JD_AMG

So all that rambling and not one single answer? I immensely respect your experience and admire the work you have done, but that wasn't the question I was asking here. Why do you own a pushrod powered Corvette over a DOHC powered sports car/performance car if you are so against using a pushrod engine? With all the bashing you do it seems quiet hypocritical that you "settled" for a new pushrod sports car, so clearly whether the engine is OHV or OHC isn't a big deal like you make it out to be. So whats the deal, why did you buy a pushrod powered Corvette if you are so seemingly against it?

None yet but have an eye out for a good deal on a C5 Z06. A major major appeal of the Corvette is the pushrod engine, allowing the car to be lighter and smaller, and being able to make stupid amounts of power NA with easy to do mods you can install in your garage, good luck doing that with some DOHC V8s out there, looking at you Audi... If the C5 came with something like a Northstar V8 I would likely be looking at other cars, but since it comes with something as great as an LS6 then that's perfect. That makes it much much more appealing than its rivals using OHC engines.

Dethsupp0rt

Wow, that's nice Foosh!

I tossed around getting the Quadrifoglio when they came out, but wanted to see how (un?)reliable they were first. Must admit, they're still on my list.

JerryU

You misinterpret the reason for my bringing up the need for a more advanced smaller cid, double overhead cam, twin turbo engine to meet the rapidly changing automotive world!

Funny, I have a PDF on my website entitled, "MIG Shielding Gas Supply Systems Have Evolved Like The Small Block Chevy!" It extols the virtues of the small block Chevy over the years, covers the Duntov cam with a bottom line shown under the title heading of this 6 page doc I used to explain my part time business: "Both had advances and set backs until the optimum air/gas control was achieved." It explains my part time business, "saving fabricators wasted Argon shielding gas!"

Frankly I don't care about getting better gas mileage! My Street Rod gets ~10 mpg cruising! But as I tease daughter and family in San Antonio Heights CA - I use much less gas than their 3 Prii family- it mostly just goes to local car shows! The Grand Sport mpg is just fine for me- I don't ever let it go into 4 cylinder mode for ~1 to 2 mpg more I could get on the Interstate! Don't need it and I mostly drive on rural roads- more fun!

Unfortunately GM, if they are going to stay in business, must compete and get their average Corporate mpg up! The ICE powered car gets about 19% of the energy in gasoline to the rear wheels (recent EPA data.) Of that, about 1/3 is wasted when braking! We can do better and I would prefer that to EVs!

Smaller cid engines have less friction (F1 went to a 1.6 Liter engine for a reason and most European cars use smaller cid engines because gasoline costs ~$10/gallon!) The use of a turbo to get more power from a small cid engine uses some of the ~30% wasted energy that goes out the exhaust! Recovering some of the wasted braking energy can be done with a small, "short duration" hybrid, as used in F1. The idea of using the motor/generator to power the front wheels is even better.

That is my reason for hoping the C8 will use more energy efficient systems- so it can stay around and delay an EV Vette! Not that I need better mpg!

JD_AMG

I see, you have the misconception that a smaller ci will make a significance difference, or any difference at all with MPG while making the same hp, in the same weight car. Now notice that last line, that makes all the difference in the world so don't bother bringing in examples of small 100hp economy cars to compare with 500+hp V8s performance cars...

So lets take a look for comparison here.
Lets compare performance cars before any fancy fuel saving feature were being used, and all with similar power outputs but different displacement.

2004 Corvette Z06 5.7L (V8 400hp) - 19/28mpg

2002 Camaro SS 5.7L (350hp V8) 19/28mpg

2004 Honda S2000 2L (I4 240hp) 20/25mpg (just for fun here, a low power 2L I4 gets worse gas mileage than a 5.7L V8)

2004 350Z 3L (V6 287hp) 20/26mpg

2004 EVO 2L (I4 300hp) 18/26mpg

2004 STi 2L (I4 300hp) 18/24mpg

2004 BMW M3 3L (I6 333hp) 16/24mpg

2004 Porsche 911 3.6L (F6 320hp) 18/26mpg

So from this it looks like the opposite of what you are saying is true. Somehow the engine with the most displacement is actually getting better gas mileage while making more power too! And it just happens to be a pushrod engine...

