Quote from MadCatX :

1.05D is up. It hopefully fixes the bug I introduced somewhere after v1.05 while providing much better debugging info. Please note that the official support is still for LFS 0.6B only, test patches are supported through "runleds". Unless you're having problems with 1.05, there is no need to update.
Before reporting any issues, make sure you have debugging output enabled in the g27leds.cfg and don't forget to post the output file.

Thank you for your effort.
I'm new to this thread and I had no trouble installing this "plug". After reinitializing the axes the LEDs work pro... and the additional cfg for the LED range is a really nice thing.

Good job! Thanks!

Quote from MadCatX :

I'm no expert no the tyre and suspension physics, but there was no tyre deformation back in Q days. Since patch S the tyres actually change their shape so it's quite obvious to me that the car's motion will be strongly affected by this.

During the development of the Scirocco car it's been discovered that the current tyre models makes them too grippy, so the completely reworked tyre model is under way.

Do you feel the same level of boredom when you drive XFG with some hotlapping set from setupfield or setupgrid?

BTW, have you actually measured overall G-forces? From what I remember the Q tyres were pretty grippy too, but once you pushed them too hard they tended to loose the grip almost instantly. Patch S made this loss of grip more gradual which should make driving easier. Current WR on BL1 for XFG is 1:32.94. It was definitely possible to do 1:31 (maybe even some high 1:30) in Q...

No. Havent tried any advanced set with this newest Z28 yet. But I did use some LFS league serious racer sets with the slightly earlier Z versions.

As Forbin confirms the tyre deformation was there preety much from the start of S1 i'm sure of that too.

I havent checked the Gforces. Only the load effect on comber changes.

I agree i have noticed that tendency as well. Indeed once you loose grip in Q its for good. They definitely changed the steepnes of transition between the dynamic and static friciton and no doubt thats for better.

Quote from Forbin :

LFS has featured visual tire deformation since the early 0.1 demo releases.

Definitely try some hotlap sets and see how you feel.

In a free moment i will do that.
One good indication I think is that ever since these "easing out" changes stable sets became fast unlike before where WRs were made with really weirdly behaving sets. (with the guy using hybrid tyres in front and making Blackwood PB topping all of that totally [I was shocked seeing that replay ]) (btw. getting into a "Test run" while previewing a hotlap gets you not only to test the set but also , if you put the car flat and steady with shift+L you can look up and "steal" some susp settings. Someone before me surely noticed that already... right?)

Take care.

Quote from Forbin :

Try using the same setup on both versions. Make a set and copy it over to the other version.

IIRC, the default "Hard Track" sets changed sometime along the way.

I just tried that. I had to reenter the values from one version to the other since the fils are not back-compatible since some additional parameters changes were introduced.

First i compared the HArd track setup of Z28 and the default Hard track setup of Q:

Greatest differences between the default Hard sets in both versions are:

-much higher default braking momentum in Z28(1100Nm) and Q(960Nm)
-Desipite the wheel comber sliders are in the same positions in both versions the life preview shows some diffeerences (with driver in and fuel in in both versions and at the same tyres pressure)

Rest seems to be set exaclty the same. (including all shocks settings!)

The higher braking strenght suggests (aside from ABS introduction) that the wheels must be now simulated to have significantly higher grip

Following i compared how a Hard track set of Z28 copied into Q feels in both versions:

Z28:

-Stable and grippy. Very easy to handle
- Compared to Q the behaviour of the tyres feels much more complex. The rubber supports much less damping now (feels more realistic in this repspect to me). Also when pushed hard the front wheel tires start eqhibiting slight oscilatory behaviour as if deforming really much and foling "under" the rim preety bad. Feels real to me.
-There is next to no body roll in corners. Thats as if the car had infinitely strong sway bars installed.
-the suspension doesnt dive much when braking almost at all.

Q:

-Totally undrivable , One slide after the other
- Not enough grip . Aspecially can be felt at the back. Something indeed was wrong with the ammount of grip delivered by the tyre
-The supsension seems more flexible somehow. The shocks give up to forces much more and this creates much less stable response at high speed. This seems consequent with reality where you cant just start turning with the steering wheel left and right as much as you like at 160km/h without getting killed. In Z28 this seems totally impossible tho. Try it. You can go much too far at high speeds like this.

