When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Marine is the toughest environment for any kind of power plant you can name. Diesel is better than gas, and turbines are better than reciprocating engines. The truth of the matter is the reason there are TWO+ engines on every serious boat is the same reason that there are two+ turbofan engines on every serious aircraft. one of them is going to fail eventually, so the other one is there to get your sorry a$$ back home !!
BTW, my boater friends tell me those big Mercury inline-six, 2-stroke outboards are getting pretty reliable. You can also just keep hanging them on the fan-tail until a) you go faster than you can stand, or b) you run out of beam. Different strokes for different folks.
now you got me looking... just saw a pic w 9 x350's offset ransom on a center console...dont know if it photoshopped...or if real...ive always heard the wash on a heavy boat spins the props out on even 4 w a 9' transom... shocking if real... Jesus...
sorry all for hijacking ... wont talk about boats anymore... long live the ME !!
Do u understand what reliability means for marine engines?
I sure do. I've run a boat with a 1000 horsepower big block for more than a decade. Bebezotes bottom end failures wouldn't have been helped by having overhead cams.
Originally Posted by dcbingaman
Marine is the toughest environment for any kind of power plant you can name. Diesel is better than gas, and turbines are better than reciprocating engines. The truth of the matter is the reason there are TWO+ engines on every serious boat is the same reason that there are two+ turbofan engines on every serious aircraft. one of them is going to fail eventually, so the other one is there to get your sorry a$$ back home !!
Not really. The main reason multiple engines are used in boats is for more power and speed. It's much less expensive to use multiple engines which are based on high-volume automotive engines, than it is to design and build an engine with two to four times the displacement or power for such a low-volume market. It can be dangerous when a boat loses power, but usually it isn't. It's not like it's going to fall out of the sky or anything, like an aircraft.
Last edited by Warp Factor; 01-22-2019 at 06:07 AM.
Marine is the toughest environment for any kind of power plant you can name. Diesel is better than gas, and turbines are better than reciprocating engines. The truth of the matter is the reason there are TWO+ engines on every serious boat is the same reason that there are two+ turbofan engines on every serious aircraft. one of them is going to fail eventually, so the other one is there to get your sorry a$$ back home !!
Actually, if one engine is blowing up on an airplane, odds are the issue is taking both out. Planes have multiple engines moreso because until recently you couldn't get a plane off the ground with only one, and it is really poor for yaw if you only hang an engine off one side of the plane.
If ever there is a place where displacement and torque rule - its water. Back in the day it was also aircraft. The greatest piston engines ever made were the radial aircooled engines on the B-29. Lots of cylinders, displacement, turbos (eventually), and wait for it - pushrods. Imagine that. When it came time to carry Oppenheimer's "gadget", nobody bitched about the dozens of pushrods in those magnificent engines, because they made the engine light enough to fly and carry a 10,000 pound payload from Tinian to Japan. I rest my case.
Chalk and cheese comparison. Prop planes run between 900-2500rpm. Not a problem for pushrods. Also, the motors run at relatively constant rpms, albeit low ones.
Actually, if one engine is blowing up on an airplane, odds are the issue is taking both out. Planes have multiple engines moreso because until recently you couldn't get a plane off the ground with only one, and it is really poor for yaw if you only hang an engine off one side of the plane.
Now this is in my wheelhouse as a pilot and having spent my entire career in the commercial aviation safety business. Maybe you're talking small general aviation aircraft, BUT
1) I can't remember a case in at least 3 decades where an engine failure has taken out a 2nd engine on a transport aircraft. There are too many redundant systems guaranteeing their independence.
2) Modern turbofan engine failures are exceedingly rare. The vast majority of commercial airline pilots never see one in a 30-40 year career. Engines are so reliable that all Boeing aircraft now built have only two wing-mounted engines, and that includes the long-range B-777. These aircraft are certified to fly over the Pacific and must demonstrate the ability to fly 180 minutes (approximately 1500 miles) on a single engine to a suitable airport. That means they can fly up to 3000 mile stretches over water between suitable airports, whereas a few decades ago that required a 4-engine aircraft.
3) Even more rare is a case where an engine failure is not contained. By that I mean the case is hardened such that shrapnel does not depart the engine housing. The only recent one was last year when a piece of shrapnel hit the fuselage of a SW aircraft taking out a window, and did result in the only commercial aviation fatality in the US in a decade. However, the other engine operated normally, and no one else was hurt after a normal landing.
4) Modern aircraft fly-by-wire systems, which almost everything flying now is, compensate for the adverse yaw caused by asymmetric thrust. It's as easy to fly on a single engine as with both operating.
Sorry, couldn't help myself. I'm passionate about this stuff.
Quick. You must stop GM from making a terrible mistake.
Cadillac 4.2L BLACKWING DOHC TT motor built in Bowling Green, KY.
GM is gonna do what they're gonna do. They've already made two V8 overhead cam engines, both discontinued, and both superseded by more powerful pushrod engines.
