Go to the drag strip. Make a run. View the replay. Use the pause button as you hit 60mph or 100kph. You can get a pretty close time that way. Maybe not perfect, but darned close.
The tools available now don't allow you to do much with the car beyond the power and weight. You can't change tire width, track, CG, etc on the car. LFS will come pretty close for basic acceleration, but not much more than that because the cars in LFS are too different from the car you are trying to model. That doesn't mean that LFS is wrong, it means that it does a good job of simulating.
Also, to get a better feel for it, google the E46 and get gear ratios and diff gearing numbers. That will help a lot. Also, because of the turbo, the torque curve is totally wrong so this will only be a very rough estimation. I understand doing it though... it is fun
I also think the weight you listed is a bit low. It should be closer to 3200lbs. My E46 323i is about 3150 without fuel or driver.
So the question that comes to my mind is this: Why do things get hot when flexed? Do all materials behave the same when flexed? For example, does metal and rubber create the same amount of heat when flexed the same amount?
My suspicion about tire heating is that the flex of the sidewalls contributes very little to heat generation in the tire. I suspect the great majority of heat is generated by the friction on the tread.
All I know is that the hot pressure of the tire is an important setting to keep the tires from getting greasy by the end of a session. If I let the pressure build above a certain level, the tires will get greasy by the end of the session. If I let the pressure get too low, the car feels squishy and imprecise; it will have a tendency to not go where you point it.
So, with my very limited experience with just a couple of different types of performance street tires says that pressures above a certain threshold will cause overheating tire surfaces more quickly than tires at the right pressure. Low pressure tires don't seem to overheat, but then again, they are hard to drive aggressively because they just don't react like they should.
My suspicion about tire heating is that the flex of the sidewalls contributes very little to heat generation in the tire. I suspect the great majority of heat is generated by the friction on the tread.
All I know is that the hot pressure of the tire is an important setting to keep the tires from getting greasy by the end of a session. If I let the pressure build above a certain level, the tires will get greasy by the end of the session. If I let the pressure get too low, the car feels squishy and imprecise; it will have a tendency to not go where you point it.
So, with my very limited experience with just a couple of different types of performance street tires says that pressures above a certain threshold will cause overheating tire surfaces more quickly than tires at the right pressure. Low pressure tires don't seem to overheat, but then again, they are hard to drive aggressively because they just don't react like they should.
And don't forget all wheel drive
you wouldn't be able to get the power down nearly as effectively without that. Bob Smith has the dp1 in his VHPA program. You can load it up and look at the acceleration times. The dp1 with 400hp will rival an F1 car for acceleration.
The tires are interesting. Dennis had a lot of trouble getting any heat into them when driving the prototype. Sure, he wasn't going 10/10ths, but still... It probably has something to do with the very low weight of the car. Finding the right tires will be an interesting challenge.
Well said. LFS won't make you a race driver, but I personally believe that it really helps to prepare your mind for performance driving. Understanding the racing line, braking points, car behaviour and even catching slides come just a tad easier I think.
Yes, exactly. I am not saying the dp1 would be easy to race in LFS, it wouldn't. But damn, what a great car to have in LFS. Chances are, most of us will never have a chance to drive a car like that in the real world, so LFS is a perfect place for it.
However, with what Dennis is doing in the real world, he is helping open the door to real, purpose built, performance cars that are reasonably priced. Eventually, even some of us could have access to one of them.
Oh come-on... do you really want that kind of massively powered (400+ hp, 900lb) all wheel drive, non-downforce car in LFS? It is too much car for most drivers to handle.
The updates to Dennis' site are cool. I can't wait to see some of the final designs. Next season up at PIR should be very interesting. I am sure I will see the cars out and about.
It isn't that they won't add it, it just isn't a priority. I don't think it is a necessity for the product anyway. There are many Americans that are racing fans that have nothing to do with NASCAR or its products. I also wouldn't call LFS European centric. It is sports car / open wheel car centric with a nod towards natural road courses and street courses.
Personally, that is the way I like it.
The problem with that is that the engine power curve in the XRG is different than you would find in an RX7 (or E30 325is in my case). So, the actual gearing from the real car does not work very well even if you go with the highest diff ratio that came with the real car. To make the car drivable without an LFSTweak, you pretty much have to adjust the gearing and diff settings.
