FrenchBoy

What exactly is happening when the engine 'Bogs Down' on a launch?

I was trying to do a few at the weekend and even with 5k dialled in and a clutch sidestep, i was still getting it.

I thought this was the preffered method for a good launch with a scoob.

Jay m A

iTrader: (2)

Do you hold the throttle steady when you sidestep? Thats probably why you bog down. You need very little throttle to get 5000rpm with no load. Soon as the clutch comes in you have to increase throttle to maintain the 5000 revs.

If you are sidestepping then you practically have to mash the throttle at the same time. Not reccommended though.

Briskly let the clutch in, yes - and when you do briskly increase the throttle to maintain those revs. As you know this all happens very quickly so keep practicing

FrenchBoy

Jay,

I thought i was flooring the throttle, i get a little wheelspin and then it bogs.
TBH i got my best time feeding it in. I was just a little surprised that dumping the clutch didnt seem to work as well. Although i'm sure this is more due to my lack of ability.

i'm still interested to know the technicalities of 'bogging down' though...

grahamfrary

Bogging down generally means you are trying to accelerate (WOT) but the revs have dropped to the extent that you are too low on the power/torque curve to get reasonable acceleration. Also called 'off-cam' on cammy engines. Unless you change down (difficult in first) you either have to wait for the cam (turbo) to come in, or slip the clutch to bring the revs up and regain the power/torque.

Graham

les1

you'll need to experiment with raising your rpm on launch, to the track conditions on the day, but if your bogging at 5k, you'll need 6k??
find out where your engine makes its peak torque, and launch there, as thats a better place to start, torque is what gets you off the line not bhp., bhp is for mph, thats how you can calculate your hp with Terminal speeds/weight etc.
Bogging as Graham said, is where your engines spinning at say 5k rpm, it then gets hit on the head if you like by the clutch, and if there's not enough torque to pull itself out of the situation, (where rpm has dropped to the point where your well out of the power band), momentum will slow down to the point where the only way to regain the momentum, is to reduce the load, dip the clutch..........you could try to use a 25/50 shot of Nitrous on launch, I think this would help a lot, as N20 produces a lot of extra torque with it.

When I was Drag racing years ago with street cars at first, I tried all types of startline techniques, driving off, hammering it etc, the fastest ET's were normally generated by blasting it, letting the tyres spin through 1st and sometimes 2nd, although that is actually NOT what Drag Racing is all about, but for a street tyre, it was the fastest way. You on the other hand can use Drag tyre thinking, because spinning is not the problem. Its ALL about raising your hp/torque levels on launch to a point where you can overcome the mechanical grip thats available.
If you think about a Pro-Mod car, 1500bhp+, they use a Lenco trans with a clutch, you'll hear them on the limiter at the start, at say 6/7000rpm where there making most of that 1500hp, reason, they know they have almost absolute grip at the start.....the quicker that first 60ft, the quicker the ET.

les

mattstant

this in not the sort of thing i do usually but as soon as my 03 PPP wagon was run in i went out to find out if prodrives claim of 4.8 0-60 was true (no stop watch just for the general feel).

I thought the prescribed method was for a quick blip of the throttle to around 5000 rpm to get the turbo spinning then dump the clutch and step on the throttle it certainly worked for me and it certainly felt a whole lot faster than my old uk 99 wagon.