Vorshlag BMW E46 M3 CSL - V8 Downforce Monster Track Car ("Chainsaw Massacre")

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The upper curved section of the flare was cut from steel made from transfers from the cardboard templates. These sections were then rolled and reformed in the English Wheel (above left) and the edges that meet the wheel arch were rolled in the bead roller (above right) and formed further in the shrinker stretcher (not shown).



These horizontal flare sections were fitted to the framework of the flare and fender but went back into the English Wheel a few times to be fitted.



Initially these horizontal sections were made from one piece of sheet - which was a very long, multi-curved panel. These were later were re-made in 3 pieces, to get a better curved fit. The rear section was templated with blue tape (see above left) and you can see the seams in the top/middle and at the rear third (see above right).



To create a gap at the door opening there was a "flat" section that was welded to the middle of the curve on the front flare. Finally a vertical panel tied that "flat" upper section section into the rear landing pad. This vertical panel has a curve that mimics the stock fender shape, just moved outward five inches. The total flare width at the curve is 8.25" - its pretty massive.



You can see the large vent opening at the rear of this panel which will be used to evacuate the wheel well. There are all sorts of curved and formed edges on this panel to give it strength, cleaner airflow and better looks.
The look we were going for was sort of a modified/curvier DTM flare. The entire structure shown above is attached to the fender, which can be removed as a unit.



The 3 layers of now cut-apart steel for the rear fender structure were hammered into place, cleared of paint and undercoating, then carefully stitch welded together via a MIG. There's no way to get to all of the factory coating on the inside sections of the sheet metal but a MIG can power through this stuff better than a TIG. Once both rear fenders were cut and welded, the areas were primed with self etching primer (needs to have "zinc" somewhere in the name) and the car was reset at ride height. It looks ugly but THAT is what needs to be done under any unibody car BEFORE you start a proper rear flare job.

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BUILDING CUSTOM STEEL FLARES - REAR

The rear flare fabrication follows the same process as the front, starting with the front and rear "landing pads" then the formed outer arch framework.



The curved horizontal flare sections were made from multiple pieces this time to keep the curves following the bodylines better.



Ryan finished up the rear flare and they looked great - from the side (see above right). But from the rear there was something odd about the rear vent opening. There was an attempt to widen the rear fender to follow the rear taillight shape. It just... didn't look right.



Several of us stood around the rear flare one afternoon and we drew some lines in sharpie as well as blue tape. We all weighed in and together came up with a new shape.



Above shows version 2 of the rear flare. The boxy rear section was scrapped in favor of a tear drop shape to the added vertical section, which blends into the fender at the tail light. Some curved air deflectors were also mocked up in cardboard.



Once again everything shown attaches to the rear fender. There will be additional portions that tie the rear bumper cover into this flare on the back side as well as a skirt that ties into the lower front section of the rear flare - as well as the trailing lower edge of the front flare.



Everyone was happier with the look of this version so the other side was begun. With a final design locked down the second side was slightly easier to duplicate in a mirror image, pulling templates from the right side pieces to make the left side flares.



I'm happy with the look, Jason likes the airflow shapes, and Ryan likes the tire clearance - and the customer likes it all. Again, we obviously have some missing sections to tie into the flares sections at the front, middle and back, but the "wheel flares" are complete and ready for final welding then track testing before bodywork and paint.

CUSTOM FUEL CELL + OIL TANK + ENCLOSURES

The images below may look pretty mundane but there was a lot of thought, planning, and custom fabrication that went into these items and enclosures.



Let's break it down into sub-sections, starting with the fuel cell decision.

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WHY USE A FUEL CELL?

The stock fuel tank in the BMW E46 has both good and bad properties. Good: it is strong, compact, mounted very low in the chassis, just aft of the front seats. Under the rear seats, under sheet metal, completely sealed away from the cabin. It crashes well being in the rear middle of the car, too.



