Low boost , bleeding boost pressure?
08-05-08, 10:28 PM
#1
Low boost , bleeding boost pressure?
I'm helping a friend of mine get his FD back in shape, the current problem is that its really low on boost. We installed a boost gauge and he claimed it produced ZERO boost when he tested it. Turned out the gauge was bad, so we replaced it and he still said it only makes 1-2 psi.
I drove it and found that if roll onto the throttle slowly, it can climb to about 5 psi before the boost bleeds all the way down to zero. Right before the boost begins to fall, there is a steadily increasing "wooosh" that like air is escaping from somewhere.
However, if you stomp on the throttle, it will only boost to 1 psi or so before it bleeds off. (the "woosh" sound occurs almost instantly in this case)
He recently replaced the stock air box w/ two cone filters and aluminum pipes, capping any unused nipples/pipes. In the process, he removed the BOV attatched to the front turbo, and left the second BOV venting to atmosphere.
My Theory:
I think there were 2 BOV's for a reason (namely they can't handle much more than 5psi a piece) and the one remaining BOV can handle the boost as it gradually builds to its "5psi" limit. However if it suddenly gets hit w/ lets say 7psi it instantly opens up and bleeds off all the boost pressure.
Let me know what you guys thing
I drove it and found that if roll onto the throttle slowly, it can climb to about 5 psi before the boost bleeds all the way down to zero. Right before the boost begins to fall, there is a steadily increasing "wooosh" that like air is escaping from somewhere.
However, if you stomp on the throttle, it will only boost to 1 psi or so before it bleeds off. (the "woosh" sound occurs almost instantly in this case)
He recently replaced the stock air box w/ two cone filters and aluminum pipes, capping any unused nipples/pipes. In the process, he removed the BOV attatched to the front turbo, and left the second BOV venting to atmosphere.
My Theory:
I think there were 2 BOV's for a reason (namely they can't handle much more than 5psi a piece) and the one remaining BOV can handle the boost as it gradually builds to its "5psi" limit. However if it suddenly gets hit w/ lets say 7psi it instantly opens up and bleeds off all the boost pressure.
Let me know what you guys thing
08-05-08, 11:26 PM
#2
Rotary Freak
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i dont think that there are two bov's, it sounds like the first "bov" you are talking about might be the charge relief valve that lets out air when prespooling the secondary turbo(i believe). try rehooking up the stock bov and see if that helps at all. make sure all other vacuum lines are connected.
also did he have this problem before removing the stock intake?
also did he have this problem before removing the stock intake?
08-05-08, 11:42 PM
#3
Oh, well he told me it was a second BOV, (he took them off and left them at home, so I haven't seen the stock pieces)
Well, the only valve in the system currently is the one closest to the firewall, (I believe its the stock BOV) and its vented to atmosphere.
He hasn't touched any of the vaccumm lines (not associated w/ the stock airbox) and No this problem did not exist before removing the stock intake.
Well, the only valve in the system currently is the one closest to the firewall, (I believe its the stock BOV) and its vented to atmosphere.
He hasn't touched any of the vaccumm lines (not associated w/ the stock airbox) and No this problem did not exist before removing the stock intake.
08-06-08, 12:00 AM
#4
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if the problem did not exist before changing the intake, then i would say something must not have been hooked back up correctly. i still think that he probably removed the actual stock bov thinking that the charge relief valve(which looks very similar) was the bov. i think it is a must for proper operation to have both hooked up correctly. before i ran the car under boost anymore i would hook the bov back up the way it was and just vent it to the engine bay and see if that helps.
08-06-08, 01:39 AM
#5
yea, I told him he needed both valves hooked up, he's having all the stock pieces mailed to him.
