This guide is to help anyone that would want to establish customizing vehicle performance to what they see fit without dealing with all the guesswork of what numbers to use. By using this guideline, you will gain an understanding of what effect on the vehicle each setting gravitates towards as you increase or decrease the values you choose to set. My findings are incomplete but since it's in high demand, I decided to fill the void now and update later.
All results you're about to see were done:
- At 60 fps constant
- In clear weather conditions
- Tested on a rear-wheel drive vehicle
- Vehicle had equal distribution of brake force between front and rear wheels (unless stated changed)
Also, a good portion of the results isn't scientifically proven (meaning not everything I account for was measured for statistically significant differences). Most of it is just personal observation of the differences I feel in the vehicle. So these areas may hold less weight and it is open for scientific proofing for validation. Anywhere I state numerical results means that I validated it; if it doesn't, it's just observation and personal feeling.
This guide also assumes you know how to edit XML data for custom vehicles. For ease of mind this link here should be able to help you out most of the way on how each setting affects the car's characteristics bodily wise. I'm filling out the performance aspect.
Most values were shifted by a magnitude of 1 in either direction (negative or positive) from its original value unless I state that something took an extreme (note the word choice, not if I say high or low, only extreme) increase/decrease in value to achieve the result (in which case, such values were shifted by a magnitude of 10).
When I say setting values to low, for most values this means using negative numbers. The only exception to the rule are bias settings where those only use positive numbers and have a range of just 0 to 1 and settings that only work with positive ranges (like mass and number of gears).
1G_BOOST - this flag speeds up the acceleration rate of the first gear. If this setting is disabled, you will hear the vehicle have a delay in sound to when the engine rev kicks in. The car is still moving but the rev is low and tamed. Enabling this setting skips that delay completely and the engine revs with max acceleration from the start
- Disabled - 2.5 seconds to shift out of 1st gear
- Enabled - 2 seconds to shift out of 1st gear
2G_BOOST - this flags does the same as the 1G_BOOST but for 2nd gear. The difference however is much smaller (almost insignificant). Negligible enough to be ignored, however, it might help heavy vehicles greatly in theory (didn't test to check).
- Disabled - 1.65 seconds to shift out of 2nd gear
- Enabled - 1.5 seconds to shift out of 2nd gear
IS_LOW - this flag seems to lower the centre of gravity of the vehicle making it slightly harder for vehicles to roll (was not tested with a van that has more rolling capability so results may vary)
REARWHEEL1ST - this I believe increases the bias of wheel drive power to the rear wheels. The car is notably faster with the setting OFF rather than ON (my guess is the increased power to the rear wheel causes a bottleneck in traction, leading to more wheel spin & burnout but less propulsion of the vehicle)
- Disabled - 6 seconds from point A to point B (in sand)
- Enabled - 6.2 seconds from point A to point B (in sand)
GOODINSAND - namesake, improves handling of the vehicle in sand. No change in general speed, but acceleration from stationary to 2nd gear greatly improved (especially on an incline in sand)
NEUTRALHANDLING - no observable changes (maybe helps bikes instead, never tested)
That covers the flags that I found and/or believed would have some effect on vehicle performance. Now we go into the variable attributes that you can set to any value (sort of).
Mass - PAY ATTENTION FOR THIS ONE. You would think this one should be as straightforward as deceleration was for brakes. You would be horribly wrong. It turns out, this is the most illogical setting of them all. So sit tight while I explain this.
In terms of collision force, this is logical and holds true to reality. The greater the mass, the stronger the force you generate hitting other vehicles and vice versa. Handling is unaffected whether it's high or low mass. We can debate whether this is true to life or not but for me I don't think it matters enough to be an argument considering the rest of settings.
Logical reasoning ends right there my friends.....
This is because the more mass you add, the FASTER your vehicle will go. You essentially become a speed hacking tank driving around. It's sheer madness.
Similarly the lesser the mass, the SLOWER your vehicle will go. You essentially become a snail with the force of paper.
This makes changing the mass of your vehicle very tricky, and is what inspires Part 2 to this guide, where I will calculate all the relationships of the settings to keep performance at a constant.
Dimensions - NEEDS TO BE STRICTLY CONSIDERED. Through my investigation of vehicle models versus the data presented in handling.cfg of the game files, most settings don't add up one bit. Ever notice that outside top speed and maybe acceleration, almost every car in a specific category kinda feels like it handles the same? Despite the reality of vehicle size variations, most vehicle stats are generalized in their dimensions. If you look through the game stats, you'll see predominantly for the x axis (this controls width of the vehicle) that the setting is 2.0 m with little variation outside this (an Infernus is much wider than the tiny Manana car for example but they have the same x axis value in game stats). The y axis (vehicle length from front to back) and z axis (vehicle height) seem to show a lot more variation that more or less reflects truthfully the vehicle's actual model dimensions.
