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Underdrive Pulley Questions

  #1  
Old 03-23-2014, 10:56 AM
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Question Underdrive Pulley Questions

I'm looking into underdrive power steering and alternator pulleys but am a bit confused at what I'm finding. I see that some are specific for 5th gen accords, some are for 4th to 6th gen accords and some are universal for all acura and honda.

The universal ones are a bit cheaper but I'm unsure as to what to look for.

Anyone put underdrive pulleys in? I see that not much difference in electrical, steering or AC has been noticed and most say its worth it for the performance gain.

Thanks, in advance, for your help guys
 
  #2  
Old 03-24-2014, 06:00 PM
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I'm sure you have read and researched this.

https://www.hondaaccordforum.com/for...pulleys-35041/
 
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Old 03-24-2014, 06:35 PM
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I didn't find this in my searches. Thanks.

....
So it makes sense that replacing the balancer with a light weight one is potential damaging to the engine. I don't think I'd go that route. But i've seen different options.

There are the lightweight crank pulleys available for both reduced diameter and weight but what I also see are overdrive pulleys right at the alternator, power steering and AC. Those I wonder about the compatibility- could a different size pulley be used as long as the belt rib count is right. And I wonder what people might have used.
 

Last edited by RobinsonRicer; 03-24-2014 at 06:50 PM.
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Old 03-25-2014, 10:53 AM
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Seems like the "danger" of underdrive pulleys is NOT the simple matter of driving the accessory at a slower RPM.

You can under-drive the accessories by 2 means. Larger diameter pulley on the accessory, or smaller pulley at the crankshaft.

The problem is that what you find is a smaller-diameter pulley at the crankshaft, which is OK. But it also does not have that rubber isolating layer between the pulley & hub, and doesn't have the right weight for higher-order vibrations. That's what can cause problems.
 
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Old 03-25-2014, 01:23 PM
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I did see that issue, which basically causes the deterioration of several components at certain resonances.

But would replacing the alternator or power steering pulley with a larger diameter pulley be of benefit? The alternators are design to output more than enough amps for the system.
 
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Old 03-25-2014, 02:04 PM
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Originally Posted by RobinsonRicer View Post
I did see that issue, which basically causes the deterioration of several components at certain resonances.

But would replacing the alternator or power steering pulley with a larger diameter pulley be of benefit? The alternators are design to output more than enough amps for the system.
Yes and no.

True, alternators at full boil are capable of generating more power (which is on demand by the way) than the car can draw, however, at idle the demands of the car are typically at or near what many alternators can generate. Adding a larger pulley (or a smaller crank pulley) will slow the alternator down to the point where, at idle, it will most likely not be able to keep up with the demands of the car.

As for the benefits of changing the relative speeds of the rotating accessories; unless you're racing and needing to shave hundredths of second off of a lap time, slowing down the accessories is pretty much worthless.
 
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Old 03-25-2014, 08:21 PM
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Hi Shipo! ;D

I've read up more and seen that the idle is the problem with underdrive alternator pulleys, that can be resolved by slightly raising the idle. But also I read that alternator pulleys can be increased to 10% without adverse issues. The other pulleys can be increased by up to 25%.

Whats interesting is that this application is mostly seen on v6 and v8s and with rather significant results. But it has been done on 4 cylinders with benefits.

I'm also looking for MPG increase as well as a little extra throttle response.

Why is this more common on v6 and v8s?
 
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Old 03-25-2014, 09:26 PM
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That's a little curious, because "typically" a 4cyl would be a higher-revving engine. So that hi-revving engine is the one that would benefit a bit more from underdriven accessories.

I think Honda flirted with this on the 95 Integra GSR that I had. With an 8,000 redline, there was a large difference between idle & "fun". At idle the headlights dimmed a bit, so I figured the alternator was just barely keeping up when the engine was spinning 700 rpm. I never thought that was a bad thing, because I don't sit with the engine idling.

For an engine with a 600 rpm redline, the alternator only has to operate over an 8:1 range of speeds.
 
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Old 03-26-2014, 10:03 AM
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I see. Then again the factory electrical systems leave more to be desired. I feel the impact of an overdrive pulley would not be as significant on a car with a good electrical system. A grounding kit made my car come to life.

There are the headlight bulbs that use less watts since thats really the most common electrical draw.

I may try this out just for kicks if I can get it cheap enough. Question is if I can find pulleys that will fit my car but are slightly larger in diameter. Do all 90s hondas use the same size alternator and power steering pulleys?
 
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