Welcome to the North American Subaru Impreza Owners Club Tuesday November 25, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Factory 2.0L Turbo Powertrain (EJ Series Factory 2.0L Turbo)

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 10-30-2003, 10:04 AM   #1
nhluhr
John Wayne Toilet Paper
Moderator
 
Member#: 7327
Join Date: Jun 2001
Chapter/Region: NWIC
Location: Seattle, WA
Vehicle:
2008 Mazdaspeed3
2006 Wrangler Sport

Default stock vs aftermarket can of worms (very long)

first and foremost, please read the whole thing before you reply

The purpose of this thread is to completely overhaul the theory behind the stock intake vs the aftermarket intake on a WRX.

I've heard from many tuners that an aftermarket intake is useless, but what I am about to reveal is a simple little experiment that I used as a metric to prove to myself that the stock airbox is in fact quite restrictive and that there is definitely room for improvement on even low and mid horsepower applications.

For some background, i've tried about 15 different intake configurations and I've made lots of observations of each. I've had a "ram" setup funneling air from the stock fog-light hole, i've had the "hacked silencer", i've had the APS cold air intake, etc. Just about every thing under the sun. My car is a roughly 300hp at the crank setup utilizing a VF35, which does spool slower than the stock WRX turbo, but quite a bit faster than the VF30 or bigger turbos. I have a TurboXS turboback with 1 cat in place, as well as samco intercooler hoses and the like.

I do not recommend that anybody tries this experiment. My "test" was basically to remove the air filter from the stock airbox. I did this on a clean, quiet, moist night when the air quality was about as clean as it ever gets around here. I made sure to do it during this time because I didn't want my car inhaling too much unfiltered particulate from the air.

I know that running without a filter is NOT a good idea and that it is potentially very harmful to the engine. Again, i'm NOT recommending that you run without a filter. I just wanted to perform this quick little change to see what the difference is. What I was trying to learn is how much the restriction of an air filter in the inlet stream affected the car's characteristics, including throttle response, boost lag, boost threshold, low-mid-high range torque, etc. I monitored everything that I could, using an EGT gauge, Boost gauge, a/f gauge, and all the stock instruments and my butt dyno.

With this test, I was hoping to illustrate that the stock air filter is the single most significant restriction in the stock inlet path. What this would mean is that obvious improvements (of some form) could be made by reducing that restriction. This reduction would be reduced not by everybody removing their air filters (that's crazy!) but rather by increasing the surface area of their air filters. This would mean a larger airbox, a huge cone filter, etc.

In the following post, I'll expand on why restriction before the turbo is a bad thing as well as present my "findings".
* Registered users of the site do not see these ads.

Last edited by nhluhr; 10-30-2003 at 02:03 PM.
nhluhr is offline   Reply With Quote
Old 10-30-2003, 10:09 AM   #2
nhluhr
John Wayne Toilet Paper
Moderator
 
Member#: 7327
Join Date: Jun 2001
Chapter/Region: NWIC
Location: Seattle, WA
Vehicle:
2008 Mazdaspeed3
2006 Wrangler Sport

Default

If you don't see how it could be a huge improvement, Look into Maximum Boost and pay close attention to the first few paragraphs of Chapter 14 "Testing the System" where Bell goes to great lengths to point out how dramatic even a 2psi drop in the inlet pressure (which has been measured as realistic in a WRX) can affect the overall turbocharger system from a pressure ratio / efficiency / knock resistance standpoint.

To sum it up, he brings the following points to light:

Turbos operate on a basis of pressure ratios. Typically, compressor maps are given as efficiency based on a certain CFM flow at a certain Pressure Ratio.

The pressure ratio is simply the ratio of the output pressure to the input pressure such that:

(output absolute pressure) / (input absolute pressure) = PR.

