Project Update for Dec 9, 2011: There's an ECR track day this Saturday (ECR Toy Run) and AJ and Ryan have been wrenching this week on both our 2001 BMW 330 and the 2011 Mustang, to take these two cars out for one last blast around the track for the year. The BMW hasn't been on track or autocrossed in over a year, but its been running around with its fresh 2005 motor for a couple of months and and we've finally found all of the clunks and bangs and repaired them (the ball joints in fairly new front control arms had already sh!t the bed! Lesson learned: don't buy cheap, no-name replacement parts).
Before we got started on the exhaust, I had AJ swap the race seats back in, then align, corner weigh and corner balance the Mustang. The weights were looking good - this was before the exhaust work lined out below. The weight above (3483) was with the trunk junk still installed; it was 3472 lbs with low fuel (autocross weight) and the junk out, so it is slowly getting lower. Not too terrible for this big pig - the car started out life at
3563 lbs w/o fuel, and we've seen over 3600 lbs stock, with some gas in the tank. The 18x10's and the 275/40/18 tires are a bit heavier than the normal 18x9/265 tires we run, so knock off another 40 pounds out for the "STX" autocross weight. And we're going to get some weight out of the exhaust, today...
The Mustang is getting a new, 304SS, 3" mandrel bent, "after-X" exhaust here at Vorshlag today. It has been running around with the ARH 1-7/8" primary full length headers, the ARH catted X-pipe, but the stock rear exhaust section from just after the X. The drive-by sound test numbers didn't go up at all with the headers, which meant the stock mufflers were choking the the exhaust noise and flow down considerably. The stock mufflers
looked heavy, too, and the over-axle section and resonators are "factory crushed" with crazy crimps and "clearance" bends. Its been bugging me for months, and we finally found time to attack the Mustang after our fabricator finished with
McCall's Z3M dual 3" exhaust (which is incredible). Did I mention that Vorshlag is offering custom mandrel bent exhaust fabrication now?
I was right about the Mustang's stock mufflers - they are 25 pounds each! The after-X exhaust section with mufflers was 75 pounds just by itself. Factory exhausts are ALWAYS crazy heavy, and restrictive, and too quiet.
We'll fix that!
While Ryan was TIG welding up the exhaust AJ was swapping to the dedicated set of track rotors and pads, plus giving the car a brake fluid flush.
This is the final routing, above. It gets within 2 inches of a fuel filler line so we wrapped that part of the exhaust with header wrap, just to be extra safe (there was zero issue with it after 2 drivers tracked it all day). To see how much weight the new dual 3" exhaust shed, we did a quick scale check as it came down - 3442 lbs. So it lost exactly 30 more pounds just in the rear exhaust. Most of that was in the mufflers, but some was in the larger diameter 16 gauge pipes, too.
After we got home that night, before we went out to grab some dinner in the Mustang, I shot a little video (below) of Amy in the Mustang starting it up, idling, and a little blip of the throttle. It sounds pretty subdued at idle and cruising around, but at WOT it is definitely "easier to hear the engine" now.
click for video of exhaust test
Next week we'll take the Mustang back to True Street and have it re-dyno tuned, and finally get the damned "street" tune, that takes out our weaker "autocross" throttle mapping. I will do another thread update after the dyno runs, with a report of how the track event went (Mustang was great!), what times it at ECR, etc.
Thanks,