Blower Motor All The Way Upgrade
08-13-2005, 01:57 AM
#1
Melting Slicks
Thread Starter
Blower Motor All The Way Upgrade
The purpose of this topic is to see what it will take to go all the way in getting one of the faster 3,000+ RPM motors adapted to replace our weak A/C-Heater blower. Even the C4 blowers are only reving at 1800RPM.
Yes...an upgrade for the blower motor is an old topic. But, no...it hasn't been completely finished...very few people have been totally satisfied with the over the counter replacements. There's been members who have purchased a C4 motor with fan and made a 1" spacer so that the longer fan will not be a problem, but some of those who have made this swap have not been happy.
I've done some investigating and still don't have all of the answers. I went to the Siemans web site since Autozone carries a new blower from Siemans with part # PM102 for $20.99 without the fan as an OEM replacement for our vettes and requires no mods. They also stock the C4 blower motor which comes with the fan Siemans part # PM137 for $33.99 which requires the spacer. But, I couldn't get any specs on them.
Now...the part that I'm really confused about is the RPM ratings. I saw one post which rated our original factory motors at like 1,400 RPM while the new one had 1,800 RPM...not really sure of the numbers. The thing is that the Siemans web site lists blower motors for like Audi, Volkswagon, Ford, etc. that have a RPM of 3,000+. What's the deal? Why isn't there a nice motor for our vettes? Why do we have to settle for 1/2 the speed of all the other cars? I don't get it. Here is the Siemans spec:
http://www.vdo.com/siemens/sycomax/u...VAC_UK_Web.pdf
Notice that it doesn't list the models for our cars. I still cannot locate any specs for the motors for our cars.
It seems to me that we need to do some work on our own. 1400RPM to 1800RPM just isn't enough of an increase for the work involved. If we have to do some customization, then let's get a motor that really rocks...something that's twice as fast...and just fabricate the mount...I mean...we would have to fabricate a spacer, so a mount isn't that much worse. I won't mind doing a little welding either.
Anyone have any thoughts? I'm going to visit my local autozone and see if I can take a look at their stock of motors...see if they have the RPMs printed on the cases...see what would be required to adapt a better motor to one of our mounts.
Yes...an upgrade for the blower motor is an old topic. But, no...it hasn't been completely finished...very few people have been totally satisfied with the over the counter replacements. There's been members who have purchased a C4 motor with fan and made a 1" spacer so that the longer fan will not be a problem, but some of those who have made this swap have not been happy.
I've done some investigating and still don't have all of the answers. I went to the Siemans web site since Autozone carries a new blower from Siemans with part # PM102 for $20.99 without the fan as an OEM replacement for our vettes and requires no mods. They also stock the C4 blower motor which comes with the fan Siemans part # PM137 for $33.99 which requires the spacer. But, I couldn't get any specs on them.
Now...the part that I'm really confused about is the RPM ratings. I saw one post which rated our original factory motors at like 1,400 RPM while the new one had 1,800 RPM...not really sure of the numbers. The thing is that the Siemans web site lists blower motors for like Audi, Volkswagon, Ford, etc. that have a RPM of 3,000+. What's the deal? Why isn't there a nice motor for our vettes? Why do we have to settle for 1/2 the speed of all the other cars? I don't get it. Here is the Siemans spec:
http://www.vdo.com/siemens/sycomax/u...VAC_UK_Web.pdf
Notice that it doesn't list the models for our cars. I still cannot locate any specs for the motors for our cars.
It seems to me that we need to do some work on our own. 1400RPM to 1800RPM just isn't enough of an increase for the work involved. If we have to do some customization, then let's get a motor that really rocks...something that's twice as fast...and just fabricate the mount...I mean...we would have to fabricate a spacer, so a mount isn't that much worse. I won't mind doing a little welding either.
Anyone have any thoughts? I'm going to visit my local autozone and see if I can take a look at their stock of motors...see if they have the RPMs printed on the cases...see what would be required to adapt a better motor to one of our mounts.
