How is timing controlled on the 800?

[Dartos]

I am wondering how the ignition timing on the current 800 RMK works. I've read a lot on the forums about higher compression heads, different pistons and other performance modifications. I want to know how the ignition timing is controlled.

Is it controlled off of engine RPM and throttle position only? Or are there other parameters that are read by the ECU? Such as outside air temperature barometric pressure? Since there's no O2 sensor I assume that this is an open loop system?

Does the timing need to be advanced or retarded to get the most performance out of a high compression head or different pistons?

 

[sledstew]

The ECU tells the engine when to fire based off of tps and rpm is the simple answer. Remember the flywheel ,and signal from trigger play a role in firing also. Some other things to think about-- timing may be retarded if engine gets to hot --many many things an ecu can do to retard or advance timing to many to list.

Pistons- I would say have minal effect on timing unless you go to a different bore or something of that nature.

Head could have an effect on the ignition timing just slightly ,in most cases big bores porting etc the gains are minimal by changing ignition timing 2-3 hp.

Ignition timing is a touchy subject and should not be messed with unless you really know what your doing , way safer to be a bit retarded vs to much advanced.

Different fuels have a major affect on how much timing you are able to run also, here is my suggestion if you want to make more power dependent on elevation the higher you go the more timing you can run,the higher the octane the more timing you can run.

Give me a call and Ill give you a good idea to try that works really really well.

Jake
701-202-6304

 

[Vertical Asshauler]

Any good performance parts are designed to run with the stock ignition mapping. By adjusting it you will only introduce problems or make less power.

 

[gman086]

Any good performance parts are designed to run with the stock ignition mapping. By adjusting it you will only introduce problems or make less power.

For the Pro I would agree but there have been plenty of circumstances where that is not the case like the Doo Series III motors that benefited hugely from advancing the ignition timing up top and retarding in the mids. It does require sophisticated equipment too change (I had to send mine to the BRP Race Dept) but it is doable.

Also keep in mind there is a difference between changing the "port timing" (which nearly all of these "fix" kits do as best as I can tell either by adding a cylinder shim or changing the piston pin mount location and building a custom head with more space) and changing the ignition timing. A port timing change and compression adjustment can have very positive effects on HP output (poor mans port job).

Have FUN!

G MAN