I have been thinking about making this thread for ages. and now I finally got around to it.
Now there is a great tuning guide by Worm, There is bunch of great open souce tunes by various people, But therre isn’t any sort of guilde on how to build a car. I’m trying to fill this hole, not completely and everyone has to still decide their builds theirselfs, I’m just throwing some general advice, and pointing what yuo should think when building a car. There will be no if you have X amount of something you need X amount of other thing to survive, this is more general guilde. and it comes from what I think when I’m in a process of building a car.
So withuot further ado, let’s get to the guide.
So what is the best way to upgrade a car in Forza Motorsport series. (Also applies to Horizon games to some extent)
Well to put it simply it is the way that uses least PI for most benefit.
First of all, we need to know how PI is determined.
In current games PI is determined by putting the car running a “test track” driven by AI, and the time it uses to finish the course determines the car’s PI We don’t exactöy know what kind of a track it is but it has been speculated that the track is somewhat similar to silverstone track, But only T10 developers know what kind of a track it exactly is. How ever what kind of a track it is, isn’t exactly too relevant.
Then we need to know how the AI drives, and this is crucial to making a good car. Therefore we need to think how AI drives.
-it never wastes time on wheelspin, lock up the brakes, or slide. no matter how the car is built (unless if the car has silly tune but that is not the case as the AI drives with default tune always)
-it uses the suggested line.
-automatic shifting
From these we can tell that
-the braking is always optimal therefore better brakes do not have too much effect
-the cornering is always ideal, therefore suspension, differential, antirollbars, and chassis rigidity is not essential, unless the car has really bad default suspension setup
-it shift’s automaticly, therefore it want’s to have more power than actual handling. and it benefit’s greatly from gearbox, and clutch upgrades
And then we have one key feature.
Due automatic shifting it rarely uses the engines full potential, as on automatic it will shift right before redline, while in some engines the power is above the redline, and some engines the power is clearly below the redline.
-Therefore the AI never uses the full potential of the engine, unless the engine has “ideal” power range for automatic shifting.
And now we get to the actual guide.
So what parts I should use
Let’s start from basic’s
What is the number 1 most beneficial upgrade to almost any car
It is weight reduction. it benefits 1.Acceleration 2.Deceleration 3.Handling
therefore by making the car lighter you will improve everything else except top speed
Therefore weight reduction is the best upgrade to just about all cars. and it shuold be the first thing you do to any car you are starting to upgrade.
Although there is such thing as “too light” althuogh this rarely is the case in Forza games, and only couple of the lightest cars are affected by it.
Then as we already noted in the opening, the adjustables Brakes, Suspension, Antirollbars. Differential.
As we already noted the AI driving doesn’t know how to take full potential from them, therefore they are the best upgrades you can get.
Now that basics are out of the way, we start looking how to get the best possible combianation of the remaining parts.
Tires and Wheels
Width / Compound / Tire profile / Wheel weight
Compound and width, which to choose
Wide tire with low grade compound is the way to go for dry track. it will provide good grip most of the time, while not being “snappy” in other words it starts all the slides gradually, and ends them smoothly therefore it’s easy to control in all situations. and almost always it’s cheaper in PI scale.
Narrow tire with high grade compound is the way for wet track. the reduced traction of the wet surface will dampen the snappiness to reasonable level, and narrow tire will not cause too much drag going trough the puddles, which makes it more stable than wide tire.
Wheels.
Wheels are rotational mass, and unsprung weight. Again less is more. The less unsprung weight you have, the more stable the car is. and the less rotationall mass you have, the sharper your braking and acceleration is.
If you have issues on locking up the brakes, heavier wheels might actually help you, but at the same time it will have same effect on acceleration, and might even cause you to stall if you have long first gear, or low torque engine.
Tire Profile
While increasing the rim size you will increase rotationall mass, you also make the tire sidewall smaller, and therefore there is less flex, which leads to sharper, more responsive handling, How ever on the flipside if you have too low profile it has again negative effect. The thing is that high profile tire is slow to react, but it also is smooth when it starts to slide, and smooth when the slide ends. while low profile tire snaps loose fast, and regains it grip fast, which makes it difficult to deal with.
My personal preference is around 35-55 tire profile, you might want to use it, or not.
There is also one way to “abuse” the PI sysem here. By fitting very large rims to low end car. you can often shave rather large amount of PI due increased weight. and currently almost every E class leaderboard car is running with extremely large rims and low profile tires. Due to the grip levels they have to the power they make, they hardly ever have grip issues. Therefore it’s often beneficial to increase weight here, to get something else in to the car.
Drivetrain
Clutch
Avoid it always and every time. it helps you only if you drive on automatic or manual without clutch, and even then leaving it out is faster.
This is again due how PI is determined. AI driver which tests the car for it’s PI will drive on automatic gears, and clutch does benefit the AI grately, and that is the reason why it will only slow you down. Only reason to ever use this part is when there is no other way to balance the PI to get to the desired PI when you have 1 PI to spare.
