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Forced Induction (question by AnzDrgn)

 
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Peter_in_AU  



Joined: 29 Jul 2001
Posts: 2740
Location: Sydney, Australia

PostPosted: Mon Jul 30, 2001 12:18 pm    Post subject: Reply with quote

Quote:

How would a forced air intake for a 924 na work? Normally you just force the air into the intake box, but in this case there is that air flow sensor. If you force air into there you end up making the sensor give false readings about the air flow and makes the fuel mix wrong. So any idea's on how to keep the correct fuel mix and add forced air intake?


Basically your super/turbocharger is set up to suck not blow (there's a couple of great jokes just waiting there).

With a turbo, the turbo and intercooler sit between the airflow sensoring gear and the throttle body. A supercharger normally sits between the throttle body and the inlet manifold.

In either case, the airflow metering gear (electronic or mechanical, doesn't matter) sees the engine sucking lots and lots of air and adjusts the fuel accordingly.

The 924 CIS metering/injection should cope with "reasonable" boost (the 931 does) but if you go above 1 bar (~15psi) you're going to need more fuel. That's why Porsche used the 928 fuel distributor on the 924 GT variants.



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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
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AppleBit  



Joined: 16 Nov 2002
Posts: 1516
Location: Minneapolis, MN

PostPosted: Mon Jul 30, 2001 4:53 pm    Post subject: Reply with quote

Look at my website. You'll see an intake system you can use. Basically if it is reading false air it will just make your car run a little richer, but you're not going to get it to do that... You'd need to drive 200 mph and have a more direct intake system to do that. This more allows you to get air from outside the engine bay...


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924RACR  



Joined: 29 Jul 2001
Posts: 8102
Location: Royal Oak, MI, USA

PostPosted: Mon Jul 30, 2001 11:47 pm    Post subject: Reply with quote

Just to clarify - the performance improvement comes from getting colder air into the engine, as noted it will not be possible to raise the pressure of the incoming air significantly.

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Vaughan Scott
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'79 924 #77 ITB racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype
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Peter_in_AU  



Joined: 29 Jul 2001
Posts: 2740
Location: Sydney, Australia

PostPosted: Tue Jul 31, 2001 12:33 am    Post subject: Reply with quote

ahhhh, got it! We're basically talking cold air intakes here. Down here "forced induction" is taken to mean turbo- or super-charging.

Take a look at http://www.autospeed.com/A_1023/page1.html for an interesting way of finding the best place to put the intake. Worth a read if your looking to make the most of the air pressure.



_________________
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
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Manouchehr  
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PostPosted: Tue Jul 31, 2001 2:51 am    Post subject: Reply with quote

Hi all,

can anyone please comment on the performance increase (if any) through "forced induction". i.e. has anyone tried getting air from someplace else than the snorkel?
Thanx!
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Cbass  
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PostPosted: Wed Mar 06, 2002 8:04 pm    Post subject: Reply with quote

Ah, I see you have been to autospeed as well. To clear something up, forced induction refers only to turbo and supercharging. Cold air and Ram air intakes are not forced induction.
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AznDrgn  
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PostPosted: Thu Mar 07, 2002 3:47 am    Post subject: Reply with quote

WOW, how did this pop up again?
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numbers  
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PostPosted: Thu Mar 07, 2002 7:41 am    Post subject: Reply with quote

Manouchehr, on my 931, I have cut the front out of a spare lower airbox and removed and sealed the horn. This lets the cold air from the badge panel openings flow directly into the airbox. I did this last year, and have not really noticed any real improvement in performance.
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