Now what effect does the dimensions have on the vehicle if all other things are equal? It affects WEIGHT and HANDLING. The bigger the vehicle dimensions, the heavier it seems to feel and is noted by a large reduction in speed, lower jumps, stronger collision force, everything you'd expect of a bigger vehicle. Also the bigger the vehicle, the more it feels like a van, or truck - sluggish in turns and has higher chance rolling onto it's roof (probably proportionately changes centre of mass as well to cause this). Inversely, the smaller the dimension, the more the quicker and nimbler the vehicle. Feels like a toy race car the lower you go, and the car becomes lighter, thus higher jumps, decreased collision force etc. (and is able to ragdoll like crazy if you crash in air).
Centre of mass - determines where most of the mass of the vehicle is distributed against the dimensions of the vehicle. Each axis gives a different result.
- X axis - the car will balance on two wheels depending on direction pretty much like this:
It's impossible to drive in this state, but if set to an appropriate level where all 4 wheels are on the ground, the car will have a tendency to roll when you turn in the opposite direction of centre of mass (so if the centre of mass has a left bias like the picture shown, then if you turn your vehicle right, it will roll over and vice versa). The side of the car that has centre of mass bias makes sharper turns whilst the weaker side understeers and tends to want to lift up should you hit a bump let's say. Vehicle will have the tendency to want to rotate clockwise/anti-clockwise up to a point when in mid-air after a jump depending on the respective side of mass distribution (if the centre of mass is to the left, the vehicle rotates anti-clockwise slightly and vice versa)
- Y axis - This operates similarly to what you would expect of the traction bias but make note that they are NOT equivalent settings. They both cause distinct effects on the vehicle that rightly sets them apart.
When the centre of mass is distributed to the front of the vehicle, the car's traction at the front increases greatly and ultimately causes the vehicle to suffer (too much traction at the front causing rolling resistance when turning under speed). The rolling resistance slows down the vehicle considerably with every turn you make. Turning becomes less nimble and tends to increase understeering. The vehicle also tends to glide very smoothly in a straight line to the direction you're facing when bringing the vehicle to a sudden stop. The vehicle nose dives when jumping and cannot drift whatsoever.
Vehicle is also slightly slower in acceleration:
- 7.1 seconds to 5th gear default centre of mass
- 7.5 seconds to 5th gear under front-end biased adjustments
When the centre of mass is distributed to the back of the vehicle, acceleration is unaffected and the back-end of the vehicle tends to spin out with every turn you make. Impossible to drive at these levels, but if set appropriately, the vehicle becomes extremely nimble, and the turning is much sharper (it's like driving a Cheetah but nimbler in a good way). Back of the vehicle dips when taking jumps.
- Z axis - vehicle tends to roll very easily when set to higher heights. Vehicle also jumps higher but not farther. Other than that, nothing else really feels different. When set to lower heights, the vehicle becomes resistant to those bumps that would lift your wheel from off the ground. Vehicle jumps lower but farther.
Traction - traction is the grip your wheels have on the road. When set to low values, the loss of grip causes:
- Increased braking time
- Reduced top speed
In contrast, increasing the traction value eliminates wheel spins, decreases brake time and leans towards oversteering (but in a very very good way, so good it's like it reduces input lag, making the vehicle feel more responsive to your controls). The increased traction however also causes reduced top speed as the engine power is now the bottleneck (causing rolling resistance).
Traction loss - I'm not sure under what circumstances this setting gets applied but it has a critical function.
If this setting is set too low, the vehicle loses all capability to stop (the perfect body in motion as an example for our physicists here). If you so much as touch the vehicle, giving it a tiny bump with your player, it will slide away forever.
With the setting set high, the vehicle has increased steering agility with an increased susceptibility to want to roll over IF steering is locked (not sure why on that though). Other than that, pretty much mimics the traction high settings.
Traction bias - determines the level of traction distribution between the front and the rear wheel. If the value is set up to 1 (front wheels), the vehicle cannot be driven and the rear wheels spin out. If the value is set to 0 (rear wheels), the vehicle is able to drive and feels like normal but the vehicle cannot turn. Therefore traction bias is a balance of turning ability and acceleration. They have an inversely proportional relationship.
Number of gears - setting this to a lower value does decrease the speed but not as significant as you would expect (29 seconds form point A to point B using a lower value vs 28 seconds at highest settings) . This setting also does not follow completely true to life. I didn't have a speedometer so I have no way of confirming definitively that I was hitting the same maximum velocity, however the difference in vehicle performance seems negligible enough to ignore this setting.
One thing you SHOULD NEVER DO is set the value above 5. This COMPLETELY GLITCHES THE GAME. If you drive a vehicle with 6 gears, it may try to fly and bounce off all manner of debris, 7 gears may bounce around all over the map, 8 gears flat out freezes the game and hangs the PC system. DO NOT USE ANY VALUE ABOVE 5!!!. You have been warned.
Engine type - in reality there are advantages and disadvantages to electric, petrol and diesel engines in terms of performance. GTA Vice City ignores all that jazz so this is a setting you don't need to tamper with, there's no difference in performance between all 3.
