twilightprotege
Member
- :
- 2001 323 Astina SP20 (P5)
definately no ass dyno gains (hell hardly anything shows gains there), but i'm certain it is worth it. rev your engine right up and i'm certain i'll rev a heap quicker
Underdrive Pulleys : The Definitive Discussion
- Thread starter twilightprotege
- Start date
Install was easy as all hell... I'd rate it as just barely more difficult than an intake install. Far easier than a header install, and much quicker than a thermal spacer install... sooo 
The alternator comments were incorrect. It certainly will cause a greater load. Energy isn't free!! You'd have to figure out the charge rate, average charge current, then convert it into watts, so say you go from a 70 amp alternator (I don't know what our current one is) and then go to 100 amp alternator, you will increase by 360 watts. 360 watts is roughly a half horse. So every 30 amps would be roughly a half horse of losses. Debatable as to whether or not that is negligible.
The alternator comments were incorrect. It certainly will cause a greater load. Energy isn't free!! You'd have to figure out the charge rate, average charge current, then convert it into watts, so say you go from a 70 amp alternator (I don't know what our current one is) and then go to 100 amp alternator, you will increase by 360 watts. 360 watts is roughly a half horse. So every 30 amps would be roughly a half horse of losses. Debatable as to whether or not that is negligible.
Also we didn't get to weigh the pulleys against one another, but I'll tell you that if I had to guess I'd guess the stock pulley was around 8 lbs, and the replacement was around 1-2 lbs. So that is a drop of a good 6 lbs...which is more of a drop than the MSP flywheel relative to the stock protege flywheels.
Installshield 2
Gothenburg Superiority
just to touch on it quickly...this has been discussed a bit in the past in different threads...
the "bad for the engine" notion is due to harmonic resonance, which in turn relates directly to crank oscillation in a number of ways...a simple way to think of it is that you figure a crank shaft is a well balanced and heavy hunk of metal, and then we have these crazy things sticking off of it that push the crank in different places at different times...simply, a spinning crank, that is being spun by rods and pistons, is difficult to keep perfectly balanced...
But with that said, modern engines have much better crank balance and overall assembly balance than Detroit's days of yore...I swear to everyone, that on most modern small displacement engines, the reason a stock "harmonic damper" is so heavy, is actually closely related to your idle quality, than actually absorbing any vibration...
Anyway...Harmonica resonance within a rotating assembly is directly correlated with volumetric efficiency and rpm...more so with volumetric efficiency...because the engineers that designed the engine are much better at balancing an engine for rpm, rather than load...so weakest part of a current engines design is usually oscillation at times of high volumetric efficiency...or high load basically...so you can see where this is going...NA engines, especially small NA engines, rarely have much of a problem with "load vibes", simply because the parts are much stronger than the vibrations caused by what little air they can pull in in the first place...so they have very little stress on the entire assembly, even at its peak volumetric efficiency...
the point of a damper or balancer is to help prevent oscillation within the crank...both the flywheel and the crank pulley do this marginally, by using mass points and overall weight within the balancer to help absorb vibrations that could theoretically travel back and fourth along the crank and crank cradle...But its overkill on a small engine such as the FS...we don't make enough V.E. to overwhelm the stock crank, which is forged to begin with...I am almost ready to test this just to prove a point...It is my bet that the difference in crank vibration from a stock piece to a lighter UDP and lighter flywheel will be so marginal it will barely make a difference...as long as the peak volumetric efficiency isn't raised significantly (like turning 130lb/ft of torque into 200...won't happen if you do it our way)...
Also some question the integrity of the oil pump, and oscillation will potentially cause problems with that...But...again, the difference in oscillation is so small in a well balanced assembly that it won't make a difference...
