mx5cartalk.com

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

JFDI

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.

Sent from my GT-I9100 using Tapatalk 2

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?

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)

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

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

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

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

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.