legacycentral bbs

so i had my stock legacy. Drilled the silencer. That made it noiser. I like it quiet. I put on a BIG cone air filter. Very noticable increase in power, but i had no torque below 2k rpms. Stoplights were a pain in the ass, i had to actually stop, and the car was LOUD. And so, desiring the torque and silence, but loving the hp gains, i have been working on this really wierd intake:

I made a corrugated plastic airbox with 3/4 inch particle board ends that the cone filter sits inside. On the O2 sensor side, there are 2 pieces of particle board sandwiching the filter flange. The whole box is sealed with silicone glue



Comming from the far end of the airbox, there are 2 holes, a la dual intake runners. one has a 1.5 foot long piece of 2 inch corrugated plastic tubing going from the box to right below the radiator, sitting on a piece of plastic down there. Long intake runner, lending itself to torque.

The other hole has a 2 inch pvc valve attached. Open the valve and it effectively doubles the airflow into the filter box. It's not cold air, but its behind the headlight, so it sure isnt warm, provided im moving. Short intake runner.

I have been using this design for about 2 weeks and have been happy with the results. neither mode quite matches a straight cone or a stock engine, but mileage is up and the difference between open and closed valve is definately noticable.

Probably too much work to be worth all my time engineering, but it was educational and it works. I'm going to clean up the design (aesthetically), and upon completion. Let me know what you folks think, or if you want detailed instruction/pics to do it yourself. Project cost: 15$

Can you posts some pics of your setup? I sorta have an idea of how things are, but am definitely more of a visual person.

If you don't have a place to host them, email them to me.

BTW, its not 02 sensor its a AFM or MAF (depending on who you ask)

I thought it was a MAF... It was my understanding that AFMs measure air flow with a flapper or somesuch while MAFs measure air mass with some kind of electrical magic.

I've never heard of a flapper-type measuring instrument. The only two I know of are:
MAF (Mass Air Flow): measures amount of air based on a heated element (foil or wire). The computer keeps the element at a certain temp range and depending on the amount of current's needed to keep the wire heated, the ecu will know how much air is going through the sensor.

MAP (Manifold Absolute Pressure): measures the amount of absulte pressure in the intake manifold. Based on preset determinants by the factory (using temp sensors and such), the computer will use a series of calculations to figure out how much air is coming into the engine.

vrg3: MAF is the more technical term, meaning Mass Air Flow while AFM is the end user tech term for Air Flow Meter.

The flapper and heat wire type are both the same AFM/MAF

The flapper style is not very accurate. It uses a spring and a variable resistor to measuer air flow.

Ours works because the tube is a calibrated size. It measures the amount of air passing over a small area (at the sensor) then multiplies this.

This is the exact reason why cone filters can hurt performance, any error is multiplied many times by the sensor.

no digital camera, and its really pretty ugly. If i beautify it, and redesign i will take some pictures. I think i may swap the corrugated plastic box for a PVC pipe one.
...........MAF \/ ______
------------------\ .........=+ short intake runner with on/off valve
to engine...0...l..........l
------------------/_____=============== long intake runner
......................^cone


thats the best i can do for a diagram. Dont ask me to draw it in the car

If you really want to test the performance of this intake its pretty easy.

Create a water gauge to measure the vacuum. Take a stick and run plastic tube down one side and up the other. Fill it a little less than half way with water. Attach one side to your intake JUST before the throttle plate.

This is an accurate poor mans anti boost guage.

boostjunkie wrote:I've never heard of a flapper-type measuring instrument.

These exist, they are however called volume flow meters.

There is a little flapper door that is drawn open by the intake vacuum. It's position I believe is then given to the ECU and it does it's magic and tells how much air is going in the engine. Yeah it's not the best way. I don't think many vehicles use it any more. It was on my mom's 90 yota pickup.

MKIII Toyota Supra non turbo use them. Also Cressida with the 7mge engine.

And MkII Supras (at least with the 5MGE) as well... My brother's '85 has a flapper-door flow meter.

And 1979 1/2-1986 Jaguar xj6's. Actually, probably a lot of older european cars.

All systems based on Bosch's L-Jetronic EFI use them. Another term for a flapper door airflow meter is VAF: vane airflow meter or sensor.

They typically have temperature sensors built in, so their EFI essentially behaves like a speed density system (fueled based on MAP and MAT), except much more restrictive and much less accurate. :)

Back from the dead This post is a year old already!

Yeah... back from the days when I used to use e-mail notification. :)

vrg3 wrote:All systems based on Bosch's L-Jetronic EFI use them. Another term for a flapper door airflow meter is VAF: vane airflow meter or sensor.

