I have been reading over this book written by Mike Kojima, Honda/Acura Engine Performance, and he seems to be a preponent of underdrive pulley sets. He notes that pulley sets, such as AEM and UR, can see gains of 4-6 hp to the wheels. Also, in regards to worries about removing the crank pulley harmonic balancer, "Since Honda engines are internally balanced, the harmonic balancer is not as critical for engine longevity as an externally balanced American V-8 and we have not heard of any problems with UR pulleys even in long-term race use."

Now I know 4-6 hp gains seem very small, but most other bolt on modifications aren't making much more power than that in some cases, and the pulley sets are normally much cheaper than say an intake, header, or exhaust. As far as the danger of aftermarket crank pulleys, just how real is the possibility of damage occuring? I have read through Mr. Kojima's book occasionally and have read his articles in SCC, and over all it seems he is knowledgeable and very experienced in Honda tuning, so is he wrong on this one?

 

yeah i would like to hear ya'lls thoughts on the crank pulley too....i heard, well after i installed it that it could cause damage to your motor.....is this really true.....

bump for a good topic

 

Purely speculation and heresay, but:

I understnd this to be a detrimental mod for a motor, it basically unbalances the motors trueness, and will adversly affect furure reliability, IMO, not worth the small gains....

Ask this to mod B18C5-EH2, he has some g00d info...

 

The stock Honda crank pulley has rubber injected inside the pulley, the pulley is actually two peaces held together by rubber. This rubber absorbs vibrations and shocks that your alternator might make or the AC, if you don't have it your oil pump gear and the crank journal bearings closest to the oil pump will see increased load. It's not something that will kill your motor right away but it doesn’t help either. The only thing you have to ask yourself is, if the rubber inside isn't necessary why is it there? Honda could save milions by making the crank pulley a single solid metal peace but they didn't.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by piscorpio &raquo;</TD></TR><TR><TD CLASS="quote"> "Since Honda engines are internally balanced, the harmonic balancer is not as critical for engine longevity as an externally balanced American V-8 and we have not heard of any problems with UR pulleys even in long-term race use."

</TD></TR></TABLE>

Reading this quote from Mike Kojima, it does not seem like a big issue? It does say it is not as critical, which could suggest the possibility of damage, but overall the impression is that it is a very minor worry.

I have read b18c5-eh2's comments on pulleys in the past, I will try to search his posts specifically, as my original search did not net any useful results. Mostly, I just wanted to get a fresh discussion, because I had never really heard a solid argument supporting underdrive pulleys.

Another note, Mr. Kojima also claims that pulley sets like AEM's (which do not underdrive the crank) are "very good" as well and will produce nearly the same hp gains. So, crank pulley worries aside, are the 4-6 hp gains really so bad that they are not worth the 100-200 bucks (I think, haven't looked at prices lately)?

 

Underdriving crank pulleys got their start years back in NHRA drag. The stock 2 peice harmonic balancers that teams were still running, had been known to crack on occasion, splitting the outer portion of the harmonic balancer into multiple peices and scattering them everywhere, even into the stands. NHRA than sanctioned that 2 peice harmonic balancers were no longer allowed, and one peice pulleys took their place. All sorts of performance companies started making lightwieght, underdriving pulleys. The catcher: the teams started having to rebuild after every couple of races or so, rather than once or twice a season!

I'll try to find where i got this info from.

 

I've actually read that before, but again, you have to refer to the previous quote I sited. I get the impression that your source is dealing with the very same domestic v-8's that Kojima referred to. Let's make sure we are comparing apples to apples here.

 

Bottom line here is about why this seems to be a much maligned mod? I always hear how they suck, don't do anything, and further are possibly damaging. Is Kojima crazy when saying they net 4-6hp gains? (Ive also read in SCC, they net about the same on relatively mild cars ie:bolt-ons)

Or is it just that pulleys don't make a noticeable presence, like the sound of an exhaust or intake, that makes it seem less attractive?

Just fishing for discussion, I don't have the personal experience so I was hoping to get opinions from those who might.

 

One last go around.

 

Still seems to be questions here, anyone else care to contribute experiences? Anyone actually incur damages, or use them long term without damage?

 

I'd like to know too....

Nick

 

I got the UR underdrive pullies (all three) on my B18B and i love them... i wish i got them sooner. i have had <U></U> problems and noticed a real nice gain.