If you are worried at least check out other boards, such as VW, Honda/Acura, Toyota, BMW, etc...they all use these...and most of which have crank driven oil pumps...on heavy modded NA apps, even with UDP's and flywheels, you barely ever hear of critical oil pump or overall engine failure...but...you probably will come across a few with turbo's and UDP's that popped...
and that is what the above was relating to...Turbo's make torque...by raising V.E. by a lot (more so than 100%)...this creates all kinds of extremely wierd and hard to cure vibrations within the crank...You will notice that the strongest turbo'd engines, are actually somewhat crudely designed...especially for efficiency...the money goes into extremely beefy parts, and if they are strong enough...they hold...and one reason for this is because of the how it is extremely expensive to cure load vibrations...there are ways of doing it for the most part, but its simply cheaper to use stronger, more expensive parts...and crank pulleys, at least heavy ones, really help this...so on Turbo cars, I would never recommend a UDP...but this is entirely different to NA engines...
this is getting way long, but one more thing...One thing that doesn't get mentioned much is the true reason for heavy s*** hanging off the end of a crank...idle...everyone buying a new car for some reason wants the thing to idle so quiet and perfect that you don't even know the engine is running...I hate that...heavy flywhees and pulleys create smooth idles by allowing the engine not to slow down nearly as much between each pistons ignition...which helps, because at 800 rpm the engine is struggling more than you think to actually keep running...with lighter end parts, the engine is more rough because it is actually slowing down considerably, even in the fractions of a second, between each piston ignition...which makes it feel and sound rougher...a rough idle is the only thing a NA owner should be concerned about as far as UDP's...and if the oil pump s*** scares you, convert to dry sump...its cooler anyway...
the "bad for the engine" notion is due to harmonic resonance, which in turn relates directly to crank oscillation in a number of ways...a simple way to think of it is that you figure a crank shaft is a well balanced and heavy hunk of metal, and then we have these crazy things sticking off of it that push the crank in different places at different times...simply, a spinning crank, that is being spun by rods and pistons, is difficult to keep perfectly balanced...
But with that said, modern engines have much better crank balance and overall assembly balance than Detroit's days of yore...I swear to everyone, that on most modern small displacement engines, the reason a stock "harmonic damper" is so heavy, is actually closely related to your idle quality, than actually absorbing any vibration...
Anyway...Harmonica resonance within a rotating assembly is directly correlated with volumetric efficiency and rpm...more so with volumetric efficiency...because the engineers that designed the engine are much better at balancing an engine for rpm, rather than load...so weakest part of a current engines design is usually oscillation at times of high volumetric efficiency...or high load basically...so you can see where this is going...NA engines, especially small NA engines, rarely have much of a problem with "load vibes", simply because the parts are much stronger than the vibrations caused by what little air they can pull in in the first place...so they have very little stress on the entire assembly, even at its peak volumetric efficiency...
the point of a damper or balancer is to help prevent oscillation within the crank...both the flywheel and the crank pulley do this marginally, by using mass points and overall weight within the balancer to help absorb vibrations that could theoretically travel back and fourth along the crank and crank cradle...But its overkill on a small engine such as the FS...we don't make enough V.E. to overwhelm the stock crank, which is forged to begin with...I am almost ready to test this just to prove a point...It is my bet that the difference in crank vibration from a stock piece to a lighter UDP and lighter flywheel will be so marginal it will barely make a difference...as long as the peak volumetric efficiency isn't raised significantly (like turning 130lb/ft of torque into 200...won't happen if you do it our way)...
Also some question the integrity of the oil pump, and oscillation will potentially cause problems with that...But...again, the difference in oscillation is so small in a well balanced assembly that it won't make a difference...
