Injen or similar CAI - does it increase power? (was: need help all u pros)
01-09-2006, 10:16 AM
#16
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Posts: 10,118
Car Info: 2005 Pooparu
Intake FAQ
The primary purpose of an aftermarket intake is to increase the amount of air flow the engine receives.
HP gain is 0-15HP. These HP figures are a range as different intakes have different dyno results.
What is an aftermarket intake? Aftermarket intakes can be broken down into two types:
1. Short ram: AKA shorty or ram pod.
2. Cold air intake: AKA CAI.
What does the stock intake look like? To gain a perspective on how aftermarket intakes function, the stock intake features will be shown and discussed for further clarity.
This is the stock intake as viewed from the driver's side.
The "U" shaped assembly and the tank that connects to it on the left is commonly referred to as the snorkle, snorkus, silencer, or resonator. It is actually hidden in the fender.
This is the stock intake as viewed from the passenger's side.
This is the stock intake as viewed from above.
1. Stock "ram intake" funnel.
2. Stock air filter box.
3. MAF sensor.
4. MAF sensor piping.
What is a short ram? This is an aftermarket intake that removes the stock fenderwell snorkel components and draws air from the engine bay. To generalize, it is essentially a filter unit that replaces the stock air filter box. Some aftermarket short rams also replace some or all of the stock MAF piping with aftermarket piping.
What is a CAI? This is an aftermarket intake that removes the stock fenderwell snorkel components and replaces them with aftermarket piping. These systems, depending on the manufacturer, may or may not replace the MAF piping as well. These systems draw air from the fenderwell.
Which type of Subaru does this information apply to? This post is generally catered towards turbocharged models. Naturally aspired Subarus actually see good, solid, and safe gains from an aftermarket intake. The STi appears to accept some intakes without as many ill effects as the WRX and little data is known about other turbocharged Subaru models. The information about aftermarket filters' filtration capabilities is applicable to all vehicles though and is a point of consideration for some owners.
Is the stock WRX/STi system adequate? Yes. The majority of major Subaru tuners agree that the stock intake is adequate to power levels in the 400HP range. It also has the following advantages:
1. The standard air scoop is mounted high in the engine bay. This makes it resistant to ingress of water. The design of the fender snorkel helps to remove any water that is drawn in by this scoop.
2. Air drawn in is cool, since the air comes from the edge of the engine bay, and at speed, all air will be drawn from outside.
3. The standard system is quiet since the resonator in the fender helps filter out noise from the air flow.
4. The stock ECU is calibrated to work perfectly with the stock intake system.
Are there any downsides to aftermarket intakes? There are potential problems with some intake systems. Most manufacturers utilize less dense filtration media in their filters. This equates to increased pariculate matter injestion via the intake. This depends on the manufacturer's choice of filter media and is something to be taken into consideration. CAI can be suseptible to water injestion. This is because through their design the filter media is quite low in the fenderwell. Extreme caution should be used when driving through standing water or other areas where water is present. The major downside of intakes are problems with the air/fuel ratio.
Which intakes do not cause problems with the air/fuel ratio? The only manufacturers of intakes that claim in writing not to cause any ill effects are:
a. TurboXS
b. APS
c. Perrin (based on my personal email correspondance with Perrin)
d. K&N Typhoon (based on testing by nhluhr and testing by AaronWRX) These tests were performed on an STi and their effect on WRX A/F ratios is untested.
Do intakes cause problems with the air/fuel ratio? Many seem to believe that since their XXX intake does not cause a CEL or exhibit any driveability problems, then their XXX intake must be good. Though the apparent increase in power gives them peace of mind, what they don't take into account is their intake is actually causing unseen harm to their engine. This is generally due to two reasons:
1. The intake piping diameter is incorrect. This can cause a lean condition in the case of larger than stock diameter piping or a rich condition with decreased diameter piping.
2. The air flow is not laminar. The stock piping, through it's apparent unusual design, is constructed to smooth out turbulent air flow. Aftermarket systems do not take this into consideration. When turbulence occurs, the MAF sensor will suddenly see more or less air then it had previously. This will cause the ECU to respond by making the engine run leaner or richer for as long as the error from turbulence occurs.
