Show full size 924Board.org
Discussion Forum of 924.org
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
 Technical FAQ924 FAQ (Technical)   Technical924 Technical Section   Jump to 924.org924.org   Jump to PCA 924 Registry924 Registry

low compression / high boost or vice-versa?

 
Post new topic   Reply to topic    924Board.org Forum Index -> 931 Discussion
View previous topic :: View next topic  
Author Message
-nick  



Joined: 16 Nov 2002
Posts: 2699
Location: Cambridge, MA

PostPosted: Tue Mar 11, 2003 1:49 pm    Post subject: low compression / high boost or vice-versa? Reply with quote

more turbo newbie questions... which is more desirable? i would think you could make more power with low comp / more boost but driveability will suffer?

for instance why not just crank up the boost with the 7.5:1 931 pistons versus less boost with 8.5:1? looking at the power stats it seems porsche didn't lower the boost with 8.5:1 which confuses my basic understanding. i would think owners with 7.5:1 motors could safely crank up the boost more than 8.5:1 motors and get more power out.

my copy of maximum boost is coming in the mail so i won't keep asking these general questions.

thanks,
-nick
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Peter_in_AU  



Joined: 29 Jul 2001
Posts: 2743
Location: Sydney, Australia

PostPosted: Tue Mar 11, 2003 3:49 pm    Post subject: Reply with quote

with real engine management, knock sensors and intercooler, 8.5:1 is probably a good start point for a turbo. Unfortunately the 931 has none of those things.

For something that's driven everyday high-compression low-boost. Take a look at the 996 Turbo - 9.4:1 compression.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you
Back to top
View user's profile Send private message Send e-mail
924RACR  



Joined: 29 Jul 2001
Posts: 8794
Location: Royal Oak, MI, USA

PostPosted: Tue Mar 11, 2003 11:46 pm    Post subject: Reply with quote

Don't forget that octane is just as much a factor (remember Rick's rants on Toluene?) and the gas in the US was crap at the time, unleaded with low octane, hadn't figured out properly how to replace the lead.

Now, with the current gas prices, I'm a bit glad my turbo's not demanding premium! 89 is quite sufficient for me!
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype
Back to top
View user's profile Send private message Send e-mail Visit poster's website
sandgroper  



Joined: 07 Dec 2002
Posts: 108
Location: in limbo

PostPosted: Thu Mar 20, 2003 3:02 am    Post subject: Reply with quote

i,m with Aussie Pete,baramundi dude,ahh wanted to check out my ROW 931avatar.
Back to top
View user's profile Send private message
Lizard  



Joined: 03 Nov 2002
Posts: 9364
Location: Abbotsford BC. Canada

PostPosted: Thu Mar 20, 2003 3:40 am    Post subject: Reply with quote

how hard is it to install a knock senser on the 931, and all it does is retart the spark correct
_________________
3 928s,
Back to top
View user's profile Send private message Send e-mail
924RACR  



Joined: 29 Jul 2001
Posts: 8794
Location: Royal Oak, MI, USA

PostPosted: Thu Mar 20, 2003 5:13 am    Post subject: Reply with quote

Depends on your engine management!!!

I think there's something in the tech section on this, using the SAAB engine controller...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype
Back to top
View user's profile Send private message Send e-mail Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    924Board.org Forum Index -> 931 Discussion All times are GMT + 10 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group