Gas Efficiency

I've heard that cold air and short ram air intakes can increase gas mileage, is this true, and if so by how much? Also, which will produce better gas efficiency results. And is it true that short ram is louder?

Also, I've heard headers increase gas mileage, again, is this true and by how much?

And finally would something like this really work, or am I getting screwed if i buy this: http://www.autopartswarehouse.com/performance/brand.php?makeid=26&modelid=262&year=2000&partid=8443?

PS Any other tips/ parts/ things i could do to up gas mileage is greatly appreciated, I commute over 50 miles a day.:banghead:

PSS Also if the tornado thing does work, is there any point in getting it if I purchase an intake?

PSSS I did read the post on gasoline, but what is the general consensus concerning buying the higher grade fuels, do they get more gas mileage, and if so is it enough to jusitfy the higher cost?

Alot of misconceptions here.

First off let's start with the Tornado. It is a POS. Don't waste your money. If you do a search for 'Tornado' you will find this topic has been beaten to death.

Second, it is a common myth that people seem to believe that higher octane affords you more power or better fuel economy. This is simply not hte case, higher octane has one purpose, to prevent pre-detonation (aka knock).
I would suggest reading this thread (http://www.automotiveforums.com/vbulletin/showthread.php?t=452830), both the first post on the first page, and the last post on the 2nd page.

Another widely repeated myth regarding fuel economy is that intake and exhaust mods will help. A cold air intake's purpose is to bring in cooler air from outside the engine bay. This decrease in temp means more oxygen content in the air. However, when the car's computer (ecu) reads more oxygen, it sends more fuel. So mods like this, while they may add some power, can actually reduce fuel economy. Granted, if they reduce restrictions in the flow of air, then they may in fact help, but this is a secondary effect. As reducing restrictions with these mods is mainly done for more power, and generally if you have more power, you are probably using it, and not driving slowly to conserve gas.

This thread (http://www.automotiveforums.com/vbulletin/showthread.php?t=558623&highlight=fuel+economy)covers this topic pretty well.



Basically, if you want better fuel economy, the trick isn't to spend more money on more expensive gas, or cheap marketing gimmicks, or modifications, but to do the smart free stuff.

a) check your tire pressure, underinflated tires are one of the biggest things people overlook. The lower the pressure, the more friction with the pavement, which has a negative effect on fuel economy

b) driving habits, is the 1st or 2nd biggest thing. Learn to shift lower, accelerate slower, and keep a drive slower (the faster you go, the more power is needed to overcome drag and wind resistance). I drive my sports car hard, average on the highway with my spirited speeding is 360 miles to a tank, I did a fun experiment and did the same highway drive with cruise control set on the speed limit, and the same tank lasted over 550 miles. So yes, driving habits, do have a HUGE impact.

c) turn off AC

d) reduce drag, close windows, remove anything like a stupidly placed pepboys wing that is acting like a parachute on the back of your car (if this applies to you).

e) reduce weight...don't carry a ton of stuff around if you dont need it in the car

You would really be surprised how little power is required to keep your car moving at a steady speed. But the more drag or resistance, which can either be a result of something on your car (wing/low tires/excess weight) or something int he world (hill, headwind) the more power needed, therefore the more fuel. The same applies to what speed you are traveling at...the faster you go, the power necessary multiplies exponentially. This is why you may only need to add 20hp to increase your car's top speed from 110-130, but you will need to increase it a few hundred hp to change the top speed from 180mph to 200mph.

So yeah, bottom line, reduce drag and resistance in any form, and don't waste money on gimmicks.

Cold air will reduce fuel economy. But through characteristics of the throttled petrol engine.

The throttle in a petrol engine causes large parasitic losses, it reduces the amount of air entering the engine by creating a pressure drop.

Colder (denser) air means the throttle has to be closed further, causing a bigger pressure drop for the engine to suck against which impacts on fuel economy.

Igovert covered well the basic steps to better fuel economy. Bolt ons are BS. If they worked then they'd be standard on new cars.

The best mod for increased fuel economy is your right foot.

Acellerate gradually, coast to stops, don't use A/C. You'll learn to fine tune your driving habits after practicing, just keep an eye on your fuel economy calculations to see what works best.

take the money you were planning on spending on bolt ons and buy a nice used scooter. 80mpg around town.

Or better yet....buy a bicycle.

