Supercharger

220 hp Mazda 6s dyno results


Manual: 176 whp

http://www.mazda6club.com/forums/read.php?TID=4181


Auto: 160 whp

http://www.mazda6club.com/forums/read.php?TID=4049

ChurchAutoTest

Elak, I don't know why you continue to try and nitpick this stuff. Put an accelerometer in the car and note the numbers. They will back up the dyno results - or they won't. Pretty simple. Apply a correction for the aero losses if you like. But its still better than trying to use your butt which was the whole point in the first place...

SC

DisneyDestroyer

Hi, please forgive me for asking some probably ignorant questions in this discussion.

First, is it possible that the car simply has a steep decline in performance? For example, that the tested cars were testing in the first few hundred miles, when the engine performs up to spec, but that the engine quickly fills with deposits that modify the burning chamber to limit HP?

Second, is it possible that the ECU changes performance depending on the speed or gear? For example, maybe we get a full 247 HP in gears 1-3, but limited HP in gears 4-6 since it's presumed we're already at higher speeds (6k RPM at 4th gear is around 80MPH, 6k RPM in 5th is around 100 MPH, 6k RPM in 6th is around 120 MPH)? Is there a way to test a dyno with the lower gears (since we have the specific gear ratios for all gears) and calculate that HP, or does it have to be done at the 1:1 gear (5th)?

BenB

Hey guys, did everybody miss the review of the RX-8 in the May 2003 issue of SCC? They said exactly what the problem was! It's the power port valve that's supposed to open at 6250 rpm. It's sticking shut. Read it for yourself. Here's a quote from the article:

"At 6250 rpm, when the high-rpm power ports kick in...well, we're not really sure. You see, our test car, and every RX-8 at this point, is an early, hand-built prototype, and apparently, after a bit of hard use, the power port valves on these prototypes are starting to stick shut.

Mechanically, it's a minor issue, and should be easily resolved, but the effect is huge, almost exactly like driving an S2000 with the VTEC disabled. With the power port valves stuck shut, the engine becomes effectively the same as the 210-hp engine available in base models in Europe and Japan, and in the sissy, four-speed automatic in the United States. We discovered the problem on our dyno, when the RX-8's power went flat at exactly 6250 rpm.

Given the missing 40 hp, we didn't bother doing acceleration tests, but here's the fun part: Several other magazines did do acceleration tests, and we're pretty sure their cars had the same problem ours did. Expect acceleration times to improve dramatically when the production cars arrive. Our car was yanked from our hands the instant we discovered the problem (hence the unknown weight), and a solution is in the works."

The article is here:

http://www.sportcompactcarweb.com/fe...rx8/index.html

There you have it!

-Ben

ZoomZoomH

iTrader: (1)

um, that was on the PRE-PRODUCTION car. Mazda already took care of that in a port campaign before it's released to the dealers.

THAT was OLD NEWS...

Lensman

Old news yes but I'm not so sure it's irrelevant!

Spin9k

or NOT... HOPEFULLY... If we could get our extra 40hp THAT EASY... THE MIND BOGGLES!!!

(yes i'm 'hopefully' yelling)

Lensman

Yes but if it IS that (and who knows?) then Mazda didn't manage to fix it from pre-production to full production so it can't be THAT easy. Most commentators say it isn't an issue because the dyno graphs show the port opening but in my opinion that could be just the ECM altering the power output momentarily as it EXPECTS the port to open. I'm not a mechanical engineer so I expect to get shot down quite rapidly.

P00Man

thats probably TOTALY fixed because, as i recall, the port issue was a PARTS problem, not a production problem, meaning the port wasnt made properly by the manufacturer, i believe

RX-8 friend

I agree with the statement to the effect "we will not know what is wrong (If anything) until something comes from Mazda". However, with previous RX-7s, there is a switch on the odometer (older tech) that did "something" to help with proper breakin (this was discussed on RX-7 lists but I never saw a definitive answer to what it did). This may be what is happening here? Perhaps they limit the effectiveness of the extra ports until 5000 miles? How about we wait until someone reaches 5000 miles and tests as Mazda recommends before we panic?

