Forza Motorsport 5

Just an addition to the other awesome guides here.
Found a faster method which requires very less effort.
Works on the latest patch where are Drag races were added.

What you want to do is, race with a dummy account, whcich has your tuning setup and design on the car. In free play.
Instead of using Circuit races select Drag (by pressing 'right' at the Game Oprtions -- Game Type)


Game Type: Drag
Max AI: 1
Drivatar Diff: your choice
Car: Any
Drive Type: Any
Assists: you want to select Automatic shift

What I did:
I taped down the RT and watched some movies on my other TV and just selected Restart.
Takes about 1:00 minute to complete 1 race including all loading screens.

EDIT::: You have to do at least 80-100 races in one DAY ( I think the Forza Server counts from 7pm PST- to 7pm PST next day) to get credits for the races.

I made 330 races in ca 7-8hrs and earned 70k for tuning and 25k for desings.

Here's what I did:

I saved a tune that I did nothing to for one of the starting cars, I then signed out and on a second profile downloaded the tune and did this:

Free play
Top gear west
Circuit race 1 lap
1 AI

I did 49 races, hitting restart at the end. 24 hours later I received 19cr on my profile unlocking the first two achievements.
So I repeated the process but only did 45 races and this morning received 14cr and unlocking the achievement.

So secondary account bang out 100 races using your tune should be just over 2 hours and in the morning you'll unlock all 3 tuning achievements.

Hope it helps, I found this to be the quickest way







TheSaucyGibbon adds some great tips/alternative solution. Thanks and credit goes to him for the following:

(This assumes that you have created your design and tune and have previously applied them to your boost account vehicle)

1. Switch off your Kinect sensor, it will try to recognise you and log you in on your normal profile.

2. Be sure that your normal profile is logged out.

3. Log in as your boosting profile.

4. Grab a pen and paper.

5. Start Forza, go to Free Play.

6. Select track : Top Gear / West Circuit

7. In Game Options, change max drivatars to 1, laps to 1. All else leave alone.

8. In Load Tuning Setup, search for then 'download and install' your tune again (just in case).

9. Start Race, track will load. Watch that loading thingy go round and around in circles for some time.

10. At Pre-race, start and FULLY RACE your first race. Sorry about the shouting there.

11. At Post-race, scroll across and select 'Restart'.

12. At Pre-race, select 'Start race'. While the race is loading, grab your pen and draw a short vertical line on your piece of paper. This is your record of having done one race.

13. As soon as you see 'GO', press your 'start button' to pause the game. Scroll all the way across and select 'Quit Race'.*

14. If you have 120 pen marks on your piece of paper, go to Step 15. If you have less than 120 pen marks, go to Step 12.

15. Congratulations, you can stop now until your next session tomorrow

Since there is no storefront to offer tunes, there is a bit of confusion about how to earn money from them, and ultimately win the tuning achievements. For me, it was part luck, a small part skill (quite small, really), and a larger part how it's presented. Here's a few tips:

1) Make tunes, but don't mass produce. Ok, obvious, but more tunes means more ability for others to find them. Find a car that has access to multiple classes, and tune them to the top of those classes. Don't just save multiple random tunes and hope for the best, because bad tunes will not receive likes, and you as a tuner will be rated lower overall and show up less often in others' design recommendations.

2) Don't ever sacrifice quality. Mass production has a tendency to try to save as much time as possible in favor of pumping out lots of numbers. Don't fall into this trap, but instead try to tune your components to run optimally for a specific condition. For example, shorten the gearing and turn up the downforce on short tracks with lots of corners. You don't need high top end speed for a track that doesn't have a long straightaway. Likewise, do the opposite for longer tracks. Then, label your tunes in the descriptions and the keywords so that users know what they're getting.

3) Description is key. People are more likely to download and ultimately like a tune that meets a description, and also more likely not to like a tune that doesn't perform a function well, or doesn't do what the description states. The beauty of Forza is that a function specific setup will vastly outpace a car that is intended to perform well as an all 'rounder. An all-around tune is likely to perform poorly for all conditions by comparison, despite the intent to make it do well for everything. The most important words belong in the front of the description. Be clear about what the tune accomplishes in the first sentence because most people's attention span will only last a few words. You have a very short amount of time to get your message across. Protip: Set up SmartGlass
for Xbox One and use your PC to type out descriptions through the remote function.

An accumulation of likes will get your rating higher, which will help to get you noticed. The payments you receive, however, are based on usage in the past 24 hours. The more others use your tunes, the more you'll be paid. An accumulation of more than 30k credits will pop the achievement.

As far as my own tunes, they are on cars like the Ferrari 458 Italia -- It's a car that is relatively affordable early in the game, but can max out A, S, and R classes. That's three of the most popular racing classes, on a popular car where people are likely to seek better setups. Find those cars, spend time on their setup, benchmark them, test them, and then share the heck out of them!

Leave feedback for me in comments to help improve this solution if you think there's something that needs to be changed.