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Diesels for boats

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Old 04-19-2008, 03:36 PM
  #111
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Ding ! Ding! Ding! Ding! We have a winner. Njawb is now officially the most condecending person on OSO.
Wow man, lighten up.




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Old 04-19-2008, 03:36 PM
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V vs L redux

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Originally Posted by Njawb View Post
There goes that presumption again, Joe.

I get more excited about the idea of a marinized Audi V12 TDI than the existing QSB 5.9 not because it is as familiar as a gas, pushrod V8 (which, in truth, it is not at all), but because such an engine would have the same or better performance than the QSB while coming in a package size between a SBC and a BBC, and weighing about the same as a BBC. Yes, the bigger, heavier Cummins may well be more durable, but the Audi in SUV trim is by no means a high-strung, high-maintenance, race-only engine. On the contrary, physically smaller and lighter, automobile-based diesels (many of them V engines) will be a better fit to many performance marine applications, even if I6's continue to dominate the trucking industry.
It's all basic stuff dude. Diesels are compression ignition. That requires longer strokes with stronger pistons and rotating assemblies. This all translates to more weight. More weight spinning on a crank means more drastic harmonics. A 120 degree crank will out perform a 90 degree crank any day of the week. Proven by real world performance. V-8 bad! V-12 or L6 good! Now we get get to the V-12 vs L-6 thing. The Bean Bag explanation covers that. To a point! there is a tipping point where the V-12 out performs the L-6. Lets go back to those trailers and change some parameters. Lets make the bags a 150 lbs and its 12 adults vs 6 asian elephants. The two man teams will out perform the elephants as far as speed in unloading is concerned. The tipping point for diesel engines is about 15L displacement. At 85 PS per liter that Audi engine is no slouch. The Banks tuned QSB is hitting a 124 hp per liter. There are older 6-BT engines in sled competition hitting a 169 hp per liter. Cummins is still on the fence about releasing the QSB-600. Thats a production marine engine that puts out 101 hp per liter. That Audi engine is an engineering marvel. But its near it's peak out of the box. There isn't very much room to tweak some more go fast out of it. But remember the QSB is no technological slouch. It was using the same fuel delivery system as the Audi while the Audi was still on the drawing board. The Banks tuned QSB uses a VGT turbo like the Audi albeit a different design. Also remember this. The L vs V argument is the same for gasoline engines too!
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Old 04-19-2008, 03:48 PM
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I give up!!!!!

You talk tech all you want, when you bring something to market I wish you luck and hope it sells and don't have warranty issues etc and make money at it.

I thought we can chat on here without going legal about taking phrases that imply "all" that are said in spirit not literally to make a point. I know I should say things like majority or most and not imply all - I come here to engage in light hearted dialogue about things that I enjoy and ignor my wife and kids for at least 5 minutes!!

So.

Yes, I am stupid and when I imply "All" I mean every last A-hole on the planet!!!

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Old 04-19-2008, 04:05 PM
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I don't know why you guys are getting so hung up on inline vs. V-engine diesels. It turns out for most long haul trucks, the inline 6 is a good sized package at a reasonable cost. However, Cummins, Detroit Diesel, Cat, and others have all built V8 HD diesels, usually in larger displacements. For light trucks, the V-engine is easier to package because it's shorter, hence, the popularity there.

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Old 04-19-2008, 04:35 PM
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Originally Posted by DMOORE View Post
Ding ! Ding! Ding! Ding! We have a winner. Njawb is now officially the most condecending person on OSO.
Wow man, lighten up.
Lighten up yourself, man. I am not condescending to Joe. Rather, I am objecting to his condescension in presuming to tell me why I think the potential for marine diesel V engines is exciting. In point of fact, I am far more interested in his telling me what he thinks about high-performance marine diesels (which is usually highly informative and useful) than in his trying to tell me what I (or anyone else) think about those engines.

