Rank: Driver's Permit
#1 Posted : Wednesday, February 4, 2015 8:42:51 AM(UTC)
sorry about making a thread about this quick question..but i found this question hard to search for..

are all/most of the engine upgrades just numbers? say for example Displacements.....it says it reduces friction and inertia (i assuming within the motor..so it shakes the car less? and allows for a wee bit better handling?)...

i know camshaft upgrades actually affect the RPM range..as I can see it immediately on the graph...

another way to put my question is...does the game "simulate" the parts of the engine, whereas there are some parts that are more synergistic together(when upgraded) like i suspect Camshaft and Valve upgrades actually produce more power in the higher RPM range...As in if you are trying to increase power mainly in the high RPMs

or does the game just see it as a set of numbers...and you just choose which ones you think you need most...(such as HP and less weight? or HP and more weight, with little Performance Index increase)

thanks alot
Rank: B-Class Racing License
#2 Posted : Wednesday, February 4, 2015 10:06:08 AM(UTC)
Originally Posted by: Lunchbox486 Go to Quoted Post
sorry about making a thread about this quick question..but i found this question hard to search for..

are all/most of the engine upgrades just numbers? say for example Displacements.....it says it reduces friction and inertia (i assuming within the motor..so it shakes the car less? and allows for a wee bit better handling?)...

i know camshaft upgrades actually affect the RPM range..as I can see it immediately on the graph...

another way to put my question is...does the game "simulate" the parts of the engine, whereas there are some parts that are more synergistic together(when upgraded) like i suspect Camshaft and Valve upgrades actually produce more power in the higher RPM range...As in if you are trying to increase power mainly in the high RPMs

or does the game just see it as a set of numbers...and you just choose which ones you think you need most...(such as HP and less weight? or HP and more weight, with little Performance Index increase)

It is my understanding that just the numbers matter. So if you can get
thanks alot


Rank: C-Class Racing License
#3 Posted : Wednesday, February 4, 2015 12:28:25 PM(UTC)
Your quote messed up a bit :P but I agree that mainly the numbers matter. Building a car as light and as powerful as possible is key to having an optimal build, but just like anything else, there are a few exceptions to that.
Rank: A-Class Racing License
#4 Posted : Wednesday, February 4, 2015 1:12:08 PM(UTC)
No, the game does not take that into effect, its really just power and weight.

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#5 Posted : Wednesday, February 4, 2015 1:12:22 PM(UTC)
Originally Posted by: The Bulin Wall5 Go to Quoted Post
Your quote messed up a bit :P but I agree that mainly the numbers matter. Building a car as light and as powerful as possible is key to having an optimal build, but just like anything else, there are a few exceptions to that.


okay thats pretty much straight forward...i was hoping that i could use certain upgrades and influence the engines' characteristics a bit (tho i don't know squat about how engines really work...but it would have been fun to experiment)

thanks for the reply

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#6 Posted : Friday, February 6, 2015 7:12:17 AM(UTC)
Here's an excerpt from a writeup I did on Forza engine building for a Focus website I'm on. Most of the info is based on real-world tuning and not all of it will directly correlate to tuning in Forza.

"ENGINE BUILDING FOR CIRCUIT RACING:

It's very tempting in Forza to slap a bunch of parts on a motor and make huge horsepower numbers believing it will make the car faster. It's also one of the more frustrating aspects of the game because it seems to work more often than not.

Realistically, the shape of the power curve, the area under the curve, the powerband range, and the gearing determine how an engine performs. DSport Magazine published an article called Learning Curves written by Allan Lockheed, Jr., who developed a race engine design program called Engine Expert. Engine builders use it to design parts with manipulating the power band in mind. I'm going to try to relay the relevant information as it pertains to Forza tuning.

PARTS: There are different trains of thought when it comes to parts choice. For a while, I was only picking engine parts that also reduced weight thinking power-weight ratio was the most important thing. Then, I came across an article on dyno graphs and began to change the way I build engines.

As noted in the article, the first thing you need to figure out is "what is the engine going to be used for?". Since ours is for circuit racing (and not drifting or rallying), we want good low-end torque for acceleration and good top-end horsepower for overall speed. Basically, cake and eat it. Many engines will have one or the other covered, requiring you to build the other end up.

Here are some of the parts you can add to change each end of the power curve:

LOW-END TORQUE: increased displacement, pistons, superchargers, intake and exhaust
TOP-END HORSEPOWER: race cams, turbochargers

While it is easier to pick a car that already has a good powerband, it is possible to take a car with poor characteristics and make it better.


ENGINE BUILDING FOR CIRCUIT RACING (CONTINUED):

To make this explanation as coherent as possible, I have created a .jpg drawing with some labels that I will reference in subsequent engine (and some gearing) posts.

