toresn 3.9 in 1.6

trader · Postby **trader** » Thu Aug 16, 2012 5:41 pm

I'm in the process of replacing suspension bushes and thought I might drop in a torsen while I was about it. There are plenty of torsens around with a ratio of 3.9 and I was wondering how they go with a 1.6 which I think has 4.3. I know it would be ideal with a turbo but how does the 3.9 go with a motor pulling 10 kw more than stock? I'd like to hear from anyone who runs that setup. First gear is so low maybe it would be okay? Thanks

hks_kansei · Postby **hks_kansei** » Thu Aug 16, 2012 5:51 pm

If i'm doing this right, the ratio is about 10% taller.

So I imagine it would be like driving the car if it had 10% less power.

but it would be better on the highway though.

Magpie · Postby **Magpie** » Thu Aug 16, 2012 6:04 pm

I have found this site a good resource to experiment with gear ratios etc. http://www.cargister.com/calculator-gear-ratio

trader · Postby **trader** » Thu Aug 16, 2012 6:36 pm

Thanks for that. really want to know if there is a "seat of the pants" effect. I put a 2.75 diff in a v8 falcon which initially had a 3.2 ratio and there was a noticable difference in wheel spin power. That was an auto though whereas the 1.6 has a really low first gear so may be an advantage?

Magpie · Postby **Magpie** » Thu Aug 16, 2012 6:49 pm

I have gone from a 4.300 to a 4.100 Torsen diff and I would have to say that it accelerates a little slower (but not by much). However the biggest seat of the pants difference is because it now has the torsen diff and not the final drive difference.

The 3.9 diff was matched to a 6 speed box and not a 5 speed box http://www.miata.net/garage/KnowYourCar/S8_Gears.html.

Postby **NitroDann** » Thu Aug 16, 2012 9:41 pm

10% less torque in each gear.

Simple.

Dann

PeterB · Postby **PeterB** » Fri Aug 17, 2012 4:44 pm

I have a Torsen2 4.3:1 in my NA6 that I got from Mania, so they are around for a price.

I haven't tried a 3.9 with a 1600, but i suspect it will noticeably affect performance. You may be able overcome this by going to a 10% lower profile tyre to make up the difference.

Your speedo will be out by 10% (reading low), but you can probably change the speedo drive to correct it, or Premier Instruments at Dickson used to make up adaptors to change the speedo gearing.

Keith · Postby **Keith** » Thu Aug 30, 2012 4:14 pm

You will definitely notice the loss of torque with a 3.9. . The 1.6 wont pull the skin off a rice pudding to start with. If you dont mind spending longer in a lower gear, or changing down earlier, you could get away with it . I really noticed the loss of torque when I went from 4.3 to my present 4.1 dif in my malibu ,and have been looking for a 4.3 torsen to swap out for a while; but now have decided to get Mania to fit an nb8a engine instead.(My son's na6 has the 4.3 ratio, with the 1800 cc engine swap and that goes like a rocket). Otherwise go 3.9 and turbo it !!!!