NA6 Intake/Exhaust Mods

[NitroDann]

I wouldnt say exposed. Id say in a mania style enclosure with a big bellmouth taking up the drivers side 3rd of the mouth. All heat wrapped. That would be where its at. Like on any n/a drag civic.

Dann

[Guran]

Dann I'm shocked and surprised! Shocked that you think pressure can be measured with a piece of wool! Surprised that you haven't done any pressure testing yourself. You don't need to buy a manometer. All you need is a length of plastic tubing, some water, and a bit on ingenuity (which you clearly have in plentiful supply!). Check out the link to Matty's intake article that was posted earlier in this thread. You'll get a pressure difference reading in "mm water" which is easily coverted to kPa if you want an SI unit.

[NitroDann]

I know I can knock up a pressure differential guage with some clear hose and some water.

But heaps have dome it before and the info is readily available.

As for the wool it doesnt measure pressure, it measures airflow, caused by pressure differential.

I test the pressure differential in my intake using my datalogging, by first checking the days air pressure with my MAP sensor in kpa, then driving, switching the engine off and seeing the new air pressure in my manifold in kpa.
Id like to know what the air pressure in my radiator duct is so i might grab a piece of wood and some hose from bunnings and find out if I need to change my intake, but then in have the engine as well as the brakes stealing air from the radiator!

Cheers,
Dann

[gslender]

I wouldnt say exposed. Id say in a mania style enclosure with a big bellmouth taking up the drivers side 3rd of the mouth. All heat wrapped. That would be where its at. Like on any n/a drag civic.

Dann

I can say with certaintiy that the JR cowl and ducting doesn't gain any heat soak. After driving for 2 hours the plastic is cool to the touch. Nothing is warm at all. I think heat wrap would be a waste of money, but then again, I'm not racing for 2 hours, so perhaps that would change things (but a lot?).

g

[Matty]

My intake produces over 1 psi of 'boost' by 100kph,

Physics says no.
[/bernoulli]

[NitroDann]

Bernoulli's Principal only applies to flowing liquids. Not static. Re-read how my intake pressure is tested.

Dann

[Matty]

Dann, I'm referring to the air flowing onto the car at 100 kmh. At that speed, you'll make about 0.06 psi, even if you stall it to a dead stop (ie, have your intake positioned at the very front of the nose).

The total restriction in the stock intake as I measured was 42cm H2O, which is only about 0.6 psi, even if you eliminated all of it. A slightly better breathing engine may measure a little more restriction through the intake, but not much more.

So at best (totally free flowing intake and a pressure head from forward movement) you might get 0.7 psi.

[Apu]

Jesus...this discussion is getting too Prof Julius Sumner Miller for me! "Why is it so...?"

But most of you guys probably don't know who he is...

[gslender]

....who Mr Glass and half of milk???

G

[NitroDann]

Matty, i understand your an engineer. So one assumes you have and can easily calculate all of this.

Do you mind getting out your notes on this and showing all the full figures and equations so we can learn.

I cannot calculate these figures, I just know what my map sensor tells me, and thats 5kpa above ambient pressure at 50 odd kph and 12-15 above somewhere a little over 100.
These tests were done engine off measuring the pressure in the intake manifold with zero flow, so yes fully stalled.

Hellmun also has a sealed heatshielded airbox that generates so much pressure it constantly blows itself apart.

Dann

[Matty]

Sure. First trick is that we are dealing with several different set of units (psi, kPa, cmH2O), but luckily they are all telling us the same thing.
http://www.sensorsone.co.uk/pressure-un ... rsion.html

1 psi = 6.89 kPa
1 psi = 70.3 cm H2O (ie, a 1 psi vacuum will suck a column of water ~70cm up your manometer)

As has been linked numerous times, my intake measurement restriction recorded 42 cmH2O maximum from the stock intake system (when being sucked at by a standard engine with a modded exhaust system). ie, the peak flow rate of the standard engine causes a ~0.6psi/4.1kPa pressure drop in the air at the throttle body. It's this loss of pressure that you are trying to gain back by opening up the intake, but the best you will get is to eliminate it completely.

Back to Bernoulli:
http://en.wikipedia.org/wiki/Bernoulli's_principle

The simplified form is what we want because changes in altitude are insignificant. The air is our fluid.

The basic equation is:
r*v^2/2 + p = constant
v = velocity (metres per second)
p = static pressure (ie manometer/gauge pressure head - use Pa)
r = fluid density = 1.2kg/m^3 for air

ie, the faster a fluid flows, the less static pressure it has.

If you follow a streamline approaching the car at 100 kmh (27.8 m/s), until it hits the nose and stagnates (0 m/s - frame of reference is the car) then you have an even simpler equation:
r*v^2/2 = (delta-p)
delta-p is your static pressure difference.

with the figures above:
1.2*27.8^2/2 = 463 Pa pressure (converts to 0.067 psi) across the nose of the car.

(Note the same equation also explains why you get low pressure zones around the outside of the car - these are the places where the air flow has been accelerated to squeeze over the body.)

How you managed to achieve 12-15 kPa (~2 psi) increase in pressure is beyond me. By calculation you'd have to completely stall an incoming airflow at about 141 m/s (509 kmh).

[Apu]

Our whole universe was in a hot dense state,
Then nearly fourteen billion years ago expansion started. Wait...
The Earth began to cool,
The autotrophs began to drool,
Neanderthals developed tools,
We built a wall (we built the pyramids),
Math, science, history, unraveling the mysteries,
That all started with the big bang!

[gslender]

ie, the peak flow rate of the standard engine causes a ~0.6psi/4.1kPa pressure drop in the air at the throttle body. It's this loss of pressure that you are trying to gain back by opening up the intake, but the best you will get is to eliminate it completely.

Matty, are you therefore stating that an incoming airflow (from driving the vehicle forward) is unable to compress/force air into the engine beyond what it can suck in itself - eg. thinking that you can produce the outcomes of a Supercharger/Turbo are just not possible - even when standing in a 100km/h wind?

I don't disagree, but just don't fully appreciate why this is so?

[jerrah]

This would go against the whole "ram air" of motorcycles? He may just be saying that the benefit does not equal 1 psi positive pressure.

http://en.wikipedia.org/wiki/Ram-air_intake
http://www.sportrider.com/tech/146_9912_ram/index.html

Well what would you rather have-115 horsepower or 122 horsepower? The CBR-XX obviously reacts well to ram-air induction. The horsepower and torque curves literally mimic the non-ram-air graphs, only with a five to seven horsepower increase and three to five additional foot-pounds of torque. It should be noted the Honda XX's ram-air system is one of the most efficient on the market

For a speed of 150 mph, the resulting maximum theoretical pressure would be about approximately .4 psi

http://www.sportrider.com/tech/146_9910_ram/index.html

[NitroDann]

Ive never claimed 2psi. Im claiming that a fully stalled manifold pressure is about 1psi at 100. Im logging with the engine off.

There is no intake restriction and bernoullis principal doesnt take effect as there is zero airflow.

Dann