Is lunging / hopping in the seat an effective practice?

(Andy Kutscher) #1

As the title states, I often see videos of racers who lunge forward or hop in the seat of their kart in what appears to be an attempt to gain momentum under acceleration.

Has anyone ever tested this with data to determine if there is an actual benefit?

(TJ Koyen) #2

Excellent topic to really dig into during winter months! I’ve turned this idea around in my head thousands of times over the years.

I don’t have hard data, but of course if you hop in the seat, you can see your RPM jump as you lighten the rear wheels. Newton’s Third would say that every action has an equal and opposite reaction, so if you hop and it causes the kart to bounce and lighten, it also has to land back down with equal force at some point, so you would think it would offset the gains. However, when you hop, if you gain let’s say 300RPM, does the engine then have more torque in that rev range and therefore when the force increases as you land from your hop, does it pull through that added force better and cancel out some of the drag you would experience?

My thought is yes, it would, so hopping would offer ever so slightly better pull off the bottom end, but it’s almost negligible. What comes up, must come down, but if you can get the engine to pull slightly harder on the come up, then the come down isn’t as detrimental.

(Andy Kutscher) #3

I’ve always dismissed it as not really effective.

watching a random video earlier today is what made me really wonder. Check this video out at 8:30 mark.

(TJ Koyen) #4

In that video I think it’s just the red kart not scrubbing off all his speed like the camera kart did, and it was his momentum that carried him past rather than hopping in his seat.

I do it sometimes, especially on starts.

I don’t know as though it’s doing much. But maybe a little.

(Dom Callan) #5

I only see the juniors doing this. I’m guessing once you weigh 150lbs plus it becomes less useful?

(James McMahon) #6

Two situations I’ve seen where this makes a big difference…

Micro Rotax “Turbo” although I believe that’s been resolved.
Highly tuned direct drive (non clutched) motors that essentially die when they “fall off the pipe”. A good enough jump will spin the wheels, get the motor up on the pipe and give you a bit of a boost if you screwup and turn and bog down.

(Eric Gunderson) #7

All I know is…I’ve lunged forward in the seat as I came to the line in a side by side battle for the podium and it worked :slight_smile:

(Matthijs Hofman) #8

This is one of the few times where my rental kart experience is useful. Hopping in the kart is common practice at race starts in rental karts. TJ Koyen is spot on when saying that hopping has both a positive effect (making the kart lighter to improve acceleration) as a negative effect (making the kart heavier when coming down).

I experienced that in the period that revs are really low and the engine has difficulties to pick up (the first 10 or so meters after the start) the hopping actually helps a little to increase acceleration. I also found out that hopping at higher speed is counterproductive: acceleration is less compared to others that don’t hop. So apparently (in a rental kart) hopping is only useful when driving almost zero miles an hour. It must have something to do with the low revs, like TJ mentioned.

Second: I think that lunging forward at the start, rather than hopping, has a more positive effect. Although the gain with both techniques is negligible.

(Matthijs Hofman) #9

Eric, throwing your transponder forward may be more effective here :slight_smile:

(Dom Callan) #10

I put my transponder on a selfie stick…

(Paul Montopoli) #11

I don’t do it much but I am confident that in the right situations it works. I used it in Rotax Masters (405 lbs) at Homestead at the slowest point of the track - a hop combine with a lift and then slowly rolling back onto the throttle. Kart took off.

(TJ Koyen) #12

It should be noted, as @KartingIsLife did with the MiniMax “turbo” phenomenon, that certain engines may have some peculiarity where hopping has a greater effect. On a Rotax, if you can hop and bump the RPMs up off a corner to get it back on the power valve, you’ll get a boost of power off corner like you’re describing here Paul.

I remember when I ran Rotax Max last (Pro Tour 2012) at Phoenix, going up the back straight if you hopped at max RPM, you would get over that hump in the power curve and you’d get a top-end boost. Or sometimes if you hopped it would stumble and fall on it’s face on top speed… Typical Rotax black magic voodoo.