come on guys, post something usefull.
Scipy has made good posts with a valid argument and Ive been enjoying this thread up till now, everyones got an opinion, and I don't think it matters if its right or wrong as long as it makes for a good disscusion.
Scipy is obviously intelligent and knows about the things he's saying, so just because he adds some attitude dosn't make his points less valid.
The wiki link is more about trucks using engine compression braking when going down steep hills, this is not quite the same as a racing vehicle braking near or on the grip limit, but great reading none the less.
Maybe its just somthing that some people will do and others wont like trailbraking
Yea, I didn't see anything wrong with Scipy either, he just had a different opinion.. And I most of all. Know what being singled out because of your own opinion feels like
Lets take a F1 car, with thousands of rpm. isn`t more safe to motorbrake such an angine. And definately fatal with a high torque engine, as a diesel engine !?
There is more to move in a diesel engine, than in a f1 engine, when you motorbrake hard
I know this is totally off-topic, but the thread seems to have derailed already anyway so...
I'm curious, what motorbike is that? And what engine? 'Cause 20 km/h seems pretty low for a motorbike to redline at in 1st gear (or any gear for that matter) Unless it's like a 50cc engine or something.
It's also the energy consumed by all the movement of air below the pistons. Above the piston, the energy used up by compressing the air is mostly returned when as the air pushes back on the piston on it's way down. Above the piston, the air acts as a spring with very little energy consumption.
However, below the piston, in the crankcase, there's not a lot of change in pressure, just movement of air between the cylinders, and this consumes a lot of energy. At higher rpms, it's this movement of air, and not engine friction, that is the dominate factor in engine braking. In the case of pro stock drag racing motorcycles (and possibly other drag racing vehicles), a vacuum pump is used to evacuate the crankcase to eliminate this loss of energy from below the pistons.
Unless the engine is disconnected from the driven wheels, via a clutch or the tranny in neutral, there will be engine braking whenever the driver / player lifts on the throttle (assuming the vehicle is moving at a reasonable speed). I've experienced lift throttle induced oversteer in a Caterham without downshifting. For some racing vehicles (cars and motorcycles), the maximum amount of engine braking is limited via a slipper clutch. Regarding racing sims, engine braking is used quite a bit in Grand Prix Legends, and the differential sensitivity is adjustable via the "coast" ramp angles.
imo the reason you see engine braking so much in LFS is that you can't feel anything through the brake pedal so it does enable more consistent braking for that reason alone in real life you don't have that problem so braking at the limit is much easier to achieve
In a car like BF1 the "braking" you notice while lifting off is just a side effect from the massive downforce a formula car generates. I think if there is downforce, there must be drag too (if we are not talking about ground effect which is banned nowadays).
Are you saying that it helps if you want do drift with the back end? Usually my problem isn't how to get the back end out, but how to keep control of it.
According to my experiences:
When you may find useful to use downshift+braking (engine brake -EB) is;
*High speed cornering: EB & brakes helps the car slow down while you enter the curve (or just before),
EB mostly acts like a "dampener/damper" and with help of EB you can take the curve more smoothly.
Because rear wheels are close the locking limit, applied EB keep wheels just below the locking threshold.
It is the engine internal compression that slows down the car.
Since I assume that we are talking about Internal Combustion engines, these engines always generate
internal forces against its spin. To clear this, it’s helpful to searching about how internal combustion
engines works.
Eg; a 4-cylinder engine, due to the power creation occurs 4 times of working principle,
at the specific time there is always one cylinder generates the power, in other words 180-degree in 720 total degree.
Rest of the cylinders are in either compressing, exhaust or intake position. All these three phases are slowing down the engine,
they generates resistance to spinning engine. To overcome this negative issue, manufactures are using the part we called
“volan”, a big heavy disk attached directly to engine. Due to its mass, engine rather easily overcome these
resistance and other internal frictions (during power on conditions). When you lift off and downshift the car,
two power cycle per rev is ended and only a negligible power can be generate by the engine
(engines are generally adjusted around 800-1000 RPM to preventing the engine dead, i called it “relanti”).
So we safely call this as Engine brake. This is also related to the how fast the engine/driver shaft (tyres) is spinning.
It is not necessary using EB while high speed cornering, its depends to who is behind the wheel and better to
experience it in real life, but brake balance of your car is important here. Its not black & white,
I can say that it’s a driving style.
*On low friction surfaces: These situations are familiar most of the people I think, so there is no need to explain deeply.
Engine brake works in same way with above mentioned. It helps the car keeping in driveable situation,
if it used properly. Exaggerated use of EB cause adverse effects, ie. oversteering (RWD) or even spinning.
*In FWD cars, EB works in same way but results are sometimes different.
Generally, improper using ended with heavy understeer.
Recovering Understeer is simply lifting the gas pedal off, sometimes applying handbrake.
Recovering Oversteer is bit complicated, i use contra steering mostly,
but oversteer is more dangereous than understeer. Because of that, IRL road cars designed to understeer.
PS.Understeer/Oversteer: Once i read a funny explanation which says Understeer is
watching the the stuff you will about the crash just above the windshield wipers.
Oversteer is watching those stuffs with using rear view mirrors.
Even with no fuel, there is still the one cylinder generating power, as the compressed air generates a force against the piston on it's way down in what would be it's normal power cycle.
As previously mentioned, the compression and expansion of air doesn't consume a lot of energy. It's the friction and the movement of air within the crankcase, under the pistons, that consumes energy.
