Author Topic: Fusible link? (Read 4485 times)

AlponaBMW · « **on:** March 14, 2012, 11:10:41 AM »

Howdy,
We're finishing up an M42 swap into our beloved furry chumpcar, aka: The Mutt.

We're using all of the 91 318 engine harness grafted to the car's existing bare bones racing electrical system. We have the diagram for that engine harness/ecu/efi but still have a couple questions.

1. we dont see any overcharge protection in that engine harness unless a fusible link is built into the regulator. Is there anything?

2. we'd love to get a useable signal for our existing 4cyl race tach (2 ground pulses per rev) what about ECU pin #74? We're guessing/hoping that's a processed signal to the 318 tach..if so, any idea its pulse rate or properties?

I think that's it for now, but there will likely be more as we scramble toward Sunday afternoon test driving.

Here are a few pics from early on getting the lump stripped down and prepped
to replace the M10 motor. Did a cool alternator re-locate and pulley swap.
http://www.techstylesdesign.com/Alpona/Mutt42/

Thanks,
Mike

DesktopDave · « **Reply #1 on:** March 14, 2012, 11:31:26 AM »

I have no idea on your questions. But I love your car. IMHO all BMWs should be driven with a sense of humor.

IIRC, the cluster from the donor car will have a calibration number on it's face. K=7784 is what's on mine...might be impulses per mile or some nonsense like that. But without the diff or cluster that's not any kind of solution.

If you're using the '02 cable operated speedo off the tranny, this won't help...but the diff sender does what, nine pulses/wheel rev? Figure circumference, count the pulses per mile & you're good. I thought some of the old 80's BMWs had a cable operated electrical pickup for cruise control. If so, that might do the trick, but good luck finding a functional one. Personally I'd just epoxy a few magnets off the driveshaft & read them with a bicycle sender.

IIRC the e30 has a fusible link in the battery lead but only for the DME/injection electronics. No protection in the starter/alternator circuit AFAIK other than maybe the unloader (relief) relay...

Welcome to the M42Club, BTW!

AlponaBMW · « **Reply #2 on:** March 14, 2012, 12:42:49 PM »

Thanks Dave, that totally answers one of the questions..I didn't think to look at the long 318 battery cable. We'll just put our own fusible link downstream of the alternator to protect everything in case the regulator fails.

The Mutt has been a very good racecar. Hopefully the M42/44 swap will give us similar power more reliably than a somewhat modified M10.

We're using 2002 flywheel & clutch with the 318's 240 tranny. Yeah we know the 240 has a bad rep but its what we have. Plan is to just treat it as a 4sp never using OD 5th. No speedo cable and no use for a speedo anyway but we do need a tach. Worst case if we can't get a useable signal for our traditional tach we'll scab the 318's tach onto the dash.

-Mike

DesktopDave · « **Reply #3 on:** March 14, 2012, 02:54:51 PM »

I'd figure the G240 will be OK with your far lighter car. But you're racing it, likely luck & chance will be driving with you even more than usual...

How's the '02 clutch & flywheel fit? Have any pics or weights? Any need for a shortened slave pushrod or modified TOB? Might be a cheap upgrade for the stock dual-mass in the later cars...

AlponaBMW · « **Reply #4 on:** March 14, 2012, 06:55:49 PM »

Stock 2002 flywheels are about 15-16lbs vs almost 30?lbs for the dual mass.
2002 flywheels can be taken down safely to 11-12lbs. We're using a 215mm clutch assy, I trust the way they Plate and Cover are fastened together more than I do the 228mm, and the 215mm assy is fine below 200hp and 8Krpm

The recipe is fairly simple:
Use shorter flywheel bolts..from 2002 or whatever.

A few of the mainseal cover bolts will touch the back of the flywheel. I've seen in other threads where folks have used a spacer under the flywheel, but I think it is smarter to simply swap them to countersink style heads (easy, just remove, countersink, and replace one at a time without removing the cover.

The slave cylinder is indeed much more compressed with the 2002stuff but it shouldn't cause any change other than a little bit more preload on the throwout bearing. It wouldn't hurt anything to cut a bit off the rod. Even if you don't, it looks to me like there is still enough throwout travel left to run the clutch disc into its rivets..but obviously adding a spacer under the flywheel would take some of that wear allowance.

Anyway, you could also easily surface the 2002 flywheel a bunch to put the throwout back closer to its stock relaxed location. If you have time&tools to work on the flywheel you could also just cut clearance for those seal cover bolts

the 2002 ring gear is about a tenth of an inch bigger in diameter so you need to ovalize the mounting holes on the starter (including the one for the locating pin) so that the starter can pulled away about .050" as the bolts are tightened.
Not sure if I had to do it?, but I also hit the inside of the bell housing with a die grinder to make sure the starter had enough room to move out.

Thats it. 15lbs off the flywheel is a very significant difference. Obviously it requires less energy to spin the motor up each time as you row up through the box which is great, but even better is the free-reving quickness..handy when blipping up to match revs during downshifts.
-Mike
PS I think we'll have the motor and tranny out again this weekend so I'll shoot a couple pics then.

locknload · « **Reply #5 on:** April 20, 2012, 08:05:34 PM »

Tjhose aren't minilight wheels are they? Would love to find a set.