What about at higher outputs?

2006 Corvette Z06 7L V8 (505hp) 16/26mpg

2006 F430 4.3L V8 (490hp) 13/17mpg

2007 Porsche 911 Turbo 3.6L F6 (480hp) 18/25mpg

2006 Lambo Gallardo 5L V10 (520hp) 10/19mpg

So it looks like once again, displacement alone doesn't necessarily dictate gas mileage.


So my thought is why not pair an electric motor system with the smaller/lighter/more efficient pushrod V8 and have best of both worlds? Why not add turbos to the pushrod V8, and an electric assist? If you want smaller displacement use a smaller displaced pushrod V8 and turbos. Make a new smaller displacement block (physically smaller, less max CI available) and have an even lighter/smaller package than now, and add turbos.

Even in your broken record of the Alfa sedan, its gets WORSE gas mileage(17/24mpg) than the 7L LS7, and that is with the new way EPA tests cars that is heavily biased to smaller ci engines that have stop/start tech(and it has two more gears to use). So it looks like AGAIN what matters is the amount of power being made, NOT the displacement, a 505hp car is not going to get as good gas mileage as a 405hp car, all else being equal, so on and so forth.

Why do the european performance cars get such bad gas mileage compared to the American equivalent then? You are again confusing using a smaller 100hp 3 cylinder for gas mileage with using a small displacement engine that is over stressed to make big power and therefore suffers MPG. They have had taxes on displacement for decades that just recently got removed, THAT is the reason for the lack of higher CI engines in performance cars, not gas mileage. Now China has a tax on engines more than ~4L, so you will see many cars with less than 4L so they can be sold competitively in the growing Chinese market.

BEAR-AvHistory

Be a lot more useful if your examples were not 12 to 17 years out of date. The EPA does not even use those standards anymore. Horsepower rating system changed in 2004 but was not fully implemented by all makes for a few years.

JerryU

You can dream on and bring up whatever apple and orange examples you want, BUT:
Small cid is less friction and better "obtainable" mpg! The European's and other countries have not been doing that for over 80 years because they think small!

Fact is, you can design an engine for max mpg or max hp or as typical a compromise. That is a significant advantage of a dual cam engine, you can vary the intake and exhaust cam timing separately.

The 535 hp crate engine version of the LT1 has a "bigger cam," i.e. more lift and duration. It eliminates the variable cam timing so valves don't hit pistons giving up the extra low end torque. In fact the torque is not much more than the 460 hp LT1.

Sounds like you won't be one who gets over the obsession with a large cid pushrod FE like those who use the excuse, "No round taillights No C7!" That's OK you can buy used C7s! Or perhaps you'd be happy when you look and see all your opinions are EVs!

Best think about buying a 650 hp 572 cid NA BB Chevy pushrod crate motor and building your own car!

Warp Factor

That depends on how high you need to rev the engine to obtain the horsepower. Early and current attempts at higher revs to obtain the horsepower showed such high frictional and hydrodynamic losses, that the current strategy has gone to big boost at lower rpm's.

I would guess that you are just starting to get your feet wet, in the power world.

Sure, I had the hottest babe in the world last night, in my dreams. Try to get a grip.

BEAR-AvHistory

Second part of the equation is Turbo or Supercharging which is pretty much standard on small displacement engines. Both my 3.0L Turbo 6's have full torque in the high teens & max power is at 5400rpm also get 22 city & 32 highway actual with 370WHP+.

JerryU

Since you are obviously looking up answers to prove you're correct, thought while on my 2 mile fast walk up hill on my Tread Mill I'd as the question, "Why do small cid engines get better mpg?"

Some interesting answers. The first few are somethat subjective, even though some are from engineers they are perhaps easier to digest that what I put in the side bar below that:

To go along with my smaller cid is less friction, one post said: “Even when the car is not moving the large cid engine takes more gasoline simply to idle.:

Another notes; Pumping loses are from pushing air around inside an engine are important. More displacement more air to move more energy. Bigger or more cylinders make more friction and more energy.

