| maaw | 08-07-2003 07:15 AM |
Left foot braking question
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I know the basic theory behind left foot braking(weight transfer), I can just never seem to do it right. Ive been to drivingtechniques.co.uk and a bunch of other places on the web to read about it but just cant seem to get the rear end to pivot around. Is there a trick to this or is it more of a dirt only thing?
Also is it dependant on setup? I just have prodrive springs and falken azenis sports 225's, no power mods yet, stock brakes.
When I try to modulate the brake pedal, with my right foot planted on the gas, the pedal seems to pump up also, if I depress the pedal maybe 3-4 times the brake doesnt respond anymore. Is this the fluid heating up and expanding(pumping). Should I change to steel lines and better fluid?
thanks in advance.
Also is it dependant on setup? I just have prodrive springs and falken azenis sports 225's, no power mods yet, stock brakes.
When I try to modulate the brake pedal, with my right foot planted on the gas, the pedal seems to pump up also, if I depress the pedal maybe 3-4 times the brake doesnt respond anymore. Is this the fluid heating up and expanding(pumping). Should I change to steel lines and better fluid?
thanks in advance.
| Kha0S | 08-07-2003 07:22 AM |
Re: Left foot braking question
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[QUOTE][i]Originally posted by maaw [/i]
[B]I know the basic theory behind left foot braking(weight transfer), I can just never seem to do it right. Ive been to drivingtechniques.co.uk and a bunch of other places on the web to read about it but just cant seem to get the rear end to pivot around. Is there a trick to this or is it more of a dirt only thing?
[/b][/quote]
As a weight transfer technique, it can be used on any surface, but for rotation, you need to have relatively low grip. Whether that's gravel, snow, wet tarmac, or terrible tires for dry tarmac, you need to have an early, progressive tire breakaway in order to get rotation.
[quote][b]
Also is it dependant on setup? I just have prodrive springs and falken azenis sports 225's, no power mods yet, stock brakes.
[/b][/quote]
You have way too much grip. Try it in an open gravel or dirt lot, or on very wet tarmac, before your tires warm up. The technique, when taught professionally, is usually learned on a skidpad first.
[quote][b]
When I try to modulate the brake pedal, with my right foot planted on the gas, the pedal seems to pump up also, if I depress the pedal maybe 3-4 times the brake doesnt respond anymore. Is this the fluid heating up and expanding(pumping). Should I change to steel lines and better fluid?
thanks in advance. [/B][/QUOTE]
That's because you're on-boost, and the vacuum assist in the brake booster is running out of vacuum with which to power your braking. There are a few hacks to fix this, and a few "correct" ways to fix it, none of which are suitable for a street car.
I would strongly reccomend visiting a real driving school where these sorts of techniques are taught (such as the Team O'Neil facility in NH, or ERS in FL, or elsewhere). There are many nuances to the technique that can only be learned from drivers who can do it in their sleep.
/Andrew
[B]I know the basic theory behind left foot braking(weight transfer), I can just never seem to do it right. Ive been to drivingtechniques.co.uk and a bunch of other places on the web to read about it but just cant seem to get the rear end to pivot around. Is there a trick to this or is it more of a dirt only thing?
[/b][/quote]
As a weight transfer technique, it can be used on any surface, but for rotation, you need to have relatively low grip. Whether that's gravel, snow, wet tarmac, or terrible tires for dry tarmac, you need to have an early, progressive tire breakaway in order to get rotation.
[quote][b]
Also is it dependant on setup? I just have prodrive springs and falken azenis sports 225's, no power mods yet, stock brakes.
[/b][/quote]
You have way too much grip. Try it in an open gravel or dirt lot, or on very wet tarmac, before your tires warm up. The technique, when taught professionally, is usually learned on a skidpad first.
[quote][b]
When I try to modulate the brake pedal, with my right foot planted on the gas, the pedal seems to pump up also, if I depress the pedal maybe 3-4 times the brake doesnt respond anymore. Is this the fluid heating up and expanding(pumping). Should I change to steel lines and better fluid?
thanks in advance. [/B][/QUOTE]
That's because you're on-boost, and the vacuum assist in the brake booster is running out of vacuum with which to power your braking. There are a few hacks to fix this, and a few "correct" ways to fix it, none of which are suitable for a street car.
I would strongly reccomend visiting a real driving school where these sorts of techniques are taught (such as the Team O'Neil facility in NH, or ERS in FL, or elsewhere). There are many nuances to the technique that can only be learned from drivers who can do it in their sleep.
/Andrew
| ITWRX4ME | 08-07-2003 10:05 AM |
The only thing I have to add to what Kha0S said is that you can get rotation on tarmac with sticky tires, it just takes more speed.
