Bill S,
Maybe I missed this earlier in the thread, but how do you measure your 60-130 runs?

 

The slope of the road makes a big difference. A car making a run on a 2% upslope versus a car making a run on a road with a 2% downslope would cause a big difference in times between the two cars.

Density altitude is computed using pressure altitude and temperature. On a cold day here in Atlanta the density altitude can be over a thousand feet lower. On a hot day it can be 2000' higher, a swing of over 3000', which would make a difference in times.

As for weight, every ~200 lbs makes ~ 0.1 sec. difference in quarter mile times, so that much might also be expected in a 60-130 run.

Combine these (one car on a 2% upslope on a hot day at 1000' MSL with a full tank of gas, versus another car on a 2% downslope on a cold day at sea level with an eighth of a tank of gas) and the the results could not be compared with any real results gained.

 

I have the AX22 GPS/accelerometer based performance meter and here's a recent graph I did while testing it in my Ruf'd GT2.



Sadly my hard-disk on my PC failed so I've lost the data, so cannot extract any performance times.

I will say that GPS or accelerometer is the only way to do it accurately, as I've seen Porsche speedos vary wildly in error.

Guy

 

No problem. Just report you test conditions. Unless way off, these variables will probably not vary the time by more than .5 seconds.

If your time is slower than you expect, just try again under better conditions and report the change. In any case, you're not going to get a time under 7 seconds unless you have a very fast car.

 

The time axis is very course. Does the GPS time get down to .1 seconds?

 

Run through all the gears to redline starting from a roll in first. Time when the speedo sweeps past 60 and 130. Publish a speedo/tach video with sound when possible to help analyze the results.

 

If you read the Race Technology Website it explains all (the 5 Hz GPS, the doppler effect interpolation and also the g-meter accelerometer overlay). The short answer is it gets down to 0.01 seconds.

Its accurate enough to be used by a few car manufacturers and some car magazines.

It also produces a full acceleration matrix ie from every 10mph increment to every other 10mph increment both accelerating and decelerating.

When I get a chance I'll use it again and post some more results.

Rgds

Guy

 

I think this deserves a TTT....just look what you started, Bill!

 

Sean look at the date of said thread 2004.........................

 

Yes Paul, I know....Bill S originated the idea (although some say it was Rennlist).

When are you going to dust off your Mangina and get Scott a time?

 

Great to see this old thread!
I only had an ECU job in those days. On a real cold night I got ~around a 9.2s measuring with an old G-Tech accelerometer. The G-techs were not very accurate because when the nose came up during hard accelleration the unit sensed more gs than were really present. The GPS measurers are certainly a vast improvement.

 

Ya, its interesting to see an old debate that resulted in something significant.

Its funny how everyone thought a mid 8 second car was unbelievably fast less than 5 years ago.

 

Thanks for BTTT, it was a good read.

 

Amazing evolution of TT mods and times over last years...

 

Yeah, I read 3 pages before I realized the date. Thought I was in the twilight zone...