The online racing simulator
Engine compression
(81 posts, started )
Quote from atlantian :[sarcasm]oh, yeah, i pull the handbrake to shift[/sarcasm]

Why else would you spin in the middle of a corner just by pressing the clutch ? And why are you stopping very quickly from pressing the clutch ?

It just doesn't make any sense at all if it would be the clutch you are talking about...
If, as I suggested, he was using his forehead to operate the pedals, then changes are pressing the clutch would also press the other pedals, and cause this behaviour. I can't really think how else it could be achieved. Even buttocks have enough dexterity.
Quote from tristancliffe :Even buttocks have enough dexterity.

only if youre ambuttdextrous
the average person being right handed will only have full control over the clutch pedal with a practically limp left cheek hanging over the brake and gas pedal pressing both at random
Quote from ATHome :Why else would you spin in the middle of a corner just by pressing the clutch ? And why are you stopping very quickly from pressing the clutch ?

It just doesn't make any sense at all if it would be the clutch you are talking about...

idk, i guess i just have a glitchy version... there was the shifter problem then some pedals that suddenly inverse it's axis...
Quote from tristancliffe :Except that a race engine has less ring:wall pressure and therefore has lower friction.

It also has oil with higher coeffitient of viscous, which actually lower the engine power and increase the friction. It is beacause you rather want to finish a race than have 20bhp more and watch pretty smoke from the hood after 5 laps. Well, some drag prepared cars aren't able to drive even 400m without failure
Quote from tristancliffe :Not really. It takes a fraction more energy to overcome the higher compression ratio, but not that much more. It certainly doesn't increase engine braking, because if if did NA Diesels would lock the driven wheels each time you lift off (>22:1 CR)

They surely would, matched with inverted (comparising low reving diesel with e.c. ferrari engine) bore/stroke ratio.
Quote from tristancliffe :The losses will be lower in a race car, not a road car. But the engine differences are some numerous that it's not a fair comparison anyway. But sadly the amount of output doesn't match the amount of engine braking that occurs. Some engines have no engine braking but produce LOTS of power.

Maybe turbine engines.
I think more power at full throttle is more prior for engineers than braking force at lift-off, and even if it is too high, they can reduce it somehow, if really needed.
Quote from tristancliffe :What sort of figures were they quoting for low speed engine braking decellerations (and in what gear/rpm?)? Because the 1g thing is TOTAL drag braking from about 160mph when on a trailing throttle.

Even in 1st it does that much deceleration. If you think ~130km/h takes aero drag into account so hard, change gearing that it will hit redline at 50km/h. Pretty black skidmarks at lift-off.

F1 is an extreme example, but shows that braking force can be huge, if you use high reving engine with MUCH_HP/1L.

Quote from tristancliffe :It is, and it's far more important than traction control from a spectator point of view, because you will see more cars losing it in braking zones than on corner exit.

I'm not sure now, if it was about 'throttle blip on downshift' or 'engine brake reduction', but maybe it is maneged by the same thing which is banned.
Quote from pasibrzuch :It also has oil with higher coeffitient of viscous, which actually lower the engine power and increase the friction. It is beacause you rather want to finish a race than have 20bhp more and watch pretty smoke from the hood after 5 laps. Well, some drag prepared cars aren't able to drive even 400m without failure

Hmmm, most race engines I've built or read about use a slightly runnier oil, with more anti-friction additives...
Quote :They surely would, matched with inverted (comparising low reving diesel with e.c. ferrari engine) bore/stroke ratio.

YOu mean oversquare, right? I think most diesels are longer stroke, but I'm not sure.
Quote :Maybe turbine engines.
I think more power at full throttle is more prior for engineers than braking force at lift-off, and even if it is too high, they can reduce it somehow, if really needed.

They are fairly well linked. To produce more power you lower the friction and losses in the engine. Higher output (for a given engine) = lower engine braking. Comparing a 1.3l hatchback engine to an F1 engine isn't fair. You have to compare 1.3standard with 1.3 tuned.
Quote :Even in 1st it does that much deceleration. If you think ~130km/h takes aero drag into account so hard, change gearing that it will hit redline at 50km/h. Pretty black skidmarks at lift-off.