Then i tried to run both versions on a typical Q set stemming from the "Race S" default variant. The set incorporates really low tyre pressures and high combers. (anyone racing at the Q ver., times will know what i mean) Now that produced much more of the so needed grip.

Q
-the car sticks to the road much better now.
-low pressure in tyres can be felt in inertia in reposnse to steerng input but doesnt seem to reach disturbing levels. Tires with as high walls as the ones in XRT in reall life when pressed much definitely will be giving up a lot sideways.
-At the same time the behaviour of the tyre it self is preety "dumpy" and much less refined then in Z28.
-when powering trough the corner the car is slipping sideways much more than in Z28. It still feels preety real... I mean in the races you can see these cars trip sideways quite a bit, right?
-drive feels still more like balancing on a thin line that keeps you on track for best time. Often you may benefit from aggresive "throwing" of your car into the corner with slight oversteer and overspeed at the entry. Hard but pays if done good.

Z280

-softer tires deliver ultra grip but totally limit max speed. Somewhat stronger effect than in Q. That again could be an indication to higher grip that should be followed with higher friciton even if we talk about static friction only now.
-The car is totally easy to handle. Goes anywhere you want.
-The life combers in corners shift from -3deg to up to +5 when pushed (Blackwood Track). This shows there is much more grip and much more side force on the suspension than in Q where the max change i could ge was from -3 to +1 (on this same set, same track)
-boring? A little.
-overall racing feeling looses the "balancing on the edge" feeling and is now more about braking in time and entering the corner best with no slip at all. No need to throw the car into an oversteer prior to entering the corner since there is ebough grip anyways....

now which one is more realistic for a car of this size and weight? I'm not sure...

For sure there is an improvemen in the tires physics. No doubt about it. The car neede a lot more grip than it had back in Q. But once compared on an Q optimized set Z28 feels really
too easy handling.

Well indeed i should not have the expectations of "hard track" set to behave like a "road" set of a regular car. Still what the Z28 presents seems ovet the top to me.

Maybe indeed its just the change in tyres without any change in suspension that creates all this effect just due to more grip... ( But then again with more braking strength and more Gforces in corners the same suspension should only roll and dive even more?!)

Perhaps then new tyres could benefit from working on the kinetics of the shocks and roll bar?

I see you write that the makers aim at realism and if the real cars are boring to drive then the simulated ones should also be like that... Well that's a point. Seems like it went a bit that direction. Indeed especially now the new machines are all the best technically but totally without a spirit.

Maybe thats the answer?

Thanks for comments everyone.

Have a nice day.

Last edited by DaDriver, Thu 17 Jun 2010, 14:28.

I just run the demo version (Z28) and it felt so different with what i remembered LFS to always be (havent raced for a while) that i decided to compare it with an old Q version. Both on XRG I made a startling discovery that the old Q behaves much more interesting in terms of suspension behaviour. The new Z (and that seemed an increasing tendency over the following versions) simulates the suspension sooooooo stiff. The "mass transfer" is very vague. The XRG behaves overly stable over all. It seems like the physics model got quite disconnected with reality there...just too perfect in a way. The weight of the car cant be felt so well. The "Bump" damping of the shocks seems much too high. the springs strenght also. (even in an "Hard Track" setup the car is nowhere near reaching a roll of a regular road car ?!). Although the tires seem to have been made softer at comparable PSI which is not a bad idea since fast sets in Q had tendencies for runing really unrealistically low pressures. Second thing is the tyres heating up in Z28. Seems like the instant heat up inertia of the tires has been increased dramatically. Somehow does not seem very realistic that the temperature would rise just by 2-3deg while performing a 300m sideways slide at high speed. (About the fact that now its harder to overall overheat the tires i wont complain since i thought that in older versions they were just slightly too prone to exceeding 50 egrees Celcius)

The graphics change is nice in Z28 by comparison. Nice to see that there comes some increased FPS with it. Definitely a good work in there. Also great is (i can be wrong here dont kill me) what seems to be stronger engine braking when you take your foot off the gas pedal. Nice stabilising effect in corner entries. Cool adds to gameplay and details (selectable pitting etc.) And the breaking help in form of ABS seems quite realistic to me.

