1/4 mile time interpretation

[4piknup]

hi all 1/4 mile masters.
i have a gtech pro and a flattish bit of road, i only run 1 way and same take off point everytime.
if i short shift 1st i get worse et but better mph, and hold 1st for better et but worse mph. is this normal?
eg, 2 runs 3 min apart:
run 1
16.022 @ 89.77
60' - 2.7 @4059rpm (clutch coming out about to grab 2nd gear)
330' - 7.08
1/8 - 10.6 @ 73.72 mph
1000' - 13.3
60mph @ 8.009

run 2
15.6 @ 85.05
60' - 2.467 @ 7210rpm ( top of 1st, just start pressing clutch in for 2nd)
330' - 6.684
1/8 - 10.14 @ 74.67mph
1000' - 13.070
60mph @ 7.5

i want to try leaving in 2nd gear to see what that does???
is this normal? it pretty slow i know, but not worried about that for now, just trying to get some runs in to show any improvements, when and if they improve.

if you not familiar with gtech then mine is same as:
http://www.gtechpro.com/rr.html
similar to new one, but no gps. no worries for a straight liner like me. plug into smoke lighter and away you go. for accurate hp you need to weigh car.

 

[ONPSI]

It's all part of drag racing mate..you'll never run bang on the same time run after run.
So many factors that change results...lazy shift speeds or short shifting or over reving peak power, just because your car redlines at "X" doesn't mean peak power is at redline. If you had a dyno sheet you'll see exactly where peak power is and aim to set your shift light just on or after or wherever it be.

 

[Smutt]

Try to be consistent, start off at same rpm, change at same rpm in every gear with the exception of possibly holding 4th across the line if your geared that way.

Knowing when to change gear once peak power is reached can only be found out from use of a dyno as "onpsi" said

Your mph is a direct indicator of horsepower,
you can stuff up your run (miss a gear costing you 0.5 seconds) but still get within 1mph at the top end I have experienced (with 45 mins between runs that is).
a loss in mph and horsepower may be an indicator of a hotter engine running back to back,
ask many drag racers and they will often say their best times are done straight off the trailer (first run for the night)

I found my 60ft times were best launching at 5000 to 5500rpm as opposed to anything higher because first gear is longer from a moving point of view, its a balance between bogging and not bogging off the line, you can aid this by fiddling with tyre pressures also (i prefer 25psi)

If your 60ft times start slipping away and everything else is consistent then this maybe an indicator of your clutch slipping, and equally if you think your clutch is packing it in (overheating) then look at your 60ft times.

After you have got the consistency sorted then change one thing at a time, but again dont expect your mph to change unless you have a reason for increased hp ie. add more boost or timing etc..

Another key point to drag racing is: for every 0.1 second gained in your 60ft time, double the gain (0.2 sec gain) for your ET at the other end!!!!!

Practice, Practice, Practice.... once your in the staging lane you have adrenalin to deal with also

 

[4piknup]

thanks guys.
ok, i will look at hp/rpm graph on gtech and report back. i will try to find a way to show graph on here.
so should i try to run consistently at run1 or run2. or doesnt it matter and depends if chasing et or mph.

 

[caged]

usually a better et does slightly lower your mph.

 

[Smutt]

usually a better et does slightly lower your mph.

Agree, but that can be a bit confusing for some. Because your utilising max Torque rather than max HP.

Dont we all just chase the ET.. the mph follows naturally, its all about power to weight and delivery of the power.

Focus on getting your 60ft time down and reap the results at the top end, ET wise.

Run 2 is better, your 60ft time is heaps better, dont know if your going to the top of every gear after that.
Try first gear long and slightly shorter shift for the rest of them (but 7000rpm may be a bit high for first)?
So so many factors, starting rpm can have a chain reaction for the rest of the run, good or bad.
Theres consistent quick gear changing also, missing a gear costs me 0.5 sec generally..

Some ideas for ya anyway

 

[4piknup]

ok, we try again next week.