Pros and cons of 4 valve engines

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Old 08-30-10, 03:49 PM
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Pros and cons of 4 valve engines

Any comments regarding power, gas mileage, engine longevity, servicability of the upper half of the engine, cost of repairs, and whatever else comes to mind?

My dad had 2.4 liter 16 valve 4-cylinder that took off like a jack rabbit. That is the only vehicle I have ever driven that had the 4 valves per cylinder.
 
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Old 08-30-10, 05:21 PM
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i shall be chastized by the pundits, but i came across, about a year ago, an interesting read. guy speculated what kind of engine would have been the best for drag racing. his conclusion was: large 4 cyl. he had some math to prove it.
all i recall from that is that a light 4 cyl, due to momentum laws, is easier to pick up and take off. less metal to move, less inertia to overcome.

ok, now you can beat me up.

otherwise, look at street racers. what is the golden standard? civic 4 cyl dohc 16 valve?

look at the european engines, historically and as of the latest developments. small turbo charged 4 cyl, direct injection, dohc?
you know what gas mileage do those get? don't want to make you envious. VANS do around 69. passenger 4 seaters do anywhere between 70 to 90. yes, it's on imperial gallon, yet....

of course, there is no such thing as summer and winter formulated gas in europe either...
 
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Old 08-30-10, 05:28 PM
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Originally Posted by ukrbyk View Post
look at the european engines, historically and as of the latest developments. small turbo charged 4 cyl, direct injection, dohc?
you know what gas mileage do those get? don't want to make you envious. VANS do around 69. passenger 4 seaters do anywhere between 70 to 90. yes, it's on imperial gallon, yet....

of course, there is no such thing as summer and winter formulated gas in europe either...
Hmmmm. This begs for more info on this, and the conversion to U.S. gallons. Then I guess if the mileage is more substantial than our engines, we have to get into the politics of why this is.
 
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Old 08-30-10, 05:34 PM
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Heck, mount a Merlin v12 to a dragster frame and see what happens. It was light enough to be a part of the airframe of the P-51 Mustang, so it shouldn't be too terribly heavy an engine. Gas mileage.....dragster.....who cares?
 
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Old 08-30-10, 06:47 PM
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ukrbyk...I'd sure like to see some stats. If you compare small turbo diesels (common in EU) to normally larger gas engines (more common in US)...thats not valid.

I don't know whether a UK gallon is the same as Imperial...(I think it is?)...but UK is actually more than US if true.

So gotta watch the reports for acurate conversion.

Not arguing...just curious.
 
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Old 08-30-10, 07:34 PM
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Mazda Rx7 with it's Wankel engine. NO valves. OK that was just off topic.
Animated Engines, Wankel

 
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Old 08-30-10, 07:35 PM
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Originally Posted by Gunguy45 View Post
ukrbyk...I'd sure like to see some stats. If you compare small turbo diesels (common in EU) to normally larger gas engines (more common in US)...thats not valid.

I don't know whether a UK gallon is the same as Imperial...(I think it is?)...but UK is actually more than US if true.

So gotta watch the reports for acurate conversion.

Not arguing...just curious.
i totally understand. i had that chart, European - i think, British - cars mpg around 1.5 year ago. i was then member in mpg forum, and someone posted it. mileage was outrageously better, later i figured that it's based on imperial gallon.
1 Imperial gallon = 1.20095042 US gallons
but even with that, it was mind boggling.

i'll try to find it. i have not been to that forum in long time.

if you think about it, though, it's market necessity. at European cost of gas, no one will buy cars doing 20 mpg. well, most of consumers.
 
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Old 08-30-10, 07:59 PM
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Top 10 Fun, MPG-Friendly Cars You Can't Buy In America—Yet - Popular Mechanics

not sure if it's based on imperial gallon; if not, then it needs to be multiplied by 1.2, so, for merc e-class, 50 x 1.2=60mpg for imperial.

btw, you know that Jeremy Clarkson did 69mpg on a 12 cyl Jaguar this spring? they ran on sealed gas tank from France to a city in Britain. he outperformed VW and something else, forgot what it was, in 4 cyl realm, and he was flooring it for the 1st half od the drive.

Anyone know why cars sold in countries like the UK get so much better fuel economy than those sold in the US? Even after i convert MPG from imperial gallons to US gallons, the MPG is still off the chart compared to US sold vehicles. Any thoughts?

A BMW 5-series ain't light, yet it averages better mileage than a Prius. And it's got over 100 HP more.


The correct answer is: different ECU mappings, which lean the mixture at the speeds and in the conditions that are used as reference for respective mileage tests in EU and US. This is the reason for different mileages in the "same" (yet EU/US) vehicles.

