How to make an engine make horsepower...
Although there are lots of techniques involved to get your engine to make horsepower, there are a couple of basics you need to understand before you get the spanners out of the toolbox.
Your 4 stroke bike engine is nothing more than an air pump. The more air you cram into it, the more air needs to get out. Simple.
There's no use in fitting a set of big carbs (or a power commander) , race camshafts, bigger valves etc., if you're using a restrictive exhaust. All these parts work in conjunction with each other.
I take it, you all know how a 4 stroke engine works. If not....google it.
Timing a set of camshafts is more than alligning the marks as described in your owners manual. That's your base setting, nothing more. Even in a stock, new, engine they can be way off the timing they really need to be. 6-10 degrees isn't exceptional.
Below is a serious article about timing camshafts, which I borrowed from the Schnitz Racing web-site.
https://store.schnitzracing.com/cam-lobe-centers-explained/
Tech tips from engine guru Greg Cope
A bit outdated, but interesting for some of us.
Exhausts explained
Exhausts play a major role in the performance of your engine. As mentioned above, the engine consists of a lot of parts working together to get the best torque and horsepower figures. To create an exhaust that gives us the best usable (smooth) power and torque, isn't just welding some pipes and bends together.
Lots of factors determine the diameter, length, collector shape and size, mid-pipe diameter/length and finally, the muffler, that will let the engine breath the way it should.
Engine size
Valve timing
Firing order
Intake length
Compression ratio
Torque RPM
Max. RPM
If you know all these figures, you can throw them in a computer program that calculates the sizes for you ( there are a couple of calculators on the internet, some good, some adequate ) and discover that most programs, are not using all the above data.... And that's what seperates an exhaust from a performance exhaust.
I once made the mistake to listen to a customer that wanted the mid-pipe ( the piece between the collector and muffler ) shorter, because he thought it looked better. Before we shortened it, we put the bike on the dyno and it made 112 RWHP. With the shortened mid-pipe, horsepower dropped to 104 RWHP ( on the same dyno ) The torque figures were even worse....
Now, before you say a bit of jetting on the dyno can cure that.... NO, it can't !! That's bullshit.
If you break a leg, there's no use in letting your arm put in plaster either.
In the pictures of the of the Ducati V4 race exhaust above and below, you see a lot of bends manufactured in the system. This makes the manufacturing a lot more time consuming ( and more expensive ) Do you think the exhaust factory would do that if it wouldn't matter? Think again.
CREATING A GOOD PERFORMANCE EXHAUST, ISN'T SIMPLY WELDING SOME PIPES TOGETHER
