timing

[2/2 many banshees]

I just got a timing plate. So I was doing a little reading on here about it and it seems like all or most every one goes +4 why? And what diffs.would it make if you went +6 or +3 ?

[Overboost]

timing is simply when the plug fires in relation to piston location.

 

advance means it fires before the piston reaches TDC, retard is firing after the piston has left TDC.

 

just like in a car, the more you advance the timing, the more power you will get, however, you also get spark knock relative to how much advance you are running.

if you go too much timing, you will get spark knock which in turn, burns holes in piston tops. you need to find that happy medium for your engine. +4 is a safe area that 99% of all banshees can tolorate. you can go more depending on motor mods, condition, spark plug heat range and several other factors but +4 is a safe range for most all bikes.

if you have too much retard, it will cause a bog, loss of power, higher engine temps and a general lack of performance.

 

simple answer, all the bikes can handle +4, you tune/build for more. +3 or less, leave the plate off, the difference you will see is minuscule.

[mopar1rules]

for best top end/over-rev past max hp rpms, its best to have the plug fire, when the piston is as close to TDC as possible. advancing the timing, puts heat into the piston, where as retarded timing puts heat into the pipe. as mentioned earlier, too much timing w/too low of fuel octane, can get you into detonation city quickly. i played w/+4 timing on my shee and did notice a stronger midrange and bottom end, but my top end was considerably down. maybe i was getting some deto on top?? IMO the best thing to have the best of both worlds, meaning top end and bottom end, would be to have a programmable ignition from dynatek. then program a curve for like +4 bottom, +2 mid, and 0 at top end. this way you should have a strong bottom, strong midrange, and a strong top end, that will want to over-rev past max hp revs. i'm sure others will give a different opinion on this.

 

i know on snowmobiles for drag racing, the more you advance the timing, the higher octane fuel you need to run and the shorter the distance the motor will survive wide open. for example a +4 timing key on a sled, might be good for a 660ft run, while a +2 key would be fine for a 1000ft run. i believe this is due to the extra heat created on the advanced spark. more advance = more heat, and we all know heat is a huge enemy of our precious 2-srokes.

Edited April 19, 2009 by mopar1rules

[deckheight]

What ignition timing adjustments are doing is controlling combustion chamber pressures. Like has already been said, maximum chamber pressure normally needs to occur at or very near TDC. Too early and the expanding gases from the fuel charge fight the piston on it's way up, thus creating uncontrolled spikes in chamber pressures/heat which promote detonation. In other words, heat energy is lost to surrounding parts instead of exerting downward force on the piston. Max combustion chamber pressures occur too late and the expanding gases are playing catch up for a piston already moving in the opposite direction, thus heat energy is simply released out the exhaust port without exerting downward force on the piston.

Almost all internal combustion engines, that I am aware of, and that are available to the general public have been "de-tuned" to some extent from their design efficiency. An appropriate ignition timing advance is just one way to regain some of it. Or exceed it if your not carefull...

 

[2/2 many banshees]

thanks fot the good info guys my next ? is do you change your timing when you change your dome size?

[BoostedRex]

its best to have the plug fire, when the piston is as close to TDC as possible.

 

 

Is this a 2 stroke thing? Because I have built over 30 Honda race engines (car engines not atv engines) and this was never ever the case. We always tried to run as much timing at every rpm as possible without detonation and this was on 600+hp 10,000rpm revving motors. But building import race cars got to expensive for me so I converted to building Banshee's. I know there is alot of things that were golden rules while tuning our imports that aren't true when it comes to tuning banshee's. So I was wondering if this was the case here.

 

for best top end/over-rev past max hp rpms,

 

What??? Why would you want to rev past your peak hp? Shift... lol

[mopar1rules]

having the plug fire as close to TDC as possible, is more of a 2-stroke thing....i believe, as four strokes can have more timing thrown at them, as the piston in a 4-stroke, has another 2 strokes to cool down, and rid some of the heat that was placed into it from the hot timing.

[BoostedRex]

having the plug fire as close to TDC as possible, is more of a 2-stroke thing....i believe, as four strokes can have more timing thrown at them, as the piston in a 4-stroke, has another 2 strokes to cool down, and rid some of the heat that was placed into it from the hot timing.