There is kiwi said, there is no bolt on hot ticket. No snake oil that you pour in the tank. The only notable option is your driving technique and keeping the car in good shape (tires, engine maintanence etc)

I used to have a "fuel efficiency gauge" (I think it's in a box in the garage)....it was really just a manifold vacuum gauge, which is a fairly good indication of engine load. Medium vacuum (idle and moderate acceleration) was yellow. High vacuum ( cruise and deceleration) was green. Low vacuum (acceleration or high speeds) was red. You could make your own dial for an off the shelf vacuum gauge. your best fuel economy is when you keep vacuum high, that is: avoid aggressive acceleration, excessive speeding, and unneccessary downshifts. our feet tend to be somewhat imprecise, and we sometimes don't realize how far we have increased throttle. with a gauge to watch, i noticed throttle position a lot more.

and the other stuff....clean out crap, air up tires, keep engine in good shape.
don't fall into the trap of spending more money to save money. Many products brag about "a 5 or 10 % increase in mileage!" Do the math...how much would that really save you? You can increase your mileage that much or more by driving more fuel-consciously. As has been said, if any one product was SO AWESOME, they'd be putting one on at the factory! Manufacturers are under increasing EPA/CARB pressure to make good mileage numbers, don't you think they'd have tornado-like device already in the intake if it helped that much?

I used to have a "fuel efficiency gauge" (I think it's in a box in the garage)....it was really just a manifold vacuum gauge, which is a fairly good indication of engine load. Medium vacuum (idle and moderate acceleration) was yellow. High vacuum ( cruise and deceleration) was green. Low vacuum (acceleration or high speeds) was red. You could make your own dial for an off the shelf vacuum gauge. your best fuel economy is when you keep vacuum high, that is: avoid aggressive acceleration, excessive speeding, and unneccessary downshifts. our feet tend to be somewhat imprecise, and we sometimes don't realize how far we have increased throttle. with a gauge to watch, i noticed throttle position a lot more.

While a vacuum gauge is a good guide to how far open the throttle is, it's counter intuitive.

A throttle petrol engine is most efficient running very little vacuum. Have a look around for the BSFC map I've posted up.

While a vacuum gauge is a good guide to how far open the throttle is, it's counter intuitive.

A throttle petrol engine is most efficient running very little vacuum. Have a look around for the BSFC map I've posted up.

That's work-efficiency, not fuel mileage efficiency. Brake specific fuel consumption maps merely point out that at x RPM at 100% load your motor will get as much power from the fuel as it can, i.e. its using the fuel efficiently. This does not mean you will get great gas mileage.

The most efficent petrol engines would be quite small engines running very high compression ratios working at top work efficiency. But they probably wouldnt last too long if you're asking them to run at 90% of their top speed constantly. That's why diesels are better in every way.

That's work-efficiency, not fuel mileage efficiency. Brake specific fuel consumption maps merely point out that at x RPM at 100% load your motor will get as much power from the fuel as it can, i.e. its using the fuel efficiently. This does not mean you will get great gas mileage.

The most efficent petrol engines would be quite small engines running very high compression ratios working at top work efficiency. But they probably wouldnt last too long if you're asking them to run at 90% of their top speed constantly. That's why diesels are better in every way.

There is no difference between what you call "work efficiency" and what you call "fuel mileage efficiency".

For example, running a car in 4th gear at 100km/h will give more vacuum than running a car in 5th gear at 100km/h.
5th gear has a wider throttle opening and less vacuum, yet the engine is using less fuel, less air and turning at lower rpms.

If you want to know how much air (and/or fuel) is entering your engine then a vacuum gauge cannot help. You need to read from the air flow meter or fuel computer. Manifold pressure alone is useless.

I agree that a small engine running at higher load will give better efficiency, but not running at the 90% top speed that you claim.
The engine has to be sized to run near maximum load at a speed below peak torque for best BSFC.
Making an engine last while doing this isn't a problem. Convincing the consumer to buy a car with no reserve power will be.

I love you all, but I'm tired of hearing about "pumping losses". The bottom line is that you need to ingest a certain amount of air (and therefore fuel) to maintain highway speed. The less throttle you have open, the less air is ingested and therefore less fuel.

RPM plays a big factor as well, since the same throttle opening at a higher RPM will suck more air, but STOP TALKING ABOUT PUMPING LOSSES AS A FACTOR IN MPG! :) I love you all.

