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Banks Sequential Super Turbo Marine diesel engine

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Old 02-11-2010, 07:45 PM
  #31
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Jass - I will tell you, you are wrong. With the multispeeds you will run a higher gear ratio and a smaller dia prop, you will go faster. You don't have enough low rpm hp to get the boat on plane with the taller gears, the multispeed will allow you to do, but the reason for them is for top end, higher prop speed and not so much drag style acceleration from a dead stop as much as out of a corner. That 75 mph number is your limit due to prop speed and nothing else. Take the max rpm's of your gas boat divide by the gear ratio and you have prop speed. You will see it is higher than your diesel prop speed, you can not totally compensate for prop speed with more dia and/or pitch. If you double the Hp


Joe give me a very rough idea.. approx how much faster would I be going.. 5mph, maybe 10...I KNOW YOU NEED MORE INFO..BUT AMUSE ME..

thanks Jeff
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Old 02-11-2010, 08:59 PM
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Jeff, I amuse myself most of all!!! (I'm not a naval engineer or prop master, I guess at speeds based on experience and test data regarding how much of our useable Hp we could apply to the water, we built engines and engine parts, boats were just another platform like a dyno to test engines on)

I can tell you this, a true 360hp being used on a 40' SH loaded with lead so it weighed 15-16,000 lbs was 65 mph.

The 38' Ebel with 600hp runs 92-94 mph (we would hit the governor not run out of Hp. Put larger props on and you could not get on plane - remember single speed trans then)

Todays hulls are faster, lighter in general steps etc., props are so much better, I would guess your 480's have to put you into the low 80's?

You need 600hp to run how fast you want to cruise. My point is that even with that extra Hp without the taller gears you won't go fast enough because the prop speed limits you.

I have a question for you, whatever boat your talking about how fast will it go with 500hp gas engines?


ps - in reference to the Ebel 38' (SH#38), when we changed engines to big twin turbos 850-900 hp each we did not change gears just props you would expect the boat to go like hell now??? it ran 102 mph but accelerated so hard it would push you back in the bolster. Again, the limits were gears. When the Gancia was repowered with big engines it had much taller gears than we had on the Ebel, the Gancia in freshwater (Lake Como), high alt ran 114-116 mph and had plenty Hp left, the boat could not run faster.

Last edited by HabanaJoe; 02-11-2010 at 09:04 PM.
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Old 02-11-2010, 09:28 PM
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Originally Posted by Catmando View Post
Well Joe I tried calling Mr. Banks today...no luck. If you can talk to someone in the Marine office at Banks maybe they can shed some light on the torque/rpm issue. I couldn't get through to them.
What are you going to do ask him for a set for your make believe boat?? I'm sure he's real excited in taking out part of his day to waste it on some free loader..
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Old 02-11-2010, 11:00 PM
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Pat
When you put a multispeed behind a big engine are the ratios both under and over?

How does the drive like the low ratio with full throttle..ouch!
We run our splits and ratios where we want them. None of the gears are direct.

The drive suffers with low rpm and high torque but when you build them like we do it is not an issue.

Joe is right about the props and ratios and speed etc.... Most of the engines do not make the power they are rated at also so be careful.

pat W
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Old 02-11-2010, 11:44 PM
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thanks Pat!
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Old 02-12-2010, 01:36 AM
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What are you going to do ask him for a set for your make believe boat?? I'm sure he's real excited in taking out part of his day to waste it on some free loader..
Remember what Cheney told Senator Leahy? How bout you go and do that.
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Old 02-12-2010, 06:31 AM
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Jo

Whats the story on the back pressure befoe the turbo?
I've never worked on custom diesels so never measured it, temp yes but pressure no.
How much are we talking to open a valve against the spring?

Re the new Merc manifold, I would guess the 2 passages are to run to the turbo that has a split pulse exhaust housing on it to help improve the low end.
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Old 02-12-2010, 08:53 AM
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powerabout -

the merc manifold, absolutely they are using an axial divided houseing and turbo. If you remember in truck terms Cummins started that inconjunction with Holset to make a "pulse tuned" manifold to help get lower rpm toruque to combat the fact that the Cat 3406 had variable pump timing which a Cummins did not. Truckers always said the Cat pulled better at lower rpms, not because of the engine but because of fuel pump timing like advance on a distributor. My point was more against the people that try to use a traditional log manifold and say "I have a performance diesel".

Exhuast back pressure in the manifold is on every turbo charged engine, you can't spin the turbo without pressure. I'll explain it this way, as the exhaust starts to spin the turbo the compressor makes boost. As the boost pressure goes up the resistance on the turbine side has to go up because the compressor does not want to compress air, it is forced to that creates pressure in the manifold.

The reason they invented waste gates was not to control boost. Pop off valves control boost, look at lod Indy cars or F-1's. The problem was exhaust pressure would get to be greater than intake pressure, when the valve are in overlap the exhuast would push intake air back out of the cylinder thus reduceing the amount of fresh air to burn. You see this on a dyno very clearly, the engine will get flat on power and smoke will increase like crazy and for no other reason than the engine starting to run very rich it will make some more power but efficientcy will drop to nothing.

Your question about how much pressure? Hot rod diesels like our old ones, Seateks back in the day would run 40-50psi of boost. (I've had tractor pull engines into the 70's but that is like a Top Fuel car, no cooling, solid heads etc.) Take the area of backside of a valve 2 sq inches??? 50 psi x 2 inches is 100 pounds of push to unseat the valve, right? You need 100lb of valve spring just to keep the valve from being open all the time.

You take your blower (supercharged) engines and they all exhaust into open atomsphere, you only need enough spring to keep the on the cam, there is no offset from positive pressure.

Go online and look for pictures of Top Fuel cars engines the intake springs are huge compared to exhaust springs why the boost wants to open them!
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Old 02-12-2010, 09:13 AM
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simple answer pboat,
emp's exhaust manifold pressure,for stockers and mildly tune diesel's,the ratio of intake pressure to exhaust pressure is 2 to 1(or more) meaning 1lb of boost intake = 2lbs in exhaust.its the design of exhaust manifold and the size of the exhaust's turbine wheel thyat dictate emp's.
so its very easy in a d-max to have 60psi emp's for 30psi of intake charge.
thats why we try to size turbo exhaust to reduce that ratio to 1.5 or less to 1.lots of experimentation to say the least,because bigger may be better but you'll take a day to spool the turbo,that sucks too

Last edited by sutphen 30; 02-12-2010 at 09:15 AM.
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Old 02-12-2010, 10:52 AM
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Thanks Joe/Sutphen

You mentioned how much boost you were running but how much pressure between the ex valve and turbo?
Are we saying like Sutphen that its common to have a 2:1 ratio so you had 80 to 100psi in the manifold?
I never knew that about the exhaust pressure overcoming the inlet and as you say with fuel injection you would certainly notice that getting rich.
Adds another dimention to the fact that on a big pressure turbo'd engine the inlet stroke is a power stroke...built in EGR.

I guess the exhaust valve would get a bit angry not being seated and getting warmed twice by the same hot gas
Time for desmodronic valve gear

Now I need to start thinking about whats happening in a compound turbo engine as in one turbo feeds into another.
Like the old 855 Cummins gen sets.

Cheers

Last edited by powerabout; 02-12-2010 at 10:56 AM.
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