This calculator is based on desktop data and so uses theoretical formula to calculate 'ideal' results.

The real world is anything but ideal and in reality will yield slightly different results. This is why it is important to tune your engine and make jetting decisions based on measured AFR, rather than internet jetting recipes (like this one)

You can also tune your engine for different applications - The setup you would use for a land speed car that operates at WOT for miles at a time will be VERY different from a daily driver.

The results given here do not take into account your application and are provided as a guide only.

The choke size determines the air velocity through the carburettor. It also sets an upper limit to the maximum air flow that the carburettor can flow.

Smaller chokes are much more responsive as they have higher velocity at partial throttle, and so are ideally suited to daily driver or street car. Whereas larger chokes have lower velocity but are less restrictive making them more suitable for WOT applications.

You can generally tell if your chokes are too large as when you stamp on the gas pedal your engine dies from a lean-inrush where the inrush of air causes a high volume but low signal. This causes the car to stumble. Increasing pump jets can mask this issue, so if you have been increasing pump jets in an attempt to overcome a stumble, it is likely that the actual issue is that your chokes are too large.

When you consider that the stock DCOE choke size is 32mm, you will essentially need to change them for all AMR500 applications. 

Our DCOE's are supplied with custom made chokes of the correct size for the application.

Apart from the fact that EVERY engine is unique and so generic jetting recipes will almost certainly not be correct for YOUR engine. 

Generally online jetting recipes are based on one-barrel-per-cylinder calculations. The problem is that when used in a siamesed application (two barrels per cylinder) the velocity is effectively halved.

This calculator is a starting point ONLY. We always recommend that you tune your carburettor properly using an AFR meter and suitable load. 

We supply all of our kits with full instructions on how to tune your engine using an AFR meter. This is a simple step-by-step process. We also provide helpdesk support to help you should you get stuck. Just one of the great reasons to buy our products.