iRacing

Connection Type

The Connection Type selection in My Account controls the maximum amount of data that the sim and the race server will exchange with each other. The higher the setting, the more data the two are allowed to exchange (the bigger the "packet"). The bigger the packet, the more space there is available to send car information to you, and so the more likely it is that the server will send you positions for more cars.

The server has the ability to send cars to you (their positions, as well as some other information) using different levels of detail. The different levels of detail require different numbers of bytes of information to be transmitted per car. Depending on the number of cars on track, the amount of space available in the "packet", and some other factors, the server will choose an appropriate mix of the level of detail it includes with each car it transmits to you. The higher your Connection Type selection, the more likely it is that the server will choose the higher detail level for more of the cars in the field.

The level of detail sent for any given car won't have any measurable impact on your CPU usage or your frame rate.

The extra overhead of handling the larger packets that can be generated when using the higher bandwidth selections might have a measurable increase in CPU usage IF there are enough cars in the session to actually use that extra space.  See Max Cars below.

The number in the Connection Type description is what we think you should have for an actual Download speed if you want to use this selection.  However, if your ISP has a very limited upload speed, you should consider that as well.  The actual figures are as follows:

Maximum bit rates for various connection type options.

Slightly higher for IPv6, due to the increased packet header sizes.  Current as of 2018-09-10.  Satellite connections are not supported.

For the higher selections, the rates are only hit for extended periods of time if you are in a dense sessions (60 cars on track), though those rates can be reached sporadically during the session, even with fewer cars.

Considerations for picking the right Connection Type

• What else will be using your Internet connection while you're racing?  Windows itself?  Other applications?  Other devices on your network?

• Does your connection actually deliver your advertised speed consistently?  Most advertised connection speeds (here in the US anyway) are complete fantasy.  speedtest.net can give you small snapshots, but it's hard to judge the variance from a few samples.

• Is your computer is fast enough to deal with all the extra work it has to do when being fed the extra data.

To set the connection type for your account, go to iRacing... Account-->My Account.

Then scroll down to the Preferences section and choose the appropriate option from the Connection Type drop down.

This change will not take effect if you are currently in the sim.  If you are in the sim when making this change, you will need to exit from the session and relaunch the sim to join the session with the new connection type in effect.

Max Cars

The Max Cars setting on the options/graphics page tells the server to which you're connected to not send you any more than the selected number of cars. If you have this set at 15, and there are 60 cars in the field, you will only ever be given positions for 15 cars at any one time. Over time, as you move through the field, the particular set of 15 cars will change - you will generally be given the 15 cars that are closest to you, biased more towards cars that are in front of you.

However, having it set to 63 does not necessarily mean that you will be transmitted all 60 cars in a 60 car field. It takes some network bandwidth to send each car to you, so the actual number of cars you will be sent will depend on a number of factors. The biggest controlling factor is what you've chosen as your Connection Type in the My Account section of the member web site.  See explanation above.

The number of cars that get transmitted to you will have a very measurable impact on both CPU usage as well as frame rate. All of those cars have to be moved through the world, they make sounds, they can be collided with, and they have to be drawn on screen (see Draw Cars/Pits below).  With the slowest connection type selections, the packets will not have enough space for the server to send all of the cars in a large field to you, regardless of what you have set Max Cars to. This is why the higher bandwidth connection type selections are labelled "requires fast computer" - you can end up having more cars sent to you, and it takes more CPU and GPU power to deal with them.

Draw Cars/Pits

Two new drop lists of presets have been added to the Graphics and Replay settings to control the maximum number of cars and pit objects to be rendered in mirrors and in the main view. The presets control the following settings inside Renderer INI files. Reducing the number of objects rendered, especially in the mirrors, can substantially improve frame rate when racing with large fields. These settings my be set differently for in-car vs replay. Note that the pre-existing setting, "Max Cars", specifies the requested number of cars to be transmitted to your client from the race server. These new settings are separate, and indicate which of those cars are to be rendered. All of the cars transmitted will be available in the replay, even if not rendered while the replay was generated. So you can race with only 30 cars visible, but enable all 60 later when watching he replay, for instance, as long as they were all transmitted. The new settings are as follows:

[Graphics Options]

MaxPitObjsToDrawInMirrors=20

MaxPitObjsToDraw=40

MaxCarsToDrawInMirrors=18

MaxCarsToDraw=30

[Replay Options]

MaxPitObjsToDrawInMirrors=20

MaxPitObjsToDraw=40

MaxCarsToDrawInMirrors=18

MaxCarsToDraw=30

Note on replays

Since the Max Cars setting only controls the number of cars the server transmits to you, not the number of cars that get drawn, its value is meaningless when watching a replay. If someone saved a replay from a session with a large field while they had Max Cars set to 63, and you go to watch their replay, your computer will display all of the cars in the replay, regardless of what you have Max Cars set to.