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V-8 vs. flat 8
V-8 is a MUCH stronger package - and the heavy stuff (crank and bearings for it + oil pump if any ARE just as low as flat 8 not a bad compromise |
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Not sure why an 8 is supposedly better than a 6. Both are inherently balanced, though the 6 can make do with lighter counterweights on the crank. In the end, it's an air pump. Either one can be a slug or a fantastic engine.
These days, a 2 liter engine can comfortably make 260 HP all day long on pump gas (even GM has one!), so I fail to see why 8 vs 6 cylinders makes a difference. |
exactly
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An 8 would be much less stressed at making its power as its between more cylinders. The V8 has way more weight up top. The crank and bearings are not the heavy part, its the heads and intake! Keeping that weight low, which is what our flat-6's do so well is important. It seems I am alone on this thread so I will not discuss the idea anymore, it must be absurd. I do hope Porsche is reading this just for the heck of it though. That Corvette SS is going to be tough to beat :( |
8s are no more magical then 6's. In the old days ('60's) Porsche had to go with more cylinders because air-cooled engines were limited to 2 valves, which limited the valve sizes. If you got enough valve area for the big HP in a 6, the valves, pistons, rods and stuff got too big and heavy for the high rev's required, or else you would have a really short stroke which caused a lower CR unless you ruined the combustion chamber with intruders and such. So in the '60's, adding two more cylinders was easier.
As far as a flat-8 versus a V8, both can be well balanced -- if you trade off the exhaust design by giving up firing pattern that alternates between the banks. Porsche tried to make a flat-crank Flat-8 work with the first iteration of the 908 engine, but the vibrations caused things to break. So they quickly switched to a 90 degree crank design (and the associated firing pattern) which resolved the problem. A flat-8 will be lower then a V8 assuming that both have overhead cam designs, and even more-so in a double-overhead camshaft design because the cams are fairly massive, and make a difference when mounted up high. Detroit side-stepped this problem by using a rocker-arm design, which also reduced the width of the engine. A V8 is also stronger due to the more compact volume that the engine takes up. The downside of the big V8 is that it took about 30 years to get the overhead valve V8 to rev has high as Porsche's 908 engines, and about 40 years and a lot of CAD and dynamic modelling work before they could get the OHV V8 to rev as high as a Cosworth DOHC, 4-valve V8. Nowadays, things are different... - Air-cooled is a thing of the past - Casting and materials technologies have progressed quite a bit - Combustion Chamber design has been highly refined. - Variable valve timing and engine management systems have made tremendous technological jumps. The result is that: - 6 cylinder engines have less friction then 8 cylinders -- which is a good thing for mileage. - Valve train and induction systems allow higher revs without sacrificing performance at low rev's. Basically today's engines pull like a T below 4000 RPM, and like an S above 4000 RPM. - The 4-valve cylinder head allow a compact combustion chamber (and thus a good CR) as well as good flow in and out of the engine. The smaller valves also allow higher revs. - A 6 cylinder engine won't be as long as an 8 cylinder engines, which in a 911 is important as Porsche manages the car's weight distribution and interior space.. |
I'm sold. Flat six it is.
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