Turbocharging a Marine Engine
Hemicuda
group? I know that it used to be done back in the 70's but I can't
find any info about any current set-ups. From what I can find it
seems like it might be advantageous by allowing you to run a better
pitch prop for higher top end speed and reduced RPMs for cruising
which seem like it would be good for efficiency and engine life. I
don't think it would drop your low end that much because the
compression on stock marine engines is close to 9:1 and you can
probably run 10PSI of boost on 8.5:1 engines. Any thoughts or
comments? I am more familiar with turbo applications on cars so I
might be missing something. Thanks for the help!
Tony Thomas
On top end you would probably gain about 4" of pitch (600 rpms or so).
On the hole shot that would kill you since you don't have the power at 600
to 1000 rpms to turn that big a prop.
Now, a torque shift would work but the power on top end would tear the
gears/springs out of it. Plus it is not the most efficient for top end
which is what your looking for.
Racers use them but they are not looking at hole shot but rather sustained
high end speed.
--
Tony
My boats and autos - http://t.thomas.home.mchsi.com
"Hemicuda" <jhar...@msn.com> wrote in message
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ba...@psyber.com
It's quite common to turbocharge Grand National ski race boats. Usually
two of 'em.
b.
ba...@psyber.com
Forgot to mention. Try taking a look at Hot Boat Magazine. Past issues
would have examples of turbocharging V8's as well as many of their ads.
They also have a competent Technical Editor dept. that could probably point
you in the direction of companies that could help.
b.
ba...@psyber.com
: Forgot to mention. Try taking a look at Hot Boat Magazine. Past issues
: would have examples of turbocharging V8's as well as many of their ads.
Ack!
That should have been "Powerboat Magazine".
J K
From what I've read in automotive repair histories, the
turbocharged engines require more maintenance.
J K
Lawrence James
poster pointed out. There is the prop issue because you'll have to run a
really
high pitch for when the turbo kicks in which will make it a dog out of the
hole. You also have to deal with a water cooled exhaust system.
And heat issues. A 144 or 177 blower will give you the same boost without
any of these problems.
"Hemicuda" <jhar...@msn.com> wrote in message
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Mark Browne
"J K" <nowa...@nospam.org> wrote in message
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engine develop the same power as a much higher displacement naturally
aspirated engine.The energy normally wasted in the exhaust is use to pump
the incoming charge above normal atmosphere pressure. If you have more air,
you can burn more fuel. The nice thing about a turbo as compared to a blower
is that the amount of boost is related to the exhaust temperature, and this
is related to the amount of fuel you are burning. In practical terms, it
runs when you need it. The bottom line is that you can make a 300 cubic inch
engine deliver the same power as a 450 cubic inch engine under full
throttle, and run as efficiently as the 300 cubic inch engine when running
at lower power settings.
In automotive applications, the throttle lag means that the engine may take
a little longer to come to full power, and you have to use a "waste gate" to
prevent the turbo from stalling when you close the throttle quickly - like
in a gear shift. In most boating application these performance issues are
simply not an issue.
Properly maintained and used, a turbo is a very long life item. There is one
moving part - a single shaft with turbine and compressor fans. A turbo spins
a very high speeds - 60 to 80 thousand RPM is not uncommon. The bearings are
simple oil film in most cases. The oil provides both lubrication and
cooling. The cooling thing can be very important because the turbine is
driven by the exhaust. These bearings are the failure mechanism in
automotive application. These bearings have to get oil when the engine
starts up. In some engines the pressure builds rather slowly on startup. If
the engine is revved before the turbo is properly lubricated, a bearing
failure is in the cards. Another popular source of failure is during
shutdown. Frequently, the driver will roar up to a stop and shut the engine
off without letting the turbo bleed off the heat in the cooling oil. The
heat soaks through the housing; the oil left in the turbo breaks down and
cokes up the bearings. Sooner or later the one moving part of the turbo
quits moving because the bearings are gummed up.
Another common problem with turbos - if you build a big fire in a little
furnace, the little furnace burns up. An engine has to be build to withstand
the power developed during boost. A little known fact is that the old Dodge
slant six was originally built as a race engine. Richard Petty wanted and
engine built for turbo charging. If you look at one of these, you will
notice that the intake and exhaust all come together with a turbo would be
mounted. The other salient features was a very long stroke to extract all
the power generated, and *very* heavy main bearings. When there were using
in a naturally aspirated engine, they were not working very hard. The racing
rules of the day required that a certain number of the engines had to be in
productions automobiles to be allowed on the racetrack. The American public
got a great deal out of this - these engines have a well deserved reputation
as being unbreakable - they would keep running when they sounded like a
shaken fruit jar full of marbles. These engines are still being run in
industrial application like Lull lifts. The only reason they are not used in
automobiles today is that the design could not be tamed to burn fuel without
polluting. Rats.
Mark Browne
Hemicuda
will probably work great while cruising and at top end but will be a
dog coming out of the hole. This is a dumb question but I thought
that at slower speeds boats require less horsepower to move them
through the water. As the speed increases so does the power
requirement for a certain hull design. Is this true? If so it
appears that the low end lack of boost shouldn't kill me. Or am I
totally of base? The other thing I was thinking of was to put smaller
turbos on the engine to reduce lag but sacrifice top end boost.
