Ok, so I am doubtful of gains from a K&N, and thus it has been one of my last upgrades. Flame away ...

Now to my observations.

I figured I may as well see if I can quantify any differences with a K&N and my TPI setup. At least make me feel better about buying one. A chasis dyno would be the best test, but for the price of a dyno run I'll save that for bigger changes.

The test: Can I see any difference between a Fram fiter (used) and a K&N using my scanner?

The Engine: 1988 5.7 with 1986 TPI using a 1987 5.7L prom. MAF still has screens (as I believe they straighten air flow - better reading).

Conditions: Engine warm (94-96 degrees C), closed loop, idling in diag mode (1000).

Values being watched: Air flow, Idle air motor, pulse width. ( I watched the others but for the test I did not expect anything to be effected.

What did I expect: Well I figured the free flowing filter would result in the idle air motor going in a few more steps as the air is flowing easier, so less vacuum signal is needed. Air flow should be the same. Pulse width should be the same. (so should the others)

Results: The IAC indeed was down a step or two, but what surprized me was a bit of an irratic air flow reading. At first I thought it was flowing less, but the reading jumped up to 1.0 point and back, from 7.9 to 8.9 and then back to 7.9 or 8.0. The air flow had a rather large range. My thoughts are that I have now introduced some turbulence to my air intake system. The fram filter restricted more and allowed the air to flow straighter or the filter itself, being deeper, straightened the air flow.

Conclusions: Well I think there is more airflow, but I have some turbulence to contend with. At low RPM this might result in some rich/lean or irratic idles. At WOT I don't think it will matter too much. The air flow should be great enough that the turbulance is eliminated (at that point).

Future: Well I think I will see what my MPG does over the next while. I may also look at installing a RAM tube idea on the inside of my ducting to see if I can straighten the air flow. I know ... I need to get a life.

Anyone care to comment, feel free to.

Mark.

 

I think the real benefit from the K&N is not really more hp but that your engine will be getting cleaner air and it won't restrict airflow when it gets dirty like the paper ones do.

 

I had a co-op interview at FRAM. They were testing K & N's filter. They agreed that it did flow more, but that the air that got through was much dirtier. They probably don't get as dirty because the dirt goes right through into the engine. It has to go somewhere

 

I agree, there is a trade-off with K&N filters, if you get more airflow you also get less filtering, so more dirt gets into the engine.

Other opinions: the screens on the MAF would produce turbulence if put into a laminar airstream so I'd remove them. Maybe leave a few wires to stop foreign objects from flying right into engine if something gets past air filter.

I've seen ads for an "airfoil" that gets mounted between the intake butterfly vallves to let the air get streamlined into the valves and not slam into the central depression.

Mark, you say "I may also look at installing a RAM tube idea on the inside of my ducting to see if I can straighten the air flow. " I haven't heard of this. What is a RAM tube?

 

Also one of the car mag's did a test of all the different filters a few months back, power on all of them remained within a couple of hp. Just make sure you change the filter regularly.

 

Ram tube ... just my thoughts on a way to lessen the air flow. In my particular intake setup, the MAF is the smallest diameter pipe. So perhaps I need to install some pipe or sheet metal inside my ducting in order to "direct" the air to where it should be.

Think of a 90 degree bend. At low velocity, the air has enough room to make the turn. At high velocity, the outside air will travel around the bend. The inside air will slam into the wall on the other side of the 90. Sort of like head porting. You want to help the air along, no so much change it's direction.

So Ram Tube is just a tube inside my ducting to ram the air into the MAF. Nothing too scientific ... but certainly sounds like good marketing material.

I recall SLP use to offer a cold air box for the F-body's. Inside the ducting were some deflectors to help things out.

Mark.

 

That's what I guessed, sounds like an easy way to do it. My idea was to fill in the ribbed sections of the stock tubing with a putty-like material to smooth the inside surface. I figured I could do it for about $4 and 1 hour. Your method is simpler though. As long as you don't reduce the inside diameter of the intake too much.

 

If anything can get past the filter and damage a MAF by impacting it, you have a huge gaping hole in your filter.

 

It's been known to happen. Since I made my open air filter, I only buy filters with an internal screen so if something hits the filter or it gets a little wet, pieces won't get sucked into the intake. Many filters don't have a screen inside.

 

My opinion is I'll stick with my K&N. 1. It flows better (especially compared to the stock Air Intake's), 2. It's reusable so I don't have to keep buying them, 3. As far as catching particles, water, and etc. that's the purpose of K&N using screens and why we oil them.

 

One of the advantagaes to a K&N is that is is an oiled-cotton filter element, as opposed to a dry paper element. The oil helps attract the smaller dust particles that might get through. It also increases the dirt holding capacity of the filter.

 

I happened to find a possible reason for the erratic turbulence you saw in your test. The explanation can be found here:
http://www.gmtips.com/3rd-degree/dox...maf-screen.htm

Apparently small scale turbulence is necessary for uniformity, large scale fluctuations are too much. Also, if the airflow was truely laminar, the velocity would be greatest in the center of the intake tubing and trail to zero right at the walls. This can apparently give an error 33 code because the MAF was not calibrated for this type of airflow. What do you think?

 

Well I am not 100% convinced of what the screens are for. Looking at how fragile the MAF wire is, you could think the screens are there to protect it. As well, if you have evey looked at a F*RD MAF (remembering my 91 explorer), it has a different setup an no screens. You would figure if the screens had an advantage they would use something similar.

You know, I recall the GM 2.8L MAF units. They did not have a screen, rather just a circuit board in the middle with a sensor in the middle.

What you would need to do is to use a flow bench idea and use a probe to measure the air flow in a MAF and map out the high and low velocity areas.

For myself, I will leave the screens in place. I have other areas to contend with for air flow. I doubt that the screens are a hinderence for me.

Mark.

 

Mark the screens inside the MAF are there for protecting the "hot wire" and to evenly distribute the air going through the MAF for a more accurate,consistant reading. Do a search on MAF screens & user name Vader. He covered all of this a year or so ago in a post.

 

I just read a bunch of posts which Jobryan referred to. I recommend that everyone interested in this read up on it. The following link is a good thread:
https://www.thirdgen.org/techbb2/sho...&highlight=MAF