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Has stiffer springs
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4,875 Posts
Discussion Starter #1
In our previous installment, concerns were expressed about the possibility
that air flow underneath the car could cause a low-pressure zone around the new air intake location.

To determine whether this is occurring, we need a sensitive pressure gauge
(otherwise known as a manometer (no, this has nothing to do with boobs -
you're thinking of something else)). Suitable digital pressure gauges can be
purchased for around $100-$200.

But this is all too expensive and takes too long. So, Ladies and Gentlemen, I present to you...



The flinkometer! It is just a u-tube, with the remote end fed into the engine
bay and inserted at the site where we wish to measure the air pressure.



I measured the air pressure at three locations:

1: Inside the Volant CAI box. This reading will tell us the resistance
getting into the Volant unit, and will also tell us whether there are any
low-pressure effects from air passing underneath the car.

2: Inside the head of the Volant filter cone (drilled a small hole, poked the
tube into it). This will tell us how much additional restriction the Volant cone
is causing.

3: Inside the intake tube, after the MAF. This will tell us how much
additional restriction the MAF is causing. (poked the tube inside the hole
for the oil vapor thingy, taped it up. Lost the little rubber junction gizmo
on the freeway somewhere :()

We're interested in the worst case here: full throttle, maximum revs. So I
tested by flooring it in 2nd gear and watching the water level when the rev
limiter came to visit. Smartypants here decided to do all this testing in
peak hour on 101, but we cannot allow the threat of mere sudden flaming death
to stand in the way of progress, now can we?

Results:

- Inside the Volant box we're seeing a pressure drop of 2" of water. That's
0.07 PSI, or 0.0053 atmoshperes. I figure this translates to a 0.5% power loss.
I was unable to detect any pressure drop due to air flow under the car:
cruising at 60MPH the water levels were equal.

- With the sensor inside the Volant cone we're seeing a 7" water column.
That's 0.26 PSI, 0.019 atmospheres. So the Volant cone is costing an
additional 1.3% peak engine power.

- Inside the intake tube, behind the MAF: 12 inches. 0.44 PSI, 0.032
atmospheres. So the MAF is costing us an additional 1.8% of peak power.

This is starting to get significant! Due to air intake restrictions the car
is running at a 0.44 PSI negative boost and is losing 3.2% peak power. And
this is before the throttle body.

If descreening the MAF reclaims that 1.8% loss then we're talking an
additional 6-7 hp at the wheels due to the descreening.

But that MAF screen is there (I think) to equalize the pressure across the
tube, to make the MAF more accurate. Possibly removal of the MAF screen would
cause measurement inaccuracies leading to losses which would offest the gain
which descreening provided. But I think I read somewhere that the engine runs
open-loop at full throttle? If so then yeah, descreening is a good idea.


Anyway, the flinkometer has now been decommissioned pending either a)
fabrication of a suitable mounting pod for it or b) experimentation with a
homebrew under-the-car ram air intake, to see if we can reclaim some of that
0.44 PSI.

Stay tuned...
 

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Die Kriegsziege fordert Blut
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1,289 Posts
I don't think adding all the pressure drops together is good math. Once you are inside the air tube between the MAF and the throttle body, the pressure in the tube is already being affected by the cone and such and is not compounded.

Rather than the math you have adding all the inches of water...

2" in the box
7" in the cone
12" in the tube

...the total should be 12" since that is the furthest and most powerful pressure loss or..

2" in the box
5" in the cone (5 cone +2 box for the reading of 7)
5" in the tube (5tube +5cone +2box =12" which is what was measured for the readng of 12)


As an example, let's take diving in the ocean. For sake of argument let's say roughly 14' of water is an atmosphere. At 140' you have 10 atmospheres.

if you take readings at 42' 84' and 140' and add them together,you end up with almost twice the true reading.

42' (3atm)
84' (6atm) and
140' (10atm)

You end up with 19 atmospheres, rather than the 10 atmospheres truly achieved at 140' of depth.

