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FENDER ROLLING THE E46 NON-M
Quick side note during the race coverage...
After the 1st and 2nd track sessions at this Club Trials event, Olof and Brad leapt on the 330 to try to remedy the rear tire rub. Track side fender rolling sucks - this should always be done in the shop! - but parts delays & C4 prep ruined our schedule on the E46 the week before. It was "do it here" to keep from ruining the day (and the tires) or "head home".
Normally this would have been done at the shop, with the car on the lift and better access to power tools. With decent skills you can do this job in about 3-4 hours for the rear fenders of an E46 and not crack the paint. The goal is to roll the square rear lips flat against the outer sheet metal, then to push the entire fender out for even more room. These pictures are from when I rolled the fenders on my blue 2001 330 back in 2009 to clear 265/35/18 tires on an 18x10" wheel - which is almost the same width as this 17x10" wheel and 245 Hoosier.
Before you can even start with the fender rolling tool itself you have to grind and cut a bunch of hard epoxy sealer out from the inner lip of the rear fenders. Three layers of sheet metal are joined here and BMW seals it all up with this thick yellow goop that turns to a concrete like consistency. At the track Brad and Olof had to painstakingly cut this stuff out with box cutters, knives and screwdrivers. In the shop it goes faster with cut off wheels and wire wheels on 90° die grinders. It still makes a total mess, even in the shop.
Once the goop is all cleared out the horizontal lip on the inner rear fenders can be heated up (a pair of 500 watt lights, heat lamps, or a friend with a heat gun), the paint softens up a bit, then you go to town with the fender roller. There are a lot of adjustments that need to be made to slowly roll roll roll that lip vertical. Pressure is applied to the bottom of the control arm to push the roller into the arc you want. And it takes more clearance than you think - we like to install the rear wheel and tire, remove the rear springs, and push the tire up all the way to the suspension bump limit of the rear shocks. Then still add a little more... if you can fit your hand in between the tire and the fender at Full Bump then it just might clear. Only hard track testing on the actual competition tire can tell you for sure!
On the front the procedure is much easier and you can usually roll the E46 fenders in under an hour. The sheet metal is only one layer think, as the fender is a simple stamped piece and not a multi-sheet thick part of the unibody. For just a bit more room I like using a plastic faced hammer on the inner lip then slowly work it up and flat to the outer face. I use a flat faced body dolly on the outside of the fender, wrapped in heavy leather to protect the paint. Of course the paint needs to be warmed up to prevent cracking, but you can never guarantee that. On this day, with Amy driving, she wasn't seeing any front tire rub so we left that end of the car alone.
OK, back to the Club Trials event. I was having all sorts of trouble on the Corvette, as we had moved from a 245mm R7 to a 345mm A6 Hoosier. This level of grip in no way worked with the rebuilt factory Bilsteins on this C4 and the rear was bouncing all over the place. Still, somehow this session 3 time in the video above was the quickest time of the day at the Club Trials with a 1:23.2.
This car was not TTC legal with the tires used during this test and would eventually be run in TT2
We both ran our cars in session 4, where I was gridded P1, but it started to rain before we went out. After a number of passes I got little bursts of clear track, and the rain wasn't much more than a sprinkle. I was gaining confidence in this janky Corvette tire test and taking corners faster, braking less and less for the high speed sweepers like Big Bend and Ricochet. Still, my times were 5+ seconds slower than I ran in the TT3 car 2 years earlier. Everyone was off the pace and both Club Trials and Club Racers alike commented on the lack of grip that day.
Amy was running 1:33s in the dry, but during the slightly wet session improved to a 1:32 lap time range, so her confidence was getting better. These times seemed nowhere near what I thought this BMW was capable of on these tires. Granted, it had a lot of body roll but damn that's 5 seconds off the TTD record of 01:27.515, set by a BRZ back in 2014. We didn't have a 2nd video camera for her car this weekend so I cannot see how she was driving. She had an AiM Solo lap timer in the car, though, so she had predicative lap timing at her disposal. She complained of a lot of traffic, but we all saw heavy traffic this day.
Raw time results from session 3 (dry) and session 4 (wet). DangerZone was quickest of the day?
Ideally I would have driven one session in the 330 to get a feel for the setup myself and see if a "driver change" could improve our times. The weather was getting colder and a rain or snow storm was predicted to hit any minute, so I decided to let her get as much seat time as possible. After 4 sessions the rain and temps started to drop so we packed up the Corvette, swapped tires on the 330, and headed home. There's nothing more exhausting than spending a very cold day shivering in bitter wind chill conditions + driving in 4 sessions with a wonky setup (the Corvette).
