My top 10 325i track toy build questions.

Just found my next car and will soon be picking it up. Its a 94 325 with a 5 speed and bench racing/planning is in full swing. I have looked around for answers and have only found a few.... here is what I want to know.

1) Car has a winter package which I am told has an LSD rear. Is this a clutch or gear LSD?

2) How can I find out the rears ratio?

3) Best way to plug an E36 sunroof hole?

4) Where can one find a non sunroof headliner?

5) Options to gut doors for weight? Are there manual roll up door cards and mechanical bits to dump the electric motors?

6) Options for cutting tons of weight while not leaving the car a full on race shell? I recall seeing a few threads on serious weight trimming but can't find them now.

7) Basic brake upgrades for track? Top drawer brake options? (after general maint of course).

8) Chassis upgrades? I am eying the TMS chassis reinforcement kit but am a bit unclear as to what bits I should source from the M3 or aftermarket in order to get the most out of the chassis as possible.

9) Cooling state of the art? I know early water pumps had issues but what about the radiator? Who is making the choice options as this car will at some point be cooling an LSx and not a S6.

10) What am I not thinking about that I should be? Obvious things I need to know not on the list above?

dsycks wrote: 1) Car has a winter package which I am told has an LSD rear. Is this a clutch or gear LSD?

Clutch

2) How can I find out the rears ratio?

There is a tag on the diff with ratio. S letter code equals LSD.

3) Best way to plug an E36 sunroof hole?

I used .044 aluminum and a bead roller. Its ugly but it weighs less than $250 w/ of CF and costs about $11.

4) Where can one find a non sunroof headliner?

No idea. Headliners are for street cars. Paint works.

5) Options to gut doors for weight? Are there manual roll up door cards and mechanical bits to dump the electric motors?

The mechanical bits weigh more due to big metal gears. If you want to save the weight gut it all and make lexan that fits into the door frame tracks. It will slide up/down and you can put a hitch pin thru the door to hold it up when you are parking outside.

6) Options for cutting tons of weight while not leaving the car a full on race shell? I recall seeing a few threads on serious weight trimming but can't find them now.

Other than the usual (seats, etc) you gotta commit to gutting everything to get real results.

7) Basic brake upgrades for track? Top drawer brake options? (after general maint of course).

M3 parts bot right up. Top shelf there are lots of options from $800 for Wilwoods to $6k for AP. M3 bits are a great start.

8) Chassis upgrades? I am eying the TMS chassis reinforcement kit but am a bit unclear as to what bits I should source from the M3 or aftermarket in order to get the most out of the chassis as possible.

A cage. Rear sways need a reinforcement for any track work at all. Subframe bushings - if they wear and are tracked heavily they will crack the sheetmetal they bolt to. Drop subframe, weld M3 reinforcement plates, upgrade bushings.

9) Cooling state of the art? I know early water pumps had issues but what about the radiator? Who is making the choice options as this car will at some point be cooling an LSx and not a S6.

speedwaymotors.com... search chevy radiator. Buy an aluminum one 26.5" wide or less and make it fit.

Stewart Warner water pump.

Bypass heater core (remove it, saves 40lbs), and remove all the water routing to the back of the engine.

Add an oil cooler

10) What am I not thinking about that I should be? Obvious things I need to know not on the list above?

Drop the oil pan... weld the oil pump nut, and baffle the pan.

Add a secondary fuel pump to keep from starving in hard corners on slicks.

Stiffen the motor and trans mounts to keep from breaking your fan and to help vagueness in the shifter under load.

Remove the factory fan, the factory aux fan, AC parts, compressor, pulley, etc and add a good quality electric where the AC condenser used to be. Saves weight, rotational mass and makes the front of the engine accessible.

Gut your bumper shocks and replace with aluminum tube.

1. if it has a LSD it'll be a clutch type, just check by jacking up the rear and spinning one side, other side should spin same way.

2. there should be a diff tag on one of the bolts unless someone threw it away. if it says say 'S346' then its' a LSD with a 3.46 gear, without the 'S' is open.

3. ive seen this carbon fiber panelbefore. for the challenge car i just skinned the stock sunroof, bent the edges out to touch hte hole's frame and tack welded around the whole thing, then seam sealed it. it isnt super pretty but works great.

4. dealer might not be awful for a headliner, never looked though.