I didn't understand that sentence. Could you quote a source for this info. The +1g lift off braking figures are for high speed conditions, not low speed conditions. Read any report on F1 braking performance and it will mention that 1g of the decelleration from high speed is caused by aero.
Quote :F1 is an extreme example, but shows that braking force can be huge, if you use high reving engine with MUCH_HP/1L.

I doubt the F1 cars have more engine braking (measured in torque at the flywheel - ignore gearing as that skews the conversation) than a 350hp 2.4 V8 road engine does, simply because that's not how engines work.


I'm not sure now, if it was about 'throttle blip on downshift' or 'engine brake reduction', but maybe it is maneged by the same thing which is banned.[/quote]
Quote from tristancliffe :Rubbish. Lift off at 8000rpm in a Saxo (do they even rev that high?) and you'll just slow down a bit. You won't lock wheels, lose control, or even slightly lock the wheels. It's just a slight decelleration, and it's pretty much right in LFS.

Try it.

Edit:
1.6 (1587 cc) VTS - DOHC (Double overhead camshaft) 16 valve - 120 bhp/6600+-- 145 Nm/5600+- - 0-60 in 7.2 seconds - top speed = 127 mph 206 Km/h



MAN NO COMMENTS i own one, and yes it almost reaches 8000 rpm, 7750 altough in redline, and yes it almost locks wheels, want a video?
Quote from TONI_PT :Edit:
1.6 (1587 cc) VTS - DOHC (Double overhead camshaft) 16 valve - 120 bhp/6600+-- 145 Nm/5600+- - 0-60 in 7.2 seconds - top speed = 127 mph 206 Km/h



MAN NO COMMENTS i own one, and yes it almost reaches 8000 rpm, 7750 altough in redline, and yes it almost locks wheels, want a video?

damn,do you shift back at 7000 rpm? i can see it locks but with just a gas lift off? thats srtange. i've never seen it in any of my fwd cars i had.
i drive an 08 vw golf (170hp 177lb-ft 2.5L), and i have to agree with tony. when you lift off
abruptly while doing max revs in first gear your car will decelerate pretty violently. you don't even have to do max revs to notice it.
Quote from TONI_PT :Edit:
1.6 (1587 cc) VTS - DOHC (Double overhead camshaft) 16 valve - 120 bhp/6600+-- 145 Nm/5600+- - 0-60 in 7.2 seconds - top speed = 127 mph 206 Km/h



MAN NO COMMENTS i own one, and yes it almost reaches 8000 rpm, 7750 altough in redline, and yes it almost locks wheels, want a video?

I don't think you needed to post so many useless facts about your hatchback. And what you did write suggests that there isn't any need whatsoever to rev past about 7000rpm EVER.

But if you would like to make a video I'd love it. Can you get a g-meter in the car too. I find it hard to believe (having driven a friend's VTS a few years back) that it will be anywhere near locking the wheels.
Quote from e2mustang :damn,do you shift back at 7000 rpm? i can see it locks but with just a gas lift off? thats srtange. i've never seen it in any of my fwd cars i had.

Yes i shift UP at more than 7000 with this car and at more with others that achieve it...But i was talking about lifting gas completely in max revs in low gears...and it almost lock, almost, not full lock (first gear)...And this was only to compare real/LFS

tristancliffe you are implicative, the reason i posted that info was cause you didn't know a saxo could reach such revs, and more much more :-)....your name in my language means sad....
why on earth would you rev up to 7k revs and then lift off in first gear??

of course there is going to be engine braking in 1st gear..not hard to work out why really...
Quote from pug205 :why on earth would you rev up to 7k revs and then lift off in first gear??

of course there is going to be engine braking in 1st gear..not hard to work out why really...

Read topic from beggining, it is a comparison between real life engine compression versus lfs engine compression
Quote from pug205 :why on earth would you rev up to 7k revs and then lift off in first gear??...

Waste money on expensive repair....maybe.

Let's say people can blast their car's engine on purpose?...
Quote from TONI_PT :tristancliffe you are implicative, the reason i posted that info was cause you didn't know a saxo could reach such revs, and more much more :-)....your name in my language means sad....

I didn't think it could, and you confirmed that it can't. You said 8000rpm, and now you've lowered that to a sensible figure.

I couldn't give two hoots if you think I'm 'sad', the point is that you are moaning about something you are feeling, and can't provide any figures to prove or disprove it.