The surprising thing is that right now XFG became so easy to handle and so predictable because of that suspension chage that its not so much fun anymore really. And it doesn't feel at all more realistic. The suspension behaves more like one chop of stiff rubber rather than a heavy mass with inertia and body roll.. it just doesnt feel right.

Please dont take it as an offence. I'm sure that the makers know what they are doing. I have been racing LFS ever since early S1 every once and then and i quite never felt like this about it. Recently i heard from people who do real life racing about the IRacing and how they loved it for beeing simply more demanding in car handing than LFS. I wonder how the recent physics changes contribute to these cases... I dont see a reason why LFS should not be THE best racing simulation ever. I think the amazing tires sim it delivers is the foundation for the most rigid simulator for all types of raving vehicles. Other sims seem to fail at delivering ralism for different machine classes all at once. (Wanna bet for ex. that GTR2 could not handle a stock car behaviour at all?)

Anyone having similar thoughts about the suspension physics changes in LFS?

Fantastic tool. Thanks

Quote from AndRand :

I think that could be mistaken in this discussion.
what I found is that by advancing, not by retardation, of the ignition the engine bahaves in such way that work done by burning the fuel (d*mn, I dont even know how you call each stroke ) would be lower than energy needed to exhaust the fumes, thus it is called negative work (or other correct term in English ). And I suppose this is the phenomena standing behind your nose hit by the wheel, DaDriver

Yes you described the idea i have in mind all the time. Negative work name fits right in.

And yes you'r right. I called the process the wrong way it's indeed advancing, not retarding, my bad!

JTbo
Whoa that ignition map looks quite heavy ! 6-54 deg difference X_X wow. would like to take a ride in sth like that! In my car it works somewhere in between 30-42deg as far as i know.

What you said about the safe margin gained by retardation in case of some harder outside contitions i find very true. Usuall car manufacturers do that to make sure their cars are less unreliable and never have problems with engine swithching off by itself whem on idle, in a very wide range of conditions. For that unfortunatelly we pay a price of car behaving like a gay, heavy, full of inersion piece of metal on wheels (having my own oppion :tilt.


JTbo/Ball Bearing Turbo
Thats interesting what you say about WRC and turbos. Didn't know about it (basically not i know noything about turbo)
Good point i guess.
Still i know cars without turbo which do that...

Ball Bearing Turbo

"But I've never heard of that, and in fact most sane people try and avoid those very circumstances like the plague. "

Yes ideed the process of a the negative engine work sound quite insane. Same are motor sorts . The whole idea is old as the idea of a car is.


PS, (bit off topic)
Sanity you talk about is something we (at least a lot of people, i feel excluded tho) got used to over years. That sanity has different goals that a, lets say, real motorization fan has. They go more or less in this order: income, ecology and economy, design, reliability and handyness only then goes safety. And that last one is mostly passive (like tenths of airbags) since after a collision you need a new car. Clear deal. Maybe that's an answer why new Peugeot 307 behaves so gay within every move of the steering wheel and gas pedal prooving also that thenths of years of human ingeenering expirience mans nothing to say compared to business demands. That's sad and more and more engulfing in every aspect of our lifes..ooops sounds like i start changing topic... ehh... eghm Yeah i probably sound extreem to you people... well

Quote from Ball Bearing Turbo :

Well, since I don't have a race car of my own, I can only compare road cars - in which case the road cars in LFS seem appropriate in this area. I have never smashed my nose on the steering wheel in any car by suddenly decelerating (using only the engine) in any given gear... What kind of car do you have? I asked the first time because I am interested



Whether shifting down or not; the principle is the same and the phenomenon occurs for the same reasons. Clearly; forcing an engine to increase in revs will eat more energy than "only" using it to slow down in the current gear.



