[F500] 493 Rotax

[David Pomfret]

The Rotax 493 is a liquid cooled, twin cylinder with Reed Valve R.A.V.E. Apparently it has a 499 cc displacement with a 69.5 mm/2.7 in bore X 65.8 mm/2.6 in stroke, uses two Mikuni VM38 carbs and a single tuned pipe exhaust.

Dave Pomfret










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[dphaneu at attglobal.net ()]

I can see the 493 vs 494 shake out as argument of those
that already have 494s vs. those looking to upgrade from
AMW or Kawasaki power.
I suspect the class has already dealt with this a few times
when AMW and then Rotax came up for approval.
If a new engine is approved it'll likely get a weight
penalty or a restricted intake (smaller carbs?) to try
and keep it on par with the current 494s. It would be good
for the class to keep new motors available, but also important
not to obsolete the existing engines.
I also don't find any 494 non rave valved engines
available used out of snowmobiles. We may not have a
shortage yet, but there's no surplus laying around either!
Dave Phaneuf

[O.S. Brannon]

Well stated, Dave.

-- Original Message --
Subject: [F500] 493 Rotax
Date: Mon, 11 Nov 2002 11:41:37 -0500
I can see the 493 vs 494 shake out as argument of those
that already have 494s vs. those looking to upgrade from
AMW or Kawasaki power.
I suspect the class has already dealt with this a few times
when AMW and then Rotax came up for approval.
If a new engine is approved it'll likely get a weight
penalty or a restricted intake (smaller carbs?) to try
and keep it on par with the current 494s. It would be good
for the class to keep new motors available, but also important
not to obsolete the existing engines.
I also don't find any 494 non rave valved engines
available used out of snowmobiles. We may not have a
shortage yet, but there's no surplus laying around either!
Dave Phaneuf
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O.S. Brannon
Manager, AAA Auto Club South
Heathrow Service Center
Phone [phone]
Fax [phone]

[dphaneu at attglobal.net ()]

Almost forgot...
How many people are going to rush out and buy
a 493 for regionals only? With out some assurances
from SCCA that it will be "fully " approved the following
season I don't see it happening.
A 95-100hp F500 should finally outrun the fords though!
Dave Phaneuf

[Gebhardt, Robert (R.)]

I agree. There aren't even exhaust pipes available for these things yet. It
sounds like this motor would phase in naturally. Although, I still question
whether it's really got that much more power.

Bob Gebhardt

-----Original Message-----
From: ***@attglobal.net [mailto:***@attglobal.net]
Sent: Monday, November 11, 2002 11:54 AM
To: ***@www.f500.org
Subject: [F500] 493 Rotax


Almost forgot...
How many people are going to rush out and buy
a 493 for regionals only? With out some assurances
from SCCA that it will be "fully " approved the following
season I don't see it happening.
A 95-100hp F500 should finally outrun the fords though!
Dave Phaneuf

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[Gerald Ryan]

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[Bob Jordan]

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[jryall at juno.com ()]

My understanding is that the motor, as installed in a sled, does have
that often quoted 10% more horsepower, but that is with flat slide carbs
that alone are worth about 7 hp, and they are also larger then the 38 mm
carbs now permitted. Once the engine is running on the 38mm round slide
carbs, there is supposedly no hp advantage. The comparison chart I have
shows the 494 has about 79 hp at 7500 rpm, and the 493 has the same at
8000 rpm. The 493 shows more torque at low rpms (until 6000 rpm), then
again above 7600 rpm, but not a major gain.

John Ryall


On Mon, 11 Nov 2002 12:21:35 -0500 "Gebhardt, Robert (R.)"

Post by Gebhardt, Robert (R.)
I agree. There aren't even exhaust pipes available for these things
yet. It
sounds like this motor would phase in naturally. Although, I still
question
whether it's really got that much more power.
Bob Gebhardt

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[Dave Phaneuf]

Is the new 493 engine a "case reed" intake or are the
carbs and reeds feeding the cylinders?
Thanks
Dave Phaneuf

[NEAL98 at aol.com ()]

Dave,

As per Snowmobiler magazine..


"The cylinder mounted reed cage has a very large intake area and is
really a hybrid between cylinder reed intake and case reed intake, with 70% of
the intake charge going directly to the crankcase and only 30% of the charge
going under the piston skirt."

[Art]

Dave,

The reed valve is part of the carburetor system. If anyone buys a used
engine before or after the 2000 model year, they will have to change the
reed valve as well as the carbs(40 mm). The 2000 model year was the only
year the 493 came with 38mm Mikuni carbs.

Art

-----Original Message-----
From: f500-bounces+qreshadow=***@f500.org
[mailto:f500-bounces+qreshadow=***@f500.org] On Behalf Of Dave
Phaneuf
Sent: Monday, January 17, 2005 8:57 AM
To: ***@f500.org
Subject: [F500] 493 Rotax

Is the new 493 engine a "case reed" intake or are the carbs and reeds
feeding the cylinders?
Thanks
Dave Phaneuf
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[Dave Phaneuf]

Thanks Art, I thought they all had 40mm carbs, not that I
can find any.....lots of 494 rave engines avail though.
Dave