torque V12
12-05-2003, 05:11 PM
#31
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Not exactly linear. That was my point. How close to linear depends on setup characteristics. But the main idea is to say that not only turbos are affected by the so called "lag". Some superchargers are also affected by this phenomenon, even though it's reduced to a minimum... Besides, I don't know which setup you have experience with but if it's whipple, they are not the type which would exhibit this "lag" or unlinear realtionship between boost and RPM. As for noise comments about diesels, there is not much I can say in their defense. It's not bad if you like the industrial sound of trucks but it will never equal the roar of a big block V8. As for the smell, diesels are getting better. With modifications to the turbocharging system and injection improvements such as EFI, common rail or direct injection, smoke is reduced to a minimum. If you also have underwater exhausts, the only thing you will find is some sooth on your transom. But it is so with gas V8s as well.
And I hope you guys are kidding about industrial as being the main application for the Torque V12. That would break my heart. As I said in another thread, I always wanted to see what triple Torque SCs would do in boats I'm building. I really think 160 would fall...
And I hope you guys are kidding about industrial as being the main application for the Torque V12. That would break my heart. As I said in another thread, I always wanted to see what triple Torque SCs would do in boats I'm building. I really think 160 would fall...
12-05-2003, 08:26 PM
#32
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As marc pointed out, positive displacement superchargers put out very close to max boost at any speed over idle. If they put out 10psi at 6000, then they'll put out very close to 10psi at 1500rpm - not the relationship you expressed. It is th emechanical nature of positive displacement blowers (and why ther have that name) that they pump a given volume of air with each rotation ( up to the pressure within their design spec). Be aware that we are talking about boost pressure with the throttle open (because otherwise you aren't reading what the compressor is capable of, only what it is doing under part throttle conditions).
And Honda did not have the first production 4-valve per cylinder engine (I know you said they were only "among the first"). Chevrolet had one in 1974 with the Cosworth Vega. If you want to exclude the Cosworth from the running due to its limited production status, then Mercedes beat Honda with the 1983 190E. This doesn't even mention the other early 70's cars like Jensen Healys and such. And Honda doesn't "do" production 5-valve motors - only a few race ones. And, also, Honda has no current DOHC marine motors, only SOHC. Suzuki is the tech leader in gizmos on outboards...
Honda trailed Mercedes in variable valve timing, as well, coming in 2 years behind the 2001 SL, and moving thru the entire range of Benz V8's by 1992.
And variable valve lift? Cadillac, 1981 (yeah, I know it didn't work very well).
(ALL of these advances were pioneered by aircraft and racing engine gurus in the 1915 to 1945 range)
What's different about my discussion of Honda (and others') new marine motors versus your mention of BMW? Simple. I am talking about motors designed from the ground up for a marine environment, not a marinized high revving performance automobile. You were extolling the virtues of the Bimmer, specifically. You didn't say "Wow this Bimmer motor AND THE NEW 4 STROKE OUTBOARDS would be great new boat motors". There is where I claim to see a difference. If you were expecting us to "fill in the blanks there" then I regret that I was not insightful enough to understand to do so.
496 won't cut it on a patrol boat, eh? Wouldn't by any chance be a misapplication of the motor would it? How do you feel that your BMW motor would work there? Or maybe you feel that an S2000 motor would live at it's power peak (7700 rpm) for 50 hours. My guess is that your patrol boat has improperly sized heat exchangers and/or propping for the application.
I'm confident you are familiar with the output classifications for diesel engines. You of all people, should recognize that a pleasure craft (class E) motor is tuned to provide higher power output, albeit for shorter WOT periods with adequate "resting time". A Class C motor is designed from the same basic envelope to provide a lesser power output but at higher percentages of WOT operation. A Class A diesel is designed to primarily run full throttle for months at a time without being shut off or unloaded.
The patrol boat application you speak of is definitely NOT a Class E Pleasure Craft application. It MIGHT be a Class C "Maximum Continuous" Application. Or It might be a Class B "Heavy Duty" Application. It is DEFINITELY NOT a Class E High Performance Pleasure Craft application.
The 496 you make mention of is a Class E crossreference. Sorry if it isn't holding up. Somebody needs to pony up for some true Commercial Duty motors for those patrol boats.
And Diesels are indeed my preferred choice of power in a heavy boat. But you gotta pay for them and the marine pleasurecraft industry has learned by experience that the consumer will choose the cheaper motor every time when the top speeds are comparable - and it doesn't matter if its lifespan is drastically reduced over the more expensive choice.
I guess it's the same reason China is doing so well in the world marketplace. Quality and longevity be damned - I want the cheaper one.
I still say that the mass-market American performance boating community won't pay a penny more for something "exotic and better" unless it will stomp the holy britches off an HP500EFI. And I don't think there's any current basis on the market for a marine motor that can outwrangle the blue Merc (or for the money, the 496, unless it is grossly misapplied).
