|
On further review,
TB size should have no affect on throttle response at all in an ijected system.
In our carbed engines, rapid throttle opening drops manifold pressure
to ambiant and flow through the booster venturi is not adequate to
match the fuel flow to the throttle position and the engine falls on
its face for lack of fuel. Thus the accellerator pump and jet system,
which pees a long stream of fuel into the hole while the engine winds
up enough revs (and air flow) to engage the boosters and get a fuel
mist pouring into the carb.
No such drama should be required in the injected engine. Should the TB
open in less than X amount of time could not the injectors closest to
the engine stand wide open for one or two revolutions, or cycles? Or
even just some period of time longer than normal?
So, it should not matter at all how big the TB is, as it is not even
required until you want to slow or shut down the engine. If there is a
butterfly in the inlet tract, the tuned length is usually figured from
that, and not the total length as from the opening into the air filter
or inlet bell. Notice the slide valve throttles on big time race
engines. No affect on the tuned length. That throttle shaft and
butterfly screws up the tune, and shortens the tuned length.
On the old Formula Continental engines, stock 1600CC VW water cooled
engines with the heads and decks shaved to give huge compression with
stock parts, the injection was free. So what did the smart people use
for injection? High pressure mechanical with high pop pressure
injectors, that shot a nasty looking stream of fuel, not a nice fog of
fuel at all. The injectors were mounted in the center of long bell
shapes, and that fast moving stream of fuel was part of an
ejector system that was used to boost airflow to the tune (pun) of 175
HP from a 54 HP VW Rabbit engine.
So the bigger the TB the less it should affect the tuned length, and
conversly the smaller the TB the more it should affect the tuned
length.
For a reference the difference between carbed and injected
engines with a restrictor in the injected system the same size as the
choke in the carbed engine as 5 to 8 HP. This is mostly the loss of the
booster venturi in the center of the hole.
The improvement in a carbed engine between 36MM and 38MM chokes is about 5 HP. Per Daryl Drummond. Race engine builder.
Is this fun to think about or what?
Lynn E.Hanover
----- Original Message -----
Sent: Tuesday, May 01, 2007 12:27
PM
Subject: [FlyRotary] Re: Throttle body
size/ other "Paul" issues
Interesting Lynn,
For the comparison that is 2,035 square mm inlet area. Assuming the
bigger 13B could use 1/3 More inlet area the total would be 2,646 square mm.
The inlet area of the 65 mm throttle body is 3,318 square mm. Seems like
a 65 mm TB would be more than up to the task. A 60 mm TB is 2,827 square
mm for reference. Plenty big Buly
Bill Jepson
-----Original Message-----
From:
lehanover@aol.com
To: flyrotary@lancaironline.net
Sent: Tue, 1 May 2007
9:08 AM
Subject: [FlyRotary] Re: Throttle body size/ other "Paul"
issues
Two 36MM chokes is enough for 244.8 HP at 9,400 RPM, and About 176 HP at
7,000 RPM. I am in California and the dyno sheet is in Hebron Ohio. But I can
quote it when I get back if it would help anyone.
Lynn E.
Hanover
|