Can the intake problems be corrected through aftermarket engine management? Yes. There are a wide variety of engine management systems that have the capability of modifying the mass air flow values to correct intake piping that is non-OEM size. Some intakes have especially troublesome turbulence problems. Since this turbulence can occur at different points in the power band, based on both engine RPM and engine load, all that can be done to make the engine run safely is to recalibrate the engine with a relatively rich overall tune to compensate.
Is there something I can do myself to free up my intake? Many owners remove their snorkel and utilize an aftermarket filter in the stock air box to free up the intake system somewhat. Instructions for this procedure can be found via this link, this link, and [rul=http://www.scoobymods.com/forums/showthread.php?s=&threadid=167]this link[/url].
Which manufacturer is best? This topic is highly debated. There have been no reported consistent "bad" intakes on the market. Obviously, there may have been bad intakes sold, but not enough to report as "bad" overall.
Which intakes have the best gains? There is no irrefutable evidence that any intake has better gains than another.
Where do I buy an intake? Every Subaru/Import performance store sells intakes. For purchasing, support your local economy or the I-CLUB Vendors.
How hard is it to install an intake? Allow around one hour for install time. Professional installation, depending on your area, is around $75. This is one vehicle modification that is very simple and can be successfully accomplished by even the greenest shade tree mechanic.
How do I install an intake? Refer to the intake manufacturer's instructions. Below are links to some of the better known intake installation instructions:
TurboXS's Instructions (with photos)
scoobymods.com instructions (with photos)
Should I reset my ECU after this mod? It is never a bad idea to perform an ECU reset after a mod. The traditional route is to disconnect the negative battery terminal, press the brake pedal for a few seconds to bleed the system of charge, and reattach. Some use the more advanced Vishnu Reset.
What about just using a drop in air filter like K&N etc.? Many people will install an aftermarket air filter with two lines of reasoning:
a. longer lifespan due to end user cleaning = cost savings
b. freer flowing = more HP
While both are probably true, there are costs associated with using an aftermarket drop in air filter.
a. Comparing costs of the OEM paper filter at $10 vs an aftermaket unit at $40 mean you will have to use the aftermarket unit for 150,000 miles before you see any return on your investment based on change frequency schedules.
b. freer flowing means more contaminants work their way into your engine. Filtration study
c. HP gains are not well documented if at all.
Editors Note
My thanks to Trey Cobb of Cobb Tuning for writing an excellent intake article and to EcuTek for their excellent intake article which both provided a lot of the information contained within this FAQ.
This post was created because I wasn't able to find a good intake FAQ. I came up with the text based on LOTS of searching here. It was also created to be intentionally brand neutral so that it serves as a stepping stone for further research. Upon reading this you should have an idea of what type of intake best suits your needs. The manufacturer is up to you.
If you find an error in this FAQ, please PM me with factual details and I will update this post. Responses such as, "I have XXX's intake and it's great!" or "XXX's intake is boggy" are not appreciated here, that is what the Car Parts Review Forum is for.
The primary purpose of an aftermarket intake is to increase the amount of air flow the engine receives.
HP gain is 0-15HP. These HP figures are a range as different intakes have different dyno results.
What is an aftermarket intake? Aftermarket intakes can be broken down into two types:
1. Short ram: AKA shorty or ram pod.
2. Cold air intake: AKA CAI.
What does the stock intake look like? To gain a perspective on how aftermarket intakes function, the stock intake features will be shown and discussed for further clarity.
This is the stock intake as viewed from the driver's side.
The "U" shaped assembly and the tank that connects to it on the left is commonly referred to as the snorkle, snorkus, silencer, or resonator. It is actually hidden in the fender.
This is the stock intake as viewed from the passenger's side.
This is the stock intake as viewed from above.
1. Stock "ram intake" funnel.
2. Stock air filter box.
3. MAF sensor.
4. MAF sensor piping.
What is a short ram? This is an aftermarket intake that removes the stock fenderwell snorkel components and draws air from the engine bay. To generalize, it is essentially a filter unit that replaces the stock air filter box. Some aftermarket short rams also replace some or all of the stock MAF piping with aftermarket piping.
What is a CAI? This is an aftermarket intake that removes the stock fenderwell snorkel components and replaces them with aftermarket piping. These systems, depending on the manufacturer, may or may not replace the MAF piping as well. These systems draw air from the fenderwell.
Which type of Subaru does this information apply to? This post is generally catered towards turbocharged models. Naturally aspired Subarus actually see good, solid, and safe gains from an aftermarket intake. The STi appears to accept some intakes without as many ill effects as the WRX and little data is known about other turbocharged Subaru models. The information about aftermarket filters' filtration capabilities is applicable to all vehicles though and is a point of consideration for some owners.
