I don't disagree with that statement, but the increase in VE is a secondary effect from an increased CR. Increased thermal efficiency and BMEP are directly improved by increased CR.Originally Posted by leo13
I don't disagree with that statement, but the increase in VE is a secondary effect from an increased CR. Increased thermal efficiency and BMEP are directly improved by increased CR.
The intake cams being driven in the middle (technically, lower middle) actually seems like a good thing to me. Less length for the angular deflection to add up over.
I have no first hand knowledge of these details, but I would not assume that the output is fixed and there is no room to improve.
There is fair amount of strain on the first length of the exhaust cam. Neither design is perfect.
The output is fixed, outboards are defined by their HP. If the series/form factor has a ceiling of 300hp then it is in the manufactures best interest to design to that limit. Auto engines are not limited and many are designed to have the output increased with minimal re-engineering. My original opinion was that this design is compact and light because it was designed for this specific output. It is not over built to say the least and will not mod well. We are off on major tangent which is not fair to the OP.
These engines (and the G2 as well) are not designed to a 250 or 300 HP upper limit. They ARE overbuilt for the class they're in.
They, in fact, are horsepower restricted at high RPM's to fit in a particular HP class (an anomaly specific to the marine/outboard industry), all the while putting out huge amounts of torque at lower RPM's. It's a big motor that doesn't have to work hard.
If Mercury wanted to race this engine, you could expect it to put out 450-500hp and still have good reliability.
I really hope the Mercury engineers calculated the torsion applied to that length of camshaft and chose a diameter and wall thickness such that the deflection is acceptable.
I understand, but for many decades they have modified existing designs a lot, or a little, to increase to the power rating. The Verado 300-400 come to mind.....all the same basic architecture as the original circa 2005.
I understand why that might make sense, but that's not what they did with the 225-250 v8 or the 175-200 hp v6's. Sure, they could have made them smaller and lighter, but that would cost a fortune in engineering and manufacturing if they're all different designs to optimize the weight/size for that power class.
I don't think we have nearly enough information on the new engine to make that determination. I will offer that I have seen the claim that something was at its power limit from the factory and there's no room to push it any further at least a dozen times over the years. But in every case, they extract more power. I heard that about the 2011 5.0 Coyote (420 hp NA), that was later upgraded to 435 then 460. I also heard it about the 3.5 Ecoboost (365 hp) that was later upgraded to 375, 450, and ultimately 647. The same went for many outboards, including the early 2.4's that later morphed into 300 hp.
Agreed!
I guess we will have to disagree about the design. I estimate the engine to weigh 325lbs and for a 4.6L double overhead cam V8 that is exceptional.
Well hopefully the OP learned something. And now, back to our Regular-Scheduled Programming.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 47 years (learn something new every day).
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