Why blip (rather than hold) the throttle?

[Sconch]

OK. I've looked long and hard on the internet for the answer to this but I can't find it.

What exactly is the purpose of blipping the throttle on a downchange?
And before you give me the textbook answer, I understand why you want to match engine revs to the driveshaft revs.

What I don't understand is why this is done with a "blip". Unless my interpretation is wrong, a blip is a very quick and temporary rise in engine revs. How does this help? Assuming you blip to the right revs so that when you engage the clutch you get a nice smooth gearchange, surely you are then immediately into engine braking.

Why do you not instead hold the revs at the right point, rather than coming off the throttle again. Then you get the smooth gearchange, followed by neutral engine acceleration/braking.

I'm sure I must be missing something.

Edited by Sconch on Thursday 30th July 09:59

[fatboy b]

And how do you assess what is the correct engine RPM for the roadspeed for the gear you want? A blip will, as some point, pass through the correct rpm without actually having to know the correct rpm, and with gentle pressure on the gearstick at the same time, it will slip in nicely when the rpm is matched.

[Altrezia]

and surely you're breaking when down-changing anyway, so engine braking isn't the worst plan in the world?

[RB Will]

Sconch said:

OK. I've looked long and hard on the internet for the answer to this but I can't find it.

What exactly is the purpose of blipping the throttle on a downchange?
And before you give me the textbook answer, I understand why you want to match engine revs to the driveshaft revs.

What I don't understand is why this is done with a "blip". Unless my interpretation is wrong, a blip is a very quick and temporary rise in engine revs. How does this help? Assuming you blip to the right revs so that when you disengage the clutch you get a nice smooth gearchange, surely you are then immediately into engine braking.

Why do you not instead hold the revs at the right point, rather than coming off the throttle again. Then you get the smooth gearchange, followed by neutral engine acceleration/braking.

I'm sure I must be missing something.

You are doing it in the wrong order.
First you disengage the clutch then you blip to bring the revs higher up to match the lower gear ration then you engage the clutch performing a nice smooth downchange.
If you kept the revs where they were they would not be right for the next gear and you would either get a jolt as the car tries to go forwards if you change up or massive engine braking if you change down.

[youngsyr]

The engine rev raise on the blip isn't temporary, you blip the throttle to increase the revs to where they should be at that speed in a lower gear.

If you're in 4th at 4,000 rpm, engage clutch and change down to 3rd, say you're now at 5,000 rpm.

If you blip the throttle whilst the clutch is down, your revs should go from 4,000 rpm to 5,000 rpm and will hold (or slowly decline through engine braking) at 5,000 rpm when you come off the clutch.

The idea being to avoid any engine braking (or acceleration by over revving) during the gear change.

Edited by youngsyr on Thursday 30th July 09:46

[Toltec]

You can hold the revs, it was pointed out to me a few years ago as an advanced technique when you were looking to maximise the smoothness of your drive. A blip works well for performance driving and where you are braking/slowing past the point of the change. If you are doing a block change once you have dropped to the speed you want then a using a steady matched throttle can work really well.

It is much harder than a blip, at least I find it is, I think it is worth practising just because it helps develop sensitivity and control of the throttle. Beyond that it can provide a vary smooth ride for your passengers if that is important to you and can be of use when driving in snowy/icy conditions as it damps out weight shifts and torque changes.

Edit - Given the posts above, when I say 'hold the revs' I mean hold the rpm that will match the gear gear speed as you lift the clutch, i.e. higher than before you dipped the clutch.

Edited by Toltec on Thursday 30th July 09:50

[Sconch]

RB Will said:

Sconch said:

OK. I've looked long and hard on the internet for the answer to this but I can't find it.

What exactly is the purpose of blipping the throttle on a downchange?
And before you give me the textbook answer, I understand why you want to match engine revs to the driveshaft revs.

What I don't understand is why this is done with a "blip". Unless my interpretation is wrong, a blip is a very quick and temporary rise in engine revs. How does this help? Assuming you blip to the right revs so that when you disengage the clutch you get a nice smooth gearchange, surely you are then immediately into engine braking.

Why do you not instead hold the revs at the right point, rather than coming off the throttle again. Then you get the smooth gearchange, followed by neutral engine acceleration/braking.

I'm sure I must be missing something.