I love you all, but I'm tired of hearing about "pumping losses". The bottom line is that you need to ingest a certain amount of air (and therefore fuel) to maintain highway speed. The less throttle you have open, the less air is ingested and therefore less fuel.

RPM plays a big factor as well, since the same throttle opening at a higher RPM will suck more air, but STOP TALKING ABOUT PUMPING LOSSES AS A FACTOR IN MPG! :) I love you all.
Okay, I'll won't mention such things in this post.
But only if I can post my favourite picture again.
http://users.actrix.co.nz/dougal.ellen/bsfcmap.jpg

:grinyes:

There is no difference between what you call "work efficiency" and what you call "fuel mileage efficiency".

For example, running a car in 4th gear at 100km/h will give more vacuum than running a car in 5th gear at 100km/h.
5th gear has a wider throttle opening and less vacuum, yet the engine is using less fuel, less air and turning at lower rpms.

If you want to know how much air (and/or fuel) is entering your engine then a vacuum gauge cannot help. You need to read from the air flow meter or fuel computer. Manifold pressure alone is useless.

I agree that a small engine running at higher load will give better efficiency, but not running at the 90% top speed that you claim.
The engine has to be sized to run near maximum load at a speed below peak torque for best BSFC.
Making an engine last while doing this isn't a problem. Convincing the consumer to buy a car with no reserve power will be.

I don't know what kind of car you're driving, but i'f im tootling down the highway in fourth gear, i most definetley have to hold the throttle wider than in fifth gear.

*edit* Anyway, as i said before, your thoughts aobut BSFC does not relate to fuel mileage. Simply put, the best BSFC you'll get is when your at peak torque RPM at WOT. This means you will get the most power per pound of fuel = work efficiency. This does NOT mean you will get better fuel mileage by running at max BSFC, UNLESS you need that amount of power. Anymore and you're wasting gas. Simple as that. Auto's are inherently inefficient because of the range and loads that the engine must go through. Most of the time people only need 80hp to cruise down the highway at 70MPH, so what would be the point of running the engine (v8 for example) at 4000RPM to make 280 pounds of torque and 200 horsepower?
Prime movers on the other hand are designed to go two speeds most of the time, Stop and Go. Go means WOT at torque peak = best BSFC = best fuel efficiency.

I don't know what kind of car you're driving, but i'f im tootling down the highway in fourth gear, i most definetley have to hold the throttle wider than in fifth gear.

*edit* Anyway, as i said before, your thoughts aobut BSFC does not relate to fuel mileage. Simply put, the best BSFC you'll get is when your at peak torque RPM at WOT. This means you will get the most power per pound of fuel = work efficiency. This does NOT mean you will get better fuel mileage by running at max BSFC, UNLESS you need that amount of power. Anymore and you're wasting gas. Simple as that. Auto's are inherently inefficient because of the range and loads that the engine must go through. Most of the time people only need 80hp to cruise down the highway at 70MPH, so what would be the point of running the engine (v8 for example) at 4000RPM to make 280 pounds of torque and 200 horsepower?
Prime movers on the other hand are designed to go two speeds most of the time, Stop and Go. Go means WOT at torque peak = best BSFC = best fuel efficiency.

You should take a long hard look at that graph, it's right above your post and answers all of your concerns.

See those lines that arc through it (the 30kw one is red), they are constant power lines.
If the car with this engine needs 20kW to push it along at cruise, then reading the graph will show that is best acheived at just under 2000rpm and requires approximately 1/2 throttle.
The BSFC at this point is approximately 260g/kwH.

If the same car is geared to run at 3000rpm then to deliver 20kW requires approx 1/3 throttle.
The BSFC at this point is approximately 310g/kwH.

The fuel consumption of this engine at 3000rpm is 20% higher than 2000rpm for the same power output.

The fuel consumption of this engine at 3000rpm is 20% higher than 2000rpm for the same power output.



Which is exactly what Steel has been saying :)

I think we're your both getting confused over the issue is how engine RPM and load relate to throttle position.

Which is exactly what Steel has been saying :)

I think we're your both getting confused over the issue is how engine RPM and load relate to throttle position.

This is the part I was disagreeing with:

as i said before, your thoughts aobut BSFC does not relate to fuel mileage

could someone please explain the graph that we have all been discussing.
i may understand the whole thing better if i knew what the graph meant.
:-]

could someone please explain the graph that we have all been discussing.
i may understand the whole thing better if i knew what the graph meant.
:-]

Sure:smooch:

Horizontal axis is engine speed (rpm)
Vertical axis is manifold pressure. Max vacuum at the bottom, full open throttle at the top.

