Turbocharging a Marine Engine
Has anyone tried turbocharging a 5.0 L or 5.7 L Merc engine in this
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! |
Turbocharging a Marine Engine
I think your missing the fact of turbo lag.
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" wrote in message om... Has anyone tried turbocharging a 5.0 L or 5.7 L Merc engine in this 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! |
Turbocharging a Marine Engine
It's quite common to turbocharge Grand National ski race boats. Usually two of 'em. b. |
Turbocharging a Marine Engine
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. |
Turbocharging a Marine Engine
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Turbocharging a Marine Engine
good for efficiency and engine life.
From what I've read in automotive repair histories, the turbocharged engines require more maintenance. J K |
Turbocharging a Marine Engine
You're far better off with a blower. Turbos have a lag problem as another
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" wrote in message om... Has anyone tried turbocharging a 5.0 L or 5.7 L Merc engine in this 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! |
Turbocharging a Marine Engine
"J K" wrote in message . 201... good for efficiency and engine life. From what I've read in automotive repair histories, the turbocharged engines require more maintenance. J K Turbo-charging allows an engine to pack in move air and fuel, making the 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 |
Turbocharging a Marine Engine
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 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! |
Turbocharging a Marine Engine
I think the "dog coming out of the hole" comment was based on putting a
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. wrote in message ... Hemicuda wrote: : 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. |
Turbocharging a Marine Engine
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. "Paul" wrote in message able.rogers.com... I think the "dog coming out of the hole" comment was based on putting a 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. wrote in message ... Hemicuda wrote: : 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. |
Turbocharging a Marine Engine
Most boats have to achieve about 2800 rpms to plane off and start moving.
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" wrote in message om... 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 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! |
Turbocharging a Marine Engine
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Turbocharging a Marine Engine
"Rick & Linda Bernard" wrote in message ...
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 :-) "Paul" wrote in message able.rogers.com... I think the "dog coming out of the hole" comment was based on putting a 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. wrote in message ... Hemicuda wrote: : 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. |
Turbocharging a Marine Engine
Turbos work well in marine applications, one of the side benefits is that they
also make great mufflers. Here is a good thread on a marine turbo project: http://forums.hotboat.net/ubb/ultima...c;f=3;t=000483 |
Turbocharging a Marine Engine
Thanks for all the comments. A marine trans is not an option so if it
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 wrote in message . .. Turbos work well in marine applications, one of the side benefits is that they also make great mufflers. Here is a good thread on a marine turbo project: http://forums.hotboat.net/ubb/ultima...c;f=3;t=000483 |
Turbocharging a Marine Engine
"Hemicuda" wrote in message om... Thanks for all the comments. A marine trans is not an option so if it 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 wrote in message . .. Turbos work well in marine applications, one of the side benefits is that they also make great mufflers. Here is a good thread on a marine turbo project: http://forums.hotboat.net/ubb/ultima...c;f=3;t=000483 Perhaps something like this: http://www.amazon.com/exec/obidos/tg...glance&s=books Mark Browne |
Turbocharging a Marine Engine
I already have Hugh McInnes book which is really solid on the
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. Perhaps something like this: http://www.amazon.com/exec/obidos/tg...glance&s=books Mark Browne |
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