Will an aluminum crank pulley damage my engine?

[Bman90]

Hello all. I hear mixed information that an undampened lightweight aluminum crank pulley will damage the engine by causing harmonic vibrations. The issue I see with this is that the piece of rubber on a factory pulley hardens over a short period of time and that defeats the purpose. I think the main issue is if an engine is externally a balanced with the pulley having a lightweight one can cause the crank to flex. So in theory it isn’t so much that vibrations will destroy the oil pump or bearings but crankshaft flex will. I have a 2.0t Accord if that helps. I also don’t see how vibrations are negated with a small piece of rubber. I’ve run solid motor mounts on one of my past cars with no issues - one mechanic even refused to install them saying it would destroy my engine. If solid motor mounts cause more vibrations then I don’t see how a lightweight undampened pulley will damage my engine. Should I install a lightweight crank pulley or is it safer keeping the stock one and not risking the small 5 horsepower gain. The aluminum pulley weighs only 0.8 lbs the stock pulley I recall is 5.5 lbs when dealing with rotational mass that’s huge. I did have an aluminum pulley on my first car back in high school a 1998 3000gt and I had no issues and it definitely made me spin the tires easier and improved throttle response. But that car only made 161 hp stock so any gain will likely be felt.

Thanks!

 

[Gladtojoin88]

I can't answer that but unless if it's over 60000 miles I'm sure warranty says it's a no no

 

[supton]

If you guess wrong, and take out some bearings, can you afford to repair them? in time and/or money that is.

 

[Skippy722]

Solid motor mounts won’t really hurt an engine, they just transfer more vibration to the vehicle. Harmonic dampeners help to take torsional vibrations out of the crank, whereas if the engine is externally balanced you will cause damage eventually. TL;DR is all harmonic balancers are dampeners, but not all dampeners are balancers.

Harmonic Damper: A Key Source for Lost Horsepower

How does the harmonic damper affect performance? Can you really gain horsepower through the use of the proper product? Find out more information inside.

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Taking It For A Spin: Why Are Some Cranks Externally Balanced?

Why are some engines internally balanced, and others are externally balanced? We talk with SCAT Crankshaft's Tom Lieb to find out.

www.enginelabs.com

 

[MacManus99]

I personally believe that the potential risks outweigh the benefits. I looked into one for my Scion FRS that saw track time, and my main intention for it was to increase how quick the engine revved to aid with heel/toe shifting. I ended up deciding against it for the above reasons.
I see some small benefit for lightweight pulleys on manual transmission vehicles, (acts like a slightly lighter flywheel) but see little benefit to them when used with an automatic transmission.
That is just my take on the part, it's your car, do what you want to in order to enjoy it.

 

[ctechbob]

I think it depends on the motor. I know when I was deep into the Miata thing it was advised against because the oil pump was driven off the very front of the crank and not having a pulley with a damper in it would cause the oil pump gears to shatter over time. So sometimes there's more to it than just the crank bearings.

Not entirely familiar with your Accord, but a lot of times Honda runs the oil pumps off the front of the crank, not sure if they would suffer the same fate.

 

[JimPghPA]

That rubber drying out takes a very long time, like 10 to 15 years.

If it was not needed the original designers would not have put it there. They are always trying to save every penny they can on how they build things. So, if it is part of the original design, it is there for a reason. Don't try to ger by without it.

 

[ctechbob]

That rubber drying out takes a very long time, like 10 to 15 years.

If it was not needed the original designers would not have put it there. They are always trying to save every penny they can on how they build things. So, if it is part of the original design, it is there for a reason. Don't try to ger by without it.

Well, there's 'needed' and 'we put it there for XYZ (Usually NVH) reasons'. Lots of things in cars could be chunked by the wayside if you're willing to put up with some measure of discomfort. Others can't be removed without causing damage. It all depends on what the end goal is.

 

[JimPghPA]

It never ceases to amaze me how time after time people who do not have decades of working on vehicles think that they can simply modify something to increase performance, and in the end what happens is they have sabotaged reliability. I have seen in again and again, nothing new here.

 

[Trav]

If it has a rubber ring then it is most likely externally balanced using a damper and I would not take a chance with a lightweight pulley in place of the damper. On an engine that uses just a pulley then sure it would not be a issue. The damper is heavy for a reason.

 

[Cujet]

In a past life, I worked with a major manufacturer developing a camshaft profile for high performance turbocharged engines. The bottom line is that some form of harmonic damper really is required on many engines. The rubber is not really as critical as one might think, and does not do the damping. It is just a connection to the weight. In other words, dampers can be made with fluid or even bushings. As long as the rubber still attaches the outer weight to the hub, it will likely work just fine. Many dampers live 50 years without difficulty.