What it does is make a visual change in the exhaust smoke (different colour between diesel and petrol, no smoke at all for electric engine).
Acceleration - fairly straightforward setting. The more you give, the faster you will accelerate. However there is a point where traction becomes a bottleneck and you will get no further benefit from going crazy in acceleration. So it is definitely a balancing act to achieve as high of an acceleration as you want (though arguably this balancing act could be cheated with setting the mass higher, seeing how illogical that is right?). Most of the acceleration happens in the first gear. Lower settings just means lower performance, no change to handling.
Brake - what's used to stop the vehicle
Deceleration - pretty obvious really but I tested just to make sure. More you give it, the stronger the brakes, the less you give it the weaker the brakes.
Brake bias - determines the distribution of brake force between the front and the rear wheels.
A value of 0 (rear wheels) makes the vehicle perform very sharp turns when braking. However brake performance to stop the vehicle gets worse. Similarly with a value of 1 (front) the brake performance is as worse as 0 than if the brake force was evenly distributed (0.5). The vehicle refuses to turn and drifts in a straight line and braking and turning with a brake bias of 1.
0.5 gives the best stopping power, and this is to be expected, as it is never a good thing to have brake bias in real life AFAIK.
Suspension - the suspension is what is used to adjust the vehicles height (height of the vehicle body from the axle of the wheels) as well as what eradicates the jerky effects of driving over bumps in the road, keeping the body of the vehicle in a stable parallel position to the ground (shock absorbance properties).
Force level - In extreme cases, the vehicle resists bumps in the road, however, a good strong bump that would normally cause spin-outs can now send you flying. I attribute this to the fact that the vehicle at these very high settings becomes bouncy in a stable way. All in all, the suspension becomes STIFF and should not be mistaken to be used to gain more shock absorbance.
Vehicle height is also affected by this sing (the higher the value, the bigger the gap between the vehicle body and the wheels and vice versa).
Dampening - this is the setting that is for the shock absorbance properties of the suspension. High settings makes bumps a thing of the past, but it is not all happy days doing so. The way a suspension works is that it compresses itself upon hitting a bump, which therefore makes the body of the car remain relatively as leveled as it was to the ground before the bump. It is because of that fact that increasing this dampening value also inhibits jumping capability (your vehicle basically absorbs too much out of any ramp and just tries to head straight, completely leveled). The vehicle body also elevates away from the wheels as well with this setting.
Too low of a value and the vehicle is impossible to drive. The vehicle just bounces around to any and everything. Appropriate settings are therefore recommended when it comes to dampening.
Upper limit - Not a useful setting to change from defaults in my opinion as it causes some strange effects. At high settings, the wheels begin to rotate along the y axis and mimic the cheat "SEAWAYS" when driving on water (the wheels change to that look). Vehicle is also lowered to the ground as a result.
In low settings, the vehicle simulates 100% traction loss, only this time the wheels are glitched into the floor. As stated, best not to trouble this one.
Lower limit - lower settings raises the body of the vehicle significantly. Could be useful if you would want to have a vehicle model similar to monster trucks like this
However note that you if you do not increase the size of the wheels appropriately, low settings will make the body of the vehicle look like its floating in mid-air.
The setting also amplifies dampening in and gives a more realistic result of how the wheels adjust to bumps in real life (that springy look) and makes the car more susceptible to rolling (like a van as the height of the vehicle has been increased tremendously).
In high settings, the vehicle body is on the ground while the wheels are in the air. Therefore high positive values are not good values to use with this setting.
Bias - again, distribution of suspension settings between the front and the rear wheels. A value of 1 keeps the front wheels high but lowers the rear wheels. This introduces vehicle bumper scraping as you drive along. No real observable differences in performance and handling outside this fact however.
A value of 0 does the opposite, it keeps the rear wheels up while the front wheels are lowered, causing the same effect as stated above. One addition however with this setting is that the vehicle now tends to be bouncy with bumps as you hit them, so it's kind of unstable to use this value.
Antidive - this setting prevents the vehicle from leaning in a certain direction when stopping (the inertia effect that tilts the car forward or backward when stopping) and thus keeps the vehicle leveled at all times. The way how the game implements this is like an invisible force that pushes either the front-end or the back-end of the vehicle upwards in the air depending on how you're stopping.
So when stopping from driving forward, the front of the vehicle leans down to the ground. This setting therefore a applies and upward force at the front of the vehicle to cancel that inertia. Likewise, when you're stopping from reversing, the back of the vehicle leans down to the ground, and this function now applies an upward force to the back-end to negate the effect
If you go extremely high on this setting, the vehicle will flip onto its roof like you would flip a remote in your hand everytime you stop. Therefore, appropriate settings are needed for this. If you hit the sweetspot, the car will remain 100% leveled when you stop, however, this has a negative effect on brake time that is of similar magnitude as setting 100% brake bias to a particular direction.
All negative values for this setting seem to have no effect on the vehicle, therefore only use positive values for this attribute.