1 Series (E87) Tarmac rally car build by Mefmotorsport

[mef]

Maybe I've misunderstood this but I always thought a rear Arb was there to induce oversteer and hence try to neutralise understeer? Surely disconnecting it would therefore lead to an increase of understeer?

[mef]

Hi Martin,
another thread with quite a lot of info on various diffs. You may have come across it already.
http://www.m3post.com/forums/showthread.php?t=788992
So far I have had no problems with understeer on my gravel car, just oversteer on demand. Even when driving it on tarmac on road tyres.
I obviously run a much softer set up than you and I'm also finding turn in much better with the front anti roll bar disconnected. Maybe everything is too stiff at the front?
Regards
Donald

Interesting thread on Bmw E92 stock diff, not highly thought of for motorsport applications it seems, food for thought

[bruvs1]

Disconnecting the rear rollbar destabilises the rear inducing roll , this helps the car pitch weight onto the front corners. Works well in the wet too.. as always its a trade off , a little understeer and some fast corner stability is better than great turn in and not holding traction on fast parts..

[mef]

Having read a lot of comments about the poor performance of the GKN Viscolok E90 M3 Diff in Motorsport applications I have more or less decided to go with one of these modified ZF type units from http://www.limitedslip.de 45% 2 way.

[mrfuzzyfelts]

Having read a lot of comments about the poor performance of the GKN Viscolok E90 M3 Diff in Motorsport applications I have more or less decided to go with one of these modified ZF type units from http://www.limitedslip.de 45% 2 way.

45% will prob be ideal for tarmac, if its too tight or not tight enough at least you can change the thinkness of the plates and play about with it.

Never knew the M3 diff you has wasnt like this.... Learn something new everyday

[mef]

Well it finally arrived today after some hassle with the bank transfer, GRRRRRRRRRRRRRRRRRRRR!

Unfortunately too late now to fit it in time for the Monteberg rallysprint this coming weekend.

Martin

[mef]

The diff arrived too late for installing before the Monteberg rallysprint on 26th April so we did the event on the standard Mlock unit as before. No dramas, 26th from 136 starters, a reasonable result in the wet conditions, I dont think any diff would have had an impact on our result.

We removed the diff over the bank holiday weekend, I also fitted some powerflex black nylon bushes in the subframe ready for the new diff. I was amazed at how soft and sloppy the standard M3 bushes were! Made of foam.

The new LSD is soon off to Hugo Kennedy in Chester for installation and setting up in my diff housing. Hugo is an ex RED transmission specialist so he knows his stuff when it comes to LSD's and CWP backlash settings etc!

Martin

[mef]

Hi all,

I forgot to do an update.....

I got the new LSD installed, no time to test drive it, we went to do the JRT Enville stages rally at Anglesey circuit a week ago.

The new ZF plate diff definitely seemed to be an improvement over the original M3 M-lock unit, I was able to get on the power earlier and get the back end out a bit more easily. It hasn't solved the understeer problem but its certainly nicer to drive and more predictable.

Unfortunately our event was cut short when I noticed that the engine temperature was getting way too high during queueing for SS8 start. (I can normally leave this engine idling all day and the temp is constant 89 degrees) I pulled out of the start queue and found that the electric fan had stopped working for some reason. The relay was pulling in and there was volts on the fuse but none at the fan end of the wiring. I tried to go to the start but the cooling system cried enough and spat out its contents, the organisers stopped me from starting the stage. I later found that a crimp tag had pulled off the back of the fuse box hence no volts to the fan, looks like the wire was a bit short and was under slight tension, could have happened at any time over the past few years! By the time I'd fixed it it was too late to carry on so we packed up and went home.

Martin

[mrfuzzyfelts]

Shame about the Fan problem etc

Glad the diff is better, did you try without ARB'S or not tried that?

[mef]

Shame about the Fan problem etc

Glad the diff is better, did you try without ARB'S or not tried that?

No, we never altered anything, we were having such a good fun time I just drove it!

Martin

[mrfuzzyfelts]

we were having such a good fun time I just drove it!

Martin

The joys of rallying a RWD bmw

Do you know what the breakaway torque is on the diff now? 1 wheel up and torque wrench jobby?

[mef]

No but I will check this next time I get a chance!

I have just removed the S50B30 engine and fitted a newly built high spec S54B30 version (which I've been building now for almost 18 months). The new engine is up and running and nearly ready for a short road test then for a mapping session. I am currently making a brand new wiring loom to suit the new engine and also have a new exhaust sytem is planned before mapping (Ive cobbled up the existing system temporarily to the S54 down pipes which are slightly different.).

The old S50B30 engine is now for sale as a complete unit, complete with a brand new DTA S80 ecu and existing wiring loom, just need a clutch and its ready.

some pics soon,

Martin

[mef]

A bit of a disaster with the new engine on the Promenade stages rally a couple of weekends ago!

Whilst running well and feeling very powerful all of a sudden the engine started to misfire above 5500rpm.

The fault was traced to the front crankshaft damper/trigger wheel which had split apart so the crank signal to the ecu was all over the place! (rubber bonded part)







It seems that this is a well known failure and after all, its probably 20-25 years old and didnt like the extra 1000rpm over the original S50 engine!

I'm looking into making something up from a steel plate since the VAC motorsports replacement part is over $1000 from USA plus postage and import duty!

Martin

[is-si]

Hi Martin,
Perhaps return to the s54 inductive sensor on the crank, to make the pulley design simpler.
Are you not concerned that the OE pulley must go someway towards keeping the harmonics moderately under control?
J
p.s. . . . . i've gone a long time without posting, I must start to work less and post more!

[mef]

I can't because I have an s50B30 crank so no way of fitting the internal crank trigger wheel. I was hoping to make an all steel damper with integrated trigger wheel similar to the offering from VAC motorsports.