bet they've already dynoed several cars since hearing of the issue. They can easily issue a statement that the consumer's dyno results are wrong, and their cars can be sent to the dealer for inspection. Similarly to scenario #2, they'd want to act with all haste to keep the media from publishing misconceptions.

Conclusion:
Since Mazda has had three weeks to consider their position, and their flagship vehicle is of utmost importance to them, it seems they have not responded as though they believe it's scenario 2 or 3. I think a month is more than enough time to straighten out misconceptions; their PR dept. should have taken care of that in a week's time, or at least before the next month's magazines come out.

Therefore, I believe there is a problem of some sort, and we can either sit and wait for word which will be very slow in coming (perhaps never, if there is not a fix, and no one outside the company investigates), or we can compile our findings, as well as email addresses of owners and others concerned who are considering buying the car (names in the media are very good to have on the list, as well). Then on the 18th or thereabouts (one month since Mazda has known), contact Mazda as a single entity with the document, and leverage contacting the media if detailed (feature/flaw in the car) answers don't come out within a week.

They know that more cars will be dynoed soon, and their answers had better match those results. Lying would prove to be a bad move.

That leaves enough time for them to respond, and enough time for the information to be published in the next month's magazines if they don't respond.

I'm not one for causing trouble, but I think tucking one's tail between one's legs is not the right thing to do. The corporation's interests are not always the same as the consumers'. Further more, there are a great number of people waiting for the information before purchasing an RX-8, and some who have decided to look elsewhere; Mazda should be told that they would benefit. It would also be kind to those who are already committed to their purchase by allaying their fears.

Very well put Altaic.

I agree with your conclusion as well, except that Mazda may not have known about any issue at the first dyno (single instance shows no trend), but they should by the third dyno from Compaddict on 7-30-03 which even includes the graph and all environmental conditions. Certainly I and others I am aware of only contacted Mazda at that point so they have only had a week so far to investigate and prepare.

I suggest we let Mazda's slow-moving PR people have until 8-31-03 to tell us what is going on, and then go to Mazda en masse for clarification. By mid-August I will start to think the 'good news' options (2 and 3 in your post) are unlikely.

I am watching this thread with much interest. I personally own a turbocharged MX-5, and am familiar with ECU mapping and air fuel ratios for my car. That said, I know little about what A/F a normally aspirated rotary engine needs for best power.

The posted dyno chart that logged AF read all the way down to 12:1 AF after 7000 RPM. That is a fairly rich mixture that is appropriate for about 12psi boost on a piston engine, such as my car. This seems extremely rich for any normally aspirated engine. Can anyone else confirm this would be true also for the Renesis?

Also, in a boosted app at least, the A/F ratio should be stable from peak boost to redline. The RX-8 logged A/F drops all the way to redline where it is in the neighborhood of 12:1. I would have expected to see something much more constant after WOT onset.

Also, a VTEC hit, such as on the S2000, will give a JUMP in torque, right as the profiles switch, due to the increased VE and CFM airflow at that point. The 3-stage intake of the RX-8 should provide two similar hits noted on the dyno chart where these additional ports open (the first being open during regular driving, the other two open at later RPM setpoints).

This being true, why do the dyno graphs show torque DROPPING at each RPM setpoint? Seems to me that the engine is not getting the additional air that we would expect from the opening of another intake port, or that the ECU delivers too much fuel when these RPM points are reached.

The engine in my car (1999 Miata engine) has a VICS variable intake system that switches from long intake runners to shorter intake runners at 5300 RPM. At this point on the dyno graph, torque visibly rises and holds to redline. Basically, with a markedly superior setup on the Renesis that actually DELIVERS more air by definition twice in the rev range, I would expect to see at least similar results if not better than with the VICS switchover on the 1999 and 2000 MX-5.

Something seems fishy to me...

Kurt

Also from the dyno charts, I see where the second intake port opens at ~4000 RPM, and I see where the third intake port opens at ~6200 RPM.

What happens at 7200 RPM that delivers the same dip in the torque curve?

