993TT compression ratio
12-12-2005, 01:01 PM
#31
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Join Date: Jul 2005
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Juha,
Sounds like you made your mind up... so just some thoughts, and maybe Kev/Geoff/PHD/viper can add some detail.. IMHO, with knock sensors you can obviously run single plug and hopefully avoid any harmful detonation... (not optimal but should owrk ok at your ST-1 power levels) again, IMHO, there are a few things to be mindful of... if you are going to eventually go twinplug, have your heads tapped and plugged for the the second spark plug during the rebuild...
one big reason to run twinplug is the quicker flame propogation.. a 102 mm bore is a long way for the flame front to travel .. so you need to run more ignition advance to allow for the propogation... when you twinplug you can dial down the advance and get the results you want.. I'm sure others can comment better here .. since you do want as much advance as she can handle for the positive effects it has...
you may want to look at cam selection (for stage 1 or 2) and decide if you are eventually changing it ,(not sure what grind 'sport' is) or going to do solid cam followers... I mention this since the same cams may not work well for both.. you mention 520 hp.. On stage 1? The stock Motronics will not support this on the stock MAF ... you will also need fuel pressure regulation and probably bigger fuel pumps FYI... the stock MAF runs out of ability at about 490-500 hp... ..
... and Geoffs point about boost versus compression and teh HP limits is very true!! btw, that graph was with 8/1 c-r on the exact same engine as mine...BUT with 8/1 pistons.. 1.1ish bar.. mine was built after that engine..
my engine actually has more lowend and brisker throttle response(your CR theory), but will hit the 600 HP around .85-9 bar.... so I'm not sure what boost level with your config would work for you at 8.5/1.... boost levels are obviously critical with that kind or CR... a .1 bar difference can be sinnificant.. my config will run out of turbo, fuel, and MAF limits at about 1.1.-1.2 bar with an absolute max of 640-650 HP with bigger fuel pumps and 60 lb injectors...for example..
if you stay at 500 ish HP you probably don;t need to reinforce teh heads... but towards 550-600 you probably should...
...... people familer with the GT-1 turbos can help more here I think... since they play a large role in teh HP levels you're talking about..
.. hope this helps...
Sounds like you made your mind up... so just some thoughts, and maybe Kev/Geoff/PHD/viper can add some detail.. IMHO, with knock sensors you can obviously run single plug and hopefully avoid any harmful detonation... (not optimal but should owrk ok at your ST-1 power levels) again, IMHO, there are a few things to be mindful of... if you are going to eventually go twinplug, have your heads tapped and plugged for the the second spark plug during the rebuild...
one big reason to run twinplug is the quicker flame propogation.. a 102 mm bore is a long way for the flame front to travel .. so you need to run more ignition advance to allow for the propogation... when you twinplug you can dial down the advance and get the results you want.. I'm sure others can comment better here .. since you do want as much advance as she can handle for the positive effects it has...
you may want to look at cam selection (for stage 1 or 2) and decide if you are eventually changing it ,(not sure what grind 'sport' is) or going to do solid cam followers... I mention this since the same cams may not work well for both.. you mention 520 hp.. On stage 1? The stock Motronics will not support this on the stock MAF ... you will also need fuel pressure regulation and probably bigger fuel pumps FYI... the stock MAF runs out of ability at about 490-500 hp... ..
... and Geoffs point about boost versus compression and teh HP limits is very true!! btw, that graph was with 8/1 c-r on the exact same engine as mine...BUT with 8/1 pistons.. 1.1ish bar.. mine was built after that engine..
my engine actually has more lowend and brisker throttle response(your CR theory), but will hit the 600 HP around .85-9 bar.... so I'm not sure what boost level with your config would work for you at 8.5/1.... boost levels are obviously critical with that kind or CR... a .1 bar difference can be sinnificant.. my config will run out of turbo, fuel, and MAF limits at about 1.1.-1.2 bar with an absolute max of 640-650 HP with bigger fuel pumps and 60 lb injectors...for example..
if you stay at 500 ish HP you probably don;t need to reinforce teh heads... but towards 550-600 you probably should...
...... people familer with the GT-1 turbos can help more here I think... since they play a large role in teh HP levels you're talking about..
.. hope this helps...
