Ok you upgraded lower blower pulley owners, what does blower cavatation sound like at idle?

I just got a JL 5# and I was curious.

 

I dont think you will hear it at idle... only in the higher RPMS, and by then it is to late... 5Lbs....

 

I presume you are talking about the phenomenon happening at sudden pressure reduction in liquids. I do not know if it can happen in our blowers...

http://cavity.ce.utexas.edu/

 

There is also something called pre-ignition or pinging...

This a is a condition that occurs when combustion starts spontaneously from a hot spot in the cylinder or on the piston, and then that flame front collides with the one propagating from the spark plug (in fact, this is why it's known as pre-ignition - it's the fuel igniting before it's "supposed to" when lit by the plug). The collision of flame fronts is what causes the characteristic "ping" sound. The higher the compression, the greater the likelyhood that combustion will start "accidentally" in this manner. Diesel engines actually function on this principal (...and that's why they sound like someone shaking a can of bolts, because fuel ignites in various parts of the chamber at once) - they have compression ratios upwards of 25:1, and squeeze the fuel under such pressure that it ignites without needing a spark plug.

http://www.hastingsinc.com/Service%2...reignition.htm

http://www.exxon.com/exxon_productda...dia/knock.html

 

No, I am refering to any difference in engine sounds at idle after installing the lower blower pulley, kind of like a little rumble at 700-800 rpms, which others refered to cavatation.

 

If you hear a rattle coming from the engine when idling in gear but no rattle when in P or N then you have whats known at cavitation. Caused by the blower pushing more air at idle than the engine can accept. Usually as a result of adding lower pulley. Your tuner should be able to adjust your chip open the idle bypass to help lower the volume of the rattle.

Rattle is viewed by some as a good thing cause it means your Blower is tight ... We all like a tight blow right ??

Doug

 

You're on it... Almost sounds like a rattle. Thanks, now I feel a bit better.

 

MOP,

It's obvious these guys don't know what you're talking about but I do. It sounds like your bearings are grinding in the blower. It's not as noticable out of gear but it gets louder when put in gear and the idle drops with a load on it. Even if you didn't have it before you're probably going to hear it with a 5# pulley.

I had it a little with the stock pulley and it got louder with a 2# pulley. I put a 4# pulley on and it got louder. I had my chip programmed to tone it down after I put the 2# on but it doesn't get rid of it. I didn't realize how much it was toned down (even though I could still hear it) until I pulled the chip. I had never heard the 4# without the chip and it was loud.

Fast1matt's was quiet with a 2# pulley when we were comparing them. When he put a 4# on it started making noise.

Doug you beat me to it.

 

Cavatation isn't the correct term for whatever is happening.


cav.i.ta.tion \ kav' i ta' shun \ n [1. the rapid formation and collapse of vapor pockets in a flowing liquid in regions of very low pressure. 2. such a pocket formed.]



It only happens with liquids, not air. Cavatation will kill a pump very quickly.

Is it possible you didn't get the pulley on square or damaged your balancer. The engine will make nasty noises and run really "rough" if something happens to the balancer or crank pulley. Even an imbalance in the crank pulley itself would be noticable. If it's bad enough it would be noticable even at idle.

 

Guys, please, stop with the cavitation thing. You're killing me here already. That whole cavitation thing is BS.

The noise heard when putting on a lower pulley (usually described as a rattle, growl, or bearing sound) is normal. That is the sound that the rotor gears make when they are not under load. As they spin at a low rpm, the make a "clattering" noise. Take one of your hands and cup it into the shape of a "C". Now take your other hand, stick it out straight, and insert it into the "C". Now hold the "C" still and move your other hand from the top to the bottom of the "C". That simulates what the rotor gears do at low rpms. The truck actually do this stock. But the stock lower pulley is designed to absorb that noise, which is why the stock pulley has a giant hunk of rubber for the middle. Going to an aftermarket soild pulley, often makes the rattling sound much louder. And when you give the truck some rpms, the gears are forced to one side, and the noise goes away. Ever hear a centrifugal blower at idle? Same noise, same reason.

 

Gear lash!

 

You can call it what you want but it can be toned down and that's a fact. I had it done with a 2# pulley and after running a 4# pulley I pulled the chip and it got twice as loud. Sal you're right about one thing and that's the fact that you had better get use to it because it going to be there whether it's louder or not.

 

Well look guys I took the snout off of my blower and smeared Jiffy peanut butter all over the gears and the noise went away. I will now go smear some peanut butter on myself and be happy. Thanks.

 

Crunchy or regular? Peter Pan is the best.

 

Guys Lighten up....

Cavitation is just a word... It was used to describe a problem.... We dont always use words in thier literal meaning, sometimes they are used to convey a concept that dosnt have a good description.... I guess we could have launched into the whole "cup your hand like so" story or we could take a little literary license and use a word for something other than its dictionary meaning.... it got the point across to the listener and that was the goal.

I still dont understand how if it is gear noise it happens only in drive ( when under load ) not in idle. And how opening the bypass lessens the noise....

Nor do I understand why, if it is gear noise, ALL trucks with pullies dont get it.

Doug