If you are worried at least check out other boards, such as VW, Honda/Acura, Toyota, BMW, etc...they all use these...and most of which have crank driven oil pumps...on heavy modded NA apps, even with UDP's and flywheels, you barely ever hear of critical oil pump or overall engine failure...but...you probably will come across a few with turbo's and UDP's that popped...
and that is what the above was relating to...Turbo's make torque...by raising V.E. by a lot (more so than 100%)...this creates all kinds of extremely wierd and hard to cure vibrations within the crank...You will notice that the strongest turbo'd engines, are actually somewhat crudely designed...especially for efficiency...the money goes into extremely beefy parts, and if they are strong enough...they hold...and one reason for this is because of the how it is extremely expensive to cure load vibrations...there are ways of doing it for the most part, but its simply cheaper to use stronger, more expensive parts...and crank pulleys, at least heavy ones, really help this...so on Turbo cars, I would never recommend a UDP...but this is entirely different to NA engines...
this is getting way long, but one more thing...One thing that doesn't get mentioned much is the true reason for heavy s*** hanging off the end of a crank...idle...everyone buying a new car for some reason wants the thing to idle so quiet and perfect that you don't even know the engine is running...I hate that...heavy flywhees and pulleys create smooth idles by allowing the engine not to slow down nearly as much between each pistons ignition...which helps, because at 800 rpm the engine is struggling more than you think to actually keep running...with lighter end parts, the engine is more rough because it is actually slowing down considerably, even in the fractions of a second, between each piston ignition...which makes it feel and sound rougher...a rough idle is the only thing a NA owner should be concerned about as far as UDP's...and if the oil pump s*** scares you, convert to dry sump...its cooler anyway...
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Any sources or ideas on dry sump? I'm definitely thinking about doing it this summer... If I can afford it.
Thanks for the great info as always Installshield... one other question for you though as well... in theory lightening the flywheel which is ALSO bolted to the crank is similar in it's effect... likely even moreso than the UDP. With a motor like mine that will be excessivly boosted the logic of above would be to remain with a heavier flywheel to ease some of that vibration overall. I'm asking/agreeing with you on that concept. I'm spending a fair amount of money to have my internals and crank carefully balanced to less than half a gram to further ensure minimal vibrations.
Thanks!
steve
Thanks for the great info as always Installshield... one other question for you though as well... in theory lightening the flywheel which is ALSO bolted to the crank is similar in it's effect... likely even moreso than the UDP. With a motor like mine that will be excessivly boosted the logic of above would be to remain with a heavier flywheel to ease some of that vibration overall. I'm asking/agreeing with you on that concept. I'm spending a fair amount of money to have my internals and crank carefully balanced to less than half a gram to further ensure minimal vibrations.
Thanks!
steve
Installshield 2
Gothenburg Superiority
yeah sort of...I never understood that part really...the first thing engine builders make sure of being correct is the trueness of the crank...meaning it is perfectly straigh from end to end through its middle section...this prevents vibration, obviously, from occuring at one end of the crank...which will literally in a matter of minutes destroy that ends journals, load points, and possibly everything...
So with that said, theoretically any vibrations occuring at end, say from the gear box and clutch/flywheel would most likely make it all the way to the oil pump too...somewhat, or get "damped" half way possibly...actually I don't know...but yeah turbo gurus have long said that UDP's are the one to look out for, but not so much for just a lighter flywheel...but NEVER both light flywheel and light UDP...instant grenade...
but you could compensate for the vibration by crank balancing, especially if you have experience with load balancing...which is hard as s***...I tried it, it sucks...depending on the equipment avaliable you have to simulate loads through calculus on certain points of the crank...and you have to do it with enough standard deviation to allow for changing engine conditions, such as a cold or hot day...and from there a computer helps you pin point pressure zones of which the crank may have a problem with load induced vibration...and it also deals with the rods/pistons themselves...I had to go through 3 sets of wrist pins because I kept getting an error saying they would cause extreme vibration on each thrust bear for that part of the crank...but if you can do it, I salute you...it will definately pay off, and destroy any need for a heavy damper...