But I'm not sure LFB is the best way to get it. Most people use LFB in the middle of a corner for one of two reasons:
-- In slow speed corners where the speed mid-corner has to be maintained, but is below the ideal power band of the engine. For the WRX that's like second gear, below 3000 rpm. So the throttle is floored to keep the boost up and the brake is used to keep the speed at a cornering rate that the tires can handle. The idea being that, at the exit of the turn, the brake can be released and the engine will be ready for max power sooner.
-- In long sweepers or turn exits where the car will understeer at full throttle. Here, the brake is tapped with the left foot to balance the car and keep it pointed in the right direction, while maintaining full throttle. But here, rotation is minimal.
If you're looking to take turns on tarmac the way Tommi Makinen does, you're going to go through some tires. Also, I believe the technique the rally guys use to get the rotation is right foot braking because they're probably still down shifting. And steering plays a big part it the technique. Maybe, while they're still sideways they switch to LFB and full throttle, but only for a second.
The easiest way I've found to get the WRX to rotate is to lift the throttle mid turn or trail brake. But you have to do it when the tires are at the limit of adhesion [i]during[/i] cornering. If you're looking for more dramatic results, get a stiffer rear anti-sway bar.
Eh, I'm a noob, so what do I know.
But I'm not sure LFB is the best way to get it. Most people use LFB in the middle of a corner for one of two reasons:
-- In slow speed corners where the speed mid-corner has to be maintained, but is below the ideal power band of the engine. For the WRX that's like second gear, below 3000 rpm. So the throttle is floored to keep the boost up and the brake is used to keep the speed at a cornering rate that the tires can handle. The idea being that, at the exit of the turn, the brake can be released and the engine will be ready for max power sooner.
-- In long sweepers or turn exits where the car will understeer at full throttle. Here, the brake is tapped with the left foot to balance the car and keep it pointed in the right direction, while maintaining full throttle. But here, rotation is minimal.
If you're looking to take turns on tarmac the way Tommi Makinen does, you're going to go through some tires. Also, I believe the technique the rally guys use to get the rotation is right foot braking because they're probably still down shifting. And steering plays a big part it the technique. Maybe, while they're still sideways they switch to LFB and full throttle, but only for a second.
The easiest way I've found to get the WRX to rotate is to lift the throttle mid turn or trail brake. But you have to do it when the tires are at the limit of adhesion [i]during[/i] cornering. If you're looking for more dramatic results, get a stiffer rear anti-sway bar.
Eh, I'm a noob, so what do I know.
| Orson | 08-07-2003 10:37 AM |
Re: Left foot braking question
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[QUOTE][i]Originally posted by maaw [/i]
[B]I know the basic theory behind left foot braking(weight transfer), I can just never seem to do it right. Ive been to drivingtechniques.co.uk and a bunch of other places on the web to read about it but just cant seem to get the rear end to pivot around. Is there a trick to this or is it more of a dirt only thing?
Also is it dependant on setup? I just have prodrive springs and falken azenis sports 225's, no power mods yet, stock brakes.
When I try to modulate the brake pedal, with my right foot planted on the gas, the pedal seems to pump up also, if I depress the pedal maybe 3-4 times the brake doesnt respond anymore. Is this the fluid heating up and expanding(pumping). Should I change to steel lines and better fluid?
thanks in advance. [/B][/QUOTE]
What Kha0s said about vaccuum assist is correct. Vaccuum-assisted brake boosters work on the assumption that you do not left-foot brake. What is happening is that you are depleting the vaccuum "resevoir" in the booster and thus running out of brake assist as you modulate the brake pedal.
If your main objective is to get the rear end out, left-foot braking doesn't work as well on a Subaru as on a Honda, for example. The reason why left-foot braking works to get the rear around on a FWD car is that by applying the throttle and brake at the same time, you are effectively making the brakes rear biased (at the front, throttle+brake=very little braking; at the rear no_throttle+brake=lots of braking). But with a Subaru, you have AWD, so left foot braking only has the advantage of keeping your turbo spooled up. In fact, once you figure in the brake proportioning valve, you may be making your car understeer more!
One trick to make your rear end come around is to employ more engine braking - go into a turn in second gear screaming at 6000rpm, for example, flick the car into the turn with a little braking and the rear will come around. The trick here is that since you are employing engine braking, equal amounts of braking go to the front and rear wheels. However, since the vehicle is slowing down, the weight transfer off the rear wheels means that the rears are comparatively over-braked, hence tail-happiness.
[B]I know the basic theory behind left foot braking(weight transfer), I can just never seem to do it right. Ive been to drivingtechniques.co.uk and a bunch of other places on the web to read about it but just cant seem to get the rear end to pivot around. Is there a trick to this or is it more of a dirt only thing?
