QUOTE(eng98 @ Feb 2 2010, 03:43 PM)
i think because of the advance timing means.... it spark even b4 the valve are not fully closing? i guess the petrol smell are the cause by advance timing... left some unburn petrol goes to exhaust valve.... everytime i hard rev sure got petrol smell... especially after genting....
btw can pm me the price and location ? thanks bro shaz
and yes.. i changed my full exhaust... header to muffler
well i don't know why FC increase.
but here are some timing basics
The spark plug needs to be fired a few degrees before the piston reaches top dead centre (TDC, the maximum stroke before the piston descends), the spark comes early because petrol burns slower than we think so igniting early allows combustion to build as the piston is traveling upwards and reaches maximum burn exactly when the piston is at TDC giving maximum power as the mix expands pushing the piston downwards capturing all the chemical energy into mechanical force.
Advancing timing means firing the plug earlier before TDC and retard means firing nearer to TDC.
For the campro first batch 2004 the pinging is happening because of advance timing, what happens at low speed is the maximum burn is achieved before piston TDC hence the downward expanding mixture collides with the upward moving piston hence the metallic ping noise. But at high speeds the timing becomes just right, reaching maximum burn at exact TDC, giving maximum power. this is why people say ecu 2004 early batch was most powerful.
New batch have no ping but less powerful because the timing is retarded = firing the plug closer to TDC, which causes the piston to
pass TDC before reaching maximum burn so the energy from expansion is not fully transformed into energy pushing the piston down because there is more volume already.
Jul 21 2009, 10:04 PM
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