If you don't have a pedal set with a clutch: you are aware that LFS engages the clutch for you at that time, right? If you have manual clutch, then disregard this comment.
If you don't have a pedal set with a clutch: you are aware that LFS engages the clutch for you at that time, right? If you have manual clutch, then disregard this comment.
I don´t have a dedicated pedal to clutch nor assigned it to a button, so lfs intirely manages it.
I understand you point, but in fact when i try that in lfs the revs go up as it starts gainning speed, so clutch is engaged, and when clutch is engaged by lfs i can see the gray bar on the right bottom of the screen. So engine compression, shõuld offer much more resistence to the inertia the car is gainning.
It is normal because they don't need e.c. anti-corrosion elements, but how much forced were those engines? 150hp per litre?
I mean stroke>bore. You can be sure (and you are (I'm sure)) that most diesels are longer stroke. Some petrols too.
If I have +10% losses in compression cyl. and +20% power in bang cyl. from increasing engine compression I'll buy it. (quick though: maybe that's why engines with turbo have lower comp. rato. It lowers losses and multiplies power in bang cylinder.)
I said that F1 engine is extreme example. I don;t know, maybe american 4.0 V8 200bhp and bmw m3 4.0(?) V8 420bhp is good comparision. I don;t have lift-off g-metering for both unfortunately.
The source is recycled to toiled paprer I think. Please try these steps by your own in LFS:
- reduce EngineBrakeReduction to 0%
- drive in first gear to redline.
- lift-off and look at G-meter. Over 1G for a moment.
But then you're traveling at ~140km/h (race_s) so aero drag may have deal. So change gearing of 1st gear to level in which you rich redline at 50-60km/h and do the same. Engine care less about friction and tires are rotating as engine wish to. Tires are not locked but rotatating much slower then they should and producing tire marks on the ground. That's force from tuned car.
Hehe, ingore the gearing
Ok, I'm not sure too, but if you have engine with higher compression and it have compress the mixuture by 5cm stroke and 8cm bore you have to put more power. Pretty more. There is a help, because 5cm stroke engine has shorter cranked crankshaft, so less force is needed. But is it the same too road going engine? Dunno. But for sure, gearing is changing this forces. So maybe engines do not differ so much about lift-off brake-power, but gearing do. For example F1 car have 6th gear in the same ratio (engine rmp to vehicle speed) as most road cars has 2nd. If you prepare car for racing you also change gearing to use additional revs and hp.ps. sorry for errors, I'm almost sleeping
Perhaps have a sleep and edit that, because I didn't really understand a word of it. Sorry.
alcohol across the globe 
there is a g meter in lfs??? where? how do i turn it on? how longs it been in lfs for? 
god damnit. nobody tells me nutten
god damnit. nobody tells me nuttenPressing F9 and focusing at the bottom center of the screen, our hero realizes all he ever desired was right there before him. *fade to black for commercial break*
cheers! and the reply was just oozing with oscar material
EDIT: your right i do have hero statis, 500g into a wall and still good for another lap!
EDIT: your right i do have hero statis, 500g into a wall and still good for another lap!
Nice discussion with some people claiming rather odd behaviour.
Is it too hard to understand what happens is you change gear down to early in mid corner while driving on te limit?
Well the tyres are on the limit, so they can' t handle the extra load from engine braking and car starts to slide.
On full braking, if rear wheels get locked by the engine AND the brakes, you indeed spin out. Its called gear-change error or wrong brake-balance. Changing gear in mid corner on rwd is dangerous, because only the rear-wheels are slowed down, same effect as mildly using the handbrake. But total lock? No unless the car is not moving
F1 Engine' s have adjustable engine-braking, in fact it is in lfs too. The motormanagement makes sure there is just enough fuel burned to counter the engine-brake effect or reduces it exactly as the driver wishes.
One note: my real car can certainly brake better then lousy 1g
Is it too hard to understand what happens is you change gear down to early in mid corner while driving on te limit?
