Old Perkins Diesel questions:
I have questions for diesel experts on this forum about "detuning" my
Perkins 6 cylinder Turbo diesels. I would also welcome suggestions for
other forums where this might be posted.

Background: I have a 34' Silverton hull that I have rebuilt as a pilot
house trawler. The boat is powered by twin 354" 180HP Perkins 6 cylinder
turbo diesels. This is WAY more power than I ever need for this boat. I
run it like a trawler even though it is a planing style deep V hull design.
These motors have given me more than 1200 hours of reliable operation
loafing along at 1200 to 1300 RPM.

I wish to simplify the plumbing on the motors to have fewer maintenance
items and gain space in the engine room. My first choice would be to find
someone with a similar pair of normally aspirated Perkins and do an even
swap. But that is likely to be hard to find.

Second choice is to get rid of some of the turbo related plumbing on my
motors. I am well aware of all the differences in injection pump specs
between normally aspirated and turbo diesels.

A good place to begin would be removing the large, bulky intercoolers and
running the turbo outlet directly to the intake manifold. There would be a
huge gain in engine room space and accessibility, and I would not have to
maintain the intercoolers. MY OPINION is that the importance of the
intercooler increases as the diesel gets closer to full throttle operation.
My guess is that at half throttle or less as I use these motors, I would not
notice much difference without the intercoolers. The fuel /air mix at
cumbustion would be a little less dense, but not greatly so. Opinions?

A third choice is to remove the turbo's all together. At idle, a turbo does
very little. But I suspect that you would get quite a rich mixture and a
smokey exhaust at even moderate loads. Does anyone have experience (perhaps
through losing a turbo while on a long cruise) with how well a turbo diesel
works at low to mid power without a turbo?

Thanks for any input (or even speculation) - Tom
respond here or: removing percent signs:

With what little I know I would think that removal of the turbo's would put
you in the 105 HP range. Like the old Lehman 6 cylinder. I believe that
the base engines are the same - Ford. Suggest you call American Diesel in
VA and explain your problem and what you want to do. After they stop
laughing because it will be the first time they have ever heard this one,
they will give you some good advise. By the way they can also sell you the
parts needed.

Too much horsepower - Its a first...

"tkranz" wrote in message
...
Old Perkins Diesel questions:
I have questions for diesel experts on this forum about "detuning" my
Perkins 6 cylinder Turbo diesels. I would also welcome suggestions for
other forums where this might be posted.

Background: I have a 34' Silverton hull that I have rebuilt as a pilot
house trawler. The boat is powered by twin 354" 180HP Perkins 6 cylinder
turbo diesels. This is WAY more power than I ever need for this boat. I
run it like a trawler even though it is a planing style deep V hull
design.
These motors have given me more than 1200 hours of reliable operation
loafing along at 1200 to 1300 RPM.

I wish to simplify the plumbing on the motors to have fewer maintenance
items and gain space in the engine room. My first choice would be to find
someone with a similar pair of normally aspirated Perkins and do an even
swap. But that is likely to be hard to find.

Second choice is to get rid of some of the turbo related plumbing on my
motors. I am well aware of all the differences in injection pump specs
between normally aspirated and turbo diesels.

A good place to begin would be removing the large, bulky intercoolers and
running the turbo outlet directly to the intake manifold. There would be
a
huge gain in engine room space and accessibility, and I would not have to
maintain the intercoolers. MY OPINION is that the importance of the
intercooler increases as the diesel gets closer to full throttle
operation.
My guess is that at half throttle or less as I use these motors, I would
not
notice much difference without the intercoolers. The fuel /air mix at
cumbustion would be a little less dense, but not greatly so. Opinions?

A third choice is to remove the turbo's all together. At idle, a turbo
does
very little. But I suspect that you would get quite a rich mixture and a
smokey exhaust at even moderate loads. Does anyone have experience
(perhaps
through losing a turbo while on a long cruise) with how well a turbo
diesel
works at low to mid power without a turbo?

Thanks for any input (or even speculation) - Tom
respond here or: removing percent signs:

With what little I know I would think that removal of the turbo's would put
you in the 105 HP range. Like the old Lehman 6 cylinder. I believe that
the base engines are the same - Ford. Suggest you call American Diesel in
VA and explain your problem and what you want to do. After they stop
laughing because it will be the first time they have ever heard this one,
they will give you some good advise. By the way they can also sell you the
parts needed.

Too much horsepower - Its a first...

"tkranz" wrote in message
...
Old Perkins Diesel questions:
I have questions for diesel experts on this forum about "detuning" my
Perkins 6 cylinder Turbo diesels. I would also welcome suggestions for
other forums where this might be posted.

Background: I have a 34' Silverton hull that I have rebuilt as a pilot
house trawler. The boat is powered by twin 354" 180HP Perkins 6 cylinder
turbo diesels. This is WAY more power than I ever need for this boat. I
run it like a trawler even though it is a planing style deep V hull
design.
These motors have given me more than 1200 hours of reliable operation
loafing along at 1200 to 1300 RPM.

I wish to simplify the plumbing on the motors to have fewer maintenance
items and gain space in the engine room. My first choice would be to find
someone with a similar pair of normally aspirated Perkins and do an even
swap. But that is likely to be hard to find.

