Bean

iTrader: (1)

2v motors making more low end power than a 4v motor is a myth and a lie... its just 4v motors are able to make more top end power and still run smooth; so typically they are tuned that way

take a look at Nissan's Titan fullsize; its the size of the dodge, yet its running a 5.6L 32v V8... makes 400ft-lbs of torque and its available VERY early in the power band... its a 4v motor and its still making lots of low end power...

the reason the american trucks use the 2v setup is because its cheaper to build and easier to work on and tune

http://www.nissanusa.com/vehicles/Mo...butes/0,,31963|31005|,00.html

jet864

Not trying to start anything, but out of innocent curiosity, why would corvette continue to make all corvettes pushrod 2V/cylinder? Would OHC be more efficient and more reliable?

James

ChrisFL

Aren't all the top fuel drag cars and funny cars using Hemi designs? That says a lot to me about power capability

jet864

I think that there are restrictions that limit the top fuel cars to 2 valves/cylinder, so the hemi is the best choice for that, and like most American V8s can be built to be rock solid to handle the nitromethane and insane amounts of power theyre putting down.

James

moparpopo

That statement is not a lie. Why is a 4 valve engine tuned for the upper end of the RPM range, because as you said, that's where it makes the most power and torque. That's different than a 2 valve engine which is more efficient in the lower rpm range and those engines are tuned to make more power down in the lower rpm ranges. That's where the hemispherical head design will out do the wedge design all day long!

When towing you need power down low, not in the upper RPM range. It's hard on the tranny and other drive train components to get a heavy tow load or carry load moving. If you have to rev the engine into a high rpm just to get started moving. This is another reason that torque numbers for trucks are more important than HP numbers.

I tried your link to the Nissan page but it wouldn't pull up for me.

Bean

iTrader: (1)

nah its only because of the restrictions they have; trust me; they'd use DOHC turbo motors if they had the option

Bean

iTrader: (1)

NO
again you're wrong...
a 4valve if tuned for it can make JUST as much torque down low as a 2valve motor...

to prove me wrong; you have to show some evidence of how and why a 2valve setup is going to make more low-end torque than a 4v setup; and you wont get anywhere because that cant be done
since you cant get to the page i'll post the little article:

"The numbers are big. 305 horsepower. 379 lb-ft of torque, with 90% kicking in below 2,500 rpm and a full 80% on tap at a class-leading 1,000 rpm.* But 'the story of Titans V8 goes beyond brute strength. No pushrod relic, this engine is a double-overhead-cam beneficiary of Nissan's advanced engineering. An aluminum block and forged crankshaft offer exceptional strength, while keeping performance-robbing weight down. In addition to the easy-breathing DOHC layout, the high-flow intake ensures that every gulp of air counts. To help cut friction, the camshafts and crankshaft are microfinished, and the piston skirts wear a slick coat of molybdenum, all so the engine can deliver more with less effort. And taking a cue from the jet age, an electronic drive-by-wire throttle connects the brain, right foot and throttle more quickly — and efficiently — than ever."

and i wasnt saying you were making a lie; its just a lie told by musclecar enthusiasts to make themselves feel good about their pushrod motors with 5k rpm redlines

moparpopo

Ok let me try this again. I agree Mr. Bean that if a 4 valve engine is tuned properly it can make the torque of a 2 valve engine in the low rpm range, but the 4 valve engine will loose the highend horse power that engine is designed for. Also why would anyone want to spend the money on the extra valves and its extra maintenance if you are not going to take advantage of it high reving capabilities?

The only company that I can think of that is using a 4 valve head in a low rpm engine is the diesel engine manufactures.
That is the reason that Most of the Domestic Truck Engine Manufactures are still keeping with the 2 valve set ups. Plus it does save on manufacturing cost.

Nissan can thank Chrysler for this advancement!

Also I have attached a few web sites for you to look over about the new Hemi engine and the 4.7 engine which has replaced the 318. I hope it is educational.
http://www.dodgeram.org/tech/gas/Cammer/4_7_v8.html
http://www.allpar.com/
http://www.allpar.com/mopar/hemi/ardun.html
http://www.allpar.com/model/ram/ram-engine.html

I think that Nascar engines are two valve. They turn up to 8,000 rpms!

Bean

iTrader: (1)

yeah they also dont have the same endurance that a normal engine would have with 4v... lets compare it to the Honda S2000... which can turn over 8000rpms no problem... and also last well over 100k miles... i dont think you'll be making a Nascar run that long

if you really want to get down to it; Formula 1 cars are 4v or 5v and they turn up to 19000-20000 rpms on 97 octane

but you have a point on the costs of manufacture... Nissan wont be making as much money on their truck as one of the big 2 will (i say big 2 since Chrysler is no longer 3rd, toyota is)... but they still will have a more reliable and powerful truck... and it still wont be as much maintenance as a domestic truck (taking into account the whole vehicle too)

and there is a way around the trade off of adjusting for low-rpm power... a lot of Nissan's V6s use some type of variable valve tuning... i'm sure it'd be easy enough for the 5.6 V8...
as for the microfinished cams and crank; just showing that Mopar came up with it in the USA doesnt mean someone didnt also come up with it in Japan

mmarshall

Listen, guys....you're forgetting something. Most of the people driving Buicks today DO remember Harley Earl. I agree, though, Buicks (and most GM products) are today built from dime-store parts, especially the interiors. That was not the case in the 50's and 60's.
But there IS something to be said for that smooth, quiet Park Avenue and LeSabre ride...especially when you are tired from a hard day's work. There's more to life than just high-G cornering and ultra-stiff suspensions.
Hey, after all....this is a Lexus forum....some of the smoothest and quietest products out there.

moparpopo

I don't know if you realized that the nascar engine is still a pushrod engine and a carb. Compaired to the honda with DOHC and fuel injection. There is a reason for the lose of endurance. NASCAR engine builders have to stay with in their rule book.



LOL Toyota doesn't even have a production desiel for heavy towing in their fullsize truck. I would like to see a Tundra hooked up to a 30' camper in the mountains or towing some construction equipment to the job site. There is a reason that the Tundra is found in yuppy neighborhoods and parked inside of garages. Its a family truck not a work truck.

Dont be insultive to American Engineers!!!
Nothing else needs to be said!!

For the original person that posted this tread about the New Hemi. I hope the web sites that I have posted have gave you the information that you request and was informative. The new hemi is different than the old, but still delivers good power for the money. Plus it will be less expensive to upgrade than some other vehicles on the market at this time.

Iceman

Yikes! I've got to disagree. I get those Buicks as "upgrades" for rental cars, and the floaty ride practically makes me carsick. In addition, I never feel that the things have a really good hold on the road, especially over 60 MPH or so. I guess there's a reason that only rental car fleets and geriatrics actually PURCHASE Buicks!

jet864

Come on though, the Buick Century's a great car, especially when it lets you drop it into 1st gear on the freeway. Those things can pull some pretty good donuts too if you push em hard enough. Good times.

James