Well the tyres are on the limit, so they can' t handle the extra load from engine braking and car starts to slide.
On full braking, if rear wheels get locked by the engine AND the brakes, you indeed spin out. Its called gear-change error or wrong brake-balance. Changing gear in mid corner on rwd is dangerous, because only the rear-wheels are slowed down, same effect as mildly using the handbrake. But total lock? No unless the car is not moving
F1 Engine' s have adjustable engine-braking, in fact it is in lfs too. The motormanagement makes sure there is just enough fuel burned to counter the engine-brake effect or reduces it exactly as the driver wishes.
One note: my real car can certainly brake better then lousy 1g
Gray bar visible = LFS is slipping the clutch for you. So the car is gaining momentum which at some point is enough to start turning the engine because the clutch is partially engaged (it's being slipped automatically).
Try this with manual clutch - go to a steep incline, shift to 1st, press the brakes, let the clutch go (it'll stall the engine) then let the brakes go and see if it'll roll. I just did this and it won't: with 1st gear as expected the engine won't budge.
Gray = handbrake
Blue = clutch
Good point - I never play with the bars visible so I was going by Toni's description.
So anyway - I stand on what I said: if the clutch indication is there then it means the clutch is either fully engaged or slipping and of course you'll get the car rolling.
Originally Posted by TONI_PT 
I understand you point, but in fact when i try that in lfs the revs go up as it starts gainning speed, so clutch is engaged, and when clutch is engaged by lfs i can see the gray bar on the right bottom of the screen. So engine compression, shõuld offer much more resistence to the inertia the car is gainning.
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I was saying that when it is in fact engaged in pedal (disengaged in mechanical terms) i can tell by the gray bar.
When it happens no gray bar is there, try it with a real car (keep in mind that lower cc3, lower resistance to movement-generaly speaking). In first gear in a descent let it roll until it reaches 5Km/h (ralenti achieved speed) or so, and then release your clutch pedal, youll see that it will offer much resistance to movement( even my little sister car does it and it is a 1100 cc3 fiat seiscento).
In LFS in the descent on the Aston circuit (i haven´t noticed a more angulated descent in LFS) if you try to mimetize reality it will fail miserably
.
I understand you point, but in fact when i try that in lfs the revs go up as it starts gainning speed, so clutch is engaged, and when clutch is engaged by lfs i can see the gray bar on the right bottom of the screen. So engine compression, shõuld offer much more resistence to the inertia the car is gainning.
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I was saying that when it is in fact engaged in pedal (disengaged in mechanical terms) i can tell by the gray bar.
When it happens no gray bar is there, try it with a real car (keep in mind that lower cc3, lower resistance to movement-generaly speaking). In first gear in a descent let it roll until it reaches 5Km/h (ralenti achieved speed) or so, and then release your clutch pedal, youll see that it will offer much resistance to movement( even my little sister car does it and it is a 1100 cc3 fiat seiscento).
In LFS in the descent on the Aston circuit (i haven´t noticed a more angulated descent in LFS) if you try to mimetize reality it will fail miserably
. Unless LFS models manifold vacuum, which I'm sure it does, you won't get the full engine braking effect of a real car. When I drive the FBM I use engine braking as a backup if I over shoot a corner by a couple km/h, so I assume it actualy works like it does in real life.
On gasoline engines it's actualy the intake stroke that provides braking effects. Because the engine is still firing, there's virtualy no loss on the compression stroke. Infact, the compression stroke tends to act as a spring and because of the absence of a butterfly valve on diesel engine, you don't get engine braking on them at all without special equipment.
This is a break down of how it actualy works.
The butterfly valve closses when you let off the throttle restricting air flow into the pistons, because they where previously taking in alot more air. It generates a powerful vacuum in the intake manifold, the effect of this is alot of restriction during the intake stroke, now the engine has to act as a pump, but not a pressure pump, a vacuum pump. The bigger the bore, or the smaller the idle airflow into the engine, the more engine braking occurs.