08-13-2005, 02:45 AM
#2
Race Director
Member Since: Sep 2002
Location: San Diego - Deep Within The State of CONFUSION!
Posts: 10,362
Likes: 0
Received 2 Likes
on
2 Posts
Originally Posted by Rockn-Roll
Anyone have any thoughts? I'm going to visit my local autozone and see if I can take a look at their stock of motors...see if they have the RPMs printed on the cases...see what would be required to adapt a better motor to one of our mounts.
On either medium-high, or high, I'm comfortable even when it's 90* outside.
The following users liked this post:
tiger38117 (07-26-2019)
08-13-2005, 08:31 AM
#4
Team Owner
R&R, I learned quite a bit from a HVAC guy about fan engineering, he had rooms full of books on the subject....
it's NOT all in the motor rpm, but like car engines, the torque load the thing can take...meaning the pitch and diameter of the squirrel cage blades....so it's the amount of blades, also....
without comparing those charactoristics, and getting an airflow reading with a constant backpressure and suction restriction you can't really compare them apples to apples so to speak....
it's is a guessing game....
also figger on the amount of work being done, moving a air volume through our systems, more air, more work, more air speed, more work, meaning more amps be drawn....my C4 blower started working my 30 amp fuse too hard, I changed the fuse clip and put in a new fuse, changed styles, still overworked the 30 amp fuse....so I put in a 40 amp fuse....case closed....runs fine....
now does that mean more work being done?? maybe, allthough spinning the fan faster MAY be able to move more air, just doing that alone will cause cavitation, just like a prop in water with too much power applied for the speed of the boat....which would occur in our blowers if the suction side was too restricted....
not such a simple topic, obviously...
GENE
it's NOT all in the motor rpm, but like car engines, the torque load the thing can take...meaning the pitch and diameter of the squirrel cage blades....so it's the amount of blades, also....
without comparing those charactoristics, and getting an airflow reading with a constant backpressure and suction restriction you can't really compare them apples to apples so to speak....
it's is a guessing game....
also figger on the amount of work being done, moving a air volume through our systems, more air, more work, more air speed, more work, meaning more amps be drawn....my C4 blower started working my 30 amp fuse too hard, I changed the fuse clip and put in a new fuse, changed styles, still overworked the 30 amp fuse....so I put in a 40 amp fuse....case closed....runs fine....
now does that mean more work being done?? maybe, allthough spinning the fan faster MAY be able to move more air, just doing that alone will cause cavitation, just like a prop in water with too much power applied for the speed of the boat....which would occur in our blowers if the suction side was too restricted....
not such a simple topic, obviously...
GENE
08-13-2005, 09:09 AM
#5
Safety Car
speed ? what about shape !
Hi, I just replaced the blower motor in my 9C1 Caprice ex-cop car and saw that the cage was shorter then the old one but the fins were wider and curved more. it seems to work just as well as the old one, maybe a faster spinning motor is not what will produce more airflow. I have no scientific data to add only seat of the pants observations.
So,,, mull that over and see if it seems logical,,,Peace,, Craig
So,,, mull that over and see if it seems logical,,,Peace,, Craig
08-13-2005, 03:29 PM
#6
Melting Slicks
Thread Starter
Thanks SanDiegoPaul. I did a complete removal and seal of my ducting when I replaced my heater core...I can feel no leaks and the ducts are completely clear. You are right that it's the first thing to check. I do get comfortable after awhile, but here in Sacramento CA just walking from an air conditioned office and opening the door to the outside feels just like opening the door to an oven set at 250ºF. When I get in my car I'd like to get a frosty breeze blowing to cool me down quickly. I know that my A/C system is doing it's job because my evaporator lines get frosted up...indicating that the air at the evaporator is as low as 32ºF...I believe mostly due to the lack of air flow to take that cold air away from the area causing a build-up of colder air. Hence, I need more air flow.