[Note the pumping loss comment is interesting. Remined that when the LT1 goes into 4-cylinder mode they carefully shut the valves in a sequence to maintain the pressure right after a combustion cycle! Does that mean there are no losses? No the piston rings are still sliding over the cylinder walls and the rod bearings still have friction. In addition, even though there are no pumping losses the captured exhaust gas cools putting energy into the cylinder walls and when it compresses on each stock, it heats slightly and that heat will also go into the cylinder walls.]

The engine can be too small. It depends on the application. While a 900cc turbocharged engine in a Fiat 500 is no better than a 1.2-liter the 1.2 is recording figures almost 7 mpg better than the slightly larger 1.4-liter unit--so 1.2 liters is probably the sweet spot for the 500.

SIDE BAR
I hesitate putting this in as most will just roll their eyes but here is a technical explanation. (Was reminded of that poor Corvair engine in that undergrad Lab that we abused getting all those objective numbers!) Used some words I found in a discussion of the topic since it made is somewhat easy to understand.

An engine is “typically” most efficient in terms of power per unit of fuel at 60%–80% of full throttle near it’s peak torque speed. That does NOT mean you will have the best fuel economy at 60% to 80% throttle while you drive. Factors like transmission shifting, and driving dynamics are also key factors

Theory of Fuel Used Per Unit of Work (Power) The graph below is the Brake Specific Fuel Consumption (BSFC) map. It’s graphing the mass of fuel in grams that is used to produce one kilowatt hour of power/work (g/kWh). The x and y axis are engine speed and torque respectively.

When you have a smaller engine, the throttle must be open further to produce the same amount of power. If you replace the 1.9 Liter engine say a 3.0L V6 the BSFC map for that engine would look like this, but with the whole BSFC “bulls eye” shifted up, or the torque axis shifted down. In that case, the BSFC for a given torque and rpm would be higher. This means it will take more fuel to produce the same amount of power since we’re further away from the engine’s “Sweet Spot”, it’s most fuel to power efficient range.

An engine is “typically” most efficient in terms of power per unit of fuel at 60%–80% of full throttle near it’s peak torque speed. That does NOT mean you will have the best fuel economy at 60%80% throttle while you drive. Factors like transmission shifting, and driving dynamics are also key factors. Note each engine is different!

Theory of Fuel Used Per Unit of Work (Power) The graph below is the Brake Specific Fuel Consumption (BSFC) map. It’s graphing the mass of fuel in grams that is used to produce one kilowatt hour of power/work (g/kWh). The x and y axis are engine speed and torque respectively.

When you have a smaller engine, the throttle must be open further to produce the same amount of power. If you replace the 1.9Liter engine say a 3.0L V6. The BSFC map for that engine would look like this, but with the whole BSFC “bulls eye” shifted up, or the torque axis shifted down. . In that case, the BSFC for a given torque and rpm would be higher. This means it will take more fuel to produce the same amount of power since we’re further away from the engine’s “bulls eye”, it’s most fuel to power efficient range.

PS: Don't expect many of the ~400 "vocal majority" who posted on this Thread will agree with the conclusions BUT perhaps some of those 78,000 "silent majority" who have viewed the Thread might!

Darion

Nah, wouldn't have made a difference, I used more current info and the target was just changed.

Look all, there are so many variables that come into play, most of which aren't being considered, that the whole conversation is kinda comical. End of the day, more air more fuel. More HP more of both.

Really none of it matters, both tech are old and camless is the way if dino burning engines have a future, otherwise its electric. And for the record, my DOHC 4 cyl motorcycles have be outstanding running out to 13k rpm plus, love it! So, I'm really a fan in the right application.

PC

JD_AMG

I know you have massive reading comprehension problems but please try to keep up:
"Lets compare performance cars before any fancy fuel saving feature were being used, and all with similar power outputs but different displacement."

