991 GTS on the Scale
#46
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That would be an interesting swap project! One of my favorite cars had a BMW V12 inserted into a Euro Mid-Engined chassis (McLaren F1).
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Also, don't sell pushrods too short on the rpm issue. An LS7 is good for 7000 rpm, but I do agree that the sound it makes at that speed, while very "NASCAR", just isn't as melodious as a flat six at the same speed...subjectively speaking.
As to rpm for the sake of rpm, we've become accustomed to those elevated Porsche engine speeds mainly because they're necessary for good power production from limited displacement. Horsepower is only a calculated number based on torque and rpm, and if there isn't a lot of torque, then there had better be a lot of rpm or a small horsepower number will be the result.
In terms of torque production, without resorting to forced induction, there is no tuning trick that can fully compensate for a lack of displacement. Porsche's Turbo is the result of this reality. It has a thick, almost lag-free, torque-rich power band...but at what physical and economic cost? They've had to add the bulk/mass of two turbos, two intercoolers, and all of the associated controls and plumbing required, to an already large, heavy, and expensive NA engine. And while the result is a wonderful and amazingly fast car, how much more amazing (and affordable!) would it have been with an equally-powerful large-displacement pushrod V8 that would have completely eliminated both turbo lag and at least 200 lbs from the back of the car?
I guess now I'm the one who's guilty of bench racing...because of course, such a car could never exist in our universe. Even without constraining European government regulations, Porsche's current clientele would just spit it out, as the car would be different from what they're used to. Would there be enough potential "different" clients to make up for that? Who can say?
And let's not forget Pagani...an "F1" with Bugatti-level fit and finish. Wow!
#48
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While a bulky Euro V8 might not physically fit into a Cayman (unless its displacement was truly tiny), a larger-displacement pushrod V8 just might fit because the cylinder heads are so compact...and that's part of my point. While all those cams/valves/rpms/etc. sound really sexy, what good are they if they keep the engine out of your car? After all, these engines have to haul themselves around (mass) and so, need to fit into their vehicles (bulk). Pushrods really shine on both these issues.
Also, don't sell pushrods too short on the rpm issue. An LS7 is good for 7000 rpm, but I do agree that the sound it makes at that speed, while very "NASCAR", just isn't as melodious as a flat six at the same speed...subjectively speaking.
As to rpm for the sake of rpm, we've become accustomed to those elevated Porsche engine speeds mainly because they're necessary for good power production from limited displacement. Horsepower is only a calculated number based on torque and rpm, and if there isn't a lot of torque, then there had better be a lot of rpm or a small horsepower number will be the result.
In terms of torque production, without resorting to forced induction, there is no tuning trick that can fully compensate for a lack of displacement. Porsche's Turbo is the result of this reality. It has a thick, almost lag-free, torque-rich power band...but at what physical and economic cost? They've had to add the bulk/mass of two turbos, two intercoolers, and all of the associated controls and plumbing required, to an already large, heavy, and expensive NA engine. And while the result is a wonderful and amazingly fast car, how much more amazing (and affordable!) would it have been with an equally-powerful large-displacement pushrod V8 that would have completely eliminated both turbo lag and at least 200 lbs from the back of the car?
I guess now I'm the one who's guilty of bench racing...because of course, such a car could never exist in our universe. Even without constraining European government regulations, Porsche's current clientele would just spit it out, as the car would be different from what they're used to. Would there be enough potential "different" clients to make up for that? Who can say?
And let's not forget Pagani...an "F1" with Bugatti-level fit and finish. Wow!
Also, don't sell pushrods too short on the rpm issue. An LS7 is good for 7000 rpm, but I do agree that the sound it makes at that speed, while very "NASCAR", just isn't as melodious as a flat six at the same speed...subjectively speaking.
As to rpm for the sake of rpm, we've become accustomed to those elevated Porsche engine speeds mainly because they're necessary for good power production from limited displacement. Horsepower is only a calculated number based on torque and rpm, and if there isn't a lot of torque, then there had better be a lot of rpm or a small horsepower number will be the result.
In terms of torque production, without resorting to forced induction, there is no tuning trick that can fully compensate for a lack of displacement. Porsche's Turbo is the result of this reality. It has a thick, almost lag-free, torque-rich power band...but at what physical and economic cost? They've had to add the bulk/mass of two turbos, two intercoolers, and all of the associated controls and plumbing required, to an already large, heavy, and expensive NA engine. And while the result is a wonderful and amazingly fast car, how much more amazing (and affordable!) would it have been with an equally-powerful large-displacement pushrod V8 that would have completely eliminated both turbo lag and at least 200 lbs from the back of the car?