Just consider the fact that vacuum is the only thing preventing the engine from screaming its head off and blowing, its a manifold vacuum that keeps it at idle when the throttle is closed.
A good example of this is my single piston engine on my dirt bike, If I lift off in first gear, The engine drops to idle and my speed drops accordingly. If I accelerate so that the engine is spinning at 5000rpm in 2nd gear and downshift to 1st, the engine will go up to about 7000rpm or around there. but if I keep the throttle open, I will not experiance any kind of braking effect provided the throttle is open enough to alow air flow for that engine speed. I can even cut spark which would completely turn the engine into a compressor, and the only thing that would slow down the bike by a noticable amount is closing the throttle.
Engine braking on my bike is extreemly severe in first and second, its strong enough that I've slid up to the bars once because I snapped off the throttle to fast. If it where compression, I'd almost fly off the bike if I where going 7000rpm in second and the spark suddenly cut.
On gasoline engines it's actualy the intake stroke that provides braking effects. Because the engine is still firing, there's virtualy no loss on the compression stroke. Infact, the compression stroke tends to act as a spring and because of the absence of a butterfly valve on diesel engine, you don't get engine braking on them at all without special equipment.
This is a break down of how it actualy works.
The butterfly valve closses when you let off the throttle restricting air flow into the pistons, because they where previously taking in alot more air. It generates a powerful vacuum in the intake manifold, the effect of this is alot of restriction during the intake stroke, now the engine has to act as a pump, but not a pressure pump, a vacuum pump. The bigger the bore, or the smaller the idle airflow into the engine, the more engine braking occurs.
Just consider the fact that vacuum is the only thing preventing the engine from screaming its head off and blowing, its a manifold vacuum that keeps it at idle when the throttle is closed.
A good example of this is my single piston engine on my dirt bike, If I lift off in first gear, The engine drops to idle and my speed drops accordingly. If I accelerate so that the engine is spinning at 5000rpm in 2nd gear and downshift to 1st, the engine will go up to about 7000rpm or around there. but if I keep the throttle open, I will not experiance any kind of braking effect provided the throttle is open enough to alow air flow for that engine speed. I can even cut spark which would completely turn the engine into a compressor, and the only thing that would slow down the bike by a noticable amount is closing the throttle.
Engine braking on my bike is extreemly severe in first and second, its strong enough that I've slid up to the bars once because I snapped off the throttle to fast. If it where compression, I'd almost fly off the bike if I where going 7000rpm in second and the spark suddenly cut.
My english isn' good enough ti fully understand some things i read, too technical to some one that only "speaks" english on the net.
Well all diesel cars i've driven (road cars, not race), they all had a strong engine brake effect, Bmw 530d-535d-320td-740d-730d, Mercedes c220cdi-s400cdi-A170cdi, Vw 1.9Tdi 150hp, Audi, seat etc, except a fuc*ed up volvo i´ve driven...
And yes in downshifiting we can reduce the brake effect by injecting some fuel in cilinder(press gas pedal)
Well all diesel cars i've driven (road cars, not race), they all had a strong engine brake effect, Bmw 530d-535d-320td-740d-730d, Mercedes c220cdi-s400cdi-A170cdi, Vw 1.9Tdi 150hp, Audi, seat etc, except a fuc*ed up volvo i´ve driven...
And yes in downshifiting we can reduce the brake effect by injecting some fuel in cilinder(press gas pedal
)Whilst diesels don't have the throttle butterfly engine braking (work on the top of the cylinder, which is why diesels have better economy), they do still have internal friction, often more than a petrol (longer stroke), so they can still have more engine braking.
As DC pointed out, the compression of air is more like a spring, and doesn't really make much different until you get to about 10rpm, when the compression causes engines to stop just prior to compression.
As DC pointed out, the compression of air is more like a spring, and doesn't really make much different until you get to about 10rpm, when the compression causes engines to stop just prior to compression.
I'm glad people here understand compression rebound, Trying to explain that to people at my school is like talking to a brick wall.
