Looking at the air intake of my 199 1

[fortee9er]

Looking at the air intake of my 1996 Ford E350 (7.5L) van it looks less than ideal. The smallish air box sits atop of the radiator, the air intake scoop also looks too small. I was thinking of a more conventional air box placed in the space normally occupied by the second battery in diesel applications. Behind the passenger side headlight. Is this a worthwhile modification in terms of efficiency (cooler denser air) or am I just wasting time and money?
Thank You

 

[MikeHalloran]

It will make more noise, which may feed your Foyt-ish fantasies, but you will need to make very careful measurements to detect an improvement, if there is one.


Mike Halloran
Pembroke Pines, FL, USA

 

[gruntguru]

It is very easy to simply measure manifold pressure at full noise (peak power). If the car has a MAP sensor simply compare the reading at key-on-engine-off. If not grab a cheap Delco 3 wire MAP sensor - connect GND, +5v (3 AA's for 4.5v will do) and read the middle terminal wrt gnd. If you want to go really cheap, make a U-Tube water manometer to carry in the car. Will need to provide a ball valve in the line to the manifold - close the throttle while taking readings and your manometer becomes a very sudden water injection system.

each 1" HG (13.6" water) is perhaps 5% power loss. (Anyone have a more accurate rule of thumb for this?)

je suis charlie

 

[fortee9er]

Gruntguru,
My van does use a MAP sensor that is easily accessed. You stared "If the car has a MAP sensor simply compare the reading at key-on-engine-off." But you didn't say what to compare to.
Could you please clarify.
Thank You

 

[BrianPetersen]

Connect a Scangauge or some similar instrument to your OBDII port.

Arrange for it to display "MAP" (manifold air pressure).

Turn the key on but don't start the engine. What the MAP displays at that moment, is what it thinks the barometric pressure is.

Now start the engine and drive around. With some straight and open road ahead, floor the accelerator. Note what the MAP displays under those conditions. Ideally this should be at the same altitude and on the same day as your engine-off check.

The highest MAP can possibly be without forced induction, is barometric pressure.

So if barometric MAP shows (let's say) 98 - 99 kPa (as it does in my car where I live), and at full throttle it shows 97 - 98 kPa (as it does in my car!) it means the entire pressure drop in the intake system up to wherever the MAP sensor is, is (in my case) somewhere near 1 kPa.

That is not very much, and given that there is always going to be *some* pressure drop, it pretty much means that there is nothing further to be gained by doing anything to the air intake system - which, in my case, is the stock snorkel from the outside of the engine compartment to the stock air filter housing. I made my own connector hose from the air filter housing to the throttle body to eliminate a resonator that was a royal pain to deal with. Then the stock throttle body and intake manifold.

If, on the other hand, at full throttle it is only showing (say) 90 kPa, and barometric was 99 kPa, then you've got some work to do and there's likely power to be found by doing it.

Bear in mind also that the biggest gain will likely be by making sure the temperature of the intake air is as close to the outside temperature as possible, as opposed to the temperature of the engine compartment. This is where aftermarket "warm air intakes" end up LOSING power.

The auto manufacturers are not stupid; chances are, your intake system already draws air from outside the engine compartment. Mine does.

 

[EdStainless]

Or you look and see what K&N sells for this engine.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[fortee9er]

Brian thank you for your post, and explaining what I needed to know. My concern with the intake is that while the air box draws air from the outside it sits a top of the radiator. Look at the link on my first post for pictures of the intake system.
Ed, K&N does make a filter for my van. It is a double cone affair and I would have to build a cold air box for it. If I do build a cold air box I rather use a flat panel type of filter.
Thanks to all

 

[BrianPetersen]

Your first photo doesn't give me a clue of the orientation of where we are looking ... maybe you know which way the photo was taken, but I can't tell.

Remember that when you are driving forwards, air flow is from the front of the radiator to the back. It doesn't (or shouldn't, unless the flow pattern was remarkably disturbed) go through the radiator front to back, miraculously work its way up to the front and on top, and then get to the air intake. Just because the air intake is on top of the radiator doesn't mean the air is going through the radiator first on the way there.

 

[Tmoose]

There may be a thermostatically controlled mixing valve in the intake ducting upstream of the filter.
So Even if cold air enters, it is tempered with heated air from around the exhaust so the air entering the engine is fairly uniform.

 

[gruntguru]

To add to Brian's excellent post. "With some straight and open road ahead, floor the accelerator. Note what the MAP displays under those conditions." I would add "Note the lowest MAP reading under these conditions" (This will occur at the upper rev range)

je suis charlie