Secondly, it does feel strange because most street car gearing is set for comfort and gas mileage, not necessarily for performance. 5th gear is for saving gas for the most part and unless your final drive gearing is really high, you will never need to use 5th at all. The RX7 set was topping out at around 120mph in 4th gear on KY3 and still had RPM's left to go faster. This is about right for the real car, but you can see how long it takes to get to that speed.
In my 325is, I can hit about 120mph indicated down the back straight at Portland International Raceway with my 3.73 diff in 4th gear (it's probably about 115mph actual though). There is no need to shift to 5th. With a 4.10 diff, you do need to shift to 5th on the back straight. In LFS using the intake restrictor and weight handicaps to mimic my BMW, you can never make it to 5th gear with the factory gearing and the 4.10 diff. Well, you can shift to 5th, but there is never a need to shift. This just shows that the engine type in the XRG is just not matched well with the factory gearing.
Using the curb is a very important part of racing both IRL and in the sim. However, there are certain curbs you stay off of because they will badly upset the car or cause damage IRL. The chicanes we are talking about in LFS are either very tall and would damage a real car and are taken at extreme high speed (120+mph), or are very wide and low but have the "sleeping policeman" (as David Hobbs calls them) speed bumps on them. People find ways of jumping those curbs in LFS. If the chicanes were redesigned a tad, it would eliminate some of that problem (not all of it for sure... a lot of it is because it is a sim).
You will see this at Blackwood too. The last curb on the right at the exit of the chicane is always completely jumped when people are hot lapping and also a lot in the race. You can gain a real time advantage by doing that because you carry that speed all the way down the straight. I think that chicane is pretty challenging if you drive the real world line through it. But it gets a lot easier and faster if you jump that last curb. Just watch some hotlaps to see what I mean.
Yeah, I was thinking of the wrong terminology. BMW mostly uses "Electric Differentials" which is an mechanical open diff with wheel brake control. It behaves like a diff would by slowing the spinning wheel and transferring the power to the non-spinning wheel.
This is an excerpt from a Wiki, but from what I have seen, it is pretty much correct.
Electronic limited slip differential system uses Anti-lock brake sensors and hardware to electronically monitor wheel speed. If one of the wheels on an axle is rotating faster, computer briefly applies brakes to it, slowing the spinning wheel down and causing the wheel on the opposite end of an open differential to start spinning and gain traction. This is an opposite to the anti-lock brake application, when a locked wheel is electronically released.
One advantage of this system over mechanical is that the vehicle steering and control is less affected. It also generates less stress on the drivetrain compared to a mechanical locking device, making it particularly suitable for the vehicles with independent suspension. It can also be tuned for specific applications off- and on road and a different speeds.
A disadvantage is that it is less predictable when going over an obstacle, as the system needs time to react. Also, the wheel with traction will only have half of the available torque applied to it.
Some wireless keyboards are terrible for this kind of thing. If your receiver isn't well placed, the keyboard will seemingly partially disconnect and it takes several presses of keys to work... sometimes one press works, sometimes it takes 5.
All of this sounds much more like a wireless keyboard issue than an LFS one.
Yes, very true. But, they aren't taking massively high curbs at 120+mph. Maybe at half that speed.
Yes, better damage models will help the situation and so will changeable track conditions. If somebody drags dirt onto the track because they cut, then everybody pays the price because you lose grip.
But the main point is that some of the chicanes out there demand that you take them mostly flat out and that you take as much curb as possible to do it. In real life, not only would your suspension be damaged, but you would most likely crash. Real racing faces the same problems. Drivers will take big risks and push things past the point of sanity to win. We've all seen it. That is why just asking people to not take so much curb doesn't work. A simple redesign of some of the more problematic chicanes would be a step in the right direction while we wait for the more difficult dynamic changes to the physics modeling. And honestly, it would make tracks like FE much more enjoyable to drive. It would be more technical and demanding. FE is one of the best tracks out there with some really cool corners. The chicanes ruin it for some because no matter how good you are on the rest of the track, blasting through the chicane is the only way to get a competitive time.
I don't know about Subaru and other cars, but BMW's "Active Differential" is just an open diff that uses the computer to apply the brakes on the slipping side combined with the more advanced features of the DSC system. It is really a poor man's LSD.
The BMW Sauber would have some driver controllable diff settings, but it isn't actively controlled by the computer (AFAIK).
Well, that's because it isn't supposed to be the Eau Rouge. Using that name for that corner leads to expectations that can't be satisfied with that corner. That set of corners is much more like the Cork Screw at Laguna if you must compare to a RL track. It is much slower and much steeper than Eau Rouge. And it isn't really a chicane either; it is part of the track dictated by the natural terrain (if electronic Digital Terrain Models can be considered "natural"
).The first chicane/corners at KY3 are awesome. They slow you down and are tough to get right.
