I was just wondering what and how does this mod effect the Banshee. Also anyone that is running the V-force reeds could you give me a report on them. Im thinking of getting them but id like to get a few opinions first. Thanks







2001 Banshee [blue]
FMF Fattys, Power 2s, AC full skid, AC front and rear bumper, Alba jet kit, 01 Alba graphics and seat cover, Razors, k&n air filter w/outwearer, DG kromelite nerfs,

 

A degree key is a tiny piece of metal that costs $20 bucks!

As your RPM goes up timing gets retarded more and more (the spark plugs fire farther and farther after it hits the top, and is starting on it way down) When it does this you loose power because as the piston goes down, you loose compression before the plugs fire and the fuel ignites. The timing key advances the timing, so the plugs fire closer to the top. It's supposed to help a lot on the top end, and alow the bike to wind higher.

I bought one, but haven't installed it yet, so I don't know how well it works.

 

A degree basically offsets your flywheel, allowing the timing to be advanced, the same thing can be accomplished with a timing advance plate. The common degree keys advance your timing +4 or +7. The +7 is recommended for mx and very short drag racing. The +7 will run flat on the top end.

 

don't even get one from curtis sparks. he sells great stuff but i installed one on my 440ex and didn't notice a differance.save your money and time

 

As quick hinted at the first reply isnt totally right, advancing your timing actually boosts your lowend performance, going too high causes a loss of topend, the trick setup is programmable ignitions so you can advance down low and retard on top ;-D

Oh yeah, The delta force reedcage is real nice, better throttle response, and dynos show an HP increase, although I think what you notice most is the crisper throttle response.



EDIT:

The timing advance helps 2 strokes a lot better than the 4 strokes[img]i/expressions/face-icon-small-smile.gif[/img]

 

Here's a dyno test with the Vito's degree key. Most of the gain is on the top end. The bike doesn't wind higher as I would have expected, but it is good for a few horse power. They got 2.6 horse more with just the degree key.

http://www.mobiledyno.com/sys-tmpl/s...&UID=10007

The bike has other mods, but the difference between the two runs shown is only the degree key.

 

http://www.mobiledyno.com/sys-tmpl/s...&UID=10007
Here's a clickable version of that link.

 

ok, so you feel 2.6hp on top is better than the fact power comes on 1000 rpm sooner? then yeah I see your point looking at the dyno. Although dynos arent exactly real world.

To illustrate a point, get your head out of the dyno sheets and install the degree key, Im betting you will feel a bottom end boost not the topend. It gets much more drastic the higher advance you go.

 

lucifa,
I've got the Vitos key and you're right, dynos and real world riding isn't the same. I felt no power increase (the bike's still not ridable below 6K RPM). If anything, it was a little better on the topend.
Hope this helps,
Fish

 

At lower RPM's the scavenging efficiency, the engine's ability to purge(scavenge) the old burnt exhuast gas from the cylinder, is typically lower than at higher RPM's. The mixing of the old exhaust gasses and the new incoming intake charge intermingle and the new fresh charge gets diluted and "contaminated" by the old hotter spent gases. This diluted charge is harder to get to burn as well(combustion efficiency) By advancing the timing, the spark advance allows for an earlier spark, thereby giving the mixture more time to burn, and in doing such more complete combustion. Ignition advance also raises the cylinder temp's and EGT's as the burning mixture is held within the bore longer. This extra heat can help also in better combustion efficiency. This is why typically more advance will help bottom end to mid power. Also why advance helps 2 strokes more than 4 strokes, there is less cylinder scavenging at lower RPM's in 2 strokes than there is in 4 strokes. More advance will however make the "hit" onto the pipe a little more sharp, which may not be desireable for your type riding.

Cylinder head pocket shape can help reduce the need for ignition advance, but typically again not until higher RPM's. This is where advance can help "bridge" across a problem, providing a needed boost. Also for most people to cut, test, and re-cut, and test, and re-cut and test pocket shapes until the "perfect" shape is found is not practicle and therefore the addition of an advance key or timing plate is practicle. There are often too many variable in pipe expansion chamber effects, port timings, RPM range, and carburation, to be able to select this "perfect" pocket shape, and again it is likely to not be as efficient at 5K RPM as it will be at peak power RPM at say 8500 RPM...A good pocket shape and timing advance will work well together and provide more power together than alone.

Too much advance at higher RPM's will create negative work for the engine. The piston is still coming towards top-dead-center(TDC) when the spark fires. The now lit off mixture begins to expand, and will "work" against the piston still coming to TDC. This is negative work or parasitic work if you prefer. This can cause engines with too much advance to go flat, or loose power on the top-end. This is where programable ignitions are great. They allow you to run lots of intial advance at lower RPM's, sub power-band(<6K RPM), and then retard the timing at higher RPM's, where less negative/parasitic work will happen.

Retarding the timing at higher RPM, also helps in moving the heat from within the cylinder, "out" into the pipe where it will make the expansion chamber "work" and hopefully(in theory, but not always)better. The added heat will make the pipe think that it is shorter(sound moves faster in hotter EGT's) and allow the pipe to become more in tune with the higher RPM's. In addition to the heat helping the pipe, it helps your cylinder temps to stay down as well, possibly avoiding nasty stuff like detonation.

Tuning and testing is the best way to find exactly how much advance you may or may NOT need. As mentioned there are alot of variables and to get the best, test and tune with varied timing settings, and check your results. There are often "rule of thumb" amounts, that can be applied, for instance, Banshee's for everyday riding typically do well with 4 degrees; drag racing 6 or more degrees advance. Honda 250R's are nearly the same.

In a perfect world, which is rarely attainable in 2 stroke engines. We would have programmable ignitions and "perfect" pocket shapes and endless power throughout the RPM range. This simply isn't the case. While the above is the best scenario, a timing key or plate and a "good" pocket shape will often lead us to better power throughout the RPM range than without.