KAD43 lagging port engine video

DavidJ

DavidJ

Well-Known Member
Joined
15 Jun 2001
Messages
5,984
Location
home in Brum. S37 sold, was in Med Spain.
Visit site
[video]http://vid247.photobucket.com/albums/gg141/JDAVID966/KAD43%20RPM_zps68klomww.mp4[/video]

Twin KAD43's , 400hrs usage from new, clean props throttles opened exactly the same. Belts all done up to torque, The port engine lags and actually falls behind a little on acceleration. After a minute or so all levels off and everything is fine but what's going on during that initial acceleration?

hmmm how do people have a nice little thumbnail
 
Last edited:
Every engine is different, is this event something which you have seen change gradually or have you just noticed it ? If youve noticed a gradual change in performance you may have a problem, if its always done that then maybe you have not.

Power delivery could be altered by many different things, a soft turbo hose on the induction side could cause a restriction, or a leaking hose on the pressure side could create a split in power delivery.

An engine fed cold air into the filter, with the second engine being fed hot air into the filter will create a split, as the engines are dealing with different quantities of air temperatures swallowed up.


Turbo engines like a nice cold air feed, more dense air equals more power, a restriction in the air filter could cause a split, I have little experience of twin diesels engines, but have a reasonable knowledge of of truck based turbo diesels and high output turbo petrol engines.

Does your engineer have a table of acceptable tolerances between your engines ?
 
Assuming tachometers are accurate .
Turbo low boost - assuming no air leak -I would have a look to see if the vanes are tight up to the housing -tips can burn -back to raised EGT issues .
Or just worn bearings -hot lub oil bakes on -or just normal wear of the bearings-they do go slowly .

Needs full boost of both ,to get up and plane -more wieght slower it will take .Once up and levelled out demand /load is less so weak one catches up -helped by the stronger one .
As it deteriorates the gap widens -from odd intermittent to every time .
 
I'd start by checking for air leaks from the supercharger pipework.
Try running both engines up in neutral at the dock with the hatch up, see if the same thing happens, and if one engine sounds more 'whooshy' than the other one at 1500rpm+
To test the supercharger clutch, you could swap them over and see if the problem swaps sides.
 
Before getting too technical ensure that the filters and pre-filters on both are clean and you don't have fuel contamination or air in the system. In 95% of cases low power = fuel starvation
 
On a KAD 300 super charger deals with low end clutch kicks in 1400 rpm ,goes out 2600 rpm -where turbo is supposed to take over .up to cruise 3000-3200
On the vid all is well low down to approx 2500 rpm suggesting supercharges are ok ? From here up -start of turbo boost .
I sold mine when this happened local French Vp agent suggested new turbos + clean out SWAC .
Buyers surveyor did not pick up on this -it behaved it's self @ sea trail -phew !
Comes on gradually worn turbo,s ,initially dismissed as a bit of 8hit in the fuel , dirty bottom , props need a clean etc .
Obviously check for air leaks .But if there are not any -turbo,s worn .Guess really need to check boost pressure to confirm diagnosis
 
Ah, have just seen the video.
Yes, looks like low turbo boost from the Port Engine. Running with a boost gauge would confirm.
 
How do you know the throttle position is the same on both engines. They are mechanical and one is longer then the other and will not respond in an identical manner.
Anyways before going into something is really wrong with the engines I would do a similar check but hitting wot directly and doing a similar video. Also make sure you record wot rpm once the boat settles at top speed.

If top speed rpm on both engines are the same and one engine still lagging I would check the compressor, if they are not the same I would check the the turbo pressure and if ok I would swap the props and see if the rpm lag moved to the other engined and if so get new props or have them checked/adjusted.
 