If the turbo is being fed air at 14.7psi (ambient) and your "boost" is 14.7psi, this means the output absolute pressure is 14.7+ambient and input absolute pressure is 14.7 so the pressure ratio is:
(14.7+14.7)/(14.7) = 2.0

Now, turbo boost is controlled relative to AMBIENT pressures and not relative INTAKE pressures, meaning, the pressure in the intake tube may be lower than ambient and can therefore cause some changes:

say your intake has a restriction of "2psi" such that intake absolute pressure is 12.7psi while you are still boosting to 14.7 (29.4 absolute). Your pressure ratio now would look like:

(14.7boost + 14.7ambient) / (14.7ambient - 2restriction) =

(29.4) / (12.7) = 2.3

The higher pressure ratio means the turbo will operate in a lower efficiency range and as a result, make hotter intake temperatures. So you see, having a restrictive intake may still allow you to reach the same boost level but at the cost of compressor efficiency, meaning all else held the same, a restrictive intake will result in hotter intake charges reaching the manifold.

SO why not improve intake air flow? You've gotta know that at high flow rates you DO get a little bit of restriction in the stock setup.

Oakos Automotive used a manometer (pressure gauge) to measure the actual restriction in his stock WRX intake before he installed an AEM Cold Air Intake. He found the difference between the intake pressure (near the maf) and the ambient pressure to be .938 PSI

<sigh - work calls, be back shortly to finish this>

Last edited by nhluhr; 10-30-2003 at 10:15 AM.
nhluhr is offline   Reply With Quote
Old 10-30-2003, 10:32 AM   #3
streetspanker
Scooby Newbie
 
Member#: 31938
Join Date: Jan 2003
Chapter/Region: MAIC
Location: detroit area, MI
Vehicle:
2003 WRX
Blue

Default

keep it coming, this is interesting...

i've heard that an intake will lean you out somewhat.

i'm still a bit of a n00b when it comes to the math behind a turbo, but i figure i'd rather be running a little bit farther out of efficency range (hotter charge temp), and still run a little rich than to be getting colder boost, and potentially leaning out, that is i'm still running the stock ecu. if i had a good way to compensate (or maybe i do and i dont know it) i'd get an intake. right now i just dont want to knock.

correct me if i'm wrong on any of this, as i'm still learning the whole turbo tuning thing.

Spanky
streetspanker is offline   Reply With Quote
Old 10-30-2003, 11:47 AM   #4
nhluhr
John Wayne Toilet Paper
Moderator
 
Member#: 7327
Join Date: Jun 2001
Chapter/Region: NWIC
Location: Seattle, WA
Vehicle:
2008 Mazdaspeed3
2006 Wrangler Sport

Default

<to finish up the above>

as I was saying, Oakos measured a drop of nearly 1psi inside the STOCK inlet. This measurement was made near the MAF even before the air is forced through the admittedly bad-looking "turbo inlet pipe" with its two accordian sections, thin cross sectional area, and its abrupt directional changes.

So, it might be reasonably assumed that with the additive pressure drop of the entire intake system before the turbo, you are seeing a pressure loss of perhaps 1.5 psi. Now, it is important to note that when Oakos installed their AEM cold air intake, they more than halved the maximum pressure drop to 0.433 psi. That is pretty impressive, imho.

What you might expect from a less restrictive inlet is that more air is able to gush into the compressor with more immediacy according to throttle changes. This would result in possibly lower boost threshold (point where boost is attainable) and possibly lower lag (time it takes for boost to build when you floor it), not to mention improved throttle response throughout the rev and throttle range (more air available on short notice, all inertial effects considered).

No, I want to go ahead and say what I found out by removing my air filter that soggy night:

-The EGTs stayed probably about the same, with DEFINITELY no increase; a decrease if anything. It seemed that anytime I watched the EGT gauge, I wasn't seeing quite as high as my normal temps, but very close.

-The boost was probably .5psi higher, which is to be expected since I use a MBC which controls boost rather ineffectively compared to a sophisticated EBC that monitors MAP and constantly adjusts.

-The Air/Fuel meter stayed pegged rich anytime I was at WOT, which is to be expected given that it's a narrowband unit and doesn't have much resolution at the richer levels. However, in the past, using an APS cold air intake, the A/F gauge DID in fact read more lean than "pegged" so that is an indication that the APS, which caused the car to run lean enough for a CEL P0171, is more significant than my little experiment.

Through an observed increase in boost, similar/lower EGTs, and similar A/F readings between filterless and normal, I can reasonably conclude that my car was not running significantly leaner than normal.