Marine engines rarely go over 5,000 RPM so I could probably go with a
smallish turbine housing with a waste gate that will bring on boost
quickly and then dump the excess exhaust gas at higher speeds. I know
the heat will be a problem but I think that is manageable but I don't
want to take forever to get up on plane. Has anyone seen or ridden in
a gasoline turbo'd boat and seen how bad the hole shot was? The
reason I want to stay away from a blower is that although it will
boost power I think it will hurt the fuel efficiency. Also blowers
tend to be expensive and I can score a pair of T3 Turbos from old T
birds which would fit a 5.0 or 5.7L fairly well for cheap at a junk
yard and fabricate a set-up. Thanks for all the help and I
appreciate any more thoughts or info you could pass on!
ba...@psyber.com
: So from what I can summarize from the above posts are that the turbo
: will probably work great while cruising and at top end but will be a
: dog coming out of the hole. This is a dumb question but I thought
It wouldn't be a "dog coming out of the hole". It'd act mostlyl like a
naturally aspirated engine.
Paul
bigger prop on it to take advantage of the increased top end. But without
that power down low then the it would be overpropped until the turbo kicked
in.
<ba...@psyber.com> wrote in message
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Rick & Linda Bernard
quickly at slow speeds and still give you a good top end.
"Paul" <nom...@rogers.com> wrote in message
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Tony Thomas
Low hp will still produce this rpm but the time to do it will increase as
you lower the power. Right now you produce a certain amount of power that
allows you to turn a certain prop to 2800 rpms within a certain time. To
maintain 5000 rpms at top end with more power you will need a larger prop.
The catch is you are not producing more power at low rpms so you increase
the time required to achieve 2800 rpms.
Think of it this way. An engine without a turbo in a car will achieve a
zero to 30 mph time of say 3 seconds and a zero to 60 time in 5 seconds.
The same car with a turbo will achieve a zero to 30 mph time of 3 seconds
and a zero to 60 time of 4 seconds (boost kicks in from 30 mph up). Now if
you reduce the gear to keep rpms under redline you just increase the 0 to 30
time to 4 seconds. Just an example.
Given the hole shot problem, heat generated, and trouble to implement hosing
and stuff - I would recommend going ahead and doing the blower. Blower may
use some more fuel but since your cruising with a lower throttle setting,
you should not see much of a change.
Tony
My boats and autos - http://t.thomas.home.mchsi.com
"Hemicuda" <jhar...@msn.com> wrote in message
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jamesgangnc
You're going to fabricate water cooled exhaust to and after a pair of
turbos and you think that will be cheap and easy :-) Along with the
rest of the intake plumbing. Making a go fast boat is going to cost
you in fuel use, that is hard to avoid. And unlike cars it takes a
lot of power to make a little more speed. Just adding a blower or
turbos to your stock engine will probably kill it in pretty short
order too. You're going to want to run it at wide open throttle for
minutes at a time. This is not like a car where it is hard to keep
the throttle floored for more that a few seconds.
Just to give you an idea of what you might be in for. I went from a
stock 5.0 to a reworked 4 bolt 5.7 with all roller valve train, kb
pistons, eldebrock heads, crane cam, holley carb, and stainless marine
exhaust. Made my top end go from low 50's to mid 60's. If I make it
go any faster I'll need to go to aftermarket steering, 60's is about
all any sane person would want to do with the factory merc steering.
jamesgangnc
> There are two speed marine transmissions that should all you to build RPM's
> quickly at slow speeds and still give you a good top end.
I'm betting this guy does not have extra space between his 5.7 and
outdrive for a transmission :-)
572
also make great mufflers. Here is a good thread on a marine turbo project:
http://forums.hotboat.net/ubb/ultimatebb.php?ubb=get_topic;f=3;t=000483
Hemicuda
comes to that I will definitely go a different route. I am not
looking for absolute power in this set up but instead looking fora
viable alternative to shoving a 502 in an express cruiser. My main
goals for the project would be improve performance of a small block
without the disadvantages of big block. As to the issue of fabbing a
set-up I should be able to get all the fittings I will need and mig
them all together. The cooling issue does concern me because I don't
want to build jacketed headers but I was thinking about possibly
tracing them tubing that water is pumped through and then rapping the
piping. As long as I have enough flow through the tubing the water
should stay liquid and cool the system. Since I am looking at putting
this system on a 5,000# boat loss of accelaeration will be a big deal
because I would still like to have the functionality to use it for
water sports. I understand some of the reasoning about the
acceleration problems. Is there any slippage of the prop in the water
during acceleration. If I can get it to about 1000-1500 rpms and put
some small turbine housings on the turbos I should be into boost by
this point. The small housings will kill my top end but that
shouldn't be a problem seeing as the engine probably won't see more
than 4500 RPM. Are there any technical articles on the start-up
torque and HP requirements of boats that I could read? Thanks for the
help.
572 <n...@a.chance> wrote in message news:<bml7mv0f39gsgresr...@4ax.com>...
Mark Browne
Perhaps something like this:
http://www.amazon.com/exec/obidos/tg/detail/-/0837601606/ref=lib_rd_btb/104-0612280-0709549?v=glance&s=books
Mark Browne
Hemicuda
fundamentals of Turbo'd engines. Does Bell's really add that much?
The guys at the JYturbo forum speak higher of McInnes book. I am
looking for a little more on the hydro-dynamics of props during the
acceleration of a boat. I am familiar with pumps (my back ground is
an engineer) but I not that familiar with the specifics as they apply
to boats. I want to get some rules of thumb about how much torque and
HP are needed during boat launch so that I can make some guesses about
whether a turbo would work in the application I'm looking at. Do you
know any books concerning that subject? Thanks for the help.