Last edited by Njawb; 04-19-2008 at 04:43 PM.
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Old 04-19-2008, 05:09 PM
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A 120 degree crank will out perform a 90 degree crank any day of the week. Proven by real world performance. V-8 bad! V-12 or L6 good!
Could you explain your thinking a bit more? I can understand the main bearing support argument, but this harmonics argument makes little to no sense to me. Yes, an I6 or V12 has inherently low primary and secondary harmonics, but so does a fully counterweighted, cross-plane V8. Counterweighting is a problem if you want a quick responding, high revving engine, but that hardly describes the typical diesel.
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Old 04-19-2008, 06:36 PM
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The "E" word

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Originally Posted by Njawb View Post
Could you explain your thinking a bit more? I can understand the main bearing support argument, but this harmonics argument makes little to no sense to me. Yes, an I6 or V12 has inherently low primary and secondary harmonics, but so does a fully counterweighted, cross-plane V8. Counterweighting is a problem if you want a quick responding, high revving engine, but that hardly describes the typical diesel.
My point is not something I thought up. My points are based experience. I'm still a young buck even though I just turned the 1/2 century corner. Back in the day there was more than one hot rodder that had a hopped up V-8 that got the stink stomped out of him by a grocery getter with a slant 6. Out in the 3d world go fast boats Big Block Chevys get stomped regularly by junkyard dog L-6 Nissans. You need a Chevy Big Block 8.9L or bigger to get 500 hp. Or 56 hp per liter. A used Nissan RB-26 long block with a better turbo and fuel delivery set up will give you an easy 500 hp. Thats 192 hp per liter. If you have money the old boys down in Omori will sell you one blueprinted and tuned to a 1000 hp. Thats 384 hp per liter. An 8.9L BBC would have to put out over 3000 hp to match that. The V-8 was pushed onto the American public because it sounded more marketable.
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Old 04-19-2008, 08:23 PM
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Harmonics?
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Old 04-19-2008, 10:51 PM
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The V-8 was pushed onto the American public because it sounded more marketable.
When it gets to the point of conspiracy theories, I think discussion is pretty much beyond hope. Why would someone want a V8 engine when they are compact, lightweight, have excellent rigidity, are smooth, powerful, look good under the hood, and sound great? We sure are a bunch of morons to fall for that marketing.

Michael

Last edited by Michael1; 04-20-2008 at 01:38 AM.
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Old 04-20-2008, 03:02 AM
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Originally Posted by 29Firefox View Post
My point is not something I thought up. My points are based experience. I'm still a young buck even though I just turned the 1/2 century corner. Back in the day there was more than one hot rodder that had a hopped up V-8 that got the stink stomped out of him by a grocery getter with a slant 6. Out in the 3d world go fast boats Big Block Chevys get stomped regularly by junkyard dog L-6 Nissans. You need a Chevy Big Block 8.9L or bigger to get 500 hp. Or 56 hp per liter. A used Nissan RB-26 long block with a better turbo and fuel delivery set up will give you an easy 500 hp. Thats 192 hp per liter. If you have money the old boys down in Omori will sell you one blueprinted and tuned to a 1000 hp. Thats 384 hp per liter. An 8.9L BBC would have to put out over 3000 hp to match that. The V-8 was pushed onto the American public because it sounded more marketable.
Firefox ,in most of your posts you are comparing engines to totally different engine,s ,,,,why ?
A big block chevy can put out 100 hp /litre naturally aspirated
when the proper parts are used ,and 7000 hp when topfuel is used ( 500 ci) that 875 hp /litre (I know this is no comparison)

that 2,6 L Nissan can put out 1000 hp with a big turbo,but only if you spend big $$ on a bottem end and ring/studding the head,if not its a ticking time bom ,you have to use racing fuel to keep the engine from destructing itself ,and or cool things down with water /meth etc
A big block 8 litre used for dragracing with turbo,s /blower can put out the same hp/litre if the bottem is reinforced and ringing the head



The more air is been pumped in ,the more power the engine makes ( if supplied by fuel)
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