| TRANSMISSION TUNING FOR FORZA MOTORSPORT |
| Most simply put, when we tune our transmissions we're looking to accomplish two objectives: |
1- Keep the number of shifts to a minimum, especially in the straights. |
| 2- When we do shift, (especially downshifting in the corners) we want to come out of the corner and apply throttle with the revs in the fat part of the powerband. And we want the same with our upshifts. |
| Let's illustrate by taking our gearing info from the transmission chart and plot it on the dyno graph to see how much power we're making every time we upshift: |
| 1ST GEAR : 0 RPM - 7500 RPM 2ND GEAR: 4800 RPM - 7500 RPM - Red dot 3RD GEAR: 5400 RPM - 7500 RPM - Blue dot 4TH GEAR: 5700 RPM - 7500 RPM - Brown dot 5TH GEAR: 6000 RPM - 7500 RPM - Purple dot 6TH GEAR: 6200 RPM - 7500 RPM - Orange dot |
 |
| Let's assume that we're hitting our rev limit before each shift, so at 7500 RPM we're always making 500 HP. That means in our shift from 1st to 2nd we're going from making 500 HP to 425 HP at 4800 RPM and won't get back up to 500 HP until our revs climb to 6000. |
| Additionally, as we progress through the gears, our shift from 2nd to 3rd has us dropping from making 500 HP at 7500 RPM to 480 HP at 5400 RPM. Without going through the remaining gears on the graph, we can clearly see that upshifting costs us time and horsepower. |
| MINIMIZING UPSHIFTS |
| In order to keep our upshifts to a minimum, we need to match the length of our gears with the length of our straights on the track. |
 |
| In the diagram above, our race car with the 7500 RPM limit takes the first turn in 3rd gear. About 1/3 of the way down the straight we need to upshift to 4th gear, then before our braking point we hit the rev limiter and need to shift to 5th. We'd rather not shift to 5th because we're going to brake soon and have to downshift for the turn anyway. In this instance we want to LENGTHEN 4th gear until we're just about to hit the rev limit at our breaking point, so instead of upshifting to 5th we downshift for the next turn. |
| It should also be noted that since all straights are not of equal length, it's impossible to set 4th gear (as illustrated in this example) to hit the rev limit at the end of each one. If you've decided to run only 4 gears for this particular circuit, set 4th gear to rev out at the end of the longest straight on the track. |
| THE CONSEQUENCES OF THE INDIVIDUAL TWEAK |
| As I'm sure you're aware, you always have the option to tweak the transmission as a unit in the direction of SPEED (longer gears) or ACCELERATION (shorter gears) by sliding the Final Drive. If you're a noob, you might want to stick with this method until you get a feel for tuning your transmission. |
| If you move the Final Drive to make 4th gear longer, all the gears will be longer but the RPM range of each gear will remain unchanged. Instead, the gears will rev up slower and the MPH that can be reached in each gear will be higher than before. Hypothetically, 2nd gear - which ranged from 4800 to 7500 RPM and from 55 to 85 MPH will still drop down to 4800 RPM but will take longer to rev up to 7500 with a top speed of 95 MPH. |
| If you lengthen 4th gear by itself, a lot more stuff will change. The RPM range of the gear will increase which means that at the instant that the shift is made, 4th gear will start at a lower RPM than before, and there will be a greater drop off in horsepower. The gear will have a higher maximum MPH, which is what we want - to avoid an upshift to 5th on our straightaway. 3rd gear will remain unchanged but 5th gear will be shorter. To avoid a significant drop in HP from 3rd to 4th, you can choose to lengthen 3rd a bit to balance things out. |
| GEARS AND TURNING RADIUS |
| We spend a lot of time trying to get our cars to turn in better by adjusting our springs, ARBs, toe, and what have you. But a lot of people who play Forza don't pay enough mind to how powerful a tool the gearing tweak actually is when it comes to reducing your vehicle's turning radius. |
| Pay close mind to this: Lower gears turn in better than higher ones but carry less corner entry speed. |
| My all-time favorite example of this is after the first turn (the long sweeper) at Suzuka Circuit. The first turn is a 3rd gear turn, then right before you get to the 'esses' you usually have to upshift to 4th gear. Try it in 4th gear, then after some laps, lengthen 3rd gear enough so that you can get through the entire section without an upshift. The car will turn in more sharply and transition in a noticably tighter radius than it did in 4th gear. |
| I always consider this when setting up my gears. If I'm sort of in 'no man's land' between gears in a corner, need a tighter tun in and can gear down, I'll do it. Generally speaking, gearing down from 4th to 3rd isn't a problem, but gearing down from 3rd gear to 2nd on those lower speed corners, (where you could get away with either) can be tricky on exit if you don't exercise throttle control. |