Beyond gauge observation, I was also able to make several butt-dyno readings as well. I have a metric that I use as a fairly standard test and I've found that it makes for pretty repeatable results - enough so that i can tell the difference through my butt in a cold (40F) morning vs a mild (55F) evening.

What I do is set cruise control on a flat, straight road for 35mph in 2nd gear. Then, when I pass a certain marker (sign, tree, whatever), I floor the throttle and let it go to redline, paying attention to how immediate and how ultimately powerful the acceleration is.

-With the filter removed, there was a definite improvement in the immediacy of the acceleration - it happened almost in sync with the throttle opening. This is the closest I've ever been on a VF35 to feeling like the stock turbo.

-There was also a slightly noticeable increase in torque at redline, which is likely due to the slightly increased boost.

The results were reversible - replacing the K&N panel filter immediately returned things to normal. Still quite powerful and quite zippy with acceptable lag, but it didn't have the same crispness as my previous runs.

So, what does this test prove? What can I learn from it?

It proves (to me and those who trust my word) that the panel filter is the most significant restriction in the intake and causes a general "inductive" effect on the intake air - meaning it doesn't conclusively limit the total amount of airflow, but it just makes for slower changes in that airflow velocity. This would help to account for the many dyno tunes that haven't really shown an increase in peak hp but have shown a slightly fattened torque curve at lower rpms.

This information tells me a few things. As much as I would love to run around filterless all the time (because it's free and clearly effective), I just can't do that. I'm not willing to sacrifice that much safety for the power I get out of this. What I can do is think of ways to reduce the effect of this. The simple fact that my naturally aspirated 1.5liter Mazda Protege had the same size air filter tells me that a compromise was made here on the WRX.

The stock intake works great - no doubt about it. It is quiet, flows quite well, cleans the air fully, etc. But if you are willing try some things, you'll figure out a truly more effective induction system in a WRX.

Basically, what I have concluded is that whatever the peak hp gains of a CAI, rampod, etc that can be shown on a dyno, you will STILL notice better response, driveability, etc from a very free flowing intake. To make a better intake without sacrificing the filtering of the stock airbox, you need to use a LARGER air cleaner. I would strive for the largest surface area you can find. Maybe one of those big cones with the cone-inside-a-cone shape on the top? Perhaps one of those huge Airinx type dome devices... I haven't tested the aftermarket filters enough to say which is best.

There are of course many other factors that come into play in choosing an aftermarket intake. Those would include the choice between readily available hot engine air or lower pressure cold fenderwell air. Some might try ducting pressurized cool air (from the front of the car) into the fenderwell to provide a higher pressure cool air source for a CAI... some might try ducting cool air directly into a ram-pod. What I'm saying is that I don't really think the OPTIMUM aftermarket solution is out there yet. I think an optimal solution requires low volume (meaning, less piping), large surface area (meaning big filter), cool air (meaning a "box" or duct to seperate it from hot engine bay air), and of course safety (meaning good filtering, resistance to water splash, etc).

I hope nobody takes this as a presumptuous proclamation, but rather as a curious pursuit. Like I mentioned earlier, I have tried lots of different intake setups and they all have different characteristics that I won't go into here. I consider myself well qualified to make subjective observations. Also, it is apparent to me that an improvement in induction can only be good for the car in general. For instance, just feast your eyes on this dyno plot from avoturbo:


Keep in mind the difference between the two runs there is <1> the AVO inlet hose and <2> tuning to utilize it. You can see quite clearly that the MAP reading rises to pretty much full pressure far earlier with the inlet pipe on.

Anyway, I'm done with my posts... i'd like to hear from some of the true experts who have actually tried things.

Last edited by nhluhr; 03-04-2004 at 01:24 AM.
nhluhr is offline   Reply With Quote
Old 10-30-2003, 11:56 AM   #5
RiftsWRX
Scooby Guru
 
Member#: 6124
Join Date: Apr 2001
Chapter/Region: MWSOC
Location: Glendale Hts, IL, USA
Vehicle:
2000 NFR AP1 S2000
'07 Honda FIT sport (5MT)

Default

A lot more refinement to your testing procedure could be done (like on a dyno where actual figures can be controlled), but you've got the right idea.

Thanks for the good read!