 

If this is the case couldn't you use egt guage's to help you get the most timing out of your tune without melting the motor down? One thing we always watched closely was making sure our exhaust temps never exceeded 1350 degrees, even if the knock sensor said there was no knock. Sorry for the noobish questions, like I said I'm new to this 2 stroke thing lol

[2003LimitedBanshee]

If this is the case couldn't you use egt guage's to help you get the most timing out of your tune without melting the motor down? One thing we always watched closely was making sure our exhaust temps never exceeded 1350 degrees, even if the knock sensor said there was no knock. Sorry for the noobish questions, like I said I'm new to this 2 stroke thing lol

 

 

Guys who are buidling big time motors do use egt sensors to help with the tuning/running process. As for your earlier post, over-rev is going to come in to play with banshees more so than on cars, even fast-revving imports. Over-rev basically references your power curve not falling off a cliff once it passes peak hp, since you are likely to miss peak rpm on some shifts.

[AKheathen]

If this is the case couldn't you use egt guage's to help you get the most timing out of your tune without melting the motor down? One thing we always watched closely was making sure our exhaust temps never exceeded 1350 degrees, even if the knock sensor said there was no knock. Sorry for the noobish questions, like I said I'm new to this 2 stroke thing lol

some do use egt gauges to tue, but more than just timing. 2 reasons the ignition timing is affected so dramatically different on a 2 stroke. charge timing, and pipe timing. on your rice rocket, the charge timing is controlled directly at the the chamber, maintaining a relatively small amount of delay, which can be changed with cam timing and different porting shapes. on a 2 stroke, the piston must pump the air down to the transfers, and back up into the cylinder. for this reason, the delay increases as the rpm's increase affecting the amount of charge. so, when you are ported, and they talk about port timings, think of it as the 2stroke camshaft. the higher the ports, the longer the charge timing at higher rpm's, but lower compression ratio. there is a hell of a lot more to porting than that, but that's kind of an idea about it. the second thing is the pipe. on a 4 stroke, exhaust is pretty much just an exit strategy, even though tuning the right back pressure effects power. on a 2 stroke, the shape and length determins the timing of a return pulse to back charge into the chamber, raising the compression. higher compression will cause the charge to burn quicker. alot of spark advance at higher rpms is not only dangerous for heat reasons, but short circuts the full potential of the explosion by being at full force before the piston can even be pushed back downward.

 

this is just my 2 cents. i'm sure someone will have a different idea about it, or part of it. :thumbsup:

[12mm]

the guy i baught my timing plate from told me to +12 it

 

i thought maybe that was too much but he said it was ok......it is on a 4mil stock cylinder motor with 18cc domes that run on Q16 VP fuel or 110.

 

when i first got it,i was suppose to be running aly. but i could not get it to run good on it so i went back to gas but left the timing on +12,is this a safe timing for a 4mil/18ccdome motor on 110 fuel ??

[mopar1rules]

get rid of the +12 timing. no more than +4 needed. for the guy who trail rides on tight trails, where he/she can't get over 4th gear, than i would recommend the +4 timing for that, as it really helps the low-mid, but if you are able to be full out in 5th and 6th gear, than leave the timing stock, as your top end will be what its suppose to be. my $.02.

Edited April 20, 2009 by mopar1rules

[deckheight]

I don't run or build alcohol motors... Soooo, from what I have been told, alky needs more ignition advance than gasoline.

I do build Gas motors and IMHO the higher octane fuels need earlier ignition advance due to a slower traveling flame front. Again JMHO, with 110 octane fuel you would probably want +/- 16* advance at max rpm. Using OEM ignition components this would be the equivalent of setting the stator plate at approximately 7* advance from the OEM setting.

And don't get what I said earlier about "maximum combustion chamber pressures very near TDC" confused with when the spark plug fires. The plug is going to have to initiate combustion well in "advance" of reaching max chamber pressures. When the plug fires just helps determine at what point in crankshaft rotation max pressures occur.

 

the guy i baught my timing plate from told me to +12 it

 

i thought maybe that was too much but he said it was ok......it is on a 4mil stock cylinder motor with 18cc domes that run on Q16 VP fuel or 110.

 

when i first got it,i was suppose to be running aly. but i could not get it to run good on it so i went back to gas but left the timing on +12,is this a safe timing for a 4mil/18ccdome motor on 110 fuel ??

 

[mopar1rules]

see, i thought he was saying +12 deg w/the timing plate. i don't think there's a plate that can give that much timing?? not to mention, i thought he was running this on nothing more than race gas, where i thought +6 would be plenty. OOPS....

Edited April 20, 2009 by mopar1rules

[12mm]

see, i thought he was saying +12 deg w/the timing plate. i don't think there's a plate that can give that much timing?? not to mention, i thought he was running this on nothing more than race gas, where i thought +6 would be plenty. OOPS....

you are right,it is a +12 deg timing plate that i have and it is run on only race gas.

 

maybe thats why it falls on its face if you hole in the throttle to long..........when i got the plate it was suppose to be used on alc. BUT we could not get it to run on alc