| TRANSMISSION BASICS |
| Obviously, if you've played your fair share of Forza Motorsport, you've seen a lot of those gearing charts like the one below. You have the slider that allows you to move the gears in one direction (toward ACCELERATION) or the other (toward SPEED). You can also tweak each individual gear, but what for? There are a lot of valid reasons to tune each gear individually. The transmission gearing holds perhaps the biggest flaw with relying on a purchased tune or having only one set up on a car you put together yourself. No single transmission tune will work for every track. Knowing how to tweak your gears to suit individual tracks will pay dividends in shaving those valuable tenths off of your lap times. |
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| READING THE CHART |
| Okay, so maybe you're a noob and as far as you're concerned, the graph above may as well be in a foreign language. Don't push the panic button, it's not that complicated. |
| First of all, let's create a hypothetical race car using the chart. The first thing to note is that each line that's plotted represents a gear in this car's transmission. This car has 6 GEARS. The next thing to note is that this car has a redline of 7500 RPMs as indicated by the red horizontal line midway between the 7 and 8 on the left side of the chart. |
| That said, let's get to reading. |
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| I've thrown some vertical lines into the graph (PINK DOTTED). But first, look at 1st GEAR highlighted in GREEN. 1st GEAR starts at 0 MPH and 0 RPM. As the RPM increases, MPH increase as well. So 1st gear will hit it's rev limit (7500 RPM) at 55 MPH, at which point we must shift to 2nd GEAR highlighted in ORANGE. |
| Now look at the top of 1st GEAR and follow the PINK dotted line down to the bottom of 2nd GEAR. (The line is straight up vertical). The bottom of 2nd GEAR picks up where 1st GEAR ended, at 55 MPH. Also note that the RPM drops as well, from 7500 to 4800 (indicated by the BLUE dotted horizontal line). This is important to know when we go to match this transmission chart with the HP-TQ (dyno graph) later on. |
| So 2nd GEAR runs from 55 MPH (at 4800 RPMs) to 85 MPH (at 7500 RPM) at which point we have to shift to 3rd GEAR, which picks up at 85 MPH (5400 RPM). |
| Finishing off the numbers for all 6 GEARS it looks like this: |
| 1ST GEAR : 0 RPM - 7500 RPM 0 MPH - 55 MPH 2ND GEAR: 4800 RPM - 7500 RPM 55 MPH - 85 MPH 3RD GEAR: 5400 RPM - 7500 RPM 85 MPH - 110 MPH 4TH GEAR: 5700 RPM - 7500 RPM 110 MPH - 140 MPH 5TH GEAR: 6000 RPM - 7500 RPM 140 MPH - 170 MPH 6TH GEAR: 6200 RPM - 7500 RPM 170 MPH - 200 MPH |
| One point of interest to note that is consistant with gearing is that in order to keep the car running in the powerband (and making the most horsepower possible) the revs, when upshifting to the next gear, should not be lower than the bottom of the previous gear. |
| For example, the RPM range of 3rd gear is 5400-7500. So when shifting to 4th gear, you wouldn't want the revs to drop down below 5400. Cars generally make more HP at a higher RPM, so when the revs drop, the car is making less power and valuable time is lost as the engine works to bring the revs back up into the powerband. This condition is even worse when dealing with cars that have small engines that don't make a lot of torque, and rely heavily on high revs to make power (like my S2000). Upshifting and having the revs drop too low makes the car bog down and kills your lap times. |
| As an additional pont of interest, this is why it's beneficial to set up your gears to make as few shifts as possible, which we'll elaborate on. |
| THE DYNO GRAPH |
| Obviously you've seen your fair share of these as well if you've ever tuned a vehicle for Forza Motorsport 4 or taken your real life car to a tune shop and put it on a dyno. Knowing your dyno plot is helpful for setting up your transmission gears. The typical dyno measures Horsepower (HP) and Torque (TQ), although dynos are capable of measuring a lot of other things such as your engine's fuel to air ratio. |
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| The chart above is for our hypothetical race car with the 7500 RPM redline. The BLUE line represents engine Torque and the GREEN line represents Horsepower. This car makes a maximum of 470 lb-ft of torque at 5000 RPM. Although a vehicle that makes a lot of torque is always better than one that doesn't, we want to keep our RPM in the range of our powerband where the engine is making close to the maximum amount of Horsepower. |
| Our vehicle makes a maximum of 510 HP at 6500 RPM, but realistically speaking, our engine is making 500-510 HP between 6000 and 7500 RPM which is the range we want to keep our revs in for as much of our lap as possible, (as indicated by the top of the HP curve). |
| As such, we want to be intelligent with our shift points on the track and set up our gears so that our revs don't drop too low. In my opinion, 3rd and 4th gears are generally the most important since we spend the most time during a lap in these gears and are downshifting from 4th to 3rd, and from 5th to 4th in the majority of our corners. |
| Also as a good rule to follow, try and keep your upshifts in the straights to a minimum. Every time you upshift, the shift itself takes time, and your revs drop so the engine is making less power. That said, it's best (for example) to make 5th gear a little longer to reach your braking point, rather than going to 6th gear to get there. |
| Another thing to remember, (especially if you've read 'Tune To Win') is that Carroll Smith says of cornering ability, straight line acceleration, or top end speed, that straight line acceleration is the most important of the three. Our ability to accelerate out of corners will yield the fastest laps, so if we can tweak our vehicles to get a little more acceleration at the expense of top end speed, we should do it. This is clearly contingent upon the track we're driving, and on most tracks we're rarely, (if ever), hitting our vehicle's top speed. |
| I'd also like to add that since there's a myrid of tuning options in the 'Engine and Power' menu, that we should pay close attention to the upgrades that not only add HP, but be aware of where in the powerband the power is going. Increases in low to mid range power and torque pay dividends by increasing our acceleration out of the corners. Certain upgrades, namely turbos, superchargers, and some engine swaps completely change the powerband for the better on our race cars. |