Is the stock WRX/STi system adequate? Yes. The majority of major Subaru tuners agree that the stock intake is adequate to power levels in the 400HP range. It also has the following advantages:
1. The standard air scoop is mounted high in the engine bay. This makes it resistant to ingress of water. The design of the fender snorkel helps to remove any water that is drawn in by this scoop.
2. Air drawn in is cool, since the air comes from the edge of the engine bay, and at speed, all air will be drawn from outside.
3. The standard system is quiet since the resonator in the fender helps filter out noise from the air flow.
4. The stock ECU is calibrated to work perfectly with the stock intake system.
Are there any downsides to aftermarket intakes? There are potential problems with some intake systems. Most manufacturers utilize less dense filtration media in their filters. This equates to increased pariculate matter injestion via the intake. This depends on the manufacturer's choice of filter media and is something to be taken into consideration. CAI can be suseptible to water injestion. This is because through their design the filter media is quite low in the fenderwell. Extreme caution should be used when driving through standing water or other areas where water is present. The major downside of intakes are problems with the air/fuel ratio.
Which intakes do not cause problems with the air/fuel ratio? The only manufacturers of intakes that claim in writing not to cause any ill effects are:
a. TurboXS
b. APS
c. Perrin (based on my personal email correspondance with Perrin)
d. K&N Typhoon (based on testing by nhluhr and testing by AaronWRX) These tests were performed on an STi and their effect on WRX A/F ratios is untested.
Do intakes cause problems with the air/fuel ratio? Many seem to believe that since their XXX intake does not cause a CEL or exhibit any driveability problems, then their XXX intake must be good. Though the apparent increase in power gives them peace of mind, what they don't take into account is their intake is actually causing unseen harm to their engine. This is generally due to two reasons:
1. The intake piping diameter is incorrect. This can cause a lean condition in the case of larger than stock diameter piping or a rich condition with decreased diameter piping.
2. The air flow is not laminar. The stock piping, through it's apparent unusual design, is constructed to smooth out turbulent air flow. Aftermarket systems do not take this into consideration. When turbulence occurs, the MAF sensor will suddenly see more or less air then it had previously. This will cause the ECU to respond by making the engine run leaner or richer for as long as the error from turbulence occurs.
Can the intake problems be corrected through aftermarket engine management? Yes. There are a wide variety of engine management systems that have the capability of modifying the mass air flow values to correct intake piping that is non-OEM size. Some intakes have especially troublesome turbulence problems. Since this turbulence can occur at different points in the power band, based on both engine RPM and engine load, all that can be done to make the engine run safely is to recalibrate the engine with a relatively rich overall tune to compensate.
Is there something I can do myself to free up my intake? Many owners remove their snorkel and utilize an aftermarket filter in the stock air box to free up the intake system somewhat. Instructions for this procedure can be found via this link, this link, and [rul=http://www.scoobymods.com/forums/showthread.php?s=&threadid=167]this link[/url].
Which manufacturer is best? This topic is highly debated. There have been no reported consistent "bad" intakes on the market. Obviously, there may have been bad intakes sold, but not enough to report as "bad" overall.
Which intakes have the best gains? There is no irrefutable evidence that any intake has better gains than another.
Where do I buy an intake? Every Subaru/Import performance store sells intakes. For purchasing, support your local economy or the I-CLUB Vendors.
How hard is it to install an intake? Allow around one hour for install time. Professional installation, depending on your area, is around $75. This is one vehicle modification that is very simple and can be successfully accomplished by even the greenest shade tree mechanic.
How do I install an intake? Refer to the intake manufacturer's instructions. Below are links to some of the better known intake installation instructions:
TurboXS's Instructions (with photos)
scoobymods.com instructions (with photos)
Should I reset my ECU after this mod? It is never a bad idea to perform an ECU reset after a mod. The traditional route is to disconnect the negative battery terminal, press the brake pedal for a few seconds to bleed the system of charge, and reattach. Some use the more advanced Vishnu Reset.
