Anatomy of a 1.271 60 foot

A

Alky V6

Let's go racing, boyz!
Joined
Jul 29, 2001
I stumbled across a new best 60' over the weekend. I thought I'd do a detailed dissection of the event to see what kind of tune my car needed at the launch to accomplish this rare feat.
At first glance of the datalog it appeared that the rpm and boost was rather low right at the release of the transbrake. I thought it was interesting that this resulted in a best 60' for the car.
Detailed analysis coming up next.
 
HelloBozos said:
Don't forget the Doctors diagnostics of your Whiplash!!!
Click to expand...
Gary came up to tell me afterwards, "Dang, you're murdering the tires!" One of those kind of launches where the rubber is talking to everybody. Actually, I think Victor got a vid of one of the better lauches over this weekend of the car. Maybe he'll post it.

This last weekend I was dialing back the boost controller in an attempt to gain some consistent traction for a bracket racing event I had entered. It was the third testing pass that gave the 1.271 60'. I was a little taken aback. Here I was dialing the controller back to slow the car down and I get handed a new best 60'. WTB Rover?!
 
Tires are screwed to the rims correct? If not ,might be able to go lower,they can spin on the rims...8^)
 
Here is the datalog with the time marker set one frame before the speed sensor started to read movement.
 

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Maybe this would be easier to read at this size.
 

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Which background color do you think is best? I think it's the grey background.
 
I final stage (shallow), set transbrake, go WOT and the nitrous hits at 26.58 timeframe, 2836 rpm, 92.9 kPa MAP (no boost). Timing is retarded to 12 degrees BTDC.
In the above datalog views the cursor is at 28.08 timeframe, 5358 rpm, 148.2 kPa MAP (7 psi boost). The frame before driveshaft movement is first detected. So, the nitrous is activated 1.5 seconds before the car actually launches.
At the point where the car starts to move we have 28.14 timeframe, 5406 rpm, 151.4 kPa MAP (about 8 psi boost).
The nitrous is still on and won't shut off until we see 174-182 kPa MAP (about 11-12 psi boost). We are launching with boost and nitrous, AND IT FEELS LIKE IT!
Timeframe 28.54, the rpm has sharply ramped to 6,094 and 203.5 kPa MAP (15 psi boost) as the nitrous has just shut off and the timing has almost completely come back in. Timing at this point is 25.9 degrees BTDC.
 
The timeframe just before the 60' mark appears to be 29.34. 6,928 rpm and 273.4 kPa MAP (25.4 psi boost), 29.6 degrees BTDC. Coolant is at 90 C and MAT is at 41 C.
At this same timeframe, the boost has peaked and will begin to drop in preparation for the 1-2 shift.
On this day the track could not tolerate a lot of boost in 2nd gear and was a problem all day long. You can see a spike in driveshaft speed after the 1-2 shift had completed. Luckily, the tires did grab the track without me having to let off the throttle.

Total boost on this run after shifting into 3rd averaged 286 kPa MAP (about 27 psi boost). Total time at 27 psi boost through the run: 2.04 sec.
ET and mph were 5.663 and 123.915
 
Rear tire pressures were even at 8 3/4 psi in the staging lanes. MT 29.5x10.5-15W at the end of their lifespan.
It was a cold day and bottle pressure might have made it up to 850-900 psi by that time in the day (12:10pm). The third hit on a fresh bottle. I get five hits out of a 10 lb. bottle.
 
The low point in the dip in the MAP to accommodate the 1-2 shift was about 263 kPa MAP (about 24 psi boost).
 
Notice how at the end of the pull, when I get out of the throttle, the driveshaft speed drops from 128 to 113 in an instant. Does this mean the car was dealing with a certain percentage of tire slip throughout the whole pass? Interesting, isn't it. :rolleyes:
 
don this were you have to grab some of your friengs and video the car behind and to the side.the info is priceless and will help you make tune and suspension changes,congrats on your best 60ft.
 
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