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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Diesel > Repower confusion (horsepower)
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Thread: Repower confusion (horsepower) Reply to Thread
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Topic Review (Newest First)
03-02-2013 04:52 PM
redhead78
Re: Repower confusion (horsepower)

Stay away from the turbo it's eventually going to need maint you don,t need it,and remember which ever engine you choose you have to run hem hard.
02-22-2013 07:43 PM
Faster
Re: Repower confusion (horsepower)

Quote:
Originally Posted by klem View Post
Faster,

To add the jrd22's comments on ....
Good stuff, thanks Klem...
02-22-2013 07:04 PM
Minnewaska
Re: Repower confusion (horsepower)

jrd.... thanks for the PM.

On the topic of retrofitting to sans turbo, I actually explored that option. It requires a bit of plumbing to ditch the turbo, a new fuel pump, new injectors and some tweaking I didn't follow. Bottom line was about the cost of a new turbo. Figures, doesn't it.
02-22-2013 06:58 PM
tommays
Re: Repower confusion (horsepower)

My friend has the darn turbo Volvo in his tartan 372 and when replacement time came it was going to be a different motor.

UNTIL the costs came in to to relocate all the stuff that was in completely different places compounded by the fact that on a 372 those places are under the kitchen sink

The freaking Volvo got fixed
02-22-2013 06:47 PM
klem
Re: Repower confusion (horsepower)

Faster,

To add the jrd22's comments on running an engine with a blown turbo, it is a bit different in a sailboat than in an OTR vehicle. In an OTR vehicle, you are simply down on power. In a boat, without multiple gears, the load on the engine is determined by the rpm, the condition of the prop and the drag of the hull. The problem is that you can end up being unable to get the rpm up very high so you are not up in the power band meaning that your power is much more reduced than in an application where you have gears and can decouple the relationship between load and rpm.

There are really 2 reasons why you are down on power when you have a blown turbo. One reason is simply that you cannot get enough air into the engine so you will not be burning the fuel at all efficiently. The other reason is that except for the really old turbocharged engines, all engines have some form of fuel limiting feature which is based on airflow. On older mechanical injection diesels, it will be an air fuel control which generally has a line coming from the intake to the injection pump. The line is pressurized by the intake and it operates a diaphragm in the injection pump controlling your maximum fuel delivery. On newer electronic injection engines, it is more common to have a MAF sensor and control your maximum injection based on that. Performance guys tend to disable these features and I have actually seen a diesel run so rich that it shut down.

There is a slight danger with exhaust gas temperatures if you are running with a blown turbo. Most stock engines won't let you run hot enough to have a problem here but some could cause piston and valve damage.

The real problem with running with a blown turbo is that the most common thing to go is the bearings. When these go, the turbo shaft will get a lot of play and it will often start to leak oil into the intake which can lead to a runaway situation. I make a point of grabbing the compressor wheel and checking for radial play whenever I have an intake off.

The good news is that turbos are remarkably durable. Excluding the new variable geometry turbos which can stick, almost all of the blown turbos I have seen have had a ton of hours on them or been in a bombed (better of modified baby) engine.

Sorry for the slightly off topic post but I hope it is helpful.
02-22-2013 05:43 PM
jrd22
Re: Repower confusion (horsepower)

I heard back from Ted Brewer. Based on displacement the hp range for our boat would be 35-50.
02-22-2013 05:01 PM
Faster
Re: Repower confusion (horsepower)

Yeah... makes sense, John....
02-22-2013 04:27 PM
jrd22
Re: Repower confusion (horsepower)

Fast- it messes up the combustion a bit because the injectors are designed for a certain volume/pressure of intake air. If the turbo is just not functioning then the intake air isn't pressurized so you normally get some smoke, and like you say, reduced power. We had a couple of turbos lose almost all of the vanes on the intake side due to sand blasting (blown or "missing" air filter in extremely dusty conditions) and the engines ran OK, just smoky and not as much power. I would guess that some of the higher tech electronically controlled engines would go into "limp" mode when the sensors detected lack of boost pressure. Usually though it's seals or bearings that go and I'm not sure how you could re-route the exhaust and intake if you physically removed it.
02-22-2013 03:05 PM
Faster
Re: Repower confusion (horsepower)

Curious.... what happens if you run a turbo engine without a functioning turbo? Besides loss of power what are the issues? Obviously if there are bad bearings etc and you can't disable the turbo that's one thing... and otherwise?
02-22-2013 02:57 PM
jrd22
Re: Repower confusion (horsepower)

Minne- sent you a PM re. turbo.
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