Sifus,

i'm planning to undertake a PnP job to my 4G15 head whereby upon reading some articles about it, it is claimed the port entry & exit is already achieving 95% flow efficiency while at the port bowl is around 75% and only 50% at the port throat & valve seat...

http://www.popularhotrodding.com/enginemas...eads/index.html

hence, should we just ignore polishing work to the exhaust port and ask the machine shop to just concentrate on reprofiling the port bowl and undertake a multi-angle valve cut plus chamber deshrouding?

moreover, some machine shop is able to increase compression ratio of the head by welding some metal filling onto it....should i also go for it?

http://protoncars.biz/index.php/topic,25613.40.html

members feedback are highly appreciated..






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japanese cylinder heads requires different porting methods from their american cousins........ That american head design is from the age of the dinosaur

wow... how u calculate ur cylinder head flow efficiency by urself??.. ur house got bench flow test rig??...

I use a flow test rig belonging to a friend of mine.......

i mean TS... not u la...

Read the article, then you know where the percentage all comes from

oh... nasty port flow... nice nice... but price... also vr nice... lolz..

Yup..nasty port flow also comes to mind..nearby my house only

hows ur 92p?

1. Basic
RM750 - Port n Polish + Valve lapping (Add RM200 for Flow test before n after)

2. Street
RM1000 – Port n Polish + Valve lapping + Multi-angle valve job (Add RM200 for Flow test before n after)

3. Competition
RM1400 - Port n Polish + Valve lapping + Multi-angle valve job + deshround combustion chamber + Flow test before n after

Guess mine is no.3 already

hardcore

That's the only way to go... Why waste time doing the job a few times over?

cata got 92p?

he not refering to me la... mine 13p only...

x much progress..haha..currently runninf on ron 95..so far so good

Either is max POrt or no need to port at all...

Unless you intend use longer duration cams to take advantage of your proposed PnP project, its best you just keep the green and find a good and reliable mech and do a Top Overhaul...

From the Top process, the head can be de-carbonized and have a shiny polish job while retaining its original specs...Further more, you can also skim the cylinder head and look for a metal type gasket....

a good suggestion...but as my project is actually trying to improve the 4G15 FC to a 20 km/l (yeah i know it is unbelievable but i'm an ardent fan of Obama's slogan - Yes, WE CAN), i need to read-up and gather good technical info's on how to achieve this and one way i think is to improve the engine volumetric efficiency...