whats RX8 top speed in 6th gear? - Page 5 - RX8Club.com



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Old 08-26-2009, 03:48 AM   #101
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Originally Posted by kersh4w View Post
i'll say that i dont know what people are saying about the rx8 feeling planted above 135.

the whole car starts to lift up into the air. you can feel it. it feels lighter. to go those speeds safely (and why i've only gone above 135 once) you need some sort of front splitter and a huge gt wing on the rear. the car was still accelerating at 149 (5th gear) though.

interesting thing about 6th gear is that every 1krpm is 20mph. 60mph, we all know is 3k rpm. so, 80 is 4k. 100 is 5k. 120 is 6k. 140 is 7k. 160 is 8k. 180 is 9k.
depending on suspention, the really light nose goes away at about 135 mph..

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Old 08-26-2009, 07:37 AM   #102
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I cannot buy 181....


Even if you were driving down Mt. Olympus in free fall I can't buy 181.


I really doubt a 238hp engine with 159 pounds of torque could over come the car's drag coefficient.


181?
Okay....
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Old 08-26-2009, 08:30 AM   #103
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+1 for the 181, considering corvettes struggle to hit that downhill as well
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Old 08-26-2009, 08:33 AM   #104
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The drag limited top speed of about 146 is beyond terminal velocity for the car. Meaning that that's faster than it would fall if you dropped it out of an airplane.

Going down a mountain is not going to let you hit 181, physics calls BS on that.

Also...coming off a mountain? Show me a mountain road that's straight as an arrow for a mile. No way in hell are you driving at 150+ down a mountain ******* road. Come on.
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Old 08-26-2009, 08:54 AM   #105
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To be fair, downhill does help increase top speed, even though it is past terminal velocity. Having gravity assist you does make a difference. And there are certainly long downhill straights out there. Like Nevada, with highways that they built straight over ridge lines. Kansas, with the center of Kansas is ~1 mile above sea level, eastern edge is under 1,000 feet (I think), etc.

Obviously no one is suggesting doing this on a canyon road or anything. The roads DO exist, even if you haven't seen them.
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Old 08-26-2009, 09:01 AM   #106
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Going downhill does help, but not *that* much. The reason that moderately-powered cars are typically drag limited to about 120 MPH is because that's about terminal velocity, and it takes a lot more power to go beyond that point than to reach it. Drag becomes a wall that the car has to push against.

Going from 150-180 takes an enormous amount of power. Far more than the 8 has no matter what your mods, and a downgrade isn't going to get you there. The main thing you have to overcome is drag, and a downgrade doesn't do anything about that. It does use gravity to effectively increase your power, so yes you will go a little faster, but no way in hell is it going to let you hit 181.
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Old 08-26-2009, 09:14 AM   #107
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I never said "downhill" will get you to 181. I agree about that. I also didn't say what degree of downhill. The slope really does matter, and there are incredibly steep straight slopes out there. Will they get you to 181 in a stock 8? nope. I-70 in western MD out of Cumberland Gap, in either direction, is alot of sweeping curves with posted 9% grade, with some straight sections, and you can CERTAINLY be 120 or so through the curves, and be up over 140 incredibly quickly on the straights. Not that it is safe, just saying it's certainly possible. In my younger dumber days, I did a trip where I was bouncing the 110mph governor on a 115hp Corolla through those highways, with plenty of room to go. I cut out 3 of 4 cylinders of another Corolla in Kansas PAST the 110 governer (and got a ticket for it)

Just saying don't dismiss the entire statement. Downhills help, how much is directly related to the degree of slope.


And I recognize how much it takes to gain speed at that speed. One of the magazines out there did a Veyron calculation, on what would be required for it to get to 300mph. The increases needed of drag coefficient, power, and downforce were staggeringly impossible.
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Old 08-26-2009, 09:35 AM   #108
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I didn't mean that going downhill doesn't help, it does, by adding the force of gravity to the power of your engine. So yes it will help you go faster.

My point about terminal velocity was that your big issue is drag; gravity will pull you through a bit more drag but not that much. Even in freefall Earth's gravity isn't strong enough to take a car drag limited to about 146 up to 181, it just isn't possible.
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Old 08-26-2009, 10:00 AM   #109
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Granted, freefall is sheer gravity vs drag. The power of the engine can't be added at all, or it wouldn't be free fall. I am not good enough with advanced math to calculate this, but I bet that with a 75 degree slope (allowing 15 degrees for some level of traction due to gravity, the rest through downforce, although more side force now), you could certainly surpass even 200mph in a stock 8. Granted, the vertical distance to accomplish this doesn't exist until you built something several miles high, and you have crosswinds etc which would act against your traction...

My point is that terminal velocity is simply gravity vs drag. Engine power + gravity IS a significant contributor, and can't be considered terminal velocity any more. Earth's gravity is strong, but using freefall as a determination of max 'pull' doesn't come close to reality.

I'll use this another way. Freefall terminal velocity in a single engine weak cessna is one speed. If the engine is running max power and you are pointed downward, you can certainly exceed this terminal velocity. Then shut off the engine, you will slow down. Every flight sim out there (Which models these dymanics accurately) will show this. Freefall < Gravity + Engine power.

