Compressor whine KAD

BruceK

BruceK

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On the later model KAD engines the manifold tube between compressor and air-box and air-box to turbo is of all steel construction with O ring connections. It also has a silencer between air-box and turbo. These compressors are subsequently comparatively quiet in comparison to the manifold of the early KADs which is thin walled aluminium tube with hose connectors. Mine are the early KADs, 42's and when the compressor kicks in they scream like banshee's.
(No my compressors are not on their last legs / sticky vanes etc)

My question is there was an interim period between the two designs where the compressor to air-box was all pneumatic hose.

Part 30 as opposed to part 20 in the diagram.

11400.jpg


Was this implemented in part or whole to reduce the whine noise? They are cheap (where as the KAD 44 and above system is going to set me back a couple of k to upgrade) so I ordered a pair as a punt but am curious to know if anybody can share any light on the issue?
 
Keen to know how you get on...I have earlier 42’s aswell and was going to get sound proofing for the floors
 
I have always felt it best not to run very long in the supercharger range so I have never been concerned about the noise.
 
FARSCO said:
Keen to know how you get on...I have earlier 42’s aswell and was going to get sound proofing for the floors
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I replaced my sound proofing, but to be quite honest there are just too many places in my boat that cannot be covered and it was a complete waste of expense, time and effort

MartynG said:
I have always felt it best not to run very long in the supercharger range so I have never been concerned about the noise.
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Yes but mine also kick in when some or other sensor feels the engine is labouring (kick down). In heavy weather the SC's can hunt, kick in and do all sorts of annoying things outside of the 1800 to 2400 rpm rev band

edit

just hear them beggars!

 
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A_8 said:
They should not do it like that, what rpm was that circa?
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Has nothing to do with rpm. That is the compressors kicking down as the waves try to knock the boat off the plane and loading the engines. Speed about 16knts

Edit

My SC's kick in ...
between 1800 and 2400 rpm - always
Kickdown - when the throttle is WOT but revs below 3100 - 3200 - always
Between 2400 and 3100 - 3200 if the engine start loading and revs drop (not necessarily at WOT)
 
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FARSCO said:
Mine don’t sound as loud as that :):):)
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Even with the engine hatch open? i.e. discount sound proofing.
My lower cockpit seating can fold away leaving an open deck. I find that really handy. The downside is, the cavity they fold down into cant be soundproofed so certain engine sounds on mine like the compressors dont seem to be damped much. Engine rumble conversely is more muted. Just one of those things
 
I might add I originally bought the boat with the SC's disconnected. One compressor was totalled and so has a new replacement and made that noise from the start. The other was sent in to be checked before buying the replacement as that noise made me suspect there was an issue with it.
This noise is amplified in the manifold, I am sure, when a friends KAD44 system started leaking air past the O-rings in their manifold it made the same noise. On mine I have rubber sleeve pipe connectors. When the SC's kick in they blow out like balloons and I'm sure that causes some sort of blowby rather like a balloon deflating while squeezing / pinching the neck of it.
 
BruceK said:
Has nothing to do with rpm. That is the compressors kicking down as the waves try to knock the boat off the plane and loading the engines. Speed about 16knts

Edit

My SC's kick in ...
between 1800 and 2400 rpm - always
Kickdown - when the throttle is WOT but revs below 3100 - 3200 - always
Between 2400 and 3100 - 3200 if the engine start loading and revs drop (not necessarily at WOT)
Click to expand...

The supercharger free areas are too narrow imho .
It feels to me like an American petrol boat that’s been adapted with diesels ( available at the time ) for the U.K. / EU mkt .
Unfortunately they are I,am afraid to say rarther inappropriate in the sense when new just enough grunt with a boat sans cruising stores .
I, don’t like the sound of the running @WOT 3100-3200 and they kick in just below if I understand what you are saying ?