What about just using a drop in air filter like K&N etc.? Many people will install an aftermarket air filter with two lines of reasoning:
a. longer lifespan due to end user cleaning = cost savings
b. freer flowing = more HP
While both are probably true, there are costs associated with using an aftermarket drop in air filter.
a. Comparing costs of the OEM paper filter at $10 vs an aftermaket unit at $40 mean you will have to use the aftermarket unit for 150,000 miles before you see any return on your investment based on change frequency schedules.
b. freer flowing means more contaminants work their way into your engine. Filtration study
c. HP gains are not well documented if at all.
Editors Note
My thanks to Trey Cobb of Cobb Tuning for writing an excellent intake article and to EcuTek for their excellent intake article which both provided a lot of the information contained within this FAQ.
This post was created because I wasn't able to find a good intake FAQ. I came up with the text based on LOTS of searching here. It was also created to be intentionally brand neutral so that it serves as a stepping stone for further research. Upon reading this you should have an idea of what type of intake best suits your needs. The manufacturer is up to you.
If you find an error in this FAQ, please PM me with factual details and I will update this post. Responses such as, "I have XXX's intake and it's great!" or "XXX's intake is boggy" are not appreciated here, that is what the Car Parts Review Forum is for.
Last edited by kenji815; 01-09-2006 at 02:31 PM.
01-09-2006, 02:30 PM
#19
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Originally Posted by sigma pi
Where do I buy aftermarket BOVs/BPVs? Every Subaru/Import performance store sells BOVs. For purchasing, support your local economy or the I-CLUB Vendors.
read before you post there eddie you just coppied and pasted
you interent tuner hehe
read before you post there eddie you just coppied and pasted
you interent tuner hehe
01-09-2006, 07:00 PM
#20
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Thread Starter
Join Date: Nov 2005
Location: So Cal
Posts: 85
Car Info: 2005 WRB w/ Silver Rims
so i still dont get it.. the injen cai claims to be perfectly tuned for the ecu.. just like the typhoon, aps, and all the others.. so do i lose power? stay the same?
01-09-2006, 07:09 PM
#21
VIP Member
Originally Posted by FujiApples
so i still dont get it.. the injen cai claims to be perfectly tuned for the ecu.. just like the typhoon, aps, and all the others.. so do i lose power? stay the same?
my gawd! stop it already
If you put an intake on you will hear noise. The factory ECU can adjust the fuel since its reading more air.
01-09-2006, 09:04 PM
#22
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Thread Starter
Join Date: Nov 2005
Location: So Cal
Posts: 85
Car Info: 2005 WRB w/ Silver Rims
haha sorry.. its just that everything everyone is saying is different.. some say its good some say its bad... and so all the opinions are getting at that its not really bad.. but eddie said it was.. and he was the first person i talked to about this and it was like some small conversation that turned into this big "cai make u lose power" issue 
01-09-2006, 11:11 PM
#23
it sure made my car run crappier
the opening where the maf sensor is, is bigger so more unmetered air is going in making it lean out. which make more HP. the computer soon learns whats going on by teh A/F ratio sensor and adjusts it back to stock. but its constantly fighting the bad info from the MAF
the opening where the maf sensor is, is bigger so more unmetered air is going in making it lean out. which make more HP. the computer soon learns whats going on by teh A/F ratio sensor and adjusts it back to stock. but its constantly fighting the bad info from the MAF
01-10-2006, 03:54 PM
#24
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OMG i have a headache. Please read the FAQ i posted on top..
Originally Posted by Kenji815
Do intakes cause problems with the air/fuel ratio? Many seem to believe that since their XXX intake does not cause a CEL or exhibit any driveability problems, then their XXX intake must be good. Though the apparent increase in power gives them peace of mind, what they don't take into account is their intake is actually causing unseen harm to their engine. This is generally due to two reasons:
1. The intake piping diameter is incorrect. This can cause a lean condition in the case of larger than stock diameter piping or a rich condition with decreased diameter piping.
2. The air flow is not laminar. The stock piping, through it's apparent unusual design, is constructed to smooth out turbulent air flow. Aftermarket systems do not take this into consideration. When turbulence occurs, the MAF sensor will suddenly see more or less air then it had previously. This will cause the ECU to respond by making the engine run leaner or richer for as long as the error from turbulence occurs.
1. The intake piping diameter is incorrect. This can cause a lean condition in the case of larger than stock diameter piping or a rich condition with decreased diameter piping.
