Hybrid gearboxes. In search of the perfect gear ratios.

[saxophonias]

We know that several gears can be swapped in s20 and s40 gearboxes along with various final drives so as to have short and closer gear ratios for N/A set ups, or just the opposite for turbo applications. So, at this topic we are going to discuss the various possible combinations in relation to dynoplots so as to see how the power is delivered. This is a must in order to take full advantage of engine power.

[saxophonias]

A good project for a d14 that pulls hard up to the limiter and revs a lot, would be to combine some gears from a4 and a8 gearboxes.
Just to remind you

d14a4
1--3,250:1
2--1,909:1
3--1,250:1
4--0,909:1
5--0,702:1
FD--4,058

d14a8
1--3,250
2--1,782
3--1,172
4--0,937
5--0.750
FD--4,437

So the ideal would be to swap on a a4 box the 4, 5 and FD, or to an a8 box the 2nd and 3rd of a4. In any case the gears will be even shorter and closer, apart from 4rth which is going to move a bit away.

In my ej9 i have the d14a8 gearbox in combination with shorter tyres 3%, so the actual km per gear are even less.
I have measured with GPS that when the dials show 180km (4rth limiter) the real km/h are 168. So it's pretty short. This isn't creating any problems though.

[Dodo Bizar]

Some D14A3/A4 have a 4.250 final gear... I suppose I got it. In 5th gear with 4000 rpm on the dial I have exactly 140 kms on the dial. Some people do that with significantly less rpm or more kms.

The exact distribution of final gears (4.058 versus 4.250) is unknown to me, seems a bit random, mayby year of build is involved?

[Raimundo]

My D14A2 original gearbox was exactly like D14A8 gearbox, so I had the same relations you have in your gearbox Saxophonias.

My ISB had worn out, like most S20/S40 old gearboxes, so I bought one S20 from EH9 ESi Civic. My FD is 4.250, and my 4th gear is longer than D14A8 gearbox.

Will upload a program to rapidshare, that my father developed, so we can put in gear ratios and compare Speed vs RPM. I'm entering work in an hour, and will leave in five, so will update us from there.

[saxophonias]

keep us posted. There is the possibility of swapping gears from ZC engines which are very short and close together.

[Raimundo]

Download the file, here.

Have fun

[Dodo Bizar]

As in that topic, I got the 4.25 .

Question that ran my mind a time ago: HRV have D-series engines isn't it? Have they similar gearboxes? I am afraid not since wheelbase is smaller... but if they are compatibly look at those ratios, even shorter isn't it?

[Raimundo]

Dodo, probably the gearboxes are compatible. Since chutch is hidraulic, and D16 Shortblock is the same, difference might be only in the shift linkages.

Will try to find out.

[hondaNickx]

The best thing i've found so far is getting either a EG3 D13 s20 tranny which is shorter then the D14a8 tranny .Or build one...

D13 hydro tranny is

1st : 3.250
2nd: 1.900
3th: 1.250
4th: 0.900
5th: 0.750
FD: 4.437

I like this setup which i may build :

D16z6 transmission with Z6 axles Cause D14 axles are 22mm VS the 25mm Z6 axles.Also the Main differential bearings on all D13/D14/D15 transmission are 35mm ,most D16 Uses 40mm not all of them though.

1st: 3.083 (Aftermarket Mfactory)
2nd: 1.900 (Stock D16z6)
3th: 1.346 (Stock D16a9 Crx)
4th: 1.033 (Stock D16a9 Crx)
5th: 0.750 (Stock D13 5th or others)
FD: 4.9 (Aftermarket Mfactory)
And a Obx LSD or i'm maybe getting a Mfactory piece.
This transmission beats the hell out of a B16 tranny

Or this is a cheaper option :

D16z6 transmission with Z6 axles:
1st: 3.250 (stock z6)
2nd: 1.900 (Stock Z6)
3th: 1.346 (Stock D16a9 Crx)
4th: 1.033 (Stock D16a9 Crx)
5th: 0.771 (Stock z6)
FD: 4.437 (Stock D13 EG3)
And a Obx Lsd.

I got my D16a9 (L3) crx transmission for 50 euro with bad bearings.
3th and 4th were in great shape.
A D16z6 transmission cost around 100-150Euro around here
A D13B2 transmission cost little less then the z6 (80-120euro)
Obx Lsd is around 250euro on ebay.

So basicly this all ads up to max of 570 euro with some new bearings and seals around 650-700.It all depends how expensive you can get the parts offcourse .If anyones interested i'll be selling my Obx Lsd with new bolts and washers for 200euro shortly.

[saxophonias]

So actually if you swap 2nd and 3rd gear from d14a4 gearbox to the d14a8 one then you have the gear ratios of d13b s20 tranny. Is this possible? I mean to swap only some gears?