Thoughts on Smaller V-6 Engines

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Originally Posted By: brianl703
I had a couple of cars with Ford's 2.5L Duratec V6. It was on the Ward's 10 best list for a year or two.

This engine has nothing to do with Mazda's 2.5L V6.


You are correct! The only Ford that came with the Mazda 2.5 V6 was the Probe. The 2.5 used in the Contour, Mondeo, and Cougar was a Ford engine.
 
Originally Posted By: rpn453
After reading it over a few times and looking up a couple of words, I follow what you're saying! I'd guess that the Flat 6 would follow the V12 and the I6 in terms of natural smoothness.

I just began picturing the V12 as operating like separate I6s, so it wouldn't even matter that they're offset by a big end width because they're just two naturally balanced engines connected together and providing twice as many power pulses per revolution as a single I6, aiding smoothness but not balance (since the I6 is already balanced). Am I correct? This is the first time I've actually thought about engine balance.


Sounds about right
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Originally Posted By: another Todd
Horsepower is a bogus measurement of power. Torque, especially at lower rpms is a much more useful measurement. Torque is what accelerates you, horsepower is what gives top speed. Since you rarely drive at top speed, but you accelerate every time you drive, torque is the better measurement of an engines "drive-ability". The newer engines boasting high horsepower numbers have to scream up to or near redline to achieve it, and are usually dogs from a stop.


It's torque at the wheels that counts for acceleration, not at the engine. A Mazda RX-8 has 159 lb-ft of torque and does 0-60 mph in 6.5 seconds with a 5-60 mph street start of 7.5 seconds and a 1/4-mile of 15.0 seconds at 93 mph. Is there a car of similar weight with under 160 hp that can match those numbers.

I enjoy using all 7100 rpm of my engine when I really want to get going. With twin balance shafts, it runs pretty smoothly for a 2.3L I4.
 
Originally Posted By: Titan
For smaller displacements, increased complexity of a V-6 is why I'd prefer a 2.5 liter 4 banger. Sure, my Subaru engines rock back and forth when you hit the starter...but, at idle, they are virtually vibration-less. At anything over 1000 rpms, it doesn't feel any smoother or rougher than my 4.6 liter V-8.

For sound, I like the straight six and V-8's the best. (But, I haven't heard a V-10 or V-12 or I-3...actually, I have heard an I-3 in a BMW motorcycle.


If we are going to talk about four cylinder engines, I think 1.0L is a good size for them and that they should be supercharged.
 
Originally Posted By: Titan
Anyone heard of Supercharging and Turbocharging concommitantly? I wonder....


Sure. That was done at the very end of the piston engine airliner era, on the huge radial engines that powered planes like the DC-7 and Super Constellation. I don't recall off hand which aircraft had which particular engines, but yes, turbo-supercharging was commonly done.

The National Naval Aviation Museum here in Pensacola has a cut-away engine collection, and it's a real eye opener to see how incredibly intricate and complicated these engines were. Obviously, a car engine could be done on a less complex level, but this is why I doubt we'll see turbo-compound engines in cars -- too expensive and complex by a long, long margin.
 
Actually, V-6 engines have gotten a lot more powerful over the past 10-15 years and there's now a number of 3-4 liter V-6's that get 240 or more hp and torque. These engines are now more powerful than most of the small block V-8's in the 5 liter range were in the past.
 
...and they still get good gas mileage and require less maintenance, weigh less and still fit into the same space and after all that they run smoother, too.
 
Originally Posted By: ekpolk
Originally Posted By: Titan
Anyone heard of Supercharging and Turbocharging concommitantly? I wonder....


Sure. That was done at the very end of the piston engine airliner era, on the huge radial engines that powered planes like the DC-7 and Super Constellation. I don't recall off hand which aircraft had which particular engines, but yes, turbo-supercharging was commonly done.



The DC-7 engines were turbo compound R-3350 engines and added another twist. They mechanically coupled the exhaust driven turbine to the recip engine output so the exhaust driven turbine contributed directly to turning the propeller. That was the "Turbo compound" in the name.

I don't recall them having mechanically driven superchargers, but that doesn't mean much
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According to Google sources the Super Connie had the same engines. That was news to me.
 
Originally Posted By: XS650
. . .They mechanically coupled the exhaust driven turbine to the recip engine output so the exhaust driven turbine contributed directly to turning the propeller. That was the "Turbo compound" in the name.


