6 Speed in NA6 - Opinions?

Jash · Postby **Jash** » Wed Sep 25, 2013 2:36 am

MX5 Humans,
I have a 1.6 NA with a T28 and Haltech that makes around 140 horse at the wheels. Its purely a street car that I might do some motorkhana work in. I like short gearing and I like acceleration. I don't mind changing gears.
I've used the 6 speed Aisin before in an Altezza I had and I like it a lot. I'd be keeping the 4.3 rear end.
All I can seem to find on the net is Americans missing the point of a close ratio box and crapping on about economy and such.
I have a 6 speed already and I can have it slung in cheaply.
I guess I'm just after some verification that the car I envisage with the 6 speed installed will be a fun thing to belt around town.
Many Thanks,
Jeff

davekmoore · Postby **davekmoore** » Wed Sep 25, 2013 3:03 am

sailaholic · Postby **sailaholic** » Wed Sep 25, 2013 6:47 am

Both Tim and Charlie used 4.3 and 6 speed in their turbo track car. Only reason Tim changed is because he was hitting the rev limit in 6th. :grin:

Both lightyear and Mxv97 recon the 6 speed with a 4.3 is the ducks nuts with a 1.8 na as well.

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koop21 · Postby **koop21** » Wed Sep 25, 2013 9:23 am

What do you exactly want to know about 6 speed + 4.3 ? Seems like you already know its a shorter gear ratio and you will be shifting more. To add you've also used that 6speed in another car.

So what's holding you back?

plohl · Postby **plohl** » Wed Sep 25, 2013 10:06 am

May or may not help...

5sp vs 6sp with 4.3 by plohl, on Flickr

Gear ratios obtained from http://www.miata.net/garage/KnowYourCar/S8_Gears.html
Calculated with 225/45R15 tyres (theoretical OD = 583.5mm)

Jash · Postby **Jash** » Wed Sep 25, 2013 12:11 pm

I think it sounds like stellar idea. It just seems like its one of those American Forum things where someone said 10 years ago the 5 speed was better and it just became gospel.
Thanks for all the opinions, gratefully accepted.
Jeff

Postby **NitroDann** » Wed Sep 25, 2013 12:21 pm

Its far far to short geared for a decently setup turbocharged car, it doesnt make any sense from a performance perspective. I had one in my 130ish whp NA6 that was N/A and revved to 8k, it was fun as a street car.

Also do you mean 140kw atw?

Dann

Jash · Postby **Jash** » Wed Sep 25, 2013 12:26 pm

Not too short for a relatively lowly powered one - its only got 140 horse or about 106rwkw. Havent got around to intercooling it yet.
I put a 4.77 rear end in my IS200/Altezza and it was great.
Jeff

Postby **NitroDann** » Wed Sep 25, 2013 12:31 pm

It's not about the peak power its about area under the curve.

If you have a peaky powerband like a F1 car or any lopey racecar n/a build its good, if you have a wide powerband you need ratios to take advantage of that.

Dann

stb · Postby **stb** » Fri Sep 27, 2013 9:55 pm

I think Dan is right - if you have a wide enough torque curve (which you should have with relatively low power turbo) adding another gear will just mean you waste more time changing gears.

Not that I've ever dríven a 6 speed... Would be interesting to do the maths given a dyno plot of your car and Plohl's graph.