|Posted on Friday, September 17, 2010 - 04:53 pm: ||
so i had made some changes to the timing maps on my bike as well as the fuel maps. i am very pleased with what i did but i was wondering like what happens if u raise the timing to much and what should i look for. i only added very little to it but im kinda curious if anyone has done this before i try to add some more.
|Posted on Friday, September 17, 2010 - 05:39 pm: ||
Too much advance can lead to detonation or pre-ignition. Can also lead to higher engine temperatures as well. All are bad for motor.
Best way to check if you have too much timing is to use a thermocouple on your spark plugs and check their temperatures while on a dyno.
The XB/XL series of engine is extremely efficient and thus typically needs very little ignition advance due to small bore, low rpm and good head flow characteristics.
|Posted on Friday, September 17, 2010 - 08:34 pm: ||
I'm a fan of high ignition timing, always have been. An old Pro Gas race car I used to own, proved my point. LOTS of experimentation
Anyway, "low" ignition timing will cause overall excess heat. The later ignition starts, not only doest the engine have to work harder to get the piston to TDC, most of the power that's "capable" of being there is wasted with the piston being too high in the cylinder.
The "detonation" will burn pistons...but that is localized heat caused by the excessive pressure in the cylinder, not a "direct" cause of the timing value.
A higher octane fuel would fix this particular problem, not lowering the timing.
As Sloppy says, too much timing will cause preignition (detonation). You have to listen VERY closely for it.
Don't be fooled... This is coming from someone who almost learned the hard way.
These engines seem to like a lot of timing...in the right places.
I was playing with my "12R's" timing. The driveability kept getting better, the mileage kept getting better (average of 51).
I didn't stop there...! Finally, I realized I was driving "all the time" in detonation. Even at steady state speed.
I finally realized this one day when I didn't use my ear plugs on the freeway.
I have a borescope, so I looked into the cylinders. Well, there is pits on the piston tops, but luckily, their not too bad and on the exhaust side only as would be expected.
Yes, the engine's like it...but go at it very carefully.
A dyno would be a great help here, cause you can watch the power AND listen to the engine at the same time.
|Posted on Saturday, September 18, 2010 - 12:18 am: ||
If you're an old pro-gasser, I bet you had to use A LOT of ignition timing to get that mixture enough time to fully combust.
The whole point of ignition timing is to "pre-fire" the combustion chamber so by the time the piston / con rod / crank angle are at max leverage, that the combustion pressure has had enough time to get to its maximum.
Dyno's aren't that expensive ($50 per 3 runs in my neighborhood) and a thermocouple costs about $100 so experimentation is a smart way to go...
|Posted on Saturday, September 18, 2010 - 07:07 pm: ||
thanks alot u guys helped alot. explained very well for me to understand. now i would like to know the noise that i am suppose to hear while the bike is running. ive only raised it a few numbers each cell on the map. and i am very pleased by the way the bike rides. but i just cant afford to mess anyhting up know that funds are tight. but i am still intrested on the noise/sound that its supposed to some what make.
|Posted on Saturday, September 18, 2010 - 11:47 pm: ||
Sounds like someone has thrown a hand full of marbles at the hood of your car.
This sound could also be just a couple of marbles hitting the hood..
"Most" of the time...you'll hear the sound under acceleration.
Accelerate hard at different rpms, and listen close. Remember the test rpm's so you can lower the timing cells if needed.
The cruise rpm cells are more near the center of the map.
The acceleration cells are located higher on the map.
|Posted on Monday, September 20, 2010 - 01:29 am: ||
mike alright thanks alot for the advice il let u know how everything goes.