How much blip?

[Evice]

x

[Qualin]

I find you can never exactly match the revs, no matter how hard you try, so I just blip the throttle and then ride the clutch in gently but quickly so the car doesn't surge forward too much or slow down too much. It just takes practice I guess.

[rsjean]

With enough time behind the wheel on the track you will RPM match pretty precisely and intuitively. Not doing so just costs speed and time (it can also be argued that it costs in parts wear too but on the track those parts are typically viewed as consumables anyway). Therefore those that do it better, perform better.

[Evice]

I do blip most of the time, especially under hard braking. My idea behind is, not only speed and wear-n-tear, I simply do not want a compression lock and spin out.

[bradford]

Originally Posted by Evice

I do blip most of the time, especially under hard braking. My idea behind is, not only speed and wear-n-tear, I simply do not want a compression lock and spin out.

Couldn't it be argued that the harder you're braking the less you need to blip the throttle, because the drivetrain speed is more likely to match the engine speed?

[Evice]

Originally Posted by bradford

Couldn't it be argued that the harder you're breaking the less you need to blip the throttle, because the drivetrain speed is more likely to match the engine speed?

it sounds correct, and I try to enage the clutch at the lowest speed a car is on the brakezone to save the strain on the gearbox. But it really depends which gear you are dropping to, and what speed you are at on hard braking. It is more of a pre-caution on my end since loss of time is not something I worry about yet.

[JimD]

You should need to get the rpm up on a downshift on a track because your downshift should be to a gear that puts you in the power band for exiting the corner. In other words, you should be shifting in a gear that will have your rpm up around 4,000. Once you kick in the clutch and get off the gas, the engine goes to idle speed, under 1,000 rpm. So without "blipping" the throttle the synchros in the transmission have to handle 3000 rpm difference. They will but when you let the clutch out you will get some engine braking you may not need right then. Better to get the rpm up around 4,000, shift, and let the clutch out.

Only better if you can do both braking and blipping, however. If you mess up the braking because you are concentrating too much on the blipping it could be quite a bad experience. I have been practicing but getting the rpm up around 1000 to 1500 like I need to slowing down around town but it is not the same thing as getting up aroun 3,000 to 4,000 while under really heavy braking on the track. Next autocross we will see if my around town practice helps.

Jim

[bradford]

With a 135i and all the torque available under nearly all circumstances, sometimes a downshift is not necessary. I'm always of the opinion that if you can avoid doing anything in a car, do so. Smooth is fast.

At the tracks that I generally drive at here in the Midwest, the big speed discrepancies are usually at the end of straights. In this case, with R-compound rubber and track pads, I have usually slowed enough at threshold braking that blipping the throttle isn't really even necessary, as my speed delta between the corners is sufficient to cover the difference in gear ratio.

[Alow]

Few tips I learned from the skip barber racing school.

- Double clutch downshift is not necessary for race car driving, but matching revs is. If you want to be a good racing driver, you need to blip well.

- Blipping enough to match revs changes from car to car. My BMW needs a bigger blip than my VW.

- How much do you blip? Just enough so the car does not lunge forward (over-blip) or you experience engine braking (under-blip).

Takes a lot of practice.. I am still getting it perfected..

Trying it around town helps you understand and ingrain in your brain how much blip you need for each speed difference, but your foot may be too high up than when you are at the track since there you are usually braking harder. You could try and brake late and hard in a few places here and there around town to try it out :-)

[Qualin]

I've found that sometimes, a quick accelerator jab to the floor (If I do it fast enough) is just enough to get enough of a blip that I won't overblip, but you gotta be a bit fast. Especially on a downshift from fourth to third.

It becomes much more pronounced if I do a downshift from third to second, but at that point that's getting to be a bit more ricey. I tend to ride the clutch into second gear when I'm driving on the street rather than revmatch. (Damn, it goes all the way down to 20 km/h in third and still has enough pickup to get going!)

I've found that this method works really well when I'm doing a sixth to fourth downshift when I'm coming off of a highway onto an exit ramp.

I still occasionally overblip, but at least this way I don't have to worry about not blipping enough. You can let the clutch out a bit more gently if you overblip and the car won't surge forward as much. I know that it doesn't help the clutch by doing this...

