daedelgt

It'll make the drive train loss a little less.

Thing I don't get is that the peak torque looks right in line with what you should expect.

1stRX8

I did notice that. I don't now if the exact ratio is accurate but it definitely starts moving toward the conservative side. Are you suggesting that the ECU will change it's maps after a certain mileage?

FYI: About two hours after I left the dyno shop - a new Boxter pulled in. I had returned to pay the bill and watched the boxter run. It was within a few HP of published numbers (201HP) with a 16% DT loss. It is easier to believe the dyno is working accurately.

TurboSE

It is likely that the ecu will switch to a different fuel map after certain mileage. I know mazda did that to the turbo 2nd gen rx7s. Don't trade it in yet!

MikeW

In every gear (except 5th) power flow into the transmission via an initial gear mesh, then another for the gear you are in. Driving in 5th the power doesn't flow via any gear meshes in the transmission, and the only gear mesh is the ring and pinion. So 3 gear meshes for 1,2,3,4,6, and 1 for 5th gear.

So you could get at best 10% better power to the rear tires

What was the rear tire pressure, 30, 35?

Racer X-8

Can someone please explain the dips in the torque & hp curves @ 4,000 , 6,400 & 7,400 rpm's.?

daedelgt

The extra intake runners are opening creating turbulence for that 1/4 second or so.

1stRX8

I am really only trying to figure out if the car does what Mazda sais it does. I can believe the break-in fuel map theory. Third gear should be in the 15% to 17% power loss range. If that is correct the rear wheels should see about 205HP at 17%. If you say fifth gear is maybe only 8% or so the out put should be - 227. It is still a smidge (21hp) short on power. I am not hugely worried at this point. I will be patient and go easy on the engine for a while and post the results of dyno pulls in another month or so.

I would really like to see what others are getting so that we can get a clearer picture of what to expect. I hope there are a few out there that aren't too chicken to put thier new baby on a dyno.

Racer X-8

This should definitely proove interesting...
http://www.rx8forum.com/showthread.php?s=&threadid=6598

86rx7

That is WAY rich, I own a second gen and ive seen them pick up 10+ HP from leaning out the factory maps. A map that rich will most likley pick up 20+ from leaning out. Here is an image out of a S4 NA rx7's factory service manuel confirming the mileage switch. If the 8 is the same, dont try dynoing it until 20,000 miles. I'd expect gas mileage to pick up after that too a bit.

86rx7

Also torque is about what it shold be because it doesnt get super pig rich untill higher rpm, but i suspect this will go up after 20k miles too, as it starts to get rich at 5000, and torque peak is suppost to be higher than that.

ZoomZoomH

iTrader: (1)

the rpms at which each secondary intake ports opened up?

Racer X-8

OK, having read the 20,000 mile thing, I feel as though I can go to sleep now.
One last thing, so y'all have something to beat up on while I lay my weary head
I can appreciate the new dyno's nowadays, but I've done some more old fashioned dyno testing in the 70's. The method used was definitely not what you would consider to be automated, where a "pull" is done in 9 seconds. It was done by establishing wide open throttle at certain rpms. The head guy would yell "mark!" and the group would record their gage readings at that time. This was done at various rpms throughout the range. Then we would do the math & plot the curves.
This 1/4 second of turbulence might have a dynamically detrimental effect on the whole upper rpm range of the performance curves if the dyno testing doesn't provide enough time for things to re-establish steady state. If, say, you establish a steady 8,500 rpm @ WOT for 5 seconds minimum, would the hp read higher than what was recorded here? You would have to perform both test procedures, one right after the other, I think, to answer that one conclusively.
I'll be dreaming of all your replies. Can't wait to read them tomorrow morning!

MrWigggles

It all comes down to at what point millage, break-in, etc. will our cars do 0-60 in 5.9s?

That's all I care about. I believe these Dyno results are accurate (someone else got 178 a few days ago), but they don't matter as long as we are getting sub 6.0 second 0-60 runs.

I do have another question. How do they get these air-fuel readings? from the OBDII port? They do seem quite rich. I wonder if this also has something to do with the considerably poorer than EPA millage that some people are getting.

One last thing, if the fuel maps do change at 20,000 miles like the RX-7, that is awfully long break-in period. Wouldn't even something like 5,000 be overkill?