Also is it dependant on setup? I just have prodrive springs and falken azenis sports 225's, no power mods yet, stock brakes.
When I try to modulate the brake pedal, with my right foot planted on the gas, the pedal seems to pump up also, if I depress the pedal maybe 3-4 times the brake doesnt respond anymore. Is this the fluid heating up and expanding(pumping). Should I change to steel lines and better fluid?
thanks in advance. [/B][/QUOTE]
What Kha0s said about vaccuum assist is correct. Vaccuum-assisted brake boosters work on the assumption that you do not left-foot brake. What is happening is that you are depleting the vaccuum "resevoir" in the booster and thus running out of brake assist as you modulate the brake pedal.
If your main objective is to get the rear end out, left-foot braking doesn't work as well on a Subaru as on a Honda, for example. The reason why left-foot braking works to get the rear around on a FWD car is that by applying the throttle and brake at the same time, you are effectively making the brakes rear biased (at the front, throttle+brake=very little braking; at the rear no_throttle+brake=lots of braking). But with a Subaru, you have AWD, so left foot braking only has the advantage of keeping your turbo spooled up. In fact, once you figure in the brake proportioning valve, you may be making your car understeer more!
One trick to make your rear end come around is to employ more engine braking - go into a turn in second gear screaming at 6000rpm, for example, flick the car into the turn with a little braking and the rear will come around. The trick here is that since you are employing engine braking, equal amounts of braking go to the front and rear wheels. However, since the vehicle is slowing down, the weight transfer off the rear wheels means that the rears are comparatively over-braked, hence tail-happiness.
| jmott | 08-07-2003 10:50 AM |
for autocrossing/pavement purposes, left foot braking isn't "to make the car rotate"
Its simply to allow smoother transition from gas to break to gas again.
It also will allow for quick taps on the break if you screw up. But its better not to screw up.
Its simply to allow smoother transition from gas to break to gas again.
It also will allow for quick taps on the break if you screw up. But its better not to screw up.
| AUTOwrXER | 08-07-2003 11:07 AM |
I don't know about smoother transitions, but it certainly cuts down on the time it takes to get from gas to brake and back again.
| 8Complex | 08-07-2003 06:14 PM |
Use throttle lift to get the car to rotate better... just lift the throttle mid-turn, the car will most definitely oversteer on you. Be prepared though, it can and will come out a lot more then expected, a lot faster then expected, if you're not prepared.
| maaw | 08-07-2003 08:16 PM |
Ive tried lifting the throttle in mid turn, the rear end swings out a little but not enough to get a change of direction/rotation. I still have the stock sway bar but am a little hesitant to get a larger one until I know what it will do in a all situations.
If i got a 20-24mm and kept it in the middle setting, I have a vague Idea of how it would effect driving at low speeds in an autocross, but what about in a high speed situation. Will the rear end automatically slide out at speed if I let off the throttle? Just curious how stable the rear end of the car will be at speed.
Also, Ive seen drivers pivot around switchbacks in wrc on regular roads, how do they do it? It seems like the front end of their car stays planted at the apex and the rear slides around, do they have different brake bias?
thanks for all the responses.
If i got a 20-24mm and kept it in the middle setting, I have a vague Idea of how it would effect driving at low speeds in an autocross, but what about in a high speed situation. Will the rear end automatically slide out at speed if I let off the throttle? Just curious how stable the rear end of the car will be at speed.
Also, Ive seen drivers pivot around switchbacks in wrc on regular roads, how do they do it? It seems like the front end of their car stays planted at the apex and the rear slides around, do they have different brake bias?
thanks for all the responses.
| sersen | 08-07-2003 08:50 PM |
HANDBRAKE!
| STX_REX | 08-08-2003 06:06 AM |
Maaw,
Get the adj. rear sway bar. Work on left foot braking in empty parking lots late at night. Like most of these guys said, use the technique to hold speed while adding throttle early in the corner.
It allows the car to build boost earlier, and shortens the "Hello....,Hello...., is this thing on?" period often experienced while exiting slower corners in second gear. :lol:
Get the adj. rear sway bar. Work on left foot braking in empty parking lots late at night. Like most of these guys said, use the technique to hold speed while adding throttle early in the corner.
It allows the car to build boost earlier, and shortens the "Hello....,Hello...., is this thing on?" period often experienced while exiting slower corners in second gear. :lol:
| ITWRX4ME | 08-08-2003 08:17 AM |
[QUOTE][i]Originally posted by sersen [/i]
[B]HANDBRAKE! [/B][/QUOTE]
:rolleyes: bad for the drivetrain
[QUOTE][i]Originally posted by maaw [/i]
[B]Ive tried lifting the throttle in mid turn, the rear end swings out a little but not enough to get a change of direction/rotation. I still have the stock sway bar but am a little hesitant to get a larger one until I know what it will do in a all situations.
