Measure your pulleys to help everyone?
#1
11-18-2007, 05:13 AM
Measure your pulleys to help everyone?
This is a repeat of a post.
If moderators think the request worthy
please repost this in the appropriate forum.
The general idea is to ask forum membership to collect for the technical archive the sizes of Chrysler pulleys that could be swapped from vehicle to vehicle as an inexpensive way of creating UnderDrive Pulley sets, which can give slight power and fuel economy improvements for engines not operating at the extremes of super-strong power steering or maximum engine cooling.
All help appreciated.
-------
It would be of benefit to all Dodge owners
if the various vehicle owners of different model years
would measure the pulleys on their engines for
outside diameter
shaft diameter
serpentine belt groove numbers
and this info could be compiled in one big list.
There is a slight MPG and power gain from underdrive pulleys
but it is usually not enough to justify $100 to $200
and the situation is even worse if you put some $/hour labor rate
on your own time to do the install.
But much much cheaper prices can be paid at junkyards for pulleys
off vehicles...but only if people can know what pulley sizes are available.
For example, a few years ago it was found that a $59 dealer cost pulley off a Viper V10 could be used as an underdrive pulley for most Dodge V8s
If we get together and build up a table of pulley sizes available
it could save everyone money, time and give performance boosts.
As others have said in posts above
it makes no sense to slow down the alternator
because the horsepower consumed by the alternator
is determined by the
'excitation of the rotor field'
and this comes from the PCM computer's voltage regulation software. Slowing the alternator shaft down just causes problems at idle and doesn't save fuel or improve hp at high rpm.
Consider listing your pulley sizes.
If you know of or see a table of pulley sizes on the internet
post the links or info here.
archived post below
-----
Ok...got the measurements
(outside edge measurement not actual ribs...but you get the picture)
Alternator
96 and Earlier = 2 1/2"
97 and Later = 2 1/4"
ASP Underdrive = 3 1/2"
March Underdrive = 3 3/8
Crank
96 and Earlier = 7 1/4"
97 and Later = 7 1/4"
ASP Underdrive = 5 1/2"
on 1995 5.9V8
alternator 2.75
water pump 5.25
power steering 6.0
-------
a cut from the Ram Pickup MPG improvement FAQ:
----
Underdrive Pulleys
Undersized crank pulleys can increase MPG slightly by driving the power
steering, air conditioning compressor, and water pump at lower rpm where
there will be less friction.
Some who have tried undersized pulley sets report an additional
alternator pulley in a pulley set is generally too slow for the street truck
that may
have to idle a long time without enough rpm to charge the battery.
A pulley that does not slow the alternator down as much as the aftermarket
ones is the factory installed one used on the aluminum block V10 Viper.
This is DC Part Number 5037204AB for a 2003-2007 Ram SRT10 crank
pulley, which usually runs about $60 retail at most Dodge dealerships and
less at discount dealers like Koller.
There have been some warnings posted that the underdrive pulleys for
5.7 Hemi's do not have a torsional damper of correct design. Beware.
Breaking a crankshaft out of warranty is not fun or cheap.
The horsepower that an alternator consumes is
mostly set not by the rpm it turns, but by how much the 'voltage regulator'
inside the Ram pickups PCM computer increases the 'excitation field current'
inside the alternator's rotor. Because of this I see no benefit in slowing an
alternator down - no significant horsepower will be saved or fuel economy
gained. The AC compressor can be simply turned off when you want either
more power or better MPG. NASCAR cooling system guru Howard Stewart
points out that on modern engines like the Chrysler 4.7/5.7 with knock
sensors, if you slow down the water pump you might have more horsepower
for the first few seconds at Wide Open Throttle, but then the cylinder head
will begin overheating at its worst spot, some pinging will start, the knock
sensors will trigger, and the PCM computer will start pulling back up to
16 degrees of ignition timing advance - then the horsepower declines
much more than you "saved" with the water pump pulley reduction.