Some spark advance is necessary for efficiency on the throttle, but what you're describing is either REALLY severe spark retardation (in which case you would be firing buring fuel/air out of the exhaust valve) or slightly too much advance (I think that's what you mean by "shifting back") Usually that's called pre-ignition and would probably cause your head to lift eventually. Imagine what the cylinder pressure would be at TDC with a rapidly expanding charge that just lit off.

It appears you're also saying more fuel is burnt during that odd occurance, which makes no sense unless you're trying to lower mean effective pressure by running rich to compensate for so much advance. The whole thing sounds sketchy to me so far; perhaps you or someone else could explain it a bit better.



Yes, the engine is under vacuum with a closed throttle under deceleration. As soon as you open the throttle, the pressure will attempt to equalize as much as it can. How fast depends on the flow characteristics of the engine (volume, manifold design etc). I have a hard time thinking that any pressure above the engines normal operating pressure (for given RPM / throttle position) will occur for any measurable amount of time, especially for long enough that the ECU would pick up lean conditions (greater than approx 14:1). The XRT is a forced induction car, so even if this was true (which I'm still not convinced it is, but I'm still open to a good explanation of it) the effect would probably be nullified.



Actually, at 5000 RPM:
Since one cylinder is 500cc, and every 1/2 revolution one cylinder is on it's intake cycle, that's 1000cc per complete revolution which is 1L 5000 times per minute, assuming 100% theoretical volumetric efficiency. Of course, this doesn't happen because of pumping losses etc but we'll ignore that. So, 83.3 times per second there demand for 1L of air, that's fine. It still does not explain anything about what happens in a closed to open throttle transition; especially & specifically why there would be a notable transient of pressure above normal for given RPM & throttle position. Don't forget how much demand there is for the air; even when the throttle is opened back up. The only thing I can see happening is the vacuum decreasing to it's normal amount; hence no more fuel would need to be added to maintain your lambda.



Well, I thought you were saying this should apply to race vehicles only (since you said that IRL it was not done on road cars for efficiency reasons), but then you said you decelerate from 140k to 100k in 4 seconds in a road car. Is that into a 80km/h head wind? You said that was in 4th gear, which on most 5 speeds is a 1:1 ratio, so you could test it with a 1:1 ratio in LFS also, assuming the same differential ratio and tire size. I'm tempted to go try it, but I think I'll wait until morning just to see. Of course, drag coefficients make a big difference in this situation. I beleive the XRT is a 0.4, so you might want to keep that in mind too. Nonetheless, as Bob stated wind resistance plays a large role at higher speeds.

@Mike - octane is measured differently (not R+m/2) IIRC overseas. (RON / MON)
Mine is stock 10.5:1....

As to your first answer, really no problem. Criticism is always welcome, as i'm no exper in this stuff really and may be as well wrong.

Some tech terms i may use wrongly cause of the langage bareers.

My car is nothing sophisitcated really. A tuned BMW E21 323i (inline 6) http://img408.imageshack.us/img408/1372/bmwe21gz4.jpg
Cours as every good old car it has a carburator which is the main reaosn actually why i love the car so much (know that it sounds odd but.. :} ). Were it not for the fact that i have driven also computer controlled cars that react properly in the matter we talk about (my definition of properly is speed up when you push the gas pedal and slow down when you take it off) I'd say no computer controlled car can behave well. Cours i'd be wrong as there are cars that "know how to behave". Also usuall cars. For example all M power later products of BMW behave really good while their noon M-power versions suck on that a lot. With my lil BMW it's not advised to take your foot of the gas pedal too abruptly already when the road is wet. :} As far as i know in very light sports cars with big engines and RWD you can spin just by too sharply stepping off the pedal to the right.