Gearbox
Stock gearbox is most of the time good enough when talking from more modern cars, there is some cases when it’s not enough. It’s usually best to avoid gearbox upgrades due them being PI expensive, and they are PI expensive due reduced shift time where the AI driver benfits a lot, but as said you do not. Specially if you are driving manual with cluth.
How ever here is few examples of benefical gearbox upgrade.
Street gearbox is great for classic muscle cars. it’s 5 speed unlike the stock 3 or 4 speed gearbox which most of the time tops out way too early. even though the stock gearbox most of the time would be good enough, due huge torque of those V8 engines. Also it most of the time lowers the PI cause the car loses acceleration. Therefore it’s extremely beneficial to use this street gearbox.
Sport gearbox. Most cars have actually extremely good gearboxes and if the car has street gearbox option this gearbox gives you those ratios, but with adjustable final drive. How ever, it is most of the time huge PI hog and not worth it, unless you have engine swap, or you have used Camshaft upgrade and that has skew’d the original gearing.
Race gearbox. While I would like to say “avoid at all costs” due it being extremely benficial gearbox for the AI test driver, it does have use. In case of 2.0 VVT engineswap, -97 Civic stock engine, and 2 rotor roary engines they all have one downside. The engine is absolutely worthless unless it’s on very high RPM range. and even though most stock, sport and street gearboxes are fine they arent always enuogh, and just can’t keep it there due too long gear ratios. The cars / engines mentioned here are the only reason to ever use race gearbox, as in any other case it’s just waste of PI. the 2 rotor is the least affected, but the VTEC is so sensitive to it’s RPM that it occasionally needs the race gearing, And while race gearing as a default is exactly the same as sport is, you will have to shorten each of the gears manually. If you can’t do that, just use sport transmission.
Driveshaft
This is the part that you should use to balance the PI it has very small effect on the PI but it has surprisingly high effect on weight, specially if you can fit the race upgrade.
Engine swaps
What is a good engine and what is not. that’s what you have to think when you are swapping engines.
Why would I want to swap 5.7l V8 to Skyline. The anwser is PI again.
In the opening I explaned it.
“-Therefore the AI never uses the full potential of the engine, unless the engine has “ideal” power range for automatic shifting.”
Skyline engine is ideal for driving with automatic gears. while 5.7 V8 isn’t. and therefore the V8 is better engine (at least in game real world doesn’t count in here, and even in real world it comes to preferences and / or situations)
So what makes most bang for PI?
well let’s look what engines we have and I’ll explane why they are good or bad engines.
-2.0 inline 4 VVT. Very high revving, Best operating above redline, but it will skew almost every other car’s gearing, so you will need adjustable final drive (at least sport gearbox). Which makes it medicore at best.
-1.3 2-rotor. Same as above
-2.6 inline 6 TT. Ideal operation for automatic shifting, but provides high top end speed with medicore acceleration. Could be good for LeMans missile car.
-2.5 flat 4 Turbo. Ideal operation for automatic gears. Overall bad choise
-5.7 V8. operates best way above redline, Does not work with automatic, Ideal swap engine due low PI cost
-3.7 V6 VVT. operates best way above redline, Does not work with automatic, but might skew the gears. Overall good engine.
-3.2 inline 6. Ideal operation for automatic shifting, but it’s very responsive and easy engine to drive. While not best, it’s a good choise.
-3.0 flat 6. good operation for automatic shifting, but it’s very responsive and easy engine to drive. While not best, it’s a good choise.
-1.6 Turbo Rally. Operates best well before redline, it’s not easy engine to work with and hard to drive most of the time, but it’s very cheap on the PI which makes it one of the best swap engines.
-7.0 V8 H. it’s extremely heavy engine and it doesn’t respond too well to tuning How ever it works very well on heavy cars due to it’s really high torque. But on the downside it’s again ideal for automatic shifting. Therefore it’s medicore.
-3.0 V8 Racing. Good for automatic, very rev happy. Again difficult engine to work with, but it will provide high power if that’s what you are after.
-5.2 V10 Even thuogh having almost identical stats with 4.5 V8. this suits only heavy cars.
-4.5 V8 Even thuogh having almost identical stats with 5.2 V10. this suits only light cars.
Difference in the 5.2 V10 and 4.5 V8 is in their nature, V10 having better torque curve but being slower respoding engine, while V8 is revhappy, but worse torque curve.
-Remaining engines, you use them if you need to make big power. they are not exactly good or bad engines.
Aspiration conversion
Why choose some spesific spiration conversion? are they any good in the first place or are they just dead weight?
well there certainly is one conversion which is better than others. but let’s see what are to good and bad sides of them first.
