ET v MPH help

[Mk3Les]

I took my car to the drags for the first time on the weekend. It’s a full weight ma70 5 speed 7mgte with 340-rwhp, dyno sheet below
http://www.supramania.com/forums/showthread.php?t=72758

Anyway my times were a bit disappointing, I understand trying to launch with 18inch wheels is hard and I’ll fix that before I go again. It explains why my 60ft times are so bad, but what I can’t work out is why my trap speed stayed pretty constant. I don’t have the scanner hooked up yet but here is what I go for the three runs I did

1st run
60ft 2.376
330ft 6.136
660ft 9.220
mph 79.87
1000ft 11.812
ET 13.98
mph 100.45

2nd run
60ft 2.581
330ft 6.487
660ft 9.571
mph 80.39
1000ft 12.155
ET 14.316
mph 99.6

3rd run
60ft 2.828
330ft 6.854
660ft 9.960
mph 79.76
1000ft 12.558
ET 14.721
mph 100.94

As you can see I got worse each run! But how does my top end still manage to stay the same? I should be slower shouldn’t I? I’ve searched but cant find any info if someone could point me in the right direction it would be a great help.
Also I found some information that suggests by cutting .1 off your 60ft = .2 at the end of the run is that right?

 

[Slow66]

Your MPH is more of a function of how much power you are making. You trapped basically the same on each run most likely because the conditions were probably consistent between the runs and you were making the same power on each run. The ET varies greatly with the 60', and it should. General rule of thumb is that a .1 reduction in 60' will = a .2 reduction in the ET. The trap seems a little low for 340whp too. Any issues with the motor?

 

[Tun_x]

Bet a set of tires/slick and it will be the single best mod to your car to date.... It will net you the most ET

 

[NAiL05]

How are you launching the car?

 

[Mk3Les]

Hey thanks for taking the time to share your thoughts guys,


SLOW66
Your MPH is more of a function of how much power you are making. You trapped basically the same on each run most likely because the conditions were probably consistent between the runs and you were making the same power on each run. The ET varies greatly with the 60', and it should. General rule of thumb is that a .1 reduction in 60' will = a .2 reduction in the ET. The trap seems a little low for 340whp too. Any issues with the motor?

The only issues I’m having right now are a leaky blow off valve and an OS Girken twin plate that seems to be a bit temperamental (makes random strange noises but seems to grab well) both will be fixed before I go again.
As for the HP the only thing I can think of is that the Dyno might have been a bit generous



Tun_x
Bet a set of tires/slick and it will be the single best mod to your car to date.... It will net you the most ET

I’ll be doing that as well. I’m a bit stubborn and wanted to run it as it’s driven on the street which meant running with my 18’s. The car didn’t feel like it was wheel spinning but looking at my 60ft’s it had to be, I just didn’t feel it.

Nail05
How are you launching the car?

My first run I left the line at around 1500rpm and got my best 60ft
Second and third run I thought I’d try a bit harder and left the line at around 3000rpm.
Funny thing is my two slowest times felt faster than the first run. As I said in my reply to Tun_x I’ll be getting some sticky tires/slick’s before I have another go.