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cam timing for gas mileage?

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cam timing for gas mileage?

Postby bc » Tue Apr 25, 2006 8:55 am

How would cam timing change if gas mileage was number 1? What is the biggest effect on gas mileage when looking at a cam; duration, lobe seperation, center line, or lift? I know that the new cars have small duration numbers and high lift with wide lobe seperation like 118 or more, are those cam specs used more for gas mileage or emissions?
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Postby Cobra » Tue Apr 25, 2006 10:05 am

Increasing lobe separation reduces overlap, increasing low rpm torque at the expense of high rpm power. This is good for engines with limited compression and can increase gas mileage. Newer, asymmetrical cam profiles open valves quickly and let them close gently. Asymmetrical cams have different ramps for opening and closing. Most gas mileage gains are made by advances to piston, ring, cylinder, and head packages. OHC's lessen problems with cam location, valve train angularity, valve train weight, friction, and reliability. Low friction coatings can also lead to better gas mileage and longer engine life. Given equal engines, lighter weight vehicles achieve better gas mileage. A new Corvette will easily get 25 mpg on the highway!
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Postby bc » Tue Apr 25, 2006 10:24 am

I have noticed that alot of the new engines use alot more exhaust duration (10+ degrees more) is that done to help with the high rpm power or is that emissions related?
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Postby Torquemonster » Tue Apr 25, 2006 9:51 pm

Can't help you on the specifics you ask - but I can tell you that I've seen surprising cruise economy on some rather largish cams - which kills the theory that a performance cam can't get reasonable mileage.

LPE Corvettes were famous for making over 500hp and 30mpg

I've seen a Viper make 580rwhp (yes at wheels) yet return 28mpg out of 488 cubes of V10 - all motor. 1000rwhp twin turbo Vipers can be tuned to make 30mpg. These cars are running around 0.600 lift on 1.7 rockers

The cams are likely to fall within the 112 range - I don't think 118 is necessary. You 'll get better gains by going to low impedence injectors and fine tuning the air/fuel and timing for cruise than simply a cam.

Mpg is a combination of many things working together as said earlier in effect . If all it took was a small cam - a truck gas engine would get great mileage at cruise... they don't - a good performance motor can out mpg them on a trip and out power them in their rpm range... just not beat them from idle to 3000rpm.

I'd start with fast opening ramps, lots of lift, duration @ 0.050 to run the rpm range you want, and keep LCA around the 112 with injection. Asymetrical is good for most combos - except where you have exhaust ports more efficient than the intakes.

If you want almost free extra mpg - add pure acetone to every tank at a 0.2% dilution. Change fuel filter first, then again after 2000 miles. While many will laugh - you'll be amazed once the crap clears out. I got 6.5mpg out of that trick and more power to boot. No down side except it takes longer to fill up and I need a calculator each fill up... so what - gas is well over US$4/gal here and I save enough adding acetone to take my wife out an extra time every month instead of paying the oil tyrants.

btw despite oil industry paid naysayers - the acetone tip came from a top chemical engineering expert who swore by it and had done so for 30 years. My results are typical not unusual - but it took me almost 3500miles to get the full benefit... that's how long it took to fully clean itself of carbon in my case - usually 2000 is enough. I only gained 1mpg at the start, but the power gain was on first tank.

Why it works?

It changes the surface tension of diesel or gas. That tension change is enough to make the fuel burn cleaner and faster. That's the short answer.
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Postby Torquemonster » Tue Apr 25, 2006 9:57 pm

to clarify - the above 6.5mpg was the INCREASE! NO changes in driving style.

re diesel - change dilution to 0.147% - that's 0.147 of 1%... so we're talking literally a few cents per tank to gain what for me was a 25% mpg gain while picking up 5kph top speed - and 10kph gain between my acceleration test markers - a noticeable power gain I can feel.

If you add more than 0.2% gas or 0.147% diesel - there is no further gain to be had - the graph of benefits peaks right there then drops off.
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Postby LilRacr » Wed Apr 26, 2006 12:03 pm

Torquemonster,
This can be done with late model cars and will not hurt O2 sensors?

The .2 dillution is per gallon?
-Bobby-
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Postby jacksoni » Wed Apr 26, 2006 12:33 pm

Have seen this acetone thing in lots of places, seems sometimes works, sometimes doesn't or less so. Mostly impression rather than good A-B-A testing. However, sounds like worth a try with the recent 30cent jump in gas last week. Torquemonster's 0.2% is right at 1 ounce Acetone in 4 gallons of gas. And the folks who push it say nothing detrimental to fuel system. Just don't tell anyone if you go in for a warranty fix melted something. :lol: That right T?
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Postby Cobra » Wed Apr 26, 2006 2:40 pm

bc- I sometimes use a lttle more exhaust duration with a heavy car.
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Postby Torquemonster » Fri Apr 28, 2006 1:36 am

LilRacr wrote:Torquemonster,
This can be done with late model cars and will not hurt O2 sensors?

The .2 dillution is per gallon?


