I know this has been mentioned and the general concensus is that strokers cannot take as much timing as a 2.0. Can anyone with knowledge of engine theory speculate why? Is it because the higher piston speed of the stroker crank gets the piston to TDC quicker, therefore needing less advance to create optimum power after TDC? Can anyone recommend timing for pump gas and race gas for a stroker (I'm only interested in base numbers, I don't expect someone to post their entire timing map). Also, since strokers tend to scavenge better, how does that affect the amount of boost relative to a 2.0L?

 

How much ignition advance the motor takes before the onset of detonation is basically a factor of pressure and heat.

The stroker has a higher mean piston speed and shorter rod/stroke ratio, which means it's more efficient at developing cylinder pressure at lower engine speeds.

The stroker piston moves faster around TDC, so this alters the relative ignition timing and cam timing somewhat, which affects cylinder pressure.

If the stroker moves the torque peak (peak cylinder pressure) downward in the rpm range, the slower movement of the piston necessitates less ignition advance. Also, if the cylinder pressure (torque) is greater at any given piston speed, that will decrease the detonation threshold (less timing advance tolerated) for any given fuel octane.

Given these inherent differences, it shouldn't be viewed as a fault that a stroker 'cannot take' the same degree of advance, it's more so that a stroker doesn't require the same degree of advance to get the ignition timing where it needs to be.

 

So a stroker running lower timing isn't indicative of a problem; more a case of more efficient at lower timing due to the factors that you mention? Everything else being equal; a stroker might have same cylinder pressure at 8 degrees that a 2.0L might have at 14 degrees?

How does the longer stroke affect ability to run more/ less boost or does it even out with the additional displacement to fill?

Thank you for your response, Ted B

 

If you read around the tuning forums, almost everyone with a 2.3 stroker says that can't get anywhere near the amount of timing advance as on a regular 2.0. The 2.3 doesn't need as much timing to have good torque and power. If you try to apply the same ignition timing maps to the 2.3, you are going to break something. As Ted B mentioned above, the piston speeds are much higher around TDC for the stroker, it is only natural for the ignition timing to be affected by this.

Please note that you might be getting some false knock readings on the 2.3 as well. Lots of people have noticed this problem. The acoustics of the engine have changed when you bolt in the stroker setup, you have to re-tune the knock maps to pickup on the new frequencies associated with the knock.