On the bad side the saddle shape makes for nasty fuel slosh in lateral loading and the "tunnel" between the two sides is too tight to fit dual 3" exhaust pipes and still keep good ground clearance. It is also plastic which means in a fire it can melt, rupture, etc. That isn't super common in crashes, but it is a possibility. Also, one side of the E46 saddle tank is much smaller than the other, as you can see above left. It is cheap and easy to just re-use this tank - which is what I did on my personal E46 330 race car.

In use a fuel cell provides a minimal anti-slosh effect due to the foam that is inside the bladder but can be designed to always pick up fuel. A fuel cell bladder is VERY tough and made to hold up very well in a motorsports crash. The bladder is mounted inside of a can that is made of steel or aluminum, with one end (usually the top) that can be unbolted, to extract the bladder for service. The bladder has to be replaced every 5 years to maintain FIA certification, so keep that in mind. The fuel cell foam can also degrade, especially when exposed to (and soaked /stored with) ethanol.



For many decades an FIA approved fuel cell was required for many road racing and hill climb (like the Pikes Peak Subaru STi above) classes, but safety improvements in modern OEM plastic fuel tanks - and their common, optimized placement under the car behind the front seats - has allowed these to be permitted in many Wheel-2-Wheel racing classes. We are building this E46 M3 for NASA Time Trial and Optima competition, so a fuel cell was not required, but it is never a bad idea. They do tend to be safer than almost any OEM fuel tank.

We talked about a custom fuel cell early on. Trunk mounting is the easiest and probably smartest move. There are many rectangular shaped fuel cells with an aluminum enclosure and kevlar bladder, like the ATL below in the 69 Camaro track build. This is mounted behind the axle just forward of the rear bumper.



I usually forego this in my own cars because I don't do wheel-to-wheel racing, but for serious builds a fuel cell is pretty standard. If packaging had permitted, we would have used an off-the-shelf fuel cell / shape and stuck it in the trunk. If possible, try to use an off-the-shelf cell. You will save mountains of packaging hassles and costs by sticking with common fuel cell shapes.



This car, being built for Optima competition, needed to be more optimized. Visible "race car" things (like a trunk mounted fuel cell) can sometimes spook the D&E judges. Besides, having a big chunk of weight in the form of 16-20 gallons of fuel mounted way out back makes for some weird polar moment issues.

MAKING A CUSTOM FUEL CELL CAN

Pretty early in this project we decided to make a custom fuel cell, to gain the exhaust clearance room in the tunnel, add safety, and keep the fuel load as low and centrally/rear located as possible. Putting it in/under the back seat would also leave the trunk floor area open for a diffuser - another really useful addition to get additional downforce in an Optima car (rear wings are severely limited in that series).



This custom cell was modeled somewhat around the lower shape of the right/passenger side of the OEM saddle tank, just made significantly taller. It actually holds 16 gallons all on the one side, which equals the OEM dual saddle tank's volume. We figured it would be easier to do a couple of sessions in a row on track feeding a hungry 800 hp engine if we had a full 16 gallons on board. Ryan made the "can" out of aluminum plate that was TIG welded together, with a flange on the top to be able to access the bladder inside.



The shape of the can is funky - not rectangular - and this will cost us later when we have a custom bladder is built, but the alternative is a compromise of one sort or another. Of course there is a hole in the rear seat floor to let the taller portion poke through - to get the fuel volume we needed. This hole will need to be sealed up from the cabin, and an enclosure around the fuel cell can will be needed as a firewall. That work is shown below in another sub-section.



The fuel cell can is 15" tall and sits about 5" above the rear seat floorpan, but sits no lower under the car than the OEM saddle tank. The fuel cell can is mounted inside of a mounting structure or "cage" made of 1" square steel tubing. The upper portion can be unbolted to remove the can.

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The entire "cage" bolts into the rear seat area - and also holds the dry sump settling tank, which I will talk about below.

DRY SUMP TANK MOUNTING

Running a dry sump oiling system is a really REALLY good idea on a car like this that has massive race tires (13.8" wide), lots of downforce, and a built race engine. And any dry sump oiling system needs an oil settling tank / reservoir.