There are chicanes out there that are taken at stupid speeds that nobody would ever do in real life... and this is done because curb hopping and straitening out those chicanes is possible. If they were deeper chicanes, then those things wouldn't be as much of a problem.
I also hate the chicane on AS3 (and other configs). But that is because it is hard to get right, not so much because it is a cheesy design per se.
Uhm, yeah... that was the point.
All modern fuel injected cars are timing and mixture controlled by the ECU or engine computer. It is the way that manufacturers can lower costs in building fuel injected cars and more importantly, increase fuel mileage and reduce emissions. If you are willing to sacrifice one or both of those last two features, you can reap some significant hp gains out of many cars.
Modern BMW's won't give you much of anything by tweaking the ECU (sharking, "swapping the chip"). They are very well optimised out of the box. But many other cars can give you 10%-15% improved hp if you get an aftermarket software load or piggy back ECU system.
So, modern fuel injected cars have "artificially" controlled torque curves. It is a bit of an overstatement, but basically true nonetheless.
I understand that situation. You are going to do a "panic" stop. However, I would suspect that there are many things different on the car than what it was probably designed for in the first place... like those hard, skinny tires and the road surface was probably a factor as well.
Romping on the brake instantly will sometimes cause lockups because weight transfer is abrupt and probably some other factors. However, if you properly roll into the brakes with a car with proper tires and proper brake pads and disks, on a decent surface, it is going to be very hard to lock the tires up. As you slow down, which happens quite rapidly, it will get more and more likely you will lock up if you don't reduce brake pressure... modulate as it were.
All I know is that with decent tires on the two cars that I have used on the track, with proper initial braking action, I can't lock up the tires until I get to a slower speed. I am using performance brake pads that do heat up quickly so you get full braking action quickly. (unlike track pads that have to have heat in them before they really work well)
Getting to that slower speed does not take that long. It goes by pretty quickly to you because you are so engaged with what you are doing. It might take a lot longer in reality than you think, but still, you could have hit the brakes at 85mph but not started really locking the tires until you were at 50mph. It goes by quickly in a situation like that.
Sorry, wrong words. How do you reduce power assist on the brakes? Do you put a restrictor in the vacuum line or do you just replace the whole brake booster.
I have an 87 BMW 325is (E30) track rat. The engine is completely disassembled right now while I work on the rebuild. Stupid PO who didn't change oil.
Thats because of those itty-bitty skinny tires you use on that tinkertoy car
.Yes, there are exceptions and yes, you can put more brake on a car than is necessary or wise (I'm not saying you have, btw). Still, LFS allows you to put on so much brake that you can lock up at full speed with minimal brake pressure. That is a bit silly, but I suppose it could be done in real life too.
BTW, how do you reduce the boost? I am wanting to do that to my track rat too.
If you are talking about high speeds and having the brakes lock, then that is because LFS allows you to put silly high braking force values on the car. Real cars won't lock up at high speed no matter how hard you press on the brake. Try it in your passenger car. Get up to 60 or 70 mph and mash the brakes. You won't start feeling the ABS until you are slowed down to something like 40ish mph (assuming you have decent tires). I would say start at a higher speed, but that would be unsafe and illegal unless you were at a track.
If you put on a big brake kit, you will have more brake force available and then you might be able to lock the tires from a higher speed. You have to be very careful with this though since that starts getting very dangerous.
The best brake setup is one in which the tires will be at an optimal slip angle range when you apply full braking power at you highest expected speed and then the driver or ABS will have to modulate the brakes as the car slows down.
Nope. Absolutely not. For qualy and short runs real race cars will generally go out with higher pressures in the tires than they will for long regular race stints.
There is an optimal pressure where the tire works best. When you are doing something like qualifying, especially in F1, you will do an out lap, hot lap, and in lap. The tires won't have time to get enough heat to come up to pressure if you ran at a lower pressure. They therefore start at a higher pressure to make sure the tires are optimal for that one lap.
Longer stints will start with lower pressure because more heat will ultimately be generated so in order for the tire to be at optimal pressure for the majority of the stint, they start with lower pressures that will take a few laps to build up to the right pressure.
I don't know exactly what this means as far as tire temperatures, both internal and surface, but that is basically what is done for the pressures.
