Time attack beetle

[Humble]

I think I'll keep a close eye on the wing with a rear facing camera for the first few runs and watch for deflection. If it's too bad I'll pull it off and wrap it in carbon which should stiffen it up. I also want to change the end plates and make them longer vertically which should make the wing more effective at speed.

The lower coilover spacers are the racers edge pieces, expensive but worth it. There's about a 1/4" (8-10mm) of clearance on the trailing arm and I ran It from full droop to full compression and the spring never gets close enough to worry about.

The QA1 can be run inverted without issue according to the tech I spoke to however the adjustment knobs are a bit harder to reach behind the big wheels. I thought they were only rebound adjustable like most other single adjustable shocks but apparently they adjust rebound and compression together. The model # is DR4855B for the promastar single adjustables.

The springs are 2.5" (about 65mm) in diameter, and set for maximum ride height right now, which gives me no room to increase spring pressure at a rear corner if I needed. Right now I've got 2" of droop and 2" of compression which is about perfect, but I'll probably be increasing the spring rates quite a bit. I'll probably switch to a 9" spring for more tuning room and move up to a 450# spring for the rear and a 350# spring for the front for a new race setup.

I found a quick (rough) spring calculation from a rally group to get spring rates. First, find your corner weights, for me it's 435# in front and 610# in rear (just the heavy side right now). Now multiply that by the max g-force the car will see, typically 2.5g's in road racing, so that's 1088# and 1525#. The bug isn't so light at 2.5g's Now take that heavy number and divide it by your suspension travel, in my case 4" front and rear so that's now 272#/in. in front and 381#/in. in the rear that are needed to take up that kind of weight in the corners. Not done yet though, that gives you spring rate but you need to find the effective wheel rate to make this work right. For 944's it's 90% in front and 60% in rear. What that means is if you compress the rear trailing arm 1" the spring will only compress .6" so you need a stiffer spring to make up the difference. So you multiply your front spring rate by 1.1 and the rear spring rate by 1.4 which gives you 299#/in. in front and 533#/in. in rear.

All this calculation is based on my last weigh in but none of these values are current. Since I last weighed in I moved the gas tank, gutted the car, moved the battery, and added more weight to the rear with the oil system and turbo kit. I'll re weigh the car once everything is sorted and order new springs then.

[Sandeep]

Thanks for the confirmation on the upside down mounting of the QA1 coilover. I have the HAL-DR5855P model and found out that they fit a stock steel trailing arm much better upside down, with no rubbing anywhere of the spring and adjusting mechanism. The adjusting knob is, of course, at the top of the rear shock tower now.

Sandeep

[Humble]

Still sorting little problems with the car trying to work the bugs out. Took the maiden drive though, nothing special, but kind of frustrating. I hadn't quite set the shifter right and I left the wrench at home, so I couldn't get the car into 1st to climb our 7% grade driveway. I got it into first and up the hill eventually but it took a while.

A new item on the short list, a leaking MC. The plastic fitting on top is cracked and leaking so I need to find a new one. I also need to sort out the turn signals. Left side works fine but the right side makes all four corners blink. I'm on the fence about the pro synchro rings in the tranny. You really have to punch it into gear, even at low speeds, to shift otherwise it grinds. I need to see how they behave at full speed.

Finally got the fuel sender dialed in right, now full is full and empty is not full. While I was working on the tank, I checked the breather and I think I'm going to route it down out of the trunk areato reduce the underhood fumes.

Other than that I'm going to be scheduling dyno time on monday and well see what this baby can really do!

[Wally]

Originally Posted by Humble

Other than that I'm going to be scheduling dyno time on monday and well see what this baby can really do!

Cool, you feel the rings have settled already (by) then?

[Humble]

We're going to break the motor in on the dyno, change the oil, then go for a top tune on boost, then add water injection and timing. Aiming for 350+ but I'll be happy with anything more than 300.

[Humble]

Dyno day is set for next Wednesday the 27th! My predictions are 350hp and 310 lb/ft torque @ 20+ psi. Well see if any of that pans out or not. I took a little trip around our neighborhood yesterday trying to nail down a streetable tune and the car is beyond loud. My roommate described it as the evil offspring of a harley and a 747. I've already ordered a muffler and piping which should show up late this week or early next week. With luck this will keep me below the 92db track limit if not I got a supertrapp tailpipe insert just in case. The power, oh the power. I got just a taste until the motor cut out at 4k, no real boost even, and I can tell hell is just waiting to break loose.

I was able to fix the leaking brake line as well, it was the low pressure line but now there's air in the system so I'll need to bleed the brakes again. Also re-routed the fuel tank breather which seemed to help the gas fume smell in the cabin.

Now I'm counting the days, hours even...

[Wally]

350 hp would be extremely well done! fingers crossed.
Could not find what turbo you had bought for it?