Jorge (RiftsWRX)
www.ProjectWRX.com
RiftsWRX is offline   Reply With Quote
Old 10-30-2003, 12:06 PM   #6
nhluhr
John Wayne Toilet Paper
Moderator
 
Member#: 7327
Join Date: Jun 2001
Chapter/Region: NWIC
Location: Seattle, WA
Vehicle:
2008 Mazdaspeed3
2006 Wrangler Sport

Default

Quote:
Originally posted by RiftsWRX
A lot more refinement to your testing procedure could be done (like on a dyno where actual figures can be controlled), but you've got the right idea.

Thanks for the good read!

Jorge (RiftsWRX)
www.ProjectWRX.com
I'd love to have time and money to do dyno testing of this stuff. It's not realistic for me personally to do this. I do hope that somebody who is going in for a dyno tune will at least try some back to back a/b testing every once in awhile.

It seems to me that people are generally interested mostly in getting their setup tuned to its fullest and no more (in an effort to save money on dyno time), thus you have very very few actual A/B comparisons and we, the public, are left to heresay and extrapolated results.
nhluhr is offline   Reply With Quote
Old 10-30-2003, 12:18 PM   #7
ride5000
Scooby Guru
 
Member#: 32792
Join Date: Feb 2003
Chapter/Region: NESIC
Location: lincoln, ri
Vehicle:
2003 GGA MBP
12.9 / 105+

Default

Quote:
Originally posted by nhluhr
...The higher pressure ratio means the turbo will operate in a lower efficiency range and as a result, make hotter intake temperatures. So you see, having a restrictive intake may still allow you to reach the same boost level but at the cost of compressor efficiency, meaning all else held the same, a restrictive intake will result in hotter intake charges reaching the manifold.
much good stuff. i know you are not finished, but i'd like to take this as a good point to interject that there's another secondary effect of a higher cold side pressure ratio--and that is a higher hot side pressure ratio. in effect, by having a restrictive intake you will increase exhaust gas back pressure. this is never a good thing!

it's also what makes the intake before the turbo and the exhaust after the turbo equally important. everyone spends a lot of time thinking about their exhaust systems--it's nice to see some more attention paid to the intake side.

interested to hear more..

ken
ride5000 is offline   Reply With Quote
Old 10-30-2003, 12:23 PM   #8
nhluhr
John Wayne Toilet Paper
Moderator
 
Member#: 7327
Join Date: Jun 2001
Chapter/Region: NWIC
Location: Seattle, WA
Vehicle:
2008 Mazdaspeed3
2006 Wrangler Sport

Default

Quote:
Originally posted by ride5000
much good stuff. i know you are not finished, but i'd like to take this as a good point to interject that there's another secondary effect of a higher cold side pressure ratio--and that is a higher hot side pressure ratio. in effect, by having a restrictive intake you will increase exhaust gas back pressure. this is never a good thing!
I'm pretty much done with my "diatribe" now and I'm hoping for lots of educated discussion... tell me more about the hot side's pressure ratio increasing with cold side... I don't really "see" how it happens. What's the working mechanism there?
nhluhr is offline   Reply With Quote
Old 10-30-2003, 12:25 PM   #9
Jon [in CT]
*** Banned ***
 
Member#: 2992
Join Date: Nov 2000
Chapter/Region: NESIC
Location: Connecticut, USA
Vehicle:
02 WRX Sedan
Silver

Default

Quote:
Originally posted by nhluhr
I consider myself well qualified to make subjective observations.
I won't argue that point, except to say that the people you complained about at the top of the thread are just as adept at making subjective observations as you. You've "proven" nothing. Objective measurements recorded on a dyno are necessary to distinguish whether screwing around with the intake system improves performance, and to what degree.
Jon [in CT] is offline   Reply With Quote
Old 10-30-2003, 12:31 PM   #10
nhluhr
John Wayne Toilet Paper
Moderator
 
Member#: 7327
Join Date: Jun 2001
Chapter/Region: NWIC
Location: Seattle, WA
Vehicle:
2008 Mazdaspeed3
2006 Wrangler Sport

