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Ignition Timing

Ignition Timing

(Or what ever happened to old Trigger... did Roy REALLY stuff him?)

By now, many of our resident motorheads (from admiral class to junior wannabees) have figured out that advancing the ignition timing on our rides can result in a nice, easy performance increase. For now, there are a couple of alternatives to Valkyrie owners on how to accomplish this. One is to change the baseline initial timing through the use of the Air Lake Trigger Wheels and the other is the Dyna 3000 ignition module. The Dyna 3000 actually provides a stock and optional advance curves that can be electronically set through switch setting on the unit. But which one is best for me, or for that matter, do I even need my ignition advanced?

As this is one of the hottest topics on the VRCC boards, it's probably time we discussed it a bit more. It has gained some added notoriety of late with two recent magazine articles. The first was an evaluation by Motorcycle Consumer News (MCN, the USA version). They tested the Trigger Wheel and liked the results. More power and better gas mileage. They also used the recommended increased octane fuel. More on this later.

The other article of note was again on the Trigger Wheel, this time tested in a 1999 1500 Gold Wing that was just published in the Gold Wing Road Riders Association publication Wing World. This was a truly lengthy article (the longest I ever remember in Wing World) that provided a lot of good information for the reader. The trouble, in my mind at least, was the testing method used was intrinsically flawed and therefore the conclusions drawn from the test were at best problematic. Namely, the author conducted the test of a 6 degree wheel using regular grade, 87 octane gasoline. This, despite the manufacturer's and many other's admonitions to switch to higher octane fuel. The test did seem to verify that higher octane fuel is often a good idea when advancing the ignition curve. Can I have a DUH from the congregation?

First, it is really much simpler situation than our friend at Wing World made it out to be. The ignition timing curve is one of the last things optimized on a motor vehicle. It is going to be compromise from the factory due to production and use tolerances. In other words, they don't optimize each individual Valkyrie's ignition timing as it comes off the production line.

Next, there is the consideration of exhaust emissions. Due to the vulgarities of modern emission testing, most vehicles are tuned with a bit less timing advance and a slightly leaner fuel mixture right around normal cruise engine speed. That's because this is where most of the testing takes place. Again, taking into
consideration variations for production tolerances and wear, we again back off a smidgen, just to be on the safe side.

Then we have design use. In the case of Gold Wings and Valkyries, they are designed by Honda to run properly on regular grade, 87 octane gasoline. Many high performance vehicles specify premium or 90+ octane gasoline. And no, the Valkyrie doesn't fit into the high performance category. That is unless you're
comparing it to the average V-twin cruiser.

So, it would appear that those of us who are willing to buy a few parts, do a little wrenching, and possibly switch to higher octane gas, can optimize the running of our bikes a bit. Especially in that part the factory purposely held back. That's why we can see a nice increase in horsepower and torque at say 2800
rpm, and much less so at say 6000 rpm. If you look at a stock Valkyrie dyno power plot, you'll notice a dip in the mid-range portion of the curve. And this is also where most of us spend much of our time riding.

So, how do we alter the ignition's timing curve? You all knew I'd get there eventually, eh? But, sorry about this, I've got to toss in a simple model here. I promise it won't hurt much though.

Once your engine is set up with its displacement, compression ratio, combustion chamber design, camshaft timing, carburetion, etc., you optimal ignition timing is dependent on two basic things. This is engine speed and load. Temperature also plays a minor role at times, but we'll touch on it later.

As the engine runs faster, the timing needs to be advanced in order to start the combustion process sooner. This will result in the optimal combustion pressure increase being applied on the top of the piston at just the right time to do the most good. Simple enough really and fairly easy to achieve. We can do this mechanically as they've done for years, or in more recent times, we can map the curve electronically based on engine speed. Some of you old hot rodders have changed out the bob-weights and springs in your car's distributor to get a faster ignition curve. This was in addition to possibly advancing the base timing setting by turning the distributor a bit.

Here's where we're at with the Trigger Wheel and Dyna 3000. The Trigger Wheel changes the base timing setting, advancing it 4 or 6 degrees. It does this across the entire rpm range. The Dyna 3000 changes the actual advance curve, starting around stock at idle and increases the total advance curve from there in steps according to the switch setting. Once past the initial stock setting, it also gets rid of that mid-range emissions dip. LaMonster recently posted an excellent graph with the Dyna ignition curve settings.

