UDP worth it?
RE: UDP worth it?
ORIGINAL: Kalevra
the bold words without a caption I admit I didn't know I was misspelling. sorry. the captions will tell it all and why it was misspelled. though, the minor misspellings should not have effected the point I was making, I'm not Mr. perfect, or always right, but you're going to discredit my point just because of some spelling errors that didn't take away from the readability of the statement above? I hate those who are always grammatically correct and discredit everyone who is not. that's just like being racist, you racist bastard 
ORIGINAL: Swordfish2Cowboy
I'm sorry any argument you may have had went out the window when I saw your atrocious spelling.
ORIGINAL: Kalevra
if (typo) the UDP smaller than the stock one? if so it would be spinning (typo) the belt a lot less therefore everything that gets power from the belt it's efficiently will be cut dramatically whether or not the other pulleys are changed, simple pulley theory or should I say rotational theory(typo, sorry)... the bigger the wheel or pulley, the more distance it will travel with one rotation, the smaller the less the distance. say the pully is 10 inches around, that means for every rev the belt moves 10 inches, and same with an 8 inches, it will move 8 inches/ revolution therefor reducing efficiency, turning the belt less and there for turning the other pulleys less
So, in conclusion, IF the pulley is smaller than stock then it will reduce the efficiency (another typo) of all the accessories on that belt. that means, AC, alt, pwr steering (donno what I was thinking there), everything due to the belt spinning slower because of a smaller UDP
EDIT: wow, I think I just outsmarted 03RT
if (typo) the UDP smaller than the stock one? if so it would be spinning (typo) the belt a lot less therefore everything that gets power from the belt it's efficiently will be cut dramatically whether or not the other pulleys are changed, simple pulley theory or should I say rotational theory(typo, sorry)... the bigger the wheel or pulley, the more distance it will travel with one rotation, the smaller the less the distance. say the pully is 10 inches around, that means for every rev the belt moves 10 inches, and same with an 8 inches, it will move 8 inches/ revolution therefor reducing efficiency, turning the belt less and there for turning the other pulleys less
So, in conclusion, IF the pulley is smaller than stock then it will reduce the efficiency (another typo) of all the accessories on that belt. that means, AC, alt, pwr steering (donno what I was thinking there), everything due to the belt spinning slower because of a smaller UDP
EDIT: wow, I think I just outsmarted 03RT
Record Breaker
Joined: Feb 2007
Posts: 1,506
Likes: 0
From:
RE: UDP worth it?
ORIGINAL: Swordfish2Cowboy
Nah, it's not like I discredited what you were saying because of your spelling and grammar, just that I didn't read it. Reading it again, I see your point. But wouldn't they make a pulley the same size as the existing one?
ORIGINAL: Kalevra
the bold words without a caption I admit I didn't know I was misspelling. sorry. the captions will tell it all and why it was misspelled. though, the minor misspellings should not have effected the point I was making, I'm not Mr. perfect, or always right, but you're going to discredit my point just because of some spelling errors that didn't take away from the readability of the statement above? I hate those who are always grammatically correct and discredit everyone who is not. that's just like being racist, you racist bastard
ORIGINAL: Swordfish2Cowboy
I'm sorry any argument you may have had went out the window when I saw your atrocious spelling.
ORIGINAL: Kalevra
if (typo) the UDP smaller than the stock one? if so it would be spinning (typo) the belt a lot less therefore everything that gets power from the belt it's efficiently will be cut dramatically whether or not the other pulleys are changed, simple pulley theory or should I say rotational theory(typo, sorry)... the bigger the wheel or pulley, the more distance it will travel with one rotation, the smaller the less the distance. say the pully is 10 inches around, that means for every rev the belt moves 10 inches, and same with an 8 inches, it will move 8 inches/ revolution therefor reducing efficiency, turning the belt less and there for turning the other pulleys less
So, in conclusion, IF the pulley is smaller than stock then it will reduce the efficiency (another typo) of all the accessories on that belt. that means, AC, alt, pwr steering (donno what I was thinking there), everything due to the belt spinning slower because of a smaller UDP
EDIT: wow, I think I just outsmarted 03RT
if (typo) the UDP smaller than the stock one? if so it would be spinning (typo) the belt a lot less therefore everything that gets power from the belt it's efficiently will be cut dramatically whether or not the other pulleys are changed, simple pulley theory or should I say rotational theory(typo, sorry)... the bigger the wheel or pulley, the more distance it will travel with one rotation, the smaller the less the distance. say the pully is 10 inches around, that means for every rev the belt moves 10 inches, and same with an 8 inches, it will move 8 inches/ revolution therefor reducing efficiency, turning the belt less and there for turning the other pulleys less
So, in conclusion, IF the pulley is smaller than stock then it will reduce the efficiency (another typo) of all the accessories on that belt. that means, AC, alt, pwr steering (donno what I was thinking there), everything due to the belt spinning slower because of a smaller UDP
EDIT: wow, I think I just outsmarted 03RT
Champion
Joined: Aug 2005
Posts: 3,313
Likes: 8
RE: UDP worth it?
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 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.
