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Using the engine as a brake
(87 posts, started )
Using the engine as a brake
What is the difference between the way you use the engine to slow down with front wheel drive cars and rear wheel drive once? Also how is it different in real life compare to the game(if it is different)? In what situation should i use lower gear and brake rather then clutch and brake again for front wheel drive and read wheel drive?
Well, the major difference between FWD and RWD is of course that in a RWD car too small gear will lock the rear tires and you might spin out. It's always good to use engine braking combined with normal braking, it usually helps you slow down better. It's never good cost down with your clutch down I think, use it only to change gears.

But the problem in LFS is that the damage model is way too forgiving. You can see that very good in the FWD cars, people just slam the gear from 5th to 2nd in no time helping them to slow down a lot. Do that in real life and you would probably kill your engine or gearbox.
Quote from Blackout :
But the problem in LFS is that the damage model is way too forgiving. You can see that very good in the FWD cars, people just slam the gear from 5th to 2nd in no time helping them to slow down a lot. Do that in real life and you would probably kill your engine or gearbox.

Yeah,but thats also kills the engine in lfs,u can hear the engine is like "popping" or what.
Anyway using engine brake and brakes will make u faster,well it made me
Quote from e2mustang :Yeah,but thats also kills the engine in lfs,u can hear the engine is like "popping" or what.
Anyway using engine brake and brakes will make u faster,well it made me

Yes, but it takes some very rough shifting and time. In short sprint you wont notice it.
The WR time's in ALOT of the replays, you see them changing down the gears quite rapidly. When in real life, this would have serious re-percussionss...
Would that affect traction at the front end?
I can understand that rapid downshifting would put serious stress on the engine, gearbox and clutch. What i am really interested in is where it can have effect on traction? Especially understear or even spining the car for front wheel drive cars when in early stage of the corner?
#7 - scipy
please people. dont be stupid. lfs is a sim and u cant break the gearbox per say, but that's no reason to use it for slowing the car down, btw you're not actually using the gearbox, it's the engine friction (and not engine compressions as it's popullary belived).

what you are actually doing (if you are using the engine for braking) is hindering accurate brake modulation and balance - i.e. ur not braking properly or on the limit. IF you are braking on the limit, adding the engine friction will only cause u to lock up and lose traction - not a desired effect. the reason for rapid downshifting is the sequential gear change (u have to go trough all the gears from 6th to 2nd), if you are in your real life car, ideally u would shift maybe 2 gears down or even 3 at a time, but not like 6th to 2nd or 1st (well shifting to 1st is best done from a gear not requireing a cross-gate shift - but that's just due to gearbox design). the reason for downshifting is just so that u can be in a proper gear for the corner exist (in the ideal rpm range for max torque bla bla).

next time u use the engine for slowing the car down, remember u are beeing stupid and scipy said so. you are only upsetting the balance of the whole car and not using the brakes effectivley. btw when u downshift u better be blipping the throttle to match the engine rpm with the gearbox rpm - so the car doesnt nosedive - if you are doing that, then ask yourself why to **** would u be doing that if u wanted to use the engine for braking. i am sick and tired of stupid and ignorant people: this actually include real life car mechanics, real life race drivers, my dad, his dad, my friends, their dads, many "street races" i know and most of the sim world. i am also sick and tired of false arguments that my dad gives me: "i've been driving for almost 30 years and i've been doing it like this". <- THAT DOES NOT MEAN U ARE DOING IT RIGHT. the whole car industry prays on stupid people who are braking their engines and clutches by using them for what they have not been constructed.

p.s. i am studying to be a mechanical engineer (2nd year now)
p.s.s. engine braking can be used in snow or ice conditions to make the tire rorational speed lower then the relative speed of the car so that u can keep some kind of control over steering.

END OF DISCUSSION
Though you forget one thing: when using engine braking, you can control the brake balance dynamically. So if you set your FWD car up to be slightly unstable under full braking (brake bias a bit too much at rear), then using engine braking will nicely stabilize the car as it pulls the effective brake balance forward. With such a setup you have the choice of safe braking for normal turns by shifting down fast, and unstable braking to help turn in for hairpins by downshifting slow or not at all (till the apex).