[/B][/QUOTE]
First and foremost, we have to assume that you're doing this on a closed course.
Second, and this is where it gets dicey, you're not driving the car at the limit of adhesion. So, it's reaction will not be as dramatic. In order to get lift throttle oversteer on tarmac, assuming a flat surface, you should be cornering with the tires howling. Lift abruptly and the rear will step out. If you time it right, you can press the brake as soon as the rear end breaks away. You have to do it progressively but quickly. In other words, start with just enough braking to match the deceleration and slide initiated by lifting the throttle. Then gradually press the brake harder, at a rate that keeps the fronts from losing grip while maintaining the nose diving attitude of the car. It should spin.
[QUOTE][i]Originally posted by maaw [/i]
[B]If i got a 20-24mm and kept it in the middle setting, I have a vague Idea of how it would effect driving at low speeds in an autocross, but what about in a high speed situation. Will the rear end automatically slide out at speed if I let off the throttle? Just curious how stable the rear end of the car will be at speed.
[/B][/QUOTE]
I have mine set at 24mm and it makes a big difference. Lifting at the limit of adhesion can get the car completely sideways. Not sure what you mean about "how stable the rear end...will be at speed". In a straight line it has no affect. Completely eliminates understeer when accelerating out of a corner in third gear and reduces it significantly in second gear.
[QUOTE][i]Originally posted by maaw [/i]
[B]
Also, Ive seen drivers pivot around switchbacks in wrc on regular roads, how do they do it? It seems like the front end of their car stays planted at the apex and the rear slides around, do they have different brake bias?
thanks for all the responses. [/B][/QUOTE]
It's all setup and technique. They probably do have brake proportioning valves in the cockpit. They run a very different suspension. They use copious amounts of camber in front and toe out in the rear. They use quick steering racks. Sometimes they use a special hand brake to lock up the rears (I'm guessing only for low speed turns).
But watch their technique in slow motion. Their entry speed is high. They turn in early, using the slide to scrub off speed. Their feet and hands are precise and quick.
If you're interested in this technique for autox purposes, the experienced autocrossers will tell you it's slower.
My .02 is to get the rear anti-sway bar. It's cheap and it'll balance the car nicely.
[B]HANDBRAKE! [/B][/QUOTE]
:rolleyes: bad for the drivetrain
[QUOTE][i]Originally posted by maaw [/i]
[B]Ive tried lifting the throttle in mid turn, the rear end swings out a little but not enough to get a change of direction/rotation. I still have the stock sway bar but am a little hesitant to get a larger one until I know what it will do in a all situations.
[/B][/QUOTE]
First and foremost, we have to assume that you're doing this on a closed course.
Second, and this is where it gets dicey, you're not driving the car at the limit of adhesion. So, it's reaction will not be as dramatic. In order to get lift throttle oversteer on tarmac, assuming a flat surface, you should be cornering with the tires howling. Lift abruptly and the rear will step out. If you time it right, you can press the brake as soon as the rear end breaks away. You have to do it progressively but quickly. In other words, start with just enough braking to match the deceleration and slide initiated by lifting the throttle. Then gradually press the brake harder, at a rate that keeps the fronts from losing grip while maintaining the nose diving attitude of the car. It should spin.
[QUOTE][i]Originally posted by maaw [/i]
[B]If i got a 20-24mm and kept it in the middle setting, I have a vague Idea of how it would effect driving at low speeds in an autocross, but what about in a high speed situation. Will the rear end automatically slide out at speed if I let off the throttle? Just curious how stable the rear end of the car will be at speed.
[/B][/QUOTE]
I have mine set at 24mm and it makes a big difference. Lifting at the limit of adhesion can get the car completely sideways. Not sure what you mean about "how stable the rear end...will be at speed". In a straight line it has no affect. Completely eliminates understeer when accelerating out of a corner in third gear and reduces it significantly in second gear.
[QUOTE][i]Originally posted by maaw [/i]
[B]
Also, Ive seen drivers pivot around switchbacks in wrc on regular roads, how do they do it? It seems like the front end of their car stays planted at the apex and the rear slides around, do they have different brake bias?
thanks for all the responses. [/B][/QUOTE]
It's all setup and technique. They probably do have brake proportioning valves in the cockpit. They run a very different suspension. They use copious amounts of camber in front and toe out in the rear. They use quick steering racks. Sometimes they use a special hand brake to lock up the rears (I'm guessing only for low speed turns).
But watch their technique in slow motion. Their entry speed is high. They turn in early, using the slide to scrub off speed. Their feet and hands are precise and quick.
If you're interested in this technique for autox purposes, the experienced autocrossers will tell you it's slower.