POWER CURVE/POWERBAND: Below is the power curve for my A600 BMW 135i build. The orange horizontal line connecting points B and C highlights the powerband. When adding parts to an engine, you want create a wide powerband (as much space between points B and C as possible).



So, how do you use a dyno chart for tuning? Well, when you shift from one gear to another, there is potential to upset the balance of the car. To maintain stability when shifting, two key ideas (both found on the dyno chart) should be observed:

1. Always keep the engine speed above peak torque (POINT A).

2. Time the shifts so that power at the up-shift recovery point (B) is the same as the shift point (C).

Although it is sometimes incredibly difficult in Forza, I try to follow this advice when building engines and adjusting gearing.

Following the guidelines above, I should never let the revs drop below 2000 rpm (no problem in the BMW 135i) and always shift at redline. However, this puts me below the ideal up-shift recovery point (5800 rpm) due to the rev drop experienced during shifting.

I have 3 options to remedy this rev drop:
1. I can extend the rpm range with cams (race cams already installed).
2. I can add parts to make the car change gears faster (race clutch already installed).
3. Or, I can shorten the gearing (will be discussed in the gearing post).

AREA UNDER THE CURVE: A car with more area under the power curve within the powerband will put down faster lap times than a car that is peaky or one with maladjusted shift points. Some of my high-horsepower builds have had somewhat peaky power curves because I was adamant that they have exactly 1,000 hp. This makes them fun to drive in a straight line at high rpm, but not-so-fun while going around a curve at lower rpm. In the end your goal should be to have the widest powerband possible (i.e. - the greatest distance between points B and C) and then match the gearing accordingly."

Edited by user Friday, February 6, 2015 8:46:39 AM(UTC)  | Reason: Not specified

Rank: C-Class Racing License
#7 Posted : Friday, February 6, 2015 9:33:52 AM(UTC)
A lot of that doesn't hold true to the game because it's just that.... A game. It isn't real life, and some things work differently. Getting the biggest bang for your buck with upgrades is pretty much all you have to worry about. If your car has a good powerband, keep the transmission stock. If it's peaky, go with a sport transmission, or even race if needed (like a Honda Civic, for example). That's pretty much all you need to know.
Rank: Racing Permit
#8 Posted : Friday, February 6, 2015 9:42:09 AM(UTC)
I did similar writeups for gearing and suspension, but the same holds true and not all of it can be applied to the game. I'm hoping Forza 6 extends the tunability and goes into more detail in each category, especially with their "promise" of the game being more technical.
Rank: C-Class Racing License
#9 Posted : Friday, February 6, 2015 2:19:13 PM(UTC)
Originally Posted by: RedZedX3 Go to Quoted Post
I did similar writeups for gearing and suspension, but the same holds true and not all of it can be applied to the game. I'm hoping Forza 6 extends the tunability and goes into more detail in each category, especially with their "promise" of the game being more technical.


That would be ideal. Using 12.0/12.0 rebound and 1.0/1.0 bump stiffness for lower class just gets old despite it working so well when it shouldn't.
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#10 Posted : Friday, February 6, 2015 2:31:32 PM(UTC)
Originally Posted by: The Bulin Wall5 Go to Quoted Post
Originally Posted by: RedZedX3 Go to Quoted Post
I did similar writeups for gearing and suspension, but the same holds true and not all of it can be applied to the game. I'm hoping Forza 6 extends the tunability and goes into more detail in each category, especially with their "promise" of the game being more technical.


That would be ideal. Using 12.0/12.0 rebound and 1.0/1.0 bump stiffness for lower class just gets old despite it working so well when it shouldn't.


I haven't tried anything like that in this, Forza 3, or Forza 2 despite hearing that it works. Also heard about maxing/bottoming the ARBs in opposite directions. I guess that would work in autocross as I know a few guys that completely remove their front bar in the FWD cars.

In reality, good production-based race cars use around a 65% damping ratio, so that's where I start. Most of my prototypes and other R3s have a 70 or 75% ratio. It works with most cars, but not all. I've heard tuning is much more important in FM5 and assume it will transfer over to FM6.

Rank: C-Class Racing License
#11 Posted : Thursday, September 10, 2015 2:25:43 PM(UTC)
Upgrades do effect each other.

Try this: Upgrade the exhaust of a stock motor. Let's say it gives you 10HP

Now, revert back to stock exhaust.
Go and upgrade your cams and your valves; maybe even your pistons/rods while you're at it.

Now, go back and re-apply that same exhaust upgrade and you'll get more than 10HP out of it this time.

Forza has been doing this for a while. I noticed it in FM4.
There's no special order you have to do upgrades in, but some do alter the power gains from others.
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