-Mr. Wigggles

Ps. I'll be saving a few nickels for an FI system regardless. The extra rich mixture will come in handy then :p

MrWigggles

Here's the graph of the torque from the Mazda press-kit:

MrWigggles

Up to 6000 RPM 1st RX-8's graphs are within the curves provided by Mazda at close to 80%. (20% drive line losses is respectable). It is after 6000 RPM that the engine doesn't take off like it is supposed to. By 8500RPM, the output is 6% lower than it should be (assuming 20% driveline losses) or about 15 Horsepower.

Hopefully that extra 6% will be restored., but the Dyno helps explains why the people who are babying their cars right now aren't typically complaining about power. They aren't past 6000 RPM yet so they don't know what they are missing.

Hopefully the extra power in the higher revs will kick-in pretty soon for 1stRX-8.

-Mr. Wigggles

Lensman

Well presumably it isn't a sticky tetiary port because the dyno graph shows the port opening. Otherwise that would be the obvious culprit right?

86rx7

Definatly not a stuck port, also a stuck closed sixth port would cause a much bigger loss, like 30%+

1stRX8

From experience with a mildly modified 84 GSL-SE engine, I played alot with the 6PI actuators to get a sense of thier importance. The difference between fully open and fully closed wasn't 30%. The problem I had wasn't getting them to open at all, it was getting them to open completely.

My take on the graph blips is that they are the ECU activating a pre-programmed map change in anticipation of the ports opening - Not entirely the ports themselves if at all. When I overlaid 5 runs on one graph the blips happen at exactly the same point, the same shape, and the same amplitude. I would expect that from a computer over a vacuum driven actuator. I do believe the 6PI actuators are fine. I can test them while driving if they are anything like the previous actuators.

eccles

FYI, the port actuators are electro-mechanical on the Renesis, not vacuum-operated.

daedelgt

That would back up his theory even more.

Racer X-8

Yawn.

Oh! Sorry, I just got up - I wasn't refering to this thread, of course. You know.

Mr Wigggles torque chart matches in shape that of yesterday's dyno results (shape, not values) (without the 3 blips) so I'll not try to defend last night's theory of mine.

Eccles, man, why are you sitting @ your computer & not in your new driver's seat? He he

No further comments @ this time...

RomanoM

To boost the break-in theory:

BMW's and to a lesser degree Audi's are famous (infamous) for this.

Most recent example is a long-term Audi 3.0 in Car And Driver that ran 0-60 in 7.2s new and 6.5s at 40,000 miles. This is similiar to the kind of difference you see in some BMW's after 20,000 miles.

Friction!

Gord96BRG

This is the same issue that was suspected with the first dyno pull, isn't it?

1stRX8, could you please tell us exactly HOW you turned off the DSC? If you just pressed the button, then it isn't off. From your description about the warning light coming on midway during your run, you only turned off the TCS, not the DSC.

The owners manual doesn't document the procedure to turn the system off completely - you have to hold down the button for over 5 seconds or more, and then both warning lights will come on. At that point, you can't turn it back on without shutting off the car - the button won't do anything.

Re gearbox efficiency - the reason dyno pulls are usually done in 4th gear is because of the 1:1 ratio in most 5 speeds (and also because it doesn't rev so fast, so transient/dynamic effects are minimized, so a more accurate pull is recorded). The mechanical differences between 3rd gear and 5th gear on the RX-8 might only be a couple of percent, not 8% or whatever you responded with. The typical number of 15% - 17% is for the most efficient drivetrain path, which would be 5th gear in the case of the RX-8.

I'd still say that the DSC is a likely issue with your pull.

Regards,
Gordon

RomanoM

Even though I also put forward the DSC as a possible problem in that other post about a dyno run. And many time that is the issue.

The graph doesn't show that. It the TC part of the DSC cut-in you would see a very clear drop in the torque curve where the system engaged. And the curve after that would look haphazard as the DSC tries to modulate engine power and/or brakes.

There is still a possiblity of the DSC since we don't know exactly what the software code is, it's possible it has a level of very minor modulation on the brakes only that would act like a parasitic power loss.

Theories, Theories, Theories :p

ZoomZoomH

iTrader: (1)

thank GOD!

no more stupid vacuum tubes!!!