So with that said, theoretically any vibrations occuring at end, say from the gear box and clutch/flywheel would most likely make it all the way to the oil pump too...somewhat, or get "damped" half way possibly...actually I don't know...but yeah turbo gurus have long said that UDP's are the one to look out for, but not so much for just a lighter flywheel...but NEVER both light flywheel and light UDP...instant grenade...
but you could compensate for the vibration by crank balancing, especially if you have experience with load balancing...which is hard as s***...I tried it, it sucks...depending on the equipment avaliable you have to simulate loads through calculus on certain points of the crank...and you have to do it with enough standard deviation to allow for changing engine conditions, such as a cold or hot day...and from there a computer helps you pin point pressure zones of which the crank may have a problem with load induced vibration...and it also deals with the rods/pistons themselves...I had to go through 3 sets of wrist pins because I kept getting an error saying they would cause extreme vibration on each thrust bear for that part of the crank...but if you can do it, I salute you...it will definately pay off, and destroy any need for a heavy damper...
Pants McGregor
Member
- :
- '05 Legacy GT wagon
So, with my AWR motor mounts I get a lot of vibration when the car is at low RPM idle. I have not yet installed my UDP, but would the expectation be that it will idle lower and cause even more vibration ?
Installshield 2
Gothenburg Superiority
not really...I should have clarified a little...the crank pulley has weight to prevent accessery drain whenever the AC kicks on or the alternator loads up...a lighter unit, or an underdriven unit will have a considerable dip in rpm whenever these things kick on...but then the ECU will be able to bring it back up to the normal idle rpm...you just notice it a little thats all, when before you only hear a sound...
but the vibration you actually feel inside the car is not the actual oscillation occuring within the crank...a poly engine mount that makes the car feel like it vibrates more has no side affects whatsoever on the engine itself (the AWR mount transmits vibrations that were already there into the cabin, while the stock rubber mounts stop the vibrations almost completely...either way, the engine still vibrates)...but these vibrations are for a whole number of reasons, not just an underdamped crank (i.e. road vibrations, gearbox variables such as diff "noise", CV joint binding, etc...)
anyway...with a UDP the engine will not idle at a lower rpm...it will idle just a bit rougher than before, but at the same rpm...the big idle killer is the AWR rear mount...I have sat in proteges with a lightwieght flywheel and a UDP, but with the stock mount...and it wasn't half as bad as my car with just the rear mount (and stock udp and flywheel)...and my guess is that if you already have that mount, a UDP will not even be noticable...
but the vibration you actually feel inside the car is not the actual oscillation occuring within the crank...a poly engine mount that makes the car feel like it vibrates more has no side affects whatsoever on the engine itself (the AWR mount transmits vibrations that were already there into the cabin, while the stock rubber mounts stop the vibrations almost completely...either way, the engine still vibrates)...but these vibrations are for a whole number of reasons, not just an underdamped crank (i.e. road vibrations, gearbox variables such as diff "noise", CV joint binding, etc...)
anyway...with a UDP the engine will not idle at a lower rpm...it will idle just a bit rougher than before, but at the same rpm...the big idle killer is the AWR rear mount...I have sat in proteges with a lightwieght flywheel and a UDP, but with the stock mount...and it wasn't half as bad as my car with just the rear mount (and stock udp and flywheel)...and my guess is that if you already have that mount, a UDP will not even be noticable...
- :
- MP5T / 944
Great info...insall. I learned alot.
But the original question was...
Is it worth it..
Response... UDP NOT worth $$$
But the original question was...
Is it worth it..
Response... UDP NOT worth $$$
Already discussed this with the fOCUS community when I had a fOCUS. The lowere pulley on these 4cyls is not a true damper. the little bit of rubber you see it for acccessory NVH reduction. These engines are usually internally balanced dure to the harmonics of a 4cyl engine.
I did the research, and this is true in at least 90% of the cases. The lower pulley on the Protege 2.0 is not a true damper (at least for the engine itself).
I did the research, and this is true in at least 90% of the cases. The lower pulley on the Protege 2.0 is not a true damper (at least for the engine itself).
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- MP5T / 944
Agreed, It can't be, it's solid. It's just more rotational mass to even out the feel of the car so that grannys can drive the P5 Happy to get their MEDS..