My .02 is to get the rear anti-sway bar. It's cheap and it'll balance the car nicely.
| jmott | 08-08-2003 08:52 AM |
if you are trying to go as fast as possible you don't want the rear to step out a lot
it might be fun but its not fast
[QUOTE][i]Originally posted by maaw [/i]
[B]Ive tried lifting the throttle in mid turn, the rear end swings out a little but not enough to get a change of direction/rotation. I still have the stock sway bar but am a little hesitant to get a larger one until I know what it will do in a all situations.
If i got a 20-24mm and kept it in the middle setting, I have a vague Idea of how it would effect driving at low speeds in an autocross, but what about in a high speed situation. Will the rear end automatically slide out at speed if I let off the throttle? Just curious how stable the rear end of the car will be at speed.
Also, Ive seen drivers pivot around switchbacks in wrc on regular roads, how do they do it? It seems like the front end of their car stays planted at the apex and the rear slides around, do they have different brake bias?
thanks for all the responses. [/B][/QUOTE]
it might be fun but its not fast
[QUOTE][i]Originally posted by maaw [/i]
[B]Ive tried lifting the throttle in mid turn, the rear end swings out a little but not enough to get a change of direction/rotation. I still have the stock sway bar but am a little hesitant to get a larger one until I know what it will do in a all situations.
If i got a 20-24mm and kept it in the middle setting, I have a vague Idea of how it would effect driving at low speeds in an autocross, but what about in a high speed situation. Will the rear end automatically slide out at speed if I let off the throttle? Just curious how stable the rear end of the car will be at speed.
Also, Ive seen drivers pivot around switchbacks in wrc on regular roads, how do they do it? It seems like the front end of their car stays planted at the apex and the rear slides around, do they have different brake bias?
thanks for all the responses. [/B][/QUOTE]
| GravelRash | 08-09-2003 04:43 AM |
As for the handbrake issue... The WRC cars (and others) are set up so that the hand brake disengages the center diff as well as applies the rear brakes. This keeps the two ends of the drivetrain from fighting each other - in effect turning the car into FWD momentarily, with results as described above.
There are some threads buried in the tranny (iirc) forum that discourage this idea with stock setups on cars with center diffs, e.g. WRX, and it makes sense that this would be rather hard on the center diff.
But it does make for impressive hairpins with the WRC cars :devil:
There are some threads buried in the tranny (iirc) forum that discourage this idea with stock setups on cars with center diffs, e.g. WRX, and it makes sense that this would be rather hard on the center diff.
But it does make for impressive hairpins with the WRC cars :devil:
| ANZAC_1915 | 08-09-2003 11:42 AM |
[QUOTE][i]Originally posted by jmott [/i]
[B]for autocrossing/pavement purposes, left foot braking isn't "to make the car rotate"
Its simply to allow smoother transition from gas to break to gas again.
It also will allow for quick taps on the break if you screw up. But its better not to screw up. [/B][/QUOTE]
This is called "trail braking" and there are several good autocross driving books that cover it.
[B]for autocrossing/pavement purposes, left foot braking isn't "to make the car rotate"
Its simply to allow smoother transition from gas to break to gas again.
It also will allow for quick taps on the break if you screw up. But its better not to screw up. [/B][/QUOTE]
This is called "trail braking" and there are several good autocross driving books that cover it.
| ANZAC_1915 | 08-09-2003 11:43 AM |
[QUOTE][i]Originally posted by GravelRash [/i]
[B]As for the handbrake issue... The WRC cars (and others) are set up so that the hand brake disengages the center diff as well as applies the rear brakes. This keeps the two ends of the drivetrain from fighting each other - in effect turning the car into FWD momentarily, with results as described above.
[/B][/QUOTE]
The STi DCCD has this feature too (it is mentioned in the service manual).
[B]As for the handbrake issue... The WRC cars (and others) are set up so that the hand brake disengages the center diff as well as applies the rear brakes. This keeps the two ends of the drivetrain from fighting each other - in effect turning the car into FWD momentarily, with results as described above.
[/B][/QUOTE]
The STi DCCD has this feature too (it is mentioned in the service manual).
| GravelRash | 08-12-2003 04:27 AM |
Interesting! How's it actuated? Is there an additional switch on the brake handle, a la the DRL switch?