However, that is so far the only reason to use engine braking. Brake heat/fade/wear is not modelled yet, so relieving the brakes by using more engine braking is useless. It will also not help you stop faster or brake better.
Quote from scipy :what you are actually doing (if you are using the engine for braking) is hindering accurate brake modulation and balance - i.e. ur not braking properly or on the limit.

I don't get it. What do you mean by that? How are you upsetting "accurate brake modulation" or "balance"? Balance of what? The whole point is that you want to use the engine to slow the car down, instead of using the brakes. I do that sometimes, and it seems fine. I don't know how it upsets the balance of the car, other than making it harder to steer.
Doesn't lifting off count as engine braking too? That is useful and very strong in the BF1 for example.

Part of my previous post was rubbish, I admit. But it always feels faster when you slam your gears down quickly, it just might be that it shows in the clock because better corner speed but you think it's because better braking. Still, braking would be much more interesting game with proper damage model I think.
Quote from Blackout :Doesn't lifting off count as engine braking too? That is useful and very strong in the BF1 for example.

Part of my previous post was rubbish, I admit. But it always feels faster when you slam your gears down quickly, it just might be that it shows in the clock because better corner speed but you think it's because better braking. Still, braking would be much more interesting game with proper damage model I think.

No... It's better because your brakes are set up so you can use the engine braking effect to slow down quicker... If you adjust your brakes so that full braking would mean the tires are at the limit of traction, THEN using the engine braking wouldn't be that good idea... That's what scipy was talking about...
in real life down shifting too fast without the proper rev matching will break your clutch and or parts in your gearbox, IMO it can be done if its done correctly and does help (at least in FWD) with stopping the front wheels locking (especially in low grip conditions as scipy said above) and can help (with blips) to keep the turbo spooling, not worth the mechanical risks unless your racing tho.

In LFS it seems to help alot more and you dont need to be as precise with the gas and suffer virtually no damage (depending on car) so people exploit it to gain time.

SD.

@Scipy, regarding the rant above you know in practice things dont always match therotical equasions ect, and in some vehicles and situations due to suspension movements under braking additional engine braking can have a positive effect even if its only psychological. So I guess I think your Dad could be right

SD.
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(Blackout) DELETED by Blackout
I dont know the science and I dont really care to, but I used about 80% brake and 20% engine to slow up in RL racing. And about 40% brake and 60% engine that time I ... used the run off. On that ocassion (RWD Saloon) the rears locked and I pirrouetted. I also swore.
Oh well, if we're talking real life braking technique, can i suggest, don't use a hedge, especially if you're on a bike, just a tad painful !
I hit a hedge once in a high speed push bike accident as a youngun, I think it was comparatively soft compared to the kurb . The kurb gave me a scar I still have today, the hedge however, has a scar from me
Quote from bbman :No... It's better because your brakes are set up so you can use the engine braking effect to slow down quicker... If you adjust your brakes so that full braking would mean the tires are at the limit of traction, THEN using the engine braking wouldn't be that good idea... That's what scipy was talking about...

that's right. as i've said, if you are on the limit while braking THEN engine braking is pointless. btw to comment on that part "when you lift you are engine braking" - not really, you are coasting, and yes it will slow the car down more because of the added engine friction and rotation of the gearbox parts etc - but (at least in croatia) that is not defined as engine braking.. engine braking here is to shift down a gear and slowly "drop" the clutch so that the car nosedives and slows down more obviously - and sadly it's actually MANDATORY to do it in driving schools and on the national driving license test.. so even i did it 3 times during the test (3 times is the minimum or u fail). as soon as i got to my car, heel and toe downshifts all the way.

to comment on the "upsetting the balance", if u squeeze the brakes on hard, on the G-meter circle the ball would go all the way forwards, and there it should stay until the time for turn in. now, if you are at the edge of the circle (say 1.15 G for street tires) and u use the engine braking, the wheels are gonna start locking up - doesnt mean huge lockup and slide - just locking up slightly (obviously by how much rpm u missmatched) - and that will cause the imbalance, weight is gonna shift forward, car will nosedive, there will be no weight at the rear (which can be a really bad thing if ur already at the turn in point). on the other hand, if you are braking @ 0.9 G and then add engine braking, ok... in that moment ur gonna experience maximum retardation of 1.15 G, but that only means u werent braking on the limit before.