Second choice is to get rid of some of the turbo related plumbing on my
motors. I am well aware of all the differences in injection pump specs
between normally aspirated and turbo diesels.

A good place to begin would be removing the large, bulky intercoolers and
running the turbo outlet directly to the intake manifold. There would be
a
huge gain in engine room space and accessibility, and I would not have to
maintain the intercoolers. MY OPINION is that the importance of the
intercooler increases as the diesel gets closer to full throttle
operation.
My guess is that at half throttle or less as I use these motors, I would
not
notice much difference without the intercoolers. The fuel /air mix at
cumbustion would be a little less dense, but not greatly so. Opinions?

A third choice is to remove the turbo's all together. At idle, a turbo
does
very little. But I suspect that you would get quite a rich mixture and a
smokey exhaust at even moderate loads. Does anyone have experience
(perhaps
through losing a turbo while on a long cruise) with how well a turbo
diesel
works at low to mid power without a turbo?

Thanks for any input (or even speculation) - Tom
respond here or: removing percent signs:

_usually_ a turbo engine has different pistons in it than the same engine
normally aspired.

Is the Perkins different?

removal of the turbo's would put
you in the 105 HP range

_usually_ a turbo engine has different pistons in it than the same engine
normally aspired.

Is the Perkins different?

removal of the turbo's would put
you in the 105 HP range

Yes, that is part of the equation. Different pistons, injection pump
calibration, probably different cam timing and perhaps compression ratio.

All these differences between normally aspirated and turbo become more and
more critical as a diesel gets closer and closer to peak power.

At idle, a the turbo does almost nothing. The question here is how much
removing the intercooler would affect partial throttle operation.
"JAXAshby" wrote in message
...
_usually_ a turbo engine has different pistons in it than the same engine
normally aspired.

Is the Perkins different?

removal of the turbo's would put
you in the 105 HP range

Yes, that is part of the equation. Different pistons, injection pump
calibration, probably different cam timing and perhaps compression ratio.

All these differences between normally aspirated and turbo become more and
more critical as a diesel gets closer and closer to peak power.

At idle, a the turbo does almost nothing. The question here is how much
removing the intercooler would affect partial throttle operation.
"JAXAshby" wrote in message
...
_usually_ a turbo engine has different pistons in it than the same engine
normally aspired.

Is the Perkins different?

removal of the turbo's would put
you in the 105 HP range

how much
removing the intercooler would affect partial throttle operation.

a quick guess would be that you might be courting overheating issues.

The engine pushed full displacement air through the engine idle or WFO, with
the slight difference that when the engine is very lightly loaded the turbo
pumps out less extra air. My guess is the engineers have "tricked out" the
turbo to give more or less full umph from maybe about 1/3 throttle on (just a
guess, but some figure less than 100% is a for sure).

Taking out the (designed in) intercooler would force less dense and hotter air
into the cylinder.

Is that a problem? I'd guess you would want to talk to a design engineer on
that one. You have both the issue of less dense/hotter air and the issue of
what's the right fuel amount for that air.

I dunno. I think I would be inclined to call the factory and try to skip
around inside the company until you can find an engineer type who knows his
business and doesn't normally talk to end users and is dying to help someone
out.

how much
removing the intercooler would affect partial throttle operation.

a quick guess would be that you might be courting overheating issues.

The engine pushed full displacement air through the engine idle or WFO, with
the slight difference that when the engine is very lightly loaded the turbo
pumps out less extra air. My guess is the engineers have "tricked out" the
turbo to give more or less full umph from maybe about 1/3 throttle on (just a
guess, but some figure less than 100% is a for sure).

Taking out the (designed in) intercooler would force less dense and hotter air
into the cylinder.

Is that a problem? I'd guess you would want to talk to a design engineer on
that one. You have both the issue of less dense/hotter air and the issue of
what's the right fuel amount for that air.

I dunno. I think I would be inclined to call the factory and try to skip
around inside the company until you can find an engineer type who knows his
business and doesn't normally talk to end users and is dying to help someone
out.

I just yanked the 165HP Perkins out of my boat. (Hydrolocked- due to a weird
failure in the intercooler- and with 4000 hours on a 20 year old engine it
seemed the right thing to do).

I replaced it with a naturally aspirated Perkins, somewhat the same engine but
with a better injection sytem and an exhaust manifold cooled with the engine
coolant rather than salt water. The NA version of the engine is 135HP.

I thought I'd probably lose a little speed, but I've picked up at least a half
knot.
(I do cruise the NA 100 RPM higher than
I did the turbo)

One of our local Perkins mechanics has told me, in the past, that he has been
able to convert the 165's to naturals.
I'm not sure what the process involves, but he led me to believe the engine
will still run
OK with the turbo removed. (It would make sense that the injectors and/or pump
might need to be changed.) At the lower end of the RPM range you report, you're
only getting "some" benefit from the turbo in any case.

I wouldn't worry much about overheating the engine due to lack of an
intercooler if you switch to NA- the air charge cooler is really only required
because the air gets
superheated when it is pressurized by the turbo. I'm not sure the air on the
output side of the air charge cooler could ever be considered refrigerated. :-)