what is it that causes a engine to be limited to its max rpm (eg.5500 stock with upgrades 10000rpm and so on) i know that stuff like double valve springs roller rockers and cam and all that fixes the problem but what is it that is preventing it from going higher than 5500 rpm is it the resistance in the block or ?????

i always thought it was cause the valves open longer on a bigger cam witch lets more fuel in (correct me if im rong)

simple. as the engine speeds up it uses fuel and air at a faster rate.
This rate of supply is limited by fuel system components (pump, carburettor jets) and also air flow components (head ports, valves etc)

Once either of these 2 systems is at a maximum, the resistance forces (friction etc) develop an equilibrium with the driving forces (the explosion of fuel/air) and a constant rpm is reached.

to allow for higher rpm follow this simple equation:
increase(fuel + air) = increase power
= increase rpm

hence why people put on larger carbies, cams, port and polish heads etc etc... until your wallet looks like it has been run over by a train! lol

however: its not all that sinple, increasing rpm generates extra forces on stock engine components, which more than likely will cause them to break (hence why people use forged components etc)

hope this helps

whats the max rpm of a a15 motor?

thanks ronald thats pretty much what i thought.

What limits the stock A12 is the valve springs. At max RPM each valve opens more than 3000 times per minute. The valve spring *closes* the valve. At somewhere around 6500 RPM the springs are not strong enough to close the valve fast enough, hence "valve float".

If you fit stronger (or even double) springs like the A12GX engine, you can go higher.

What limits the A15 may be the cast pistons. The stock ones will rev to at least 8500 RPM, but somewhere after that, both A15 and A12 pistons will break when the crankshaft pulls the piston down (the stock crank and rods are very strong). And over time at high RPM and high pressure levels, cast pistons will fracture and break. Hence Forged pistons in racing engines.

damn dd you make engines sound so sexy

lol!

Ronald is right, and I am sure many of you will know this already, but just thought I would add my 2 cents for those who don

hey ratboy is ur name mitch