Thread: type 930/64
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356-930 356-930 is offline
Acceleration Junkie
Join Date: Aug 2007
Location: Laguna Beach, CA
Posts: 263
Originally Posted by nocarrier View Post
The problem i see is being that my engine has been modified; If I use the stock injector pieces it will create a step in the port. There will be a step on the manifold side 4.44mm and a step on the head side 5.00mm in such a short distance.
I think I am going to have to bite the bullet and buy a set of aluminum blocks
I recommend you take a look at an unmodified 930 engine. There is a major step built into the design.
Synopsis of “Stupid Inlet Spacers”

Post by JFairman - They used small ports on the 930 to speed up intake velocity at lower speeds.
That improves low speed driving, makes a smoother idle and keeps CIS fuel spray from the injectors atomized better.

Post by billjam - I figured there had so be some sound engineering reason behind the small port size - damn it - don't you just hate those Germans!!

Post by Spuggy. +1 what JFairman says...
Chap, you might need to revisit gas flow theory...
Small inlet tracts, small throttle body and small valves all make for better throttle response - and more torque & tractability - at lower RPM because the velocity of the gas at part throttle is faster than it would otherwise be. Downside is that it strangles the motor at the top end.
Big problem on an N/A motor, not so much with forced induction.
Opening up the ports and using larger valves doesn't improve low end, it improves the top-end by allowing more gas to flow at large throttle openings, but at the expense of off-boost response and tractability.

Post by beepbeep - Reason for 32mm ports is off-boost torque. Engine has 7:1 C/R and is a pig w/o boost, delivering staggering 120hp w/o the huffer.
Porsche used those strangled intakes to improve gas velocity and thus cylinder filling at low load.

Post by billjam - It's interesting that Porsche reduced the size of the isolators at some stage.
It kind of indicates that they may have had some power or driveability issues as implied by beepbeep and spuggy.

Post by RarlyL8 - I would not modify the stock phenolic injector blocks. They are already stressed with age and heat.
As many have already said, the stock 32mm intake path is helful for low end. The stock intake and heads will support 375+WHP. Porting the exhaust ports can help bump you past 400WHP.
I see no reason to mess with intake side unless you want 425+WHP. At that point most go to EFI and change everything.

My take is that unless you’re building a 1/4-mile drag car, or pushing for over 375RWHP, you may wind up exacerbating your low end power curve by installing larger ID injector blocks.
Old 07-29-2008, 09:55 AM
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