But you are right Tristancliffe, diesels have more friction in the engine which causes a braking effect. But it is never as drastic as the vacuum braking on a gasoline engine. Which as you said, makes diesels more efficient.
Most diesel transport trucks have special devices to create an effect similar to vacuum braking. If they didn't they'd actualy have to use a different braking system so the wheel brakes didn't overheat on hills.
As for diesel cars, I'm not sure, but I think they actualy use a system to create more engine braking so people that drive gasoline cars don't have to adjust to driving a diesel. It can't be the same as on a big truck though, because they tend to be very loud unless they have a muffler. I've never been able to test it though, the only diesel I have access to is an automatic. It's a cargo van, and I'm not alowed to take the heaps of plastic off the top of the engine to check it out.
But you are right Tristancliffe, diesels have more friction in the engine which causes a braking effect. But it is never as drastic as the vacuum braking on a gasoline engine. Which as you said, makes diesels more efficient.
Most diesel transport trucks have special devices to create an effect similar to vacuum braking. If they didn't they'd actualy have to use a different braking system so the wheel brakes didn't overheat on hills.
As for diesel cars, I'm not sure, but I think they actualy use a system to create more engine braking so people that drive gasoline cars don't have to adjust to driving a diesel. It can't be the same as on a big truck though, because they tend to be very loud unless they have a muffler. I've never been able to test it though, the only diesel I have access to is an automatic. It's a cargo van, and I'm not alowed to take the heaps of plastic off the top of the engine to check it out.
Guys explain me some thing,....please 
I thought (my knowlege of cars comes from driving, talking with friends, and what i can learn with guys like you) that car decelaration came from the inehrent engine/transmission/wheels demultiplication, as well from every other aspect that makes us burn fuel to accelerate; like tyre friction, aerodinamics, rollers friction, gravity......but i thought the major force actuating here(at lower speeds <60-70 Km/h) was the engine braking.....
I understand the concept of air compression inside cilinders actuating like a spring, if offers resistance to compression, and it can help counter effect the compression forces from cilinder to cilinder, one is compressing air but other cilinder at some point might be decompressing ñot only due to the fact of how a set of cilinders interconnected work but also because air wants to decompress expecially at those temperatures.
What is entirely new to me is the fact that we can have a specific engine part that is entirely or almost solely responsible for the engine braking.
I not saying that what you have written is wrong, by the contrary i ask you guys to explain it again but in a less technical language and in a more pratical terms, as i´m not english and i didin´t fully understood it.
I also though that in trucks used water cooled brakes due to vehicle mass, type of brakes, and the gear box they use with lots and lots of gears....I though the course of the engine and the compression rate where the cause...
I thought (my knowlege of cars comes from driving, talking with friends, and what i can learn with guys like you) that car decelaration came from the inehrent engine/transmission/wheels demultiplication, as well from every other aspect that makes us burn fuel to accelerate; like tyre friction, aerodinamics, rollers friction, gravity......but i thought the major force actuating here(at lower speeds <60-70 Km/h) was the engine braking.....
I understand the concept of air compression inside cilinders actuating like a spring, if offers resistance to compression, and it can help counter effect the compression forces from cilinder to cilinder, one is compressing air but other cilinder at some point might be decompressing ñot only due to the fact of how a set of cilinders interconnected work but also because air wants to decompress expecially at those temperatures.
What is entirely new to me is the fact that we can have a specific engine part that is entirely or almost solely responsible for the engine braking.
I not saying that what you have written is wrong, by the contrary i ask you guys to explain it again but in a less technical language and in a more pratical terms, as i´m not english and i didin´t fully understood it
.I also though that in trucks used water cooled brakes due to vehicle mass, type of brakes, and the gear box they use with lots and lots of gears....I though the course of the engine and the compression rate where the cause...
The gearing multiplication will increase the effect of engine braking, but only if the engine braking effect is strong enough. For the most part friction isn't strong enough to create a useful engine braking effect, but manifold vacuum is.