one more thing about brake temps and taking care of them. there is no reason to use engine braking for that. IRL race cars, u pick the brake pads and the discs that can handle the temperatures. so if you are on a track with elevations and many slow corners with a lot of braking - harder and more fade resistant pads. also on a proper race car, you should read out your brake temperatures and then set the brake cooling duct to the size that will keep those temps in the optimum range (let' say not let them cool down below 350°C). once again, engine has nothing to do with it. engine is for the opposite G on the circle, the one for positive acceleration.
Quote from Becky Rose :I hit a hedge once in a high speed push bike accident as a youngun, I think it was comparatively soft compared to the kurb . The kurb gave me a scar I still have today, the hedge however, has a scar from me

You really want to compare war wounds ?. Think i might just have the edge on you on that one, unfortunately
Scipy, it IS the gearbox. To 'engine brake' you must change down the gears quite rapidly. Therefore technically, it should be called gearbox braking. You change down faster than the 'recommended' limit, locking (sometimes not)the front or rear wheels (depending on the drivetrain) of the car, slowing the car more thouroughly than on the brakes alone. To say it is simply the engine is stupid. You need to be going faster than the percieved maximum speed of the gear lower than the gear currently in use to use engine braking to it's potential (on LFS at least. you can get miles using the this technique), although even simple down changing still has an effect, just normally downchanging, try it, accelerate to 50mph in any car, then use the brakes with out changing down gears at all, then repeat the process but just normally changing down, like you would automatically.
omg. i love when people start talking about stuff that they have no clue about. do you even know what a gearbox is or what the purpose of it is? if there was not engine on the other end, your "fast downshifting" would get u nowhere. it's the ratio of the transmission (size of one gear in regeards to the other) that will in fact transmit the torque from the rotating wheels to the engine - engine not liking that, will rise in rpm but unnaturally. so you are using the wheels to rotate the engine parts. the transmission/gearbox losses are minimal. so it's engine braking. plz dont use argument fallacies, it only shows your level of knowlege. also if you read anything i wrote above you would know, IF u are braking at 100 % there is ABSOLUTLEY NO ROOM for any more speed retardation, and braking at 100 % is the only way to brake.

and about your "try braking without downshifting argument", i actually did that to prove another person who was arguing the same crap wrong. i placed cones at the ends of my braking lines in a quater mile drag race, the fastest way to stop is clutch + brake with no engine friction added, but that is not usefull in racing since you have to have the power for the exit (but it's the fastest way to bring a car to a full stop. clutch + brake - used for panic stops in real world). next fastest way of stopping was proper downshifting with blips, then it was just leaving the car in gear, and then it was engine braking with car sliding all around trying to brake loose. the differences were 1-3 m all in all, but going 3 m deeper into a corner on a race track makes the difference.

plz dont argue just for the sake of arguing, you will not prove me wrong because i think i'm right, it is because that is the factual state of things - either learn how to brake properly or live in an illusion of "engine is helping me to stop".
Hehe scipy i remember trying to explain the exact same thing to another guy on my engineering course. He just could not understand that if you are braking at 100% using the pedal there is no way you can slow down any quicker by using the engine as well.

In a perfect world with perfect tracks, drivers and cars you would never need to use engine braking, *but*, there are 2 reasons IRL why engine braking can be useful.

1) In low-grip situations (wet grass, snow, ice) when the engine is connected to the steered wheels, it can prevent lock-up (at least help keep you around the point of maximum deceleration), using just the pedal it is very easy to slide off the peak and lock the wheels - then wasting a lot of distance getting the wheels turning again so you can steer.

