Does a cold air intake improve gas mileage?

[SteveSRT8]

my 05 Silverado picked up about 1.5 mpg from my AFE intake. Note it is a dry filter, and is still reusable. 5.3 gas V8.

As an example of the other side of the coin, my Mopar 6.1 gets very little gain from a CAI, the factory box is very well designed.

 

[2003f7]

Originally Posted By: SteveSRT8
my 05 Silverado picked up about 1.5 mpg from my AFE intake. Note it is a dry filter, and is still reusable. 5.3 gas V8.

As an example of the other side of the coin, my Mopar 6.1 gets very little gain from a CAI, the factory box is very well designed.

My old 04 1/2 ton with a K&n FIPK was about the same. It did improve the mileage but the noise was unbearable when I was towing. I removed it and sold it to s friend that does not tow. He loves it and also notices a MPG improvement.

 

[mechtech2]

Ram air is different than cold air.
A true ram air can help power at high speeds - full throttle at 50 MPH minimum. this requires forward facing scoops that funnel the air [with no leaks] into the intake.

Neither should help with economy when cruising.

 

[OVERKILL]

Originally Posted By: mechtech2
Ram air is different than cold air.
A true ram air can help power at high speeds - full throttle at 50 MPH minimum. this requires forward facing scoops that funnel the air [with no leaks] into the intake.

Neither should help with economy when cruising.



Agreed.

 

[rpn453]

Originally Posted By: OVERK1LL
Interestingly enough, replacing the stock intake tubing on my Mustang did nothing to reduce low-end power, but did increase top-end power.


How did you determine that?

Originally Posted By: OVERK1LL
Air modulation is performed by the throttle body. This is the last component before the intake. You are trying to tell me that the size of the tubing BEFORE this variable restriction is in some way going to affect how this device functions? The biggest restriction at the "drive around town" power level and throttle position IS the throttle body.


Exhaust and intake tuning involves more than losses; it also involves fluid inertia. At what point does the exhaust no longer affect the tuning? After the cat? The resonator? The muffler?

Originally Posted By: OVERK1LL
If the factory air system is not adequately able to feed the engine above 3,500RPM under full load, then logic would dictate that replacing it with a freer flowing system would increase power in that area......


Logic would also dictate that they'd want to advertise the performance of an intake at the lower end of the rpm range, if it doesn't adversely affect performance.

Originally Posted By: OVERK1LL
Perhaps using the term AFTERMARKET CAI would be more accurate.


Perhaps. Therefore, from this post on, everyone in the thread must use the term AFTERMARKET CAI!

 

[mechanicx]

Originally Posted By: rpn453
Originally Posted By: OVERK1LL
Interestingly enough, replacing the stock intake tubing on my Mustang did nothing to reduce low-end power, but did increase top-end power.


How did you determine that?

Originally Posted By: OVERK1LL
Air modulation is performed by the throttle body. This is the last component before the intake. You are trying to tell me that the size of the tubing BEFORE this variable restriction is in some way going to affect how this device functions? The biggest restriction at the "drive around town" power level and throttle position IS the throttle body.


Exhaust and intake tuning involves more than losses; it also involves fluid inertia. At what point does the exhaust no longer affect the tuning? After the cat? The resonator? The muffler?

Originally Posted By: OVERK1LL
If the factory air system is not adequately able to feed the engine above 3,500RPM under full load, then logic would dictate that replacing it with a freer flowing system would increase power in that area......


Logic would also dictate that they'd want to advertise the performance of an intake at the lower end of the rpm range, if it doesn't adversely affect performance.

Originally Posted By: OVERK1LL
Perhaps using the term AFTERMARKET CAI would be more accurate.


Perhaps. Therefore, from this post on, everyone in the thread must use the term AFTERMARKET CAI!


Exactly, it's the same concept that smaller plenums and intake runners can make more torque at WOT from say 1500RPM to some higher RPM to where the smaller runners become restrictive. This ram effect is inertia, not to confused with a "ram air" intake. This concept has been shown many times on dyno tests. Some people here just argue against things that have been proven many times over and they don't even know what their even arguing about really.

 

[mechanicx]

Originally Posted By: slammds15


whom ever said the small tube tunnel ram thing needs a lesson on physics and not advertisements. The engine creates a low pressure area and the high pressure area (atmospheric pressure) moves into the engine. How is a straw equal to a fire hose for restriction at any flow rate?