Now, I should speak.. I come from the wonderfull world of the automatic and I've only been driving stick for about two years so a lot of concepts I learned on the fly. All I know is that I have a friend of mine who drives a manual as smoothly as an automatic, so I watch him and know he's doing something right.

One thing I've learned, if you can pull off a downshift so it that feels just as smooth and seamless as an automatic transmission downshift, you're doing OK. :-)

[Evice]

I am pretty good at rev matching properly and I agree with above poster that it is still not smooth on 3rd ->2nd shifts, which I think the gearing is further apart so I have to blip a little more, like half a throttle more, which was the main reason I created this post to get some general ideas.

[bradford]

Originally Posted by Evice

I am pretty good at rev matching properly and I agree with above poster that it is still not smooth on 3rd ->2nd shifts, which I think the gearing is further apart so I have to blip a little more, like half a throttle more, which was the main reason I created this post to get some general ideas.

It's a function of deceleration and gear ratio. If you hold deceleration constant, than it's solely a function of gear ratio. Here are the ratios:

1st - 4.06:1
2nd - 2.40:1
3rd - 1.58:1
4th - 1.19:1
5th - 1.00:1
6th - 0.87:1

The closer the ratio is to the gear above it, the less you'll need to blip the throttle to match the revs. As you can see, barely any blip is needed for upper gears, and fairly drastic blips are required for lower ones. It's really a feel thing that only comes with experience though. You can practice without the brake first, just travelling in a straight line at a constant speed, shifting from gear to gear while trying not to upset the balance of the car. Once you've got that down, add in the heel/toe aspect.

Personally, I think heel/toe is a misnomer. I find the ball/side technique to be much easier. The ball of your foot goes on the brake, and you roll to the side to blip the throttle.

[ben14142001]

I was taught at racing school (Bondurant) that you should always give more of a jab than you think you should. I used to be a small blipper, but I got yelled at on the track down there. They said that each car is different, but you should generally try to give it more throttle than you think.
And yeah, heal-toeing is a misnomer. I've tried both ways depending on pedal setup, and I have always found it easier to roll.

[JimD]

I've driven a manual for >25 years and only recently tried blipping the throttle on downshifts. I currently drive two manual transmission vehicles, a 2006 Suzuki Grand Vitara (2.7L V6 with a 5 speed) and my 128i convertible. The pedals are too far apart for me to roll my foot from side to side so I don't blip the Suzuki. My foot is easily wide enough to work on the 128i so I blip it. My one autocross in the bimmer I did not like the relatively high 3 to 2nd down shifts with no added rpm. So I decided to learn how to do this. I have no plans to autocross the Suzuki so I really don't need to do this in it, I was initially trying so I didn't have to switch every time I switch vehicles (I drive both every week, sometimes I drive both the same day).

Long winded way of saying I am not skilled enough to "heel-and-toe" but I can roll from side to side.

Jim

[Evice]

I am not really sure what you mean roll to the side to blip? I am doing the conventional, ball of my right foot on brake, (so my rightfoot is tilted LEFT in a way) and use the heel of my right foot to blip at the end point of the throttle, so that with less movement, I can give gas more because of angle in the gas pedal..

[Itanius]

Originally Posted by Evice

I am not really sure what you mean roll to the side to blip? I am doing the conventional, ball of my right foot on brake, (so my rightfoot is tilted LEFT in a way) and use the heel of my right foot to blip at the end point of the throttle, so that with less movement, I can give gas more because of angle in the gas pedal..

Rolling means that you essentially use your big toe on the brake pedal and roll your foot to the right and use your pinky toe to blip the throttle.

Both methods are still "Heel-Toe", it's just user preference.

[adrean8j]

Originally Posted by bradford

With a 135i and all the torque available under nearly all circumstances, sometimes a downshift is not necessary. I'm always of the opinion that if you can avoid doing anything in a car, do so. Smooth is fast.

Same thing I have noticed at the couple of tracks I have been to. The power/torque band on these cars is so great that I can stay in 3rd/4th through most of the track.