Tuned intake for fuel economy

[Daox]

I was thinking today about if anyone had any thoughts or has read anything on tuning your intake for fuel economy? By intake, I'm talking about the piping and air filter in front of the throttle body. I think we all know that cold air intakes are good for power, and warm air intakes are good for fuel economy in gasoline engines. I'm not talking about that. I'm talking about designing an intake specifically for fuel economy. I'm talking about pipe diameter and pipe length, possibly a resonance chamber, or a bell-mouth on the inlet. I don't recall seeing any threads on this over the years, so I'm starting one.

[Stubby79]

You'd need it to match your valve timing to be most effective, so changing your cam to a "cool" cam should be done first, if you're going to.

[ThermionicScott]

I dunno if there's much "left on the table" in that regard. Isn't the throttle almost always a bigger restriction in our cars (and driving)?

Always worth investigating, though.

[oil pan 4]

Put the MAF as far away from the throttle body ad possible so the pulsating air flow doesn't create a false higher air flow reading, which would cause more fuel to be added.

[19bonestock88]

So, moving the MAF sensor further from the TB will make the readings more steady, possibly resulting in better mileage? Hmmm...

[oil pan 4]

Also use a exposed element IAT for roughly 10x faster response time.
Because if you are not running a thermostatic intake your temperature can vary widely, especially wiit a warm air intake.

[darcane]

Originally Posted by Daox

I was thinking today about if anyone had any thoughts or has read anything on tuning your intake for fuel economy? By intake, I'm talking about the piping and air filter in front of the throttle body. I think we all know that cold air intakes are good for power, and warm air intakes are good for fuel economy in gasoline engines. I'm not talking about that. I'm talking about designing an intake specifically for fuel economy. I'm talking about pipe diameter and pipe length, possibly a resonance chamber, or a bell-mouth on the inlet. I don't recall seeing any threads on this over the years, so I'm starting one.

"Tuning" an intake is really manipulating the frequency of the pulses hitting the intake valves so that the peak pressure happens when the intake valve is opened. Changing the pipe diameter and length affects this... as long as there isn't something else in the way, like a throttle plate.

At part throttle operation, which is where fuel economy is typically greatest, I believe the closed/nearly closed throttle plate is going to eliminate any ability of tuning the piping in front of it. Just do your best to eliminate restrictions like your idea of adding a bell mouth.

I could see gains by reducing the size of the throttle body or tweaking the actual intake manifold though.

[rmay635703]

The length you need off the intake to tune is quite long.

You could tune the exhaust, it has a definite affect on all cars and is generally long enough to actually tune

[hayden55]

Well the whole reason you tune exhaust is because you are attaching exhaust ports together that are firing with uneven pulses, so when you hook them together you balance out each stroke and the next stroke effectively pulls on the other. Adjusting pipe diameter after the header is just what diameter pipe is needed to flow the horsepower you are making. Too small you lose power, too big you don't much of anything. And back pressure needed is a myth for the most part, i've never seen a v8 (in my purpose) lose power from to big of an exhaust they usually just end up spending money to gain a lot of weight and a minute extra lil bit of power. So unless you are tuning an intake manifold runner length or diameter or adjusting throttle body the size of the tube wont make a big enough difference. So i'd assume the air intake tube itself would only be the same cfm to flow horsepower as the exhaust was, more than you need, you don't gain much of anything, less than you need you lose. (But that was all to make power and making power isn't always the most efficient way to tune an engine for fuel efficiency.) Then it just comes down to whether you get a nice strong smooth readings on the maf, and iat's for the purpose intended (power or thermal efficiency). But... It could be down to volumetric efficiency at bsfc. So maybe if you tuned the intake to only pull the air in it need at peak bsfc you would gain efficiency at that point, but lose power up top? I threw all my thoughts in here so somebody correct me if i'm wrong.

[Frank Lee]

I presume GM's Tuned Port Induction with it's longer runners and port injection showed good efficiency gains over it's predecessors. Probably the biggest improvement came from having dry runners vs wet such that there weren't any more rich or lean cylinders. Then the O2 sensor could really do it's job and optimize mixture strength for all cylinders. But everything has had these features for quite some time now.

I'd imagine the big fat plenum ahead of the runners mitigates pulsing at the MAF to some- small or large?- degree.

Beyond that I think the same notions we apply to exhausts also apply to intakes: runners small and long enough to promote flow momentum at the desired rpm.

Yah, I know that all helped a lot.