bmwe21.net forums

I think that 316 (1.6 not 1.8!!) did come from factory with the 4.1?
I have nothing done on my engine, except for the Weber 28/36 from Mark and a handmade, "free" filter, so the car really seems now to have serious intentions to go faster
(although I don't know the gained horsepower, as I haven't dyno-ed it yet)
Any suggestions on a diff upgrade?
My thoughts are 1)an open diff would do the job, not much power to need an lsd
2)Maybe the exactly "next step" one is the right one? I mean the 3.91 from 1.8 would give me some economy as well as higher top speed, without taking so much of my cute (VERY CUT, especially now) acceleration??

But point 1) and 2) are just my thoughts, and I am still a learner...

Any ideas?

what ever you do, delete 3.45 diff from your options.

3.91 or 4.1 will do the trick. I would leave it as it is..

1.6 / 1.8 / 2.0 came with a 3.91 diff from factory, and the 315 with a 4.10
if you wan't to make your car slower, put a 320/6 diff that has 3.64 ratio
but in your place i would choose something much shorter, like a 4.10

my vote goes to 4.1

I think the 316 1.6 came from factory with the 4.1 (this is what Jeroen's specs claim, as well)
So I think the 3.91 is the option in order to get some more top speed, and some better economy, but a bit slower acceleration.
For the time being, I think I 'll leave it as is, however...

Tres Bizarre

I have measured some time ago a differential from a 316, and that differential was a 3.91. And the thing that surprised me is that I do not think it was ever changed ...
The year of the car was 78 ( pre-facelift )

I think some 316s had an 1.8 engine (maybe for countries other than Greece, because in Greece tax system has always been favourable for small engined cars??)
Mine is an 1.6

Here in Uruguay, South America, E21 316 where import came from Germany, it came`s with diff 4.10:1

316/1 (the 1.6-liter) engine is an engine with power just for the body of the e21.
If you want the engine go a little lower speed on the road, install the differential 3,91:1, but not the 3,64:1 or 3:45:1

If you want more top speed and better economy, install a gearbox with overdrive, more expensive, but the better choice.

Greetings,

Well, I 've already the 5 speed eco garbox.
But what I can see is that I can't get more top speed than before with the 4th, and less than that with the 5th.
However, I don't know whether this is due to the wider tyres...I used to drive on 185/70-13 and have replaced to 195/55-15...So could be that.

(by the way, top speed is around 100 miles)

My 316 is 1.6L, gearbox is the standard 4 changes, and the original differential (4.10:1)
With Solex 32/32, had trouble reaching 160km/h.
With DGAV Weber 32/36, turn out well and wants to go for more!
My tires are 185/70/13

Perhaps you need to adjust the carburetor.

Greetings,

When I had this (original) set up, (4.11, 4 speed gearbox and solex 32/32-and 185/70-13) The car could do around 165 kph on the tacho.
When I replaced the gearbox with the overdrive, (diff, gearbox, carb and tyres remained as above) I saw a couple of times in the motorway around 178-180 on the tacho on fifth gear!
But since I replaced the wheels+tyres,(15"x7" alloys and 195/55-15) the car has had a difficulty to give more than 160 and this is done only on 4th gear.
So I guess it's the tyres
This is why I am planning to replace the 15"x7" alloys by the 14"x6" Alpina replicas that Mark sold me, and the tyres from 195/55-15 to 185/60-14 (??I think that's the proper dimension)-anyway what the tyre calculators will indicate

I have 14"x6" wheels ti put in my 316. They are from a Civic 2002, and look like Alpina.
It need a spacer, about 15mm to get correct offset. I m going to choose 185-65-14.

Maybe wait until you try yours ,

I think that the 14" Alpina replicas I have are OK, from offset point of view, and no spacers will be needed, I'll ask Mark, though
The ones the car runs on right now (15") are sitting on spacers

Still wondering if (with current carb and engine) an upgrade to a 3.91 diff would be really an upgrade or a downgrade in relation to leaving my current 4.10 as is...

Saturday, early morning open highway, and a POLO IV 16v couldn't catch me until 145-150 kmh...

Was really smiling thinking at the guy's face when looking at a 34 year old car leaving his almost all new polo several metres behind!!!

leave it as it is!

you do not have to drive so fast all the time..
next week I'm fitting back 4.1 instead crappy 3.45.
i drove my e21 (when it was still 315 with 4.1 diff) over 190km/h because there was no rew limiter