Friction in engines is mostly negated by the fact that when one piston isn't firing another one is, in an inline 4, when 3 pistons are running through a powerless cycle, 1 is providing power, so theres never a time where the engine isn't producing power, even during deceleration. This also means that compression is paired with a power stroke, so you still get more power back than you lose in a compression stroke.
On diesel engines the throttle is controled by increasing or decreasing the fuel injected into the engine, so when you release the throttle, it basicaly cuts down the fuel to what it would be if the engine was running steady at idle. This means that diesels tend to have quicker throttle off responce and less of the friction is negated because the combustion isn't at full power like it would be in a gasoline engine. So friction is higher in diesel engines, but it still isn't as high as vacuum braking.
One of the devices used to create engine braking on a diesel is a compression release brake. It works by releasing the compression before it has a chance to act as a spring, this way the high compression of the diesel engine can slow down the vehicle as if it where being slowed down by vacuum. Thats one of the devices though, there are many different ones that work differently.
Compression braking as most people hear it is created by the device I mentiond and not present on gasoline engines. you'd be suprized at how many people belive that its the engine compression slowing down there vehicle though. It seems to be a very common miss conception.
Friction in engines is mostly negated by the fact that when one piston isn't firing another one is, in an inline 4, when 3 pistons are running through a powerless cycle, 1 is providing power, so theres never a time where the engine isn't producing power, even during deceleration. This also means that compression is paired with a power stroke, so you still get more power back than you lose in a compression stroke.
On diesel engines the throttle is controled by increasing or decreasing the fuel injected into the engine, so when you release the throttle, it basicaly cuts down the fuel to what it would be if the engine was running steady at idle. This means that diesels tend to have quicker throttle off responce and less of the friction is negated because the combustion isn't at full power like it would be in a gasoline engine. So friction is higher in diesel engines, but it still isn't as high as vacuum braking.
One of the devices used to create engine braking on a diesel is a compression release brake. It works by releasing the compression before it has a chance to act as a spring, this way the high compression of the diesel engine can slow down the vehicle as if it where being slowed down by vacuum. Thats one of the devices though, there are many different ones that work differently.
Compression braking as most people hear it is created by the device I mentiond and not present on gasoline engines. you'd be suprized at how many people belive that its the engine compression slowing down there vehicle though. It seems to be a very common miss conception.
Diesel engines have NO throttle.
Which is what he said. But the varying of fuel injection is generally referred to as the throttle, as it is the diesel equivalent.
W4H - so many times you've popped into a 'technical' thread, make a pointless comment, and then run away. I know you aren't experienced with motor cars, but it is a bit silly. I think it's fair to say DC knows a little bit more than you.
W4H - so many times you've popped into a 'technical' thread, make a pointless comment, and then run away. I know you aren't experienced with motor cars, but it is a bit silly. I think it's fair to say DC knows a little bit more than you.
Thanks DragonCommando and tristancliffe 
"It works by releasing the compression before it has a chance to act as a spring" Makes sense...
Another question if i may....Is the manifold vaccuum (petrol engines) responsible for the extra force added to the braking system (in portuguese it is called a servo-freio)? The device wich help us in multiplying the pressure in the braking circuit...
Thanks guys
"It works by releasing the compression before it has a chance to act as a spring" Makes sense...
Another question if i may....Is the manifold vaccuum (petrol engines) responsible for the extra force added to the braking system (in portuguese it is called a servo-freio)? The device wich help us in multiplying the pressure in the braking circuit...
Thanks guys
Manifold vacuum is used to run alot of different things on your car, the brake booster is one of them.
On diesel engines, they either have a vacuum pump to run the brake booster and everything else running on vacuum, or they have some other way of providing power for those devices.
On diesel engines, they either have a vacuum pump to run the brake booster and everything else running on vacuum, or they have some other way of providing power for those devices.
Yes it´s that...didn´t have a clue on that, servo-brake booster, "freio" in ancient portuguese means "travão" also in portuguese, wich means brakes in english.
Engine compression
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