Default

Quote:
Originally posted by Jon [in CT]
I won't argue that point, except to say that the people you complained about at the top of the thread are just as adept at making subjective observations as you. You've "proven" nothing. Objective measurements recorded on a dyno are necessary to distinguish whether screwing around with the intake system improves performance, and to what degree.
a fair enough assessment - I think perhaps what might seperate me from the others I complained about is that i took the time to think this through and have tried to actually back up my ideas with logic and observations, instead of regurgitating something I read here on nasioc or a tuner website. Jon, I really hope you'll add insight to this...
nhluhr is offline   Reply With Quote
Old 10-30-2003, 12:32 PM   #11
ride5000
Scooby Guru
 
Member#: 32792
Join Date: Feb 2003
Chapter/Region: NESIC
Location: lincoln, ri
Vehicle:
2003 GGA MBP
12.9 / 105+

Default

Quote:
Originally posted by Jon [in CT]
I won't argue that point, except to say that the people you complained about at the top of the thread are just as adept at making subjective observations as you. You've "proven" nothing. Objective measurements recorded on a dyno are necessary to distinguish whether screwing around with the intake system improves performance, and to what degree.
as far as whether or not it improves performance, you'd really have to be thick to think that it does not!

it is a simple matter of making the compressor pressure ratio lower.

are you saying that a turbo that has to do less work isn't always a "good thing?" that's like saying a port and polish on the intake and exhaust tracts (assuming it is done correctly) isn't always a good thing.

i agree that the question remains to what degree is the improvement... but i stand by the assertion that making an engine breathe better is never going to yield negative results.

jm2c
ken
ride5000 is offline   Reply With Quote
Old 10-30-2003, 12:35 PM   #12
nhluhr
John Wayne Toilet Paper
Moderator
 
Member#: 7327
Join Date: Jun 2001
Chapter/Region: NWIC
Location: Seattle, WA
Vehicle:
2008 Mazdaspeed3
2006 Wrangler Sport

Default

Quote:
Originally posted by ride5000
as far as whether or not it improves performance, you'd really have to be thick to think that it does not!

it is a simple matter of making the compressor pressure ratio lower.

are you saying that a turbo that has to do less work isn't always a "good thing?" that's like saying a port and polish on the intake and exhaust tracts (assuming it is done correctly) isn't always a good thing.

i agree that the question remains to what degree is the improvement... but i stand by the assertion that making an engine breathe better is never going to yield negative results.

jm2c
ken
Keep in mind that you have inefficiency on both sides of the compressor map, both "working too hard" and "not working hard enough" will cause a turbo to compress less efficiently.



See, clearly, if you are not in a specific range, you are not at peak efficiency.

Last edited by nhluhr; 03-04-2004 at 01:25 AM.
nhluhr is offline   Reply With Quote
Old 10-30-2003, 12:49 PM   #13
LargeOrangeFont
Scooby Specialist
 
Member#: 28475
Join Date: Oct 2002
Chapter/Region: SCIC
Location: So Cal
Vehicle:
86 RX-7, 07 Yaris,
2010 CTS-V

Default

This my be slightly OT, But I run a GP MOTO short ram intake.

I did a couple contrilled experiments monitoring intake temperatures between stock intake, and the GP moto intake. The stock intake pulled the COOLEST air at a standstill as well as while driving. The GP MOTO short ram w\ all stock components removed (stock scoop and resonator elbow) ran only a degree hotter while crusing, but rose 20-30 degrees hotter at a stand still. This shows a definate need to make some sort of isolating box when using a short ram intake. While crusing at 70 MPH on a 90+ degree day we saw temps of 92~94 (91~93 w\ stock intake) but intake temps soared to 140+ while at a standstill (about 112 stock).
What is very interesting is that when we put the stock scoop on w\ the short ram temperatures while crusing WENT UP by 15 degrees. Definately don't use the stock scoop w\ a short ram intake.
This weekend I will be testing again the stock intake, the GP MOTO short ram, as well as a K&N typhoon cold air intake. I will post my findings next week. We now have the ability to measure flow of air as well as temperature so it should be interesting.
LargeOrangeFont is offline   Reply With Quote
Old 10-30-2003, 12:51 PM   #14
ride5000
Scooby Guru
 
Member#: 32792
Join Date: Feb 2003
Chapter/Region: NESIC
Location: lincoln, ri
Vehicle:
2003 GGA MBP
12.9 / 105+

