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Author Topic: Cr250 ignition advance  (Read 2575 times)

Offline jto1

Cr250 ignition advance
« on: July 15, 2016, 01:54:28 PM »
So, with esr plate, where do you all set the ignition? Do you run it at zero, retard timing or advance timing? What's the best or do you like in your experience, and why? Whats benifits from one way to the other?

Offline jwraymond6

Cr250 ignition advance
« Reply #1 on: July 15, 2016, 02:00:11 PM »
I set mine at 0 haven't tried anything else on it works good as far as I'm concerned
87 363 sphynx built by Pete @ hybrid engineering

Offline dem3500

Cr250 ignition advance
« Reply #2 on: July 16, 2016, 02:08:54 PM »
Yea mine is at zero and I just haven't tried anything else cause it runs fine. One day I might play with it.
Facebook.com/toonutzcreations

Offline hickwheeler

Cr250 ignition advance
« Reply #3 on: July 17, 2016, 10:13:19 PM »
Mine is also at zero and works good
88 hybrid 431 puma
88 (BOF Build) stock motor and oem 89 plastics
More in the works

Offline Morse250r

Cr250 ignition advance
« Reply #4 on: July 18, 2016, 08:34:03 AM »
I advance mine, but with that being said each motor likes a diff timing set up.  On the dyno I picked up 7hp advancing the timing all the way, but in the dunes / track it didn't like it and I burnt a piston.  My motor now likes about 1/2 way to wide open advanced from the stock location
Packard built puma "bad investment"
88 rb racing duner
Trx 70\'s
Atc 125

Offline Skeans1

Cr250 ignition advance
« Reply #5 on: July 18, 2016, 09:03:31 AM »
Quote from: Morse250r;68848
I advance mine, but with that being said each motor likes a diff timing set up.  On the dyno I picked up 7hp advancing the timing all the way, but in the dunes / track it didn't like it and I burnt a piston.  My motor now likes about 1/2 way to wide open advanced from the stock location

Just for giggles have you done any testing with a 125 cdi an the combo as well?

Offline Jerry Hall

Cr250 ignition advance
« Reply #6 on: July 18, 2016, 11:26:13 AM »
Quote from: Morse250r;68848
I advance mine, but with that being said each motor likes a diff timing set up.  On the dyno I picked up 7hp advancing the timing all the way, but in the dunes / track it didn't like it and I burnt a piston.  My motor now likes about 1/2 way to wide open advanced from the stock location

We see this happen frequently when testing methods are not closely simulating/generating real world internal engine and pipe temperatures.  

The time the engine is under full throttle determines the surface temperature of the piston crown, combustion chamber, spark plug electrodes, and the temperature of the gases inside the exhaust system.  

Depending upon the power the engine is developing, the time the engine is under full load usually takes about 1 to 4 seconds if the gearing is not drastically changed when testing ATVs on dynos that most shops have nowadays.  Engines like the timing advanced when the engine's internal surfaces mentioned above are not up to full operating temperature.  These short dyno runs typically simulate internal engine surface temperatures seen in engines used for 300 ft.drags and not what most recreational or long track engines experience.

At the beginning of a dyno run with the coolant temperature at 150 to 200 deg F the piston crown will typically be 200 to 250 deg F. At the end of a 4 second dyno run, the piston crown surface temperature will rise to 300 to 350 deg F.  

In the dunes at the bottom of the hill, the piston crown will start off at 250 deg F or so when the coolant temperature is 150 to 200 deg.  After 10 to 15 seconds of full throttle when approaching the top of a long hill, the piston crown temperature will often exceed 425 deg. F on a properly jetted engine.

The engine will make more power retarding the timing if your exhaust system is not matched up for your porting and head design when the pipe is a little to long .  An engine will make more power advancing the timing if the pipe is too short.

It is imperative that a person tuning two stroke engines has a good understanding of the above principles, otherwise the dyno tuning will not simulate real world conditions with engine failure often resulting.

Offline Morse250r

Cr250 ignition advance
« Reply #7 on: July 18, 2016, 11:35:19 AM »
Quote from: Skeans1;68850
Just for giggles have you done any testing with a 125 cdi an the combo as well?

not on the dyno but tried the box on my old pro x really didn't see any change with my set up
Packard built puma "bad investment"
88 rb racing duner
Trx 70\'s
Atc 125

 

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