The ratio is a good point. My car has a only 4 forward gears
The aerodynamics of the car... What aerodynamics ? Noone seemed to care yet at that time lol.
But don't be mistaken by that. 140km/h is not yet a speed of sound and believe me the wind can be blowing 80km/h in the back of the car but it'll also slow down the same fast. In common people having to do with older cars will get my point right a way. With computer steering comes whole set of nasty automatation modules that often stay like really whole seconds behind what we want the car to do by pressing the gas pedal, these systems (in usuall cars) hardly tell a difference if you want to speed up or slow down the first second since your decision not to say about reacting to some little things like uderpressure... However sport computer handled systems will. The main thing is that first of all throttles in the intake system are used there ( they, as someone before me nicely explained, cutt off almost whole air intake when off gas pedal). No system of air flow support then works, (in usuall cars executed by bloody small electric "step engines"[however you guys call that] that let the air flow inside the engine freely every time we step off the pedal just tu save the kinematic energy of our vehicle and thus save fuel, enviroment and not to make more noise etc. etc. BULLSHIT.)


"but what you're describing is either REALLY severe spark retardation (in which case you would be firing buring fuel/air out of the exhaust valve)"

Ever seen a WRC rally car in action? What happens before it enters a corner? Cours you see flames from the exhaust! That's exactly the sign of the ignition retardation i'm talking about (meaningn the spark is generated earlier than normally, when the exhaust valves are not yet fully closed). My car and not only my also does that (you can actually only hear that cause flames are suppressed by the quite usuall exhaust) There is nothing worng about that. Actually it's one of the signs that the engine is beeing steered properly!

The fuel is also an issue. Same engine runnig at a lower octane gas (for example using 95 unstead of 98) wont brake so much and will in all be weaker ( my car engine compression ratio is 11.7:1 if i'm not wrong btw).

The outcomes of your test indicate that your car engine braking must be stongly reduced and that is probably done on purpouse. Ever tried getting rid of the step engine and stuffing a rag in the suction pipe for the time of a test (justa as much as not to make the engine suffocate and turn off at lowest rpm)? Well i can only tell you that it does make the engine brake more properly. Not that i tried it no no no, cours not.


Im happy this interesting conversation arised.

Last edited by DaDriver, Tue 27 Mar 2007, 21:13.

Quote from Gimpster :

This is why I buy older cars with simplistic computers. No OBDII for me.

Good point! I'v noticed the same thing.

Quote from Gimpster :

I have on many occasions slid the rear tires of the XRT on approach to T1 on Blackwood due to the engine braking being more then the tires have grip to handle. Its there, its noticable but with out the seat of your pants g-forces you just can not sence it well.

I don't even want to get in to the mistakes and assumptions you make reguarding how engine braking works and how you think its adjustable.

Easy now. See people beeing quite agressive off the track as well
The example that you gave make me think you did not exacly understand my idea. I'm not talking about engine braking due to gear reduction. That of cours is noticable and works quite relisitc, but I meant engine braking abilities whenever you step off the gas pedal within the same gear. I only compare LFS car reaction to a real car ( not Punto, not Focus, not even bloody R-type or other pseudo sports puschairs openly sold to the mass) but a car that is meant to be used for racing. Had you taken your foot of the throttle too fast in such car and not prepare yourself well enough you'r nose would be in danger of beeing smashed agains the steering wheel. (example taken from life actually). XRT does not brake that strong. You say i'm beeing wrong it's adjustable? Darn than, what's that vehicle standing in my garage. An exeption? People refer engine braking to only what's happening after they switch to a lower gear, that is caused by simply the difference between the engine RPM and what the wheels trought increased cluch transmision ration are forcing it to go. The braking i meant has different reason and is applied by the change in ignition timing phase as soon as you stop pushing gas pedal (the phase of ingintion is then acutally so much shifted back that the pistons are beeing pushed back down yet before they reach their higher point) . Actually the whole process takes a bit of additional fuel (that's why "city cars" wont react like that- economy.

Quote from Ball Bearing Turbo :

What in the.....

"engine braking bar"?

"more torque following a closed throttle -> open throttle transition" .. why? Some kind of breif transient of airflow because of it's inertia lasting 1/10,000th of a second? Seems bizarre.

LFS does not model engine mounts (the actual physical component I mean, the engine orientation is of course modeled) to my knowledge, so any "stablization" due to a longitudinal engine orientation would not be noticed in LFS.... If that's what you were getting at

Giving you the benefit of the doubt for now; turn on the F9 display and observe the G meters at the bottom centre area of the screen. You will note how much engine braking there is for a given speed & given gear, and note that it's dyanmically calculated (obviously). There's a number of people in this forum with exceptional physics and vehicle dyanmics knowledge, and experience so if I was you I might not shoot my mouth off regarding physics subsequent to a post like that....

