Performance Modifications - a systemic approach

All of the modifications you do for performance need to be seen as a system. One part of the engine needs to work with the others, or nothing is gained. And sometimes, you can even go backwards.

This isn't complex, or confusing. An engine is a pump that uses the air and fuel it pulls inside to produce heat. This heat causes the air to expand and move the pump. If you think about it, everything you do needs to help the part in front of it and behind it. If you can improve the way the engine works as a system, you can get the most improvement for the work you do.

Choosing exhaust silencers that are less restrictive than stock will help - up to a point. Then the next item in the system needs to be looked at.

I will use my bike and my work as an example:
I started with TORS and the triumph tune. This was a nice improvement over the stock bike.

I then bought a Trident Half system, it flows more than the TORS, but the bike couldn't make use of the additional flow. So I removed the precatalyst from the header. I also did some minor clean up work to the header, and matched the header to the exhaust ports in the head. I even ground the header flange a bit larger than the exhaust ports on the bottom and the sides to prevent low speed air in the header from re-entering the exhaust port at low rpm and low throttle positions. This can help throttle response in many cases. The result was a very nice improvement in power and response.

The next area that needed work was the intake. I removed the stock throttle body, the rubber adapters that connect it to the intake ports, and the velocity stacks. I noticed that each of these parts needed a bit of clean up work. They had rough edges that intruded into the flow. So I cleaned up these parts. I even added a higher flowing BMC air filter. Again I noticed a nice gain in top end performance.

Now the stock fuel tuning was very lean in the midrange and at higher rpm, so I needed to add more fuel to take advantage of the additional exhaust flow and scavaging (pulling more air and fuel into the cylinder and out through the exhaust by stronger exhaust pulses). I chose TuneBoy (TuneEdit actually) due to its advantages over my experiences with Power Commanders.

I started with a tune developed by Wayne Macdonald at TuneBoy. This tune helped the midrange tremendously by adding much needed fuel. This also improved the top end power. But the tune was not perfect for my bike. I worked with this tune and altered the fuel ,and in some places I altered the spark timing. It worked even better.

I also looked at the temperature of the air entering the engine. If the air is cooler, it is denser. The engine can pull more air into the engine if it is denser. This makes more expansion possible, and more power is produced.

After this, I added adjustable cam gears to allow me to test the effect of a bit more or less overlap on the intake and exhaust cams. I also used velocity stacks that were a different than stock (in several sizes, taper angles, and radious of opening). Together, these allowed me to bump the peak power several hundred rpm. But this took a lot of work for a couple of more hp. In many cases, I actually went backwards until I found a combination that seems to work well with the previous mods. The cost in time and parts (not to mention dyno time) makes these couple of hp considerably more expensive than the each hp gained up to this point.

This is where I am now. Others may be able to do these same mods, or develop others, to come up with an even better combination. But these mods have taken a bike that started with 112 hp on a local dyno, and last made 135 hp and over 82 ft-lb of torque. This is a nice 20% improvement in power and torque throughout the powerband.

I have looked at the heads. The stock casting and machine work can be improved. So I am doing some clean up work in the ports that should add a bit more flow without increasing the port volume noticeably.

I am also coating a few parts to reduce friction, and to keep more heat in the combustion chamber and out of the cooling system. This will add a bit more efficiency and result in a touch more power.

Custom cams, and more involved porting would add a good bit more power, but the cost per hp starts rising substantially. This kind of defeats the reason I am doing this. I want to see what is possible with the stock parts when they are optimised to work together - as a system. And still keep the costs reasonable and the mods easily copied (or improved upon) by others in their garage or by having it done by a local shop.

Just because you have never done this before does not prevent you from doing it. There is only one way to learn. You can read and gain all the knowledge possible, but you need practical application to gain experience. I am no engine guru, but I may have experiences that others do not. If I can help, I will.

Triumph designed a great engine. Manufacturing costs and emissions regulations prevent them from making everything perfect. But that doesn't prevent us from picking up where Triumph left off.

I hope this helps.

I apologize for writing a "book", but I feel it was needed in order to explain what I did, and why. I realize that most of the forum members will not care about more performance from their Speed Triple, but those who do might find this informative.