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Unread 11-21-2013, 05:52 PM
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Default Re: Vorshlag BMW E36 LS1 "ST2 Build"

continued from above

Chassis Reinforcement and Prep

While the rear subframe was out being welded/reinforced/powder coated, and after the RTAB buckets and subframe mount reinforcement work was done, it was time to pretty up the rear of the chassis. The guys degreased, power washed, paint prepped, stitched welded a few areas and then painted the back of chassis in high gloss white. A lot of hours went into this step but the results were worth it.

Since we might cut out the spare tire well (one of the few parts of the floorpan legal to modify in Super Touring) I had the guys leave that section unpainted. And since we still have cage work to do in the middle of the chassis, they stopped the white paint forward of the RTAB buckets.

On the front of the tub the guys stripped and stitch welded a few more areas of concern, like places normally only held together by spot welds. After that the same power washing, degreasing and paint prep were followed by more gloss white paint. This is a paint product we've used before and it is tough stuff. It rolls on, not sprays on, and takes about 3 coats to really get perfect coverage. It is so nice working on a super clean white chassis like this, and the exterior will be spray painted a matching GM Gloss White as well. We will eventually paint the cage and interior with some more high gloss paint, too.

Cage Work Started

Since this will be built to ST2 rules, which is a wheel to wheel club racing class, it needs a full roll cage built using the specs within the NASA CCR. I'm not going to bore you with all of the possible roll cage tubing sizes we can use other than to say that since this car will be between 2500 and 2999 pounds we will use 1.75" diameter x .095" wall DOM tubing (see NASA CCR, 15.6.18 section).

Before we began the cage work the interior was stripped, of course. Strangely we didn't get pictures of any of this work. Tons of carpet, heavy foam insulation and wiring came out. Then the dash and HVAC bits. Not a single picture, which was puzzling. Anyway, even with all of the interior panels and carpet out there is still a lot of "sound deadening material" that is stuck to the floorpan in large areas. Kyle worked for a full day getting this stuff out, using two popular methods. The method shown above was taking dry ice and placing it on the thick insulation material.

In theory (internet theory, mind you), after you place dry ice on top, the black sound deadening material then gets very cold and brittle and you just "tap it with a hammer and it pops off". Well, that did not happen. This dry ice method is terrible and I would never recommend it to anyone, at least not with a BMW. We had much better luck with heat, namely using a heat gun to soften the adhesive then peeling the material off with a scraper. Of course when you do this the factory paint under the material gets scraped up a bit, so we cleaned then primed these areas to prevent rust during the next few weeks of work.

While our head fabricator Ryan was on vacation for a week and a half we took the stripped chassis over to Janco Fab and had Kurt bend up some of the .095" wall DOM tubing we brought. Kurt bent the main hoop and two front A-pillar bars above, which came out great. Janco does this type of cage bending work for a lot of shops in the area and we will continue to use him, because he is damned good. We had our friends at Titan Auto Glass come by and remove the windshield and rear glass, to make the cage fab work easier. Of course the windshield broke, but that happens a lot on original glass bonded to a chassis that has been installed for 22 years, like this was. At least the more costly rear glass was intact (although we might use Lexan back there and the rear quarter windows, depending on where the weight ends up.

Once the car was back from Janco the guys mocked up the bars he bent up and they began to work on the mounting plates that will be welded to the chassis. These load spreader plates will be made of .125" thick steel, which is thicker than the .080" minimum thickness (see NASA CCR, 15.6.14). Ryan here at our shop will build the rest of the cage structure and do all of the TIG and MIG welding.

This build will have a somewhat minimalist cage; one that meets the CCR and has a few optional tubes and gussets, and NASCAR style door bars on both sides, but nothing like the overdone cages I see "designed on the internet", with 20 optional tubes and X-braces on top of X-braces.