Pants McGregor said:
I only get more vibration with ALL of my accessories on (and even then it is just a very slight bit more). This seems to only be a problem with the 4cyl engines and is caused by the extra drain on the altenator pulling harder on the engine, not something else.
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- MP5T / 944
The AWR do rattle a bit, but it's woth it. I love to hear the tranny whine through the floor of the car. I love to feel the car shake on start up. It's my little race car. It was never meant to be smooth. Violent and fast! I love the reaction I get when I take Peeps for a spin.
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- MP5T / 944
That is nuts but cool...
twilightprotege
Member
- :
- 2001 323 Astina SP20 (P5)
Installshield 2 said:
when do you ever touch on things quickly??? LMAO!!!
Installshield 2
Gothenburg Superiority
fair point...let it be said that I meant to touch on it quickly, but lost that battle...
But again I want to note that any vibration you feel inside the car is not the oscillation that a lot of people worry about...crank oscillation occurs at such a high frequency (when it is bad) that the human ear would not be able to detect it, or be able to feel it for that matter...So don't think because a UDP equipped car shakes more at idle that your engine is going to fly apart...thats a totally different form of vibration, that is not bad at all...just annoying to some...
But again I want to note that any vibration you feel inside the car is not the oscillation that a lot of people worry about...crank oscillation occurs at such a high frequency (when it is bad) that the human ear would not be able to detect it, or be able to feel it for that matter...So don't think because a UDP equipped car shakes more at idle that your engine is going to fly apart...thats a totally different form of vibration, that is not bad at all...just annoying to some...
Installshield 2
Gothenburg Superiority
Brian MP5T said:Agreed, It can't be, it's solid. It's just more rotational mass to even out the feel of the car so that grannys can drive the P5 Happy to get their MEDS..
You kind of faked yourself out...That is one way a car's harmonic balancer works...the rotational inertia created by the mass of the spinning flywheel and drive pulley helps dampen the oscillation created by a crank that is spun by parts that start and stop...
So basically the more mass, the more balancing done to the spinning crank...and also the smoother the operation...albeit can sap lots of power and efficiency...
But like mentioned before, the internal balancing of the crank and assembly make the balancing affects of a heavy drive pulley somewhat overkill...but the heavy pulley still helps with idle quality and driving of the AC etc...
But Flywheels are sometimes referred to as harmonic balancers also...and they are solid...But you are correct in that the term Detroit uses for a harmonic balancer has all kinds of cavities and wierd spots...and ours does not...its more a difference in definitions within the automotive community...but as far as physics is concerned, it has little to do with the part itself, just what it does to oscillation...(Gets rid of it)
twilightprotege
Member
- :
- 2001 323 Astina SP20 (P5)
not that we mind long replies, you always give great info
Keep in mind that any solid body that is rotated will have a natural frequency. any adjustment in the mass or apparent load will alter that natural frequency. Sound design requires calculating those ranges of loads and determining the necessary mass values of the rotational inertia of the system to ensure that the given rotation will not hit a harmonic frequency.
For more information see: Tacoma Narrows Bridge (same concept in some ways, just not rotational based)
Install... I have a real hard time believing that the UDP is any different as far as frequencies than the flywheel. they are both DIRECTLY bolted to that crankshaft. They both are part of the crank for all intents and purposes. The one thing that I can think of though is the flywheel mass is spread out more.. but at the same time you would think greater reductions in that would make greater issues for the harmonics.
I think this is much like cryo.. lot of anecdotal statements and beliefs, but not a lot of actual evidence.
For more information see: Tacoma Narrows Bridge (same concept in some ways, just not rotational based)
Install... I have a real hard time believing that the UDP is any different as far as frequencies than the flywheel. they are both DIRECTLY bolted to that crankshaft. They both are part of the crank for all intents and purposes. The one thing that I can think of though is the flywheel mass is spread out more.. but at the same time you would think greater reductions in that would make greater issues for the harmonics.
I think this is much like cryo.. lot of anecdotal statements and beliefs, but not a lot of actual evidence.
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