The Way I Think It Works
 

There is not that much that can be done to a stock engine manage system. You can buy Hot Rod systems but they still must follow EPA rules to be legal. And you can get really lost in one. Shutting down the EGR valve will give a boost in mpg by letting the fuel burn hotter, but that make the no2 gas go up. Out side of L.A. that's not that big a deal. .Going to smaller tires will cut rolling resistance. But the tires will not carry the same load. And will not stop as good. May 2006 Road and Track's pg 105 "Your Mileage May Differ" is the most up to date thing I now of. It goes along with what I made up my own mind to. That's why I like it, right. Do you guys know about holding down revs? Over the road truck drivers have long known to us use low a rpm as possible. Call it short-shifting, shift as soon as your motor will let pull the load. About %7 of a airplane motor is lost to pulling air past the throttle. They up the airs heat to reduce its density and open the throttle to make up for it. I knew that the more the throttle was open the less power was lost. but R&T says you can save %20 in city driveling driving. If your in front and can open up as you get rolling. Open up all the way, or as much as you can. Don't creep up to the speed you are going to run at. Weight maters most when you are speeding up, no news there. but R&T says 100 pounds added to 3000 pounds adds only %1.5 fuel use. More in stop and go, less on the road. Weight ups rolling resistance, but not that much, they say. .Also hybrids spin there motor up and then add fuel and spark. That's not why other cars do. They add fuel from the starter on. That does waste gas and wash the oil off. I read someplace that almost any start is a cold start to the engine manage system. I know that heating the air worked in carburetors, and engine manage systems use air temperate for setting how much gas to use. the hotter the less. But how it will work now is something I don't know. Also it will add to engine detonation. So try and add a cold air intake when power is needed.

Source?

I wouldn't base all of my view on fuel efficency on a single Road & Track article. Good rigorous testing is the only way to know for sure what will work and what won't.

So bust out the Scanguage and start testing, because that will be the only way to really make up your mind.

Andrew, even our wonderful ScanGauges shouldn't be above some scrutiny. Heck... it only just got a workaround to deal with DFCO. ;)

I agree with Andrew. You can read through article after article, but what do you say when you see a car rated at 37 mpg highway getting over 50 mpg? The members here prove that it can be done, and they'll help you to improve your mileage too.

Engine Management Systems
 

Dan's comments are contradictory in a sense. Probably the second best thing that I have done with my DiabloSport Predator programmer is to reduce the speed at which the transmission shifts (short-shifting), with the absolute best thing being a 100 RPM reduction in idle speed. I just wish that I could change the commanded Air/Fuel Ratio from 14.7 (lowest emissions) to 15.5 (best efficiency) with the same tool, but sadly the EPA has a lot to say about that.

Wayne




...There is not that much that can be done to a stock engine manage system. You can buy Hot Rod systems but they still must follow EPA rules to be legal. .....
... Call it short-shifting, shift as soon as your motor will let pull the load.

Wha? Smaller tires - everything else being equal - have higher rolling resistance....

Well actually he said smaller tires.
I think he should have said skinnier tires, which seem to help FE but probably due to less aero frontal area. Maybe due to less road contact rolling resistance, but the higher pressures most/many of us are running kinda does the same.

Anyway, I think DAN needs to read the stickies first and get an understanding of what we have here first before becoming an instructor.

Fair enough... I'll edit my post (but larger diameter = less RR)...

Science vs. Speculation
 

First, Road and Track is not a Scientific publication. The consensus here is to support claims with multiple citations of tests with Scientific merit, or to conduct one's own tests using proper technique.

Mr. DAN, I believe you are on a slippery slope with such speculation.

Please respond to this thread to confirm or deny these claims.

On the issue of testing, the best instrumentation we have (available in mass), is the ScanGauge. True, it is not perfect; however, by using the instrument in simple tests, it is entirely possible to isolate a variable to gather data, and publish the experiment for others to attempt.

As a reminder to all who have forgotten or are not aware, please see this quick definition of the "Scientific Method".

RH77

i used smaller meaning like 175 to 155.
 

smaller tires cut rolling resistance". i used smaller meaning like 175 to 155. not tallness"smaller tires w

what was in Road and Track was what i have read and used for years. not just one r&t.
i have some doubt about what people are finding on their own. i know it is very hard to get a true mpg using gas station pumps. with out counting many fill ups the difference in the pumps cut off may have a big effect. as does wind and where it is driven. i try and go by standard engineering practice. and i know i can be wrong. i have made more power in my motors and on some made much better mpg. like with a self adjusting carburetor with a working water injector to stop knock as needed on its own.

i talked about Air dams keeping the air out from under the car. jim hall cam up with them. the deeper the better. i was always going to make a spring loaded one. when driving around a low speed it would stay up out of the way of curbs and driveway dips. air on part of it would push it down with speed.. cars like the old z-28s had a problem with damage at low speed. too lazy to do it.

Shutting down the EGR valve. well i've done it. it works , but maybe not on cold days. the heat may help. with faster warmup if nothing else. the erg and a lesser ignition advance is how nox is cut. the lower combustion heat cuts nox by heating the nitrogen in the are less. that was the big reason cars sold in America got less power and mpg than where they were made. a ford made in England was sold with a 1100 cc motor. here it first used a 1400 cc. motor. (i think)

i am just trowing out ideas to be talked about here. not spiting on the flag. i spent my live in shops and have the burns and marks to prove it. maybe i talk different. but that's not putting anybody down

I know that heating the air worked in carburetors, and engine manage systems use air temperature for setting how much gas to use. the hotter the less. But how it will work now is something I don't know. Also it will add to engine detonation. So try and add a cold air intake when power is needed. no i never got around to it on new cars. could not find the room on mine.