The other thing is, Europe has to pay much more for a gallon, so fuel-efficiency is a crucial issue here.


Car Talk

i think i either found it, or something similar. still looking for that one with van in it doing 69mpg.

US Gas Prices

Study: European variants of US cars average 60% better gas mileage by Steve Austin - 2007/06/04

The base model Ford Focus gets 37 MPG in the US, which is pretty decent mileage. But it gets 59 MPG in Europe which is 60% better gas mileage!
Today we compare the mileage of 8 base model compact cars available both in the US and in Europe. Cars in the study consist of US models equipped with economy, no-thrill engines and their European cousins equipped with diesel engines. Each US/European car only differs by the engine. Other than the engines, cars are identical. GT/sports models and Hybrids are excluded from the study to keep it fair.
Across the board, European models get an average of 52 MPG versus 32 MPG for the US version of the same car. So the same car on European roads gets 60% better gas mileage than on American roads.

Interestingly this 60% difference is not limited to the Ford Focus which gets the best mileage of the set, the difference averages also 60% for all cars. The difference is widest for the BMW 3 series: gas mileage on the European 1.8D is 80% better than on the smallest gasoline engine offered in the US (BMW 328).

So you may wonder: "How do the engines differ?"

European cars are powered by turbocharged "common-rail" diesel engines. This type of engine has been widely used in Europe for the last 10 years. They don't need spark plugs, run on diesel fuel including bio-diesel and have a high compression ratio of 17 to 25:1 versus 9:1 found on a typical gasoline engine, making them that much more efficient. And by the way, did I mention that they run on bio-diesel as well?
US car manufacturers attempted to produce diesel engines in the 80's but failed. They used standard engine blocks designed for gasoline, not for these high compressions and as a result the blocks cracked. Ever since diesels have had bad reputation in the US while they equip most cars in Europe and are highly reliable.
Now you may ask: "When will Ford or Chrysler bring their diesel compact cars to the US?" This is a very good question. After all the big 3 are loosing double-digit market share every quarter to more efficient car makers. Shouldn't it be time for them to react and bring these diesel compact cars in the US? American companies already make them for goodness sake!

Well you'll be suprised but they have no plan to do so. For the time being US consumers will have to choose between the Volkswagen TDI and the Mercedes-Benz E 320 diesel

(chart does not want to copy)

of course, there's infamous case of Ford Taurus size car, designed in the USA, back around 20 yrs, doing 62mpg, and never gone into production.

now, that's 2007 study. ever since, they started using DI gas engines. it was question of getting high pressure pumps for those, capable of providing enough gas pressure for stratification. DI gas engines get even better mpg, as far as i know, than what was in 2007.

A Yaris 1.4 D-4D won the European ALD World Fleet MPG Marathon, averaging 70.49 mpg over the 400-mile fuel-efficiency road race.

The Diesel Polo can't boast much in the way of speed or backseat legroom, but its 1.4-liter 3-cylinder engine accomplishes impressive economy, which VW claims to be around 60 mpg

IN Italian, lupo means wolf, but for much of Europe it also denotes the smallest car in Volkswagen's litter. The Lupo 3 Liter TDI is also VW's most efficient. ''Three liter'' stands not for engine displacement or size, but for fuel efficiency: three liters per 100 kilometers in European measure, or 99 miles a gallon.
 
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Old 08-31-10, 04:48 AM
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But going back to the original question, one of the primary reasons for four valves is to increase "breathing" area - size of intake and exhaust - without having to make the single valves so big as to be impractical. Among other things the two smaller valves are each lighter and therefore less likely to "float" at high rpm.
 
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Old 08-31-10, 06:27 AM
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Better breathing is always better therefore 4 valves are better. More parts on an engine and more initial cost and more things can go wrong though.
American cars have strict emission laws.
Back in mid 70s cars were getting 12 mpg and doing 1/4 miles in 19 seconds and going in for tune ups every 6 months.
Tough emission laws are still in place put computer control has helped alot.
If a country did not have to follow emission laws power and fuel economy would be increased.
 
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Old 08-31-10, 06:23 PM
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An NHRA naturally aspirated Pro-Stock 500 cubic inch two valve per cylinder engine will make fourteen hundred horsepower and rev to 10,000 RPM. Two valve engines obviously make power. However, as with any engine it's a matter of where and how that power is made.
 
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Old 09-01-10, 04:01 PM
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Originally Posted by frankiee View Post
If a country did not have to follow emission laws power and fuel economy would be increased.
I thought one of the ideas of emissions laws was to squeeze more out of each gallon rather than send carbon waste into the air. ???
 