Warp Factor

Quote:Originally Posted by Warp Factor You can dream on and bring up whatever apple and orange examples you want, BUT:
Small cid is less friction and better "obtainable" mpg!Quote
________________________________________
Oh dear, it was you who said that, not me!
________________________________________ _
Originally Posted by JerryU That depends on how high you need to rev the engine to obtain the horsepower. Early and current attempts at higher revs to obtain the horsepower showed such high frictional and hydrodynamic losses, that the current strategy has gone to big boost at lower rpm's .
________________________________________ _______
Oh dear, it was I who said that, not you. I don't know whether your errors were mistakes, or sourced in skullduggery, but either way, I hope you can do better in the future.

Shaka

See post 783

JD_AMG

As I figured, you have no argument and more bench racing.
Europeans have been using smaller displacement engines because of moronic outdated taxes that tax a car based on engine displacement. Same goes for Japan. If they really wanted better mpg they would tax GAS MILEAGE, like the US.
Why do all those cars get WORSE gas mileage than the Corvette despite the displacement difference?

Correct, at the cost of size, weight and complexity on V engines.

What is your point?

Wrong again. I like what works best, what makes the most power density, and don't care about useless stats like which engine has more/less displacement. I care about results, and don't care about how much "tech" an engine has if its not delivering the results (power to WEIGHT and SIZE, MPG).

Why would I want a heavier/larger V8 when I can have a lighter/smaller V8 making the same power and getting the same MPG??? Please answer that one.


If GM decides to kill off the V8 then I much rather have an EV Corvette than some wheezy/farty V6 or I4 Corvette. If they decide to use a DOHC V8 thats fine but Id rather see a lighter/smaller V8 in there for better performance. - Again results matter. I don't care how many cams it has, valves, redline, turbos, whatever else. 500hp is 500hp is 500hp, give me 500hp with the lightest/smallest packaging while being reliable and affordable.

Would be cool if I just wanted to drag race but I prefer a small block (power density). Small engine in a smallish lightweight sports car, like a pushrod V8 in the Corvette.

BEAR-AvHistory

You want to go back in time. How about a 1975 350CI Corvette with 165BHP 12MPG. If the Corvette was too expensive you could always buy a Z28, the hottest one you could buy, came from the factory with a 155-horsepower, 350-cubic-inch V8 10MPG. !975 Ferrari 179CI with 251BHP 12 MPG

Give me a break.

BTW You are talking about real world fuel economy, do you have real world gas mileage experience with a Corvette?

JD_AMG

I fully understand the theory, but as you should know what looks good on paper doesn't always play out in the real world. Like my example in the post you were quoting, why do all those cars get worse gas mileage then the Corvette?

You're not talking about the 1.2L that makes significantly less power than the 1.4L are you? Maybe you can find examples of apples to apples comparison where the power output is closer to the same like I did?

JoesC5

My 2.3L DOHC 4 banger sedan has a .28Cd and has a larger frontal area, than my C6 Z06 with it's .34 Cd and OHV 7.0L V8 engine. The CdA is about the same for both cars.

My sedan weighs about 75 pounds more than my C6 Z06. Both get 29-30 MPG while driving 70-75 MPH on the highway.

The 4 banger gets around 5 MPG better fuel economy driving in town.

My Z06 is much, much faster than my 4 banger, even with the positive displacement Roots supercharger on the 4 banger.

JD_AMG

Thanks for further proving my point. The tired old 350ci Corvette in your example gets the same gas mileage as a "high tech" Ferrai of the time, with less ci. Looks like displacement still doesn't dictate gas mileage.

Real world seems to favor the Corvette even more, owners on here report 30+mpg highway on road trips. Friends with Corvettes report the same, and friends with LS1 Fbodies report the same.

JD_AMG

So the Z06 with significantly more power gets the same mpg on the highway, and a little less in city driving?

Also the Z06 gets better mpg than its rated for highway driving, hope you are reading this BEAR-AvHistory.

BEAR-AvHistory

While delivering 100 more horsepower for the same amount of fuel used out of 171 less cubic inches. What is your point again?

Every auto company including GM has made the change but do keep hanging on to your dream.


How much better then EPA 's 22 highway? C&D road test gave it a 24. Thing is who has gas mileage on their radar when buying a StingRay?

Some Z06 owners say
https://www.corvetteforum.com/forums...ghway-mpg.html