Stock Boost PSI

[msharifi]

Hi all,

I'm trying to figure out my bad MPG and very bad performance on my car and I bought a boost gauge and the reading I get is 10psi and then drops to 7psi.

What is the spec on the Stock Turbo boost PSI and the vaccume line reading?

What area's do I need to look for boost leak?

[A4natomical]

sounds bout right. vacuum at ~18-20mmhg

[[email protected]]

9psi and -22mmHg

[A4natomical]

oh dang, i didnt know stock was like that. wow.

[A4 Moda]

Could be your forward o2 sensor has gone bad. Got any codes for it yet?

Try some sea foam as well. Check plugs. And clean your air filter. That's about it man.

How many miles on the clock?

[msharifi]

Could be your forward o2 sensor has gone bad. Got any codes for it yet?

Try some sea foam as well. Check plugs. And clean your air filter. That's about it man.

How many miles on the clock?

I changed the first o2 Sensfor the one before the CAT did not have a CEL but I heard it can get lazy.

What is sea foam? new spark plugs and I have a cold air intake but it was like this when I had the stock.

I have 65k miles on the car.

here is another question when I turn the car in the morning there is a loud sound coming from the turbo area and some users told me that my secondary air pump is going out. so this morning I turn the car on and went by the secondary air pump hose that has a breather hose and I took the mini filter out and put my hand it does suck air. When I try to clog the hose the sound went away but when I took my hand off the sound came back. It seems like the sound is coming from the breather hose that connectes to the secondary air pump. does that effect your MPG? I heard its only at cold start to heat your CAT.

Sorry for the long writing. I live in OC and maybe someone can help me.

[msharifi]

Could be your forward o2 sensor has gone bad. Got any codes for it yet?

Try some sea foam as well. Check plugs. And clean your air filter. That's about it man.

How many miles on the clock?

I had this code before and I cleared it haven't seen it come back or maybe it did have not checked it.

17522 - Oxygen (Lambda) Sensor: B1 S2: Internal Resistance too High
P1114 - 008 - Implausible Signal - Intermittent

would that cause the secondary air pump to start making loud noise?

[A4ringedONE8T]

Yes the SAI pump runs only at cold startup to aid in heating up the cat and quickly getting the car to emissions friendly temps. How you can tell if the SAI system is active is by the RPM's, when the pump is running the RPM's will be around 11-1200, when it turns off, they will drop to there normal 8-900. SAI shouldnt affect you economy and it will make a suction/air movement noise when its running, can you be more specific on the sound its making?

[msharifi]

I will try to video tape the sound and send a link. The sound does go away after a minute some say its my secondary air pump is going bad but I want to make sure that is really the case.

[msharifi]

anyone in OC have a spare DV I can swap to see if my DV is really bad?

[old guy]

OK. Let me try one more time to help you. Quite frankly you have been all over the map with your previous posts so it has been difficult to follow your exact symptoms. first lets address the noise. If it is ONLY occurring for the first 90 seconds or so during a cold start the noise is definitely coming somewhere from the SAI system. This only works during a cold start and will have NO effect on your overall gas mileage. The SAI pump is powered by the serpentine belt on the front of the motor. The air flow goes from the pump through a hard line on the turbo side of the motor to the Combi valve that I sent you a picture of previously. the Combi valve is opened and closed via a vacuum line (the blue line in the previous pic I posted for you). The vacuum line is controlled by the SAI air valve (N-112) located under the intake manifold. This diagram should help Clicky click All of this is controlled by the ECU. It engages the SAI pump and allows the air flow to enter the exhaust through the combi valve on the back of the head. You already know that your pump is working. If there is any break in the lines from the SAI pump to the hard line or from the hard line to the Combi valve you will get noise. Also, if the vacuum line is broken the the combi valve will not work properly. You need to check all of that out for any problems. Usually the issue is a split hose connecting the SAI to the hard line. Or it can be the pump itself making the noise. Again, to reiterate, none of this will cause a performance issue. Just a noisy start up.

Now to your boost questions. If you are running a stock ECU your boost will peak around 10 or 11psi and taper off to around 6 or 7psi. Perfectly normal.

As to the bad gas mileage and poor performance. what are you considering bad mileage? Can you give a better description of the performance drop? The front O2 sensor will affect your gas mileage. You mentioned that you replaced it. Did you use an OEM part or an aftermarket part? What makes you think your DV is bad? Are you hearing a "whoosh" sound when accelerating? Any additional info you can give will be helpful in determining your performance and mileage issues.

[A4 Moda]

Oh and just FYI,
Your CAI is probably also causing bad MPG.

I found that out when I put one on my car as well. Mostly it' becuase you are sucking in hot, less dense, air. That's why I just tossed it and went back to my stock air box. I put in a foam filter (universal from tru Flow). Not only did that improve my fuel economy, it helped recover some lost HP as well.