Default

Quote:
Originally posted by nhluhr
I'm pretty much done with my "diatribe" now and I'm hoping for lots of educated discussion... tell me more about the hot side's pressure ratio increasing with cold side... I don't really "see" how it happens. What's the working mechanism there?
the mechanism, in a nutshell, can probably best be understood from an energy or thermodynamic standpoint. at least this works best for me and my limited expertise.

the energy requirements and supplies can be thought of as the pressure ratios and flows through each of the two sides. to create larger pressure ratios and/or larger mass flow rates requires more energy.

for our intents and purposes, the turbo can be thought of as a closed system. energy is supplied by the exhaust gas, in particular, the pressure ratio across and flow through the hot side, and it is taken up by the act of compressing the charge on the cold side, again defined by a pressure ratio and flow mass. since we have no other sources of energy they are inextricably linked... as one goes up, so must the other.

i believe it was azscooby that threw out a ballpark figure for how great the EGBP was for our OEM turbos.. from 2 to 3 times the intake pressure, iirc. thus, for an intake pressure of 15psig, you'd have an EGBP of 30 to 45psig. (no wonder uppipes are fussy about gaskets!) obviously different turbos will have different ratios, but they're NEVER close to 1:1. there are too many losses in the system.

hth
ken
ride5000 is offline   Reply With Quote
Old 10-30-2003, 12:53 PM   #15
ride5000
Scooby Guru
 
Member#: 32792
Join Date: Feb 2003
Chapter/Region: NESIC
Location: lincoln, ri
Vehicle:
2003 GGA MBP
12.9 / 105+

Default

Quote:
Originally posted by nhluhr
Keep in mind that you have inefficiency on both sides of the compressor map, both "working too hard" and "not working hard enough" will cause a turbo to compress less efficiently.
...
See, clearly, if you are not in a specific range, you are not at peak efficiency.
you're right. i was oversimplifying things a bit too much.

most of the time, though, i think our problems lie on the right side of that graph, not the left!

(i do have to say that the chart is only taking into account the compressor efficiency. for example, i don't think there's enough flow on the hot side to net you an intake PR of 2 at 100cfm. then again, i am not sure of this.)

ken
ride5000 is offline   Reply With Quote
Old 10-30-2003, 12:54 PM   #16
LargeOrangeFont
Scooby Specialist
 
Member#: 28475
Join Date: Oct 2002
Chapter/Region: SCIC
Location: So Cal
Vehicle:
86 RX-7, 07 Yaris,
2010 CTS-V

Default

Quote:
Originally posted by ride5000
as far as whether or not it improves performance, you'd really have to be thick to think that it does not!

it is a simple matter of making the compressor pressure ratio lower.

are you saying that a turbo that has to do less work isn't always a "good thing?" that's like saying a port and polish on the intake and exhaust tracts (assuming it is done correctly) isn't always a good thing.

i agree that the question remains to what degree is the improvement... but i stand by the assertion that making an engine breathe better is never going to yield negative results.

jm2c
ken
I agree. I think that it will be hard to test intakes on a DYNO and see any real world numbers that we can use to make a educated decision. What we need to do is put the dyno inside a wind tunnel.
LargeOrangeFont is offline   Reply With Quote
Old 10-30-2003, 01:06 PM   #17
shields102
Scooby Newbie
 
Member#: 9598
Join Date: Aug 2001
Location: westland mi
Vehicle:
02 wrx
white

Default

I to have always found it hard to swallow that a decrease in intake restriction, no matter how small, could be a bad or useless thing. But I also feel there are additional factors at play. Although the stock intake "system", may not do a great job of providing ultimate flow, it does do a very good job of smoothing the flow it does produce. Reguardless of "maf tube calibration" and all the talk of incorrectly sized or scaled intakes; increased flow often brings with it increased turbulence. That turbulence can effect the stock maf which is designed with only a certain amount of flow in mind.....I have no idea what the makers had in mind as a limit, but i do know that the same part number is on the current toyota mr2's........and they arn't flowing a heck of a lot of air. The effects of the turbulence on a maf read-out, is a jagged line as opposed to a smooth curve.