8. if you plan a torquey v8, r-comp rubber, and track days i'd definitely reinforce the rear subframe and get an M3 x-brace up front. the rear is a pretty big job to do, drop the whole rear subframe/suspension out of it and weld in plates where the mounts go. but its a lot easier when the mounting locations are in good shape than trying to reassemble a torn up mangled broken unibody.

9. i would think a good quality all aluminum radiator would be enough for either engine. what does vorshlag use for their lsx cars? if hoses can be made to work with either tahts probably a good place to start. otherwise a stock new radiator isnt a usually problem until it gets old, and itll be cheaper if the v8 alum radiator wouldnt work best with both.

edit-GPS beat me to a lot of that. absolutely on the rear swaybar reinforcement too

Good stuff guys! Thanks.

The car is enthusiast owned and seems as if he has paid attention to the right details thus far. He bought it to track but never did and wants to get a 911 so he is adopting out some toys.

Right now I am just trying to get my mental game plan together as to make sure I hit things in a logical way so I don't miss something vital or end up forced to spend money for something more than once.

Focus is on solidity, hard sure stops and tight control without worry about adding power for some time.

One thing I am wondering is about a cage. We may well be gutting the car anyway so it seems the right time to do a all bushings and reinforcement as well. May even get trick Opera S2000 JDM style with light weight stiffness. Time will tell.

FWIW I think stock m3 brakes would be more than adequate, especialyl considering your car will be lighter. Also I believe the main things you'd want to reinforce are the subframe mounts, r swaybar mounts, front shock towers with the plate things, and possibly the RTAB pockets if you're going to be using stiff bushings all around. The OEM reinforcements should be cheap from BMW. But seriously don't forget the front strut tower reinforcements, without them you can mushroom the towers, it's actually fairly common.

Also look at e21 transmission mounts, they're stiffer than the stock m3 ones and really cheap from BMW.

Luckily the m50 you have is a pretty good motor, it just doesn't rev very high. You can probably get 200whp out of it but it won't have nearly the midrange power an s50 or s52 will. For a track car that shouldn't matter though.

I don't think you can get a non-sunroof headliner from BMW. I would just take the whole thing out and seal the top with something, and not worry about the hole there. I got lucky and found an m3 without a sunroof though ;)

One more thing is the seats, you can save a lot of weight from just changing the seats and getting rid of the rear ones. it should be easy to get the car to ~2800lbs, lighter than that begins to cost money and/or make the car less streetable, which may or may not be a consideration.

Also if you get bigger brakes you'll need bigger wheels, kosei k1's are pretty light and inexpensive.

Here is how the doors should look when you are finished

...and the headliner... before the aluminum sheet I used the metal cover from the original roof and black caulk.

Homemade swaybar reinforcement:

Damn I miss that car.

Nice cage but my big wide country arse is not looking for anything that hard to crawl into or out of. Even less so when the car will see (I am sure) more street miles than track miles.

I think someone MUST offer sunroof free headliners as there are E36s without sunroofs. May have to look to BMW or someone but its gotta be around. I like the idea of trying to cut out as much bulk as possible and leave the car looking almost like a real car and not a dedicated track animal but those plans may change when I get excited and start gutting.

My Evo RS with its carpet and no padding and lightweight everything with no radio is my inspiration. 2500lbs is the goal but not sure that will be possible with even a minor cage in.

Anyone have thoughts for light manual seats that don't break the bank and are somewhat supportive?

I was pondering Kirkeys but I think the negatives with the wife will make it a no go.

dsycks wrote: Anyone have thoughts for light manual seats that don't break the bank and are somewhat supportive? I was pondering Kirkeys but I think the negatives with the wife will make it a no go.

Sparco Evos are nice and supportive as are the Momo Starts. Very, very light too. They do not recline (obviously). Since it sounds like you are looking more for a street car - you cannot go wrong with Recaro SRDs. Keep an eye out - sometimes I see a pair go for $500 in nice shape.

i'd look at some of the factory recaro type seats like the Evo, SRT4, redline, etc. people often change to race shells leaving these usually pretty comfy, reclining, some offer harness holes, and way cheaper than a pair of wife friendly aftermarket seats.

Pondering suspension. Had some friends that really dug the KW V3s for the Evo's and I guess I never bothered to wonder why. The way they deal with compression is to preset the high speed and let you monkey with the low speed which is oddly appealing to me.

I've been all itchy to go 3 way just to be able to get low speed bump adjustment and this may be a cheap way to scratch that itch.

Anyone know anyone rocking these coils on an E36?