Engine braking (good or bad)
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Pat Buckley
GT40s Supporter
IMO, engine braking was good back in the days when the brakes were marginal - it has no place in todays car.
The only reason to shift down while braking is so that you are in the corect gear when the time comes to accelerate. Blipping the throttle to match revs is done for one reason only - and that is so that you don't cause the rear tires to break traction when you down shift into the lower gear and let the clutch out....remember the rear tires will be lightly loaded under braking making this a very real possibility.
The only reason to shift down while braking is so that you are in the corect gear when the time comes to accelerate. Blipping the throttle to match revs is done for one reason only - and that is so that you don't cause the rear tires to break traction when you down shift into the lower gear and let the clutch out....remember the rear tires will be lightly loaded under braking making this a very real possibility.
Brake pads are alot cheaper than an over revved engine/valvetrain.......
I have a Road and Track DVD of an old Stirling Moss interview (late 50's) where in it he discusses driving technique. He said he never uses the gearbox/ engine to slow the car,so even back then it wasn't commonplace
Bad, pulls big end of rod out of shape, wipes out bearings. Not so likely on high quality rods but a real problem on OE rods. If you or the driver reckons the car stops quicker by using engine braking or down shifting you have got the brake balance wrong. Cure-- fix the balance & get another driver, less expensive than the new motor.
I've taught and used both methods of breaking/corner entry. There's not a one-method-fits-all for this. It's also highly dependent upon he type of car and it's chassis setup. Some chassis get too upset in the transition from pure threshold braking to throttle-on without having made the transition through some degree of dynamic compression braking.
If used, matching revs will not only help the synchronizers do their job but there will be less driveline shock in the process. Less driveline shock means less upset to the chassis etc..
Note that the type of race sprint/enduro will also require modification to driving style and methods used. Enduros are more of a balance of longevity of systems-components and performance.
If you need to use dynamic braking to win the race and the engine and driveline is not capable of taking the abuse - it's time to get a new mechanic.
Don't blame me - blame a chap name Michael Schumaker..
If used, matching revs will not only help the synchronizers do their job but there will be less driveline shock in the process. Less driveline shock means less upset to the chassis etc..
Note that the type of race sprint/enduro will also require modification to driving style and methods used. Enduros are more of a balance of longevity of systems-components and performance.
If you need to use dynamic braking to win the race and the engine and driveline is not capable of taking the abuse - it's time to get a new mechanic.
Don't blame me - blame a chap name Michael Schumaker..
As said, unlike the old days brakes are sufficient to be used for braking. No need to put the engine in peril. Just downshift while approaching turns to ensure you're in the correct gear to maintain speed, especially long sweepers and multi-apex monsters, and accelerate out of the turn.
Pat Buckley
GT40s Supporter
Randy -
I didn't realize that Shumacher used engine braking - really?
I didn't realize that Shumacher used engine braking - really?
I agree with Randy-with this clarafication- usually the engine he used for braking was fitted to another competitors car
Jac Mac
Pat Buckley
GT40s Supporter
LOL!
I can't think of a single series where the braking time is so long that engine braking even begins to become a factor.
When I instructed I never recommended engine braking.
I can't think of a single series where the braking time is so long that engine braking even begins to become a factor.
When I instructed I never recommended engine braking.
I know some people hate it and swear that you will break your engine, but I have fond memories of my father downshifting and using engine braking on his Alfa before he turned into our driveway. It's how I remember knowing that Dad was home. Now I find myself doing it because I turn into a long common driveway from a long, fast stretch of a state highway. Lets my kids know I'll be walking in the door in a couple minutes.
Yeah, OK, the metallurgists will say that 4340 doesn't like stresss reversals, and that's why you should never swap half shafts from one side of the car to the other. But really, how much reverse torque does a crankshaft see from engine braking? Maybe 5% of the torque it sees from normal acceleration?