| Keep in mind that when in a lower gear, the engine revs higher at a given speed, and there's more available power in reserve coming out of slow corners than faster ones. Take a corner in 2nd gear, then next lap take it in 3rd. You'll get more wheelspin coming out of the same corner in 2nd. 3rd gear is more stable and more forgiving, but for a given exit speed (with adequate throttle control) you'll accelerate out of that corner faster in 2nd. |
| Back in the days of Forza 2, this transmission trick was a reason why Leader Board guys could get around the track in 1000 HP muscle cars on skinny street tires, and you couldn't. (The other reason is they're better drivers than you, but that's besides the point). But the trick was to make 4th gear really, really long and run the entire circuit without downshifting. The wheelspin was much more managable in 4th gear than if they had to navigate those slow corners in 2nd. And since the cars made so much power, and had so much low rpm grunt (they were torque monsters) they still accelerated well despite the one gear being so long. |
| HOW MANY GEARS SHOULD I RUN? |
| This is a question for the ages. Unfortunately there's no fixed set of rules to go by. Generally speaking, I found on most of the full circuits that 5 gears was adequate, and I rarely felt the need to run a 6th gear. Considering how short a 6th gear is in relation to 5th gear, my attitude was to make 5th as long as I needed to get down the longest straight on the cicuit and save myself an extra shift. |
| If you're dealing with the short circuits like Tsukuba, where there isn't adequate length on any given straightaway to get to the higher gears, 3 or 4 speeds should be sufficient, but it's dependant on the track and how the car makes its power. |
| If the issue for you on the full circuits is whether to run 4, 5, or 6 gears, a good rule is to examine the HP-TQ curve of the vehicle you're tuning. A good initial indicator of cars that can get away with running less gears is how much Torque they make in the low to mid range of the powerband. Cars that make a lot of low end torque with low redlines (around 7000) are better candidates to run less gears. The reasons being that the less gears you run, the lower your RPM will be coming out of corners, and the lower your RPM will drop when you upshift, because the gears will have to be a lot longer. You need a lot of low end grunt to get the car moving out of slow and mid-speed corners to fight off the rotational inertia that is the by-product of the engine's RPM dropping down on the powerband. |
| By comparison, there are certain cars with really steep HP-TQ curves that make all their power on the high end of the rev range and are torque starved in the low to mid range of the powerband. Cars that need high revs to make power are generally smaller engines, like the 4 cylinder variety, and generally have a higher redline (like the 2.0 liter - torque starved AP1 S2000 which has a 9000 RPM). These cars need to keep the revs high to make power, especially coming out of lower speed corners. These are the cars that perform best with more gears. |
| Cars with a lot of low end grunt genearlly have the big block motors you'll find in Corvettes and Vipers. Regardless of the vehicle, low-mid range power is always appreciated. Improving the hp/tq curve is done in the upgrades garage. If you have a small, high revving engine, you don't want to add parts like camshafts that raise the redline. Other parts are better suited like turbos and superchargers, they significantly change the powerband for the better. And don't forget to check out the engine swap option when available. Sometimes swapping motors is a huge improvement. |
| Look at the graphs below from the old Forza 2 days. The INGS-RX7 had a ridiculous curve, I mean, look at that freaking thing. It's making 550 ft/lbs of tq at only 3000 rpms. This is a car you could run less gears in, because as long as your revs on shifts weren't dropping below 3000, you were golden. The graph on the right is the INGS antithesis. It makes no TQ at all, and needs high revs to make power with an 8900rpm redline. If you ran only 4 gears on this car and the revs dropped to 3000, you'd be getting murdered coming out of a corner in 2nd gear. This car you'd want to keep the revs as close to 7000 on your shifts as you can. |
 |
| Drive the car with the stock gearing and feel it out. Then drop a gear and run some laps. Less gears mean less shifts which is good, but also means longer gears which can impair acceleration. If the car feels like it's bogged down coming out of the corners, put the gear back. If the car is quick with 5 gears and you want to drop another gear, lengthen the remaining 4 gears until the top of 4th gear is hitting the redline at the end of the longest straight on the track. Then try it out. Once again, if the car feels bogged down coming out of the corners, put 5th gear back and set it so that it's hitting the redline at your braking point at the end of the longest straight. Pay attention to your revs coming out of the corners, if they're too low, you need to add a gear or tweak the gearing be it the FD or the individual gear. |
| And lastly, don't be shy about going back to the garage and swapping out parts for better acceleration if the car isn't up to snuff. |