Engine mods with conservative valve timing

[amichie]

It seems that most of the mods that NA engines benefit from like exhaust scavenging etc rely on having a decent amount of valve overlap. I have found that my 7mge is very intolerant to changing cam timing except for an increased tendency to ping with advanced inlet cam timing.

I think it may make more sense to upgrade the camshafts and then work from there when deciding on exhaust requirements etc.????

Another point you often come accross is that so many parts of the intake tract are said to be good for creating turbulence that assists in atomisation of fuel vapour droplets etc and generates better low end torque. I guess this doesnot apply to LPG engines?? What do you think.

[oldcorollas]

and what happens when you retard the timing with the advanced inlet cam timing?
and why do you think it pings?

pick cams and overlap based on desired rpm range, and then make everythign else work with them

arguably all airflow in engines is turbulent, but there are sometimes "devices" around injectors to assist.. maybe..

most LPG engines are basically a constant strem of gas, like a carby, and mixing in turbulent flow of a port and during being sucked into the cylinder, should be good enough..

[amichie]

and what happens when you retard the timing with the advanced inlet cam timing?
and why do you think it pings?

pick cams and overlap based on desired rpm range, and then make everythign else work with them

arguably all airflow in engines is turbulent, but there are sometimes "devices" around injectors to assist.. maybe..

most LPG engines are basically a constant strem of gas, like a carby, and mixing in turbulent flow of a port and during being sucked into the cylinder, should be good enough..

The reason it pings is the higher compression pressure you get when have early closing of the inlet valve. So far the best compromise I have found is slightly retarded inlet cam timing combined with slighly advanced static ignition timing.