I wonder if the owner's manual mentions it? Lessee...how would you explain what it's for w/o encouraging rampant hooliganism? :devil: :banana:
I wonder if the owner's manual mentions it? Lessee...how would you explain what it's for w/o encouraging rampant hooliganism? :devil: :banana:
| Kostamojen | 08-12-2003 04:45 AM |
I havent found a situation where left foot braking actually works with my car. Lifting the throttle does plunty for me, and depending on my tire pressure and how I have my struts set I can get the tail REALLY happy just lifting the throttle (just did it tonight on accident, LOL!) but it does help a ton with repositioning our cars for taking a better line in a corner due to how our AWD acts in a corner with a constant mild push towards the outside of the corner while we are utilizing our AWD during a corner.
| TractionCircle | 08-12-2003 09:48 AM |
I used to have the same problem where lift throttle wouldn't cause the car to oversteer any, but all that went away when I finally figured out I was just overpowering the front tires into the corner. Be a little smoother or slower into the corner so your front tires don't completely wash out and you will find lift throttle oversteer to be almost scary in these cars, especially with the rear sway bar. Once the front tires "wash out", the steering wheel just becomes a volume knob for how loud the front tires will howl :)
Hope this helps,
Jay
Hope this helps,
Jay
| codemunky | 08-13-2003 08:41 PM |
Correct me if I'm wrong, but doesn't left foot braking add oversteer? Think weight shift and grip.
| Kostamojen | 08-14-2003 02:52 AM |
[QUOTE][i]Originally posted by codemunky [/i]
[B]Correct me if I'm wrong, but doesn't left foot braking add oversteer? Think weight shift and grip. [/B][/QUOTE]
Try it and see for yourself.
[B]Correct me if I'm wrong, but doesn't left foot braking add oversteer? Think weight shift and grip. [/B][/QUOTE]
Try it and see for yourself.
| kfoote | 08-14-2003 10:36 AM |
I have not yet found a car that I have driven on the track where left foot braking does NOT help. I have driven quite a variety of cars, including ones that theoreticlly help less (like my current track car, a 99 Miata). Everywhere I don't downshift I use my left foot on the brake. I first started developing the technique driving a 1991 Ford Probe GT (lots of turbo lag) so that the car would get on power more quickly, but in the non-turbo cars I've driven (several Miatas, C5 Corvette, Porsche 944, Honda CRX, 2.5RS, 1998 Mustang GT, among others) I find there to ba a huge benefit in corner entry (trail braking), and the longer the corner, the more benefit there is. Done wrong, it can induce oversteer, but the primary result is lessening the understeer generated from having carried more speed into the corner.
The biggest down side to left foot braking is that it is a lot harder on the brakes, so when setting up and tesing a car at VIR earlier this year for an 8 hour enduro, I did not left foot brake for that reason. :confused:
The biggest down side to left foot braking is that it is a lot harder on the brakes, so when setting up and tesing a car at VIR earlier this year for an 8 hour enduro, I did not left foot brake for that reason. :confused:
| ITWRX4ME | 08-14-2003 11:18 AM |
So, in a car that has a top end of around 60 mph in second gear, you might choose third gear for a slow (say 45 - 50 mph) corner at the end of a fast straight? You left foot brake to both get on the throttle sooner and to trail brake deeper into the corner, maximizing the straightaway speed. And to set up for building speed in the next corner or two. Is that the idea?
| kfoote | 08-14-2003 11:42 AM |
Generally I won't compromise the ability to put the power down better coming out of a corner by being in a higher gear, but there are situations where if there is a question of which gear to be in (where I would have to upshift before being pointed straight) that I would be in a higher gear as long as it would gain me more on entry than it would cost on exit. The only corner that comes to mind where I have actually done that is Turn 1 using the south chicaine at NHIS, where there is a lot more gained by entering in 4th and downshifting to 3rd for turn 2A (very little distance between 1 and 2A). Where it helps the most is corners that normally require either a lift or light braking to settle the car. The best example of this that I have used is the Uphill at Lime Rock, where you are on the brakes for such a short distance that the time it takes to switch your right foot from the gas to the brake and back to the gas that you have already slowed down too much, and it costs time on the following straight. The transition from 9 to 10 at NHIS and from the last left hader to the right hander entering the esses at VIR are other examples of this.
| TexRex2002 | 08-14-2003 01:29 PM |
Why do we have to run out of vacuum?
�
�
Does anyone make a kit or anything to take vacuum from before the turbo when I'm in boost? For sure there'd be vacuum up there, don't you think?
normal driving-> vacuum assist from the intake
left foot braking, constant boost -> vacuum assist from late in the MAF hose.
Makes sense, doesn't it?
"Ice mode" sucks. It makes me feel like I'm going to bend or break the pedal...
normal driving-> vacuum assist from the intake
left foot braking, constant boost -> vacuum assist from late in the MAF hose.
Makes sense, doesn't it?
"Ice mode" sucks. It makes me feel like I'm going to bend or break the pedal...
| AWMIII | 08-14-2003 03:12 PM |
Wouldn't all this hurt your gas milage?
| LyveWRX | 08-14-2003 03:16 PM |
Usually when...