Yeah, OK, the metallurgists will say that 4340 doesn't like stresss reversals, and that's why you should never swap half shafts from one side of the car to the other. But really, how much reverse torque does a crankshaft see from engine braking? Maybe 5% of the torque it sees from normal acceleration?
I think the potential for over revving and "bouncing " the valvetrain, if a mistimed is a major concern also.....not just the metallurgical stress issues.
Drivers using Sequential gearboxes rarely use the clutch during up/downshifts - listen and watch carefully.
Feeling only marginally compelled to defend my position -
Having been a 5 time triple champion in SCCA competition, I've found styles that work for me and I teach those styles as well as continue to use them.
In the last 10 years I've had one single engine failure (Honda) which was of my own doing by having the short-track gear in the car running at Road America (on the track record BTW).
Leading the race 6 laps from the end, the she spun two rod bearings and a main. I could have clinched the Central Division Championship during that race but because of my finishing position being next to dead last, I had to work that much harder on the last race of the year - that was 2001. It was our 3rd Central Division Championship.
Sufficient to say - As a driver, I'll use every tool available to me to win. Unlike some, I don't see other racecars as "tools".
When the race is over and you've stood on the podium - it really doesn't matter what it cost to get there..
If you're not willing to push yourself and your equipment - you'll likely never taste victory.
-edit-
I should clarify that using your equipment to it's fullest does not necessarily imply that you are abusing the same..
I'm incredibly careful to not overrev the engine on a downshift - rather I am well below the redline when selecting a gear down..
Feeling only marginally compelled to defend my position -
Having been a 5 time triple champion in SCCA competition, I've found styles that work for me and I teach those styles as well as continue to use them.
In the last 10 years I've had one single engine failure (Honda) which was of my own doing by having the short-track gear in the car running at Road America (on the track record BTW).
Leading the race 6 laps from the end, the she spun two rod bearings and a main. I could have clinched the Central Division Championship during that race but because of my finishing position being next to dead last, I had to work that much harder on the last race of the year - that was 2001. It was our 3rd Central Division Championship.
Sufficient to say - As a driver, I'll use every tool available to me to win. Unlike some, I don't see other racecars as "tools".
When the race is over and you've stood on the podium - it really doesn't matter what it cost to get there..
If you're not willing to push yourself and your equipment - you'll likely never taste victory.
-edit-
I should clarify that using your equipment to it's fullest does not necessarily imply that you are abusing the same..
I'm incredibly careful to not overrev the engine on a downshift - rather I am well below the redline when selecting a gear down..
Pat Buckley
GT40s Supporter
I held a track record at Elkhart also - in a really competitive class.
Doesn't change the fact that using engine braking as you enter a corner is only for driving on the street and having fun....not for going fast.
All in good fun.....smile.
Doesn't change the fact that using engine braking as you enter a corner is only for driving on the street and having fun....not for going fast.
All in good fun.....smile.
Ross Nicol
GT40s Supporter
Well I've been racing for the last 2 days so my cornering technique is fairly fresh in my head, I hit the brakes at my marker, then immediately prepare to change down to the correct gear for the approaching corner. I will miss out intermediate gears and for a slow tight corner shift straight to 2nd. Sandown has a back straight with a fast sweeping corner over a hill and then an over 90° corner immediately following.I brake hard before the sweeping corner and change down to 4th to drive into the next corner, where I brake hard before changing to 2nd gear for the drive out.In all cases I blip the throttle to equalize revs but most importantly I make sure the speed is down low enough so the engine is not overreved when I release the clutch.I will admit there are times when the heat of battle and red mist (call it what you like) takes over and I do nasty things to the mechanical parts, but thankfully these moments are rare.
Ross
Ross
For cruising on the road I always try to arrive at a corner at a suitable speed without having to brake or change down unless it's a hairpin bend or other fairly slow corner, so I guess that's using the engine to slow down with. And cruising I miss out some gears on the down changes and also on the upchanges.
On the track the ideal is to be either hard on the brakes or hard on the throttle. Fluffing around slowing early using the engine for minimal deceleration will see everyone else sailing past you with their boot hard up it until they get to the 'real' braking zone.