Ah yes mrvette...thanks for posting...as always you have some good technical information to share. I was looking at the specs on the Siemens blowers and the wattages were like around 100. At 12 volts this would be somewhere in the neighborhood of 10amps. But, if you were blowing your 30amp fuse then that may indicate that the new blowers are consuming more current and thus causing the resistors to consume more power Power=current^2 * Resistance. Even an extra 2 amps would greatly increase the power consumption at those resistors due to the squaring of the current.
Which this extra power consumption in mind I think it would be wise to rewire the blower motor with some larger gauge wire and re-engineer the resistors...I'm thinking perhaps a rheostat might be nice...to get a full range of variable speeds. Of course this would mean replacing the three-way switch with a **** and modifying the center console, but I think it would be a great improvement over what we now have.
Yes you are right about the fan itself being an issue, which is why just getting a faster motor may not completely improve our weak stock air flow. You are also right about the motor torque, and I may have to experiment with several motor/fan combos in order to find one that can move the most air under load.
Though I must disagree about cavitation. Cavitation is where the low pressure created at the underside of the fan blades causes water to boil and creates water vapor bubbles which "pop" as they reach higher pressure areas...high speed turbines have to be very cautious about this because a pump system can become saturated with these bubbles and destroy a pump in just a year.
Here's a quote from my Fluid Mechanics book, "For example, the vapor pressure of water at 50ºF is .178PSIA. Therefore, if the pressure within the water at that temperature is reduced to that value, the water boils. Such boiling often occurs in flowing liquids, such as on the suction side of a pump. When such boiling does occur in flowing liquids, vapor bubbles start growing in local regions of very low pressure and then collapse in regions of higher pressure downstream. The phenomenon, which is called cavitation, is discussed in Chapter 5."
So...no...cavitation is not a concern. The only thing to worry about when dealing with gases such as air, is when air speed reaches the speed of sound...I doubt that we will be seeing supersonic speeds in our ducts.
I also think it’s not a guessing game, but an engineering problem…an easy one compared to the “Rocket Science” that I had to learn in Fluid Mechanics.
Yes moosie982, I think we can look at other cars for motors that will kick some cooling butt. Well, not Fords, but other GM cars especially SUV’s which have a higher requirement for air flow. It’s very possible that the mounting brackets will be the same. Oh…another thought I had was to get a 1970’s Cadillac A/C blower motor. As I understand it all the GM A/C systems were identical to reduce costs of tooling up for each model they released. The difference then would be in the air flow presented by the blower. I figure perhaps a Cadillac blower will mate up perfectly, but have much better flow.
Ah...never mind. I just checked Autozone, and the Cadillac blower is the exact same as our vette blower...part # PM102.
But, another interesting thing is that the Cadillac fan (wire cage, whatever) which attaches to the motor is available for the cadillac part # 35530, but not for the vette. So, I'm not sure if the Cadillac fan is the same...should be though.
Ah yes mrvette...thanks for posting...as always you have some good technical information to share. I was looking at the specs on the Siemens blowers and the wattages were like around 100. At 12 volts this would be somewhere in the neighborhood of 10amps. But, if you were blowing your 30amp fuse then that may indicate that the new blowers are consuming more current and thus causing the resistors to consume more power Power=current^2 * Resistance. Even an extra 2 amps would greatly increase the power consumption at those resistors due to the squaring of the current.
Which this extra power consumption in mind I think it would be wise to rewire the blower motor with some larger gauge wire and re-engineer the resistors...I'm thinking perhaps a rheostat might be nice...to get a full range of variable speeds. Of course this would mean replacing the three-way switch with a **** and modifying the center console, but I think it would be a great improvement over what we now have.
Yes you are right about the fan itself being an issue, which is why just getting a faster motor may not completely improve our weak stock air flow. You are also right about the motor torque, and I may have to experiment with several motor/fan combos in order to find one that can move the most air under load.
Though I must disagree about cavitation. Cavitation is where the low pressure created at the underside of the fan blades causes water to boil and creates water vapor bubbles which "pop" as they reach higher pressure areas...high speed turbines have to be very cautious about this because a pump system can become saturated with these bubbles and destroy a pump in just a year.