That wasn't the point I was making. There is a "bug"/flaw in the modeling somewhere that causes huge forces when the tire has more than one contact point. Just try what I said and you will understand.
Of course if a car smacks one of those nasty speed bumps the suspension should be damaged. Those are extreme and would cause extreme forces as well. That is normal and realistic and is as it should be. Hopping over them at speed is a tad insane and is just one of those things that will have to get looked at sooner or later.
But how many times have cars gone over the lower part of the curb coming off the KY3 oval and gotten flung across the track without hitting the speed bumps? The answer is it happens all the time. It could be a virtually identical line to what they ran the lap before, its just that this time you hit the wrong crack in the curb and you go flying. That is the bug.
The chicanes on FE are the worst. Very high and brutal, yet you can slam over them at full speed while occurring only a small suspension problem that doesn't really affect the handling. You can hit those curbs all day long without too much problem. It makes things pretty extreme because in order to be competitive, you have to smash over those curbs at speeds that would never be considered in the real world.
Yeah, it is a "bug". The suspicion is that the tire model can only deal with one contact point at a time. On some of those curbs, and cracks between curbs, the tire ends up having two simultaneous contact points and the physics engine seems to rapidly switch back and forth between which one is being used. This cause massive forces that throw you off the track.
Try this. Take your car and park it along either the curbs in that last little chicane before the oval on KY2, or that chicane coming off the oval on KY3. The car will just sit there and vibrate if you park it in the right spot.
Try this. Take your car and park it along either the curbs in that last little chicane before the oval on KY2, or that chicane coming off the oval on KY3. The car will just sit there and vibrate if you park it in the right spot.
So you are testing engine braking? Did you play with the engine braking settings on the BF1? That will have a big effect on the results.
Also, wasn't Nick's comments about the actual braking and not the engine braking? His comments seem to correlate nicely with LFS as the high downforce cars are very easy to lock up at lower speeds because of the high brake settings you can use effectively at higher speeds because of the downforce.
In LFS, although lower pressures definitely do increase sidewall and internal temperatures, it also seems to cause the tire surface to heat up more quickly and stay hot longer. It is like the inner tire temperature radiates heat to the tread.
I do notice that when running R3's at higher pressures, that the surface temperature goes up and will go into the red zone, but the rest of the tire stays in the blue zone. But again, if you lower the pressures, generally you will end up with over heated tire surfaces pretty quickly. I will have to do some testing on this stuff to see if a happy compromise can be made.
Maybe it is just that the lower pressure tires are doing more work because of the higher grip levels. But it makes a lower tire pressure almost unusable in long races even with harder tires. The lower pressures will reduce your lap times a tad, but the heat generated will force you slow down quite early in a race.
I don't know why this is for sure, but from practical experience in standard cars and from spending time in the paddock with race cars, typically, high pressure=a hotter tire in a shorter time. Lower pressures=a tire that takes longer to heat up and get "to pressure and temperature".
For qualifying and short stints, tire pressures are typically higher than you would set for a long stint. For hot days, tire pressures are generally lower than you would set for cool days.
LFS seems to have it backwards in practice. We always go out with low pressure for qualifying and hot laps and use high pressure for long stints. We get more grip from lower pressures, but suffer from over heated tires in a hurry. If we exclude major tire spin or sliding, then this seems a bit backwards.
Real tires have an optimum temperature and pressure where they work best. This will also be dependent on the car, the suspension type and track type. In LFS, this optimal setting seems a bit hard to come by.
Could it be that there is a lot of heat transfer going on between the tire surface and the air in the tires? At low pressures, the air inside the tire can take a lot of heat because it has the room to expand? Once to pressure, the air can't take much if any more heat from the tire so there is no more "heat sink" to use?
For qualifying and short stints, tire pressures are typically higher than you would set for a long stint. For hot days, tire pressures are generally lower than you would set for cool days.
LFS seems to have it backwards in practice. We always go out with low pressure for qualifying and hot laps and use high pressure for long stints. We get more grip from lower pressures, but suffer from over heated tires in a hurry. If we exclude major tire spin or sliding, then this seems a bit backwards.
Real tires have an optimum temperature and pressure where they work best. This will also be dependent on the car, the suspension type and track type. In LFS, this optimal setting seems a bit hard to come by.
Could it be that there is a lot of heat transfer going on between the tire surface and the air in the tires? At low pressures, the air inside the tire can take a lot of heat because it has the room to expand? Once to pressure, the air can't take much if any more heat from the tire so there is no more "heat sink" to use?
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