There are two schools of thought on oil tank placement with a dry oiling system: the engine builder wants it up front RIGHT next to the engine, with minimal plumbing runs. Mounting it under the hood at the firewall is common. The chassis engineer wants this 10-14 quart oil tank at the opposite end of the chassis than the motor, to keep improve rearward weight bias. This "trunk mounting" option is somewhat less common, but it is done.



On this car we split the difference, mounting the oil tank opposite of the fuel cell, sitting behind the driver. It also pokes down through the rear seat floor, to keep the weight as low in the chassis as possible.



The shape of a dry sump tank is also important. The taller the tank the more distance the settling oil has to travel and hopefully the more baffles it can pass through to remove entrapped air. The oil that hits spinning engine parts can get whipped up like a milk shake and turn into foam. Foam doesn't "pump" well and lubricates even worse. The longer the oil has to travel inside the settling tank, the more air gets removed and the more "liquid" it becomes. So a tall/skinny tank is more advantageous than a short/fat tank. But all sorts of sizes are available to help builders package the oil tank in their application.



The tank that fed the 7.0L LS7 engine in the the factory equipped dry sump C6 Z06 was tall and skinny. One major change happened from 2007 through 2013 model run of this car was - to make the tank larger in volume, going from 6 quarts up to 9 quarts (bringing total oil capacity of engine + tank + cooler from 8 to 11 quarts). There are even larger capacity oil tank units for this OEM LS7 application from the aftermarket.



We chose an ARE tank (p/n 7025A) which has a 25.5" height and 6" diameter. This holds 2.5 gallons of oil (10 quarts) and is the "Tall and Skinny" option. These are more of a chore to package inside of a race car. We also ordered the ARE tank mount (p/n 7000) to hold the tank, which was mounted to the 1" tubular structure mounted in the back seat.



As you can see it sits pretty high in the chassis but its 25.5" tall. It sticks down under the rear seat floor (through a hole) as far down as we could comfortably put it, too.



This hole of course has to be covered, but a fire proof aluminum enclosure will handle that.

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MOUNTING "CAGE" FOR FUEL AND OIL TANKS

A mounting structure was built with 1" square tubing to hold the fuel cell can and dry sump tank. On top of this are the "firewall" panels that seal the passenger compartment from these hot/flammable fluids as well as the underside of the car.



The structure started out as a perimeter section of tubing and eventually lower sections were added for the fuel cell can. Then the bolt-on upper section for the can, too.



After that the bracket to hold the ARE billet oil tank mount was formed from steel sheet, with some dimple die holes to add stiffness and remove weight.

ENCLOSURE TO COVER OIL TANK AND FUEL CELL

Now that the tank/cell mounting cage was bolted into the car the openings through the trunk floor needed to be sealed. There also needed to be metal coverings for the dry sump tank and fuel cell as well, to keep fluids and fire away from the cabin.



First the enclosure for the top of the fuel cell was built from more aluminum sheet.



These were cut using cardboard templates, then taped together and trimmed, tack welded and final TIG welded. This "can" mounts inside the 1" steel tubing structure.



But wait, there's more! A giant 3-piece enclosure was needed for the oil tank side. The enclosure was too tall and unwieldy to be made from 1 piece, so it's 3 pieces.



We need to make an easy to access hatch to check the oil tank levels (dipstick) and there's still a flat panel that needs to go between the two upper enclosures but for the most part it is done. They aren't exactly "pretty" to look at but they are very functional and necessary. We might add a shrubbery or something to distract the D&E judges...

LEXAN SIDE AND REAR WINDOWS + FUEL FILL

To lower weight we added Lexan rear quarter windows and back windows. Then we added a fuel filler neck in one of these windows, and an enclosure around the filler neck.



We sourced the rear quarter and back windows from Five Star, a race car supplier. These were mocked up on the car above to check for fit, which was very good.