Here's a quote from my Fluid Mechanics book, "For example, the vapor pressure of water at 50ºF is .178PSIA. Therefore, if the pressure within the water at that temperature is reduced to that value, the water boils. Such boiling often occurs in flowing liquids, such as on the suction side of a pump. When such boiling does occur in flowing liquids, vapor bubbles start growing in local regions of very low pressure and then collapse in regions of higher pressure downstream. The phenomenon, which is called cavitation, is discussed in Chapter 5."
So...no...cavitation is not a concern. The only thing to worry about when dealing with gases such as air, is when air speed reaches the speed of sound...I doubt that we will be seeing supersonic speeds in our ducts.
I also think it’s not a guessing game, but an engineering problem…an easy one compared to the “Rocket Science” that I had to learn in Fluid Mechanics.
Yes moosie982, I think we can look at other cars for motors that will kick some cooling butt. Well, not Fords, but other GM cars especially SUV’s which have a higher requirement for air flow. It’s very possible that the mounting brackets will be the same. Oh…another thought I had was to get a 1970’s Cadillac A/C blower motor. As I understand it all the GM A/C systems were identical to reduce costs of tooling up for each model they released. The difference then would be in the air flow presented by the blower. I figure perhaps a Cadillac blower will mate up perfectly, but have much better flow.
Ah...never mind. I just checked Autozone, and the Cadillac blower is the exact same as our vette blower...part # PM102.
But, another interesting thing is that the Cadillac fan (wire cage, whatever) which attaches to the motor is available for the cadillac part # 35530, but not for the vette. So, I'm not sure if the Cadillac fan is the same...should be though.
Last edited by Rockn-Roll; 08-13-2005 at 03:35 PM.
08-13-2005, 04:15 PM
#9
Race Director
Member Since: Sep 2002
Location: San Diego - Deep Within The State of CONFUSION!
Posts: 10,362
Likes: 0
Received 2 Likes
on
2 Posts
Originally Posted by rihwoods
"I insulated the cabin with Reflectix too."
Paul...think I have seen that at Dixieline...is it 5/16" thick ?
Paul...think I have seen that at Dixieline...is it 5/16" thick ?
08-13-2005, 05:36 PM
#10
Drifting
I don't know if this would make a difference. I used a 3/4" spacer w/c4 blower. There was a 50% or more increase. Would the 1/4" gap hurt airflow? I only have med/hi switch. My mech says the stk switcher are junk. He used upgraded GM switches when possible. JMHO
Rick
Rick
08-14-2005, 02:46 AM
#11
Melting Slicks
Thread Starter
Well, chevymans 77 , mine doesn't look as bad as that! It does have some leaves in it though, so I'm cleaning it out. I should have done it when I have the VIR/POA valve out. I'm having a tough fight trying to get in to get the leaves out. I'm gonna make sure I seal off the inlets in the wiper bay...the screens don't cover enough area...I'm going to go with household window screen material...will keep those pesky mosquitoes out as well as leaves.Anyway...I made it to Autozone and looked at four blower motors. One is the stock OEM replacement part #PM102. Also the C4 Vette replacement part #PM137. I also figured that a Van would have a better motor since it has a larger area to service, so I looked at the one for the 1995 Astro Van part # PM111. Just for good measure I looked at the 1995 Buick Park Avenue Ultra part #PM151.
Here's some pictures of them:
All:
PM102 Stock Replacement:
PM137 1995 Vette:
PM111 Astro Van:
PM151 1995 Buick Park Ave Ultra:
I inspected each unit carefully including inside through the cool air intake hole and they all have the exact same motor...5 windings over 10 cores with the same diameter wires with the same number of windings. The major difference is the orientation of the cool intake hole on the motor with respect to the mounting bracket. The PM111 1995 Astro Van unit is actually identical except that it includes a rubber seal for mounting the unit in the opposite direction of our units. Without the rubber seal the two units are identical.
