Hello!

I have a Mini with a D16A9 CRX ('88 non Vtec) engine and gearbox. Because my Mini has smaller wheels (12 inch) my engine makes a lot of rpm.

Question is: is there a sollution to change the final gear to get a higher top speed and lower rpm. Now it should be 3.88, 3.50 would be much better!

Any suggestions?

Best regards,

Paul
The Netherlands
16Vmini.net

 

Is your top speed on track gear-limited?

 

Houseman custom FD's and/or gears

http://www.housemanautosport.com/index.html

 

Not sure about compatibility, but the 92-95 Civic CX (US market base model, D15) had a 3.25 ring and pinion.

 

im pretty sure since you are using the d16a9 tranny which is like the JDM ZC version, you have a 3.888 final drive, the only other final drive i could see you swapping is the US spec 88-91 CRX HF which has a 2.95...

i did a bit more of a search, but it seems that the californians got a higher final drive in the HF, mayb to make them eat more gas... anyways thats a 3.25

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">Is your top speed on track gear-limited?</TD></TR></TABLE>

That's a valid question, I'm building a Honda-based Mini and did some calculations about this issue. With a Cd (drag coefficient) of 0.45-0.50 or so, my Mini is gear-limited to 130mph (at engine red-line). The important thing to note is that at 130mph there's so much aero drag that it takes 150whp to maintain that speed!, practically all the whp my H22A1 puts out. So while a numerically lower final-drive will help freeway mileage, top speed would not change in my case. In your case, with a presumably lower hp engine, I suspect it isn't going to help at all and in fact may give you a lower top speed...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kb58 &raquo;</TD></TR><TR><TD CLASS="quote">That's a valid question, I'm building a Honda-based Mini and did some calculations about this issue. With a Cd (drag coefficient) of 0.45-0.50 or so, my Mini is gear-limited to 130mph (at engine red-line). The important thing to note is that at 130mph there's so much aero drag that it takes 150whp to maintain that speed!, practically all the whp my H22A1 puts out. So while a numerically lower final-drive will help freeway mileage, top speed would not change in my case. In your case, with a presumably lower hp engine, I suspect it isn't going to help at all and in fact may give you a lower top speed...</TD></TR></TABLE>

Lucky.. As of now I am gear limited to 73mph indicated. Seems as though I have a later 12" or 13" box going to 10" tires. That, and a 1275 does not like to rev much higher than 5200rpm!

 

In the most recent issue of Sport Compact Car they have a B18C5-powered Mini, and the owner says he has serious problems with the gearing and small wheels. Good luck figuring it out, as I'd like to do a similar project in the not-too-distant future and would like to know an answer

 

I think the SCC car was running 175-50-13's? I have seen one or two minis that have pulled off a 185-55?-14, but this was with a good amount of work needed..

 

I'm running 215-50/13 tires on the driven wheels, 21.5" tire OD. Like I said above, because of the brick-like shape of the Mini, you need a LOT of hp to go fast. How much is your engine putting out? What good is spending $$$$ if you don't have the hp to make use of it?



Modified by kb58 at 8:00 PM 9/3/2004

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kb58 &raquo;</TD></TR><TR><TD CLASS="quote">I'm running 215-50/13 tires on the driven wheels, 21.5" tire OD. Like I said above, because of the brick-like shape of the Mini, you need a LOT of hp to go fast. How much is your engine putting out? What good is spending $$$$ if you don't have the hp to make use of it?</TD></TR></TABLE>

Right - thats why I am honestly happy with my bog-stock 1275cc and 10" wheels.. BTW - not to hijack the thread anymore than it has been, but I love the fabrication you have done on your car thus-far.

 

Sorry, I was responding to the original poster. Thanks for the complements, I have the next week off so I hope to get lots done!

 

I believe you have the Si model with the 4.28 Final in it ? if that's the case you have 2 cheap options, switch to a 88-91 DX STD or HF box or try to simply replace the final all of the years had increasingly larger flywheels and clutches so consider this when changing the trans

I believe the DX and STD had a 3.8 something final but probably check http://www.d-series.org for a more specific listing


Modified by FF lotus at 8:00 AM 9/4/2004

 

At this moment my top speed is at max RPM.

It's not that I want a higher top speed, it's scarry enough now! Problem is that the engine makes to much rpm (and noise!) at normal legal highway speeds. Engine has enough power, so power for at least the same topspeed (about 190 km/h) should be no problem.

Paul
16vmini.net

 

sir paulus what tranny your are using??? i have the same engine and my tranny is s20 but in my 1st gear and 2nd is to slow. it is posible to use the d15 sohc tranny???

 

*Slaps forehead...*

 

You can only use a FD made for a cable trans. Countershafts are different heights between cable and hydro.

2.95 is the highest you can go OEM.

If you were to change to a hydro box (and for the other guy that posted with the S20) you can use a 3.25 OEM.

 

Have a search for the gear ratios for a Rover 216 GTi/GSi (UKDM).....IIRC all the internals are interchangable with your gearbox.