You are doing it in the wrong order.
First you disengage the clutch then you blip to bring the revs higher up to match the lower gear ration then you engage the clutch performing a nice smooth downchange.
If you kept the revs where they were they would not be right for the next gear and you would either get a jolt as the car tries to go forwards if you change up or massive engine braking if you change down.

I always get engage and disengage mixed up!! I've edited my original post now.

[Dr Jekyll]

Altrezia said:

and surely you're breaking when down-changing anyway, so engine braking isn't the worst plan in the world?

And the Great Debate starts yet again........

[Sconch]

fatboy b said:

And how do you assess what is the correct engine RPM for the roadspeed for the gear you want? A blip will, as some point, pass through the correct rpm without actually having to know the correct rpm, and with gentle pressure on the gearstick at the same time, it will slip in nicely when the rpm is matched.

Now that's an interesting point that I've not seen made before.

I assumed that the blippers out there are all blipping to exactly the right revs. But if that's not the case then that would explain the need to blip rather than hold (and like Toltec says I'm assuming that I'm holding at the rev level for the next gear).

Edited by Sconch on Thursday 30th July 10:27

[crofty1984]

It's supposed to be a very quick thing, so no just figuring out what the revs would be then making sure you hod it at those revs.
In the BEC fury it was brake, clutch in (still braking), stamp on accelerator shooting it past the "ideal" rpm, then clutch out as the revs come back down past the ideal figure.

[monthefish]

fatboy b said:

And how do you assess what is the correct engine RPM for the roadspeed for the gear you want? A blip will, as some point, pass through the correct rpm without actually having to know the correct rpm, and with gentle pressure on the gearstick at the same time, it will slip in nicely when the rpm is matched.

What are you doing with your clutch, as you're gently pushing pressure on the gearstick waiting for the revs to pass through the correct rpm?

[Toltec]

Sconch said:

fatboy b said:

And how do you assess what is the correct engine RPM for the roadspeed for the gear you want? A blip will, as some point, pass through the correct rpm without actually having to know the correct rpm, and with gentle pressure on the gearstick at the same time, it will slip in nicely when the rpm is matched.

Now that's an interesting point that I've not seen made before.

I assumed that the blippers out there are all blipping to exactly the right revs. But if that's not the case then that would explain the need to clip rather than hold (and like Toltec says I'm assuming that I'm holding at the rev level for the next gear).

How do you know the correct speed and entry point for a bend without looking at your speedo?

Eyes, ears, kinetic sense, experience and knowledge of your vehicle.

To pull it off well is even more complex, not only are you trying to match the rpm on a vehicle that is slowly decelerating (free wheeling as you dip the clutch), but as you raise the clutch you have to apply throttle at the right rate to keep the revs matched.

On a FWD car there is little point in doing this if you are still braking, i.e. heel and toe, as you can modulate the braking torque on the front wheels using the brake pedal by easing off as you lift the clutch and regain engine braking. On a RWD car it can stop you unsettling the rear while still applying heavy/limit braking that you might not want to reduce. I suspect it could be done quickly and as a performance technique in this situation, I for one am no where near being able to do it though.

[fatboy b]

monthefish said:

fatboy b said:

And how do you assess what is the correct engine RPM for the roadspeed for the gear you want? A blip will, as some point, pass through the correct rpm without actually having to know the correct rpm, and with gentle pressure on the gearstick at the same time, it will slip in nicely when the rpm is matched.

What are you doing with your clutch, as you're gently pushing pressure on the gearstick waiting for the revs to pass through the correct rpm?

Dissengaged. But poised to engage as soon as the gear slips in.

[BOR]

Sconch said:

Why do you not instead hold the revs at the right point, rather than coming off the throttle again. Then you get the smooth gearchange, followed by neutral engine acceleration/braking.

Edited by Sconch on Thursday 30th July 09:59

If you are travelling at a constant speed, rather than on the brakes, you can indeed "hold the revs at the right point"

The technique is to simply NOT change your accelerator pedal position as you dip the clutch and move the gearstick. You need to play with the speed with which you change gear to get this to work smoothly, but when you do, downchanges are imperceptible.

[schmalex]

Oh god, I can see another willy waving thread about heel & toe-ing developing

[Accelebrate]

Altrezia said:

and surely you're breaking when down-changing anyway, so engine braking isn't the worst plan in the world?

Breaking what when down changing?

[58warren]

Oh well, can't do this anyway as my car is an auto!