I recently bought a Magnehelic gauge off Ebay for intake restriction testing. The first intake we tested was my friends 87 NA. The biggest performance mod is the RB True duals. For the test, he had a stock intake setup in place with a Fram filter. The only thing changed was there was no hose going into it for emissions.



What we hooked up was silicone hose to that barbed connector. Then ran it thru the ac drain hose hole to the pass. compartment.



This is the gauge its self. It is a manometer. I learned about these in an Autospeed article found here ( http://www.autospeed.com/A_0629/page1.html

)

For the testing, we took it out on the highway. I had Santiago floor it in third gear at 3000rpm. He called every 1000-rpm to redline (7000) and I wrote the number. It was about 70°F out side while we did the testing.



For the results:



The first Pull we did was on a bit of a downgrade with a left turn close to redline.



3k- 3" of water

4K- 4" of water

5k- 7" of water

6k- 8" of water

7k- 9.5" of water



Second Pull was level until about 6krpms at which we took a hill.



3k- 3" of water

4K- 4.9" of water

5k- 7" of water

6k- 9.5" of water

7k- 10.5" of water



Third Pull Was fairly level as I remember it.



3k- 3" of water

4K- 4.2" of water

5k- 7" of water

6k- 8.5" of water

7k- 9.8" of water



Now, for the fourth pull we pulled over on the side of the road, took the filter out, buttoned it up, and did a run.



3k- 1" of water

4K- 2" of water

5k- 3" of water

6k- 4.2" of water

7k- 5.1" of water



As you can see, the filter did pose a large restriction. Icemark noted that on most cars there is a about a 1" of Water due to the filter. Now were using a Fram filter. That is all we had available. We will be doing a K&N after Xmas.



This was also posted by Icemark for comparison against other cars.

AutoSpeed have done a bunch of similar tests.



Audi S4 (2.2L turbo, 30inH2O)

Holden Commodore (3.0L turbo, 30inH2O)

Mazda MX-5 (1.6L, 15inH2O)

Subaru WRX (2.0L turbo, 51inH2O) [need to subscribe]

Nissan Maxima (2.0L turbo, 30inH2O) [need to subscribe]



James

Here is a close up picture of the gauge.



James

So all you are doing is measuring vacuum at varying locations in the intake or with parts of the intake left off to see if vacuum is more or less afterwards. The problem with this test procedure is you have too many variables changing between measurements.



You should be monitoring two points simultaneously and observing the difference. For example, if you are curious about how much restriction the air filter is, you need a port before and a port after the filter, and run lines to the gauge since it has the ability to measure the differential. Otherwise you need two gauges, but the quick research I did on that gauge reveals that it does support it, according to a web site anyways.



Many things can change affecting the vacuum from the engine while you are driving on the streets, so you gotta get the gauge monitoring the drop, not seperate vacuum readings done sequentially, under what are likely varying conditions...



otherwise this is a potentially intersting/useful experiment, especially if you go further and monitor drop across the various manifolds etc.

OMG, lol..James u made a post on here https://www.nopistons.com/forums/pub...#>/biggrin.png





Did you and santiago think of any CAI routes for ur white car? lol..





Keep on testing, btw...we tuned jon's car some yesterday..i'll explain on IM later,lol...

aside from what peng said, please use a NEW Fram filter for comparision

to the K&N

Hey guys I thought I would chime in.



We aren't testing different spots in the intake. Just testing the stock intake close to the end of the big hose. We are going to do it again with the K&N drop in and the Cold Air Intake that I make. I already know that my CAI does lower temps a lot and the butt dyno says its good. Real dyno tests are also in the works. We will be using a similar spot on the CAI to test for vac on it but still after the AFM and before the TB. We are going to do tests with a new MAzda OE filter. The powers that be at rx7club don't think that Fram is good enought https://www.nopistons.com/forums/pub...1047683664.gif





Santiago



PS- tests to come! https://www.nopistons.com/forums/pub...1047683473.gif



And I am going to be working with James' car and my own S5 TII shortly to come and the final version will be made public some time next year.

a K&N flows about the same as a new air filter, down the road

the K&N might flow a bit better.

Hey santiago...minus the paint issues, isnt james' car sweet as hell! Sorry..emotional attachment to his car there,lol...anyways, look forward to seeing what u and james come up with...

even if you're just testing the air filter you should take advantage of the differential feature of that pimpy little vacuum gauge you've got there and use two inputs from the two sides of the filter. They even sell the kit for that specific gauge for this purpose, using one source at a time under varying conditions is not the best approach.



http://www.johnsherman.com/gauges/magnehelic.htm



Air Filter Gauge Accessory Kit

Adapts any standard Magnehelic®

for use as an air filter gauge. Includes

aluminum surface mounting plate with

screws, two 5' lengths of ¼" aluminum

tubing, two static pressure tips and two

moulded plastic vent valves with integral

compression fittings on both tips and

valves.

yep his car is sweet. But I am sad to say that from my extremly limited experience the TII is slow down low. I don't like that. But otherwise she is a beauty!