BMW Compact Rally Car Build

[pdxmotorhead]

Did you convert to a 1 piece drive line? You should be able to swap front sections to match...

Dave T.

[DaveKern]

Originally Posted by pdxmotorhead

Did you convert to a 1 piece drive line? You should be able to swap front sections to match...

Not sure what you mean about front sections?

Had a local driveshaft shop fab a one piece driveshaft with a slip yolk at the front. Its got an adapter plate to convert it to Jeep/Toyota dimension stuff.

Having a spare gearbox probably isn't a bad idea, but would like to pick one up that'll be a direct swap. From my quick research the ZF box from the 328 is the same unit as in the 1995 M3. Not sure I'm really a fan of the gear ratios...1st is worthless, and 2nd is borderline unuseable too.

Dave

[pdxmotorhead]

The stocker is a two piece unit, (Guibo in the center section.)
Its purpose is to stop harmonics in the drive line. As well as
noise reduction but in your case only the harmonics are important.

If the drive-line hits a harmonic it can suck 16 or more HP away.
(Starts being significant at about 80 to 100 MPH)
If you look at most land speed record cars they have many
segments in the drive-line of different lengths to dampen the
harmonic tendencies. Note, this is NOT balance, a perfectly
balanced drive-line can go harmonic from flex and shock in the
drive train. The longer a segment the lower RPM it can
resonate at and the more harmonic resonant points it has.

On a Mustang with a 350 HP engine road racing we had a single piece unit,
when we went back to the stock style 2 segment drive line we gained almost 15 MPH
on the front straight at our local road race course. We figured out on the
chassis dyno that we had a wicked power loss at about 90 and 130 MPH with
the straight 1 piece driveline.

Cheers.
Dave T

[J!m]

Hey Dave-

Looking at your engine bay photo I see no heat shield for the motor mount... You want that, particularly with Polyurethane mounts...

[DaveKern]

Originally Posted by pdxmotorhead

The stocker is a two piece unit, (Guibo in the center section.)
Its purpose is to stop harmonics in the drive line. As well as
noise reduction but in your case only the harmonics are important.

Hmm, sounds like a quick dyno run some time may be in order to see if we're having this issue at all. The thing about the shift back down into 3rd is that I tried it at various speeds and never once did it go in without a syncro buzz, so thinking it's more likely I bought a less than perfect gearbox.

Originally Posted by J!m

Looking at your engine bay photo I see no heat shield for the motor mount... You want that, particularly with Polyurethane mounts...

Thanks for the info, will get one fabbed up before I take it out again.

Dave

[J!m]

Originally Posted by DaveKern

Thanks for the info, will get one fabbed up before I take it out again.

Dave

Probably easier to look at the original mount from the ti or the donor car- both have the heat shield originally...

[DaveKern]

Got to shakedown the car yesterday. Went better than I expected for a brand new build, but we did have a few little issues.

Issue #1 - diff bushings. I was hoping to use something somewhat soft in hopes of isolating diff noise. Looks like we tried to go a bit too soft on the first go:



Issue #2 was the transmission not wanting to allow grindless shifts from 4th back into 3rd. Looking for a new transmission. If you know of any in the Denver area, please shoot me a PM!

After we got back from the testing we put the car on the scales. Not as light as I'd hoped, but still not too bad considering we've got glass all around and no lightweight body panels.



Dave

[DaveKern]

Now, for shots of the car in its new habitat:













Dave

[BimmerBum]

Very cool!

How much weight do you think the cage added?

[DaveKern]

Originally Posted by BimmerBum

How much weight do you think the cage added?

Guesstimated 180 ish pounds. There's an older homologate cage (but not legal in the US) that was spec'd at 99 lbs but its T45 chromoly and has a few bars missing that curren spec cages must have.

Dave

[Steve K-B]

Hi dave, Ive been following your thread for the last few months (on a couple of forums), its good to finally see some shots of the compact in action! I find its not very often you see a car build from start to finish on the net so thanks for the constant updates.

I may have missed it but did you decide against the Harry Hockly body kit?

Ive just started my own compact tarmac rally car build here in New Zealand and was quite looking forward to hear your reaction about the quality/weight of the kit. Like you I have a big thing against weight!

Steve

[DaveKern]

Originally Posted by Steve K-B

Hi dave, Ive been following your thread for the last few months (on a couple of forums), its good to finally see some shots of the compact in action! I find its not very often you see a car build from start to finish on the net so thanks for the constant updates.

Thanks for the compliments & for following along!

Originally Posted by Steve K-B

I may have missed it but did you decide against the Harry Hockly body kit?

Didn't decide against the HHMS body kit, but rather ran out of funds. Had some changes happen at work where they took away our overtime pay (read: fun $$), so that's why the build stretched out over an extra year too. Still actively looking for sponsors to help out with things, but in this tough economy its harder than ever to find support.

Dave

[tiFreak]

awesome to see it finally driving, any footage from the camera on the side?

[slow_ti]

damn, so sick

[DaveKern]

Originally Posted by tiFreak

awesome to see it finally driving, any footage from the camera on the side?

Unfortunately we only put the camera on 5 minutes before the place closed, so just did a quick pass by the camera guy. Hoping to make some fixes and get some more miles in this weekend. Offroad park season pass FTW!

Dave