2nd opinions on turbo please

BruceK

Well-known member
Joined
8 Feb 2015
Messages
8,318
Location
Conwy
Visit site
Following on from my previous thread I have removed the exhaust elbow on the two engines about to take the turbos off. The fans are perfect. No sign of wear at the tips and the gap between blade and housing is much less than a 1mm by sight. There is no play whatsoever eirher. Everything looks and feels perfect and I am about to cancel sending them in for a refurb but for 1 thing. When I spin them with a finger there is just enough drag that they wont free spin. I would say the drag is about as much as youd feel from a feeler guage that is perfectly set. Does that sound right? Or are the bearings tight? Id have thought it would freewheel easily.
 

BruceK

Well-known member
Joined
8 Feb 2015
Messages
8,318
Location
Conwy
Visit site
When I say perfectly set. By force not any notchiness . As if there was a weak magnetic force holding it back.
 

petem

Well-known member
Joined
16 May 2001
Messages
18,701
Location
Cotswolds / Altea
www.fairlineownersclub.com
Following on from my previous thread I have removed the exhaust elbow on the two engines about to take the turbos off. The fans are perfect. No sign of wear at the tips and the gap between blade and housing is much less than a 1mm by sight. There is no play whatsoever eirher. Everything looks and feels perfect and I am about to cancel sending them in for a refurb but for 1 thing. When I spin them with a finger there is just enough drag that they wont free spin. I would say the drag is about as much as youd feel from a feeler guage that is perfectly set. Does that sound right? Or are the bearings tight? Id have thought it would freewheel easily.

Pics?
 

vas

Well-known member
Joined
21 Jun 2011
Messages
7,952
Location
Volos-Athens
Visit site
Bruce, can't you get someone a tad more experienced to feel the rotors spinning and tell you what he thinks?
Should really spin freely, but now quantifying freely vs a magnet holding them is a bit too much...

V.
 

Portofino

Well-known member
Joined
10 Apr 2011
Messages
12,219
Location
Boat- Western Med
Visit site
I,ll go the other way they should freely spin like a kids gyroscope when twanged with a finger .

Generically speaking it’s the oil or lack of it that leads to bearing failure , those bearings get very hot .
Not wanting to widen the thread into oil quality ( the stuff and it’s filter change Fq ?) or oil temp before getting up on the plane or cool down phase when coming off .
Your turbo bearings are a barometer of the oil quality.

I suspect 1mm gap is at the outer range too .
 

Mr Googler

Well-known member
Joined
11 Apr 2008
Messages
5,519
Visit site
I would check:

All the air intake pipe work
replace the seals in the pipe between the charge air cooler and turbo.
Clean the charge air cooler.

When I bought mine, it wouldn’t rev past 3100 on one engine (other would only make 3500 for obvious reasons) and the supercharge did weird things. New turbo helped but didn’t solve. Once I got it back home a bolt on the charge air cooler casing had snapped. Looked fine when not under boost. Laid down the side of the engine and got the supercharger to cut in......the casing opened up and dumped all the boost! Surveyor and 2 x marine engineers missed that. Once that was sorted....moocho power!

If you’re losing air anywhere, it could give the same effect as a worn turbo.

I have a rebuilt turbo sat in the garage so I’ll take a video of the “spin”
 
Last edited:

Portofino

Well-known member
Joined
10 Apr 2011
Messages
12,219
Location
Boat- Western Med
Visit site
A boost pressure test insitu is what’s required.

Here’s the detail of the bearing
Engine oil is the life blood of a vehicle, and without it the modern turbo simply could not function. The oil performs two key functions within the engine – firstly, it lubricates the various components which are required to move. With respect to a turbocharger, this means the main shaft assembly, onto which the compressor and turbine wheels are mounted.

Most modern turbochargers utilize a ‘plain’ bearing system to control the movement of the main shaft. This means that they rely on a film of high-pressure oil to support the shaft, and consequently there is zero contact between the shaft and the housing. The shaft effectively ‘floats’ while it rotates at very high speed. Despite the film of high-pressure oil, the velocity with which the shaft must rotate in a modern turbo to generate the required flow of air (over 240,000rpm – that’s 4,000 rotations per second!) results in a very rapid build-up of heat.

The second function of the engine oil is to transfer that build-up away from the highly stressed components, and thus prevent temperatures from rising to the level that would soften the construction materials, or cause total mechanical failure of the turbo.

Here the effect of bad oil

a) Oil deterioration: The high temperatures that are present in modern diesel engines can cause oils to crack or break-down. This action produces carbonaceous (tarry) materials, which stick to the engine rings and cause other troubles. Oxidisation is caused by the hydrocarbons in the oil mixing with the oxygen; this produces organic acids of which there are two main types: those with low boiling points and those with highly corrosive.


These products are responsible for several of the problems on diesel engines and turbochargers. If the acids are al-lowed to become concentrated, they will attack the bearings etc., causing pitting and subsequent failure. Also they react to the remaining oil to form sludge, this is then deposited throughout the engine, particularly in the filters aggravating the turbocharger oil supply. Heavier oxidation causes hard varnish to appear.

