Motor Mount Options?

[Z3_GoCar]

I've started purchasing parts to put the race car back togeather. One thing I've though alot about but haven't pulled the trigger on are the motor and trans mounts. I'll just go with stock trans mounts, but what about the group-N or equvalant motor mounts? I'd rather have a mount that hold up a little better and doesn't allow the motor to come loose and start banging around like it did. I've got to replace the trans-cross member and shift linkage, and maybe the oil pan because the mounts broke. Just how legal are the factory replacement motor mounts?

James

Btw, I was just kidding about loading up the spare tire tray with dirt....

[Greg Amy]

I'll just go with stock trans mounts...

You mean, the ones allowed by the rules...?

...but what about the group-N or equvalant motor mounts?

You mean ones that are not allowed by the rules...?

Hey, just sayin'...

[Knestis]

My engine stayrod is about 4" long and goes from where the rear engine mount bolts to the subframe, to where the rear engine mount bolts to the block.

K

[Z3_GoCar]

You mean, the ones allowed by the rules...?


You mean ones that are not allowed by the rules...?

Hey, just sayin'...

Acutally, since hardware is free, on the trans mount I was thinking about cutting off the stud thats welded to the steel plate on either side of the hour-glass shaped block of rubber, and drilling a through hole and using a bolt to hold the mount down. The real weekness of the stock mounts is that they're basically rubber bonded between two plates and we all know what happens to rubber when its stretched...

As for the Group N parts, they're made by BMW. When I did a search on Real-OEM there's like four part numbers listed. Is one of these better than the others? It seems to me if one wasn't filled with that silicon fluid, it might be stiffer.

As for a stay rod. I don't know where I'd connect it between the motor and chassis. There doesn't seem to be a good place to do that on either the BMW motor, or the chassis. Does anyone have pictures of this on a BMW?

James

[Greg Amy]

My point, James mah man, is that the rules do not allow alternate motor mounts. At all.

It's a point that's snagged more than a few folks, myself included (I showed up at the '03 ARRC *assuming* motor mounts were free...when my good buddy Tim pointed out that the red poly motor mounts were a bit much - and I re-read the rules - I recognized my mistake).

And don't you think the "cutting off of studs, re-drilling through the mount" bit is stretching the 'hardware is free concept' just a tad...? I mean, hell, if that the case, I should be allowed to drill and through-bolt my crankcase, right? I could also use a little bit more strength in control arms, too, now that I think about it... - GA

[JoshS]

James,

My take is that if the BMW parts book (ETK, available online as realoem.com) shows a part as a valid part for your particular car, then it's a valid part for your car. I did a search and there are two different (three, but one has been superceded) part numbers for engine mounts for the 2.8L Z3. I have no idea what the difference is. What's the Group N part number?

Here's the realoem search for the Z3 2.8 roadster (yours is a CJ33, right?):
http://www.realoem.com/bmw/showparts...96&hg=11&fg=10

In my opinion, any of the three listed part numbers would have to be ruled legal ... but no others. Is one of those the Group N part?

EDIT: looks like the Group N part number is 11 81 2 224 413. Not listed for any US car. Sorry, no go.

[Z3_GoCar]

Hey Greg,

Point taken, that's why I'm asking questions before pulling the trigger and buying non-alowed parts. None of these mounts that I'm researching are urethane, they're all solid rubber that remove the silicon gel damping fluid, and are built like stock mounts.

Josh, thanks for finding the part number for the group-N mount. I performend a google search looking for that and wasn't able to come up with anything. The cars a CJ33, build date of 10/96. As for aftermarket sources for parts, how about these mounts:

http://store.bimmerworld.com/shared/...t=products.asp

James

[Greg Amy]

:giles:

[Andy Bettencourt]

I guess I am confused here. ONLY STOCK motor mounts are allowed. That doesn't mean stock in Europe, it doesn't mean 'made by BMW' - it means what came on your car from the factory.

[shwah]

- it means what came on your car from the factory.

when the car was purchased new in the United States, OR a part that the manufacturer now supercedes in place of that one in the United States market.

[Ron Earp]

Point taken, that's why I'm asking questions before pulling the trigger and buying non-alowed parts. None of these mounts that I'm researching are urethane, they're all solid rubber that remove the silicon gel damping fluid, and are built like stock mounts.

If all the stock parts have silicon gel dampening fluid, then your replacements MUST have silicone gel dampening fluid. No way around that. Sort of like that dual mass flywheel BMW (and Porsche) used on a lot of cars - if it is stock you've got to use it, can't replace it with a conventional flywheel.

[Greg Amy]

when the car was purchased new in the United States, OR a part that the manufacturer now supercedes in place of that one in the United States market.

...noting that, "...Documentation of the superseding parts or assemblies must be supplied to the Club Racing Department and the appropriate part numbers listed on that particular model’s specification line."

Both in same paragraph, ITCS 9.1.3.C.

[Z3_GoCar]

...noting that, "...Documentation of the superseding parts or assemblies must be supplied to the Club Racing Department and the appropriate part numbers listed on that particular model’s specification line."

Both in same paragraph, ITCS 9.1.3.C.