The islands are BSFC (brake specific fuel consumption), they are marked with how many grams of fuel it takes to provide 1kw of engine output for 1 hours. Smaller numbers are more efficient. Lowest BSFC is less than 250g/kwH, highest BSFC is more than 550 g/kwH.

The thick blue line across the top is torque, units are Nm (Newton Metres) and the scale is on the right hand side. Max torque is approx 240Nm from 3000-4000rpm.

The lines which arc across the graph from top left, then down and across are constant power lines. The red one is 30kW, this engine maxes out at 120kW.

so if rpm and torque are directly related, why dont engines w/ lots of torque low down get better power (excluding desiels)
is it because of the fact that you have to close the throttle more?

so if rpm and torque are directly related, why dont engines w/ lots of torque low down get better power (excluding desiels)
is it because of the fact that you have to close the throttle more?

I think it's due to engine design.
Most engines are either designed for good volumetric efficiency down low (which gives good low end torque and very good economy) or for good volumetric efficiency up high (which gives lots of power, great top end but little down low).

To bridge the gap between the two, manufacturers are using such things as variable length inlet manifolds and variable valve timing.

A very good example is toyotas FE engines compared to their GE engines.
The corolla I owned with the 5AFE was over 25 seconds to 100 km/h but was quite economical.
Simlar car with the 4AGE would be 1/3 to 1/2 of that time.

becasue power is just a mathematical toy, really.

HP = (Tq x RPM)/5252 The reason most motors with lots of torque down low (and this INLCUDES diesels, I don't understand why you would want to exclude them?) is that they usually will not spin all that fast, and are designed with this in mind. It may be in the case they they are big and heavy motors and/or have a very long stroke (such is the case with heavy diesels) or the intake is designed for velocity and not max flow i.e. the motor will choke if you try to spin it faster.

On the other end of the spectrum you have motors such as F1 engines that have terrible torque figures (something like 100 foot pounds, dont quote me) considering their displacement, but put out 700+ HP. Hoooow do they do it? They spin to 18,000+ rpm.

So the F1 car will beat the Mack truck to the finish line, but if i have 40 tons to tow, i think i'll pick the truck (not that the car sin't capable, it can do it fine, you'd just need a transmission with 100 speeds to get anywhere)

the reason i excluded diesels is that like you said, w/o a lot of work, most diesels only rev to like 4500 rpm or less.
...i dont know...

FINE diesels get to play too... if that makes you happy :-]

the reason i excluded diesels is that like you said, w/o a lot of work, most diesels only rev to like 4500 rpm or less.
...i dont know...

FINE diesels get to play too... if that makes you happy :-]

Why would you even want to compare diesels to petrols in this context?

Bananas and apples.

well that was my original reason for saying "diesels excluded"

HAHAHAHA!!! That's a pretty good way of explaining torque and horses. If it's all the same to you folks, I'll take the F1...

Anyhow, some bolt-ons do work on turbo-charged engines, but significantly more so for turbo-charged diesel engines, e.g., a $3,000 intercooler setup or a $300 water-injection setup; propane intake fumigators; NO2 kits; racing stripes...

The added horses/torque come at a price: added fuel consumption UNLESS you increase the engine's efficiency.

Because there is a finite amount of energy in a fixed amount of fuel (petrol or diesel), increasing an engine's efficiency is the only way to extract more work out of the fuel without increasing fuel consumption.

Gasoline engines have a fixed stoichiometric A:F ratio (~14:1). Diesels are not limited by such Fuel:Air ratio and can run anywhere from 10:1 to 150:1. Cold air intakes and free-breathing filters come into play in the realm of the higher A:F ratios.

Anyway, to add to the list of fuel-saving tips:

-- replace engine-driven cooling fan with thermostat-controlled electric fans
-- drive at the engine's max-torque RPM as much as possible
-- install larger diameter tires for mostly highway driving, or smaller diameter tires for mostly stop-n-go city driving (Yep! Higher pressure tires require less energy because it takes energy to continually squish tires as you drive along)
-- reduce load on alternator by turning off unneeded juice-burning accessories
-- consider re-sizing accessory pulleys depending on your needs

Good luck!