: Bonneville GXP 1/4 mile times

02-02-09, 06:25 PM
Iíve only had my GXP to the track one time, back in September 07. I posted this up on a Bonneville site at the time, but thought I would post it over here as well. The runs were made at Thunder Valley raceway in Noble, OK.

At the time, my car had a partially gutted airbox. Since then, Iíve fully gutted the airbox including a bigger inlet, and cleaned up the throttle body entrance with a die grinder. Traction was not very good that night, as evidenced by my 60-foot times. Not really sure what my car weighs, but I would assume its at least 300lbs lighter than a Caddy.

Temp was a steady 67 degrees the entire evening per my Climate control display. It seemed to be fairly humid. There was no significant wind that I noticed.

I run 93 octane in this car exclusively. I had about ĺ of a tank of gas before I left for the track, and I added about 3/4 of a gallon of tolulene. That might not be beneficial for an N/A car, but I thought it might give me an edge. I did several WOT pulls in town and on the highway thinking that the PCM might respond with more timing to go with the slightly better fuel. By the time I got to the track, I had just over ľ tank. Now I realize that with a stock PCM, higher octane is not going to help.

Pass#1: For the first pass, I had a bin of tools and misc junk, plus a small cooler in the trunk. I stomped it off the line thinking it would hook because of all the rubber on the starting line, but it spun about Ĺ way through first gear; here are the results:

60' 2.405
1/8 ET 9.832
1/8 mph 74.12
1000' 12.676
ET 15.098
MPH 91.65

I was disappointed, but knew I could do way better. The car felt like it lacked power for some reason.

Pass#2: I decided Iíd go ahead and get everything out of the trunk and hope nobody ripped me off. Rough guess for the stuff I took out 30 lbs or so. I did a better burnout this time. Instead of stomping it I floored it a bit more slowly and was rewarded with much less wheelspin:

60' 2.29
1/8 ET 9.633
1/8 mph 75.44
1000' 12.439
ET 14.831
MPH 94.27

What a relief! I came to run a 14 Ė mission accomplished, now I could relax and see if I could do better. The increase in mph was a pleasant surprise although taking out 30 lbs does not explain it.

Pass#3: Removed Passenger headlamp:

60' 2.286
1/8 ET 9.57
1/8 mph 76.01
1000' 12.358
ET 14.732
MPH 94.95

Pass#4: Removed jack and spare, hit compressor button to pump up the shocks (and turned it off before the pass):

60' 2.273
1/8 ET 9.512
1/8 mph 76.43
1000' 12.283
ET 14.643
MPH 95.54

Yeah! Solidly into the 14.60s

Pass#5: No more changes. I launched it fairly easy, but still got some wheelspin just off the line.

60' 2.301
1/8 ET 9.485
1/8 mph 76.48
1000' 12.253
ET 14.609
MPH 94.31

Sweet Ė I picked up on the ET a little more! However something went wrong on the mph for this pass. If you compare it to the previous pass, itís obvious it fell off at the end somehow. I had less than ľ tank at this point, so maybe it was that, the fact that I hot-lapped it, or maybe I just didnít keep my foot in it long enoughÖwho knows.

I expect to run 14.40 next time out, I would like to make it back out sometime this spring.

02-02-09, 06:38 PM
good times. try torco next time, my buddy with a twin turbo ls1 puts one in every fill up. its not his daily driver so he only fills up about every 2 weeks

02-02-09, 07:06 PM
the bonneville gxp has a curb weight of 3,790 lbs. my 93 sts has a curb weight 3,870 lbs. nice times..i'd like to take my sts out sometime and see what trap times would be. i need good performance tires though.. i have excellent all season passenger tireson it right now..which is good cause its winter! did you power brake it to minimize wheelspin?

02-02-09, 10:04 PM
I was running the original Goodyear GAs, I have since put on some BFGs that do hook a little better, at least on the street. I was just loading the engine slightly on the brakes (guessing like 1200 rpm but didn't really pay attention), then on green I'd release the brake and give it x amount of throttle. As long as I didn't break the tires loose too bad, the car would take full throttle about 2 car lengths from the starting line. Maybe next time I will try loading it up a bit more and see if that helps.

Not sure if the gutted airbox helped, but the stocker had an internal tube that was 2 5/8" id, so I thought it would help to gut it.

02-11-09, 12:59 PM
Your decreasing ET and increasing MPH is what I have seen when drag racing at night. As the sun goes down and atmospheric conditions change, I usually see see between 3-5 tenths difference from a 6:00pm pass, compared to a 10:00pm pass. This is without changes in my setup(low 15/high 14 second truck).

I will have to get the STS to the drags. I would guess low 15's.

Nice runs.