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PTP turbo'd RX-8 in Car and Driver- july 06 issue

 
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Old 06-15-2006, 10:23 AM
  #176  
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I just read the article (coming late to the ball game as usual) and noted a few things which would slow the car down...

"particularly above about 4000 rpm when the turbo comes on board..."

That's certainly going to make the 0-60 time slower, to say nothing of the 1/4 mile time. The 109 mph trap speed makes me think the car still isn't picking up a great deal of speed on the top end. What does a stock car do in the 1/4 again? I think the turbo is too big for this application, and comes on too late. Like someone else said, won't the Greddy kit get nearly the same 1/4 mile time on far less peak boost? That would tell me that both PTP's kit and Greddy's kit make the same amount of power in the range used to hit 0-60 and the 1/4 mile.

"There's minimal midrange, meaning seriously lazy throttle response below 5000 rpm."

First, throttle response on a rotary is snappier than most any other engine I've driven. Second, perhaps the author should try downshifting? This is an engine which makes an fairly even amount of torque, all across the wide rpm band. It needs to use its transmission as a torque-multiplier to generate snappy thrust. Clearly the author missed out on that point about a stock RX-8. It didn't get to be a 3-time "10-Best" winner with a "lazy throttle"! LOL

19" wheels? Toyo T1-S tires? What, did they just happen to have a mack-daddy pimpin' set laying around? Those 275s ont the rear have to be on at least 10" wide rim judging by the sidewall appearance. This method would stiffen the sidewalls like crazy, making it a very hard tire no matter what the psi inside the tire was, not to mention the distortion of the tires' contact patches. T1-R tires at a minimum, or better still the new Bridgestone RE-01Rs or Advan Neovas! Hell, I'll bet even Nitto NT-555Rs would have produced better times!

160 ft 70-0 distance? Heavy wheels and tires!

Tein suspension? Hmmmm, now there's a mod I'd like to try, especially if they have the dampening rates well-sorted for the car.

I'd love to see the PTP car retuned for the next size down turbo, for much faster spooling. I figure at 3000 RPM, the engine has more time available to burn a boosted mix than it does at 8500 rpm, so why not shove in all of the air and fuel it can handle at that point? Peak power should be set around 7500-8000 rpm, with the waste gate opening about that to keep from overspinning the turbo. 300 quick-hitting hp in a 3100-lb car will trump 390 top end hp simply because you'll spend far more time in the engine's main powerband that way (figure 3000 to 8000 rpm). The engine MUST be making full boost by 3500 for this to work.

These are my OPINIONS, and should not be misconstrued by anyone as facts.
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Old 06-15-2006, 11:35 AM
  #177  
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photomunkey

i just wanted to clear up a few things, i respect your opinion and agree with the complaint about the stock 8 being laggy below 5k rpms, but you must understand that car & driver is trying to explain how the car feels to ppl who have never driven one. so they need to go into detail as to where the power is made and how the car feels daily driving. they said the same thing about the s2000 when it was first released.... no power until 5k and up. but thats just how the car was designed.

the car makes full boost... be it 8lbs or 12lbs.... at 3000rpms, they say it comes alive at 4000rpms because that is where the car starts to make some real power. And the 0-60 and 1/4 times were traction issues, he went 0-140 about 8 times trying to get a good launch. A 109 trap is about a 12.5 second pass if the correct launch was achieved.

We have also tried 3 different sized turbos, and the gt35r was only 150rpm slower than the small turbo we started out with. The small turbo was only capable of about 300hp max and it just wasn't enough power.
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