9.1.3.C top of page 330 "Stock replacement parts may be obtained from sources other than the manufacturer provided they are the exact equivalent of the original part." So who says whats the "exact equivalent?" For anyone who can go down to NAPA to purchase such parts, do you run a frequency analysis spectrum to make sure the Chinese made part has the same polymer/cure ratio as your old part? Or do you just look at it and say, "Well it generally looks like the stock part, the holes are in the right spot, and it looks like it'll fit." If you were to even perform a simple test like a durometer on the rubber, what kind of value and more importantly what kind of error range would there be, and how does it change over time?

Remember, I'm not talking about orange poly's... I'd think the earlier list and documentation would only apply to the factory parts. On my car I could supply about a dozen or so of those superseeded part numbers, but they're not on the spec line right now.... Then multiply that across all the different cars, and our spec lines will grow much longer. I don't think the ITAC wants to get in the bussiness of part number management, not when you're getting ready to even get rid of the model (vin) numbers you have under your control now. I think the test is, "Does it look stock?" is about as close as we're going to get. Aluminum?? No, Orange/Yellow/Green/Black Poly?? No, These?? you tell me.

James

[Greg Amy]

Hoo-boy...here we go...

[lateapex911]

Well, ask yourself. You know the rule means stock. Do you think it's the same as stock. Really?

...on the other hand, replacement parts can easily fail a protest if they are deviant.

[Ron Earp]

James, in your case they need to have silicone dampening fluid and look stock. In my case they need to be made of rubber and look stock.

I'd like to use aluminum mounts get rid of the rubber ones that last 9 months. You'd like to get rid of the squishy BMW silicone filled ones and go to hard rubber, plastic, aluminum, or something like that. Neither of us can legally do these things the way the rules are written.

Ron

[JLawton]

9.1.3.C top of page 330 "Stock replacement parts may be obtained from sources other than the manufacturer provided they are the exact equivalent of the original part." So who says whats the "exact equivalent?" For anyone who can go down to NAPA to purchase such parts, do you run a frequency analysis spectrum to make sure the Chinese made part has the same polymer/cure ratio as your old part? Or do you just look at it and say, "Well it generally looks like the stock part, the holes are in the right spot, and it looks like it'll fit." If you were to even perform a simple test like a durometer on the rubber, what kind of value and more importantly what kind of error range would there be, and how does it change over time?

Remember, I'm not talking about orange poly's... I'd think the earlier list and documentation would only apply to the factory parts. On my car I could supply about a dozen or so of those superseeded part numbers, but they're not on the spec line right now.... Then multiply that across all the different cars, and our spec lines will grow much longer. I don't think the ITAC wants to get in the bussiness of part number management, not when you're getting ready to even get rid of the model (vin) numbers you have under your control now. I think the test is, "Does it look stock?" is about as close as we're going to get. Aluminum?? No, Orange/Yellow/Green/Black Poly?? No, These?? you tell me.

James

However you want to "try" and justify it...........


What do you think is the intent of the rule??

[dj10]

James,
This is pretty easy but let your conscience be your guide. 1. use the stock motor mount if you want to be legal. 2. Use something else and cheat. Honest, it's that simple.
I will say this, I don't like the rule. I doubt very seriously that you would win any races because of a better engine mount. I'm 99.9% sure I would never prostest anyone because of a engine or transmission mount. That said, I didn't write the rule, I just follow what is written the best I know.

[Z3_GoCar]

Thanks all, I will do the right thing. I think that BMW and aftermarket parts makers are not so wedded to what a stock part is. I don't know what the differences between the three parts listed in the ETK, but I can find what other vehicles that they go on so here's what I found:

The discontinued part: 11812228298
also is listed for:

E36 M3 CONVERTIBLE
E36 M3 COUPE
E36 M3 SEDAN


E46 325xi TOURING
E46 325xi SEDAN
E46 330xi SEDAN
E46 M3 CONVERTIBLE
E46 M3 COUPE
Z3 Z3 2.5 ROADSTER
Z3 Z3 2.5i ROADSTER
Z3 Z3 2.8 ROADSTER
Z3 Z3 2.8 COUPE
Z3 Z3 3.0i COUPE
Z3 Z3 3.0i ROADSTER
Z3 Z3 M ROADSTER
Z3 Z3 M COUPE

For both parts numbers 11817837985 and 11812283798:
are listed for:

E36 M3 CONVERTIBLE
E36 M3 COUPE
E36 M3 SEDAN


E46 325xi TOURING
E46 325xi SEDAN
E46 330xi SEDAN
E46 M3 CONVERTIBLE
E46 M3 COUPE
E85 Z4 M3.2 ROADSTER

E86 Z4 M3.2 COUPE

Z3 Z3 2.5 ROADSTER
Z3 Z3 2.5i ROADSTER
Z3 Z3 2.8 ROADSTER
Z3 Z3 2.8 COUPE
Z3 Z3 3.0i COUPE
Z3 Z3 3.0i ROADSTER
Z3 Z3 M ROADSTER
Z3 Z3 M COUPE

It seems to me that as BMW uses a mount similar to what was used in the past on a new model, they change the part number so that the new part is back-dated to be used on the older chassis, as can be seen with the adoption of the same part for the e-85/e-86.

James

[shwah]

If it really is a superceded part by BMW, and you want to run it - just follow the directions pointed out by Greg and get it added to your spec line. Then there is no grey area.