3.1L turbo ix

[The Dark Side of Will]

The max torque of a stock m20 is 164 ft-lbs at 4300 RPM. Full throttle in first gear in an iX is not a big deal because it does not break transfer cases, front diffs, or axles. To find the torque multiplier of your car multiple the desired gear ratio by the final drive ratio. American iX's came in only 3.91(manuals) and 4.10(autos) final drive ratios. Also the first gear ratio in the manual is much higher than the auto (3.83 vs 2.48).

1st gear manual with 4.10 diffs:

Torque multiplier: 3.83 * 4.10 = 15.703

Max torque seen by driveline: 15.703 * 164 ft-lbs torque = 2575.3 ft-lbs.



2nd gear manual with 4.10 diffs:

Torque Multiplier: 2.20 * 4.10 = 9.02

Max torque seen by driveline: 9.02 * 164 ft-lbs = 1479 ft-lbs.

To sharpen the pencil on this a little bit... we know that the 188mm rear end with the 94mm CV joints is good for 500ish HP, so that's not the weak spot.

The T-case splits torque, so with 165 * 3.83 = 632 ftlbs at the input, it sends 221 forward and 411 to the rear.
With 221 ftlbs at the input and 3.91 ratio, the front diff has 864 ftlbs at the output, of which half--432 ftlbs--goes to each axle.

This should indicate how light weight the E30 front drive hardware is. It's really not designed to take much of a beating.

The numbers above are on average. Peak can be much higher due to the operation of the VC in the T-case sending additional torque forward.

However, the E30 front drive hardware is still MUCH MUCH lighter weight than even the lightest rear drive hardware. The front drive hardware uses the same basic dimensions as the 168mm rear, with one large exception. The front drive hwardware is narrower across the carrier bearings than the rear. This means that the diff guts are smaller and weaker. Of all the 168mm units, the E30 front is the narrowest across the carrier bearings, and therefore the weakest.

As a basis of comparison, the same Quaife part number fits the rear end of the Z3 1.9 and the front end of the E53 X5.

[nando]

agreed - a type 168 (small case) rear diff is stronger than the ix's type 168 front diff. everything is smaller - even the pinion shaft is diminutive.

[nomansland92]

Ok so who volunteers to build custom internals for the front diff?

[nando]

Not enough space. The case is too small.

[downforce22]

how about the 525ix front diff?

http://www.ebay.de/itm/BMW-E34-525ix-differential-3-38-Vorne-Diff-1213024-Vorderachsgetriebe-D126-/130971945667?pt=DE_Autoteile&hash=item1e7e894ac3

[Nisse Järnet]

how about the 525ix front diff?

http://www.ebay.de/itm/BMW-E34-525ix...item1e7e894ac3

Got two of those, i can take comparison pics with the 325ix one later on.
I will test the E34 diff durability next year in my 325ix M50 turbo build :)

[nando]

how about the 525ix front diff?

http://www.ebay.de/itm/BMW-E34-525ix...item1e7e894ac3

Its stronger but it wont work with the e30ix oil pan or CV shafts.

[Northern]

Custom spider gears?

[Nisse Järnet]

Custom spider gears?

This im interested in!

[nando]

What are you going to do? You cant make them bigger. That is the problem..

[Nisse Järnet]

Put two extra in and/or stronger steel.
The Finish guy put two extra gears in if im not wrong?

[nando]

Yeah he did that. It still exploded. :p

[Northern]

I'd be happy if they were made of something a decent amount stronger. The oem ones may as well be made of brass.

Also, hasn't "the Finnish guy's" most recent 4 spider gear diff lasted more than a year now? I haven't checked the e30tech thread recently, but he at one point said it lasted a lot longer so far.

[Nisse Järnet]

Yeah he did that. It still exploded. :p

Yes but i was thinking of doing the same thing on a E34 diff might be better? :)
Dont know how much stronger the E34 one is compared to the stock E30 though?

[Nisse Järnet]

I'd be happy if they were made of something a decent amount stronger. The oem ones may as well be made of brass.

Also, hasn't "the Finnish guy's" most recent 4 spider gear diff lasted more than a year now? I haven't checked the e30tech thread recently, but he at one point said it lasted a lot longer so far.

I think it lasted about a year and a couple drag strip passes with like 700-800hp?
Im running boost by gear so i was thinking maybe 4-500hp in 1st and 2nd and then more boost :) Should help front diff!

Specially the E53 diff should be able to take that beating stock? I mean the later diesel version got 500Nm stock and with Xdrive it can send 50% torque up front right?
If used on a 37/63 setup and 5-600Nm torque in 1st gear it should be ok? Well se later on