Bob The Eskimo

I have followed many of these threads for a long time but have just gotten involved. I now own a bunch of rotary engine parts, many assembly hours of workers time, and a blue aluminum hood in Hirosima.
In two or three months I will see my newly assembled ride.

This may have been cleared up already but what gear was the dyno done in? the automatic is geared at a 1:1 in 3rd but the manual is geared to 1:1 in 5th. The dyno would need to be done in 5th gear, right?

I don't know a thing about dyno's so don't flog me too hard for stupidity.

None of the results, good or bad, have stopped me from ordering my 8.

Also, did anyone get a good deal from the dealership? MSRP?

ChurchAutoTest

Mr. Eskimo (hey I was born in Alaska! )

There is a rather common myth going around these last 12 months or so that a dyno test should be done in whichever gear is closest to 1:1.

Simply put, it isn't the gear ratio that matters.

The more complicated answer is this.

1. Power transmission losses through gears do vary slightly as ratios change. However, the difference between losses in a 3:1 ratio vs. a 1:1 ratio is on the order of 1% or less.

2. What we're really interested in when selecting a gear is _load time_. On an inertia dyno, the load applied to the engine is fixed (based on the weight of the system) so the load time depends on that load plus how much torque the engine is putting to the wheels (flywheel torque multiplied by total gear ratio).

On most cars, we want to see a load time of 12-13 seconds on a Dynojet. This is sufficient to give a good time sample without overheating the car. The shorter the load time, the more energy required to accelerate rotating parts, so losses grow. The longer the load time, the reverse, although heat soak can come into play.

In the case of controllable load dynos (like my Dynapack), we can actually set the load time, so gear is irrelevant (save for over torque issues on the dyno's themselves). We've actually done tests in 3 different gears with the same load time and the results were nearly identical.

SC

pelucidor

Bob the Eskimo and RX-8 Friend: I know this is a long thread but I wish people would read it (especially the first few pages) before making comments. This is about the 50th time these same two items have been posted. Some of the dyno tests were done in 3rd, 4th and 5th gears - about 1% difference between them. An older RX-7 had 'something' happen to the ECU at 20k miles to provide a little more hp - this was documented in the technicians manual for that car. Unfortunately nothing similar is documented in the Tech CD that various people have for the RX-8, and no dealership techs have been made aware of such a 'mileage related switch' even after asking Mazda specifically about such a thing - if it was so simple you would think Mazda would tell someone by now.

The other very common question is 'was the DSC/Traction turned off during the dynos'. The answer is YES, in at least all the dyno tests I know about. No doubt this will be revisited in a page or two...

At this point EVERY SINGLE OBVIOUS QUESTION has already been asked, and some VERY KNOWLEDGEABLE dyno experts, rotary experts and tuners have said what they know/think. I wish this thread would only be added to with people providing new real information or new data (especially a Mazda rep), not the same old questions. Forgive me if I am being terse, but every time I see a new post I think we might have an answer or more data, and I get disappointed every time.

RX-8 Zoomster

Pelucidor,

Good post!

Did I tell you, I think it might be a auxilliary port not opening?

Sorry for dragging back into this post with no real answer. :D

canzoomer

I wonder if this problem is only happening on *SOME* of the RX-8's

While I only have a couple of hundred kilometers on my 8 so far, and I have not revved it beyond 7500 yet, I DO feel a definite boost of power above 6000rpm, and it is *definitely* making more power on mine.
No, I did not use a dyno, just my "butt accelerometer", but I definitely feel it makes a lot more power at 7500 than at 6000.

Another wild guess or two:
Maybe the ECU gets some other sensor reading and is not opening the secondary ports on a dyno?

Maybe only some of these are showing the problem??

Maybe the Canadian ECU setup is differnt than the USA one???

BenB

I think this is exactly what's happening. Let's be logical... if many of the pre-production cars had power port valves that started sticking after a while, then it's a problem that will not necessarily happen at the same time (or at all) in every car out there.

And just because Mazda did something to "fix" this problem on the production cars doesn't mean that it actually DID fix the problem. Whether or not the valve sticks depends on firction, heat, and probably other factors, so most likely it's a crap shoot as to whether each car does it or not.