My addition here. Normally engine braking isn't used just for braking but rather to control oversteer in turns. Lift throttle induced oversteer can scrub off speed and keep a car turning inwards. Trying to trail brake in a similar situation could induce understeer, unless the braking balance was rearwards, which can be an issue if a track includes downhill braking sections.
These limit the amount of engine braking. You can tell if a racing game implements a slipper clutch by seeing if engine rpms vary depending on throttle inputs without a change in actual speed. The only racing game I'm aware of that does this is Grand Prix Legends. In real life, some race cars, most racing motorcycles, and some street motorcycles use slipper clutches.
Windage losses, I believe they are called. Can sap a LOT of power from an engine.
Making an easier path for the air to travel can help. But best is to dry sump the engine, and use the scavenge pumps to create a partial vacuum, which can free up a noticable amount of power.
Flat engines are less effected by it, but only if the cylinders are opposite - the air moves backwards and forwards between the two pistons, which takes little effort. But in an inline or a V engine, the air has to go round corners, which is harder.
Never discount windage losses. Especially in racing, where it's not usually covered in regulations and if employed could move you a long way up the grid.
sorry, i skipped most of the very long posts in here. maybe i ll read it later.
just my personal point of view on this:
i am under the impression that the car is way more stable under braking when i am moving very fast (the beginning of braking). So, when i am driving in my XRT. I use a lot of engine braking at first. by doing that, i have the brake balance turned to the back a little bit and more "brakingpower" overall. when getting slower and slower i stop that engine braking and only use my brakes, because my car would get unstable at the rear, if i continued that engine braking.
i think, it's like android said, it's possible to dynamically adjust the balance under braking. imho the perfect balance varies at each point of the track. sometimes you need to trail brake, sometimes you need just brakes that stop the car as quickly as possible.
Not agree completely on this. When you try to turn the engine by turning the crank (with a proper wrench) you can feel the resistance of the compressing piston, even crank case/carter removed. You can hear the vacuuming noise and a very strong spring like resistance caused by compression.
If you want to turn the engine easily by hand, you have to remove spark plugs.
Oil filler cap is open to crank case/carter directly. If there is too much pressure in the carter, filler cap will be pop out, and I never saw that happened. Manufacturers designed this caps as tight fitted style like some kind of cork not screwed or secured type(at least my old Mercedes and Sierra like that).
If some cylinder leaks because of the pressure rings, you will only noticed a fume or light smoke when you check to oil filler cap immediately after shutdown the engine.
But once that piston is past top dead center, it gets much easier to turn the engine, or the pressure in that piston may be enough to turn the engine on it's own.
You could remove all the spark plugs and place springs in the cylinders and you'd get essentially the same effect, and springs don't consume energy.
Yes, I agree, after Top dead center, a little relaxing should felt but its about half turn not much, because other pistons is ready to compressing at this moment (for multi-cylinder engine). Without fuel, engine never spin by turning the crank by hand few turns like this way, it will stuck at the nearest compression phase.
Squeezing/relaxing the springs needs energy. Simply putting kinetic to potential than potential to kinetic energy. At the end some energy lost by friction and movement can not continue, unless a power source is supplied necessary power.
Rubbish - you can turn engines all you like by hand.
You do lose a little bit of energy in the compression/expansion of the air, just like you do in a spring, but it's actually pretty negligable overall, but gives the [wrong] idea that it's the compression causing the engine braking.
I think he just means, it becomes HARD to turn, as the engine stiffens the crank at the nearest compresion phase... I could be wrong, I have been wrong before
After reading through this entire argument - - I decided to share my opinion.
Wheels first when talking about braking I believe. I also believe that not only doesn't the engine cause the vehicle to "brake ( slow down )", Its the other way around, but im just brain storming.
first gear has a limit to the speed it can reach before redline, all gears have different maximums. If one were to be driving in 4th gear at say...1200 revs before redline gearing down would cause the engine to be pushed forward, causing over revving and (depending on the gear ratio or given road forces to stabalise or otherwise the given car) wheel lock up. <- theory
hmm, can't i use this in racing?.
why not?
Applying the brakes while approaching a high speed corner (without the clutch) would cause the engine to slow down due to tyre friction > drive axles > differential > driveshaft etc...
the speed at which the engine decelerates would differ depending on masses of working parts i believe which may be greater or less affected by the tyres friction on the road surface (greater mass of working engine parts would mean less rpm loss and possible wheel lockup).
So I thought to myself, " what would happen if I were to add these two simple equations together to aid my digital brake (keyboard for now)" the differences (given gear + max/minumum speeds of said gears) plus the friction variables while the clutch is engaged.
Result severely cut braking distances. works for me in Live For Speed, Makes sence to me therefore I don't see why it shouldn't work in real life.
How many turns you think you can make before exhausted?
Yes, its possible to turn the 4-cyl. engines by hand but its not that easy.
But if someone try to turn an engine with cylinder head removed,
he/she can easily noticed how easy turning to engine by hand.
Engine compression is not negligible force and it is one of the reason of the engine braking
besides with other components frictions; gears, accessories etc.
Things are not black and white completely on this issue.
There is too many parts working together in the engine.
Addressing only one reason is not covering whole fact.
halo, think logically: Yes, you got several cylinders compressing, but just as many decompressing! Physically, two equal forces in opposite direction cancel each other out...
Many myths are being told over and over again, because those who wrote the articles on wiki or anywhere else thought they knew when in reality, they didn't... I rather believe two people who are studying/have studied motor engineering than umpteenth internet pages written by laymans...
Unless it's like a 50cc engine or something.
so it does enable more consistent braking for that reason alone 
