I just stumbled onto a Japanese rider's website where he was talking about his D-Tracker mods (aka KLX) and he posted this picture



and said, "We are allowed to advance to the limit the initial ignition timing with the long hole mounting holes of the pickup coil" (Google translate)


So, what about them apples? Is there some power to be gained by adjusting the initial timing?

I am aware of Ray Cour's CDI experience where no power was gained with an adjustable CDI box.. but this is a free mod (!)

 

Advancing the spark helps response at lower rpms, right where the klx needs it most.I have studied this before and intend to try it at some point. I'm really enjoying my bike just like it is for now.
marc

 

I can't risk pulling my side cover off to take a look at the pickup coil until the new side cover gasket I ordered gets here in a few months (I'm overseas)..but once it arrives I will give the p.u. coil mounting hole mod more consideration.

I emailed the guy in Japan, but reading through his website again it looks like he sold the Kaw motard racer some time ago, and he may not care to be discussing this mod or the FCR37 he had on it.

 

Any feedback from any of those sources as to how this mod might affect detonation/pinging?

 

Factors.........................Advance Timing for: ....Retard Timing for:

Cylinder Pressure..................Low...........................High
Vacuum............................. High...........................Low
Energy of Ignition.................Low...........................High
Fuel Octane........................High...........................Low
Mixture (Air/Fuel).................Rich...........................Lean
Temperature.......................Cool...........................Hot
Combustion Chamber Shape...Open..........................Compact
Spark Plug Location..............Offset........................Center
Combustion Turbulence.........Low,,,,,,,,,,,,,,,,,,,,,,,,,,,,High
Load.................................Light...........................Heavy

(from the internet)

 

I think that if your riding style is not to do much shifting but rather lugging the engine a lot, then you wouldn't want much advance. If you like to shift and keep the rpms up, then maybe you could handle more advance.

There are lots of results in a general internet search about keeping an eye/ear out for pinging detonation

 

More from the internet..

"Pre-ignition" is when the air/fuel mixture auto-ignites from excess heat and/or pressure before the spark plug has fired, and has little to do with the ignition timing.

Unfortunately for the tuner and the customer, it can sound exactly the same as an auto-ignition from timing that is too advanced. Lowering the pressure and/or the heat in the combustion chamber will reduce the chances of pre-ignition.

Lowering the pressure on a forced-induction engine is as simple as lowering the boost, but on a normally aspirated engine it may be as daunting as changing a head gasket to lower the compression ratio.

Fortunately, pre-ignition may be caused by something as simple as a spark plug that is too "hot." This heat range rating on the spark plug refers to its thermal conductivity and its ability to dissipate heat.

A "hotter" plug will retain more heat in its tip and may stay hot enough to ignite the air/fuel mixture at an unwanted time. Therefore, "colder" plugs are desired when the pressure in a combustion chamber is increased. Care must be taken when choosing a heat range for spark plugs, as plugs that are too "cold" will result in poor starting and drivability."

 

Yes, those are all "general" issues in regards to real or potential detonation, but did any of the users with a KLX who actually did this mod have a problem with increased detonation? Under the right conditions in certain circumstances, I can hear some detonation. I'm running an OEM 300 kit which retains the 11:1 compression. Other bore kits that up the compression to 12:1 like the 351, may be even more critical to octane level and jetting or EFI fuel metering. I'm not saying that advancing the timing with this method won't yield results. I'm just saying that there is usually no "free lunch".

In a few of my performance vehicles I had a MSD adjustable timing device in the cab of the vehicle that integrated with my MSD ignition box. Conditions often affected ignition timing to the extent that I would have to drop timing noticeably to prevent detonation...towing, hot weather, lower fuel quality, etc. Also someone mentioned how well timing advance helped a tuner car they had. I'm guessing that vehicle may have also been equipped with a computer, maybe FI, and an antiknock sensor that would automatically back off the timing or influence fuel delivery to compensate for detonation. My KLX doesn't have any of that. Ignition timing can be a valuable tuning benefit or it can burn a hole in your piston...or worse. Just be sure you know what you're doing if you start advancing timing on any engine.

 

All true. Like adding a new carburetor or pipe one should make the changes in incremental steps. Keeping an eye your spark plug and engine noises, temperature etc

The amount of total advance (35deg vs 25deg stock I think it was) in Ray Cour's CDI was a lot more than stock and for at least as long as he had it on the dyno etc,the engine seemed to tolerate it.

You wouldn't want to just elongate the pickup coil hole(s), move the timing, and just head off *****-nilly. A degree wheel on the crank w/ pointer and timing light to check the new timing with the engine off would be advised to know exactly how much of a move you are making each time.

The KLX is detuned from the factory so much, there might be some potential for gain. The well known camshaft mod has just as much chance for tragic error-if not more.

You seem to be more against it than for it, People play with timing all the time. A dyno or riding buddy to do roll-ons against - some way of testing for gain or no gain should be included in the overall plan.

 

FYI from the internet

When establishing static advance the golden rule is never use less than 10; never use more than 20 degrees. The engine may well tolerate more than 20 degrees at idle, but the moment the throttle is opened and cylinder filling is improved it will pink heavily.

One problem often encountered when using more static advance than standard is that the engine may 'kick-back' when starting causing the
starter to slow dramatically, this can be confused with a flattened battery or duff starter motor.

You may need to compromise by the odd degree or two if your engine will not tolerate the required degrees of advance at start-up.

Pent-roof 4 valve Vauxhall16v,Zetec,Cosworth YB 30-32 degrees total advance

Note how little advance a four valve, pent roofed combustion chamber needs, this is because of the very short and equal length flame paths from the centrally placed plug promoting a very fast burn.

Engines with a faster burn time have a much higher RPM potential, the faster the burn, the less advance requirement, and therefore the fewer problems at high RPM.

This is why Grand Prix engines have many small cylinders; these have small combustion chambers that have very fast burn times,allowing much higher RPM than engines with fewer large cylinders