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Camshafts

This is again one of the most important factors to consider (along with cylinder head porting) when turbo matching your engine as it can have one of the biggest impacts on turbocharger performance. Again, many people believe (incorrectly) that bigger is better when it comes to camshaft size and design when modifying an engine… this could not be further from the truth when fitted to a turbo car.

The bottom line is big camshafts with wild lift and overlap work very well on naturally aspirated engines but don’t work on turbo engines. If you want good response and no lag they simply don’t work… end of story! Sure you will get huge power increases but at the very top end of the rev scale, (remember the Robin Reliant at the lights again!) but the bottom end response will be very poor. This sort of cam design can also have a more serious side effect on the turbo as it can increase the chances of inducing compressor surge from the turbo, again due to the gas speed. We have many situations where we have had to down spec a hybrid turbo to fit an engine with a “Ported & Polished Head” and “Fast Road Cams” to gain the same response as a larger turbo on a standard engine.

 
Camshaft Valve Timing

This is not as critical as the porting and camshaft design but again it can have a big influence on the matching and performance of the turbocharger you select. Cam timing will not have much of an effect on overall performance but there are gains and loses to be had… for instance, retarding the cam timing can often help with response and lag, just the same advancing the cam timing will give more top end power… again it’s the word compromise. Most of the time we find the manufacturers have got it pretty well sorted from the factory (not allowing for mass-production variance). Obviously you can’t beat adjustable cam timing to set it to the optimum position.