Always synchronize your revs on the down changes whether you go through them all or whether you just select the one you want for corner exit. Smoothness is the key, always. Sometimes it can be difficult to get the revs right if you're going straight from 5th to 2nd frinstance. On the track I much prefer to keep the engine revs in the ballpark by going down sequentially as the brakes slow the car, if I've got a nice shifter. Some are pigs and with them less shifts are probably better. Matter of personal preference, driving style and gearbox function.
Just my $.02
On the track the ideal is to be either hard on the brakes or hard on the throttle. Fluffing around slowing early using the engine for minimal deceleration will see everyone else sailing past you with their boot hard up it until they get to the 'real' braking zone.
Always synchronize your revs on the down changes whether you go through them all or whether you just select the one you want for corner exit. Smoothness is the key, always. Sometimes it can be difficult to get the revs right if you're going straight from 5th to 2nd frinstance. On the track I much prefer to keep the engine revs in the ballpark by going down sequentially as the brakes slow the car, if I've got a nice shifter. Some are pigs and with them less shifts are probably better. Matter of personal preference, driving style and gearbox function.
Just my $.02
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What about slipper clutches for cars? All modern Superbikes have them. Of course we have independent front and rear braking systems also. Slipper clutches make downshift rev matching a whole lot less critical, takes the torque variable out of the chassis and suspension. Some guys use the rear brake to back the bike in, others use a slow feed of the clutch lever to cause enough rear wheel braking to get the bike backed in.
Seems this technique could be used in a car - balance the brake system - but when you needed to get the car to pivot a little quicker or sooner let the clutch drag on the way to the apex. Instant and controlable oversteer. Of course this only works when you are on the limit of adhesion while braking/turning.
Seems this technique could be used in a car - balance the brake system - but when you needed to get the car to pivot a little quicker or sooner let the clutch drag on the way to the apex. Instant and controlable oversteer. Of course this only works when you are on the limit of adhesion while braking/turning.
That sounds pretty serious stuff Mesa.
But on a serious car you don't use the clutch at all, except for off the line. And in a less serious application.... well, why bother?
But on a serious car you don't use the clutch at all, except for off the line. And in a less serious application.... well, why bother?
Jack Houpe
GT40s Supporter
I have been on many tracks and I will say that on small displacement low compression engines (my 2 liter V8 twin turbo 7-1 compression) that are high revers it does have a purpose as to keep in the power band on acceleration out of corner and help braking in a corner. Now as for a 427 with 10 to 1 you might end up swapping rear to front if your not careful. I might down shift coming to a stop sign to get the view of some long legged woman but only at lower RPMs. Randy I hope to we can do that open Texas rode race someday, I could use some instruction.
For my two pennyworth, and as a senior observer in the Institute of Advanced Motorists, there are two types of engine breaking (someone will tell me there's more of course) 1. engine braking in the gear you were driving in and 2. engine braking by going down a gear(s) to force extra braking. For road use 1 is good 2 is bad. Here's the reasons. As has already been said, brakes are cheaper to replace than engines and transmissions, and these days they are much more efficient and reliable, negating the need to "save" them for when they are really needed. Engine braking naturally occurs when you lift off the throttle and can be used to slow the car before applying the brakes to stop. Modern cars can take very low speeds with the clutch engaged before labouring so if you plan the stop correctly you can almost stop under engine braking from a distance with little or no stress to any components. When driving down steep winding hills, however it is best to take a lower gear and use engine braking to keep the car in check to that the brakes can be used to assist when needed without the fear of overheating and fading. One of the things we do as advanced drivers is see how well you can drive in all traffic conditions without using the brakes but also without using excessive engine braking. It is amazing how much concentration and forward planning you need to do this, but the results are quite spectacular in respect of mpg, brake pad longevity and progress.
As for racing rules I am not a racing driver so cannot comment.
As for racing rules I am not a racing driver so cannot comment.
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