De-snorkal a NA car?

[Legachy]

Is it a good idea to De-snorkal a NA Legacy? also, will I notice any difference in sound?(I would like some intake noise ) And is there anyway I could make the intake noise more louder aswell?

Also, would it be such a bad idea to add a pod filter instead?

Thanks

[86ruguy]

I had a cone filter on an N/A wagon and it didn't have any adverse affect until I took it through a couple of mud holes.

IMO..It doesn't hurt and it was way louder.

[kid420]

from what ive been reading the stock air-box is pretty efficient, especially running in a N/A vehicle

[BXSS]

I desnorked my wife's OBS.

First I put a drop-in Perrin air filter on the car which gave a small but noticeable gain (she noticed it on her first drive & asked why the car felt zippy).

Then I desnorked the airbox & enlarged the inlet from 2" to 4".

It is way LOUDER on WOT & it feels a bit quicker than the drop-in filter alone.

[ciper]

Snorkulectomy = BAD

I would like everyone to look at this thread http://forums.nasioc.com/forums/showthr ... ?t=1471819

Specifically the third and fourth image.

[Legacy777]

I'm not sure how applicable that is to the first gen legacies.

To test it someone with an n/a motor would need to watch the alpha correction # on the select monitor or Vikash's ECU scanner program to see if the number goes severely negative anywhere in the rpm/load range.

[Soul Shinobi]

That really was an interesting read though. I'll try to check it on the scan tool program myself sometime.

I removed my snorkus on my 2.2L NA, then cut a larger hole in my airbox and GOD it's loud! I cut the hole too big I think, and I wish I hadn't cut it at all; I actually want to put my snorkus back on so I can go full throttle without drawing much attention to myself.

I once heard this a while ago, and I find it true for myself; "The older I get, the more I appreciate my setup being quiet."

[smh0101]

I put a 90* rubber elbow out the hole into the fender and got the right diameter metal exhaust pipe and ran it down fender.... the fender liner helps so water doesnt get sucked up but it has a noticable gain... because there is no fog light cup... so air is forced in.

[Soul Shinobi]

I've thought about doing that, but I'm concerned about what might happen when it rains. Of course, I could just be careful, but having AWD makes you want to be very not careful in poor weather!

[smh0101]

But you can still find yourself ass over tea kettle in the rain with an AWD car...

Remember, AWD doesnt help you stop!!

AndI havent had any wet MAF problems since doing the mod.

If your really concerned, put a drip loop in it with a hole drilled in the bottom.

[Soul Shinobi]

Little to no tire wear in the rain though

Anyway, with regards to the MAF signals, I had my brother sit shotgun with the laptop hooked up. My setup include the removal of the snorkus, a larger hole cut in the airbox, and the spacer where fog lamps would go removed (irrelevant to this testing since the testing is just at low speeds).

Now, below about 1,500 RPM, if I mat the throttle in first gear, the car bogs massively, MAF voltage shoots to 2.8-ish and engine load reads 100. I think that's the issue we're looking at here.

I actually thought that was normal operation (first thing I did when I got the car was remove the snorkus). But I suppose it's not.

To test it someone with an n/a motor would need to watch the alpha correction # on the select monitor or Vikash's ECU scanner program to see if the number goes severely negative anywhere in the rpm/load range.

I don't know what unit you were referring to, but like I said, MAF voltage shot up, and engine load hit the ceiling. I'll have to try again tomorrow and see what the fuel injectors do.

[ciper]

Now, below about 1,500 RPM, if I mat the throttle in first gear, the car bogs massively, MAF voltage shoots to 2.8-ish and engine load reads 100. I think that's the issue we're looking at here.

Did you ever know that you're my hero,
and everything I would like to be?
I can fly higher than an eagle,
For you are the wind beneath my wings.

[Soul Shinobi]

I'm so on the verge of understanding you that I'm both very amused and massively confused.


The issue seemed to get worse when I had made the opening in the airbox bigger. I'd like to test this a bit more extensively, but I'm not sure what more to do other than check Fuel Injector Duty Cycle...

... I've just realized what Legacy777 meant by "watch the alpha correction # ... to see if the number goes severely negative." He was referring to Fuel Trim (isn't it called lambda, not alpha?). That'd be better to watch than Duty Cycle. Not only if I could make some graphs like those ones ciper sourced from NASIOC. Guess we'd need a new program for that, oh well. OBD-II would help...

This just goes to show you that some kids with a ram pod are not one-upping the real engineers of Fuji Heavy Industries as they'd like to think they are (I'm not denying the benefits of a ram pod, just saying that they're far from the be-all-end-all). Subaru wasn't fooling around, as silly as the snorkus looks.

Anyway, I'll try to pinpoint this issue more on my car.

[Legacy777]

... I've just realized what Legacy777 meant by "watch the alpha correction # ... to see if the number goes severely negative." He was referring to Fuel Trim (isn't it called lambda, not alpha?). That'd be better to watch than Duty Cycle. Not only if I could make some graphs like those ones ciper sourced from NASIOC. Guess we'd need a new program for that, oh well. OBD-II would help...

Depending on what you look at, it's called different things. The FSM calls it "Correction Coefficient of air-fuel ratio (ALPHA)".

Vikash's scan tool may call it fuel trim
http://bbs.legacycentral.org/viewtopic.php?t=34119

Either way, that is what you need to look at. The testing you did really doesn't draw any conclusions yet. You may just have bogging issues due to opening up the intake. However if you do see a large negative alpha correction along with the bogging, then you could draw some conclusions that the intake system resonance issues on the new subarus may also be present in the older ones.

