racerdave

From reading the Canzoomer threads, as the dyno indicates, the gain is only 5K+.

A lot of people are saying that the stock gearing is a bit too tall to take advantage of the high peak power -- at legal speeds.

Are there any final drive upgrade options available for the 8? It would seem like a shorter final drive could be a good mod in combination with the Zoomer mod.

Any thoughts?

emailists

I too would be interested in how a final drive ratio change would affect the car. (ie giving some more torque down low)

ANyone know about this?

MrWigggles

Racer,

To answer your question, yes they are made. FEED in Japan makes a 4.7:1 which is 6% shorter than the stock 4.44:1.

You can order it here:

http://www.jt-imports.com/FEED_RX8_Parts_List.htm

However, I think it is important to point out that while yes you will be utilizing the higher RPM band you will also need to shift more.

On a quarter mile run, you will likely never be less than 5K anyway if you shift at 8500.

In general I don't think it is worth it but especially in this case where we are talking about $800 for a 6% difference. (going with 225/40-18's would also create an almost identical effect and reduce the weight of your wheels in the process)

-Mr. Wigggles

Ps. if you want to be real technical, the increase in torque can be offset somewhat by the increase in parasitic inertial losses (not frictional) in the transmission do the shorter gearing. The 6% shorter gearing would increase losses by factor of about 12%.

racerdave

Good point about the tires and gearing.

That would do it.

My only concern then would be less sidewall height, but it might not be a big deal.

As for shifting... if you have an 8, then you *gotta* love shifting.

The big thing would just be that in any given gear, the "happy zone" wouldn't take as long to hit.

And actually, the 225/40/18s mean a lot more tire choices (although the speedo will be off a bit on the fast side).

j9fd3s

it would be at higher rpm at freeway cruise too though.

amartin

And you'll need a 'yellow-box' (search on s2ki.com if you want to find where to get one)... to fix the speedo error.

-- Aaron

racerdave

Or, better yet... combine the lower-profile tires *and* the diff ratio and get a car that really uses all 6 gears. :D

More shifting, but quicker access to the power.

Jhouse

and if we drop down to a 35 series tire?

Japan8

Depending on the tired you use, isn't it almost the same price for the tires as it is the rear-end? Installation costs may differ, but tires wear out faster than gears do...

Fab 8

Japan8,

Have you come across any tests in Japan on the FEED shorter final drive? Any acceleration results etc? Thanks.

syntrix

http://www.blackrobotics.com/

Been using them on bikes that are re-geared for years. Even got an extra in the garage.

The question is... is it a single pickup for the speed or is it averaged over the speed sensors on all 4 tires. Consult the tech manuals, it's not very clear on which way it is.

canzoomer

If you want a lower final drive ratio there is a much simpler method:
Buy 17" wheels and use tires with the same aspect ratio.
For example, i am running 17" winter wheels, and 215/35/17 Nokian WR tires and have a 5% shorter drive ratio.

MrWigggles

Too busy to read the whole thread these days?

-Mr. Wigggles

canzoomer

Sorry, how so?

I am not "getting" the reference..

He asked about final drive ratios and I mentioned the simplest method..

What did i miss?

racerdave

Um, Mr. Wiggles already gave that same answer.

And then I added, well, why not pair the smaller tires with the gear and have even more aggressive gearing?

That would be just what the 8 needs, IMHO.

And no, I don't think it would be too much shifting.

But keep in mind that my favorite toy in my garage is a shifter kart that goes best when between 10 and 12.8K, so I don't mind shifting at all.

canzoomer

I realize what you mean. In gentler daily driving I usually shift 1st, 2nd, 4th, 6th. Sometime 1st, 3rd,5th.

One does not need that many gears in light throttle and in traffic.