Somebody needs to find where that valve is and inspect it and test it.

ChrisW

If the guys at Mazda who fixed this deserve the title "Engineer" then they will most certainly NOT have just applied a quick fix that made the problem go away on the prototypes, and then forgotten about it.

They will have investigated exactly why the system failed to work as specified, identified the design flaws, fixed them and then tested the hell out of the thing.

Japanese car companies haven't achieved their worldwide reputation for quality by being slapdash over things like this.

In any case, the problem does not look very intermittent. Every production RX-8 that has been put on a dyno has been way down on power. We need to see at least one example of a car producing full power before we can say that only some cars are affected or that the problem comes and goes.

Phinhead54

I've been following this thread for a while because it is the only thing that has kept me from deciding 100% to get an RX-8 . . . just to add data to the mix (and forgive me if this is already in the thread, I don't remember reading it) my brother brought over Road and Track's Special Series "Guide to the Mazda RX-8" marketing piece and they don't have dyno plots, but they do have test results from the quarter mile at 14.5 at 95.6MPH, a little faster then even Mazda rates the car.

May not be important, but it is another data point.

Speed Racer

After listening to all of the chatter about the lack of HP and torque I decided to do something a little more productive than complaining. So I order a Gtech so that I could get some real numbers on the car and stop relying on my "butt dyno". It came in today and I was able to make a couple of runs tonight. After all of the noise about poor performance I wasn't expecting to see anything real promising for numbers but I have to say that I was pleasantly surprised when I was able to go from 0-60 in 6.020 seconds and cover the 1/4 mile in 14.037 seconds at 101.39 MPH! Before anyone asks, I should note that I had to launch it at 8k RPMs to get those numbers. When I tried it at 6k my 0-60 was 7.0 seconds.

If the car is really missing 20+ HP I don't think that it would be possible to do 0-60 in 6 sec and 1/4 mile in 14 sec. What do you guys make off this?

canzoomer

Nice one Speed Racer!

You are Da' Man!

:D

Shamus

You know, I have been wishing more guys would quit whining about hp they think isn't there because they expect more at the dyno, and get out and actually flog the freaking car to see if the test numbers are obtainable - and they are.

Firstly, bravo for launching at that rpm and THANK YOU for providing the datasheet. I like the break-down too, it compares well with what Road and Track tests yielded...

0-30 R & T = 2.1 / you 2.4 seconds
0-40 R & T = 3.2 / you 3.2 seconds
0-50 R & T = 4.5 / you 4.6 seconds
0-60 R & T = 5.9 / you 6 seconds
0-70 R & T = 8 / you 7.8 seconds

And you nipped them in the quarter by .4 seconds. They tested on a very similiar temp day w/more humidity but they did mention that they had to sidestep the clutch at like 7500 rpm to get the times.

Thanks for the info, this is encouraging... maybe Mazda has said nothing to this point because there is nothing to say... That quarter mile time and 0-60 time point to 250hp easily.

RX-Nut

I notice there is a HP and TQ tab.. do those measure HP and TQ? If so, what did they show?

MrWigggles

There have been plenty of people doing 0-60 runs. Speed is the only person I have heard of that has gotten 0-60 in 6 seconds. Everyone else has been in the 6.4 and up range.

I appreciate his efforts and I am sure he performed the test accurately, but his results are unique. A true comparison would be for him to take his measurement system into another car (350z etc.) and drive it just as hard to see what he gets. With his particular Gtech he might get 5.2 or so from 0-60 in a 350z. All the power, torque, velocity, etc. numbers coming out of a Gtech are derived from a relatively low cost accelerometer. It could easilly be 8% off.

I like the RX-8 a whole lot (and have one on order) but the one I test drove did not feel like it could do 0-60 in 6s or less. Yes, acceleration, top speed, etc. are whats important, but a dyno takes the driver error out of the equation and all the dynos to this point show the car is about 10% low on power in the upper RPMs.

-Mr. Wigggles

Digisan

I agree, multiple dynos don't lie...TBC

Phinhead54

Did it give you an estimated HP?