I am not saying that certain doom waits around the corner with more efficiant flow. What i would like to see is aftermarket intakes with proper maf housings and devices to smooth flow before the maf.

Sorry about any spelling.
shields102 is offline   Reply With Quote
Old 10-30-2003, 01:15 PM   #18
shields102
Scooby Newbie
 
Member#: 9598
Join Date: Aug 2001
Location: westland mi
Vehicle:
02 wrx
white

Default

I realize this could be seen as more nasioc myth; however, i know Tony (x99percent) and Tom Payne. This testing was done in hopes on IMproving, not DISproving intake mods.

Posted by X99percent,

Early this year, I handed my stock intake over to Pro-Flow (I could be wrong about the name), along with an AEM CAI from Payn (a local tuner) for testing.

The stock intake has a lot of pressure drop vs. an AEM CAI. Remove the silencer from the system, and there is less pressure drop, but you get more MAF signal "noise". Install an aftermarket intake, and the pressure drop is significantly reduced, but the MAF noise is greatly increased... they didn't even finish testing the AEM.

BUT.. the noise wasn't that bad under WOT conditions with the AEM... leading me to think that a car with an AEM CAI would have some part-throttle quirkyness, but may be stronger at WOT.
shields102 is offline   Reply With Quote
Old 10-30-2003, 01:15 PM   #19
AZScoobie
Scooby Guru
 
Member#: 8785
Join Date: Jul 2001
Chapter/Region: SWIC
Vehicle:
02 c_turner@ix.
netcom.com

Default

N, Nice to see your enthusiastic about this. The biggest point that alot people seem to overlook of just forget is that these cars use a load reference of Mass air flow. The MAF sensor, the intake pipes and even the filter provide the ECU with a load reference. Altering any part of this system alters this load reference.

Anyone that has ever removed the filter on the dyno and made another pull can attest to this. Try it on a new STi and lose an instant 20Whp.

This is because the MAF sensor to the ECu was calibrated with the filter and the stock pipes hooked up. The filter smooths airflow... Its a smoothing "gate" if you will.

I will not suggest that a short ram or other intake can flow more air but I will suggest that you will screw up the load reference to the ECu causing lean and rich spots and poor fuel trims. Sometimes you get lucky and your intake causes a rich condition in certain areas which implies a larger negative AF learing figure which in turn removes fuel from open loop WOT pulls... This woud give you some hp if you car was running rich... Other times you get the oposite.

A few weeks back I trapped 117mph with the stock intake and box. I have also made well over 500hp with it. I have tried intakes including the worst(AEM) and my opinion is that a stock box is the best you ever going to get.

Clark
AZScoobie is offline   Reply With Quote
Old 10-30-2003, 01:22 PM   #20
Vision
Scooby Newbie
 
Member#: 24964
Join Date: Sep 2002
Chapter/Region: Tri-State
Location: NYC
Vehicle:
2oo2 WRX
PSM

Default

Clark, do you have any experience with the arc induction box for the wrx ?. The design is very similar to stock and it has a slightly larger panel surface area.
Vision is offline   Reply With Quote
Old 10-30-2003, 01:28 PM   #21
shields102
Scooby Newbie
 
Member#: 9598
Join Date: Aug 2001
Location: westland mi
Vehicle:
02 wrx
white

Default

What clark mentioned about scaleing and fuel trim is interesting.....while data logging after my perrin turbo inlet pipe was installed (a week had passed) we noted that my fuel trim was not trimming at all, but adding fuel? Related?
shields102 is offline   Reply With Quote
Old 10-30-2003, 01:31 PM   #22
mlambert
Scooby Guru
 
Member#: 13831
Join Date: Jan 2002
Location: 99 problems but a bitch aint 1
Default

Has anyone (besides shiv) ever said that good intakes wont help a high horsepower car make more power, even the wrx? If you can properly tune around maf inconsistencies that can show up with aftermarket intakes, the end result will be more power if its properly designed. I always figured this to be common knowledge since the APS intake hit the market way back when cobb was selling their stage kits.

The auto replies about intakes (which I have done alot of) are to help keep idiots from killing their ej's.