So rather than the 3.2% power loss calculated by adding all the power losses measured, I feel it is truely only 1.8% power loss since that is the greatest pressure loss measured. Still, a power loss nonetheless.
 

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Die Kriegsziege fordert Blut
Joined
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1,289 Posts
I don't think adding all the pressure drops together is good math. Once you are inside the air tube between the MAF and the throttle body, the pressure in the tube is already being affected by the cone and such and is not compounded.

Rather than the math you have adding all the inches of water...

2" in the box
7" in the cone
12" in the tube

...the total should be 12" since that is the furthest and most powerful pressure loss or..

2" in the box
5" in the cone (5 cone +2 box for the reading of 7)
5" in the tube (5tube +5cone +3box =12" which is what was measured for the readng of 12)


As an example, let's take diving in the ocean. For sake of argument let's say roughly 14' of water is an atmosphere. At 140' you have 10 atmospheres.

if you take readings at 42' 84' and 140' and add them together,you end up with almost twice the true reading.

42' (3atm)
84' (6atm) and
140' (10atm)

You end up with 19 atmospheres, rather than the 10 atmospheres truly achieved at 140' of depth.

So rather than the 3.2% power loss calculated by adding all the power losses measured, I feel it is trueluy only 1.8% power loss since that is the greatest pressure loss measured.
 

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The Entenmann's Shim-Sham
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12,143 Posts
Interesting.

I emailed Amsoil recently (no reply, going to try calling) because they now have some out with an Ea filter, as they call it. These conical filters replace the plastic/rubber/metal top of a traditional conical filter with more filter material directed towards the airflow.

I think it would be interesting to see how much a simple change to this type of filter will affect the car's ability to intake air. Again, one needs to be made for the GTO since the only one close enough to the measurements we need is a half inch taller and a half inch wider, and thus, a half inch too tall and a half inch too wide.

www.amsoil.com/StoreFront/eaau.aspx
 

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Has stiffer springs
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4,875 Posts
Discussion Starter #7
I don't think adding all the pressure drops together is good math. Once you are inside the air tube between the MAF and the throttle body, the pressure in the tube is already being affected by the cone and such and is not compounded.

Rather than the math you have adding all the inches of water...

2" in the box
7" in the cone
12" in the tube
Nope, 12" of water pressure was the measured difference between ambient and
behind-the-MAF. So from the other measurements, I figure that into-the-box was
worth 2", through-the-cone was 5" and through-the-MAF is worth another 5".
 

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Has stiffer springs
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4,875 Posts
Discussion Starter #8
experimentation with a
homebrew under-the-car ram air intake, to see if we can reclaim some of that
0.44 PSI.

Stay tuned...
Bad news.

To work out how helpful a ram air intake is likely to be, we need to know how much
positive pressure there is at the front of the car. To simulate this I got a 24"x5" plank,
drilled a little hole in it and poked the sensor tube in there. Then went for a drive.
This led to a near-death experience for a cyclist as a minivan whizzed past him
at 40MPH with my daughter holding a bloddy great plank out the window.

Result? 1" water column at 40MPH, 2" at 65MPH. That's 0.07 PSI boost at 65PMH.
0.005 atmospheres. 0.5% increase in power, and you have to drive at
65MPH to get it? Forget it, not worth it.

On the basis of this measurement I'm prepared to pronounce ram air intakes
to be a load of balls.

To simulate a scoop we got a 4" funnel ("hey, that's for replacing my diff lube") and
taped the end of the tube into the thin end of the funnel and went for another drive
(no cyclists this time). Exactly the same result: 2" water column at 65MPH. And
why expect any difference? How could there be a significant pressure gradient
across a few inches of open air??

So on the basis of that test I'll pronounnce scoops on ram air intakes to be another
load of balls.

My bottom line: I'd expect a small gain of the order of 1-2% at WOT from MAF
descreening, and after that, nothing else will be effective apart from forced
induction.

