Ok, heres the scoop. I keep a detailed log of everytime I go down the track, that way I can recall any race. My best run was back in November of 2002. It was a cold day. Here is my time slip from the first race:

Reaction- .6256
60 Foot- 1.7792
1/8 ET- 8.221
1/8 MPH- 82.39
1/4 ET- 12.942
1/4 MPH- 104.60

I was running 18 Chrome wheels up front and Nitto 555R's @ 18 PSI in the rear. Stock Suspension, 275 RWHP-302 RWTQ

Now, I got rid of those wheels and went with Weld Draglights with skinnies up front and 26x10.5x15 ET Streets @12 PSI. I got rid of 102 Pounds, went to 290 RWHP and 332 RWTQ. I also added BMR LCA's, Relocating Brackets, and Boxed SFC's and still managed to lose 102 Pounds overall. I also added A TransGo Shift Kit, Drag Air bag @ 7.5 PSI and V6 Springs.

Here is a time slip on April 03:

Reaction- .7286
60 Foot- 1.786
1/8 ET- 8.3415
1/8 MPH- 81.86
1/4 ET- 13.1359
1/4 MPH- 102.97

It had rained earlier in the day and was a little on the hot side and a little humid. I did however run about this same time back in March with about 60 degree weather.

What gives? I was hoping with losing 100+ pounds I would gain a tenth. Gaining 15 RWHP another tenth and the added suspension another tenth. I was hoping going from 12.94xx's to constant 12.75-12.80xx's. I did run many times from 12.94 to 13.03 with my old set-up.
1. Im I running with too low of air pressure in the ET Streets? Should I start at 18 PSI and work my way down?
2. Im I out of HP to get my car to run lower 60 foot times? Do I need more HP to make the 60 foot times go down?
3. Is it something I do not see?

Thanks, this is really starting to bother me and I dont want to have to wait until November to run lower ET's.

BTW, the added HP and TQ came in the form of a 3" Flowmaster Y-Collector and 3" exhaust from the Y-Collector to the Cut-out and a Dyno Tune using LT1 Edit.

 

All you did was change chassis parts. You're down just over 1.5 mph. The MPH is a direct result of HP and you did nothing to change hp. I'd guess it's the weather conditions that made the loss of hp.

In your logs, what were the temperature, barometric pressure and humidity of each run? Heat and humidity will increase the density altitude as will lower barometric pressure. An engine makes less hp at higher altitudes. You can't compare days and say it was a nice sunny day with no wind. Those cold damp days are usually better race days than hot sunny ones.

Chances are you would have slowed down even if you didn't make any changes. It's possible the changes you did made the difference in poor performance better than would they could have been.

 

1. I have a proven +15 RWHP and +30 RWTQ added to the car. Which I would let account for a -.1 in the 1/4 mile.
I have loss 100+ pounds off the car's race weight. Which should account for another -.1 in the 1/4 mile.
Now given the above 2 details I should have loss time in the 1/4 mile not gained time. Am I wrong for assuming this?

2. When I added all the suspension parts I listed in the initial post and was hoping I would better my 60 foot time, but in fact it never even changed. My best time with Nitto 555's and stock suspension was 1.76. Now the I went to ET STreets and changed to aftermarket suspension I have only did a best of 1.77. I would have thought I would have been more around a 1.68-1.74 60 foot times. Again Am I wrong for assuming this?

3. I thought well maybe the reason I have lost 1-2 MPH trp speed was do to the change in rear tires. Changing out the Nitto's and going with the ET Streets. I have not played with the tire presure yet. I just head to the track and take it down to 12.5 PSI and work my way to 10 PSI a few times. I think I am going to start at 18 PSI and work my way down. Maybe I will pick up some trap speed that way.

And yes the weather was ideal the day I made the passes from 12.94-13.03 but when I did all those things tp the car that I mentioned I would have thought that I should at least run the same, and on an ideal day be around a 12.7xx. Now all my times are from 13.13-13.26. In warmer days with more humidity. I would give .1-.2 away for this, but the way I am figuring it up I should be at the 12.9-13.00 waiting for a coll day to drop in the 12.7xx's. Maybe I just dont see it.

 

Were you spinning with the Nitto's? Have you used the nitto's with the current combination? If you still have the nitto's,try them and see what happens.
12.5 psi is WAY too low to even consider with your combo. go to 18 maybe even 20 and see what happens.I have seen many "slower" (nothing against you,just the time bracket bolt on cars run) not benefit from a ET Street unless they were blowing the drag radials off.

As stated above,heat/humidity kills power. Almost have to find a comparable day on weather to ascertain changes were good or bad.
In "theory" yes you should of gained roughly 2/10's..but theory doesnt always apply to the track.
Also,you did a few too many suspension changes at once IMO. No biggie,just means you gotta work harder to find the combo.

 

I am unclear. What did you do to add horsepower?

I see less weight in the wheels and tires.
I see more weight in the chassis modifications.
I see ET Streets (I run about 14.5 pounds in mine and they hook fine).
I see a shift kit which should improve efficiency.

Weather can easily add or subtract a couple of tenths and a couple of mph. Easily. From real cool to real hot can even be three tenths... Easily.

If you were not slipping before, and you switched to ET Streets and are not slipping now, not slipping=not slipping so I see no drop in your sixty foot time based on traction.

Where did the 100 pound weight loss come from? That is a fair amount of weight. Where did the horsepower gain come from? 20hp is quite a bit.

Without accurate weather conditions, launch rpms, shift points, and any other variables to consider comparing performance is virtually impossible. I understand what you see on paper, but the key to determing the cause and effect is to quantify as many variables as possible.

In my opinion, you have too little air in the ET Streets and perhaps they are spinning on the rims???????? You may want to check, but that in itself isn't close to the whole ball of wax.

Keep thinking of things that could impact performance. You need to isolate and identify the causes.

 

I have Hooker Shorty Headers and was using the Y-Pipe that came with it. I switched to a Flowmaster Y-Collector. Also it was the stock exhaust pipe from the headers to the Cut-Out. I swapped that out to 3" exhaust now. Went to the dyno and using LT1 Edit I was able to kick my RWHP from 275 to 290 with the addition of the exhaust and tuning. I ran 4 times with it in the 290+ mark. This is where I got the addded RWHP from.

As for the weight loss, I was using 18" Helo full Chrome with Nankang NS2 Tires up front. The rears were stock 97 TA wheels with Nitto 555R's. Now I run Weld Draglights with 165R15 tires up front and the ET Streets in the rear. I took out the entire back seat and all the seat belts for the rear. Before I did this I weighed in at the scales at 3705 LBS. Last 2 times to the track my car weighed in at 3595 and 3599 LBS race weight. This was even with the addition of the suspension parts. That is where I got the weight reduction from.

I think you guys are right about the PSI in the rears. Next time I will start at 20 PSI and work my way down. It hooks pretty well without any spinning visable from the side lines.

Im doing this in a different order than adding 200 RWHP and trying to keep traction. Im doing all the suspension and etc. mods first, then when time and money permit add 200 RWHP.

 

12.5 psi is WAY too low to even consider with your combo. go to 18 maybe even 20 and see what happens.Perhaps they are spinning on the rims?
Without accurate va riables to consider compa perfor ringmance is virtually impossible.No call. Is it my understanding the tr dea is the problem? holler please , but the key to determing effect is to quantify as many var iables as possible.