Thanks A8
I've experienced the same symptoms over dozens of varying accelerations. The one shown is not the most extreme and the video shows an actual small reduction in revs while I'm still pushing the levers down (your not to know this of course)
So it's all pointing at low boost pressure at the moment.
Thanks for your input and thoughts on the problem
Cheers
David
 
DavidJ said:
Thanks A8
I've experienced the same symptoms over dozens of varying accelerations. The one shown is not the most extreme and the video shows an actual small reduction in revs while I'm still pushing the levers down (your not to know this of course)
So it's all pointing at low boost pressure at the moment.
Thanks for your input and thoughts on the problem
Cheers
David
Click to expand...
Just had exactly same problem on a kad 44 turned out to be a Seized turbo shaft .
Revs and pick up virtually the same . Check shaft .
 
volvopaul said:
Just had exactly same problem on a kad 44 turned out to be a Seized turbo shaft .
Revs and pick up virtually the same . Check shaft .
Click to expand...
Thanks Volvopaul
This will seem a silly question for you but how do I get to the shaft to check it?
I'm capable of doing engine strip downs (not done a turbo) but is there a quick fix which may get it spinning again.
Cheers
David
 
Last edited:
DavidJ said:
Thanks Volvopaul
This will seem a silly question for you but how do I get to the shaft to check it?

If it is seized how do I free it?
Cheers
David
Click to expand...
To get a proper look at the inlet blades take the black elbow off the inlet side of the turbo hi how means taking the air filter box off , 2 10 mm head bolts , 1 hose clip and slide it away , you need an Allen key to undo the elbow off the turbo .
Also take off the pipe between the turbo and intercooler and check the o rings .
Run the engine at idle , place a screwdriver blade across the proximity switch to bring the super charger in , feel around the turbo pipes for air escaping . Do this before you dismantle anything.
 
volvopaul said:
To get a proper look at the inlet blades take the black elbow off the inlet side of the turbo hi how means taking the air filter box off , 2 10 mm head bolts , 1 hose clip and slide it away , you need an Allen key to undo the elbow off the turbo .
Also take off the pipe between the turbo and intercooler and check the o rings .
Run the engine at idle , place a screwdriver blade across the proximity switch to bring the super charger in , feel around the turbo pipes for air escaping . Do this before you dismantle anything.
Click to expand...

Thanks for you quick reply as I was modifying my question.
I believe the Kad43 has an electronic super charger switch and not a proximity switch. Can I rev the engine to 1600 to bring in the super charger and do the test.
Cheers
 
I personally think boost leak as long as your charger is coming in ?
In that video you wasn't even getting to enough revs for charger to cut out and turbo to take over fully.
Get a friend to rev to 1600-1800 rpm in neutral whilst u are in engine bay. ( safer 2 of u )
Get your self some gas leak spray and then spray or all the boost pipe work including aftercooler end caps and look for bubbles, bad boost leaks u will feel by hand and u will defo see & hear the super charger engage if it's working.
Good look.
 
Thanks Frank
My compressor is definitely switching in at 1600 RPM although you can't hear it in the video.
Your observations are really interesting and I like your idea for testing using gas leak spray. I'm not going to the boat again until September and will try your idea then as well as those suggested by volvopaul and others who have kindly contributed to my thread.
I'll feed back my results and hopefully the cure in a couple of months
Cheers
David
 
Last edited:
Just before you get really technical please lift the legs and check you have all four props, we just had a customer who thought his port engine was under performing, lower revs, poor acceleration. The 'engineer' from a well known company came and he checked all of the above symptoms, with no explanation found.
I just lifted the legs and diagnosed a missing starboard propellor, took all of 20 seconds, his face was a picture, until he realised how expensive Volvo prop are........
 
Jonmendez said:
Just before you get really technical please lift the legs and check you have all four props, we just had a customer who thought his port engine was under performing, lower revs, poor acceleration. The 'engineer' from a well known company came and he checked all of the above symptoms, with no explanation found.
I just lifted the legs and diagnosed a missing starboard propellor, took all of 20 seconds, his face was a picture, until he realised how expensive Volvo prop are........
Click to expand...

You can't plane with three propellors (see the video).
I know this from first-hand experience :(
 
I'd say it was just different throttle positions given that the port engines rev's started 200 rpm down before the throttles were opened. Those 200 revs will make it over fuel more than the other at the beginning and keep it behind till as you say everything evens out.
 
It could be one of the propellers on the "good" engine is slipping on it's bush and it's the "bad" engine doing extra work to make up for it causing it to lag.
 
You must log in or register to reply here.

Share this page

Top