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LEXAN SIDE REAR WINDOWS

One thing I didn't get this time were the weights on the glass rear window or side windows vs the Lexan bits. I did get the weights on the HARD Motorsport and OEM E46 rear side rear windows in this July post on the E46 330 TTD car, which I copied below. The Five Star bits weigh almost exactly the same but the HM bits are much easier to mount (with their optional install kit) and come with a black outline vinyl border pre-applied to the inside.



The side windows were installed first. Like most race car parts these come with no instructions - you're expected to know what you are doing.



Ryan began by marking the outer perimeter with two lines that corresponded to part of the "black border" that would be added later as well as a centerline for drilled holes. These were marked using a compass and a Sharpie, which you can see below at left. The outer protective film was left in place as to not mark up the actual Lexan plastic.



None of the factory mounting hardware was re-used. Holes were drilled equally around the perimeter of the glass that would land in the sheet metal surround of the window. Then the holes in the windows were transferred to the body and those were center punched and drilled.



M5 nutserts were installed into the sheet metal surround for each window then countersunk stainless Tinnerman washer and countersunk stainless bolts secured the window in place. This makes for flush mount, corrosion free hardware. The factory black drip rail trim was then reinstalled.

LEXAN REAR WINDOW INSTALLATION



The rear window installation followed the same techniques: marked and drilled Lexan, transferred holes and drilled sheet metal, added M5 nutserts, then Tinnerman washers and countersunk M5 bolts.



Many of you readers have seen us install and use these threaded inserts or "nutserts" on many projects. We tend to use metric splined steel nutserts in M4, M5, M6 and M8 sizes, like the one shown above left. These add a threaded hole to sheet metal that is "blind" or hard to access on the backside. There are also versions for use in plastic or fiberglass panels as well. If you can work a blind rivet gun you can work a nutsert installation tool (above right).



This is how they are installed... you drill the appropriate hole (there's a chart), install the nutsert you want with the correct "grip length" (there are longer nutserts for thicker panels), then use the tool to squeeze the insert and expand the back side behind the panel. Now you have a threaded insert that is secured in place. Sure, you could install welded inserts, but that's a lot more work. We tend to use those on thicker metal, if we cannot drill/tap it for some reason, or if we need a much longer threaded length or more strength than the nutsert can support.



Like Ryan did on the same exact brand of rear window on my E46 330, we will go back and tape off then spray paint the border on both the side and rear window on this E46 M3 at a later date. This makes the windows look a lot less "race car" and hides the visible sheet metal underneath.

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We will be blowing the car apart for paint after the first track test, so we will likely add the painted borders (and some RTV sealant) to these windows then. For now they were secured in place with bolts only.

FUEL FILLER NECK

At this step we show the plumbing from fuel filler cap on the right rear window to the fuel cell, which had an ATL sourced top fill panel. This is shown with the partial aluminum enclosure around the aluminum fuel cell can in the picture below.



Because of the unusual back seat fuel cell location the filler neck was added to the right rear window. A simple fuel filler neck and cap were sourced from ATL and added as shown below.



Ryan took some aluminum tubing and welded a mandrel bend at the top to line up the filler tube to the cap in the window. A short piece of flexible tubing was added at the bottom but this is only silicone and will be changed out for a fuel safe flexible hose soon.



To make this filler neck fire safe the entire fuel fill section was then wrapped within a metal enclosure.



This is what it takes to put a fuel cell in the back seat - lots of fabrication work. An upper section to the fuel cell enclosure was built to tie into the fuel filler neck enclosure tube-within-a-tube. Ample room in the top enclosure was added to allow for plumbing AN lines from the fuel cell to the fuel pump and engine and back, all of which will run under the car.



All of this can be unbolted in sections for service, but most importantly fuel can be easily added outside of the car and end up in the fuel cell - with fire safe enclosures around everything. That wraps up the fuel cell can, filler neck, and enclosure. We still need a fuel cell bladder, which we have been trying to get quoted for many weeks.

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