Ive got a 6-speed 3.9 combo @ ~250whp, love it.

 

I have the Quaife internals sourced from FM. It should handle anything you throw at it (Hustler's comments notwithstanding) and it gives you similar gearing to the stock 5-speed. Have a look at FM's gearing calculator to see what you can pull down the straight-aways (Flyin' Miata : Technical info : Gearing calculator). With your R&P and this box, you're good for over 170 mph. Not cheap, but it does offer what you're looking for.

 

Men use 3.909s because they are worth time on track, and men also know that 1st gear is for driving the car on and off the trailer and 2nd gear is for driving around the pits. Think of 3-4-5-6 as the most wicked 1-2-3-4 box you've ever driven, plus a pair of granny lows, and champagne will fall from the skies.

Unless you are an undeniable badass with 375whp, in which case 3.63s might be warranted.

 

Thanks for the good response.

Before i try a 6sp, i give the 5sp a last chance with cooling and oil-nozzles at the 1,2,3 and 5th gear.

 

[QUOTE=Sandro;534890]Thanks for the good response.

Before i try a 6sp, i give the 5sp a last chance with cooling and oil-nozzles at the 1,2,3 and 5th gear.

QUOTE]

I don’t think the seven 5 speed transmissions I have broken were from the oil getting too hot or lack of oil, simply too much torque. With over 300 ft-lbs and good rubber you might make a single track day if you’re lucky with the 5 speed. 250 ft-lbs might go significantly longer but it is still limited.

I have the 6 speed with a 3.909. I absolutely hate it for autocross, constantly having to make shifts between second and third at really awkward moments even with a 7400 rpm rev limit. Autocross typically has fast and slow sections but really no straightaways. 1st gear is good for about 10 feet and will get you from the stage line to the timer start line which is nice but can’t go fast enough in second on the fast sections. Kieth Brown kicks my *** with a DP miata wich is about 500 lbs lighter and has 174!!! naturally aspirated RWHP out of a 1.6l spinning to 9000 rpm. 5 speed on 13” slicks he is however a better autocross driver than me and would probably kick my *** driving my car.

I think I will love it on the track once I get use to 3rd being the low gear I think 3rd through 6th will be better suited for most tracks. I actually think the new 3rd gear will get me off tight corners much faster than I was with the 5 speed when I go to real race tracks.

Bob

 

I suddenly miss my old 4.10 r&p.

 

Swap you my 4.10 torsen for your 3.6

 

Ding ding ding. 3rd becomes your new super-tall 2nd (~70mph), and suddenly the 6-speed box makes a whole lot of sense on track.

 

Yes, i killed the last two 5sp transmissions at the nürburgring gp-course from Saturday to Saturday.

Here you can hear my 3rd gear at 1:25 in the warm-up from the second stint on this track day.

YouTube - TurboSandro's Channel

I measured outside the rearend housing 248F with a temp-sticker and i think the transmission oil could be similar. If you add some offset to the bearings 300F oil-temp could be possible.

 

I wouldn't even dream of ever trying to use a 5speed with any power/track abuse..

I just look at 5 speeds and they self-destruct.

 

What is your Vmax with the 6spd and 4.1?

 

Check post #22 and follow the link. You can calculate for any Miata gearbox and R&P ratio.

 

How often are you gays changing your gear oil in terms of track hours?

 

I achieve a GPS measured speed of 145 down the front straight of my local track, Pacific Raceway. A 6 speed with a 4.10 will only go 147 at 7400 rpm. This is a recipe for disaster in my opinion. Lengthy sustained high load at or near peak rpm creates huge combustion temperature loads and will result in turbos falling off and melted pistons and stuff. I need taller gears than that. I already blew up a GTR powered 323 GTX that didn’t have enough legs for that long straightaway.

With the 5 speed and 3.909 it would do ~160 and a 6 speed with the 3.909 will do 154. in reality to make things last for more than a weekend and not risk an overheat in a 20 minute session I try and keep it below 7000 rpm as much as possible. At 7000 rpm the 6 speed with the 3.909 will do 145, it is the lowest rear end ratio I would consider with the 6 speed. It might even be better than a 3.636 in some situations.

A 6 speed with a mysterious unobtainable 3.308 seems like an interesting combo. It would make all the first 3 gears useful agian. It is nice to not have as big of jump from second to 3rd like the stock 5 speed.

The 5 speed Quafe sets also can be used to make some very effective combos in gearing. Plus the 5 speed trans is 10 lbs lighter than the 6 speed.

Bob

 

But then you have to deal with Quaife.

 

I'm sorry you had such a bad experience with them but all the racers around here that are winning are running quaife diffs. Atleast the E30 racers are anyway.

 

I know several people (real people, not e-friends), who have broken Quaife parts.

 

Have any of these people broken the Miata Quaife gearset? As far as I know, they've held up extremely well. I've certainly had no issues with mine.

 

I know of one trashed Quaife box but I'm not saying who due to professional arrangements.

 

+1

6 speed / 3.9 for boosted cars on the track

Our track rental 99 that makes about 140whp uses a 6 speed / 4.3 which is perfect for it.