Shift point

Question for all the KZ drag racers, approx how far down the track is your 1-2 shift happening? Reason for asking: Went to T&T last night to start practicing with a delay box to see if i like and i forgot to turn on the autoshift, my 60 time dropped to a 1.53 from my usual 1.59-1.63. This got me thinking my 1-2 shift is happening before i get to the 60' line. Also i realized a couple weeks ago Im shifting into 5th just after the 1/8 mile line. Setup: slick, bar, 1stage lockup,airshift, 14/42 final ratio, Averages 120 mph @10.90 sec 

Personally, don’t be too worried about where your 1-2 shift is, but more what RPM you’re crossing the finish line at.  If you’re
leaving some engine speed on the table at the 1/4m mark, gear down slightly.  Watch
some NHRA ProStock cars’ in-car videos, they cross the line at an rpm that is just kissing the rev-limiter. Granted they have way more adjustability with transmission ratios but the principle is the same.

Later, Doug

This is the first time I have ever heard that question, and I believe its something you don't need to worry about or can even physically control. 

For sure you would do that shift within 60 feet but could only capture that with a data logger or video camera. The more HP you make the farther out that shift will occur.

There is too much going on in your brain when riding to mentally think about the 1-2 shift as it happens so fast. Your thinking about so many different things when launching, and mostly worried about messing up the run!

Like StreetfighterKz mentioned you should try to capture what gear and RPM your going thru the traps, that is a easy one for your brain to remember as the rest is just body position, weight transfer, and muscle memory. This is also important for finding the correct gear ratio for your setup (HP and package weight)

On a small tire slick bike you want to run high RPM as that is where you can run it the quickest/fastest.

Something is wrong gearing wise if your in 5th at the 1/8 mile if running 1/4 mile (unclear in your description)

Not sure what your engine specs are but it sounds like small CC small HP weekly points bike setup. Also sounds like the overall package weight may be heavy. These are not digs, just trying to understand your setup.
 

Just to give you a bench mark I bought a roller off a guy who gave me some of his timing slips when I bought the frame.

His setup was as follows :
1075cc 
32 Lectrons
MTC slider
delay box
full auto tranny
7" slick wheelie bar
~550 lbs Total weight (360 lbs bike)
15/38T sprockets
9.28@142MPH in quarter

 

This was a weekly points series bracket race bike, last raced in 1999.
 

For me, (way back in the day), with my particular set up, shifting from 1st to 2nd was very early, maybe 60 ft. But as mentioned there are way to many variables that can effect that. I guess you just want the shift point at the max power band, rpm, and not before it or after it... That's what makes figuring that out so much fun at the drag strip. And the smell of burning rubber also...
Some of my time slips from the shoe box of yesteryear....

Injected wrote:

Just to give you a bench mark I bought a roller off a guy who gave me some of his timing slips when I bought the frame.

His setup was as follows :
1075cc 
32 Lectrons
MTC slider
delay box
full auto tranny
7" slick wheelie bar
~550 lbs Total weight (360 lbs bike)
15/38T sprockets
9.28@142MPH in quarter

 

This was a weekly points series bracket race bike, last raced in 1999.
Those numbers seem like a dream to me, i must be doing something very wrong
My setup:
1075 cc 
web cams #118 grind
RS 34 Flat slides
200 psi compression
delay box
5" slick wheelie bar
750 total weight
14/42 final ratio
best mph 123.00
Best 10.74
 

Two hundred pounds can make quite a difference. Also, we do not know what cams were in that quick bike.
Forty percent more rubber on the ground surely did not hurt, either.

Regards to fellow drag fellas!! Southpaw. Nobody looks at the tachometer. It's merely a token of display. When running ANY engine You can "feel" it. Whether in the harmonics of the seat or muffled in the helmet, You know when you've gone to far. I chuckle when i see persons with those Big-O display tachs crowding the instrument area..worthless unless you're pulling the salt flats.    

I do watch my tach towards the end on every run, wanna see what im crossing the stripe at. 9600-9800 rpm

I think those numbers are pretty good for the weight and power output. If you want to go faster you need to drop weight and up the HP.

Most drag bike engines are +250 PSI, and one guy I talked to doing points series was "+300 PSI" 

Sounds like you have street bike pistons (10:1 comp) in the engine. Easiest way to bump compression is to switch to a 13:1 piston as its a bit more expensive to massage the head to achieve the same result (but possible)

I think the 1075 engine I quoted would have been running some cams bigger than .435" lift.

Actually it has either 12.5:1 OR 13:1 pistons im not sure they were slightly used. Considering putting in Web Cam #110 .395 lift cams in next year

wrote:

Actually it has either 12.5:1 OR 13:1 pistons im not sure they were slightly used. Considering putting in Web Cam #110 .395 lift cams in next year



 

OK, sounds like you need to concentrate on the head/cams. Has the head been worked on? 

I don't know anybody who runs shim over on a drag setup. Most run as big a cam as they can to get big CFM out of the head.

The target for my 1327 drag engine for the head was a 34cc combustion chamber volume (as prescribed by my porting guy) That took my pistons from about a 12:1 ratio (cut down MTC 13:1 pistons) to about a 16:1 ratio. You can deck the snot out of a Z1 head but you need to sink the valves deeper to compensate. I decked mine till the piston dome was "almost" locked in the combustion chamber when placed on it by hand.