And Honda did not have the first production 4-valve per cylinder engine (I know you said they were only "among the first"). Chevrolet had one in 1974 with the Cosworth Vega. If you want to exclude the Cosworth from the running due to its limited production status, then Mercedes beat Honda with the 1983 190E. This doesn't even mention the other early 70's cars like Jensen Healys and such. And Honda doesn't "do" production 5-valve motors - only a few race ones. And, also, Honda has no current DOHC marine motors, only SOHC. Suzuki is the tech leader in gizmos on outboards...
Honda trailed Mercedes in variable valve timing, as well, coming in 2 years behind the 2001 SL, and moving thru the entire range of Benz V8's by 1992.
And variable valve lift? Cadillac, 1981 (yeah, I know it didn't work very well).
(ALL of these advances were pioneered by aircraft and racing engine gurus in the 1915 to 1945 range)
What's different about my discussion of Honda (and others') new marine motors versus your mention of BMW? Simple. I am talking about motors designed from the ground up for a marine environment, not a marinized high revving performance automobile. You were extolling the virtues of the Bimmer, specifically. You didn't say "Wow this Bimmer motor AND THE NEW 4 STROKE OUTBOARDS would be great new boat motors". There is where I claim to see a difference. If you were expecting us to "fill in the blanks there" then I regret that I was not insightful enough to understand to do so.
496 won't cut it on a patrol boat, eh? Wouldn't by any chance be a misapplication of the motor would it? How do you feel that your BMW motor would work there? Or maybe you feel that an S2000 motor would live at it's power peak (7700 rpm) for 50 hours. My guess is that your patrol boat has improperly sized heat exchangers and/or propping for the application.
I'm confident you are familiar with the output classifications for diesel engines. You of all people, should recognize that a pleasure craft (class E) motor is tuned to provide higher power output, albeit for shorter WOT periods with adequate "resting time". A Class C motor is designed from the same basic envelope to provide a lesser power output but at higher percentages of WOT operation. A Class A diesel is designed to primarily run full throttle for months at a time without being shut off or unloaded.
The patrol boat application you speak of is definitely NOT a Class E Pleasure Craft application. It MIGHT be a Class C "Maximum Continuous" Application. Or It might be a Class B "Heavy Duty" Application. It is DEFINITELY NOT a Class E High Performance Pleasure Craft application.
The 496 you make mention of is a Class E crossreference. Sorry if it isn't holding up. Somebody needs to pony up for some true Commercial Duty motors for those patrol boats.
And Diesels are indeed my preferred choice of power in a heavy boat. But you gotta pay for them and the marine pleasurecraft industry has learned by experience that the consumer will choose the cheaper motor every time when the top speeds are comparable - and it doesn't matter if its lifespan is drastically reduced over the more expensive choice.
I guess it's the same reason China is doing so well in the world marketplace. Quality and longevity be damned - I want the cheaper one.
I still say that the mass-market American performance boating community won't pay a penny more for something "exotic and better" unless it will stomp the holy britches off an HP500EFI. And I don't think there's any current basis on the market for a marine motor that can outwrangle the blue Merc (or for the money, the 496, unless it is grossly misapplied).
Last edited by mcollinstn; 12-05-2003 at 09:02 PM.
12-06-2003, 05:03 AM
#33
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Mccollinstn, I was referring to centrifugal superchargers when talking about boost presure "lag" or the unlinear relationship between boost and RPM. I stated that the positive-displacement superchargers like the Lysholm, Eaton, Roots types of which Whipple chargers are an example I believe, do not exhibit this characteristic. The airflow is roughly linear to RPM meaning that boost pressure is fairly constant. That's what I meant to say: just distinguish between centrifugal and positive-displacement superchargers...
As for engines, I agree with you again. A clean sheet engine designed for marine applications will always be better than a marinized automotive block. However, pure marine engines are very rare so I was just wondering how well a BMW would do. If there are so few true marine engines around, you have to start thinking about the next best thing: marinized engines and that's what I was doing. The opinion remains the same though and I think we both agree: marine engines, marinized or designed for this purpose, would be much better if modern technologies were applied to them. Sure, it would be great if BMW took a clean sheet of paper and made a big block marine engine but for the lack of it, you have to wonder what a marinized one would do. I believe it would be an extremely good engine. Afterall, it did win two Class 2 championships... Once again, what Suzuki or Honda are doing may be a better example but I think the message remains the same: a marine engine with DOHC, 4 valves per cylinder, variable valve timing and adequate displacement for torque would be more powerful, more reliable, more economical and cleaner for the environment. So I guess we agree on that one, no?
