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Old 23-09-2010, 21:11   #16
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Aloha Larson,

Sounds like you are getting 6 knots out of your engine. That is really good. How many RPM does it take to get the 6 knots?
kind regards,
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Old 23-09-2010, 22:04   #17
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7 mph is 6.08 Knots

Speed Converter.
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Old 24-09-2010, 00:34   #18
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Originally Posted by larson2032 View Post
I am only getting 7 miles per hour on the handheld gps so 4.5 knots.
Hull speed for the 43ft Columbia is given as max 7.7 knots,
you GPS reading converts t0 6.08 knots. Not too bad.
To get max HP out of the Perkins, one needs to run it at 4,000 RPM - not a good idea.
Another point to consider is that a turbo assisted diesel engine require high RPM for the turbo to kick in. If the engine is run without the turbo operating, the turbo will soot up over time.
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Old 24-09-2010, 00:57   #19
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Clean bottom, clean prop properly pitched? (geez, try saying that fast three times)
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Old 24-09-2010, 06:55   #20
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I bet that if the Hp were boosted that the normal leaks in the 4-108 would turn info major gysers!
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Old 24-09-2010, 10:43   #21
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Originally Posted by Laidback View Post
Another point to consider is that a turbo assisted diesel engine require high RPM for the turbo to kick in. If the engine is run without the turbo operating, the turbo will soot up over time.
I almost mentioned this myself...Thanks for doing it..


You need to think of turbos much in the same manner as a 4 barrel carburetor...They are not doing a thing for you until a certain throttle setting is achieved...THEN they kick in and add the benefit...not before.

If your seldom at that throttle setting they are more a hindrance then a benefit.
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Old 24-09-2010, 11:08   #22
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Quote:
Originally Posted by Laidback View Post
Hull speed for the 43ft Columbia is given as max 7.7 knots,
you GPS reading converts t0 6.08 knots. Not too bad.
To get max HP out of the Perkins, one needs to run it at 4,000 RPM - not a good idea.
Another point to consider is that a turbo assisted diesel engine require high RPM for the turbo to kick in. If the engine is run without the turbo operating, the turbo will soot up over time.

True,
You can match a turbo to the typical RPM range that you expect the engine to operate at, but then when you exceed that range (ie set your turbo to work well at 2200 rpm, but then rev to 3500 rpm) you can actually cause the turbo to "bark". It'll actually compress more air than the engine consumes, then need to release it in the direction that it was meant to enter the engine.
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Old 24-09-2010, 11:20   #23
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I have a couple pieces of equipment fitted with turbos they are nice in some ways....but every one of them sits in front of a torque converter to a hydrostatic transmission with out exception...(Except in the dump trucks)...where you seldom throttle down much to change direction and where the transmission shifts automatically to keep in step with the loads keeping the engine at its chosen RPM setting.

I have just never seen the need or application for them in a sail boat....Just my opinion.
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Old 24-09-2010, 11:30   #24
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Most automotive diesel engines that have a turbo also employ a waste gate. A turbo yanmar doesn't have a waste gate, but the turbo does almost exactally nil until you reach the upper end of the rpm range.
Larger engines like the 16V2000 and the 16V4000 detroits have dual sequential turbos that have been designed to operate across a range of engine speeds by by dumping all the exh gas into one until the engine speed/load comes up to a point. Then both are brought online, with a huge lag.
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Old 24-09-2010, 11:41   #25
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Quote:
Originally Posted by Stillraining View Post
I have a couple pieces of equipment fitted with turbos they are nice in some ways....but every one of them sits in front of a torque converter to a hydrostatic transmission with out exception...(Except in the dump trucks)...where you seldom throttle down much to change direction and where the transmission shifts automatically to keep in step with the loads keeping the engine at its chosen RPM setting.

I have just never seen the need or application for them in a sail boat....Just my opinion.
Well, the idea is you get more power out of more compact and lighter power plant. That a turbo does, and it has some benefit for a sailboat.

I think a turbo also enhances efficiency by recapturing some of the thermal energy out of the exhaust stream. Efficiency is good in a sailboat just like everywhere else.

Our boat has a 100 horsepower Yanmar turbocharged and intercooled diesel. It displaces only 2000cc and revs to 3800.

It is smooth as glass and quiet and efficient (smokes though). I guess it's ok. We run it at 2400 RPM most of the time.

But if I had had a choice, I would have gone for a naturally aspirated Perkins. This has double the mass -- it's a big old iron lump -- and displaces 4000cc. It only revs to 2800 or something like that. Built like a brickhouse, dead simple, and much less to go wrong. Noisy and vibraty, but less stressed. In my opinion those values are even more important in a blue water sailboat where you plan to be thousands of miles from civiliztion.
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Old 24-09-2010, 19:07   #26
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Well, the idea is you get more power out of more compact and lighter power plant. That a turbo does, and it has some benefit for a sailboat.

I think a turbo also enhances efficiency by recapturing some of the thermal energy out of the exhaust stream. Efficiency is good in a sailboat just like everywhere else.

Our boat has a 100 horsepower Yanmar turbocharged and intercooled diesel. It displaces only 2000cc and revs to 3800.

It is smooth as glass and quiet and efficient (smokes though). I guess it's ok. We run it at 2400 RPM most of the time.

But if I had had a choice, I would have gone for a naturally aspirated Perkins. This has double the mass -- it's a big old iron lump -- and displaces 4000cc. It only revs to 2800 or something like that. Built like a brickhouse, dead simple, and much less to go wrong. Noisy and vibraty, but less stressed. In my opinion those values are even more important in a blue water sailboat where you plan to be thousands of miles from civiliztion.
Agreed, agreed and Agreed..
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Old 04-03-2011, 06:52   #27
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Re: Turbocharger Help for Perkins 4-108 Diesel

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I have heard from a long time 4-108 user on this forum that the 4-108 is nowhere near a 50 hp. engine,
The factory rates the 4-108 at 51 HP when turning 4000 RPM.

I have no doubt the numbers are correct, but for normal use, 4000 RPM is not recommended.

My car's engine is rated at 302 HP, but for normal driving I use less than half of that, the rating is still correct however.
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Old 04-03-2011, 09:30   #28
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Re: Turbocharger Help for Perkins 4-108 Diesel

There's probably not a sailboat engine that puts out the rated HP, Nobody runs their engine at the rated RPM's
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Old 04-03-2011, 18:33   #29
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Re: Turbocharger Help for Perkins 4-108 Diesel

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Nobody runs their engine at the rated RPM's
A few times I have used every bit of the 51 HP on the Perkins 4-108:
Going thru draw bridges in Fort Lauderdale when they try to close on you and take the mast down: Full war power and then some @ 4000 RPM was good to have a few times: Once the bridge was inches from the spreaders and less power would have dismasted the boat..The Bridge Operator got fired after that one when I complained: She never looked out the window before hitting the "Down with the Bridge Button".

Other times in Bimini trying to dock and to leave the dock with a strong current going: If I screwed up I could always gun the engine and muscle my way out of the situation. (Of course it never happened to me )

I have driven the same type of boat with the 30 HP Westerbeke and found the power on tap to be a lot less. (CSY 33 Cutter)
I have no doubt the Perkins will deliver the goods, but it is not for continous operation.
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Old 05-03-2011, 06:56   #30
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Re: Turbocharger Help for Perkins 4-108 Diesel

total custom install but doable
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