So...I went with the PM102 which is a bolt-in replacement since it is just as powerful as any other OEM replacement. I've done some thinking about the larger fan, and believe that using the same housing with the larger fan (with the spacer) would not increase the flow significantly...some increase yes, but not much. I figure the best upgrade would be to get the housing that supports the larger fan...I have a suspicion that it may just bolt right in where our smaller housing goes.
08-14-2005, 03:17 AM
#12
Race Director
Member Since: Jun 2001
Location: The Only Corvette in Gila Bend, Az.
Posts: 16,483
Likes: 0
Received 1 Like
on
1 Post
St. Jude Donor '09
Originally Posted by Rockn-Roll
I know that my A/C system is doing it's job because my evaporator lines get frosted up...indicating that the air at the evaporator is as low as 32ºF....
They will then frost over a few degrees below that...
I helped 71airstrike put a C4 blower in his 71, and the increase in airflow from the vents was greatly improved over stock.
08-14-2005, 07:53 AM
#13
Team Owner
Originally Posted by Desertdawg
The evaporator lines will form moisture when they reach the dew point, it varies day to day...(watch your local news)...
They will then frost over a few degrees below that...
I helped 71airstrike put a C4 blower in his 71, and the increase in airflow from the vents was greatly improved over stock.
They will then frost over a few degrees below that...
I helped 71airstrike put a C4 blower in his 71, and the increase in airflow from the vents was greatly improved over stock.
GENE
08-14-2005, 08:41 AM
#14
i also did the blower upgrade,used a metal ''stove pipe cap'' for a spacer. i believe the reason we picked up some air flow was the new design of the squirell cage blades and the depth of the new cage, throws more air,,,scoops it better with the curved blades
08-14-2005, 10:00 AM
#15
Safety Car
Here's a retrofit air handler that I'm working up for my '77.
It has a pusher and a puller fan. The fans are the encapsulated SPAL evaporator fans.
This should provide plenty of air flow.
The diagram is looking down into the engine compartment. This section is the only part that needs to be changed.
It has a pusher and a puller fan. The fans are the encapsulated SPAL evaporator fans.
This should provide plenty of air flow.
The diagram is looking down into the engine compartment. This section is the only part that needs to be changed.
08-14-2005, 10:14 AM
#16
so where does this 2nd blower motor install? i have this setup in my house for a room in the addition that never got enough air/heat..its a duct/ booster fan that is energized when the fan is blowing in the furnace..the main blower is in the furnace,,and the 2nd is in the middle of the duct run serving the room which has the flow problem,,,,,,,,,,but where would this booster fan fit in a c-3???
Last edited by carl a; 08-14-2005 at 10:21 AM.
08-14-2005, 11:27 AM
#17
Safety Car
I'm still in the cardboard and sheet aluminum mock-up stage; it looks like it should fit above the PS valve cover.
Another thing I want to try is up'ing the power to fan motor to 19 volts by using this: TurboBooster voltage step-up module (#TB16V)
Another thing I want to try is up'ing the power to fan motor to 19 volts by using this: TurboBooster voltage step-up module (#TB16V)
08-14-2005, 05:05 PM
#18
Melting Slicks
Thread Starter
I also did a detailed comparison of the stock blades over the original and the pitch is exactly the same and with the same number of blades. The additional length of the blades won't be that effective since the air velocity coming out of the fan will be deflected by the spacer. There will be a slight increase in pressure, but due to the area restriction and accelerations of the air coming from the extra inch I doubt if the increase would be anything better than 5%. The extra load will also reduce the RPMs. Without actual measurements the determination of whether there is a significant increase in air flow is subjective.
08-14-2005, 11:29 PM
#19
Le Mans Master
C4 fan blades have more curvature to move more air. Late C3 fans have more curvature than early C3s but a bit less than C4s.
I installed a C4 fan with spacer and felt some increase but not a great deal.