Kurt

many people ahve speculated that the ECU deliberately drops the AF ration to protect the engine during break-in periods
which explains the drop in torque and stuff youve pointed out as being awfully wrong for peak power

Originally posted by turboMX5
Also from the dyno charts, I see where the second intake port opens at ~4000 RPM, and I see where the third intake port opens at ~6200 RPM.

What happens at 7200 RPM that delivers the same dip in the torque curve?Actually, one of those lower hiccups (I forget which) is caused by an external valve which alters the characteristics of the intake tract. The final 7200rpm hiccup is the third ports opening.

they aren't talking about hiccups here. if i'm reading correctly, what they are mentioning is the overall degrease in torque after the ports and intake's open and change, respectively. notice that after the 2nd and 3rd sets of ports open up, the torque drops significantly and fails to ever reach the maximum torque produced from the previous set of intake ports.

i have edited the toque curve to show what i think is the general trend, and how it seems to be going from the previous port opening data.

as you can see, it seems opening the 5th and 6th ports is parasitic, causing the car to loose torque and peak hp. it seems the torque between 6300 and 7400 was greating increasing and by leaving that setup alone, the car would end up producing more toque and more HP further on down the curve.

i agree with turbomx-5. you'd think with a change in ports and intake setup, you would get a net rise in torque, not a decrease.

For those who are new to Mazda, there was a similar hp issue with the miata as well a few years ago. But the power loss wasn't this dramatic. only about 7hp. I'm not sure Mazda ever compensated the owners.
I know for a fact that Ford actually recalled the Cobras and have them retuned with modified headers and some engine work to regain the claimed hp figures. I really really hope Mazda would rectify this issue....if indeed is an issue.

Originally posted by delhi
For those who are new to Mazda, there was a similar hp issue with the miata as well a few years ago. But the power loss wasn't this dramatic. only about 7hp. I'm not sure Mazda ever compensated the owners.
I know for a fact that Ford actually recalled the Cobras and have them retuned with modified headers and some engine work to regain the claimed hp figures. I really really hope Mazda would rectify this issue....if indeed is an issue.

I'm sure somebody will come in who knows exactly, but Mazda either bought those cars back, or gave free extended service etc on them... for 7.... I doubt they screwed up 20, but maybe that's just me...

Originally posted by KyngNothing
I'm sure somebody will come in who knows exactly, but Mazda either bought those cars back, or gave free extended service etc on themI won't go into detail here because this is covered in other posts, but basically Mazda gave Miata owners two choices: Free maintenance for the length of the warranty period or they would buy back the cars.

Now, to comment once again on many folks' "Mazda must tell us something by this date" demands, fact is Mazda's a big company and if you know anything about big companies it's that announcements about things like this come slow. Even if it was something like the RX-8 cannot be dynoed on a "standard" dyno they would want to cover all their bases and determine exactly why before saying a thing.

As I've stated before, I would be rather surprised if Mazda makes an announcement within a month, because frankly it's the concern of a bunch of enthusiasts at this point, and most potential customers don't even know the 8 is out yet let alone know about any theoretical power issue.

Remember that BMW only really addressed the E46 M3 engine issue when AutoWeek reported on the web site reports, and even then a majority of potential M3 purchasers know nothing except their engine warranty has been extended for some reason; if there is an issue and Mazda plays their cards right potential 8 owners would be similarly oblivious and just think "Gee, the 8 comes with free maintenance - cool!"

Originally posted by Quick_lude

Keep in mind, that's a 20hp increase over 340-350hp or about a 6% increase. 20hp over 180 is an 11% increase, or almost twice as large. I don't think the Renesis would "find" 20hp after "break in".

Good point! I didn't think of it that way, I was just trying to present an encouraging possibility.:D

Originally posted by rx7aggie
notice that after the 2nd and 3rd sets of ports open up, the torque drops significantly and fails to ever reach the maximum torque produced from the previous set of intake ports.Which was exactly my point in an earlier post (in one of these damned dyno threads). I strongly suspect that because these dyno runs are being done in 3rd gear, the engine is spinning up too fast for the system to recover from the extra turbulence or whatever that is caused by the opening of the extra ports. I suspect that if the runs were done in a higher gear, so the engine reves up more slowly and has a chance to recover after each change, that we would see a rapid recovery back to almost the same HP as before each port opened, and climbing again from there. But nobody else seemed to want to pick up on that point at the time, for some reason.