I have heard of ppl claiming to have gained moderate MPG's and so they think/feel power. These ppl are Not hindered idiots just your normal everyday Joe. I have no statistical data just hear say. I also might add, they did install actual boxed in cold air intake system.


Apparently you are the one that needs to study engine tuning dynamics. If what you said was true the shortest, biggest intake runners would make as much or more low RPM torque as as any that are longer and smaller.

 

[rpn453]

Originally Posted By: slammds15
whom ever said the small tube tunnel ram thing needs a lesson on physics and not advertisements. The engine creates a low pressure area and the high pressure area (atmospheric pressure) moves into the engine. How is a straw equal to a fire hose for restriction at any flow rate?


Well, let's have that lesson then!

The way I understand it, intake and exhaust tuning involve a balance of fluid inertia and flow restriction. Assuming minor losses are the same in two exhaust or intake systems of different size, the larger will have lower friction losses. However, the fluid will also travel at a lower velocity and therefore have less inertia. So as the valves are opening and closing - providing pressure pulses in a compressible fluid - that lower inertia will not be able to contribute as much toward smoothing out those pressure pulses. If you have a mass of compressible fluid moving along a pipe and you quickly close a valve behind it there will be a low pressure zone in front of the valve as the fluid expands, slowing the mass in front of it. If the valve is closed ahead of it, a high pressure zone will result from the compression of the fluid by the mass behind it. So, at any given combination of load and engine speed, for a given length of pipe, there will be an ideal pipe diameter that balances those two effects. As flow increases, the ideal pipe diameter increases. Of course, if you have a turbo in the system the impeller probably provides more than enough inertia and, in that case, anything beyond what is necessary for smooth flow in or out of the impeller should be as open as possible.

I've never actually seen a proper and complete explanation on exhaust tuning, and this is simply a compilation and analysis of the information I have gathered in my head over the years. I look forward to your critique!

 

[rpn453]

Originally Posted By: OVERK1LL
Noise reduction is likely the primary role.


But after all that rambling, I do actually agree that the efficiency and output of OEM intake and exhaust systems is often hindered by noise reduction methods to the point that an AFTERMARKET CAI can improve power across the entire operating range of the engine. However, I believe they are unlikely to improve fuel economy, as they are usually excessively large for the minimal power levels that are typically used during daily driving.

 

[calvin1]

Any change that lets you get more air into the engine will cause your ECU to also add the matching amount of fuel. If you want to change your intake so you get better mileage you need to make it MORE restrictive, not less.

 

[[RT] ProjUltraZ]

it really depends how restrictive the stock intake is, but most are more restrictive than the K&N. that said you should buy an Amsoil EAO filter and swap it as soon as you get it. don't bother w/ the red oil

 

[OVERKILL]

Originally Posted By: rpn453
Originally Posted By: OVERK1LL
Interestingly enough, replacing the stock intake tubing on my Mustang did nothing to reduce low-end power, but did increase top-end power.


How did you determine that?

Originally Posted By: OVERK1LL
Air modulation is performed by the throttle body. This is the last component before the intake. You are trying to tell me that the size of the tubing BEFORE this variable restriction is in some way going to affect how this device functions? The biggest restriction at the "drive around town" power level and throttle position IS the throttle body.


Exhaust and intake tuning involves more than losses; it also involves fluid inertia. At what point does the exhaust no longer affect the tuning? After the cat? The resonator? The muffler?

Originally Posted By: OVERK1LL
If the factory air system is not adequately able to feed the engine above 3,500RPM under full load, then logic would dictate that replacing it with a freer flowing system would increase power in that area......


Logic would also dictate that they'd want to advertise the performance of an intake at the lower end of the rpm range, if it doesn't adversely affect performance.

Originally Posted By: OVERK1LL
Perhaps using the term AFTERMARKET CAI would be more accurate.


Perhaps. Therefore, from this post on, everyone in the thread must use the term AFTERMARKET CAI!

You are missing my point.

Intake design, runner shape, volume, length, taper...etc, exhaust design, header design, collector design, pipe design, all of that come AFTER the throttle body.

The throttle body is a NECESSARY restriction. When it is NOT a restriction, you are not in that lower RPM range, because of course, you are now at WOT

Same with Aftermarket CAI's. Your engine only benefits when it actually can CONSUME more air, logic would dictate that this happens in the higher RPM range.

