What's the advantage of OHV(pushrod) to OHC engine?

[sbc350gearhead]

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Originally posted by kenw:

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Originally posted by T-Keith:

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Originally posted by Spitty:

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Originally posted by sbc350gearhead
Pushrod engines usually get better fuel economy than a DOHC engine of the same displacement.

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That's an interesting idea, can you give an example, you must also consider power out-put.

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The new Malibu's 3.5 has more power and better gas mileage then Toyota's 3.0.

-T

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problem is, the Toyota 3.0L v6 is 10+ years old. The comparable GM v6 in 1993 was the (bark, bark) 3.1..... ?

OK, that was tacky... let's move up to the GM 3.8L...~20% larger displacement (than the TMC 3.0) and and STILL less HP.....

how many ways can you spell dog???

fast forward to something not 10 years old...

The Toyota 3.0L has been replaced by a 3.3L v6. Which STILL puts out more power (225hp/240#) than the Malibu's "new" 3.5L (200/220#).

and... is still smaller.... [/QB]

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Ok....The 3.5 liter in the malibu has 200 HP and the malibu is about 3400 pounds. With a 4 speed automatic is gets about 32 MPG and goes from 0-60 in a hair under 8 seconds. The toyota camry has 225 HP, and weighs about 3400 pounds. with a 5 speed automatic, it also goes from 0-60 in a hair under 8 seconds, and gets 29 mpg.

A toyota tundra with a 4.6 liter V-8 gets has 282HP and gets 18 mpg. A chevy silverado with a 5.3 liter V-8 has 310 HP and gets 18 mpg, even though the chevy is a much larger and heavier truck.

This isn't my opinion. The same traits that give a DOHC engine an advantage at high rpm, also make it a disadvantage at low rpm as far as torque and fuel economy are concerned.

[ December 14, 2004, 09:01 PM: Message edited by: sbc350gearhead ]

 

[hone eagle]

Iam not old enough to remember the early days of engines(ww 1) but i have read that the first motors were ohc and mechanical injection! both very crude iam sure but the only logical way the first designers could make them run.just before the next war they found a wonderful answer for the frontal area problem for air craft-pushrods-then the english solved another problem -radiator drag- with carberation(atomization cooled the engine).See so nothing is new tech.My cousin from europe tells me my truck(7.3l) would be taxed for displacment to the tune of 2500 euro's a year.you see after the war the goverments over there protected the new car industry ( and fuel reserves) by locking out the american cars with their big displacments,as they got back on their feet and need bigger faster cars the tax was still in place(any chance it would be recinded? HA) so they compromized with more revs simple.given the choice they would have bought our cars,i know my dad wanted one.I also owned a Fiat in my student days(no *** cars imported yet) hated 4000rpms at 60 mph but thats what they had to put up with and still do.

 

[XENON12003]

A good pushrod Mustang.

Models:
Sandee Westgate and Amanda Lex

http://musclemustangfastfords.com/features/0410mm_max/

 

[brianl703]

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Originally posted by sbc350gearhead:
The same traits that give a DOHC engine an advantage at high rpm, also make it a disadvantage at low rpm as far as torque and fuel economy are concerned.

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Ford's 2.5L and 3.0L Duratec engines, which are DOHC engines, make 75% of max torque at 1500RPM, according to a press release they issued years ago. I've no idea how this compares with other DOHC engines.

On a dyno, these engines show two torque peaks. One before the secondary intake runners open at around 2500RPM, and one after the secondary intake runners open at around 5500RPM.

The secondary intake runners feed the secondary intake valve. Below about 4000RPM, the secondary valves are closed off. It gets no air. All air goes through the primary intake valves. Above that speed, the air enters the engine through both the primary and secondary intake valves.

The intake manifold for this setup looks like a coil of snakes!

 

[sbc350gearhead]

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Originally posted by brianl703:

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Originally posted by sbc350gearhead:
The same traits that give a DOHC engine an advantage at high rpm, also make it a disadvantage at low rpm as far as torque and fuel economy are concerned.

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Ford's 2.5L and 3.0L Duratec engines, which are DOHC engines, make 75% of max torque at 1500RPM, according to a press release they issued years ago. I've no idea how this compares with other DOHC engines.

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That is actually quite good for a DOHC engine. Some DOHC engines have a much broader torque curve than others, but most of those are lower HP output models. IIRC the LS-1 based V-8's have 90% of their torque from 1500 rpm until redline.

I am not trying to badmouth DOHC engines, as I do believe that they have their place (I even own one), but I cannot write off pushrod engines, as they are proving everyday that they can run with the 4-valvers. I think that you will see the death of the pushrod engine on the same day that you see the death of the DOHC engines, since auto manufacturers are dumping huge amounts of money into developing computer controlled electric solenoids to control valve actuation, which will take engine performance and fuel economy to a new level.

[ December 14, 2004, 11:53 PM: Message edited by: sbc350gearhead ]

 

[cruzan]

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Take the old 5.7L LS1 OHV vs Ford's 4.6L DOHC motor..

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The Ford engine is at a 69 cubic inch disadvantage...a 20 percent difference is more important than where the cams are located.

By the way Ford had an overhead cam V8 long before any Japanese company, and before you say the very limited Lexus LS400 came out 1 year before mass produced Ford modular remember the Ford 427 single overhead cam V8 from 1965.

To those who say the pushrods limit port size, and valve angles please remember the Ford 351 Cleveland's ports, or the big block chevy's or the original Chrysler Hemi's, all from the 1960's and all are legendary power producers.

For extreme high RPM use (over 7000) the overhead cam design has the advantage but 90% of the time an average passenger car or truck is below 4000 RPM.

There is an old saying "horsepower sells engines but torque wins races."

 

[Bret Chase]

[/QUOTE]The Honda GC OHC lawn and garden motors are terrific, though they do seem to be an exercise in engineering. [/QB][/QUOTE]

My dad's partner has a serious hard-on for honda motors, so pretty much every piece of power equipment (generators, pumps, etc)has a honda motor on it. in short, I HATE THEM!... both generators (an EU1000 and a 5000EX) are the oil burning-est, gas slurping, no running pieces of over priced crap that I have ever seen. the EU1000 has been rebuilt twice by the local honda dealer... put it this way, you don't need to worry about mosquitos around it. the 5000EX breaks down about once a month and needs about $200 of work each time... completely unacceptable for a $2500 generator. our concrete saw is alright, but it doesn't get run enough to break down... yet he still swears by Hondas... if it were me, I'd dump them all and put small diesels in everything... there's nothing like a 6000 watt diesel generator that'll go 30HRs on 5 gals of fuel... our honda is lucky to go 8.

-Bret