I have a 600cc 4 cylinder Honda engine that my race car team uses.

The rules of the race mandate that we install an intake that is substantially smaller than the stock factory intake size to limit power.

This year, we want to optimize the stock camshaft profile to increase power across the whole curve (or at least the low end).

The engine is running on stock factory cams but its air intake is much more restricted that stock so the current camshaft profile is not optimal. So this means we need to reduce duration/overlap on intake and exhaust camshafts. I am looking for help on how to find the new profile.

(I'm guessing it will be something like this but I need to calculate actual numbers). camshaft profiles

How do I go about doing this? (Using spreadsheets)

Thank you


First of all, do NOT USE EXCEL. Sooner or later it will lead to undetected errors and great sadness.

Next, whether you use "Excel formulas" or proper code in tools like MATLAB or python, you need to start with the equations and formulas and boundary conditions you want to work with. Only after you have this can you start to make software do the optimization you desire. Sadly, we are nowhere near the STTNG - level of software yet ("Computer, design an optimum cam shape for me, and while you're at it pop a couple out of the Replicator")

  • $\begingroup$ Thanks for the answer. Where can I find the equations? Is there any book which explains this stuff? How do cam shops do it? $\endgroup$
    – Ardalan G.
    May 11 at 21:51

So, plot the valve opening time against the crank position, then consider the rate of opening, duration it is open and closing time and -of course- rate of closing.

Once you have this against the crank position then check things like valve overlap as this helps the leaving exhaust gas «pull» the fresh intake air into the cylinder as well as the fresh gas cleaning out the exhaust gas from the cylinder.

Once this is clear against the crank then the cam shapes can be defined - and your decisions above may well cause different profiles for inlet and exhaust.

The choices will change the engine performance : a valve profile for a family car engine is completely different to a racing engine. A family car engine will easily idle below 1000rpm while a race engine struggles below 2000rpm but will rev to 12000rpm.

I chose a cam for a V8 that gave a flatter power band from 1500 to 4500 rpm a really good choice for its use.


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