Rick:
This is a very good mod, and it is sooo easy. Yes, your numbers
are
right. 4 HP for free, or so it seems.
At some point, bigger is not better, as the tube is not a
restriction and
the velocity of the air in the pipe is low enough that it begins to heat
up on
it's way to the carbs (i.e. it has time to absorb heat from it's
surroundings). Not
likely with the size you have used, and it is plenty big enough to not
be a restriction
to the airflow.
As for the carb calibrations, they will change slightly. Your
mixture will
tend to lean out a bit, since the density of the air goes up.
Carburetors add fuel based on the VOLUME of air that flows
through them.
The ZS makes some attempt to correct this with the temperature
compensators, but
these are primarily effective at idle. As the air cools, the MASS of air
increases,
but the volume the engine uses stays the same (i.e. the DENSITY of the
air increases).
The ZS carbs will see the same VOLUME, and add the same amount of fuel,
but because the
mass has gone up, the mixture becomes too lean.
This is where EFI shines. If you have a MAF (Mass air flow)
sensor, you directly
measure the mass. If you have a MAP (Manifold Air Pressure) sensor and
an air temperature
sensor you can compute the mass of the incoming air charge. Pretty
spiffy.
Anyway, it is a great little mod. The Euro spec TR6s came stock
with this feature.
The poor Yankees got the castrated version of the car. Too bad.
Vance
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of richard.r.olson@faa.gov
Sent: Monday, August 23, 2004 8:04 AM
To: 6pack@autox.team.net
Subject: Air cleaner mods
Has anyone experimented with modifying the air cleaner intake to grab
fresh/cooler air in front of the shroud? I was thinking along the lines
of
the earlier 6/Spitfire<?> with the two small diameter hoses running
between
the AC housing and the shroud. I recently fabbed a sheet metal 'snout'
on
to the front of my spare AC. It terminates in a 4" diameter tube which
is
connected via rubber (sewer pipe!) connector through a hole in my
aluminum
shroud. I also opened up the two rectangular holes on the front of the
AC
a bit. The math shows that the old opening (including the bottom rear
opening) was ~8.5 sq inches. The revised opening is ~12 sq inches.
Question: Bigger is better? As in more air flow.
Question: Will this have an effect on the A/F ratio (good or bad)
I've read a little about the theoretical 1% increase in HP for each 11
degree drop in temp(related to air density). I've measured my air
temps.
Inside the stock AC it was ~125 degrees F after a 20 minute drive, while
the air temperature in front of the shroud was ambient (77 that day).
Question: 48 degree drop gives me 4 more HP? What's the catch?
Like I said in my last post - I've got too much time on my hands....
Rick Olson 'digesting'
'72 TR6 - CC78827U/HVDA
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