RIDE HEIGHT vs. ACCELERATION

[NISMOgtrztune]

Ive tried this on many cars, but always seem to come up confused with the way it works or just give up entirely. I like tuning cars to run the quarter mile. A factor in doing so is adjusting the ride height. For some reason, raising or lowering the car can have a beneficial impact on acceleration. For some cars ive tuned, the setting has to be lower. For some it has to be higher. I understand the concept of lowering it to give the car better grip and handling around turns, but i am only after straight-line performance. This, I feel, would have a big impact on the way i tune cars. If anyone knows how this affects cars in real life I would appreciate the information. Thanks for the advice.

 

[rk]

Ive tried this on many cars, but always seem to come up confused with the way it works or just give up entirely. I like tuning cars to run the quarter mile. A factor in doing so is adjusting the ride height. For some reason, raising or lowering the car can have a beneficial impact on acceleration. For some cars ive tuned, the setting has to be lower. For some it has to be higher. I understand the concept of lowering it to give the car better grip and handling around turns, but i am only after straight-line performance. This, I feel, would have a big impact on the way i tune cars. If anyone knows how this affects cars in real life I would appreciate the information. Thanks for the advice.

I would suggest that you are giving the programmers too much credit. I would love to have a miniature world inside my PS2, but it just isn't so. Since it would take too much time to code a miniature world thoroughly and apparently a freaking racing game ADEQUATELY, we are faced with certain compromises. The only possible real world reason a raised car would go faster is because the terrain is rougher than lowered suspension will travel. One would hope a tuner of your skills could identify that condition. The only possible other reason THIS contributor can dredge up is that you are somehow invoking the ground effect portion of the physics engine. The effect was very pronounced in GT2, it may have been considered an exploit, to the point that I consider it absent in GT3. Now it's back, definately a setting I adjust for and it sounds like you are accessing it unintentionally. Drag racing is not my specialty, although it is probably the only legal real world competition I have driven in, but I don't know if ground effect downforce is desireable. Presumably it forces the drive wheels into the pavement so it would be "good".
To answer your question about gears, I would remind you that the hp/torque curve is a graph of a graph, similar to the way that horsepower is really torque/speed. Remember that the RPM axis is actually the jagged diagonal line that enters the graph at "speed zero/distance from starting line zero" and leaves the graph at 200+/1000M. A torque curve has to practically reverse to not get further advantages from more RPM and it is next to impossible to NOT get more HP from more RPM. The limiting factor is the increasing difficulty of getting more RPM. So far as shift points are concerned, real drag racers shift when their butts stop getting pushed into the seat. Perhaps you could establish a lap ghost to test acceleration. I used a similar test to learn ideal brake settings and suspension damping and the ghost is accurate to the thousandths of a second. So if I make a ghost then improve my braking very slightly, say by adjusting camber, the next time I hit the start/finish, there it is; and if it is half a car length ahead or behind, I have my answer, all in a setting I think even a radar gun couldn't differentiate.

 

[DarkKni9hT]

Take a look at dragsters and funny cars for your answer. Very low at the front, very high at the back. By lowering the front of the car as close to the ground as possible, the amount of air that slips under the car, creating unstable drag and potentially deadly front end lift, is limited. Raising the rear tips the weight balance to the front, accentuating the nose down, as well as making room for the huge tires. The overall wedge shape of the car created by the low/high setup is more effective at slicing the air that a level vehicle would be.

 

[Duke]

Actually, the reason they are up high in back is not merely to accentuate the wedge shape of the car. Also, ride height at each end of the car does nothing to the static weight distribution.

The reason that RWD drag cars are up high in back is to encourage weight transfer. For ideal traction, a RWD drag car wants all of its weight on the back tires, with just enough weight on the nose to prevent uplift. So having high ride height in the back allows the car to squat on its haunches at launch and transfer as much weight as possible to the drive wheels.

I can't find a picture of a car called The High and Mighty, but look at this vintage hemi Coronet. See how high it sits at both ends? These are at-rest pictures:

This is why FWD draggers keep them low and stiff in back - because they want to keep as much weight up front as possible at launch. Serious FWD draggers even run wheelie bars even though it's a physical impossibility to skylaunch a FWD car; the wheelie casters touch the ground when the car squats, doubling the wheelbase and transferring weight back up front. In fact, the rules prohibit 'preloading' the wheelie bars by having them push down onto the ground when the car is at rest, because that increases the weight distribution toward the front wheels.

