IR manifold design

[bill.shurvinton at nokia.com]

Accepted wisdom for 4 pot IR is that at these low RPMs the injectors should be downstream of the butterflies. Upstream only becomes an advantage at 5000+. But like all accepted wisdom is usually based on the fact the IR TB's have their injector pockets in this location:-)

The higher the injector, the bigger the accel squirt needed, so possibly part throttle drivability may decrease, BUT you get better atomisation at WOT. Oh and potentially worse emmissions.

You may have noticed that there are now 8+ variables at play, which will be specific to your install.

Conclusion: I would place them where you can fit them.

Bill

-----Original Message-----
From: ext Ron Schroeder [mailto:rjs at bnl.gov]
Sent: Tuesday, March 12, 2002 12:46 PM
To: diy_efi at diy-efi.org
Subject: IR manifold design


Hi,

I need to build a new manifold for my 4 cyl. inline engine.  The primary
operating range will be 1500 to 4000rpm.  Smoothness is the primary concern.

My major constraint is that the injectors can be no closer than about 6"
from the valves.  Would it be better to place the injectors just upstream or
just downstream of the butterflies (one per runner)?  What are the
advantages / disadvantages of either position?

Thanks

Ron Schroeder
WD8CDH
day 631 344-4561
nite 631 286-5677

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