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Old 09-01-10, 04:12 PM
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Originally Posted by ASE MASTER View Post
An NHRA naturally aspirated Pro-Stock 500 cubic inch two valve per cylinder engine will make fourteen hundred horsepower and rev to 10,000 RPM. Two valve engines obviously make power. However, as with any engine it's a matter of where and how that power is made.
Obviously.

Yet we know the mfger just didn't make dual head cam engines for no reason. Either they generate more power, overcoming their obvious additional drag due to more moving parts, or they save gas - or maybe both? But it was the sporty type cars that seemed to get the dual overhead cam and I assumed this generated more power per cube without having a turbo or super charger.
 
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The U.S. standards and emissions requirements are not that tough. A European inspection is often so strict, there are few backyard mechanics that have a hard time meeting the annual 1 or 2 day inspection.

Turbos are used to get more efficiency and 4 valve engines can breathe better. After that, the limits are usually the exhaust situations since that can limit the amount of air going through.

High performance engines in European cars are often twin turbos with a tuned dual exhaust system and larger diameter. There are 2.4 liter (150 cubic inch engines) V8s that can put out 500 hp if the turbos are needed, otherwise they are quite normal. The good European cars are not for back-yard mechanics because of the sophistication.

Most of the really good cars are not exported to the U.S for marketing or business decisions, but they can be bought there and shipped back and often lights or some glass is replaced because it is made and tested to a different standard and the car manufacturers do not think it is worth the testing and certification if they do not market in the U.S. The exotics - Ferrari (owned by Fiat), Lomborghini (owned by Audi) and Bugatti (owned by VW/Porsche) are exceptions since the are high buck custom cars and can charge what they want to cover the certification.

Dick
 
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Old 09-01-10, 05:01 PM
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Is there a major penalty of some sort if we go to Europe, buy one of those cars and bring it over here? Be very tempting to do so if one can afford it.
 
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Old 09-01-10, 05:33 PM
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Originally Posted by Concretemasonry View Post
Turbos are used to get more efficiency and 4 valve engines can breathe better.
So naturally that begs the question - what does better breathing then accomplish?

Dick, if you were a mechanic for 66 years, your brain may have exploded by now. You are good at providing some interesting information.
 
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Old 09-01-10, 06:01 PM
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NEsportsfan -

Beyond the minor adjustments or modification to comply with unique different standards. As an example, the glass must be branded/etched to meet the U.S. and the European standards are not accepted here because of the expenses. The other penalties are the shipping cost and the duties, which are less if the car has enough miles on it and the time/cost involved in getting to the delivery point.

I bought a VW (made to U.S. specs), picked it up at a factory dealer, drove it 2500 miles and had it shipped back. At that time, there was no duty because of the mileage, but I had to fly to get to south Chicago where it was stored and held for a certain time period before being charged a daily fee. I immediately got to gas station to fill up with cheap American gas and drove it home all in the same day. Not a bad experience and sure cheaper than renting a car in Europe.

EC -
Have been an engineer for 35+ years and a car fanatic for about 55 years. I enjoy a good dirt track race or a Formula 1 race and hate the NASCAR races in tanks that are built to put on a good show for TV. Formula 1 is fun to see in person a few times, but better on TV since the good tracks have hills left and right turns and speed does not win races because the handling and brakes and the cars are voluntarily limited to maximum RPMs (17,000-19,000) determined by the team manager. Dirt is great because you can see it easily and sit near the family of the owners in the few bleacher seats. - I have been lucky to live or be at the right place to find good racing. Now I plan to be at the new track at Austin, TX for the return of the annual U.S. Formula 1 since it was determined a few years ago that the track (modified Indy infield) did not attract enough attention or market, so the race dates went to better markets like China, Indonesia, Japan in addition to the old tradition like the European ones like the last one was in Belgium, but even if tickets were available, the cheap ones were $375.

Dick
 

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Old 09-02-10, 08:13 AM
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Dick,

NASCAR tanks? You mean the cars? If so, that is my choice of motor sports since these seem closest to real cars we drive. Those other rigs things seem like souped up go carts, IMO.
 
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Old 09-02-10, 10:01 AM
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The NACAR cars do not at all resemble real American cars except for the nameplates. Since they are always having body damage, the cosmetics can be replaced easy or it can be re-skinned to change the brands, which has been done quite a few times.

The frames and suspension are totally different than a normal car since they are designed to only turn left, except the few that are also made for road tracks. I call them tanks because they are crude, built to bounce off another car and are heavy. There is only one Formula 1 race per year in a country but you always see some good circle racing at dirt track if there one near you. Some even have races that include the small displacement 4 valve engines. At least the tickets are not expensive as Formula 1 by any measure. For the cost of a Formula 1 car you could buy 5 to 8 NASCAR tanks.

Dick
 
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