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Old 10-29-2012, 03:33 PM   #1
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Default top speed of a turboed maita?

What is the expected top end in a typical race prepared miata?

I am looking into class placement for roadracing. My local track is PIR,which has a long (a little less that a mile) straight stretch.

The first time out with my miata was with low boost (12#) and basically an OEM longblock. I think I was able to hit low to mid 130's mph.

This worked out fine when I ran in SPM, which was grouped in with other classes running at similar speeds like pro-3, etc... so at least I had someone to dice with... but no one to "race" with; as a "real" SPM car is way faster than my little t-miata.

The t-miata will also fit in racing class ITE. However, I was really in the way by the end of the straight... as you really need a top speed of high 140's to mid 150's to keep up. Mostly 911's, corvettes and turbo-924's.

I've got a second motor that I've fitted with a forged bottom end. I think I can spool 15-16# on it with my current 2860 set-up + some new tuning.

Q: For those who have built and raced their car, what kind of top end do you see? Is ITE a realistic class for a miata to even try to engage? If not, what classes can you race it in?
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Old 10-29-2012, 03:39 PM   #2
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Depends on gearing...
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Old 10-29-2012, 03:42 PM   #3
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You need a 6 speed and 3.63 rear end.

A turbo miata is limited more by its gearing then power.
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Old 10-29-2012, 03:43 PM   #4
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What he said ^
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Old 10-29-2012, 03:51 PM   #5
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I hit 161mph/rev limit at TWS CW
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Old 10-29-2012, 06:19 PM   #6
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My theoretical top speed is about 140 with my 4.10 gears and a self-imposed 7000 redline. I have only hit 132 on the track due to running out of track. I'm not dumb enough to try it on the highway here.
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Old 10-29-2012, 07:08 PM   #7
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what are the restrictions of your class?
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Old 10-30-2012, 01:44 AM   #8
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Been past 7000 rpm wit a 6 speed 3.636 on the front strait at Pacific Raceway. probably just over 150 Mph. I’ve run a 1:32.5 in my street driven turbo Miata but it is not legal for wheel to wheel. I was right at 10 seconds slower the first Time I raced my not well setup Spec Miata at 1:42.5 mid pack on old tires and 7 seconds slower racing a Pro3 Car while running very competitive Pro3 times at 1:39.5.
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Old 10-30-2012, 01:54 AM   #9
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Tire flex is pretty severe at those speeds. I've been to 7400 with a 6-speed and 3.909s at a couple of tracks, which works out to 154mph on gearing, but the GPS never went higher than ~146mph.
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Old 10-30-2012, 01:54 AM   #10
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I swear when I rode in failflora's car with the gt3071 setup and 3.63 gears, we hit over 140 and we had plenty left over. My 5 speed 4.30 setup bounces off the rev limiter at like 125mph.
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Old 10-30-2012, 02:03 AM   #11
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Quote:
Originally Posted by thirdgen View Post
I swear when I rode in failflora's car with the gt3071 setup and 3.63 gears, we hit over 140 and we had plenty left over. My 5 speed 4.30 setup bounces off the rev limiter at like 125mph.
Theseus picks up 6mph per second in 6th gear. It's still pulling hard at the limiter in 6th.
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Old 10-30-2012, 05:24 AM   #12
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Very rough calculations but you'll need ~325whp to hit 140 at Portland with the chicane. The 4:10 gears will need over 7k to do it with the 6 speed. 3.63 gears will top out just below 160 in the same neighborhood.

These cars hit a horrendous aero wall around 140 and it takes a crap-ton of power to push through it. At ~250whp at the same point at Pacific I was only around 140 (indicated - GPS was 137iirc). My best trap at PIR was maybe a buck and a quarter. I had the car to 150 once but it took a LONG time to get the last 10 mph at that power level. The new track car isn't well sorted yet and still has 4:10s.
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Old 10-30-2012, 09:23 AM   #13
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Gearing is main factor, getting up to 125-130 or so seems to happen pretty quickly. Highest I ever saw on GPS was 126mph with stock 5spd and 4.3.

The one Miata that ran the Silver State in an old video I saw said the car got pretty floaty around 150mph. All of the track guys I've seen here with both the power and gearing to top this also have decent aero.
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Old 10-30-2012, 05:49 PM   #14
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Come on Andrew - step up and offer us a real trans swap... or cut us some 3.3:1 R&Ps - those ******* vettes and gt3s hand our ***** in the straights - I want to own 'em in BOTH straights and the curvey parts
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Old 10-30-2012, 06:16 PM   #15
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Quote:
Originally Posted by hustler View Post
I hit 161mph/rev limit at TWS CW

150+ mph miata club. How did it feel?


Quote:
Originally Posted by thirdgen View Post
I swear when I rode in failflora's car with the gt3071 setup and 3.63 gears, we hit over 140 and we had plenty left over. My 5 speed 4.30 setup bounces off the rev limiter at like 125mph.

Yes. We went to the top of 5th. Sigh. It is hard for me to believe that my car once moved on its own.

6spd/3.63/8000RPM = usable gears. Still shift a fuckton more than other cars though FTL.
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Old 10-30-2012, 06:20 PM   #16
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Quote:
Originally Posted by Faeflora View Post
150+ mph miata club. How did it feel?
Wet dream - he had to clean up afterward and explain to GF
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Old 10-30-2012, 07:05 PM   #17
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Quote:
Originally Posted by GeneSplicer View Post
Wet dream - he had to clean up afterward and explain to GFBF
I am not in the 150mph miata club. I feel death very near to me when I hit 140 in my miata. IS-F however, 170mph felt like 80mph does in the miata.
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Old 10-31-2012, 01:30 PM   #18
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I think that the taller gearing would help me out now, even with my tiny hp.

Even after increasing my redline to 7500 so that I can stretch the gear a little if needed, I still find myself having to shift mid corner... it seems that I'm never in the right gear on my local track.
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Old 10-31-2012, 05:25 PM   #19
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That's not a rear end problem, that's a gearbox ratio problem. Taller gears will make it worse.

If you always want the right gear for any corner, you want a 6-speed (or a gearbox with a similar ratio split, i.e. Quaife's wide-ratio 5-speed).
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