Turbo & Twinturbo
For 2wd cars will suffer from the turbo kick, but for AWD cars it might be the the mid range torque boost what they need quite literally the only real benefit is the midrange torque boost, but its also decent option if you are in search of maximum power. twinturbo is better suited for 2wd cars but it is heavier. When building a circuit car you will probably want to avoid weight, and go for Natrually aspirated version, as that way you will lose 50-80lbs but lose only 5-15hp. Therefore most of the time Natrual aspiration has better power to weight ratio.
Poistive Displacemant / Twinscrew supercharger
Huge torgue boost troughout the rev range, and it’s heavy. Therefore it serves best for automatic gearbox, and the AI test driver, This makes it heavy and PI expensive. which makes it most worthless aspiration conversion of them all. Pure waste of PI. How ever if the car comes with this aspiration and is Front engine RWD layout (2013 Ford Mustang Shelby 500) it’s the best solution, as you probably don’t want to deal with the turbo kick with this kind of car.
Centrifugal supercharger
Operates only on very high rpm range, and is absolutely best above the redline, giving almost nothing before the redline. and the higer tier you go the more higer the effect is. Therefore its the very best way to gain power if you are using forced induction at all. the effect is multiplied when used with 2.0 VVT, 5.7 V8, and 3.7 VVT swap engines making it one of the best upgrades you can get, when you are looking for more power. Even with the disadvantage of the weight gain it still outranks just about everything else.
Engine parts
I have always preached handling over power, and the trend isn’t changing here either. Therefore I’m just listing parts in the most beneficial order here for starters. The order is, what brings higest weight reduction to lowest woeight reduction
Exhaust
Intake Manifold (if forced induction is not used)
Airfilter
Valves
Pistons
Ideal would be that with those parts in you are almost top of the class where you want to build the car or you had to play around with the the last 3 parts to get to the PI you wanted to get.
Displacement
Ignition and fuel system. Those are the next 3 parts you want to play with
Then comes Cams
Camshaft, While you get nice power boost with this one. you almost always skew your gearing with this one. and even if that wouldn’t be the case, you almost certainly will get more torque with other modifications which will impove your acceleration. Therefore it’s usually not so beneficial to use camshaft.
Exception is FWD cars, where you want to avoid the torque to reduce wheelspin, even if it would cost you the transmission upgrade. And in case of swap engine that has notably lower redline then original (5.7 V8 Skyline R34 for example) and you top out on longer straights. Also, low class light weight cars on speed / momentum tracks.
Cars like E and D class Lotus Elan and Alps/Nordschleife, and so on. In this low class you can gain time when you don’t have to accelerate from very slow speed too often, but are capeable to rev the engine high, as you have saved PI by not using transmission upgrades. The result is higer top speed.
Intercooler and Oil and cooling. is most of the time just dead weight, They will increase the top speed, but so small amount that the benefit is only noticable on last third of Mulsanne Straight on old LeMans. The oil and cooling is better of these two, and might have some benefit on pure momentum tracks, like Alps. but Prague is already too twisty for getting any benefit from that.
And the worst offender
Flywheel, While it does increase the engines responsiveness, at the same time it’s PI hog for similar reason as clutch. Use it only for balanving the PI when there is no other way to balance the PI.
Aero, Rollcage, and Drivetrain conversions
No I didn’t forget these even thuogh I havn’t mentioned these yet.
Rollcage
While adding weight, on some cars this will affect so much that just by installing it, you might think you have 1 tier higher tire compound. you need to experiment with it. How ever most FWD cars don’t like it. as for acceleration it’s just dead weight, and FWD is all about getting out of the corner.
Aero
While it does reduce your top end, it will improve your braking and cornering speed on mid to highspeed turns. you can think that if you are braking or turning in speeds over 50mph, And let’s face it looking at the top end cars on this game. McLaren P1 is truly a fast car around the track, but #1 Nissan motul autech GT-R race car which has lower PI will run rings around it if they start racing. the differece is mostly on wings.
Granted the difference isn’t that high in lower classes, but it is there.
Drivetrain Conversion
Personally I have not played around with this. I use it only if I’m pushing E class car to S class so I’m not saying anything about it.
Odditys of the PI system
As I said on the opening of the post, AI driver does not slide, or lock brakes, Therefore sometimes increasong tire width at the rear of the car will decrese PI, and other way around This happens in AWD abd FWD cars. This is because the AI doesn’t even come close to sliding the cars, and thereofre higer grip on the rear is irrelevant to it, and therefore it is “just dead weight” to it. the same effect happens with the rear wing of the car. The grip is never needed but the top speed is reduced. therefore PI is lower. And most of the time player will want those wider tires or wing. and this again is one of the best ways to “abuse” the PI system.
I’ll also note that reducing the rear wing to minimum to low end car, will not effect almost at all to top speed, compared to no wing at all. but reduces the PI by quite bit.
Edit:
Raceboy77 did an awesome video which explanes how he does things. While I don’t necessarily agree with everything he say’s. I’d say it’s worth looking in to.
