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RX-8 Performance Data from Texas Owners

Old 08-11-2003, 10:23 AM
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RX-8 Performance Data from Texas Owners

I am sure most of us are already familiar with the 'fuzz' going around the dyno'd 8s. I was wondernig if any owners from Texas had the chance to put their 8s down a dyno, or if they have noticed any unusual behaviour.

I am waiting for my Velocity Red (should be here around by September...can't wait..)

Anyways, I thought it might be interesting to catch the attention of local owners.

Thanks!
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Old 08-11-2003, 11:52 AM
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Re: RX-8 Performance Data from Texas Owners

Originally posted by RX8-TX
I was wondernig if any owners from Texas had the chance to put their 8s down a dyno
Not yet. Mine will be going on a dyno once it has about 1500 miles on the clock, and probably again in mid-September after I return from the Solo II Nationals.
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Old 08-11-2003, 01:36 PM
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I know it's kinda a he said/she said thing...

but supposedly Chris over at Rx7.com put down 197 on their dyno..

http://www.rx7club.com/forum/showthr...hreadid=212917
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Old 08-11-2003, 02:21 PM
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Smile

I guess any claims of better dyno results at this point will make me feel more confortable. However, I did test drive an 8 a couple weeks ago (6MT), and Oh Boy!, I don't know if those were 247 or 150hp (I am not a car-nutts -no offense, I will be soon..) but it felt like driving a little feather through traffic.

I got the chance to put it on the highway (speed limit: 60, everybody going 65~70 though). I took the ramp on 2nd gear, press the gas and got up to 62mph, clunked 3rd and had a hard time coupling with traffic (slow drivers...:p )

Don't know how hard the engine was revving, I was paying too much attention to the dig.speedo.

Anyways, I was kindda turned-off by all the comments on the power loss, and Mazda's silence. I am still wondering what the real figures are, and how Mazda is going to handle it. If the official figures are not accurate and they don't get corrected one way or the other...it is very likely that the 8s deppreciation will be steeper.

Anyone else with information about this?
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Old 08-13-2003, 09:27 AM
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Chris Ott's car made 190hp on the ground at the rear wheels. This is NOT to be confused with rated horsepower at the flywheel, i.e. the figures that you see posted in every article, press release, etc. etc.

Going strictly by rated vs. measured horsepower that would be a 23% driveline loss. 23%?! you say? Yes, 23%. That would be a tremendously huge loss through the drivetrain, more than any other drivetrain I've heard of. The interesting bit is when you take the flywheel rating of 247HP and apply a more standard 19% driveline loss such as I guesstimated from dyno runs on bone-stock 93-95 RX-7's. If you apply a 19% loss to the 247HP Renesis, that comes out to be right at 200HP at the rear wheels. A convenient number isn't it? You can instantly look at a chassis dyno result and know if that bolt-on exhaust system and intake have made a material difference in the amount of HP that your car is making.

There are several theories about why RX-8's right off the showroom floor are measuring a little lower than expected by some number-hungry dyno-queen drivers. One of the more common theories is one that I also heard from the Mazda Protege drivers. They suspect (but don't have any dyno proof) that Mazda's ECU has a built-in break-in period of many thousand miles. Protege drivers have stated that they experienced a much more entertaining driving experience after the 12,000 mile mark. This suggests that there are two different fuel maps triggered by mileage. Again, there is no real dyno proof of that. The ButtDyno(tm) is notoriously inaccurate.

Another theory is that the seals in the engine just haven't bedded in properly on these engines that only have 1,500 miles or so on them. There isn't much spring force on rotary seals so this would be completely possible. In the rotary road racing world many engine builders will use freshly lapped housings but used seals for just that reason. Not because they are cheap but becase they seal better and have lower friction than an identical new seal. Because of those qualities they also make more horsepower.

One thing that I haven't seen anyone at all talk about is the actual break-in of the remainder of the driveline. Since we haven't seen anyone take their engine out of their brand new RX-8 and slap it on a engine dyno, I don't see how you can talk about HP numbers of the entire driveline without discussing the necessary break-in of the transmission and differential. These are friction producing parts with many faces interacting with each other. It's been long known that changing the gear lube with something thinner, say SAE 80, will net a few HP on a chassis dyno at the expense of properly lubricating the transmission or differential. I may be overstating the obvious but nobody has mentioned the fact that the transmissions are new as well.

Now let's look at it from Mazda's perspective. They've just release a new car with a new(ish) engine rated at 247HP. Joe Bob jumps in it and drives it right to Billy Joe's Dyno Shop and Cheese Emporium to throw it on the chassis dyno. They make some pulls and Joe Bob gets pissed. "!$#@$(#@*$!!!! 185HP?!?", he says. After Joe Bob calls up his salesman and pounces on him for selling him a dud car he goes out on the net and posts about how much of a PoS his spanking new RX-8 is because he didn't see 200HP on Billy Joe's chassis dyno. This is where Jed chimes in, theorizing about a dual map ECU program probably used for break-in. Since Billy Joe doesn't have a wide band O2 for his chassis dyno, there is no way to confirm that so it remains speculation.

Eventually Joe Bob's friend, Clem, gets a hold of someone at Mazda and asks him about dual-table ECUs. Mazda doesn't say anything. He asks about break-in period, Mazda says at LEAST 2,000 miles but 5,000 - 7,000 would be better. Clem is a little miffed but Joe Bob still isn't
happy.

Mazda isn't officially going to say that there is a break-in period built into the ECU. Why? He probably doesn't know. Unless you ask the guys that actually programmed (not designed) the ECU, you can't get a reasonably reliable answer. When asked about higher friction in the
engine Mazda probably won't say much either. Why? Same answer, they just don't know.

The vast majority of the people that are accessable to the general public aren't going to be the uber-technical people we'd like them to be. It would be bad for someone not directly related with the development of a given component to say something about how it works with the knowledge that this will be passed to the general public. It's better for them to not say anything than to have someone not in-the-know to say something inaccurate or flat out wrong.
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