So RWD cars want a lot of ride height, particularly in back, to facilitate weight transfer while AWD (to some extent) and FWD cars want to be low in order to reduce weight transfer.

 

[DarkKni9hT]

I may be mistaken, but I was under the impression that FWD draggers' Wheelie bars actually operated on a modified hydraulic system that used them to physically push up on the rear end of the car to affect weight transfer. The wheels at the rear of the wheelie bar system effectively become the rear wheels of the car. Otherwise with the power they run the front tires would simply spin off the car.

And yes.... shamed... I was a little sparse in my descriptiion of ride heights. It was early and I didn't feel like typing a lot. The high rear end does in fact have much to do with the squat under power, I know.

 

[Duke]

I may be mistaken, but I was under the impression that FWD draggers' Wheelie bars actually operated on a modified hydraulic system that used them to physically push up on the rear end of the car to affect weight transfer. The wheels at the rear of the wheelie bar system effectively become the rear wheels of the car. Otherwise with the power they run the front tires would simply spin off the car.

That's sort of correct, though it's not an active hydraulic system. It's more of a spring/damper unit. But they've changed the rules from most FWD drag racing events to prohibit preloading the wheelie bars; the casters may not touch the ground when the car is at rest on a flat surface.

 

[NISMOgtrztune]

Thanks for all your guys input. I know I give this game way too much credit regarding the settings and what they do. In my opinion, to achieve the fastest time, everything should be adjusted (if not just for the sake of seeing what it will do). Like I said though, I am using an AWD WRX. The VCD is set at 50% to the front wheels, making the weight distribution at take off something like 70/30 (back/front) right? Should I change the weight transfer so that there is more in front to compensate with launch? The nose of the car raises near the start of each shift....

 

[NISMOgtrztune]

rk, how old are you? You really seem to know your stuff. Just wondering how I could improve what I know in real life (not so much in a game) so I could tune my own car. Did you work with cars or have experience tuning them? Some of your replies are complicated, no doubt they help immensely, but sound like a professional talking.

 

[Sparx89]

IM sorry to tell you that the car nose ALWAYS lifts when you shift. Its inertia or something. Its because your not giving the car power as you switch gears.

 

[Duke]

Actually, the nose will drop during the shift because you're not accelerating; this transfers weight forward. When the power comes back on the nose will rise again.

For a WRX I would try setting your VCD to put more power to the rear wheels in order to maximize straight-line traction; maybe 25% front 75% rear as a baseline and adjust it either way to see how your times change. I would keep the ride height near stock in back and maybe drop it in front; put stiff bound and soft rebound settings on the front struts.

The game doesn't seem to model wheel lift except from bumps (ie, the inside rear of a FWD car will not lift on a fast turn) so I doubt it models wheel hop. Experiment with soft spring, bound, and rebound settings in the rear to see if you can keep the weight planted on the back wheels.

The other thing to really take care with is transmission ratios. This is tough to do well without power graphs for the cars, but you may find that slightly-less-than-ideal gearing may actually be faster if you can cut one shift out of your drag run. The only way to tell that is by experiment, unfortunately.

 

[rk]

rk, how old are you? You really seem to know your stuff. Just wondering how I could improve what I know in real life (not so much in a game) so I could tune my own car. Did you work with cars or have experience tuning them? Some of your replies are complicated, no doubt they help immensely, but sound like a professional talking.

I am not quite as old as the hills, but many of the trees on them are younger. Thanks for the complement, but I mostly just seem to know my stuff. Most of my experience derives from motorcycling, the knee dragging kind, a Kawasaki 500 triple is what I dragraced, but only on one occasion. I came close to safety wiring my KZ550 to qualify to race at Sears (Infineon), but then my friends started dragging themselves off the track with their horror stories, ah youth...
So now I just armchair race, I very much enjoy learning and sharing about the game here because I feel my tuning skills help me compensate for the savantic deftness some of my friends drive with.

 

[NISMOgtrztune]

Yeah, Duke, I do work with the gears on the strip. Generally if you start it in second it will shave off a few tenths. Also Im really working on the gears right now. Mainly just the final drive ratio. Ive found that this really affects the run. Im almost ready to start a new thread with it (its a lot of information). It will explain a lot, and Ive been suprised to learn more than I thought I would from it. I cant tell you how it works, just what to do to make it work. If anyone is interested, I think Ill just start a thread on progress with tuning the WRX. Taking this project to the next level has really been a good thing. At this point, Im using this car as a guide to learn from and become a better tuner.