only other common question we are asked, is people running road cars e.g.
Astra 2.0L 16V or Cavalier SRI & GSI even the modern Ecotec engines
as fitted to the latest range of Vauxhall cars. What kind of camshaft
can I fit to my car? As well as all the problems already listed, you have
one further problem to add and that is, that most production cars use
what is known as air-flow metering.
are either what is called ‘hot wired’ where the air being drawn across
a heated wire changes the resistance according to temperature. So the
faster the air, the cooler the wire becomes and from this the standard
ECU is able to work out the amount of air being drawn across the air-flow
other type is what we call a ‘gate type’ and the faster the engine draws
the air, the gate being sprung loaded, is sucked open further. Now for
the problem – all camshafts generate a pulsing effect, this is where at
a certain point in the engine cycle, the inlet charge becomes stationary
(for simplicities sake). On a mildly tuned engine e.g. standard, this
stationary pocket of air remains very close to the cylinder head. As you
attempt to increase the cam duration on overlap to generate more power,
this stationary pocket of air moves further and further up the inlet tract,
eventually reaching the air-flow meter. Once this happens all air-flow
metered systems become completely confused. So if you fit a camshaft which
is a great enough improvement to give you an increase in performance,
it will almost certainly produce the described effect and if you fit a
camshaft mild enough not to cause the effect, your gains will be almost
might say, why not move the air-flow meter further away? Problem 1 is
the reason most road cars are sluggish on throttle response is because
the airflow meter is so far away from the head to begin with. The manufacturer
has carefully worked out the position, which is as close as possible to
the engine without causing the effect described. The further away you
move the airflow meter the slower the throttle response becomes. So in
effect, any gains you might have got from changing the cams is completely
lost by the increasing delay of throttle response.
only kind of system that can cope with this pulsing effect, is a throttle
angle system such as the MBE systems we supply. They are pre-programmed
with an amount of fuel for every at various speeds and throttle openings
and as such are not effected by pulsing. There is also no delay because whatever
speed you are at, and whatever throttle angle you achieve, the ECU knows
immediately the pre-programmed amount of fuel to deliver.
as you will see from our engine kits, if the replacement cams are used
they are fitted in conjunction with either, deepening of the pockets of
the standard pistons or replacement of the piston with up rated piston
with deeper pocket & higher compression.