Hence, give us some real life g figures to compare to LFS. Then perhaps some wheel figures. If you are JUST going by seat of the pants feel then that's meaningless in LFS. How do you know the tyres are 'just' locking? Have you measure their torque capacity and torque load? Or are you just assuming they are close to locking up based on noise (which doesn't tell you a damn thing), or decellerations (which again don't tell you anything, as a Saxo is capable of (at a rough guess) 0.7g braking, so the tyres are capable of providing more force than you'd get by lifting off.

In other words, you are misinformed and unable to prove any claims. And I happen to think you are wrong based on hard driving of many cars (including a VTS).
If the wheels almost lock when you lift off the gas, and you don't touch the clutch, doesn't it imply that you almost stall the engine? How can that be?
Quote from tristancliffe :I didn't think it could, and you confirmed that it can't. You said 8000rpm, and now you've lowered that to a sensible figure....

WRONG i said almost 8000 in my first post, so ...no point there...

Also i wrote the factory data, if you don´t know cars can go past redline (petrol) some more some less, only cars that i can´t get trough redline are the diesel ones (not tricked)...

If i ofended you...i did not meant to.

I haven't said full lock, i wrote almost lock, and wet tarmac and dirty tarmac you can bet my saxo whell spin front wheels slower than rear ones if i suddently lift my gas pedal in first gear...Why i did it? TO FU**ING compare with LFS, and it's not your business how much money i spend in repairs.

My saxo (my saxo not yours, or your friends) in the last annual inspection reached 8250 revs according to the guy who operates the machine(i don´t nkow what machine is, it just sits the car there and connects some cables to exaust, car battery and intake i guess, i nkow it can also measure gases)...AND in high way and Vasco da gama bridge i my kilometers counter passes max speed written in the gauge and reaches the clock and the revs goes at 7900 -+ once again almost 8000.

Now explain the ridiculous g meter, is that what you use when you are driving to know you still have grip???? do you carry one to school or work???? well i can tell when it skids or whatever, its called driving and predicting

The factory saxo brakes in 32 meters from 100 to 0, i have different discs, pads, and tubes(cables), and when i change tyres maybe i will give it a test but in g forces i don´t know...
Quote from TONI_PT :WRONG i said almost 8000 in my first post, so ...no point there...

If you say so. That's not how I read it.
Quote from TONI_PT :Also i wrote the factory data, if you don´t know cars can go past redline (petrol) some more some less, only cars that i can´t get trough redline are the diesel ones (not tricked)...

I still doubt a Saxo's rev limiter will allow revving to 8000rpm, red line or not.

Quote from TONI_PT :If i ofended you...i did not meant to.

It takes more than an internet forum to offend me.
Quote from TONI_PT :I haven't said full lock, i wrote almost lock, and wet tarmac and dirty tarmac you can bet my saxo whell spin front wheels slower than rear ones if i suddently lift my gas pedal in first gear...Why i did it? TO FU**ING compare with LFS, and it's not your business how much money i spend in repairs.

I didn't write full lock either. But now you've changed your tune - you're comparing a wet road in reality to a dry road in LFS? Why didn't you say, as that makes a huge difference. But how do you know they are 'almost locking'? Answer this: HOW HAVE YOU MEASURED INDIVIDUAL WHEEL SPEEDS?

I've not mentioned your cost of repairs.

[quote=TONI_PT;726912]My saxo (my saxo not yours, or your friends) in the last annual inspection reached 8250 revs according to the guy who operates the machine(i don´t nkow what machine is, it just sits the car there and connects some cables to exaust, car battery and intake i guess, i nkow it can also measure gases)...AND in high way and Vasco da gama bridge i my kilometers counter passes max speed written in the gauge and reaches the clock and the revs goes at 7900 -+ once again almost 8000.
The garage will have to rev the car a bit. If your man revs it above 3000rpm NEVER EVER EVER take the car their again - he doesn't know what he's doing. Emissions tests are basically at a fast idle (actually it's more of a quick rev up, but you won't go to 8250rpm.