Ooops, you're correct on that. Engines for certain WW-2 fighters were turbosupercharged (later Corsairs, for example), and I believe the same for some of the bombers as well. The airliners of the mid 1950s which I mentioned were indeed turbocompound designs (supercharged induction, exhaust driven turbines adding torque to the crankshaft).

EDIT: Gee, I wonder how much extra room you'd need under the Prius' hood to add turbosupercharging AND turbocompounding to the hybrid drive system???
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. . .actually, as I think about it, it might be cool to add a turbocompounded extra generator to capture wasted exhaust flow energy as electrical power, which you could later use to drive the car.
 
One number, whether it be torque or horsepower, will not be a good indicator of performance.

http://dmiessler.com/study/horsepower/ his conclusion:
"So yes, the answer to the question is torque, but torque at the wheels, not at the engine. And since we're talking about torque at the wheels and not at the engine, the actual complete answer is HORSEPOWER because horsepower encompasses not only the engines torque but the total torque that gets put to the ground to accelerate the vehicle.:"

They way I like to put it...it doesn't matter if torque or horsepower is the more important number, I want more of BOTH!


Originally Posted By: another Todd
Horsepower is a bogus measurement of power. Torque, especially at lower rpms is a much more useful measurement. Torque is what accelerates you, horsepower is what gives top speed. Since you rarely drive at top speed, but you accelerate every time you drive, torque is the better measurement of an engines "drive-ability". The newer engines boasting high horsepower numbers have to scream up to or near redline to achieve it, and are usually dogs from a stop.
 
Originally Posted By: another Todd
Horsepower is a bogus measurement of power. Torque, especially at lower rpms is a much more useful measurement. Torque is what accelerates you, horsepower is what gives top speed.


I read somewhere that Ford's 2.5L Duratec V6 put out 75% of it's peak torque at 1500RPM.

That was the only car I ever had that was happy to drive at 15MPH in 4th gear. The shorter gearing helped. You could even start it from a dead stop in 3rd gear with little trouble.
 
Originally Posted By: ekpolk
. . .actually, as I think about it, it might be cool to add a turbocompounded extra generator to capture wasted exhaust flow energy as electrical power, which you could later use to drive the car.


I've seen a mitsubishi paper where they have an electric cerntrifugal supercharger and turbocompounding...enabled the supercharger to do its work the best when needed (regardless of exhaust volume), and the compounded turbine to operate wastegate free.

Could use the turbine to generate electricity.

Detroit Diesel (I beleive) are working on electric assist turbos.
 
Originally Posted By: ekpolk
. . .actually, as I think about it, it might be cool to add a turbocompounded extra generator to capture wasted exhaust flow energy as electrical power, which you could later use to drive the car.


A big problem with that is that car engines spend most of their time operating at low power levels so there isn't much energy to be captured that way. In line with your earlier post, a Prius would be a better candidate for that because of it's higher average %load on the gas engine when it's running.

It would be more difficult to make work than a normal turbocharger setup. With a turbocharger, you add exhaust restriction but add more than enough intake boost to compensate.

With an exhaust turbo used to run a generator or to turbo compound, you would have additional exhaust restriction with no corresponding intake boost.

Cross country trucks would be an easier application because they run at a more consistant high load.
 
Originally Posted By: Shannow


Detroit Diesel (I beleive) are working on electric assist turbos.


DD was working on something like that 20 years ago for their 2-stroke diesels. The 2-strokes all had Rootes blowers which were mainly to control airflow and give a slight boost. The turbo versions added a turbo to that. When the turbo came on boost, the Rootes actually restricted airflow. One option was bypass valves that let the turbo blow right past the roots blower. IIRC, the bypass added about 50 hp to the high performance 6V-92TIA engines. We were running ours at 620 hp at about 2000 rpm. They were only 552 cubic inches. Not bad for a diesel.

The electric boosted turbo enable them to spin up the turbo to where the engine would run without a Rootes blower. They had them running in test but I don't think they ever got to production.
 
Nissan has done it ages ago with their March Super Turbo.

Nissan's MA09ERT engine:

930 cubic cm displacement in-line 4, 7.7:1 static CR, 8 valves, supercharged and turbocharged.
 
Originally Posted By: Camu Mahubah
Originally Posted By: Titan
Anyone heard of Supercharging and Turbocharging concommitantly? I wonder....


Volkswagen has already thought of this and it is running around Europe as we speak!

The Golf GT



I did not know that supercharging a turbocharged engine was possible. Why do we not see more cars designed on this concept?
 
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