Tried the Corvette Challenge race again at Englishtown on Sat.
I ran a couple new best times during time trials (12.68 at 105.9), with two good reaction times. (Good air plus reset ignition timing). So in the first round of eliminations, my reaction time was off and I got beat.
See timeslips below. Timeslip on right was 1st round.
BTW - Since my 60 ft times stay close, can anybody explain why my ET varies from 12.68 to 12.74?

 

That's not really a huge difference in ET, but you can get a variation if you staged differently each time, and only the really experienced guys get to the point where they stage exactly the same each pass.

For example, if you stage very deep (but both lights are still on), as soon as you move forward a fraction of an inch the timer will start.

OTOH, if you stage shallow (but still both staging lights are on), you will get a slight rolling start before you trip the light and the timing equipment starts which will put you through the 1/4 mile at a slightly quicker time. Just a theory.

 

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.006 differential is nothing, nothing wrong with a high 12. second car

One reaction time is .002 from a Red Light

 

Though temp didn't change much the baro seemed to be dropping as the day went on. Looks like from MPH and incrementals you were down a little HP that was starting to show up at the end...but for sure from the 330' point onward.

The first run had low temp, high baro and it appears it just spun a little maybe. I would also question the carb jetting...maybe you're just a tad on the rich side?

The reason I think that is that everything on the 2nd run looks better. The baro is only slightly lower..but you hooked...and it got good MPH, whereas the 1st run didn't. *IF* it's a little fat..it would be a little pickier about the lower baro possibly.

Comparing 1st and 3rd runs, it's interesting to see that the 1/8th mile times were better...mph was down.....but you ran the same 1000' time. It came back alive after the 1/8th mile. The 2nd and 3rd pass were pretty close other than MPH dropped off on 3rd.. It pulled a LOT better after the 330' on the 2nd pass than the others. If anything happened..it should show up there. What was different? Did secondaries feel to open to early on other passes and hesitate some?


Any idea what Humidity was doing?

You need a weather station to really drill in this close.

Either way. looks like great runs and a fun day!


JIM

 

What did you put as your dial in time? with a .688 and a .736 your dial in should have been a 12.71 or 12.72 and if you are in front enough back off or even brake. Just so you don't break out.

The late light killed you though.

Less than .06 is pretty good unless your car has major setup adjustments.

The track and air can change the time more than that.

 

.oo1 RT? Sick

 

Thanks for the suggestions guys.

PRNDL - I try to just barely get the second prestage light on every time.

Ironcross - Just a little math correction - .06 range of ET, not .006.

JIM - One thing I didn't mention, I was off the gas just before the stripe on the elimination run. The other guy had me by a nose. As for jetting, I'm using a Qjet so its not so easy to change. I think the air temp going up slightly and barometer going down explains it with the second run being best because of the .01 difference in 60 ft time. Not sure about humidity but I did hears guys saying DA numbers were getting worse as the day went on.

gkull - I was dialed 12.67. I didn't take into account the weather change. I wonder about the .06 spread because the car leaves so consistently (only .01 variation there).

Canuck - The .001 light was wasted on a time shot. I needed that in the first round.

 

I never put a time faster than I went in practice. I was the on the brakes master. You can let off if you are out in front but you can't make a car go quicker.

This winter might be a good time for a bigger cam

 

BK, I have taken the liberty of breaking-down your 3 runs by segment, which may better-help understand where the runs differed on this day:
TT#1 in Blue, TT#2 in Red, E#1 in Black.

0000-0060 : 1.778 - 1.744 - 1.767
0060-0330 : 3.397 - 3.408 - 3.402
0330-0660 : 2.905 - 2.896 - 2.909
0660-1000 : 2.520 - 2.518 - 2.525
1000-1320 : 2.136 - 2.122 - 2.140

You say that you lifted right-at the stripe in E#1, but I am not-sure that accounted for any ET variance, especially from TT#1:
comparing TT#1 & E#1, you were .011 quicker to 60' in E#1, yet only .006-quicker at 330', just .002 'ahead' at 660', and by 1000, you were .003-slower that TT#1.

In-effect, the further you went, the behinder you got, and this is backed-up by the slower MPH at 660', 84.29 to 84.19:
it's not-much, but we are trying to account for every thousandth of a second.

I did some calculations, and figure that your ET to 1254' to be 12.307, 12.263 on your second run, and 12.3151 during Eliminations, just a few .001 slower than TT#1, so it is quite-possible that you didn't scrub-off any ET when you lifted.

As has been stated before, for every .010 your 60' varies, you can expect the 1/4-mile ET to vary by approx .015, meaning your variance is another 50% the final 1260' of the run:
this time is similar to 'momentum', and once you lose it, you usually can't regain it without running-under or breaking-out.

Comparing TT#1 and TT#2, we see a 60' improvement of .034 (1.778 - 1.744), and .034 x 1.5 = .051 ET improvement:
TT#1 ET of 12.736 - .051 = 12.685 (projected ET, based-on 60' improvement), and you ran 12.688, a descrepancy of just .003-seconds from our calculations.

It might-not be that your 'tune-up' is wrong, as-much-as your 60' varied on those 2 time-runs:
had you gone 1.77 and 12.71-12.74 on TT#2, you'd have dialed closer to the actual ET it ran in Eliminations, but that 1.74/12.68 got you all hot-and-bothered, thinking the car would continually go-quicker/faster, hence your lower dial-in of 12.67.

If you are going to concentrate on 'bracket-racing', as-opposed to 'going-fast', you might be better-served by being satisfied with 1.77-ish 60' times with your current set-up, even if it means giving-up some ET, while striving for consistency over all-out Low ET:
would you rather lose running inconsistent-but-quick, or WIN running a respectable ET?


i.e. - find-out WHY you had that abnormal 60' time in TT#2, and if you can't repeat that 1.74 short-time, gladly take 1.77 all day long:
just make-sure they spell your name correctly on the Winner's Check!


Hope this helps!