Last edited by RIWWP; 08-26-2009 at 10:03 AM.
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Old 08-26-2009, 10:09 AM   #110
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Quote:
Originally Posted by swoope View Post
semi plausible.

but 155 gps vs 156 on the tach, Or speedo? but you should have had better luck in 5th.

and if this happened you must have had lot of room..

beers
5th tops out at ~138. 09 = different gearing.

tach, speedo, the little thing that displays the MPHs.


I don't really care if you don't want to believe it though /shrug
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Old 08-26-2009, 10:10 AM   #111
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I didn't literally mean freefall without the power of the engine, in that case you wouldn't even get to the 8s normal top speed.

Freefall gets you to about 120 with gravity alone. Adding the power of the engine lets you go faster. But not as much faster as you think.

The reason I bring up terminal velocity is to show how much drag force we're talking about. That's enough drag to stop acceleration in free fall. And the drag increases dramatically as you go faster.

I think you are underestimating the force of drag at these speeds. No way will you hit 180 on a downslope with an 8, let alone 200. The 8 has neither the power nor the aerodynmics to get there, and the help of gravity isn't enough to overcome that.
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Old 08-26-2009, 10:20 AM   #112
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I'll drop it.

I never said you could hit 180, 181, 200, etc... on a downslope that actually exists in the world. I even said I agreed with you on that. I am not underestimating drag, I recognize it's impact. Drag increases as the square of speed. I get it.
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Old 08-26-2009, 10:29 AM   #113
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I think we agree, it's the freefall analogy that caused misunderstanding.
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Old 08-26-2009, 10:57 AM   #114
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I think the bottom line is:
181 ain't happening in an RX-8 just because you're driving down a hill [mountain].

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Old 08-26-2009, 12:28 PM   #115
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Quote:
Originally Posted by Marklar View Post
Going downhill does help, but not *that* much. The reason that moderately-powered cars are typically drag limited to about 120 MPH is because that's about terminal velocity, and it takes a lot more power to go beyond that point than to reach it. Drag becomes a wall that the car has to push against.

Going from 150-180 takes an enormous amount of power. Far more than the 8 has no matter what your mods, and a downgrade isn't going to get you there. The main thing you have to overcome is drag, and a downgrade doesn't do anything about that. It does use gravity to effectively increase your power, so yes you will go a little faster, but no way in hell is it going to let you hit 181.
Not true, http://www.youtube.com/user/fastlane.../0/TLwB541aJFM this is my RX-8 measured by GPS (True speed) not on jack stands or some else cheats.

EDIT: Sorry I read your post wrong, going from 150-180 I totally agree with you, I really maxed my car out at 262km/h (~160mph?) going from 150-180 needs atleast 100whp more.

Last edited by fastlaneracing; 08-26-2009 at 12:37 PM.
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Old 12-09-2010, 03:35 PM   #116
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I have an '05 with exhaust and intake, and today I hit 144 in sixth. (took 6th from 75 to 144) not really trying hard, but in fifth I've hit 154
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Old 12-09-2010, 04:03 PM   #117
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yay. You're a man now.
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Old 12-09-2010, 04:11 PM   #118
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yay. You're a man now.
he still has to drift around a corner into a siderail, then he is a man.
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Old 07-01-2011, 06:15 AM   #119
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I have an 05 with an AT and I red lined 3rd at around 100mph and then shifted into 4th and got it up to 115 but couldnt get it any higher. It was on flat road with optimal driving conditions, (about 60 degrees farenhiet and dry) and I had the AC off and windows up. Its all stock and I just changed the spark plugs, ignition coils, and air filter, and a fresh oil change. I cant figure out why I cant get more out of it. I'm probably gonna throw a CAI on it. Thinkin about a K&N typhoon.
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Old 07-02-2011, 01:32 AM   #120
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I have an 05 with an AT and I red lined 3rd at around 100mph and then shifted into 4th and got it up to 115 but couldnt get it any higher. It was on flat road with optimal driving conditions, (about 60 degrees farenhiet and dry) and I had the AC off and windows up. Its all stock and I just changed the spark plugs, ignition coils, and air filter, and a fresh oil change. I cant figure out why I cant get more out of it. I'm probably gonna throw a CAI on it. Thinkin about a K&N typhoon.
So, the thinking is that a CAI is going to have this huge benefit when you're going 115mph in 60 degree air. Okay.

Oh, and way to bump a thread started six years ago... and trying to top out a car that only does 125mph with an engine that's running right and has good compression.

What exactly is the point?
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Old 07-02-2011, 11:14 AM   #121
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The point was seeing if any of you had any suggestions other than the CAI since some of you know more about the renesis engine than I do. I'm new to this site and this car and I simply wanted opinions and instructions.
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Old 07-02-2011, 11:20 AM   #122
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And yes I know its pointless to go that fast on public roads. There is a track about ten minutes from my house that I take it to and give it some exercise every now and then and I want it to perform at it best when I compete.
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Old 07-02-2011, 12:09 PM   #123
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That is it's top speed, and a Typhoon will actually make it slower.
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Old 07-02-2011, 09:09 PM   #124
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My '04 hits the rev limiter at 148...
On Grand Turismo 5 that is.
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Old 07-02-2011, 10:16 PM   #125
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damn i only took my car to 120 ill try 145 in 5th
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