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FI Top speed

Old 03-31-2014, 07:32 PM
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FI Top speed

Was wondering what the top speed of RX-8 was with forced induction. Please state any gear mods that you may have.
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Old 03-31-2014, 07:35 PM
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Assuming your RX8 was using the same Trans and Diff wouldn't the top stop be the same whether FI or NA?

It's just on how fast you get there.

no?
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Old 03-31-2014, 07:48 PM
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Isn't it power to push trough the wind resistance?
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Old 03-31-2014, 08:17 PM
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Originally Posted by wcs View Post
Assuming your RX8 was using the same Trans and Diff wouldn't the top stop be the same whether FI or NA?

It's just on how fast you get there.

no?
An NA 8 tops out at 250km/hr limited by wind resistance . A decent turbo would make it to 270ish relatively easily after which gearing will play a part as well as wind resistance.
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Old 03-31-2014, 08:32 PM
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Second time today I have seen this topic

Please refer here where the math has already done for you, add another 6MPH on the 6th if you push it to 9K instead of 8500. IMO tho you would still not have the power needed to get to this speed on the road.

Originally Posted by Carbon8 View Post
Little reasearch and a little math later and I have some results

S1 Dif S1 trans; 16.6944, 10.07436, 7.326, 5.27028, 4.44, 3.74292
S1 Diff S2 Trans; 16.9386, 10.7802. 7.2816, 5.22588, 4.44, 3.69408
S2 Diff S1 Trans; 17.9352, 10.82313, 7.8705, 5.66199, 4.77, 4.02111
S2 Diff S2 Trans; 18.19755, 10.7802, 7.8228, 5.61429, 4.77, 3.96864

Top [email protected]
S1 Dif S1 trans; 39, 65, 89, 124, 147, 175
S1 Diff S2 Trans; 39, 61, 90, 125, 147, 177
S2 Diff S1 Trans; 37, 61, 83, 116, 137, 163
S2 Diff S2 Trans; 36, 61, 84 ,117, 137, 165

Synapsis

S2 setup will provide better acceleration with a lower top speed.
S1 Setup will achieve slower acceleration but a higher top speed

It seems the best setup would actually be a S1 Trans and S2 diff, but considering the S1 trans is garbage compared to the S2 It seems that and S1 diff w/ a S2 Trans is the best all around setup, wish first gear had a little more output torque though.

Side note, if you are looking to enter the 200MPH club it is theoretically possible with a 3.9 diff(Mazmart sells) using either an S1 or S2 trans.
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Old 03-31-2014, 08:44 PM
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Those are theoretical numbers. I want someone to say I have x turbo dynos with x power having gone x mph. Everyone keeps saying gears top out, when they don't, engine has it's limits so you must change gears. 6th gear he engine doesn't have enough power to go faster than 156. Slap a turbo on and you get 165. Gears don't have limits engines do.
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Old 03-31-2014, 08:56 PM
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I am just telling you the potential to actually get to that speed depends on many variables, a rough estimation can be made using the below. Cd is .3, Front Area is 21.6, weight of a base 8 is 3020lbs

Calculate HP For Speed
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Old 04-01-2014, 06:09 AM
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Ok so we are really only talking about the top of the RPM band in 6th gear.

Really a rare place to be for NA or FI.

A place for me which I can't go as my RPM limit is set to 8500 rpm.
Brett wha'cha got yours set too now?

Anyways FWIW, I did a quick you tube search.
Found some good NA runs but not much in the way of boosted. Well I did but it all seemed like a bunch of kids posting their Boosted 8 on some stupid f'n video game.
Who records their video game?
Ah I must be old. GET OFF MY LAWN KIDS!!!!



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Old 04-01-2014, 08:59 AM
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Originally Posted by Hesselrode View Post
Those are theoretical numbers. I want someone to say I have x turbo dynos with x power having gone x mph. Everyone keeps saying gears top out, when they don't, engine has it's limits so you must change gears. 6th gear he engine doesn't have enough power to go faster than 156. Slap a turbo on and you get 165. Gears don't have limits engines do.
I've come to the conclusion that you won't get an answer because no one has done it. There is no place to do it legally and few places to do it on the streets. Even if you entered the Silver State Classic, your speeds are limited for a street car. I believe (if I remember correctly), that you are limited to 187 mph due to rpm redline and gearing. Changing to a 4.10 final gear will increase that higher. But then you would loose bottom end and that's what the FI crowd is going for anyway.
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Old 04-01-2014, 12:41 PM
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Originally Posted by wcs View Post
Ok so we are really only talking about the top of the RPM band in 6th gear.

Really a rare place to be for NA or FI.

A place for me which I can't go as my RPM limit is set to 8500 rpm.
Brett wha'cha got yours set too now?
Mine is just a tad lower (8300) . As far as testing top speed goes .... I have no interest in doing that . I think the fastest I've ever been on a track was 8000rpm in 5th whatever that is .
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Old 04-03-2014, 04:13 AM
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Damn that vid posted above of the turbo 8 took a long time to get up there. When I was in Germany I saw redline in 5th gear many times. I think the car pulls better above 100mph then from a dig to 100.
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Old 04-10-2014, 06:43 PM
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My car in NA form maxed out at 151mph. But to achieve that speed you have to jump the box up to like 140 in 5th then change at about 7500 to pull the rest in 6th. Was purely for testing purposes on a closed test track. Time will tell what she does in turbo format!
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