What do you race IRL?

more torque following a closed throttle -> open throttle transition- exactly. Why?.. as far as i know it's linked with the fact that sports cars air intake systems are based on a system of eghmm throttles :} (sic. the thigie that cuts off the the air) but that for sure you know. You also are aware of the fact that there is underpressure building up behind them (inside the engine) whenever the engine is braking. Now as soon as you open the throttles the air will be sucked in way faster which will cause a higher compression ratio in the cylinders for the very first moments when you want to start aceelerating. That also means you get more air to be sucked in for the first compression cycles, more air means you can melt more fuel with it.(just to keep the lambda coefficent at its best for the engine performance). This mixture is enough more explosive to be noticed in a faster and stronger car reaction. Inertia, probably adds a bit to it too. Filling in even only 1l of engine capacity (lets say two of four cilinders of our XRT 2l engine are beeing filled at a time) at 5000RPM means that 1l of air has to be sucked in 2500times per minute wich is est. 40 times a SECOND. This has to meet with air resistance. Now imagine it's decreased to almost 0 shorlty after each closed throttle -> open throttle transition, due to under pressure.

I did made use of the G-force indicators before posting and did compared the braking abilities with a real car with an enigne of same capacity and close power. XRT almost does not brake at all compare to that. (real life example. 4th gear 140km/h to 100km/h in about 4sec after just taking my foot off).

The engine orientation is indeed modeled as even after pressing F and observing the vectors of pressure of wheels against the track you can see that when agresively adding RPM when declutched the vectors react accordingly to the In line engine mount for XRT and crosswise mount for XFG due to engine torque. I may be wrong but i think i can tell already the little difference between entering a corner at 5000rpm in XRT and entering it same speed but when declutched. Still that could be felt a bit stronger.

"There's a number of people in this forum with exceptional physics and vehicle dyanmics knowledge, and experience" - you say. I'd like to meet them and have an intereting conversation. Basically that's why i wrote my suggestion. Suggesting is far from shooting ones mouth off in my understanding.

Quote from KeiichiRX7 :

I think he was suggesting an "engine brake reduction" bar, like the BF1 has, which is controlled via the electronics. basicly it applies a little throttle to keep the car from swapping ends any time you let off the gas

So it's used in other cars? (please remember my suggestion is regarding the behavour of demo version vehicles only). So i guess that wold be it, with the only diffrence that it could not only decrease but also add to engine braking ability.

Quote from Woz :

This also depends on setup as its possible to make this effect the car more/less by playing with the diff.

Yes i think i'v noticed

Quote from wheel4hummer :

LFS cars do implement Engine braking, but you wouldn't be able to tell, since the best example of this is the BF1.

Well that i find very true ... eghm. Time to get a license :}

Hi.
Respect Scawen Victor and Eric.
You seem the only people in this brunch who understand car physics. Congrats on the tires improvement, it's a really a major change. Having raced on S1 and S2 (unfortunatelly only demo as far) for some years now and beeing a driver in reality i'd have one suggestion regarding the car reaction when stepping off the gas pedal. Real race-tuned car will brake with the engine then. S2 lacks that. I understand that strong braking after taking the foot off the throttle could be a nightmare for mouse racers when going trough corners as the RWD cars would most likely loose grip of the rear wheels then. That's why i'd suggest an additonal engine-braking bar setup with which everyone could set as they find suitable(basically in real race cars that can be regulated). Engine braking is very important for the car dynamics. After engine braking, engine regains underpressure in the inake manifolds which makes it release more torque after stepping on the throttle again afterwards. Also higher engine rpm in rwd cars with the engine placed lenghtways stabilises it on the corners which is qiute hard to prove but can be easily felt when driving a real vehicle.
Pour some life in the engine reactions and the driving expirience will be even more enjoyable.
Congrats once again.
(im reeling from shock that these days someone aims not only for money and remains so devoted to the customes relasing so many good impovements)