Spinning any fan faster than its design will cause air to stall on the blade, create drag and tubulence (just like an airplane wing) and reduce airflow.
It's probably more important to completely seal the duct system (especially the dual ducts above the instruments) and to insure good electrical connections to the motor (especially ground). Poor electrical connections will cause low voltage resulting in low rpm operations and low air flow.
Also completely seal the firewall and the fresh air plenum (firewall to fender adhesive seal.
Insulating the engine side of the evap box helps also - especially if you have headers
I installed a C4 fan with spacer and felt some increase but not a great deal.
Spinning any fan faster than its design will cause air to stall on the blade, create drag and tubulence (just like an airplane wing) and reduce airflow.
It's probably more important to completely seal the duct system (especially the dual ducts above the instruments) and to insure good electrical connections to the motor (especially ground). Poor electrical connections will cause low voltage resulting in low rpm operations and low air flow.
Also completely seal the firewall and the fresh air plenum (firewall to fender adhesive seal.
Insulating the engine side of the evap box helps also - especially if you have headers
Last edited by flynhi; 08-15-2005 at 10:41 AM.
08-15-2005, 07:14 PM
#20
Melting Slicks
Thread Starter
flynhi...thanks for posting. Yes...the duct system needs to be clear, and electrical connections need to be good and solid without any resistance due to the connection itself. Very true about the sealing of the air box...I felt around the air box when I first got my vette and could feel cool air leaking around it. Some silicon and tightening of the screws did the job..
But...what you said about air stalling on the blade isn't accurate. Fans and airplane wings, any aerodynamic surface in fact, can accomodate any speed of air flowing over their surfaces. The only speed that is of concern is the speed of sound or better defined the speed at which pressure waves created by the front of the fan blades moves ahead of the blade and pushes air out of the way.
The speed of sound in air is approximately 761 miles/hour. The diameter of the fan is 5-1/2", so for every revolution of the fan each blade is moving at 5.5" x pi = 17.3". Even if the fan motor was turning at the Siemen's web site rating of 3,000 RPM then we would be seeing 17.3" x 3000 = 52,000 inches/minute which is equal to 49.1 miles/hour. As you can see we can increase the speed of our motors 10 times faster and still not have any problems with air pressure propogation not being able to keep up with the fan.
Also notice that at 49.1 miles/hour the fan isn't creating air velocity as fast as the air flowing into the air ducts from outside air at freeway speeds or better yet at the end of the quarter mile. I submit that anything we can do to speed up the fan is a good thing and worth trying.
I had the C4 fan blades and my original fan blades next to each other and they are identical...same pitch, width, etc.
I also wonder how much of the increase in air flow is simply due to wanting it to be increased? What we need is an actual air flow meter to detect the air speed out of the ducts.
But...what you said about air stalling on the blade isn't accurate. Fans and airplane wings, any aerodynamic surface in fact, can accomodate any speed of air flowing over their surfaces. The only speed that is of concern is the speed of sound or better defined the speed at which pressure waves created by the front of the fan blades moves ahead of the blade and pushes air out of the way.
The speed of sound in air is approximately 761 miles/hour. The diameter of the fan is 5-1/2", so for every revolution of the fan each blade is moving at 5.5" x pi = 17.3". Even if the fan motor was turning at the Siemen's web site rating of 3,000 RPM then we would be seeing 17.3" x 3000 = 52,000 inches/minute which is equal to 49.1 miles/hour. As you can see we can increase the speed of our motors 10 times faster and still not have any problems with air pressure propogation not being able to keep up with the fan.
Also notice that at 49.1 miles/hour the fan isn't creating air velocity as fast as the air flowing into the air ducts from outside air at freeway speeds or better yet at the end of the quarter mile. I submit that anything we can do to speed up the fan is a good thing and worth trying.
I had the C4 fan blades and my original fan blades next to each other and they are identical...same pitch, width, etc.
I also wonder how much of the increase in air flow is simply due to wanting it to be increased? What we need is an actual air flow meter to detect the air speed out of the ducts.