Setup The Race Car IV

Setting Up The Race Car Part 4

Transmission ratios:

The function of the gear box is to keep the engine in the power band as much as possible. The power band is the range of RPM where the engine generates the most torque. In the simulation, this seems to be a fairly narrow band from about 7500 to 9000 RPM. Real Winston Cup teams spend a lot of money developing engines that have large power bands.

A higher number means a lower (or shorter) gear. Short gearing gives quicker acceleration, but because the engine must turn faster, fuel mileage and top speed are lower. Tall gears give smoother acceleration and higher top speed, at the expense of quick acceleration. We are allowed transmission ratio changes in within following ranges:

1st gear 1.36 – 3.54
2nd gear 1.11 – 2.41
3rd gear 0.88 – 1.94
4th gear 0.88 – 1.67

Transmission ratios are very rarely changed, unless your running at a track that requires a lot of shifting, like a road course. Most of your ratio changes will be made at the rear end in the differential. The most important factor in selecting proper transmission ratios, is to make sure your not geared to high causing excessive wheel spin. You must also be sure you have a good split between ratios through all 4 gears.

You’ll want to maintain as high an rpm as possible when shifting through the gears. To large a split ratio between gears will cause slow acceleration and lost time whenever shifting is required. Most notably on a road course and exiting the pits.

Start by setting 4th gear for the high speed part of the track. In most cases you will want the engine light to blink just as you hit your peak speed. Consider adjusting peak speed to where you make the transition from the straight to the turn entrance. In another words, where you lift off the throttle and start to brake or decelerate.

On tracks where you shift, you may want to make 4th gear a little taller so you spend as much time as possible in the power band. Tracks where drafting takes place, you need to make 4th a bit taller to give yourself some safety margin when you pick up the draft.

Next, work on first gear. Set up first gear so the engine is turning around 7000 to 7500 RPM on the pace lap. This will also aid you for your pit speed. This will help you get a jump on starts and restarts. Be careful that you don’t get too much spread between 2nd and 4th gear, or you might be lugging when you go into 3rd or 4th gear.

Once you get 1st and 4th gear set, the procedure for 2nd and 3rd depends on whether you’re setting up for an oval or road course. On an oval, when you shift, then 3rd gear will be setup to put the engine in the power band coming out of the corner. Now set 2nd gear so the RPM going into 2nd is the same as the RPM going into 3rd gear. This can be done mathematically. Divide the 1st gear ratio by the 3rd gear ratio, then take the square root of that. Then multiply it by the 3rd gear ratio.

On tracks where you don’t shift, simply work up 2nd gear and 3rd gear to give the same RPM going into 2nd, 3rd and 4th gear. This too can be done mathematically. Divide the 1st gear ratio by the 4th gear ratio, then take the cube root of that. Then multiply it by the 4th gear ratio to get the 3rd gear ratio, then finally multiply again to get the 2nd gear ratio.

On road courses, 1st, 2nd and 3rd gear should be set to put the engine in the power band at critical points on the track. Typically, the most critical places are the corners that lead onto the long straightaway. Every MPH of speed you can gain coming out of a corner adds to your speed at the end of the straight.

Differential ratios:

The differential is a gear assembly in the rear end whose purpose is to distribute torque to the rear wheels for traction. We have the ability to change these gears allowing us to run different ratios for different size tracks.

The ratio expresses the number of turns required by the pinion (which is attached to the output shaft of the transmission) to turn the drive axle one revolution, i.e. 2.86 means the pinion must turn 2.86 times to turn the drive axle once. A higher number (6.56) means a lower (or shorter) gear. Short gearing gives quicker acceleration, but because the engine must turn faster, fuel mileage and top speed are lower. Tall gears give smoother acceleration and higher top speed, at the expense of quick acceleration.

We are allowed to choose from no less than 48 different ratios with an adjustment range from 2.86 to 6.56. The differential ratio you will need to change for every track and is the most common gear changed on a WC race car. When you change the differential ratio, you change all the final drive ratios together proportionally.

On short tracks you will want to choose a higher differential ratio because quicker acceleration will be a must at tracks where speeds are not as high. At superspeedways you’ll want a smaller ratio for top speed since quick acceleration is not necessary on a track where your at full throttle most of the time. The most important factor when considering what ratio to use is that you don’t choose a ratio that is too high. Too high a differential ratio will result in running higher rpm.

If, when you reach the end of a straightaway, your running higher than 9000 rpm, you risk having the rev limiter kick in. The result will be a loss of torque and loss of speed. The rev limiter is to prevent us from running the rpm too high, which would result in a blown engine. You must watch your tach when changing gear the ratio. If your running too high an rpm you will also notice it through the sound of your engine as a “missing” sound.

As you adjust other chassis components, you will most likely find yourself having to change your differential ratio. As you find more speed through the corners, you’ll eventually find yourself on the throttle quicker. Since your on the throttle sooner you will be running a higher rpm towards the end of a straightaway. This will force you to make a differential change.