I thought the dyno with the 2000mile engine was also done in 4th and 5th gears but since the results were almost identical Compactaddict didn't post them up. Maybe you could ask him if he has the plots of those runs for comparison.

Yes Compaddict said that the 4th and 5th gear runs were about 1% less - within the bounds of measuring error.

Based on my experience with switching the variable intake on my Miata, I would like for someone to try something on their RX-8 and see if the power feels any better.

I bet the engine has two butterfly actuators, one for each of the additional ports. These will be controlled/switched by a solenoid near or on the plenum. If it is like my car, the extra chamber is held closed by a +12V current to the solenoid, channeling vacuum to the actuator that holds the chamber blocked off. At the ECU's RPM setpoint, this circuit is broken, removing the vacuum signal, that opens the butterflies for the extra chamber or plenum.

Judging from all the dyno charts I have seen of the 6-spd, the power could benefit from NOT switching to the auxillary intake ports, for whatever reason. The quick and easy test for this is to wire the intake actuator in its idling/rest position.

Alternatively, the same test could be done by wiring the actuators in the open (high RPM) setting and seeing that difference. I'm sure you could learn alot from this, especially if someone was to test this on the dyno.

If anyone on this list is in the DFW area, I'd be happy to explain further and show an example on my turbocharged MX-5.

Kurt

One of the threads about this in the tech forum stated that there are not vaccum tubes and the the actuators are electronic/computer controlled. So this may not work, however I may be wrong.

There seems to be a bit of confusion as to how the intake paths and ports work. I hope this helps:

Neit,

Great post. I was wondering exactly how the ports worked.

Originally posted by omahawk
Neit,

Great post. I was wondering exactly how the ports worked.

Or in this case, how they don't work. They look to be a detriment to power. Maybe they only half-open or something? The torque should NOT drop with an advertised positive effect from resonance or from additional port airflow.

I bet a solution will be found rather quickly.

Kurt

Originally posted by rx7aggie
they aren't talking about hiccups here. if i'm reading correctly, what they are mentioning is the overall degrease in torque after the ports and intake's open and change, respectively. notice that after the 2nd and 3rd sets of ports open up, the torque drops significantly and fails to ever reach the maximum torque produced from the previous set of intake ports.

i have edited the toque curve to show what i think is the general trend, and how it seems to be going from the previous port opening data.

as you can see, it seems opening the 5th and 6th ports is parasitic, causing the car to loose torque and peak hp. it seems the torque between 6300 and 7400 was greating increasing and by leaving that setup alone, the car would end up producing more toque and more HP further on down the curve.

i agree with turbomx-5. you'd think with a change in ports and intake setup, you would get a net rise in torque, not a decrease. Yeah, I was seeing that "projected torque" loss from day one of this quandry. I have dismissed this to myself though, believing that the "projected torque curve" would most likely nose-dive, like that of a hp curve after about 400 rpm or so into the projection. Still though, I feel like you that there is something basically wrong right here, I just don't have what I would need to analyze it at all. :confused:

Originally posted by Spin9k
In response to my inquiry to Mazda regarding the HP controversy, I received this reply on Friday 8/7:

"Thank you for contacting Mazda North American Operations.
I appreciate the opportunity to respond to you.

In regard to your inquiry, Mazda is aware of the comments
floating around on the Internet regarding RX-8s not meeting
the posted horsepower rating, and we are looking into the
matter. However, we stand by the current states power levels:
247hp for the manual transmission cars and 207hp for the
automatic cars.
...

...
Again, thank you for contacting Mazda.

xxxx xxxxx
Specialist, Customer Assistance E-Business"

This thread is turning into a repeat of others, so let's keep it all in one place on this thread (http://www.rx8club.com/showthread.php?s=&threadid=7976).

---jps