Where'd my MPH go?

[Squishmytomato]

I put the ET streets on tonight expecting to see 11's, and did not hit them. For some reason, I couldn't get the car near 120mph like last week (on the Nitto drags). I had the heat exchanger running when the car was off, ice on the blower, cool down for 30 minutes, etc. We even tried pushing the car through the staging lines with ice on the blower.

LAST WEEK:
60: 1.883
330: 5.188
1/8: 7.927
MPH: 89.59
1000: 10.252
1/4: 12.180
MPH: 120.01

LAST WEEK:
60: 1.906
330: 5.233
1/8: 7.959
MPH: 89.22
1000: 10.272
1/4: 12.197
MPH: 120.61

THIS WEEK:
60: 1.807
330: 5.112
1/8: 7.872
MPH: 87.06
1000: 10.205
1/4: 12.173
MPH: 118.38

THIS WEEK:
60: 1.884
330: 5.183
1/8: 7.936
MPH: 91.36
1000: 10.261
1/4: 12.200
MPH: 115.34

THIS WEEK:
60: 1.848
330: 5.126
1/8: 7.914
MPH: 90.37
1000: 10.256
1/4: 12.222
MPH: 113.39

If anyone can analyze this and tell me what's up, I'd greatly appreciate it. I know I can do better on the 60 ft times (high 1.6's-low 1.7s will be attainable with some practice), BUT what is up with my MPH? Notice how on my 2 runs where I trapped under 116, I was well over 90mph in the 1/8th, which I did not hit last week. The other run where I hit 118 (my highest of the night), I was only at 87 in the 1/8th. Last week on my 2 best runs, I was at 89 and hit 120. Is it the tires? Bad shifting? I have no idea. I go through the 1/8th mile marker in 3rd gear I am pretty sure, so it can't be the 2nd to 3rd shift? Or can it?

 

[QWKRN U]

Loose Nut behind the Wheel. oke:

 

[Squishmytomato]

According to a couple basic calculations, I have the corrected elevation at well over 1800 ft for tonight, which sucks compared to last week's ~500-700ft. 2 weeks ago, it was actually at negative elevation. I think the atmospheric conditions just sucked tonight.

How big of an effect does that have?

 

[QWKRN U]

Alot
answer that question for yourself. How does your car feel on a night when its 40 degree's out versus a night when its 80 degree's out.

 

[cobrafever]

Well, did you run tubes in your ET streets..????, if so, there is more weight, run em tubeless. Also what size ET streets were you running..???

 

[Orr89rocz]

were u in the same lane each run?

and is your car lowered at all? or does the front end sit very low?

and how was the weather conditions on those days? weather can affect mph by a few but what ur seeing seems to be on par with what happened to me.

my irocz sits very low in the front... the air dam deflector is like 3 inches off the ground or so.
in the RIGHT lane, i'll run IDENTICAL ET's thru the 1/4 mile as the LEFT lane... even the same MPH in the 1/8 mile... but my RIGHT lane mph in the 1/4 is 92-93mph where the left lane is 100mph..... its something to do with the track layout and my front air dam hittin the beam too late or something like that.

 

[Evil_SVT]

what is your hp and tq? what are your mods that will help out in telling you where you are messing up.

 

[STAMPEDE3]

were u in the same lane each run?

and is your car lowered at all? or does the front end sit very low?

and how was the weather conditions on those days? weather can affect mph by a few but what ur seeing seems to be on par with what happened to me.

my irocz sits very low in the front... the air dam deflector is like 3 inches off the ground or so.
in the RIGHT lane, i'll run IDENTICAL ET's thru the 1/4 mile as the LEFT lane... even the same MPH in the 1/8 mile... but my RIGHT lane mph in the 1/4 is 92-93mph where the left lane is 100mph..... its something to do with the track layout and my front air dam hittin the beam too late or something like that.

Had that problem too.

What gear do you finish in, 3rd or 4th?

 

[2k1cobra]

Somethings not right on your 120 1/4 traps your only trapping 89 mph in the 1/8. Most pullied cobra trap 92-94 MPH and on your slow 1/4 runs you trapped 90-91 in the 1/8th? :shrug:

 

[Squishmytomato]

were u in the same lane each run?

and is your car lowered at all? or does the front end sit very low?

and how was the weather conditions on those days? weather can affect mph by a few but what ur seeing seems to be on par with what happened to me.

my irocz sits very low in the front... the air dam deflector is like 3 inches off the ground or so.
in the RIGHT lane, i'll run IDENTICAL ET's thru the 1/4 mile as the LEFT lane... even the same MPH in the 1/8 mile... but my RIGHT lane mph in the 1/4 is 92-93mph where the left lane is 100mph..... its something to do with the track layout and my front air dam hittin the beam too late or something like that.

Whoa, that's really weird. I just noticed this:

My trap speeds in the left lane NEVER exceeded 115mph, but my 1/8th mile traps were frequently over 90mph.

In the right line, I hit 120, 120, 118, 117, etc. However, my 1/8th mile traps were ALWAYS under 90mph. The best was 89mph.

 

[Evil_SVT]

what are your mods? how much hp/tq?

 

[Squishmytomato]

what are your mods? how much hp/tq?

2.93, MGW shifter, LFP HE, Subframes, Lowered, Exhaust, Intake, H pipe

450hp, 460 lbs ft

 

[Evil_SVT]

well with that hp and et streets its definitely your shifting.
Purchase a raptor shiftlight and practice your 2-3 3-4 shift becuase it appears thats where you are loosing time/mph.
bang them gears!

 

[Goo]

Clutch?

 

[spyder1337]

Is his belt slipping? It looked like your 1/8th is on track and then seems to fall on its face towards the end on your recent runs? Maybe your tune might be messing up with the change in climate.

 

[o3SnakeBite]

Sounds like a clutch

 

[Squishmytomato]

The clutch is not slipping to my knowledge, but the engagement point has gotten closer to the floor if that shows anything. It could be clutch or belt slippage, I will check both.

 

[STAMPEDE3]

From what I see the car is pretty consistant through the 1/8th mile and ET wise in the 1/4.

The only difference is trap speed correct?

I'm sticking with the timing thing because I've seen it before.

Trap speed is measured over the last 60 or 66' of the track (I can't remember which)
If the first timing light is too high it will hit your air dam/bumper and start timing.
Last light is correct and hits the tire, that's what 1-1.5 feet difference.
At 120MPH your moving about 20ft or more per .1sec. so you cover the last 60' in .3
That 1.5 ft difference in bumper to wheel when the computer calculates makes a big difference.

I normally trap @104, one night it was right lane 103-104, left lane 96-99. (A lot of cars like ours were off)
Brought it to their attention the went adjust the light and then it was 103-104 both lanes.

 

[Orr89rocz]

it have to be timing of the track

i dont see how u would be running nearly the same ET's but lose 5-6 mph or so. 5-6 mph is ALOT of power loss...you would lose ET on the top end

but do check for any mechanical problems and work on your shifting to become as consistant as possible. then run both lanes as equal as you can and see if anything is different.

also talk to others out at your track.. they might be experiencing the same thing. thats how i found out about my track's problem