[Soul Shinobi]

Wow, his new scan tool is awesome. I'll see what fuel trim does sometime soon, hopefully today. I would think what I've found so far is somewhat conclusive, as I got very similar anomalies as those shown on both graphs. Though, I may mention that I'm not well versed in the details of these figures or exactly how engine management works.

[Legacy777]

Like I said, what you experienced is not conclusive. You've identified the problem...bogging. Which could be attributed to this problem, or the fact there's a sudden decrease is air in the intact track. It may be that the two are related,

But until you look at the alpha correction, it'd be difficult to say for sure.

Let us know what you find out.

[Soul Shinobi]

Alright, I was riding around with the laptop on Fuel Trim and I have no idea what it was trying to show me.

I got numbers like -2.xx% to -3.xx% on normal light acceleration, -7.xx% on off throttle coasting and when I went Wide Open Throttle (WOT) it would be dead set at 0.00% all the time, the only exception being the low end 'bog' range, where WOT threw a negative number (-3.xx% I think, really hard to read since I was reading it myself, no codriver) just for a second, then it would got to 0.00% but the car would be bogging just the same.

There's clearly a lot I don't understand. It's worth noting that I suspect my O2 sensor is not in great condition, but it is working.

EDIT: Okay thinking it over I do understand these results, I'm not totally lost. It's only what happens when I go WOT and bogging occurs that I don't understand.

[Legacy777]

The fuel trim number is basically a feedback loop for the fuel table lookup.

The ECU has a fuel table MAP it uses to determine how much fuel needs to be injected with a given amount of air. In open loop mode, that's more or less all the ECU uses to determine fueling. There's some small exceptions to this, like when the engine is cold, and during hard acceleration, in which the ECU has a separate "enrichment" table it uses to add a little more fuel for better drivability when the engine is cold, and a little more power for "overtaking" when the accelerator is "mashed".

However in closed loop mode, the above is taking place, but in addition, the O2 sensor is monitoring for excess oxygen, which indicates whether complete combustion is occuring or not. In closed loop, the ECU is shooting for an AFR of 14.7 to 1, and will continually try to add or remove fuel to get to that target AFR. If it has to remove fuel, you end up with a negative percentage fuel trim number. If it has to add fuel, you end up with a positive percentage fuel trim number.

As for the WOT readings. Really....there's shouldn't be any correction at WOT because it's completely open loop. Why exactly you're seeing a -3% at WOT bogging....I can't say.

However I'll ask the question, do you get any bogging without going to WOT?

Because of how our ECU's handle closed loop/open loop, I'm not confident that the bogging problem is the same, nor am I sure that we have any means to determine it based on what data the ECU is spitting out. Specifically, I don't think our ECU's stay in closed loop much at all, so looking at the alpha correction number is irrelavent in open loop.

[BXSS]

The wifes car bogged a little on WOT off idle on evening 1 of the snorkectomy, but by the next morning it ran perfectly.

A ECU reset with the snorkectomy would have probably prevented this all-together...

[Soul Shinobi]

Alright. I've gone out again, this time set to Injector Pulse Width.

Idle: 3.xxx ms
Off Throttle Coasting: 0.256 ms
On Throttle 'Cruising': 3.xxx to 5.xxx ms
Light to Moderate Acceleration: 5.xxx to 9.xxx ms
WOT Above 1,500 RPM: 14.xxx to 15.xxx ms (this seems to be the max*)
WOT Below 1,500 RPM (Bogging): 22.xxx to 24.xxx ms

*Note: Max number I got on level ground while being propelled forward, no counting the bogging range.

I tried to read the numbers for all of these on ground that was more-or-less level. I of course did measure more things than we needed, just for comparison so we can get an idea of the full range these figures operate at. What unit is ms by the way?

[cheno SLO]

What unit is ms by the way?

milisecond

[Legacy777]

Soul Shinobi,

Thanks for doing the testing. Since your max readings posted are based at WOT, the ECU should be in open loop, so it's getting fueling values from a lookup table, and any enrichment tables.

Do you still have your snorkel? Could you put it back in and see what you experience then?

[Soul Shinobi]

I do understand what you're saying, I'll see if I can test it further. I still have my snorkel, but I have cut a larger hole in the side of my airbox. I may be able to seal it up with duct tape. I'll see what I can do.

[Legacy777]

Yeah, use some duct tape & cardboard or something.

Let us know what you find out.

[Soul Shinobi]

THE DIFFERENCE IS NIGHT AND DAY

I set the intake to stock with delicate precision and Gorilla Tape. Now the car WILL NOT bog due to WOT, now matter how low the revs.

Injector Pulse Width: is 14.xxx to 15.xxx ms at WOT no matter how low in the revs I am. No longer does it jump to 22.xxx+ at WOT with low revs, and bogging is gone. I tried going as low as possible from a dead stop, and from the slowest crawl I could without stalling, and the car just picks up speed.

Noise: Noise is about the same at idle, but my normal accelerating (WOT 2,000 to 4,000 RPM) no longer sounds aggressive, and above 4,000 RPM no longer sounds like a mating call to policemen.

Drivability: Not having to worry about bogging on an aggressive start from stop is so relieving, it's great knowing the car will just go now. The engine is also smoother, I no longer feel the same vibrations through the accelerator pedal, almost none at all at some revs even at WOT. I didn't really expect that either, it caught me off guard.

Safety: The author of the NASIOC thread that ciper posted the link to put it well, and I have experienced what he describes (but no longer!): "... Imagine having the car in a low gear at idle in stop and go traffic. Suddenly, you see a chance to get into the faster moving lane next to you so you punch it. Right into the trouble spot." -williaty, NASIOC. It doesn't take much imagination to see how this could end up being more dangerous, for example trying to get out of the way of someone with no brakes, or brains (the latter being more common; people on cell phones comes to mind).