If you must change pulleys it is best to just slow down the power steering
pump alone.
If moderators think the request worthy
please repost this in the appropriate forum.
The general idea is to ask forum membership to collect for the technical archive the sizes of Chrysler pulleys that could be swapped from vehicle to vehicle as an inexpensive way of creating UnderDrive Pulley sets, which can give slight power and fuel economy improvements for engines not operating at the extremes of super-strong power steering or maximum engine cooling.
All help appreciated.
-------
It would be of benefit to all Dodge owners
if the various vehicle owners of different model years
would measure the pulleys on their engines for
outside diameter
shaft diameter
serpentine belt groove numbers
and this info could be compiled in one big list.
There is a slight MPG and power gain from underdrive pulleys
but it is usually not enough to justify $100 to $200
and the situation is even worse if you put some $/hour labor rate
on your own time to do the install.
But much much cheaper prices can be paid at junkyards for pulleys
off vehicles...but only if people can know what pulley sizes are available.
For example, a few years ago it was found that a $59 dealer cost pulley off a Viper V10 could be used as an underdrive pulley for most Dodge V8s
If we get together and build up a table of pulley sizes available
it could save everyone money, time and give performance boosts.
As others have said in posts above
it makes no sense to slow down the alternator
because the horsepower consumed by the alternator
is determined by the
'excitation of the rotor field'
and this comes from the PCM computer's voltage regulation software. Slowing the alternator shaft down just causes problems at idle and doesn't save fuel or improve hp at high rpm.
Consider listing your pulley sizes.
If you know of or see a table of pulley sizes on the internet
post the links or info here.
archived post below
-----
Ok...got the measurements
(outside edge measurement not actual ribs...but you get the picture)
Alternator
96 and Earlier = 2 1/2"
97 and Later = 2 1/4"
ASP Underdrive = 3 1/2"
March Underdrive = 3 3/8
Crank
96 and Earlier = 7 1/4"
97 and Later = 7 1/4"
ASP Underdrive = 5 1/2"
on 1995 5.9V8
alternator 2.75
water pump 5.25
power steering 6.0
-------
a cut from the Ram Pickup MPG improvement FAQ:
----
Underdrive Pulleys
Undersized crank pulleys can increase MPG slightly by driving the power
steering, air conditioning compressor, and water pump at lower rpm where
there will be less friction.
Some who have tried undersized pulley sets report an additional
alternator pulley in a pulley set is generally too slow for the street truck
that may
have to idle a long time without enough rpm to charge the battery.
A pulley that does not slow the alternator down as much as the aftermarket
ones is the factory installed one used on the aluminum block V10 Viper.
This is DC Part Number 5037204AB for a 2003-2007 Ram SRT10 crank
pulley, which usually runs about $60 retail at most Dodge dealerships and
less at discount dealers like Koller.
There have been some warnings posted that the underdrive pulleys for
5.7 Hemi's do not have a torsional damper of correct design. Beware.
Breaking a crankshaft out of warranty is not fun or cheap.
The horsepower that an alternator consumes is
mostly set not by the rpm it turns, but by how much the 'voltage regulator'
inside the Ram pickups PCM computer increases the 'excitation field current'
inside the alternator's rotor. Because of this I see no benefit in slowing an
alternator down - no significant horsepower will be saved or fuel economy
gained. The AC compressor can be simply turned off when you want either
more power or better MPG. NASCAR cooling system guru Howard Stewart
points out that on modern engines like the Chrysler 4.7/5.7 with knock
sensors, if you slow down the water pump you might have more horsepower
for the first few seconds at Wide Open Throttle, but then the cylinder head
will begin overheating at its worst spot, some pinging will start, the knock
sensors will trigger, and the PCM computer will start pulling back up to
16 degrees of ignition timing advance - then the horsepower declines
much more than you "saved" with the water pump pulley reduction.
If you must change pulleys it is best to just slow down the power steering
pump alone.