'06 Opti 150, New compressor and increased air related noise, help - what to do?

[leaky]

I've got a pair of these with ~900 hours. The background - one runs perfect in all respects, ridiculously perfect almost, the starboard engine. The port engine has had a minor cold idle problem I can't put my finger on and have been at it for awhile, tinkering for years maybe - recent thread on it as follows: http://www.screamandfly.com/showthre...05#post2956805

The starboard (again, perfect running) engine had a compressor fail last year, bearing went. I replaced w/ a new compressor. It was eating at me that I was tempting fate by not yet replacing the same on the port so I did. It didn't change the idle quality good or bad, however what I've noticed which may have happened from the instant I started it post-replacement or began at some point within the first couple hours, is the port engine has an air-related compressor sound emitting from the exhaust housing at a volume waaaay higher than the starboard. At first I ignored it, dismissed as new compressor should quiet down, but it's not, might even be getting louder not sure, have run it about 20 hours since installed.

What I'm speaking of is the somewhat higher pitched compressor sound I'd describe like it comes from an air driven instrument like a flute, sorta a honking noise even, not a bearing or belt squeal or anything, as if the blow off side of the air compressor on the port engine is doing something with higher pressure involved. Now if I listen to the starboard engine I swear it makes the identical noise just at a much much lower volume, that sound is very loud from the port engine. I wouldn't think anything of it except the port is just way louder.

Other things - it seems to go away at anything much above idle and I can tone it down by putting my finger somewhat over the intake to the compressor, ie create a little vacuum and maybe you have less pressure and less sound - that's what's got me 95% sure this is a compressor sound related to air, can be throttled by messing w/ the intake. The actual air compressor is not noisy at all rather this sound is 100% emitted from the exhaust housing somehow, not even sure it comes out with the exhaust seems to pass through the aluminum housing if you listen around to where it's loudest.

Thoughts on what to do? Is this likely to be a bad compressor or another bad part on the port engine? (the port which has some pre-existing issue I believe impacts all cylinders, keep going back to one of the valves on the fuel/air rails but have not gone into them yet)..

One thing I'm very tempted to do is swap the compressors, only thing that's stopping me is I think I ought to re-prime the oil system when I do (by putting them in break in mode) and I hate screwing with the perfect running engine by choking it with oil but it would certainly isolate the compressor from the rest of the engine and shouldn't really hurt anything other than maybe I'm into them for plugs again a month later.

Thanks in advance!

Jon

[XstreamVking]

All I can add is that I have 4 opti's and they all have their own sound at idle. Some make a woka,woka sound and some make more of a muted clicking / clacking sound. If it runs good, just run it....jm2cts

[leaky]

Thanks! Funny it's hard to describe the sound, I think both of mine make something I describe as a boop boop boop boop horn sort of noise but the port engine does it at such a volume you can hear it over everything else.

Update - yesterday I pulled the belts off both compressors and gave everything a hard visual/feel inspection to see if there was any difference between the two and in every respect I see nothing different, they feel like nice tight new compressors, which they are.

Ran the port engine again to make sure I'm not going to crazy and what I'm saying is accurate, air related sound, goes 100% away playing with the intake to the compressor by restricting it, sound is omitted from a place I can't put my finger on, almost is louder down by the water intake to my ears, kinda comes out of the aluminum case and not out the holes that emit exhaust.

Also played around with the test valves on the air side of both engines rails, a turn or two on the compressors wheel and you build good pressure on the air rail that holds, not a hugely meaningful test but basically there is nothing leaking down very quickly as I wouldn't be able to build pressure so easily by hand.

Jon

[XstreamVking]

You can use a tire pressure ga on the air side to just do a shade tree check while the motors are running. Soapy water in a spray bottle to check for leaks in the air hoses also works. If you don't know, the water supply for the compressors has a screen on it that needs cleaning from time to time. Port side low on block.

[leaky]

You can use a tire pressure ga on the air side to just do a shade tree check while the motors are running. Soapy water in a spray bottle to check for leaks in the air hoses also works. If you don't know, the water supply for the compressors has a screen on it that needs cleaning from time to time. Port side low on block.

Thanks - yes I may go and do that again w/ the pressure gauges, one of the zillion things I've done trying to smooth the idle on that engine which has only confirmed to be good, but now with the noise I'm trying to understand maybe it will uncover something.

If we are talking about the plastic fitting w/ the screen that screws into the block or exhaust adapter then yes I'm aware of it, I clean it out from time to time when I have the lower cowling off or when I'm doing a complete cooling overhaul (yearly I do water pumps, when something seems wacked out I go and do the poppet valve, that screen, closely inspect hose routing sometimes replacing anything that's wearing to a kink, and t-tats, although that screen never has more than a little bit of seaweed on it in my experience).

Jon