Hope you dont take this the wrong way as this forum needs more people doing proper testing and reporting but I agree with jon.
mlambert is offline   Reply With Quote
Old 10-30-2003, 01:44 PM   #23
nhluhr
John Wayne Toilet Paper
Moderator
 
Member#: 7327
Join Date: Jun 2001
Chapter/Region: NWIC
Location: Seattle, WA
Vehicle:
2008 Mazdaspeed3
2006 Wrangler Sport

Default

Quote:
Originally posted by AZScoobie
This is because the MAF sensor to the ECu was calibrated with the filter and the stock pipes hooked up. The filter smooths airflow... Its a smoothing "gate" if you will.

Clark
Clark, this reminds me of something I saw on the ecutek website. Referencing http://www.ecutek.com/tuning/induction/ , they found that different intakes (or more spefically, different maf housings) were useful in lowering the MAF voltage (to tune for higher airflow) but at the same time found that they dramatically changed the shape of the voltage:airflow curve, which means a total recalibration of the engine control system is in order to properly utilize the larger maf housing.

nhluhr is offline   Reply With Quote
Old 10-30-2003, 01:46 PM   #24
lotusdrift
Scooby Specialist
 
Member#: 24308
Join Date: Sep 2002
Chapter/Region: MAIC
Location: HR
Vehicle:
Oh, **** it
I'm gonna have a party

Default Re: stock vs aftermarket can of worms (very long)

Quote:
Originally posted by nhluhr
[b]so, ever ask a simple question about aftermarket intakes and have some automaton forum subscriber tell you that the tuners haven't seen any gains from aftermarket intakes and therefore it is impossible (or at least unlikely) that gains do exist?
I take great offense to that, as not only did you not once form a single cohesive argument for your case, you sijmple reverted to name calling and stating your education background as if that somehow made your 'evidence' more applaudable (laughable).

Now you come in here, running away from my direct challenges to show any ounce of proof. I would love to have an intellectual conversation about the topic, but show me once in the other thread where you even attempted that. The conversation on your part was not only far from intellectual, it was merely superstition based on your asanine observation that you gained power by TAKING OUT YOUR FILTER! No **** sherlock.

I challange you once again, removing your filter and getting gains is not a case agains the intake but rather just a simple inherently known fact that filters are NOT free flowing.

Furthermore, the case was made in agreement with you that larger surface area filters would indubitely be beneficial, IF IT COULD BE CORRECTLY TUNED FOR.

What exactly do you want to argue here, that you came up with some great new theory on fluid dynamics based on your thourough past history of dedicated study....or that you too are merely REGURGITATING a very known and self evident wisdom on one of the very first things to do to an automobile to increase performance. PULL THE PLUGS, clean out the exhaust and intake. Thats the first thing people of course tried with the wrx, but found it was not just a simple step anymore thanks to electronics and sensors. It has now become an expensive step, with tuning required for gains (which might be very minimal at that), which makes it NOT A WORTHWHILE MOD.

you sir are a jerk.


and for anyone else, please refer to MID-A forum if you want to know what thread I am referring to.
lotusdrift is offline   Reply With Quote
Old 10-30-2003, 01:46 PM   #25
nhluhr
John Wayne Toilet Paper
Moderator
 
Member#: 7327
Join Date: Jun 2001
Chapter/Region: NWIC
Location: Seattle, WA
Vehicle:
2008 Mazdaspeed3
2006 Wrangler Sport

Default

so with what's been said about MAF "noise" and what I'll call turbulence warble (varying of maf voltage due to the lack of the smoothing effect of the air filter), I wonder if it would be possible to use, as I have suggested, a HUGE air filter upstream, coupled with a large-mesh screen downstream to "smooth" the air flow before the MAF.... Of course, introducing a screen to the path would have to be a significant restriction, but I wonder if it would work and also if it would be too much of a trade-off?

-nick
nhluhr is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Can of WORMS kelsey Newbies & FAQs 4 10-20-2007 02:36 PM
Holy cow a can of worms just opened up trustWRX Off-Topic 13 09-01-2004 01:18 AM
A can of worms Dave_MacKinnon Brakes, Steering & Suspension 3 02-02-2002 05:52 PM
Opening the gear oil can of worms again. cvalle-sd Normally Aspirated Powertrain 4 05-18-2001 01:24 AM


All times are GMT -4. The time now is 11:29 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.