Actually I think it's Volume Airflow meter, or at least that's what my mom's yota manual called it.

Mazda called it a vane airflow meter.

Same difference.

ehhh...same thing....different manufactures....bastards

Hmm, but this requires actually getting out of the car to adjust the runner, yes?

You need an automatic setup, similar to what Ford used on the SHO with their secondaries.

Essentially, on the SHO, there are long and skinny runners called the primaries. Under throttle, these are open and air is running through them (nice torque).

At 3400RPM, there is a flapper valve that closes the primaries and opens the secondaries. Short, wicked fat runners that dump right into the cylinder. Top end like nobodies business.

If any of you have had the pleasure of riding in an uncorked SHO, you would know the glory of the secondaries.

THIS is what I thought you were talking about. An automated system to increase airflow getting to the filter by way of a flapper valve or something of the sort. Just like a secondary throttle body or like an exhaust cutout to switch from one intake runner to another.

BAC5.2 wrote:Hmm, but this requires actually getting out of the car to adjust the runner, yes?

You need an automatic setup, similar to what Ford used on the SHO with their secondaries.

Essentially, on the SHO, there are long and skinny runners called the primaries. Under throttle, these are open and air is running through them (nice torque).

At 3400RPM, there is a flapper valve that closes the primaries and opens the secondaries. Short, wicked fat runners that dump right into the cylinder. Top end like nobodies business.

If any of you have had the pleasure of riding in an uncorked SHO, you would know the glory of the secondaries.

THIS is what I thought you were talking about. An automated system to increase airflow getting to the filter by way of a flapper valve or something of the sort. Just like a secondary throttle body or like an exhaust cutout to switch from one intake runner to another.

What you're describing is a variable-length intake manifold. A lot of manufacturers use this sorta setup . . . actually, I belive the svx used a variable intake manifold setup!!

My vote for the best SHO engine is the yamaha 6-cyl. The engine was WAAAAY overengineered. Capable of about 350hp (mind you this was back in the early 90s) but detuned to about 250hp(?). You might be asking why Ford had yamaha detune the engine?

Because Ford didn't have any fwd transmissions that could hold up to that much hp/tq!!! LOL! Ford=stupid! They had such an incredibly designed engine that was capable of soooo much more. This engine also employed variable-length runners. I believe Porsche also uses a design similar to the Ford one you described.

Is it no wonder why I chose this GT-S? The engine was a joint project by Yamaha and Toyota. Toyota reliability + Yamaha efficiency = teh sex!

Still trying to find out if the engine compares to the ej22t, tho.

heh, variable intake manifold doesnt describe it. Depending on load and rpms and all kinds of other shit the SVX coudl actually close half the manifold and run on three cylinders! Least that's how I understood it, it may be actually work differently. The ej20g alsso had variable intake, and so do impreza wrx's.

THAWA wrote:heh, variable intake manifold doesnt describe it. Depending on load and rpms and all kinds of other shit the SVX coudl actually close half the manifold and run on three cylinders! Least that's how I understood it, it may be actually work differently. The ej20g alsso had variable intake, and so do impreza wrx's.

Just curious where you got this information......I've never heard of anything like that, nor have I seen any control valve or setup that could do this when looking at an svx motor.

In these two articles:
http://209.197.75.192/articles/article1.html
and
http://209.197.75.192/articles/article2.html

So my memory was a little sketchy...

Jason, when Roman gets the SHO fixed, you can see what the V8's are made of. He has zero intake restriction (i.e. Throttle body is attached directly to the MAF which is attached to the cone) and some exhaust work done.

The Secondaries make you shudder they are so loud.

Ford detuned it for a few reasons. The tranny issue like you said (simply put, the diff would shoot a pin right through the housing. I've never seen a SC SHO running the stock diff. Every single 2G SC or Turbo SHO has a Quaife or other LSD).

The other reason is that Ford didn't want the V6 SHO to be faster than the 5.0L and 4.6L Mustang GT. The 1991 SHO Plus was good for a high 14, stock. Which is just enough to put the scare to a stock 5.0L. Fully tuned, the stock 3.0L V6 (the automatics got a 3.2L V6) SHOULD make around 350 is the best guess we can make. There is no such thing as a "retune kit" though, and Yamaha wouldn't release the original cam specs and all of the other tune variables.

It still kind of scares me to see a DOHC V8 rev to 7k. Sure is cool though.

I don't know of any other car that uses the runner setup like an SHO.

Here's a pic of Roman's intake setup. The Secondaries are LLLOOOOUUUDDDD.

Is it possible that certain non-USDM SVXes got the variable length intake runners, while ours didn't? Kind of like with VTD?