Except, of course, for keeping the intake temperature down. At room temperature every 5F
increase in air temperature will decreases the air's density by 1%..
 

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1LE
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13,384 Posts
Great work!
I'm thinking the pressure might be lower under the car, in front or on top will have the most pressure.
 

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Don't Taze me Bro
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638 Posts
pressure tests for hood scoops and cowl heat extraction

Dude, nice job, I've been waiting on someone to rig up one of these to run at various points on the car.

Why did you use plywood plank to measure stagnation pressure? Why not tape the tube right to the front grill?

Can you re-run these tests at some steady cruise speed (all at 80 mph) with the tube taped in the following locations?
1. At the front grills (maybe in a couple locations) to measure stagnation pressure (outside of car)
2. At the front lip of hood (outside of car)
3. At the actual hood scoop grills on (outside of car on hood) to see if that area is actually a low pressure zone or has some stagnation pressure.
4. underneath hood say within a few inches of hood scoops
5. At rear of hood in cowl area at bottom of windshield
6. under drivers side fender where some people put their CAI
7. Under hood near firewall (cowl exit area for those who have removed weatherstripping)

If you can, please take pictures of each set-up. This would be a big help to many of us.

By comparing the relative pressures on both sides of hood in the scoop area and both sides of hood in the cowl area we can determine what kind of airflow potential and direction of flow you'll have at both locations. I've often wondered if the stagnation pressure that is normally found near the base of the windshield on most cars could be driving air into the engine compartment (reverse flow) at high speeds for those who have pulled the weatherstripping. But then at lower speeds or at stop lights it flows out from engine comartment to release heat from convection. Seeing the differential pressures in all these areas could answer quite a few questions in posts.
 

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Administrator
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20,348 Posts
stick the tube into the intake manifold, and youll lose all kinds of power, zomg!
 

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Growing up is an option
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17,296 Posts
nice stuff. this is much better and quantitative than most posts. the hood from my study of it isn't going to be a good point. smack in the middle of the grill is the best. i also found that scooping underneath the fender helps if you have one there. either way "ramming" isn't really a significant effect. cold air is.
 

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Beer Geek
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3,713 Posts
How about a vertical air dam under the car, immediately behind the air intake. Then you ~~should~~ see max positive pressure at the air intake, AND max negative pressure under the skid plate for both more power and more downforce.

just a thought.

S
 

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Die Kriegsziege fordert Blut
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1,289 Posts
Nope, 12" of water pressure was the measured difference between ambient and
behind-the-MAF. So from the other measurements, I figure that into-the-box was
worth 2", through-the-cone was 5" and through-the-MAF is worth another 5".


Ah, then I misunderstood the readings. Apologies.
 

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Growing up is an option
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17,296 Posts
just as the panel filter is a restriction, the small cones that fit inside the "C"AI boxes are a bit on the small side and are too. interesting that that and the MAF restriction are confirmed.
 

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Master of Youngrushhour
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4,318 Posts
Flink - great job!

This what we need emperical information. This along with all of the great work svede1212 has been doing may lead one of us to figure out a real way to get cold air in.

Flink - I agree with your prior post that the IAT may be reading off of the plastic surronding material. I put the Vector IAT into my 04 and found that while it does measure fast - it still has something heating it up - which leads me to the plastic top. Not sure I want to cut it off - but may try.

I have spent the last few days - reworking the K&N FIPK that I just got to reduce the hot air entering it. This thing is bad on that side. I have been using metal flashing to fill in all of the engine compartment air inlets - big difference - but it ain't done yet. Once I get all of the pieces done I will post pictures for you guys. Plan on making the parts out of 1/8th aluminum.
 

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Growing up is an option
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17,296 Posts
one thing i was going to add was last Saturday i was under my car and decided to clean my air filter even tho it looked clean. a ton of sand came out of it. it looked like beach sand but i haven't been near the beach this year. no problems, just interesting
 
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