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racing gas mileage is not as much of a factor....
nick
nick
| kfoote | 08-14-2003 04:39 PM |
It does hurt your gas mileage a bit, but in any race shorter than 1 hour, it doesn't matter. The Miata is among the best race cars for fuel mileage, and I get about 12 MPG on the track. For street driving, there is absolutely no benefit to left foot braking in a manual transmission car.
| dmitrik4 | 08-15-2003 12:01 AM |
maaw-
the more low-speed oversteer you build into the car (via sway bar changes/settings, for example), the less stable the car becomes, esp at higher speeds. get the adjustable bar and play with it on course to see what works best, then switch it back to normal when you leave. that way you get the rotation you want and don't have to worry about the rear end stepping out in the rain on the highway.
[QUOTE][i]Originally posted by AWMIII [/i]
[B]Wouldn't all this hurt your gas milage? [/B][/QUOTE]
:lol:
the more low-speed oversteer you build into the car (via sway bar changes/settings, for example), the less stable the car becomes, esp at higher speeds. get the adjustable bar and play with it on course to see what works best, then switch it back to normal when you leave. that way you get the rotation you want and don't have to worry about the rear end stepping out in the rain on the highway.
[QUOTE][i]Originally posted by AWMIII [/i]
[B]Wouldn't all this hurt your gas milage? [/B][/QUOTE]
:lol:
| STX_REX | 08-15-2003 05:56 AM |
Re: Why do we have to run out of vacuum?
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[QUOTE][i]Originally posted by TexRex2002 [/i]
[B]Does anyone make a kit or anything to take vacuum from before the turbo when I'm in boost? For sure there'd be vacuum up there, don't you think?
normal driving-> vacuum assist from the intake
left foot braking, constant boost -> vacuum assist from late in the MAF hose.
Makes sense, doesn't it?
"Ice mode" sucks. It makes me feel like I'm going to bend or break the pedal... [/B][/QUOTE]
I think this is why my drivers seat squeaks so much. The first time it happened I think I nearly pushed the front seat off the tracks, I was on the pedal so hard. It feels as if its going from "Vaccum Assist" to "Boost Resist" :eek: :furious:
[B]Does anyone make a kit or anything to take vacuum from before the turbo when I'm in boost? For sure there'd be vacuum up there, don't you think?
normal driving-> vacuum assist from the intake
left foot braking, constant boost -> vacuum assist from late in the MAF hose.
Makes sense, doesn't it?
"Ice mode" sucks. It makes me feel like I'm going to bend or break the pedal... [/B][/QUOTE]
I think this is why my drivers seat squeaks so much. The first time it happened I think I nearly pushed the front seat off the tracks, I was on the pedal so hard. It feels as if its going from "Vaccum Assist" to "Boost Resist" :eek: :furious:
| GravelRash | 08-16-2003 05:23 AM |
SCC mentioned left foot braking a number of times in their various articles re their WRX. (They learned at Tim O'Neil's school.)
Their primary use was judiciously tightening their line while already in a corner. Most eye-opening example was driving up a mountain road, fully committed all wheel drift in a tight right hander (uphill side of the road), when a doofus driven mustang appeared coming down the road - halfway into the inside lane. Lfb tightened the line enough, putting the inside wheels off the road, to miss the Mustang.
Haven't had to do that yet...:lol:
Their primary use was judiciously tightening their line while already in a corner. Most eye-opening example was driving up a mountain road, fully committed all wheel drift in a tight right hander (uphill side of the road), when a doofus driven mustang appeared coming down the road - halfway into the inside lane. Lfb tightened the line enough, putting the inside wheels off the road, to miss the Mustang.
Haven't had to do that yet...:lol:
| maaw | 08-20-2003 08:24 AM |
I finally got to try it, out in the back roads they just decided to cover this road in gravel. I have no clue why as there was tarmac on it before, but it is a back road. So theres no one out there and there is a flat turn that ive driven about a billion times with plenty of run-off so I said what the hell, turned in early a bit, and started modulating the brake with my left foot. I was going maybe 40 or so, the car rotated really nicely and I got a feeling for what its like. The way ive had it explained to me before, is that you treat the car like a boat and use the brake like a rudder. Its kind of exactly like that. Its a very interesting feeling, and now I realize that I have entirely too much grip for this to work properly in anything but dirt/gravel/rain or snow.
think I'm going to have to save up a bit so I can sign up for rally school at thunderhill at the end of september.
think I'm going to have to save up a bit so I can sign up for rally school at thunderhill at the end of september.
| ITWRX4ME | 08-20-2003 09:18 AM |
Nice feeling when it works, huh?
| joshuagore | 08-21-2004 09:19 PM |
Lots of speculation here.