One thing easily noticeable is the high center of mass in that engine. Probably OK for a boulevard Cadillac, but not the best thing for a track or sports car. However, that is to be one of the engines in the mid-engine C8, and the only one I know about so far. Maybe they're chasing fuel economy, since turbocharged small displacement engines can offer that, if the boost doesn't get so high that the static compression ratio needs to be really low. 500 horsepower would probably be fine, for the base C8. Later higher-performance variants will probably need to do something different. But the "standard" Corvettes have always had the most sales, so an engine like that might contribute a lot to the fuel economy of the Corvette segment.
Later higher-performance variants will probably need to do something different. But the "standard" Corvettes have always had the most sales, so an engine like that might contribute a lot to the fuel economy of the Corvette segment.
I'd be terribly surprised if we don't also see a Cadillac-skinned ME car coming out of BG in the near future. Like the XLR that (poorly) preceded it, it'll probably shun the OHV engine in favor of a "smooth OHC" one. Because: marketing. Not performance.
How can u possibly say this "One thing easily noticeable is the high center of mass in that engine. Probably OK for a boulevard Cadillac, but not the best thing for a track or sports car." and then justify accepting the new LT5 on the basis of "not being too tall or top heavy? At least the DOHC are in a much lower location than that blower.
Last edited by Dominic Sorresso; 01-22-2019 at 01:42 PM.
I honestly don't have any idea how significant, if at all, the higher CG would be. It may be near round-off error, but a DOHC most certainly has a higher CG than the LT. I also think it could be easily compensated for in other ways.
I was simply responding to the picture of the LT5 that appeared to be of similar height to the 4.2 DOHC.
Sorry, couldn't help myself. I'm passionate about this stuff.
No problem! I'd argue that both are exceedingly rare events.
As far as yaw, that was more from an engineering standpoint. How do you design a commercial jetliner with a big enough single engine? Yes, I'm aware of ETOPS requirements that would never allow it, but other than something like a DC11 with it stuck in the tail (a much smaller engine than required), I'm not sure of a great way to handle the engineering without using considerable living/cargo space, all single jet engine aircraft stick it right in the fuselage. Even if you CAN manage thrust on one side of the aircraft only, it is still a poor engineering method to not balance it and by design requiring extensive intervention to keep it straight.
Then again, I remember from when I was put through ground school for work that the instructor was insistent on the only bigger problem than a novice pilot losing an engine in a single engine plane was a novice pilot losing an engine in a double engine plane
Yep, that's still a general aviation problem, but not an issue on modern commercial aircraft with fly-by-wire advanced tech and flight envelope protection systems. Think of it as a very sophisticated stability control system in modern automobiles. The type of GA aircraft flown by hobby pilots don't have such systems, and think of them as old school cars.
No one puts an engine in the tail anymore or even at the rear of the fuselage on 100-seat or greater airline type aircraft. The DC10/MD11 family is a 40+ year old design and long retired from passenger service. Airliners today are all 2 large engines hung on the wing. Corporate jets are the exception because of their small size, it's less feasible to hang engines on the wing.
A single engine commercial, passenger aircraft would not be certifiable under Federal Aviation Regulations. That's independent of ETOPs regs, which was about allowing twin-engine aircraft to operate on long-range, over-water routes previously only allowed under the regs with 3-4 engines. That rule change became possible because of the dramatic improvement in turbofan reliability over time.
GM is gonna do what they're gonna do. They've already made two V8 overhead cam engines, both discontinued, and both superseded by more powerful pushrod engines.
One thing easily noticeable is the high center of mass in that engine. Probably OK for a boulevard Cadillac, but not the best thing for a track or sports car. However, that is to be one of the engines in the mid-engine C8, and the only one I know about so far. Maybe they're chasing fuel economy, since turbocharged small displacement engines can offer that, if the boost doesn't get so high that the static compression ratio needs to be really low. 500 horsepower would probably be fine, for the base C8. Later higher-performance variants will probably need to do something different. But the "standard" Corvettes have always had the most sales, so an engine like that might contribute a lot to the fuel economy of the Corvette segment.
Do you have inside info on the Blackwing being destined for the C8 or is that just a guess based on public info?
I am speculating that the difference between the Cadillac BW and one of the LTx motors for the Corvette ME will be the HotV for the Caddy while the Vette will go w a more traditional configuration of intake in the V and exhaust on the exterior of the motor. Additionally cam profile and calibrations will differ. So the cylinder heads will differ but use the same short block.
I am speculating that the difference between the Cadillac BW and one of the LTx motors for the Corvette ME will be the HotV for the Caddy while the Vette will go w a more traditional configuration of intake in the V and exhaust on the exterior of the motor. Additionally cam profile and calibrations will differ. So the cylinder heads will differ but use the same short block.
Seems likely. One or two small changes and the engine gets a different code which allows the Cadillac statement to remain true while still putting the “same” engine in the c8.
Quick. You must stop GM from making a terrible mistake.
Cadillac 4.2L BLACKWING DOHC TT motor built in Bowling Green, KY.
You're still around? Im still waiting for you to stop deflecting and dodging and actually reply to my posts, but I think we both know why you arn't replying...
I wouldn't be too surprised to see GM use the blackwing in the Corvette, as that is what the rumors have been for a while now. It seems GM is trying to attract bench racers stuck in the 90s like yourself, we'll see how well that works though. Its only a matter of time before they go with a camless drivetrain and then full electric soon enough.
01-22-2019, 02:12 AM
