gtti have semi-forged piston so......no problem with high boost!
Forged:
· Stronger. The difference in strength between forged and cast pistons is considerable.
They can withstand loads anywhere from 40% to almost 100% higher than cast because the forging process makes the metal more ductile.
· Mass - the forged is lighter by about a third than cast. This makes a big difference at 7500rpm as lighter pistons can handle higher rpms with less
stress on the rods, crankshaft and block.
· Durability - the forged will take far more abuse without breaking because of it's finer structure.
· Oil use - after warming up a forged piston will use less oil as it's thinner rings will seal better.
· More power - rings can account for up to 40% of an engine's internal friction. If they are thinner - less friction -less heat - more power.
· Detonation - casts are very intolerant of detonation especially around the ring lands. Forged pistons will conductheat of the crown faster than cast
because of the structure. Overheated combustion chamber parts start reacting as glow plugs.
Pre-ignition induces extremely rapid combustion and welding temperatures.
Melt down is only seconds away. So if you are in the habit of going to the red line a lot (try to change this - a standard Lav runs out of steam at around
7500 so going to 8300 is just making noise!) or riding long and hard on hot summer days, racing or your beast has been tuned to the tits - consider forged
pistons.
Otherwise casts are fine.
Pre-ignition and detonation problems should be fixed and their end result not blamed on the piston.
for more information just go to...
http://www.laverdamania.com/pistongb.htm
gtti
cheers to Daihatsu for sending us a bit of their oriental magic. (I was devastated when they were cut from production in 93')