I can't say whether your engine will suffer by damper removal. You might want to look into any enthusiast group (forums) that operate the engine in question. Crank driven oil pumps can suffer without a damper. As the additional vibrations can "tax" the gears in the pump. It is true that many engines can live a long full life with the damper removed. It's also true that some engines suffer premature failures. One thing is certain, you really are not "freeing up" any HP unless the pulley size is changed. Even then, it's possible that the crank or cam position sensor will now reflect the additional torsional movement and reduce HP through lower accuracy.

Example of a gerotor oil pump failure. Whether this one was due to excess RPM (outside of the dampers limits) or lack of damper, I don't know. But in the end, improper crankshaft damping caused the failure. The cast iron "gears" are brittle, and 8000+ RPM results in a lot of back and forth acceleration on the unloaded end of the crankshaft, as it also rotates at 8000.

Not all engines have a crank end gerotor pump, and therefore not all engines have this risk.

 

[RooflessVW]

On a turbocharged motor one of the last items I would look at to increase power would be the pullies.

This isn't an N/A B16.

 

[TeamZero]

It *probably* wont hurt anything in the engine.....but may reduce life in the trans/clutch if its a stick. I was part of a team that very successfully ran a n/a 2.4 in a neon in ChumpCar for years. Along the way we ditched the heavy harmonic balancer for a smaller aluminum one. While it made a slight difference in rev feel/action, and slowed down alt speed, which also gave us a small gain, there WAS as issue. We kept cracking clutch pressure plates/discs. We tried all different $$$$ aftermarket ones, but they would usually only last about 30hrs or so, so 2 race weekends, but some clutches, less than that......this is endurance racing with usually two 7 hr races on a weekend. Now keep in mind this is a modded 2.4 with balance shafts removed, that runs WOT 4000-6500 for 7 hrs at a time. Finally we swapped to a Fluidampr and never broke a clutch again. When we first swapped to alum. pulley, and started having issues, I soon realized it was harmonics causing the issue, but we tried to work through it trying different clutches. As I was the engine builder, it was also in my back of mind we might also end up with crank breaking issues, as they use a cast crank. This never happened and we ran with that pulley for prob close to 2 years? so.....the gain will be small, and prob. not worth it unless you are looking for every less hp in a racing application .

 

[partspro]

If you guess wrong, and take out some bearings, can you afford to repair them? in time and/or money that is.

I believe others are correct, you must maintain Correct ‘Balance’. IIRC, when I converted the 69 Mustang from Auto to Stickshift, Finding a correctly Balanced Flywheel and Ringgear was difficult and Expensive

 

[partspro]

Sure, this is simpler, but I had a Harmonic Balancer Walkoff a crank shaft on a previous 351 Windsor build that I put in a Ford Fairmont , I would contact the Manufacturer with your specific engine, year etc

 

[Deleted member 89374]

Considering how much auto manufacturers want to squeeze every drop of fuel economy that they possibly can out of each powertrain, if there was even a slight benefit to installing a lightweight crank pulley to oh-so-slightly increase horsepower and decrease fuel consumption, they would have done it from the factory. Since the risks outweigh the benefits, none of them is doing it. So, don't do it if you'd like to avoid engine problems.

 

[Bman90]

Considering how much auto manufacturers want to squeeze every drop of fuel economy that they possibly can out of each powertrain, if there was even a slight benefit to installing a lightweight crank pulley to oh-so-slightly increase horsepower and decrease fuel consumption, they would have done it from the factory. Since the risks outweigh the benefits, none of them is doing it. So, don't do it if you'd like to avoid engine problems.

I don’t believe in the they would of of done it from the factory if it was better. Cast iron pullies are cheaper than aluminum ones. Plus the rubber eventually can come apart causing the pulley to come apart. Everything is about money a solid pulley wouldn’t have to be replaced ever. There’s also people reporting that solid pullies cause them to feel vibrations from ac turning on and off. It’s all about comfort. Stock rubber mounts go bad over time but solid mounts aren’t good for most people because of the vibrations.

 

[Bman90]

On a turbocharged motor one of the last items I would look at to increase power would be the pullies.

This isn't an N/A B16.

I think you’re right. If anything depending on how many mods I get into I may look into lightweight wheels and lightweight cam gears to decrease rotational mass. But there’s better proven mods. Thanks.

 

[Bman90]

It never ceases to amaze me how time after time people who do not have decades of working on vehicles think that they can simply modify something to increase performance, and in the end what happens is they have sabotaged reliability. I have seen in again and again, nothing new here.

I used an aluminum pulley on my 3000gt for over 10 years with no issues. But that car even with all my mods and bolt mans was maybe making 200 horsepower only. I guess with more power the margin for error gets less.