CHANGES AFTER MSR-CRESSON
There was only one week between the MSR-Cresson event with SCCA and the season opening NASA race at MSR-Houston. Amy and I have both driven that track and we both needed to score points in our two TT cars to help start the 2016 season off right. We felt like the track side fender rolling the weekend before was probably sufficient and honestly our shop schedule got busy with customer work, so we tried to do as little as possible to both cars that week. I took the C4 for official dyno tests after the event and the 330 got a new set of springs.
The coilover spring rates we chose for this next segment of the suspension test were fairly conservative at 350 #/in front and 450 #/in rear. Compare that to the PSS rates of 156 #/in front and a progressive spring with an average of 265 #/in rates at the rear. To the front rate went up by a factor of 2.2 and the rear by a factor of 1.8... so nearly double the rates.
Normally with AST, MCS or Moton adjustable monotube coilovers for an E46 we would start with rates at 450F/550R, then jump to 500F/550R, and even 650F/750R rates for our 3 basic spring kit options. My blue 2001 330 coupe used 750#/in fronts and 900 #/in rears with a 285mm Hoosier R6, as shown above. It cornered much flatter even with a +40mm wider tire of similar compound.
Usually tire size and compound dictate how far up the spring rate ladder we climb, as well as intended use (dedicated race car vs street car, or somewhere in between). To convert these Bilsteins to regular 60mm coilover springs we swapped the OEM perches on the front camber plates to a pair of our 60mm upper perches. That converts from the goofy tapered spring that came with the PSS kit, which is made for the OEM E46 non-M upper strut mount and upper perch. Out back a pair of 60mm springs got our spring alignment cones, but we managed to keep the Bilstein ride height platforms that came in the PSS kit.
The only other changes made before the NASA race were adding some decals. Jon made some huge Vorshlag decals but only had time to install one side before we loaded up and headed to MSR-Houston on Friday.
Jon also added decals for some of the companies who parts we were using on this build like Forgestar, Bilstein, Mishimoto (more on that in my next update), and of course Hoosier (for potential tire contingency).
NASA AT MSR-HOUSTON (CW) JAN 23-24, 2016
We took both the Corvette and BMW to this 2016 NASA season opener event at MSR-Houston. We loaded up Friday morning and slogged through 6.5 hours of driving, most of which was burned inside the city limits of Houston dealing with their nightmarish traffic (normally this is a 4 hour drive from Dallas). I was towing the Corvette (which was being moved up to TT2 class) and Amy drove the BMW down, which she said was "bouncy" with the new springs. Hmm...
Of course when we arrived it was pitch dark and the paddock was packed. We got lucky and found a wedge shaped spot close to grid where we unhooked the trailer and parked the BMW. Amy raced over to tech and managed to get the car inspected for Annual TT Tech and a new Logbook.
The 330 also weighed 3434 with me in it after one TT session of four that I drove it over the weekend (I drove it in 2 TT sessions Saturday and 2 more on Sunday). That means this car is nearly 150 pounds overweight (class minimum for ths car is 3285 pounds). In TT letter class you don't have to bring a certified dyno sheet if you haven't touched the motor or done any power mods, which we have not on this car - yet. I suspect based on other E46 330s with this 3.0L M54 engine I've dyno'd, plus the dyno we did on the 2.5L engine in the 325Ci, this car probably makes around 180-190 whp.
Goal Power and Weight for this 330 in TTD:
3285 pounds / 13.45 ratio = 244.2 whp
Assuming the car dyno's on the high end at 190 whp, we're still pretty far away from the TTD class limit of 14.25:1 or our modified 13.45:1 ratio we can run at 3285 pounds with the 245 mm tire bonus (+0.8 bonus). So I figured we would be struggling on the straights at this event. And we were.
8.1.2 Minimum “Adjusted Weight/Power Ratios” for each Class
TT1 = 5.50:1
TT2 = 8.00:1 <- where the C4 should be
TT3 = 10.00:1
TTB = 10.50:1 <- closer to where the C4 is (11.1:1)
TTC = 12.00:1
TTD = 14.25:1 <- where the 330 should be
TTE = 16.50:1
TTF = 19.50:1 < - closer to where the 330 is (18.1:1)
- E46 330: 3434 actual weight / 190 whp guesstimate = 18.1:1 P-to-W
- C4 Corvette: 3188 actual weight / 288 whp = 11.1:1 P-to-W
In reality the power to weight ratio of our setup at 3434 pounds was closer to TTF than TTD, which explained why we couldn't keep up with some of the TTE prepped Miatas on straights at this event. We knew this car was under-prepped this time and were just trying to get some points during this season opening weekend for use later in the season (same could be said for the C4, which was closer to TTB's P-to-W than TT2 where we ran it).
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