Where sludge is allowed to accumulate in the oil systems, as this passes through the turbo it is thrown by centrifugal force from the rotating shaft against the walls and internal surfaces of the bearing housing where it can stick and impede the free oil flow. In time the build-up will cause problems with oil drainage, resulting in oil leaking from the turbine end of the unit.

If this matter is allowed to accumulate on the turbine side, the heat will cause a baking to take place and the result is usually unbalance in the turbocharger system.

We are back to my pet subject EGT,s .
A lower EGT , range 550 to 625 means more “ gum “ and bad “acid “ formation .
So all you guys doing extended pootling or running off boost with high performance diesels engines in your boats are not doing them any favours .
Your KAD ,s and D series should be 3100 to 3400 , folks like me with ex truck engines ,which lets face it are souped up should be about 80;% load , the turbos the oil temp , the oil coolers and filters sitting in the designed range and crucially the EGT ,s In the optimal range as much as poss minimising the build of “ gum” in the oil - so as I said your turbo bearings are the barometer and will go firsts , get slugged up / acid decay etc .

What’s happening here with Bruce’s engines is the rpm .
For example let’s keep the maths simple ,
Optimal boost is 100000 rpm .
Visible inpection = nothing abnormal except sticky - don,t free spin - my point .
Bearings gummed up in such away that only say 96000 rpm is reached but it really needs this every rpm to achieve boost .If the” gum “ or stickiness means a drop , a tiny drop to 95950 rpm then the boost drop is picked up and the Super charger kicks in as the revs drop off .
Somehow it then manages to climb above the critical SC support level , then drops below etc etc .

The power for the boat is on the edge and everything needs to be within say 98 % of efficiency, so as FARSCO infers a fouled charge air cooler , or slight leaky gasket - anything that tips the Hp down is gonna cause extra work on the other systems and amplify there issues .Theres hardly any headroom for a power drop .
In another application the very same engines say in a Targa 30 or 34 a rpm drop to 96000 might not be noticeable, these examples may take a bigger drop say be asymptomatic at say 92000 rpm .

That’s why it’s difficult comparing the SAME engine in different boats - depends how much headroom in power there is .

The KAD s are overly complicated and virtually every system needs to be tip top .
D 6 had a good star rewriting , resetting the Hp and torque bar for mid and sub 40 ftrs , but it didn’t,t take long for the builders to fit them in 40 to mid forty ftrs and then IPS them , then add superchargers and then builders moved to 45/50 ftrs - again minimal headroom for a an once of Hp loss , everything needs to be tip top 98-100 %
 

Portofino

Well-known member
Joined
10 Apr 2011
Messages
12,219
Location
Boat- Western Med
Visit site
https://1drv.ms/v/s!AielKv6BpFtrhuB4FR8Khi2wzOfJog

See if this works

The sound you can hear is my fat fingers hitting the casing!

That’s a “free spinner” in my book .
So using the anology used post #13 if 100000 rpm is factory spec and 96000 rpm or below problems occur ,Re boost not enough i would say that would be Ok and get nearer to the 100000 than 96000 rpm .

Those rpm numbers are just for illustration of the principle btw not gospel VP data .
 

volvopaul

Well-known member
Joined
1 Apr 2007
Messages
8,807
Location
midlands
hotmail.co.uk
I would check:

All the air intake pipe work
replace the seals in the pipe between the charge air cooler and turbo.
Clean the charge air cooler.

When I bought mine, it wouldn’t rev past 3100 on one engine (other would only make 3500 for obvious reasons) and the supercharge did weird things. New turbo helped but didn’t solve. Once I got it back home a bolt on the charge air cooler casing had snapped. Looked fine when not under boost. Laid down the side of the engine and got the supercharger to cut in......the casing opened up and dumped all the boost! Surveyor and 2 x marine engineers missed that. Once that was sorted....moocho power!

If you’re losing air anywhere, it could give the same effect as a worn turbo.

I have a rebuilt turbo sat in the garage so I’ll take a video of the “spin”

When I survey any kad series I place a fly blade screwdriver on the kick down switch , this brings the super charger in at idle , you can then have a feel around the air inlet tract for any possible leaks . Sounds like your engine man was a bit of a novice .
 

vas

Well-known member
Joined
21 Jun 2011
Messages
7,952
Location
Volos-Athens
Visit site
Thanks. My blade gaps are as good as yours. Spin on mine marginally tighter but engine room is below 3 C

20mins in the e/r attacking the turbo housing with a 2KW hairdryer will sort out the 3C Bruce, then you see if it spins nice or not.
Alternatively wait for June :p

V.
 

BruceK

Well-known member
Joined
8 Feb 2015
Messages
8,318
Location
Conwy
Visit site
Dont rub it in Vas :D My deck was under 2 inch of hard pack ice mid week. Relatively speaking today was warm.
 
Top