Final drive ratios:

The final drive ratios is a non adjustable option that is basically used for comparison purposes. The final drive ratio represents the number of engine revolutions to rear wheel revolutions. The final drive ratios can be viewed for all four gears. These 4 ratios change automatically whenever the differential ratio is changed and will change individually per gear whenever a transmission ratio is changed.

Like the differential and transmission ratios, the final drive ratios are read in the same manner. A higher number means a lower (or shorter) gear. Short gearing gives quicker acceleration, but because the engine must turn faster, fuel mileage and top speed are lower. Tall gears give smoother acceleration and higher top speed, at the expense of quick acceleration.

Your highest final drive ratio will be in 1st gear and should get smaller as you move through the gears. Your final drive ratio will be the same as your differential ratio. Unless your at a track that requires a lot of shifting, the final drive ratio will not be that important and is only used to compare how your ratios change through the gears after attempting a differential or single transmission ratio change.

Race adjustments:

This section will discuss the adjustment options we have available to us during a race while pitting. Once the race begins, were limited as to what we can adjust to help improve our chassis.

The following is a list of options we can change during a pit stop:

F3 Fuel
F5 Tires/psi.
F6 Wedge
F7 Track Bar
F8 Grill Tape

To change the amount of fuel you would like during a pit stop you must press the F3 button. From here you can use you left and right arrows to select how much fuel you want to take on. You are allowed to take on a splash of fuel as well as 1/2, 1, 1 1/2, or 2 cans. A splash of fuel will give you 2-3 gallons. 1/2 can gives you 5-6 gallons. 1 can equals 11-12 gallons, 1 1/2 cans will give you 17-18 gallons. 2 cans will fill your tank with 22 gallons. The less fuel you carry the faster you should be. Use this to your advantage when planning pit stops, race strategy and fuel mileage.

Pressing the F5 button for the tire change screen. Here you are able to decide how many tires you would like changed as well as any psi adjustments you would like to make. Pressing the space bar will allow you to toggle between taking on 4 tires, left sides, right sides or no tires at all. Using the up and down arrows on the keyboard will allow you to select each individual tire that you would like to make an air pressure adjustment too.

Hitting the left and right arrows will allow you to increase or decrease the pressure of the selected tire in 1/2 lb. increments. Tire psi is the most difficult of all adjustments to remember while pitting because it can be changed in conjunction with other tires to produce various results.

Here is a general breakdown on tire psi:

Higher psi in RF will loosen the car.

Lower psi in the RF will tighten the car.

Higher psi in RR will tighten the car.

Lower psi in the RR will loosen the car.

Higher psi in the LR will tighten the car from the middle out.

Lower psi in the LR will loosen the car from the middle out.

Higher psi in the LF will tighten the car.

Lower psi in the LF will loosen the car.

The lower the psi in a tire the hotter it will run.

The higher the psi in a tire the colder it will run.

Excessively low front tire psi will create a push.

Excessively low rear tire psi will create a loose condition.

Increasing the split (more RR psi than LR) increases stagger, helping the car to turn in the middle of a corner

Increasing the split of the left and right side psi (more psi on the right) increases the pull to the left.

The F6 button allows you to make a wedge adjustment. Use the left and right arrows to increase or decrease the desired amount of wedge. You can change the wedge in 5 lb. increments. Increasing wedge (higher %) will tighten the chassis. Decreasing wedge (lower%) will loosen the chassis.

Use the F7 button to adjust your track bar. Using the left and right arrows we can raise or lower the track bar in 1/4″ increments. The important thing to remember when adjusting the track bar during a pit stop, is that your raising or lower the RIGHT SIDE ONLY. In the garage were allowed adjustments on both sides. Because were only adjusting the right or frame side of the track bar, we are adding rear steer to the chassis.

Therefore raising the track bar during a pit stop will make the car looser under acceleration while at the same time tighten you up under braking. Lowering the right side of the track bar will have the opposite effect and will make the car tighter under acceleration and loosen you up while braking. The more you raise or lower the bar, the greater the effect on the chassis.

Adding or removing grill tape is another adjustment we can make by using the F8 button. The left and right arrows will add or subtract tape in 5% increments. Adding grill tape reduces drag and increases speed. Adding tape also places more downforce on the front end and can be used to loosen the car up through the corners. Be sure to keep an eye on your gauges. Too much tape will raise your water temperature and overheat your engine, you might be forced to make an extra pit stop to remove the tape to help cool the engine.

As you can see, the number of adjustments we have available to us during a race, are far less than we have in the garage. Because of this it is important to have your setup close before entering a race. Use the above adjustments to fine tune the chassis for the various weather conditions and to readjust your chassis as a race progresses.

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Comments
  1. steve says:

    I do a lot of nascar racing on gt5. Recently been hearing people talk about to forh gears. And the guys talking about this are by themselves passing 3 cars in the draft. I’m not sure but I heard them saying something like multiply 4th gear times final drive and that equals your third gear. raising the top speed to 298 and putting the final drive somewhere in the area of 3.8 -4.0! from what I understood him talking about I tried to do this and it didn’t work. the gear ratios just sitting exist. Or maybe I had the formula All wrong. I am stuck trying to figure this out I will not give up. Could you please let me know if you’ve ever heard of something like this. Thank you.

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