Stock Intake Pressure Drop Measurements

[Matt64341]

Last night I did some pressure drop testing on the stock intake. The air pressure from the atmosphere is about 14.7 psi, and the engine sucks in the air through the intake. If everything was perfect, the air at the throttle body would be at atmospheric pressure, but the intake causes restrictions, so in reality, the air at the throttle body is less than atmospheric. The negative pressure can be measured which is what I did.

 

I built a manometer with some wood, some $3 plastic tubing from Home Depot, an empty plastic container, water and food coloring. This is what it looks like. The second picture is with me sucking on the end to show how it reads.

 

I marked off every inch up the board and labeled every 2, and the water was filled until it was right at the -4 line (so I had to add 4 to all my measurements). They are measured in inches of water. To actually do the test, I installed the entire stock intake with stock paper filter. The intake starts at the throttle body where there is a resonator, then there is the MAF, the Airbox and filter, a bend out of the box, and a pipe in the fender with another resonator on the side.

 

I tapped into several spots in the intake and measured the pressure drop at each point. To find the maximum drop at each point, I had to max out second gear, so all measurements are full throttle at ~6k rpm. The measurement at the throttle body is the TOTAL intake restriction. Then the measurement after the resonator will be smaller if the resonator is causing a restriction. The difference between them is the pressure drop caused JUST by the resonator.

 

I took measurements:

1. At the throttle body

2. After the resonator and before the MAF

3. After the MAF and before the Filter

4. After the filter and before the bend

5. At the end of the bend before the pipe and second resonator

 

Here are the results

1. 24 inches of water

2. 24 inches of water

3. 12 inches of water

4. 9 inches of water

5. 7 inches of water

 

So,

Total Intake Restriction

24

 

Resonator Restriction

0 (0%)

 

MAF Restriction

12 (50%)

 

Filter Restriction

3 (12.5%)

 

Bend Restriction

2 (8.3%)

 

Resonator Restriction (fender)

7 (29.2%)

 

[all of the numbers add up to 24 - the total intake restriction]

 

From other results for cars I have read about, 24 inches of water is bad, but there are worse out there (in the low 30's). Just for comparison, 24 inches of water is about 0.87 psi of wasted pressure that could make it to the engine. Obviously the biggest restriction is the MAF, which is also the hardest to change, but I am going to look into what can be done about that. I am thinking that removing the tight mesh screen (but leaving the fins) might help, and I don't think it will have any negative effects if the fins are still there to straighten the airflow. But a 30% improvement can be made just by removing the resonator in the fender, and it is very easy to do. For a relatively small improvement, a K&N high flow filter would also help. Unfortunately removing the resonator at the throttle body will not have any measurable change in pressure. I also think that that you could make a small improvement by adding a larger diameter bend on the end of the airbox with a smoother transition in, so you could have about a 37.5% improvement for just a few dollars and maybe an hour or two of work.

 

I would expect that the ChiTown intake would have the restriction of the MAF and the pressure drop from the rest of the pipe is probably negligible. So an improvement of around 50% over stock. If we could get rid of even some of the restriction from the MAF we would improve the airflow over the stock intake by a considerable amount.

[ing-schu@online.no]

Respect

 

Refer to my .org reply.

[///BHRpowered]

 

there should be a reply posted where people who don't care about xbox in the dash will care.

 

matt - I assume this was with the stock intake? I would like to see the difference with the chitown intake. Noone disagrees that the TB causes restriction, and chi fabbed up a new one, but all the damn vacuum lines and everything going into it, its almost like its stealing air.

[Matt64341]

 

there should be a reply posted where people who don't care about xbox in the dash will care.

 

matt - I assume this was with the stock intake? I would like to see the difference with the chitown intake. Noone disagrees that the TB causes restriction, and chi fabbed up a new one, but all the damn vacuum lines and everything going into it, its almost like its stealing air.

 

Yes everything was stock, and it was a paper filter. The resonator that ChiTown replaced causes 0 pressure drop, so replacing it would not help pressure-wise, but he used a shiny metal pipe and it does not go as close to the hot engine as the resonator, so I would expect the air would be able to stay slightly cooler. Gains can be made through less pressure drop and less temperature gain, but this test only goes into the pressure part of it. The vacuum lines just vent there, to release vacuum, but it is such a small amount, it has no way of stealing enough air to affect the engine which is breating in massive amounts of air.

 

I do not have a ChiTown intake to test, but you can assume that the chitown intake will still contain the MAF with a 12 inches of water drop, and the rest of the pipe is free flowing, and I would guess should cause between 0 and 2 inches of water maximum, so 42-50% improvement over stock, most likely closer to 50.

 

I also plan at some point to get a digital thermometer with a good temperature range, so I can test the temperature drop from ambient, and I would like to use it to see how efficient the intercoolers really are as well...

[latinopikachu]

woooooooow

 

you're cool :thumbsup:

[ChiTown]

very interesting. good write up on an idea i never thought of! As for the Chitown intake, this seems to mirror what i have found from building the intakes. stage 1 of the intake (delete fender resonator) added the most performance gains and a nice sound. After installing stage 2 i did not feel any noticeable gains but the intake did get louder because of the second resonator delete. I assume a small gain is accomplished by the tubing being 3" from filter to TB however.

[Matt64341]

very interesting. good write up on an idea i never thought of! As for the Chitown intake, this seems to mirror what i have found from building the intakes. stage 1 of the intake (delete fender resonator) added the most performance gains and a nice sound. After installing stage 2 i did not feel any noticeable gains but the intake did get louder because of the second resonator delete. I assume a small gain is accomplished by the tubing being 3" from filter to TB however.

 

Yea that's true, and like I said before, the resonator is black plastic and is touching the side of the engine, and your stage 2 pipe is not pressed up against the side of the engine and is a shiny metal so I am guessing that the air would stay cooler passing through the pipe than it would through the stock resonator. It is a good enough reason that I might switch it out at some point too. Plus, I really like how much less clutter there is without all the stock intake pieces.

 

[latinopikachu]

if i could bend pipe i might try making my own intake

[Matt64341]

if i could bend pipe i might try making my own intake

 

You can get really nice mandrel bent pipes and put them together with rubber or silicon couplers. They have them at places like boostcontroller.com or ebay The size of the intake is 3".