2) It can dynamically control the brake bias, giving more control to the (skilled) driver to keep all 4 tyres as close as possible to the maximum deceleration. At most tracks the optimum brake bias will not be the same at every corner, using engine braking you can make up for the variations.
Quote from sgb27 :2) It can dynamically control the brake bias, giving more control to the (skilled) driver to keep all 4 tyres as close as possible to the maximum deceleration. At most tracks the optimum brake bias will not be the same at every corner, using engine braking you can make up for the variations.

yea, i use it on some tracks around hairpins and such, aston national with fzr for example, the downshift from 3rd to 2nd gear is done without the pause and the rear wheels actually start to slip to some degree, making the car oversteery but just slightly and still keeping control.. but that's all in the timing and it takes some laps to get it down.. but from any other gear it's pointless (like from on braking and downshifting from 6th to 5th to 4th.. then it's just unstable).
Quote from scipy :btw you're not actually using the gearbox, it's the engine friction (and not engine compressions as it's popullary belived).

That's incorrect. Firstly, friction forces are roughly constant with respect to the speed of the surfaces in contact. So if what you said was true, the engine braking would be the same torque no matter if the engine was turning at 2000rpm or 8000rpm - obviously this is not true.

Secondly, have you ever felt how hard it is to turn an engine over with spark plugs in? Then with them removed (ie no compression)? The difference is huge, because it's the compression that makes it hard to turn over, and hence creates the engine braking.
i dont think so.. when the engine is coasting there is almost no compression beeing made, cylinders are running almost on vacuum with intake vales beeing steady and exhaust valves opening slightly. what you are using to slow down is: let's say you're on 6000 rpm in 6th gear, start braking and downshift without a throttle blip, the engine has already started to slow down - it had some kinetic energy on 6000 rpm, and that energy is going down, also taking into consideration the rotating mass of the flywheel and the clutch assembly.. when the clutch reingages it will spin that mass once again, and the thing that opposes you is friction, not compression.. because there is almost no mixture in the cylinders it's just like in idle operation, ECU recognizes that, and it will not add any gas mixture when the engine starts reving up. ofcourse some compression will occur but that will be minimal, not 12 or 13.5:1 like it usually is. so, the actuall spin up of all the moving engine parts will cause the kinetic energy from the driven wheels to be dissapated in friction and following heat..
Quote from scipy :please people. dont be stupid. lfs is a sim and u cant break the gearbox per say, but that's no reason to use it for slowing the car down, btw you're not actually using the gearbox, it's the engine friction (and not engine compressions as it's popullary belived).

what you are actually doing (if you are using the engine for braking) is hindering accurate brake modulation and balance - i.e. ur not braking properly or on the limit. IF you are braking on the limit, adding the engine friction will only cause u to lock up and lose traction - not a desired effect. the reason for rapid downshifting is the sequential gear change (u have to go trough all the gears from 6th to 2nd), if you are in your real life car, ideally u would shift maybe 2 gears down or even 3 at a time, but not like 6th to 2nd or 1st (well shifting to 1st is best done from a gear not requireing a cross-gate shift - but that's just due to gearbox design). the reason for downshifting is just so that u can be in a proper gear for the corner exist (in the ideal rpm range for max torque bla bla).

next time u use the engine for slowing the car down, remember u are beeing stupid and scipy said so. you are only upsetting the balance of the whole car and not using the brakes effectivley. btw when u downshift u better be blipping the throttle to match the engine rpm with the gearbox rpm - so the car doesnt nosedive - if you are doing that, then ask yourself why to **** would u be doing that if u wanted to use the engine for braking. i am sick and tired of stupid and ignorant people: this actually include real life car mechanics, real life race drivers, my dad, his dad, my friends, their dads, many "street races" i know and most of the sim world. i am also sick and tired of false arguments that my dad gives me: "i've been driving for almost 30 years and i've been doing it like this". <- THAT DOES NOT MEAN U ARE DOING IT RIGHT. the whole car industry prays on stupid people who are braking their engines and clutches by using them for what they have not been constructed.

p.s. i am studying to be a mechanical engineer (2nd year now)
p.s.s. engine braking can be used in snow or ice conditions to make the tire rorational speed lower then the relative speed of the car so that u can keep some kind of control over steering.

END OF DISCUSSION

good luck with the studies.
tnx, it's 4.7 GPA for now

Using the engine as a brake
(87 posts, started )
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