I guess now I'm the one who's guilty of bench racing...because of course, such a car could never exist in our universe. Even without constraining European government regulations, Porsche's current clientele would just spit it out, as the car would be different from what they're used to. Would there be enough potential "different" clients to make up for that? Who can say?
And let's not forget Pagani...an "F1" with Bugatti-level fit and finish. Wow!
#50
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I would guess oiling issues and the way counter weights react. Isn't Ford building a flat plane 8 cylinder for the up and coming GT 350. Don't know if it's push-rod though.
Last edited by jimbo1111; 04-29-2015 at 03:09 PM.
#51
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The flat six is an inherently smooth running design. Going pushrod would to my ignorant mind seem to be merely swapping pushrods for the overhead cam. My guess is this means lower revs, which means you need more displacement- which the regulators have ruled out.
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You are 100% correct except you are missing a couple of key notes. The 6 cylinder motor that Porsche uses is designed around the chassis in that the weight is at the lowest possible position. Remember that it's a road machine and not a 1/4 mile car. Some compromises have to be made in order to have a well rounded sports car. Sure a V8 would do a lot in the strait line performance but at the other spectrum of road handling it would exacerbate a flaw to the chassis dynamics.
As far as "well rounded sports cars", have you tried keeping up with a "top-heavy-V8-powered" C7 on a road course? While I can't get past its looks, I do realize that its mechanical package makes for an undeniably effective sports car.
It'll never happen. The Germans (in general) don't believe in pushrods. They think of them as last century old-fashioned. Even though pushrods still make perfect sense from a mass/bulk/cost standpoint, they look down their noses at them. I'm speaking from first hand knowledge here. I worked in a U.S. OEM engine plant for decades, and visiting German engineers were always blowing their noses on our most successful and reliable pushrod design. Trust me, if they aren't using it, it's no good...period.
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1analguy, I can sympathize with you on the pushrods, but you've lost me on the engine height. Here are cutaways of a 991 and corvette. The entire 991 engine sits at roughly axle level. Crank, heads, all the same level. Even the intake, which is pretty much plastic, sits within wheel height. Not only that, but when you get into the details Porsche has all the ancillaries- alternator, pumps, etc- packed into that same plane right about axle level. Check it out.
Sure it looks like chevy got the crank down low. But looking at their engine this may only have been to enable the driver to see over it! The heads are way up at the top of the tires, and the intake sits a good deal higher than that. There's a great big alternator that appears to be perched about as high as they could find and still fit under the hood.
If you're surprised how high the engine sits in a 911, instead of looking at the fans and covers, try looking at the engine. If you do that I doubt if you'll be surprised how much lower it is than the vette. You'll be shocked.
Sure it looks like chevy got the crank down low. But looking at their engine this may only have been to enable the driver to see over it! The heads are way up at the top of the tires, and the intake sits a good deal higher than that. There's a great big alternator that appears to be perched about as high as they could find and still fit under the hood.
If you're surprised how high the engine sits in a 911, instead of looking at the fans and covers, try looking at the engine. If you do that I doubt if you'll be surprised how much lower it is than the vette. You'll be shocked.
Last edited by chuck911; 05-09-2015 at 02:13 AM.
#54
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While a bulky Euro V8 might not physically fit into a Cayman (unless its displacement was truly tiny), a larger-displacement pushrod V8 just might fit because the cylinder heads are so compact...and that's part of my point. While all those cams/valves/rpms/etc. sound really sexy, what good are they if they keep the engine out of your car? After all, these engines have to haul themselves around (mass) and so, need to fit into their vehicles (bulk). Pushrods really shine on both these issues.
Also, don't sell pushrods too short on the rpm issue. An LS7 is good for 7000 rpm, but I do agree that the sound it makes at that speed, while very "NASCAR", just isn't as melodious as a flat six at the same speed...subjectively speaking.
As to rpm for the sake of rpm, we've become accustomed to those elevated Porsche engine speeds mainly because they're necessary for good power production from limited displacement. Horsepower is only a calculated number based on torque and rpm, and if there isn't a lot of torque, then there had better be a lot of rpm or a small horsepower number will be the result.
In terms of torque production, without resorting to forced induction, there is no tuning trick that can fully compensate for a lack of displacement. Porsche's Turbo is the result of this reality. It has a thick, almost lag-free, torque-rich power band...but at what physical and economic cost? They've had to add the bulk/mass of two turbos, two intercoolers, and all of the associated controls and plumbing required, to an already large, heavy, and expensive NA engine. And while the result is a wonderful and amazingly fast car, how much more amazing (and affordable!) would it have been with an equally-powerful large-displacement pushrod V8 that would have completely eliminated both turbo lag and at least 200 lbs from the back of the car?