At high speed on the road your speedo is going to be over 20kmh fast - all speedos are! As for the revs.
[quote=TONI_PT;726912]Now explain the ridiculous g meter, is that what you use when you are driving to know you still have grip???? do you carry one to school or work???? well i can tell when it skids or whatever, its called driving and predicting

The factory saxo brakes in 32 meters from 100 to 0, i have different discs, pads, and tubes(cables), and when i change tyres maybe i will give it a test but in g forces i don´t know...[/quote]


It's a way of measuring and quantifying the acceleration of a vehicle - something that is impossible just relying on noise and feel. It doesn't tell you grip, as such, but in a straight line you can work out the peak decelleration possible, which is a guide to what the tyres can do.

Lifting off will NEVER in a road car (even a heavily modified one) cause the wheels to lock (or nearly lock). Don't forget that I also know how to drive, and have experience of more than hatchbacks.

I think you are confusing a sudden increase in revs and a chirp from the drive train (including the tyres, but it's not them 'nearly locking') with a problem. But you have no way to measure it in real life or LFS.
no
oh
Quote from TONI_PT :Don´t know if this is a bug or simply poorly simulated...

The XF GT is a 4 cilinder inline 2000 cc and it weights about 900 kgs, in the aston circuit by the descent i noticed that the brake effect from engine compression resultant of downshifting or lifting gas on high revs(well all revs) is almost non existent!!!! this as a tremendous impact on car behavior...i´ll try more cars and see if this is general or only xfgt...

In real life a prepared car with similar specs should almost lock wheels while releasing gas on max revs in first gear, and should have a tremendous brake power if done in 2 gear....

Im aware of the speed error, even so, you seem not to understand what i write or you dont remmember the gauge, the error is percentual thus increasing with speed, even so it reaches the middle of the clock, ok? and it´s not normal, my previous saxo wouldn´t reach there even in descents, nor 2 other´s i´ve driven. About the revs, i´m not sure but i think it has no error(at least not as muck as the speed gauge).

My rallenti is not steady, and my co2 values float, so i started punching the gas pedal to see if it normalized when revs went down, and the dude from the machine started showing me the revs indicated in the machine while i did it. But you are right normaly we only have to slightly accelerate till 3000 rpm depending on the car..

I don´t know how to quote more than once in one post and iam not familiarized in editing posts, so sorry for the 2 post in a row, moderators feel free to join the 3 posts, or erase previous...
I know it's a very different car, and it's rear wheel drive, but I tried this in my MX-5 last night on the way to my girlfriends. 7000rpm (slightly beyond the red line, but before the limiter) in 1st gear. Full throttle to zero throttle. The car just slowed a bit. The wheels at no point were even vaguely close to locking (partially or otherwise).

I've not tried it in other cars, as the other cars we own are a bit to expensive to drive like such a twat in 1st gear, but I would put money on them not having any problems with it either, front, rear or all wheel drive.
I´ve seen mx-5do very cool stuff, like donuts, slides, and in those round roads(i don't know how it is called in english-a circle wich join some other arteries roads) it can go completly sideways still controlable...
I believe you, some cars do it more than others, compression ratio, gear ratio, weight, etc....varies, tyre condition is very important too...

But appart all this, please get in the xf gt at aston circuit and at the descent, stop the car at the beginning and in first gear lift the brake and let it roll, and see, the car accelerates way faster than it should do, with no inercia stored and the first gear engaged the engine should resist acceleration much more, try that in your car.

In my oppinion engine compression is has small forces actuating in the cars physics, i think it should be increased.
#49 - xtm
I was going to start a new thread, but this seems to be relevant enough.
I was just having fun on my auto-x layout yesterday, and managed to turn my XRT upside down. And what I noticed seemed a bit odd, correct me if I am wrong. The friction of the drivetrain is very-very low. I did a little test, revved up the wheels to 60km/h, left the car in 2nd gear and pushed in the clutch. It took the wheels 1min20sec to slow down to 50km/h (i.e. loose 10kmh). I am no car mechanic, but intuitively I feel that free spinning wheels should expirience a little more friction, since they have to "drive" the differential, crankshaft, gearbox and part of the clutch.

I have vague memories of spinning a wheel of my grand-dads car and somehow I recall it didn't keep spinning for minutes
Let me know if you think I am wrong

I was just thinking on this thing.it is really wierd it does that.maybe your front brake calipers are siezed

Engine compression
(81 posts, started )
FGED GREDG RDFGDR GSFDG