To be honest I have not encountered anyone that had a problem with O2 sensors - I'd have thought the cleaning action would keep them good - but I guess it is possible the crap coming off the fuel lines and tank and the de-carboning of the induction system might affect some O2 sensors that...

to me it would be a small price to pay if so at gas prices now.

the dilution for gas is 2ml per 1000ml or 2ml per liter... sorry I don't have the conversion for that on hand to US gallons....
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Postby Torquemonster » Fri Apr 28, 2006 1:46 am

jacksoni wrote:Have seen this acetone thing in lots of places, seems sometimes works, sometimes doesn't or less so. Mostly impression rather than good A-B-A testing. However, sounds like worth a try with the recent 30cent jump in gas last week. Torquemonster's 0.2% is right at 1 ounce Acetone in 4 gallons of gas. And the folks who push it say nothing detrimental to fuel system. Just don't tell anyone if you go in for a warranty fix melted something. :lol: That right T?


lol

1 ounce per 4 gallons sounds about right - hardly enough to give even rubber fuel parts (for the older cars that still have them) a concern. If they fail at 0.2% they were probably going to anyway.

the testimonial vs science debate is a murky one. Many give up too soon and say it didn't do much.

I doubt that the latest super high fuel pressure common rail diesels would get the same mpg gains the older lower pressure diesels get - but have no clue as I have not tested one. Logically I'd say the older cars would gain more than a new one too.... but again - only one way to find out.

There should be a power gain in all however (in theory) as pump gas/diesel quality sucks for ALL vehicles - anything that enables it to burn more completely is going to help power.
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Postby Keith Morganstein » Fri Apr 28, 2006 4:16 am

RE: use of additives for mpg increase.

Lets see some BSFC numbers, otherwise it's complete HOGWASH.
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Postby hydra » Fri Apr 28, 2006 5:56 am

I second that motion
There are a number of mechanical devices which increase sexual arousal, particularly in women. Chief among these is the Mercedes-Benz 450SL. --P.J. O'Rourke
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Postby JCR » Fri Apr 28, 2006 10:10 am

Torquemonster wrote:If you want almost free extra mpg - add pure acetone to every tank at a 0.2% dilution. Change fuel filter first, then again after 2000 miles. While many will laugh - you'll be amazed once the crap clears out. I got 6.5mpg out of that trick and more power to boot. No down side except it takes longer to fill up and I need a calculator each fill up... so what - gas is well over US$4/gal here and I save enough adding acetone to take my wife out an extra time every month instead of paying the oil tyrants.

btw despite oil industry paid naysayers - the acetone tip came from a top chemical engineering expert who swore by it and had done so for 30 years. My results are typical not unusual - but it took me almost 3500miles to get the full benefit... that's how long it took to fully clean itself of carbon in my case - usually 2000 is enough. I only gained 1mpg at the start, but the power gain was on first tank.


:roll:
The acetone thing is a bunch of BS peddled by some hack by the name of Louis LaPointe at http://www.lubedev.com/articles/additive.htm Of course none of his work is peer reviewed. It's geared for the gullable types who buy Slick 50 and other such trash.

Acetone has been debunked here http://www.ece.kettering.edu/news/archi ... orynum=406
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Postby Torquemonster » Sat Apr 29, 2006 7:17 pm

When a double major scientist with 2 doctorates tells me it is impossible to run an ICE on water - and I've just spent some time with a guy actually doing it - and who has had a film crew filming his activities for 12 weeks.... who also KNOW not THINK that it works

I say the dr is a moron. The world of experts is full of morons whose quest for knowledge is limited to confirming what they already hold dear, and to whom new ideas are to be violently opposed.

morons

so when those who do not have doctorates say hogwash etc to real world actual not imagined results - we both share the same opinion of each other on this matter. i.e. we can agree to think each of other as morons.

if that offends - tough - I'm speaking from real world knowlege and experience you are speaking from something you read on the internet and not from real world experience.

Test it for 5000 miles on several vehilces and get back to me - until then - you are a moron trying to speak with authority about why something will not work.

I'll take my 32.5mpg that used to be 23mpg and leave you experts to argue over why that happened.... acetone was directly worth 6.5mpg of that - the rest is a result of other things that did not involve changes in driving style or tuning.

you may come up with 100 different explanations - all of which will be wrong. But you will feel better because thinking I'm a fool must mean you are right.

I'm done on this topic - 95% of ICE experts are morons on anything outside the square of their own learning. I've had engineers work for me for a long time - less than 5% can actually be taught anything outside their box - the rest follow the line of trained thought their learning gave them. They are useless to me for R & D.
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Postby Keith Morganstein » Sun Apr 30, 2006 4:41 am

Torquemonster wrote:
so when those who do not have doctorates say hogwash etc to real world actual not imagined results - we both share the same opinion of each other on this matter. i.e. we can agree to think each of other as morons.

if that offends - tough - I'm speaking from real world knowlege and experience you are speaking from something you read on the internet and not from real world experience.







The world is full of fuel mileage claims and related anecdotal stories,
Most of them are HOGWASH!

I have an open mind, but not a gullible one. All I demand is proof.

BSFC: (brake specific fuel consumption) the pounds of fuel it takes to make one horsepower for one hour.

Prove the claim on the Dyno or you have nothing but another fantasy.
"Nil Satis Nisi Optimum"
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