My Mustang verification was done at the drag strip. It picked up .5Mph repeatably.



----------------


What component comes after the throttle body?

What component sits below a carburetor?

The PLENUM.

Where do the runners draw from to feed the cylinders?

The PLENUM.

The throttle body regulates the available air volume in the plenum. The air that is drawn down the runners (I agree that ALL of these components are CRITICAL in determining power output, band, range...etc) comes from the PLENUM.

During cruise, the plenum is in a constant state of vacuum, with the only thing feeding it being the throttle body. The flow of the air through the throttle body is NOT "fluid". It is broken by the blade. The ONLY time it approaches anything NEAR fluid is when you are at WOT. And of course this does not apply to the area we are discussing; low RPM put around town power, where the plenum is usually under significant vacuum.

Also, off-side: Dyno runs usually start ~3,000RPM.

 

[OVERKILL]

Originally Posted By: mechanicx

Exactly, it's the same concept that smaller plenums and intake runners can make more torque at WOT from say 1500RPM to some higher RPM to where the smaller runners become restrictive. This ram effect is inertia, not to confused with a "ram air" intake. This concept has been shown many times on dyno tests. Some people here just argue against things that have been proven many times over and they don't even know what their even arguing about really.


I agree with the small intake runners and plenums. Intake design is paramount to how an engine behaves. Things like variable length runners are KEY in allowing engines that want to rev, to have good manners in the lower RPM range. Same goes with exhaust tuning and cylinder head design. This is all a SYSTEM, which I'm sure you will agree!

The problem is that the gateway to this entire system is the throttle body. It controls the available mass of air in the plenum that allows this system to operate. A very wise man, who knows massively more than I probably ever will on this topic stated that the carburetor does not feed the engine. It feeds the plenum. The cylinders do not draw through the carburetor, they draw from the plenum. This was from a discussion about race engines and how important plenum design, shape, volume...etc are in dictating how a given engine performed. It also delved into cam timing in relation to plenum sizing and the like, but that's a little bit of a digression from the topic at hand.

I guess the point I'm trying to make is this:

Engine designers spend a LOT of time designing the engine. They spend a lot of time engineering the intake system for that engine to allow it to work well throughout its intended RPM range. They then have to "muffle" the intake tract enough to get it to pass the noise testing. I don't know if the "performance" of this component is ever factored into the equation, as the engine's performance seems to often be designed without this component (in production trim anyways) in place. A good example of course would be the Mustang Cobra, which, while advertised as making 320HP, was NOT. This was primarily due to an overly restrictive intake and exhaust setup; components that were NOT on the engine when it was designed and tested.

I think the fact that the same engine, with the same specs, but fitted into two different vehicles will have completely different intake tracts depending on the vehicle it is fitted to is another key here.

I honestly believe that the intake tract is designed in a manner in which it can reduce the most noise, while providing the engine with a decent amount of air. I imagine that on an Expedition with the 4.6L for example, which has the EXACT same intake tract as my 5.4L, that it may not benefit in the same manner from removing the small diameter noise reduction piping, since it is of less displacement, yet is given the same RPM range from the factory.

And of course, if the factory air induction system only becomes a restriction when the engine is under full load and in the upper RPM range, then it would make sense that an aftermarket CAI that removes that restriction, is only going to provide a benefit in that area as well.

 

[OVERKILL]

By the way, I tend to ramble... so if this getting too long winded for you guys, let me know.

 

[mareakin]

Originally Posted By: OVERK1LL
By the way, I tend to ramble... so if this getting too long winded for you guys, let me know.


no, please, your post was very informative!!!

I think I'm going to MOD the intake system of my COROLLA

 

[mareakin]

I noticed that the throttle response improved after I removed my carbon filter of my Corolla's intake.

Perhaps further modifications would help.

 

[rpn453]

Originally Posted By: OVERK1LL
The throttle body is a NECESSARY restriction. When it is NOT a restriction, you are not in that lower RPM range, because of course, you are now at WOT

Hey, I floor it while operating between 1500 and 3000 rpm quite regularly!

Originally Posted By: OVERK1LL
My Mustang verification was done at the drag strip. It picked up .5Mph repeatably.


But that doesn't provide any information about low-end torque!