The pictures above show a cage built for us by Dallas Performance back in 2007, which was not made to be W2W legal, but was fine for Time Trial use with only a driver. This ST2 car's cage will have NASCAR style door bars (on both sides) instead of the X style door bar shown above, and we will add an FIA bar to support the front corner of the cage as well as several gussets. But for the most part it will be similar to that one, which was plenty strong, safe and fairly light. No bars "going nowhere", unsupported nodes, bars to the subframe mounts or the like.

What's Next?

We have plenty of work to tackle in November and December to make our first scheduled January 2014 race date. Here's next year's NASA schedule that we are trying to run in TT2, which just came out:

January 18-19............MSR Houston
February 15-16...........Barber Motorsports Park (MS, SE and NOLA regions)
March 8-9................MSR Cresson
April 25-27..............Texas World Speedway

June 21-22...............Hallett Motor Raceway
Aug 1-3..................Road Atlanta Nationals Practice
August 29-31.............NASA Eastern States Championship at Road Atlanta
Sept 20-21...............NOLA Motorsports Park (crossover w/ MS & NOLA)
October 11-12............Texas World Speedway
November 1-2.............Eagles Canyon Raceway

The dates in green above are the ones we will likely run in this LS1 BMW car. After about April 2014 we think the new 2015 "S550" Mustang chassis should be out and we will try to acquire and prepare one of those for the rest of the NASA races in 2014. Amy and I are signed up to run as a "team" for NASA in 2014 (Team Vorshlag), so we can share a car and only pay a single entry fee. It makes more sense than paying for 2 entries and sharing a car anyway - its not like we will get any less track time. When the Mustang arrives and is prepped, we can switch from this E36 to that, and say in TT2. That's the plan, at least...

A few other bits have been finalized. We just ordered a set of 275/35/18 Hoosier A6s for this car and the Forgestar 18x11" F14 wheels will be ordered soon. This 11" wide wheel will let us run as narrow as a 275 or as wide as a 315 tire. Of course there is a nice weight break at 275mm, so we will build around that primarily, but the flares will be built around the optional 315 tire, just in case. Its nice to have some flexibility down the road.

What will it weigh? Here's an idea...caged LS1 E36 without driver

Weight and power are the last things we will finalize. The power can be adjusted with a few parts changes (cam, intake, tune) so the final race weight will kind of end up being the driving force for that. We know what a similarly prepped E36 LS1 should weigh, because we've built them before. The E36 above had stock M3 brakes, a cage, all steel bodywork, all of the glass (except doors), heavy wheels and an LS1 + T56 and was 2508 pounds, with a single seat. In ST/TT classes you weigh with driver, and since I'm 200 pounds, that puts us near 2700 - soaking wet, without any significant weight savings plans (lighter wheels, brakes, bodywork, Lexan, etc). I don't see this ST2 chassis being much if any different... maybe 20 pounds more cage material, at most? Since the ST/TT "numbered classes" (see this page) are almost all "power to weight" based we can adjust the weight or power as needed to stay in ST2/TT2.

Essentially we are building towards an 8:1 pounds per horsepower ratio, which is the limit for ST2 and TT2 (TT3 is 9:1 or 9.5:1 if you have non stock aero, and TT1 is 5.5:1). There are several "modifiers" to this ratio, of course, and this car will use two of those. First, staying with a DOT tire that is 275mm or narrower gives us a modifier bonus of -0.4, so that would be 7.6:1. But then you have to look at your final race weight, and if we run it from 2651-2750 pounds (very likely) we would have to take a +0.25 ratio hit, which puts is at 7.85:1. So with a 2750 pound car in TT2/ST2 we would end up being able to run as much as 350 whp, which should be pretty easy to get to in a nearly stock 5.7L LS1 we have in store. A bone stock junkyard LS1 with our kit headers made 340 whp in a previous build, and the motor we are using is similar, but has been rebuilt by HKE.

That's all for this time. We should have more frequent updates over the next couple of months. Thanks for reading.
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