I hear this all the time: "Well, my
car is about 160hp stock, but I've got a K&N airfilter, cold air intake,
and a cat-back exhaust, so my car is putting out way more than that. The
filter and the intake are good for 20hp each, and the exhaust gives me
35hp, so I figure I've got about 235hp now." Wrong.......so wrong. Usually
people like the above mentioned get a rude awakening if they ever have
their car run on a dyno. The simple fact is this: Modifications like this
usually don't do a whole lot, and the reason is this: The factory that
built you car put millions of dollars into the development of it. In most
cases, they did a pretty good job (their are exceptions). If they could
have changed a couple of little things and gotten an extra 75hp, you can
bet your ass they would have. That said, these type of mods have a place
in engine performance, but their place is in concert with other, more effective
mods, or in situations where just a small amount of gain is desired. From
the above modifications alone, with quality parts on a typical engine,
an output of say 170hp in the upper range of the engine might be achieved.
For those who want signifigantly more than that, other modifications are
in order. These include but are not limited to displacement increase, camshaft
and powerband changes, NOS, and forced induction. While a detailed discussion
of each of these is in the articles following this one, an introduction
to them will be given here.
The thing to remember about horsepower is that it follows a specific curve, defined by this equation: (Torque*RPM)/5252 = HP. From this is is relatively easy to see that increasing the torque for a given RPM will yield higher horsepower, as will increasing the RPM that an engine produces a specific torque. Case in point: A 95' v6 Camero produces 160hp, and 200 lbft of torque. In contrast, a current Formula 1 car only produces 250 lbft of torque, but puts out 900hp. The difference is caused by the fact that the Camero produces maximum torque at 4200rpm, whereas the F1 car produes 250lbft at 19,000rpm. So, performance modifications generally fall into 2 catagories: Those that increase torque and those that increase the RPM that torque occurs at. As far as increasing both RPM and torque, I'll talk about that in a bit. Displacement increase, NOS, and forced induction increase torque by getting more mixture into the cylinders to gain power, whereas camshaft and powerband changes increase the RPM that torque occurs at. Now with that out of the way, we can move on to the next article, how to choose which is right for you.
:Big site full of info on T'nT and Blizzard SkiDoo's
Antique Ski-Doo & Vintage Ski-Doo Restoration Resources
Report on Power Valve Maintenance
:Keep those R.A.V.E. valves clean
:An interesting article on the fable of "ram air"
:A tech article about rear cylinder siezures in PWC twins due to crankshaft torsion (very interesting)
:A page that has the skinny on Polaris triples (ie which ones to avoid)
New Hampshire Snowmobile Association
Vintage Arctic Cat Site
Phillips, Stib Inc.
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