So, which is better? Ah, here we go again, but it depends! For around $50 and some higher octane gasoline, the Trigger Wheels do really make a difference. Most of us are picking up 3-4 mpg. I know that doesn't sound like much, but on my bike it meant going from an average of 30 mpg to 33+ mpg. This means at least 15 more miles per tank on a bike with some pretty lousy range. It also smoothed out some of the roll-on power in high gear in the 55 to 65 mph range for me. For the time, money and effort, I'm sold!

Now the drawbacks. Other than the need for more expensive gasoline, the other is the Trigger Wheel doesn't alter the shape of the curve. So for one thing, I still have the nice stock dip. Just advancing it here 6 degrees at cruise probably helped my gas mileage as much as anything. But there may be even more
available on top and I won't be able to get there with stock ignition module. I also may have the timing advanced a bit too much at lower rpm levels, at least as far as optimal settings go.

At around $300, the Dyna 3000 ignition module actually varies the ignition timing curve, getting more progressive at higher switch settings. It also gets rid of the emission dip and should be able to produce more ultimate horsepower increase than just the Trigger Wheel by itself. One major drawback here is price. Based on its cost and the need to run more expensive gasoline, it's doubtful that either the Dyna 3000 or Trigger Wheel for that matter are going to pay for themselves through a small increase in fuel economy.

What about using the two together, Trigger Wheel and Dyna 3000. Some folks here already have but there's a consideration here as well. It's called total timing and it is the baseline timing plus and ignition advance up to the maximum, in this case, put out by the ignition module. At higher settings we may be using too much total timing for the engine. At the same time, using the Dyna 3000 at lower settings to simply get rid of the emission dip is kind of expensive, don't you think? Much like carburetion jetting, ignition timing needs to be optimized for each engine combination over its entire operating range. A sharp tuner with a dynamometer can help here.

Now what about that bit about load? Funny thing here but a lightly loaded engine can use more ignition timing than a heavily loaded one. We've all driven vehicles at one time or another that would ping or detonate going up hills or under medium acceleration. Most automobiles for years have had a system called vacuum advance as part of their ignition system. At light throttle settings where intake manifold vacuum signal is high, they add advance to the ignition timing a bit. At heavier loads where the throttle is depressed further and the intake vacuum signal is low they don't advance the timing. Timing is then set by the base timing setting and the rpm advance only.

Modern cars have much more sophisticated systems but they work in basically the same way. Until recently, most motorcycles didn't alter their ignition timing according to load or throttle setting. They also didn't carburate very well but that's another story. These days, more and more bikes are adding a TPS or
throttle position sensor to the system. It's basic function is to tell the ignition module, along with engine rpm and possibly temperature, if it can advance the timing curve a bit more. Properly set up, they help the
engine run better and more efficiently. Unfortunately, our Valkyrie's don't have one. At least not yet.

Another thing a lot of modern cars have that our bikes don't yet is what's called a knock sensor. Basically a piezoelectric switch, it listens for the specific frequencies resonating through the engine during pinging or detonation. It then tells the engine module to back the timing down a bit until this stops. In addition to providing an extra safeguard for the engine while allowing more ignition advance, it allows some engines to run on different grades of gasoline. Put the cheap stuff in to save money and the good stuff when you want some more power. It definitely requires a sophisticated engine control module (ECM) which typically varies both the ignition and fuel mixture settings. Maybe next time when we get the full electronic fuel injection (EFI) system?

So what's best for you? Some guidelines if you will. If the engine is basically stock and you like running regular gas, leave as is. You're not going to get something for nothing by advancing the timing and continuing to run regular gas. In fact, you may damage your engine or at least shorten its life. Marty Rood
posted a message a while back about the pinging or detonation you might not hear. And our friend in Wing World found he couldn't hear all signs of detonation at highway speeds on an ultra quiet Wing. How are you going to fare with your shorty helmet and drag pipes?

Those looking to run a K&N filter, some pipes and a good re-jetting should do well with the Trigger Wheel if you're willing to pump up the octane, so to speak. For a Valk Standard or Tourer, I'd go with the 4 or 6 degree model. For an Interstate or Gold Wing, I'd stay with a 4 degree wheel if I was going to haul much of a load. Right now I'm running a 6 degree wheel with a big load at times on a basically stock engine and have found no ill effects. I always run premium and I don't lug it either.

For you big-bucks types and anyone doing more serious work on their engines, the Dyna almost becomes a must to allow you to completely tailor your ignition curve. Bigger cams and freer flowing carbs and exhaust may want more baseline and a steeper curve. Hey, nobody ever said going fast was cheap! And for those of you contemplating going where no Valk has gone before, get yourself one of the new adjustable advance timing lights. They're bit pricey but indispensable for this kind of thing. No, you can't have mine but I'll let you use it! :)

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