Gearbox Weights

[Dom-PZ]

Is the 5 speed lighter than the S1 6 speed does anyone know?

I'm undecided which to use in the Westfield. The 5 speed ratios may be a bit long, but with just over half a ton to shift it might not be such an issue.

Uncle Google is not being conclusive

[SprintRX8]

May be worth dropping Boosted a PM DM

As he ran a Rotary powered Westfield

viewtopic.php?f=104&t=70988

[Dom-PZ]

Great minds think alike - caught up with him on a track day last month

[rameshr]

Would be interested to know as well


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[Conan]

Go with the 6 speed every time
The static weight will make no difference but the gears could give you seconds
Regards
Pete

[Dom-PZ]

I wouldn't be surprised if the 5-speed is slightly heavier.

It's basically the same 'box that was used for the RX-7 FD, designed to handle the torque from that engine with twin turbos.
The gears and bearing are each significantly wider, even though there's one less.
The case has a centre internal partition, which is why it has two separate oil drain plugs.
For the RX-8 installation the tail of the 'box was extended, so the length matched the 6-speed and the same cf propshaft could be used.

[Dom-PZ]

Thanks both, the ratios I was sat on the fence on (I'd be using 4th frequently on track with the 6 speed, but rarely with the 5), but hadn't considered that the internals of the 5 speed would effectively cancel out the weight of the 6 speed. I think I'll go with the 6...

[rameshr]

Well I am on my 3rd 6 speed box, I use the Rx8 for rack use. I have been unlucky in the secondhand ones I bought.

I will be going 5 speed just so that the box will last longer. Planning on doing a lot of track work next year.


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[boosted]

I used the 6 speed but i never weighed it. But i can pick 1 up on my own easily whereas a bare 231 block i cant so id say its marginally lighter than a 231 bare block if thats any help atall.
My Westy being a narrow live axled caged car fully fuelled weighed 560kg.
The only issue with the 6 speed is synchro wear and on my car i never hurried a shift else it would snitch into gear. Nice precise change and all all ok.

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[Paul_13]

I had a 5 speed box on the mx5 (rx8 231 engine) and it was horrendous. Completely the wrong gearing. I was doing 88mph in 2nd gear at 8k rpm. It was falling off the power band and completely ruined the car.
I'd stick with 6 speed if your diff ratio is similar to mx5 nc (3.9:1)

[rameshr]

Warp has some pretty graphs

viewtopic.php?t=79248

for me its about reliability, I am going to learn how to swap the boxes over myself. In the next 3 months I should have a small garage so hoping to do this work and save money. Worst case I go back to 6.

not sure what the diff ratio is on a 231 diff

[Dom-PZ]

I had a 5 speed box on the mx5 (rx8 231 engine) and it was horrendous. Completely the wrong gearing. I was doing 88mph in 2nd gear at 8k rpm. It was falling off the power band and completely ruined the car.
I'd stick with 6 speed if your diff ratio is similar to mx5 nc (3.9:1)

I've got 3.6, 3.9 and 4.1 in the garage at the moment, doing calculations based on the 4.1 and of course, with the dinkier 195/50/15 tyres. I'm not going to be running the standard intake so won't have all the valves trickery to improve performance in the midrange... so if the standard 231 drops out of the power band I'd be very exposed!

[Paul_13]

I found the 6 speed box with 4.1 diff is the perfect combination for the mx5. (17"wheels)