I guess now I'm the one who's guilty of bench racing...because of course, such a car could never exist in our universe. Even without constraining European government regulations, Porsche's current clientele would just spit it out, as the car would be different from what they're used to. Would there be enough potential "different" clients to make up for that? Who can say?
And let's not forget Pagani...an "F1" with Bugatti-level fit and finish. Wow!
Also, don't sell pushrods too short on the rpm issue. An LS7 is good for 7000 rpm, but I do agree that the sound it makes at that speed, while very "NASCAR", just isn't as melodious as a flat six at the same speed...subjectively speaking.
As to rpm for the sake of rpm, we've become accustomed to those elevated Porsche engine speeds mainly because they're necessary for good power production from limited displacement. Horsepower is only a calculated number based on torque and rpm, and if there isn't a lot of torque, then there had better be a lot of rpm or a small horsepower number will be the result.
In terms of torque production, without resorting to forced induction, there is no tuning trick that can fully compensate for a lack of displacement. Porsche's Turbo is the result of this reality. It has a thick, almost lag-free, torque-rich power band...but at what physical and economic cost? They've had to add the bulk/mass of two turbos, two intercoolers, and all of the associated controls and plumbing required, to an already large, heavy, and expensive NA engine. And while the result is a wonderful and amazingly fast car, how much more amazing (and affordable!) would it have been with an equally-powerful large-displacement pushrod V8 that would have completely eliminated both turbo lag and at least 200 lbs from the back of the car?
I guess now I'm the one who's guilty of bench racing...because of course, such a car could never exist in our universe. Even without constraining European government regulations, Porsche's current clientele would just spit it out, as the car would be different from what they're used to. Would there be enough potential "different" clients to make up for that? Who can say?
And let's not forget Pagani...an "F1" with Bugatti-level fit and finish. Wow!
#55
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https://rennlist.com/forums/991/842093-g-g.html
https://rennlist.com/forums/928-foru...b-project.html
http://jalopnik.com/the-10-best-engi...ars-1510676043
991 is approx 100 lbs heavier (3/4 tank) and is better in the curves, LS3/525 928 (1/2 tank) is faster in the straights. Both a blast to drive. T
https://rennlist.com/forums/928-foru...b-project.html
http://jalopnik.com/the-10-best-engi...ars-1510676043
991 is approx 100 lbs heavier (3/4 tank) and is better in the curves, LS3/525 928 (1/2 tank) is faster in the straights. Both a blast to drive. T
Last edited by 77tony; 04-30-2015 at 10:03 PM.
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1analguy, I can sympathize with you on the pushrods, but you've lost me on the engine height. Here are cutaways of a 991 and corvette. The entire 991 engine sits at roughly axle level. Crank, heads, all the same level. Even the intake, which is pretty much plastic, sits within wheel height. Not only that, but when you get into the details Porsche has all the ancillaries- alternator, pumps, etc- packed into that same plane right about axle level. Check it out.
Sure it looks like chevy got the crank down low. But looking at their engine this may only have been to enable the driver to see over it! The heads are way up at the top of the tires, and the intake sits a good deal higher than that. There's a great big alternator that appears to be perched about as high as they could find and still fit under the hood.
If you're surprised how high the engine sits in a 911, instead of looking at the fans and covers, try looking at the engine. If you do that I doubt if you'll be surprised how much lower it is than the vette. You'll be shocked.
Sure it looks like chevy got the crank down low. But looking at their engine this may only have been to enable the driver to see over it! The heads are way up at the top of the tires, and the intake sits a good deal higher than that. There's a great big alternator that appears to be perched about as high as they could find and still fit under the hood.
If you're surprised how high the engine sits in a 911, instead of looking at the fans and covers, try looking at the engine. If you do that I doubt if you'll be surprised how much lower it is than the vette. You'll be shocked.
Your pic of the Z06 illustrates nicely the Chevrolet did indeed get the engine mounted low...remember, those front tires are about 1.25" shorter than the rears on the 991. That LT4 has a supercharger on top of it that is probably not even visible from the driver's seat, even with the hood open. Those Corvette development guys can never be accused of not thinking about their car's dynamics. That's why Corvettes always produce such great numbers. Now, if they would just show more concern for the car's refinement...
This is strictly an "apples-to-pomegranates" comparison. Is it really so surprising that a car designed in the mid 70s is out-handled by a car that was designed when the 991 was? Though, that breathed-on LS3 is a really tough act to follow. 525 hp (and lots of torque) from a 415 lb street-legal engine? Not to bad, for pushrods...