You actually seem to go further in your call for a modernization of marine engines by saying that a clean sheet design for a purely marine engine is needed. Economic realities impose other priorities. Automotive market is bigger and so a great majority of engines will be designed for this application and then marinized. Combined with the fact that they were tinkering with the idea in coop with Victory Team, this is why I tought about BMW. But sure, there are better examples like Yanmar, Seatek and others who design their marine engines from zero... Although I believe Honda use their automotive blocks as a base for their engines, at least on certain models.
As for the 496HO, once again you're right but the simple reality is that I have no other choice. Patrol boats are a very difficult market where even though a heavy-duty rated engine version would be approprite, clients usually demand a light-duty version because it is more powerful and they need speed, even if it means problems every 50 hours. So faced with this reality, I think that an engine with modern technologies in application would do a better job indeed. The problem is that we need to rev the GM big blocks at approx. 5000 RPM to get the power and decent top end and this type of engine is not originally intended to rev that high. A high-tech modern engine, even a marinized one, would cope better with this kind of revving. And by that virtue alone, it would be a better solution. Yes, a 4.4 V8 would have a hard time because it is too small and it would not have the torque to cope with 20 000+ lb. Which brings us to your point that original designs for marine use are a better solution. Now if only BMW could design an 8.2 liter or why not a 10 liter or so engine with all its technology for marine applications. Would it be better than a 496HO? Yes, no doubt. Would it cost more? Surely but guys who buy patrol boats don't care. And with time, this would also become affordable just like Honda and Suzuki outboards came progresively down to earth in terms of pricing.
As for engines, I agree with you again. A clean sheet engine designed for marine applications will always be better than a marinized automotive block. However, pure marine engines are very rare so I was just wondering how well a BMW would do. If there are so few true marine engines around, you have to start thinking about the next best thing: marinized engines and that's what I was doing. The opinion remains the same though and I think we both agree: marine engines, marinized or designed for this purpose, would be much better if modern technologies were applied to them. Sure, it would be great if BMW took a clean sheet of paper and made a big block marine engine but for the lack of it, you have to wonder what a marinized one would do. I believe it would be an extremely good engine. Afterall, it did win two Class 2 championships... Once again, what Suzuki or Honda are doing may be a better example but I think the message remains the same: a marine engine with DOHC, 4 valves per cylinder, variable valve timing and adequate displacement for torque would be more powerful, more reliable, more economical and cleaner for the environment. So I guess we agree on that one, no?
You actually seem to go further in your call for a modernization of marine engines by saying that a clean sheet design for a purely marine engine is needed. Economic realities impose other priorities. Automotive market is bigger and so a great majority of engines will be designed for this application and then marinized. Combined with the fact that they were tinkering with the idea in coop with Victory Team, this is why I tought about BMW. But sure, there are better examples like Yanmar, Seatek and others who design their marine engines from zero... Although I believe Honda use their automotive blocks as a base for their engines, at least on certain models.
As for the 496HO, once again you're right but the simple reality is that I have no other choice. Patrol boats are a very difficult market where even though a heavy-duty rated engine version would be approprite, clients usually demand a light-duty version because it is more powerful and they need speed, even if it means problems every 50 hours. So faced with this reality, I think that an engine with modern technologies in application would do a better job indeed. The problem is that we need to rev the GM big blocks at approx. 5000 RPM to get the power and decent top end and this type of engine is not originally intended to rev that high. A high-tech modern engine, even a marinized one, would cope better with this kind of revving. And by that virtue alone, it would be a better solution. Yes, a 4.4 V8 would have a hard time because it is too small and it would not have the torque to cope with 20 000+ lb. Which brings us to your point that original designs for marine use are a better solution. Now if only BMW could design an 8.2 liter or why not a 10 liter or so engine with all its technology for marine applications. Would it be better than a 496HO? Yes, no doubt. Would it cost more? Surely but guys who buy patrol boats don't care. And with time, this would also become affordable just like Honda and Suzuki outboards came progresively down to earth in terms of pricing.
12-06-2003, 05:45 AM
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BTW, I now see what you mean by saying that the boost is very close to max anywhere above idle. I was thinking about boost at a given throttle position, not necessarily open. While it's true that in this case you're not judging the pure performance of the supercharger itself, they are bolted to an engine and the engine is used the way it's used, not necessarily with throttle open all the time. I guess it's a different definition of supercharger performance, but you're right. Thanks for the clarification...
12-06-2003, 11:08 AM
#37
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Thanks Lucy, same here but not enough time in KW.
termoli, from a practical standpoint any of the belt driven (including centrifugal) blowers deliver pretty constant full throttle boost levels within the useful RPM range of the engine.
termoli, from a practical standpoint any of the belt driven (including centrifugal) blowers deliver pretty constant full throttle boost levels within the useful RPM range of the engine.
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