The fact the superchargers can,t function correct with the turbos so there’s a nice wide operating band is symptomatic with the poor application for the weight ( drag ) of the boat .
Waves as you found out exacerbates the problem .
There’s also natural power loss over the years again exacerbated by running at WOT or near WOT due to chronic excess EGT ,s .The higher EGTs the more insidious valve damage occurs .Its not a switch , one min Ok next fault .Its ever so slight mushrooming and distortion of the valves and seats that leads to ever so slightly poorer fit and [ insert your value ] % power drop .

Additionally although others disagree ( another thread recently) i,sm of the opinion the VP superchargers are NOT designed for prolonged running .Theres confusion with constant running SC petrols in the automotive side .SC ing a diesels in terms of air vol and pressure are far greater and requires a far closer tolerances / fit of the vanes to achieve those pressures to be effective compared to a SC for a car petrol .
The wine on the VP SC is the vanes clanking together on there wear facets .As the bearings at the end of the vanes naturally wear the vanes that compress the air increase there surface area of contact so the noise increases , if you get any radial dial play then air will escape as the vanes are effectively wobbling on each other .

Short answer wrong engine application.

Imho
 
Do your superchargers do that when the sea is calm? I suspect not.
Are the props the right size ?
 
MartynG said:
Do your superchargers do that when the sea is calm? I suspect not.
Are the props the right size ?
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Ah , in my post #12 above I made the assumption the props were stock as nothing said .

However if I can just mod the last sentence in parentheses below -

( “ short answer wrong engine application “ ) for the props and weight / drag of the hull .

It think that sounds better ?
 
BruceK said:
Has nothing to do with rpm. That is the compressors kicking down as the waves try to knock the boat off the plane and loading the engines. Speed about 16knts

Edit

My SC's kick in ...
between 1800 and 2400 rpm - always
Kickdown - when the throttle is WOT but revs below 3100 - 3200 - always
Between 2400 and 3100 - 3200 if the engine start loading and revs drop (not necessarily at WOT)
Click to expand...

If they are the same as my ex KAD43 they were only rpm controlled (nothing to tell them if the engine was loaded or not) and could be adjusted. Can it be that you are underpowered as discussed and someone tried to get a bit more torque by letting the SC work higher up in the rpm range. I think mine cut out at around 2400 or thereabouts, absolutely not engaged at 3100 rpm's which might explain why yours sound like they do. Volvopaul should know exactly how this is supposed to work.
 
Regarding your video, you say you were doing 16 kts. Sounds about right for revs somewhere between 2400 - 2600 rpm. To me that sounds that you are just riding on the edge and as the revs fluctuate slightly due to waves, the SC cuts in and out.

On our Sealine F37 with KAMD300's the compressor noise was very noticeable in the saloon. So much so, in fact that we never ran longer periods of time at revs where the SC was on.

I had the pneumatic hose on a Kad42 years ago. Unfortunately I don't know why the design was changed, nor if the change made any difference to the noise as I had nothing to compare it to.
 
A_8 said:
If they are the same as my ex KAD43 they were only rpm controlled (nothing to tell them if the engine was loaded or not) and could be adjusted. Can it be that you are underpowered as discussed and someone tried to get a bit more torque by letting the SC work higher up in the rpm range. I think mine cut out at around 2400 or thereabouts, absolutely not engaged at 3100 rpm's which might explain why yours sound like they do. Volvopaul should know exactly how this is supposed to work.
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On mine there is a sensor pickup on the the pump that the throttle linkage activates. Im pretty sure yours would have had one too. If so yours may not have been working. ... ?
 
The Sc, s on the KAD 300 powered boat I had cut in @1400 and disengaged @ 2400 , with the caveat the turbos were in fine fettle .

It could stay ar say 2900 or 3000 rpm all day , waves just made the speedo vary .
However if the turbos start to fail then boost is lost so intermittently at say 3100 rpm one of the SC,s would kick in , and start hunting and there would be a significant reduction of speed until the correct boost re established.

My engineer diagnosed worn turbos and suggested refurbing them ,

I sold the boat and the buyers surveyor picked up on this so I knocked a bit off of a pre elivated price .

So this kicking in of the SC ,s way above the 2400 rpm cut out could be worn turbo related .

I suppose there’s some sort of boost pressure test - one for Volvo Paul ?
 
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