Originally Posted By: OVERK1LL
During cruise, the plenum is in a constant state of vacuum, with the only thing feeding it being the throttle body. The flow of the air through the throttle body is NOT "fluid". It is broken by the blade. The ONLY time it approaches anything NEAR fluid is when you are at WOT. . .


It's definitely still fluid across the throttle body!

From Dictionary.com:

flu⋅id/ˈfluɪd/[floo-id]
–noun
1. a substance, as a liquid or gas, that is capable of flowing and that changes its shape at a steady rate when acted upon by a force tending to change its shape.
–adjective
2. pertaining to a substance that easily changes its shape; capable of flowing.
3. consisting of or pertaining to fluids.
4. changing readily; shifting; not fixed, stable, or rigid: fluid movements.
5. convertible into cash: fluid assets.

Originally Posted By: OVERK1LL
. . . And of course this does not apply to the area we are discussing; low RPM put around town power, where the plenum is usually under significant vacuum.


I thought we were still debating WOT situations, too! I only got into this because you said:

Originally Posted By: OVERK1LL
How is something in FRONT of the MAF and TB going to take away low-end power?


Though I certainly am responsible for bringing fuel economy into the same discussion.

Originally Posted By: OVERK1LL
Also, off-side: Dyno runs usually start ~3,000RPM.


Sure, but it depends what you're going for. For a daily driver, it's useful to know the effects of modifications at the lower revs. K&N provided the dyno plot for the Mazda3 (my car, slightly different engine) from 2300 rpm to 6900 rpm. It's odd that the peak gain is made at 4800 rpm and the two plots converge both before and after that point. There is no significant gain from the aftermarket intake at 6900 rpm and very little at 2300 rpm. I'm not applying that to this conversation or drawing any conclusions from it. I just thought it was unusual.

http://www.knfilters.com/dynocharts/69-6010_dyno.pdf

Originally Posted By: OVERK1LL
You are missing my point.


It's possible, but I was having fun with it anyway!

Your point seemed to be that tuning the intake ahead of the throttle has no effect on performance, except for the effects of friction losses at WOT. To me, it's still a mass of air flowing toward the valves, and I think the inertia of that mass would affect the flow primarily at WOT, but also even with a partially closed throttle; it's still pulsing, to some degree, as it crosses. I accept that you may be correct in that the plenum volume could negate that effect for daily driving situations or, even more likely, that the effects become so small as to be negligible. We'll have to agree to disagree unless someone can provide some credible testing or references about this specific subject, but I'm willing to concede that fuel economy in a throttled engine is probably not affected in any significant way by the installation of an aftermarket intake, as eljefino stated a few pages ago. I still believe that an oversized intake can adversely affect full-throttle performance at low revs.

 

[OVERKILL]

Hey, it made 260lb-ft to the tires at 3,100RPM, to me, the low-end was more than adequate

I didn't dyno it before and after though. Just track runs. But considering every dyno shop I've been to starts their runs at 3K, I doubt I would have learned much of anything useful for the cost of $100

I guess fluid was perhaps not the term I was looking for. The blade on the TB disrupts flow. That's its job, to restrict air volume to the plenum to control RPM. In doing so, it causes a significant break in the air flow/column/stream with the blade.

I guess if we had a lot of free time we could dyno test from idle to 3,000RPM, but I doubt that's going to happen, LOL!

5HP on a dyno is typically within the range for "noise", I would have liked K&N to average 5 runs with and without the intake.

 

[mechanicx]

The throttlebody size can affect lower RPM torque at WOT. I still say the intake tube size can have some affect on low end torque due to inertia. The thing is the intake tube size matches the TB size. If you enlarge both too much, you may see a loss of low end torque. Also for example I've seen dyno tests where the stock snorkel air cleaner housing made more low end torque torque and power than an open element aircleaner with the same filter.

 

[mechtech2]

Small intake runners favor lower RPM power.
Lrge intke runners are best for high RPM full throttle use.
Throttle response is also better with a smaller or less restrictive intake tube to the TB. Full throttle is often improved with a larger diameter intake tube.
Don't look for miracles in this area.

No engine likes exhaust back pressure -ever.
Large exhaust pipes actually have MORE back pressure at lower RPMs because of the greater mass of gas in them. This is why skinnier pipe are better for low end, until they have more restriction at greater RPMs.