TXGOLD, this is a two-shift run, right?

 

One shift, and it appears to be a granny one at that. I beleive the first blip on the speed axis is due to the elevation change shown directly below. For what its worth, this is a RWD stock K16 car. Incidentally, I was able to get a couple more 8.4s tonight.

How are you guys determining shifting time from these graphs?

Peter and Scott, thanks for the help and time.

 

TXGold

It is not likely that the slope caused this, there is a clear sudden loss of acceleration a little beyond the 90 mph mark where the speed curve flattens, the Gs drop a lot in parallell, just the same as during your next shift.

The granny shift looks like it is due to clutch slippage most likely. I am still amazed at how the tool is showing positive Gs while shifting, despite such slow shifts like this one...Beats physics.

So you are on a flash only and stock K16 (not hybrids) and got a 8.4s?

 

Affirmitive sir, they are stock k16s.

How are you asscertaining this is clutch slippage?

 

Pretty amazing.

I cannot ascertain based on a Jpeg, but it is my opinion since the long Gs are gradually going upwards after the shift....typically you get a high spike of long G right after you have released the clutch and are on full throttle, and it then subsides to the normal G levels. Sort of what you see on the zigzag line around the 90+mph level.

Clutch slippage might be a slow release of the clutch of course, not necessarily that the clutch is gone.

 

edited

 

How do ya'll determine shifting time from these graphs?

 

Ryan,

I just want to verify that that you have made NO other modifications to your car since the 9.26 1-shift run you made previously, other than converting to RWD. Is that correct?

I've been waiting a long time now for a before and after AWD to RWD run...and as long as you made no other mods...this seems to be exactly what I was looking for.

For those that are interested, TXGold 's previous best 60-130 with AWD and 1-shift was 9.26. He converted to RWD and went 8.40 with 1-shift. This is with the stock K16's.

 

Thats correct. Since the AWD run, the only change has been the RWD conversion.

 

Did you send both graphs to Kevin? Also what were the running conditions of both runs? And weight?

Just asking so we can eliminate the possiblilty of any other factors.

 

Can someone overlay both runs one on top of the other and post a snapshot to see differences in shifting times etc.. The time difference with only this mod looks too much. We have observed around 0.4 seconds difference between 2WD and 4WD, on the same exact car and shifting times, including the weight difference of the 4WD system (meaning including friction losses + 100lbs difference)

 

Ryan,

Do you still have the .dbn file for your 9.26 run that you can resend me so I can overlay the graphs? I believe KPG is the one that verified the 9.26 graph. He might have it if you don't.

I was able to find the .jpeg of the graph, however:

 

Scott, I emailed you the file...
Peter

 

Okay, here is the comparison graph.

The 9.26 run was on a decline of 0.06% over the course of the run (1,372 feet). The 8.40 run was on a decline of 0.65% (1,233 feet). Both well under 1% over the course of the run, so an insignificant difference there. Had he been drag racing himself, he would have been 9.5 cars ahead of his 9.26 run.

The shift time was .32 seconds for the 9.26 run, and the shift time for the 8.40 run was .23, for a difference of .09 seconds in favor of the 8.40 run.

The 9.26 run was made on 02 Feb 08: From weatherunderground.com, here are the weather conditions for 02 Feb '08 in Houston:

Avg Temp: 59.7 degrees
Avg humidity: 77%
Avg pressure: 30.04 inches

From the same website, here are the conditions for Houston yesterday, 18 April '08:

Avg Temp: 67.1 degrees
Avg humidity: 65%
Avg pressure: 29.95 inches

Slightly better conditions on 02 Feb (higher pressure, lower temp...but with a bit more humidity).

 

I'm going to post this on the NASA forums. They seem to think that AWD is worth a 50 hp penalty vs RWD (a penalty of .5 which is almost as much as adding non DOT slicks)

I'm having to consider removing it so I will have a real shot against the 2900 lb (w/ driver) Z06's.