 

I have had NO problems*** sorry for the typo, i definetly recommend the pullies

 

The correct name for the crank pulley is a HARMONIC balancer. It does not have to do with balancing the reciprocating parts in the motor (pistons, rods, pins) that is done by the counterweights on the crank itself. It is to cancel out the harmonics caused by each crank throw being separated by the bore spacing. Each time a power stroke occurs it "hits" the crank which winds it up then it snaps back. All this is in really small amounts, thousanths of an inch. This happens along the length of the crank. A long crank like a Jag XK motor can self destruct at around 6k even with a balancer. A short crank like a Suburu can be OK without one, but still comes with one from the factory.

The Honda cranks are generally forged steel versus cast iron in many V-8's and the steel is much stronger. For street use on a mostly stock motor, the stock crank is strong enough that it is not likely to be a problem removing the balancer due to the crank being overbuilt. The closer you come to the limit of its strength, the better chance of damage. BTW, small block Chevy V-8's are internally balanced, except for the 400.

For the above reasons I choose to use the stock balancer. I have heard of racing balancers for V-8's that are lighter than stock and can take high revs that can make more power due to being more than the usual rubber band between steel parts. Maybe it's time for someone to make them for Hondas?

I have AEM pulleys on the p/s and alternator and found it made the engine rev quicker, but voltage at idle is low. If you spend a lot of time at low speed in traffic the battery may not get a good charge.

 

So if the engine is internally balanced, this is still not the same as harmonic balancing, I think I understood that correctly. But perhaps the fact that it is balanced internally, means there is less stress, or "hits", and thus harmonic balancing, while helpful, is not as vital to the engine? You also mention that the stock crank is overbuilt in a sense and can stand much abuse, wouldn't that also suggest that a harmonic damper is not crucial to the engine's survival?

I am just trying to understand this whole issue, since it comes up often and many people explain the harmonic balancing issue, but it comes off as theory. Very few people have had experiences with them, whether good or bad. The only reason I site Kojima's information, is because he seems to have an extensive background in Honda tuning and is basing his reasoning on his own experience. Clearly, from his own writing, he sees nothing wrong with replacing the stock crank pulley, but I wondered if he is the only one, or if it is based on applications that are vastly different than the average street engine?

 

For street use there is probably little harm in removing the balancer, but there is only a small gain in power and the engine will rev a little quicker. The benefit is not all that great. A lighter flywheel will make much more difference, but requires removing the transmission. The harder the engine is run, the greater chance damage could occur.

The basic problem is vibration in the crankshaft. It trys to twist slightly at each power stroke and the balancer damps out the vibrations before they can get too big. If the vibrations in the crank are the right frequency either it or things attached to it like bearings, rods, oil pump can be damaged or break. The balancer is like putting your finger on a tuning fork, it stops the vibrations.

Most materials have what is called a fatigue life. A set number of stress cycles can eventually break the part. The load from each cylinder firing and any undamped vibration add up. The balancer stops the vibrations and keeps them from building up higher. When a glass breaks from a note, that is a vibration (harmonic) at the critical frequency for that material. It is possible that the vibration in the crank could do the same. I doubt it could happen to a stock motor but it could reduce the lifespan of the bottom end.

I have heard of several motors with iron crankshafts that will break the crank if run at certain rpm's but are durable if kept below that level. Gm Iron Duke and Chrysler slant 6 are two. For myself the potential problems outweigh the benefits. I would be curious to hear what people with built motors choose to do. Sorry this ran so long, but I wanted to give the mechanics of what is happening. My paranoid engineer training says to stay conservative. The parts that could fail can take out the whole bottom end of the engine. As I said, not worth it to me.

 

Thanks for your input. I see what you mean, if there is even a chance of damage, why risk it for small gains?

I wasn't really analyzing the hp gain/cost/reliability factor, just trying to see if anyone has actually had an aftermarket crank pulley damage their Honda engine. So far, all I have heard/read, is old domestic V8's and iron cranks being damaged or destroyed, but that is about as different from a Honda 4 cyl. as you can get. I guess everyone likes to stay conservative as well?

 

Here are a few links you can read on the subject.

http://www.theoldone.com/archi...r.htm

http://www.supras.com/~riemer/....html

http://www.acura-cl.com/forums...ber=1

http://www.ntpog.org/reviews/u...shtml

 

i thought that (well i know the H-series engines atleast) have balance shafts that act as the harmonic balancer. but if they dont then what do they do? could be wrong but thats what i thought.

 

Thanks for the links.