They use the handbrake to make thoose wonderfull turns in the wrc or most any rally. Sometimes its power or bake enduced but most of the time its tha good old fashioned EBRAKE.
They use the handbrake to make thoose wonderfull turns in the wrc or most any rally. Sometimes its power or bake enduced but most of the time its tha good old fashioned EBRAKE.
| GravelRash | 08-22-2004 06:02 AM |
...except that it's not quite the "...good old fashioned EBRAKE", as explained above.
| REX8 | 08-22-2004 03:14 PM |
An although not the fastest way around a dry track, for slippery surfaces, or just good times...we all know about the "scandinavian flick" (might have spelled that wrong). If you are entering a right hander, just before turn in, flick the wheel LEFT, get the weight on the inside tires, then quickly turn in right. Before the weight shifts back to the outside tires, you're set up in a nice balanced drift. Depending on your speed and how quick you flick the wheel, you can have anything from an all out cross yourself up mess, to a nice progressive break away, to a neutral turn with no understeer. We all know the Subarus are happier when not driven so smooth. They like to be tossed around a little....Safety First
John
John
| bemani | 08-22-2004 10:54 PM |
[QUOTE=Kha0S]
That's because you're on-boost, and the vacuum assist in the brake booster is running out of vacuum with which to power your braking. There are a few hacks to fix this, and a few "correct" ways to fix it, none of which are suitable for a street car.
[/QUOTE]
What are the various fixes? Anything that can be used temporaily on autox?
That's because you're on-boost, and the vacuum assist in the brake booster is running out of vacuum with which to power your braking. There are a few hacks to fix this, and a few "correct" ways to fix it, none of which are suitable for a street car.
[/QUOTE]
What are the various fixes? Anything that can be used temporaily on autox?
| dadswrx | 08-23-2004 08:12 AM |
[QUOTE=bemani]What are the various fixes? Anything that can be used temporaily on autox?[/QUOTE]
If you are running anything other than stock class, you [B][U]may[/U][/B] be able to add an extra vacuum cannister. This doesn't allow you to make more vacuum, but it does allow you to store more. I've probably still got the one from my E-mod Rabbit that I would let go for a reasonable price.
Mike
02 WRX Wagon
If you are running anything other than stock class, you [B][U]may[/U][/B] be able to add an extra vacuum cannister. This doesn't allow you to make more vacuum, but it does allow you to store more. I've probably still got the one from my E-mod Rabbit that I would let go for a reasonable price.
Mike
02 WRX Wagon
| bemani | 08-23-2004 12:22 PM |
How is it installed?
| makofoto | 08-23-2004 11:17 PM |
hahahaha ! Car gets best mileage if you just stay in bed .... ;-(
| leecea | 08-24-2004 09:19 AM |
I don't get how LFB while on the throttle keeps you on boost, since engine speed is directly related to ground speed assuming nothing is slipping. If I'm cornering in 2nd at 25mph, I will be at approx 2500rpm. Whether I'm at 25mph because of light throttle or full throttle and LFB, I'm still doing 25mph so I'm still at 2500rpm unless the clutch is slipping.
| trhoppe | 08-24-2004 09:56 AM |
Because the car builds boost when you are on the brakes and throttle at the same time, regardless of what RPMs you are at.
-Tom
-Tom
| mrbell | 08-24-2004 10:05 AM |
open throttle, regardless of RPM, lets more air into the engine... more air in = more exhaust out... more exhaust = more boost.
| leecea | 08-24-2004 04:16 PM |
OK. I still have a hard time with it, but I'll believe it.
| kfoote | 08-24-2004 05:49 PM |
[QUOTE=trhoppe]Because the car builds boost when you are on the brakes and throttle at the same time, regardless of what RPMs you are at.
-Tom[/QUOTE]
To show why this is, think of it this way:
In an engine, the fuel (liquid) is turned into a gas in the combustion chamber through heat and ignition. Normally, this results in force being used to push the piston down. If there is more resistance to pushing the piston down (brakes), all that extra folume of the fuel that has been turned from liquid into gas has to go out the exhaust. This results in higher exhaust pressure, meaning faster exhaust gas flow, resulting in spinning the turbocharger more quickly that it normally would at the same RPM's without the brake on.
Hope that helps explain the why.
-Tom[/QUOTE]
To show why this is, think of it this way:
In an engine, the fuel (liquid) is turned into a gas in the combustion chamber through heat and ignition. Normally, this results in force being used to push the piston down. If there is more resistance to pushing the piston down (brakes), all that extra folume of the fuel that has been turned from liquid into gas has to go out the exhaust. This results in higher exhaust pressure, meaning faster exhaust gas flow, resulting in spinning the turbocharger more quickly that it normally would at the same RPM's without the brake on.
Hope that helps explain the why.
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