Engine design question
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Engine design question
Hey i'm doing a bit of research into different engine designs and I have a question that I cannot get a straight answer to. I thought this might be a good forum to post this in. For the sake of even numbers, let's say I have three 6.0 liter engines designed by the same company. One is a V6 (each cylinder one liter), one is a V8 (each cylinder 750cc), and one is a V10 (each cylinder 600cc). The V10 would be the most expensive, but would it generate more power? Is it better to have a larger number of smaller cylinders or a smaller number of larger cylinders? Is one of these hypothetical engines better for hauling and another for raw acceleration, or does it all just depend? I've been given explanations that the V10 would produce more power but isn't worth the extra money, and I've been told the V6 would produce the most, some say V8 because of efficiency matters. Anyway, any info would be appreciated.
Post Fiend
Joined: Jan 2003
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From: Iowa
There's a number of different ways to look at this. If they are all 90 degree engines, where the cylinder banks are 90 degrees apart, the V6 and to some extent the V10, would be shakers. It would be very difficult to balance them correctly. The V8 would be a smooth balanced engine.
It's hard to say which would make the most power and torque, or anything else for that matter. How are you getting the displacement per cylinder difference? Are you varying the stroke, or are you varying the cylinder bore diameter? What head design is used? Open chamber, hemispherical, or quench type heads? 2 or 4 valves per cylinder? Which engines get 2 valves and which ones get four? Do the heads all have the same size ports, or do the ports get smaller on the V8 and V10 to compensate for the decreased displacement per cylinder? Do they all use the same cam profile?
You see, there are no easy answers here.
It's hard to say which would make the most power and torque, or anything else for that matter. How are you getting the displacement per cylinder difference? Are you varying the stroke, or are you varying the cylinder bore diameter? What head design is used? Open chamber, hemispherical, or quench type heads? 2 or 4 valves per cylinder? Which engines get 2 valves and which ones get four? Do the heads all have the same size ports, or do the ports get smaller on the V8 and V10 to compensate for the decreased displacement per cylinder? Do they all use the same cam profile?
You see, there are no easy answers here.
Last edited by rusty70f100; Mar 7, 2006 at 01:45 PM.
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If you use the laws of physics, the V6 given that the VE is equal, due to the losses incurred from friction. The V configuration balance issue is negated by utilizing crankshaft that have uncommon rod journals, thus allowing them to be fired in equal degrees of rotation.
rusty, CF Iowa, could that be Cedar Falls, just outside of Waterloo?
rusty, CF Iowa, could that be Cedar Falls, just outside of Waterloo?
Post Fiend
Joined: Jan 2003
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From: Iowa
Yep, Cedar Falls.
Another way to look at it, is the V10 would be more powerfull, if the cylinder bores are smaller. This would mean the mixture would be burned faster, and closer to TDC. The motor would become more efficient. OR you could reduce the stroke of the crank, in which case you'd have less piston speed to deal with, and you could build a higher revving motor and gain more HP there.
Like I said before, no easy answers. It could go any direction depending on how the engines are put together.
On balancing, I was thinking more about some manufacturer's 90 degree V6 motors that are simply V8's minus 2 cylinders. Think Chevy 4.3L V6. The best way to do it is a 60 degree V6 on a split pin crank, like you were saying.
Another way to look at it, is the V10 would be more powerfull, if the cylinder bores are smaller. This would mean the mixture would be burned faster, and closer to TDC. The motor would become more efficient. OR you could reduce the stroke of the crank, in which case you'd have less piston speed to deal with, and you could build a higher revving motor and gain more HP there.
Like I said before, no easy answers. It could go any direction depending on how the engines are put together.
On balancing, I was thinking more about some manufacturer's 90 degree V6 motors that are simply V8's minus 2 cylinders. Think Chevy 4.3L V6. The best way to do it is a 60 degree V6 on a split pin crank, like you were saying.
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Post Fiend
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From: "Islander"
Hence the "Boxer" motor like BMW motorcycle twins, Porsche the last 69 years, Subrau, Lycoming and Continental aircraft motors. Both pistons go away and together, cancel each other out except for rocking coupling motion to a small degree.
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Fleet Owner
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From: Lake Tahoe, Nevada
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Post Fiend
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From: "Islander"
I'm lost on this "valves burn"? Back in 54 dad raced VW/s with Judson SC's then got into road racing Porsche's until too old, I too over a little driving SCCA but college stopped me. We never had "valves burn". Early Porsche (74 Cararra) mechanical fuel injection lean out burnt pistons yes but that's being stupid as CHT and oil temps would show up first.
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Fleet Owner
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From: Lake Tahoe, Nevada
Well no offense intended. But you might be surprised at the number of VW valves that have burnt because most of the owners never took seriously the need to adjust their valves. With your experience, you are aware that this is a critical and frequently needed adjustment.
Fleet Owner
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From: Lake Tahoe, Nevada
Originally Posted by Beemer Nut
Think about how many VW bugs and vans that ran around during the hippie era, you think they pulled any regular maintenance?
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Elder User
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From: So. California
I think that the V6 would be torquiest off idle, the V 10 would have teh best mid range 5000+ rpm and the V8 would be a compromise good 2300-4500 better.
I am draqing this off of desk top dyno...
I am draqing this off of desk top dyno...
Post Fiend
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From: "Islander"
Tech, formula 1 is state of the art in motors and suspensions yes i'm a fan, Indy cars are just brute force. Give F1 back the turbo and wide tires and watch them perform. Kind of like Top Fuel vs Pro Stock, Pro Stocks high tech.
Please bring back the Can Am cars we miss them.
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Please bring back the Can Am cars we miss them.
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