Now driving a BMW :(
AO Platinum Member
Join Date: Sep 2002
Location: West Yorkshire
<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:<hr /><font size="1" face="Verdana, Helvetica, sans-serif">Originally posted by bazza:
<strong>What are the advantages and disadvantages? Does anything else on the engine have to be modified?</strong><hr /></blockquote><font size="1" face="Verdana, Helvetica, sans-serif">bazza
The camshafts (two on a Twin Spark) control how long the valves are open for. This in turn affects how much power, torque and revs the engine produces. The majority of modified cams will allow increased revs, but in so doing, move the power curves higher up the rev range. This makes traffic jams and town driving hard work. The benefit is greater power at higher revs, so you really get the benefit when you are singing along at 5,000 rpm plus.
If you view the engine as an air pump, it has to suck air in to blow air out. The more it can suck in, the more it can blow out. In the middle it has to mix the correct amount of fuel with the correct amount of air. So, more air, needs more fuel. On old fashioned cars you could add bigger carburetors (seee my Avatar!). On a modern engine, the ECU will cope up to a point - this is why your engine always "feels" nicer on a cold damp morning as the ECU takes into account the colder denser air. However, a revised cam is probably going to confuse the standard ECU, so you need a new ECU. Then, because you have the ability to rev higher (more air coming in), you might want to move the rev limiter higher, but then is the bottom end up to it? (I don't know how many miles you have on the engine). So then do you look at a bottom end rebuild with lightening and balancing??
My gut feeling is not to bother, unless you can find a really "mild" cam which is just a whisker up on standard - I would check that all the plugs and ignition side are in good nick, put a K&N 57i cone filter on with a cold air feed from the front spoiler / bumper, a decent exhaust system and manifold, and a revised chip allowing for these changes, and only then go for the cam...
Other alternative is to have some work done on the cylinder head for better flowing and porting - I am sure there was someone in the Owners Club mag advertising a 175bhp kit for the 145QV. I will try and have a look tonight for it.