52 replies to this topic

[Pidgeon]

I am going to have to dissagree with the comments of engine braking hindering the cars performance - it's absolutely essential. If you're unsettling the car or doing it too early, you're doing it wrong, very wrong. Don't forget that heel-toe is also essential if you're engine braking. The limitger does not protect the engine on down shift. Not heel-toeing means you run a real risk of buzzing the engine.

You say you disagree, but the purpose of H + T can be to minimise engine braking. The finest exponent of H + T will minimise engine braking to zero.

H + T is to match engine speed in the lower gear to road speed. The clutch comes up when the engine speed matches road speed perfectly, so no engine braking. Looking at it the other way, if you wanted to maximise engine braking, you would downshift as soon as the brakes had removed enough road speed for you to engage the lower gear at maximum engine revs, no H + T involved.

Best practical illustration I have had was driving one of Johhnie Palmer's Clio Cups in the wet. Anything other than a perfect H+T locked the fronts, which remained locked until I was out of brakes. Fortunately, I consider FWD to be the work of the devil and avoid wherever possible.

(BTW, H+T dooes not protect the engine from being buzzed. If you've got the wrong gear for roadspeed, that engine will buzz whether you've H+Td or not. )

[System-G]

True, but you're still using the engine to assist with braking - a fair bit more than most would assume. However, It's not like using the engine a lot with an old-school solid dowshift And True H&T does not prevent the engine from being buzzed, just minimalises the chances if you've matched the revs correctly

[MellowYellow]

I once had issues with a customers MK2 Escort rally car breaking propshafts during downshifts on tarmac events, the amount of torque generated was pretty much on the limit of the joints in the shafts when using slicks (not got my little book of equations handy to explain the slippage etc), factor in the unknowns of a bump while braking (extra loading = more grip, no skidding) into the equation and it was enough to snap the joints. Just goes to show that engine braking can be a very potent tool if you can control it

[bunsenburner]

I once had issues with a customers MK2 Escort rally car breaking propshafts during downshifts on tarmac events, the amount of torque generated was pretty much on the limit of the joints in the shafts when using slicks (not got my little book of equations handy to explain the slippage etc), factor in the unknowns of a bump while braking (extra loading = more grip, no skidding) into the equation and it was enough to snap the joints. Just goes to show that engine braking can be a very potent tool if you can control it

And still pretty potent if you can't

[Pidgeon]

I once had issues with a customers MK2 Escort rally car breaking propshafts during downshifts on tarmac events, the amount of torque generated was pretty much on the limit of the joints in the shafts when using slicks (not got my little book of equations handy to explain the slippage etc), factor in the unknowns of a bump while braking (extra loading = more grip, no skidding) into the equation and it was enough to snap the joints. Just goes to show that engine braking can be a very potent tool if you can control it

Or alternatively, use the brakes for braking, not the transmission, as one is designed to cope with those forces and the other isn't. Your customer should have learned to heel and toe to avoid putting that stress on the tranny.

Sad thing is, I don't H + T in the VX. Walshy showed me how I could, but the level of anatomical distortion causes sufficient pain to distract me from the job in hand

[techieboy]

Sad thing is, I don't H + T in the VX. Walshy showed me how I could, but the level of anatomical distortion causes sufficient pain to distract me from the job in hand

Same as that. Just seems a physical impossibility from where I'm sitting.

[siztenboots]

just checking but is the pedal box firmly attached to the chassis as they have been known to break the pop rivets and bonding material. http://www.vx220.org...ylinder-rivets/

[Pidgeon]

F@ck me, are you trying to scare me? I'm no worrier, but now I need to consider whether the M/C will fail catastrophically or the pedal box will simply sheer off

[slindborg]

F@ck me, are you trying to scare me? I'm no worrier, but now I need to consider whether the M/C will fail catastrophically or the pedal box will simply sheer off

Or both

[SteveA]

Steve, if you're you're not using the engine to help brake a bit, what purpose are you heel-toeing for?

Am I missing something here? I use H&T specifically to minimise engine braking (that's what its for)

Edited by SteveA, 16 June 2011 - 10:37 PM.

[System-G]

Was just winding you up mate - hence the smiley Sorry if it got lost in translation

[SteveA]

No problem, I guessed it was supposed to be something like that but it was a long day yesterday and my brain couldn't figure it out

[System-G]

It's why I hate forums. Humour often doesn't come out right...