I have found out the following from various sites. Apologies for anyone spotting errors for the STi6 ratio's as I could only find a scanned copy of a brochure and it was difficult to read.

Column 1:-UK STi7/8
Column 2:-JDM STi7/8
Column 3&4:-JDM Sti6 RA(choice of 2?)

Gear
1 3.636 3.636 3.063 3.106
2 2.375 2.375 2.062 1.882
3 1.761 1.761 1.546 1.296
4 1.346 1.346 1.151 0.972
5 0.971 1.062 0.825 0.738
6 0.756 0.842 - -
Reverse 3.545 3.545 3.353 3.353
Diff 3.900 3.900 4.444 4.444

I don't really understand how to interpret any of this. For example, whats the effect on changing the ratios on 5th and 6th gear on the new STi UK vs. JDM?

Also, if you were to test each in the same car with the same set up except for the above box and diffs what would be the difference in terms of seat of the pants acceleration?

Damian.



[Edited by SPEN555 - 2/5/2003 12:12:09 PM]

[Edited by SPEN555 - 2/5/2003 12:15:08 PM]

 

Hello Damian,

The JDM STI7/8 has shorter 5th and 6th gearas the UK STI7/8, that means that at the same vehicle speed the JDM drives with higher engine revs.
If at 200 km/h the UK drives with 5000 RPM (6th gear), then the JDM will have 5000*(0.842/0.756)= 5569 RPM.
So with the JDM version you will get faster acc up to a certain speed, but you will have to shift to 6th at lower speed and most likely the topspeed will be lower with the JDM spec transmission.
If topspeed is not important the JDM will give you more acceleration in the higher gears.

Maarten

 

Cheers Maarten.

That is how I interpreted the difference for UK vs. JDM on STi7/8.

Anyone able to comment on new Sti vs. Old STi RA?

Damian.

 

TTT

 

Hi Damien:The shorter/lower the gearing, generally speaking then the better the acceleration. Top speed, or lack of it or high revs at motorway cruising speed may be a consideration. However if first and second are so low that all you get is wheel spin then taller gearing is needed or a different start technique. But another consideration is where the turbo is actually producing boost to avoid bogging down. Another consideration is lag on gear change especially on a big power engine. If lag is signifigant it may be better to reach the quarter in say three gears (two changes) rather than four closer together which give better acceleration but loose out on the time of a gear change and any associated lag.
To work out geared speeds:
MPH/1000 rpm=Tyre Circumferencex60x1000/5280xgear ratioxdiff ratio.
There is a spread sheet somewhere that calculates it all for you and I will attempt to locate for you.

 

Harvey,

Cheers the spreadsheet sounds excellent.

Damian.

 

http://www.geocities.com/motorcity/4601/hpcalc.html
Damian: This is the site you need.It has lots of useful stuff.