2. The air flow is not laminar. The stock piping, through it's apparent unusual design, is constructed to smooth out turbulent air flow. Aftermarket systems do not take this into consideration. When turbulence occurs, the MAF sensor will suddenly see more or less air then it had previously. This will cause the ECU to respond by making the engine run leaner or richer for as long as the error from turbulence occurs.
Last edited by kenji815; 01-10-2006 at 03:56 PM.
01-10-2006, 03:54 PM
#25
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Join Date: Nov 2005
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sorry for sounding noob but like.. would a bov sorta even it out? cuz it makes it a bit rich right after u get back on the accelerater (this ones for sigma pi)
01-10-2006, 04:07 PM
#26
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Originally Posted by sigma pi
Where do I buy aftermarket BOVs/BPVs? Every Subaru/Import performance store sells BOVs. For purchasing, support your local economy or the NASIOC Vendors.
read before you post there eddie you just coppied and pasted
you interent tuner hehe
read before you post there eddie you just coppied and pasted
you interent tuner hehe
01-10-2006, 05:34 PM
#27
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Join Date: Sep 2004
Location: Virginia
Posts: 131
Car Info: 02' WRX
Originally Posted by LifePlaza
what makes you think eddie knows what he's talking about?
This is from a PROFESSIONAL SUBARU RACER :
GarySheehan
SMR Driver Extraordinaire & Team Manager
Member # 2019
posted 20 March, 2004 04:25 PM
--------------------------------------------------------------------------------
Here's the deal. With the recirculating blow off valve, when the throttle plate is closed, pressurized air is sent into the intake post MAF. This volume of air goes back through the compressor of the turbo, since it is still spinning very fast, back into the intercooler. At the same time, airflow through the MAF has virtually stopped since there is pressurized air coming from the blow-off valve. Also, everyone is fogetting that the engine is still consuming air at a reasonably fast pace, even though the throttle is closed. The small volume of pressurized air in the intercooler will be relieved in a relatively short time even with a closed throttle. Very little air, if any, should be force back past the MAF since the engine is still consuming air.
With a partial or full atmospheric venting BOV, the air that the MAF has accounted for is gone. The airflow through the MAF does not slow down since all the pressurized air has been vented to atmosphere, but the engine is still consuming air. Therefore, when you go back to on-throttle, the MAF has told the ECU that there is more air in the system than there actually is. The ECU signals the injectors for the appropriate amount of fuel for the air that the MAF has accounted for (which just went out your BOV). Hence the momentary rich condition. It only stays rich for as long as it would take the engine to consume the incorrect volume of air.
We used a 100% BOV at a few of our races. Where it's very noticeable is mid-corner partial throttle. The driver is modulating the gas pedal going into boost and coming back out, in quick succession. During this time the engine is going through mutliple cycles of rich condition. Throttle response suffers, there are momentary hiccups in power delivery after throttle application and the driveability of the engine is not optimal. This happened with two different makes of atmospheric BOVs.
We went back to the stock BOV and partial throttle driveability went back to being perfect.
It's too bad, because I really enjoyed the sound of the BOV on the track. But then again, when racing, you can't sacrifice performance for asthetics.
Gary
Sheehan Motor Racing
www.teamSMR.com
--------------------------------------------------------------------------------
Atmospheric BOV's will make your car run less than optimal.The air that is diverted to the atmoshere was ALREADY MEETERED FROM THE MAF and the ECU is expecting to be there after the shift and you push back on the throttle.Also by venting to atmosphere you de-pressurize the charge pipes.Before you can make positive pressure again(boost) the pipes have to be pressurized again meaning you will now have TURBO LAG.By recirculating back into the system you will also keep the tubo spinning in its no-load condition durring shifting with a "pin wheel" like effect which also helps on throttle responce to keep TURBO LAG from occuring by keeping the turbo spining
Last edited by Donkey; 01-10-2006 at 05:39 PM.
01-10-2006, 05:36 PM
#28
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Join Date: Sep 2004
Location: Virginia
Posts: 131
Car Info: 02' WRX
Originally Posted by LifePlaza
an CAI or BOV will not cause lag.
A BOV to 100%atmosphere is just wasted air
A BOV to 100%atmosphere is just wasted air
Last edited by Donkey; 01-10-2006 at 05:41 PM.
01-10-2006, 06:04 PM
#30
Originally Posted by FujiApples
sorry for sounding noob but like.. would a bov sorta even it out? cuz it makes it a bit rich right after u get back on the accelerater (this ones for sigma pi)
it would not equil each other out