[msharifi]

OK. Let me try one more time to help you. Quite frankly you have been all over the map with your previous posts so it has been difficult to follow your exact symptoms. first lets address the noise. If it is ONLY occurring for the first 90 seconds or so during a cold start the noise is definitely coming somewhere from the SAI system. This only works during a cold start and will have NO effect on your overall gas mileage. The SAI pump is powered by the serpentine belt on the front of the motor. The air flow goes from the pump through a hard line on the turbo side of the motor to the Combi valve that I sent you a picture of previously. the Combi valve is opened and closed via a vacuum line (the blue line in the previous pic I posted for you). The vacuum line is controlled by the SAI air valve (N-112) located under the intake manifold. This diagram should help Clicky click All of this is controlled by the ECU. It engages the SAI pump and allows the air flow to enter the exhaust through the combi valve on the back of the head. You already know that your pump is working. If there is any break in the lines from the SAI pump to the hard line or from the hard line to the Combi valve you will get noise. Also, if the vacuum line is broken the the combi valve will not work properly. You need to check all of that out for any problems. Usually the issue is a split hose connecting the SAI to the hard line. Or it can be the pump itself making the noise. Again, to reiterate, none of this will cause a performance issue. Just a noisy start up.

Now to your boost questions. If you are running a stock ECU your boost will peak around 10 or 11psi and taper off to around 6 or 7psi. Perfectly normal.

As to the bad gas mileage and poor performance. what are you considering bad mileage? Can you give a better description of the performance drop? The front O2 sensor will affect your gas mileage. You mentioned that you replaced it. Did you use an OEM part or an aftermarket part? What makes you think your DV is bad? Are you hearing a "whoosh" sound when accelerating? Any additional info you can give will be helpful in determining your performance and mileage issues.

Thanks for the info

1. If my SAI pump is working why is there a loud sound coming? is this normal? because it wasn't like this before.

2. "If there is any break in the lines from the SAI pump to the hard line or from the hard line to the Combi valve you will get noise" How do I check that by just inspecting it?

3. When I say I have bad MPG... New spark plugs, Oil change, clean air filter, New before CAT o2 sensor, tires are 32PSI all around. Everything is stock but I have a aftermarket cold air intake but the problem was there with the stock intake. The whoosh sound is loud for a stock DV and I heard that bad DV will have leak vaccume etc. I do log my MPGs from full tank and with the new o2 sensor I get about 15 MPG.

I dont know where to go for the problem. Thanks for the help.

[msharifi]

Oh and just FYI,
Your CAI is probably also causing bad MPG.

I found that out when I put one on my car as well. Mostly it' becuase you are sucking in hot, less dense, air. That's why I just tossed it and went back to my stock air box. I put in a foam filter (universal from tru Flow). Not only did that improve my fuel economy, it helped recover some lost HP as well.

I have a heat sheild for it and I had the same mpg with the stock.

[old guy]

Thanks for the info

1. If my SAI pump is working why is there a loud sound coming? is this normal? because it wasn't like this before.

If it wasn't like that before you need to check out the air lines from the SAI to the combi valve for any leaks.

2. "If there is any break in the lines from the SAI pump to the hard line or from the hard line to the Combi valve you will get noise" How do I check that by just inspecting it?

Yes. Just examine the complete system. If everything is intact the problem may just be the pump going out.

3. When I say I have bad MPG... New spark plugs, Oil change, clean air filter, New before CAT o2 sensor, tires are 32PSI all around. Everything is stock but I have a aftermarket cold air intake but the problem was there with the stock intake. The whoosh sound is loud for a stock DV and I heard that bad DV will have leak vaccume etc. I do log my MPGs from full tank and with the new o2 sensor I get about 15 MPG.

What was the mileage before you replaced the O2 sensor? You stated that the "whoosh" sound was loud. Are you getting the sound under acceleration or only when you let off the gas? The aftermarket intake will definitely make the DV louder when you let off the gas. It is barely audible with a stock intake. Is there a noticeable decrease in acceleration associated with the drop in mileage?

[old guy]

Another thought occurred to me concerning the SAI noise. Did it get loud when you replaced the intake with an aftermarket unit? The SAI normally routes through the stock intake box. The stock box is lined with sound absorbing material to dampen the intake, DV and SAI noise. What you are hearing may be normal noises usually dampened by the stock air box.

[A4 Moda]

You might have a boost leak then. The loud sound you might be hearing may be boost venting to the atmosphere.

Check the L hose at the back of the block. That one usually bursts just because it's happy.

Glad OldGuy is helping you out too.
GL

I have a heat sheild for it and I had the same mpg with the stock.

[msharifi]

If it wasn't like that before you need to check out the air lines from the SAI to the combi valve for any leaks. Yes. Just examine the complete system. If everything is intact the problem may just be the pump going out.
What was the mileage before you replaced the O2 sensor? You stated that the "whoosh" sound was loud. Are you getting the sound under acceleration or only when you let off the gas? The aftermarket intake will definitely make the DV louder when you let off the gas. It is barely audible with a stock intake. Is there a noticeable decrease in acceleration associated with the drop in mileage?

I changed it week ago it has 65k miles. only when I let off the gas it makes the woosh sound loud.

[msharifi]

Another thought occurred to me concerning the SAI noise. Did it get loud when you replaced the intake with an aftermarket unit? The SAI normally routes through the stock intake box. The stock box is lined with sound absorbing material to dampen the intake, DV and SAI noise. What you are hearing may be normal noises usually dampened by the stock air box.

I thought about this today and I'm going to swap the intake with oem air box and see if it goes away.

[old guy]

I changed it week ago it has 65k miles. only when I let off the gas it makes the woosh sound loud.

OK. That is normal.

[msharifi]

I did the boost leak test and I found a leak coming from the Vacuum Pump Check Valve, Purge.

http://www.mjmautohaus.com/catalog/p...oducts_id=2786