I know there's a boost pattern (or at least there's supposed to be) for FD's what is it? (FC guy here) Also, could it be a problem w/ an rpm activated solenoid or switch? or is everything psi activated? I ask because his tach doesn't work so....... yea
I know there's a boost pattern (or at least there's supposed to be) for FD's what is it? (FC guy here) Also, could it be a problem w/ an rpm activated solenoid or switch? or is everything psi activated? I ask because his tach doesn't work so....... yea
08-06-08, 10:47 AM
#7
Well after deliberating with the mad scientist it seems there is def a boost leak. He obtained a secondary blow off valve from another blown car and has the settings back to stock minus a few hoses and it seems the car is still running to 5 pounds and expelling boost...
to be continued...
to be continued...
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08-06-08, 10:14 PM
#8
Alright... so we made a pressure tester (and a damn good one if I may say so). We took the system up to about 10 lbs and the pressure just steadily bled off.
We then sprayed soapy water on the various parts of the intake tract and voila!
Apparently he removed the TB elbow to change the spark plugs and didn't secure it properly when he put it back on because it was blowing bubbles like there's no tomorrow.
The bolts were tight, and there doesn't appear to be a real gasket there, so we used some RTV to seal it up, we'll test it in the morning.
We then sprayed soapy water on the various parts of the intake tract and voila!
Apparently he removed the TB elbow to change the spark plugs and didn't secure it properly when he put it back on because it was blowing bubbles like there's no tomorrow.
The bolts were tight, and there doesn't appear to be a real gasket there, so we used some RTV to seal it up, we'll test it in the morning.
08-08-08, 01:37 PM
#10
Lol, +1
....anyways, after sealing the leak, the boost leak continued, although boost seems to build a little bit faster, it still "wooshes" away just as quickly.
We then re-pressure tested and discovered that the rear most brown valve (bov?) was bleeding off boost pressure (the rtv sealed area is fine). He then came up w/ the idea of routing the open nipple from the BOV to the front nipple on the Y-pipe (where another brown valve originally was).
I was skeptical to say the least, but the car will now hold 7-8 pounds and pulls a lot harder (read: at all ...lol)
My question is, is routing the valve like that doing any damage? hurting performance?
....anyways, after sealing the leak, the boost leak continued, although boost seems to build a little bit faster, it still "wooshes" away just as quickly.
We then re-pressure tested and discovered that the rear most brown valve (bov?) was bleeding off boost pressure (the rtv sealed area is fine). He then came up w/ the idea of routing the open nipple from the BOV to the front nipple on the Y-pipe (where another brown valve originally was).
I was skeptical to say the least, but the car will now hold 7-8 pounds and pulls a lot harder (read: at all ...lol)
My question is, is routing the valve like that doing any damage? hurting performance?
08-08-08, 05:53 PM
#11
Not a step in the right direction.
The large nipple on the y-pipe is for the stock BOV. What's there now?
You should route the other brown valve (coming from the rear section of the y-pipe) back to the air intake where it was. It's called the charge relief valve and it should in fact be open from about 3000 to 4500rpm as part of the prespool process.
Have a look at the sticky thread listed manuals and tech info. Print the color vacuum hose diagram and go through the car until you're sure they're all correct.
Dave
The large nipple on the y-pipe is for the stock BOV. What's there now?
You should route the other brown valve (coming from the rear section of the y-pipe) back to the air intake where it was. It's called the charge relief valve and it should in fact be open from about 3000 to 4500rpm as part of the prespool process.
Have a look at the sticky thread listed manuals and tech info. Print the color vacuum hose diagram and go through the car until you're sure they're all correct.
Dave
08-08-08, 06:17 PM
#12
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Having said all that, I was posting in another recent thread about just that, to see if it was normal lol. not many people seemed to know :P but I'm pretty certain it's normal, as I only head the noise after fitting the new filters! I'd still kinda like to know myself!!
Don't know if you've checked all the various rubber hoses, to/from intercooler, y pipe coupler, primary turbo inlet! My y pipe coupler was split right open where the jubilee clip fits. noticed the difference like night and day after that was fixed!
Anyway I'll stop rambling... I'm pretty new to all this myself anyway so what do I know... :P
08-09-08, 09:18 AM
#13
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I'm posting this video link up in a few threads, it relates to a few different things! Low quality but the best I could do... you can hear the wooshing!! this is the 3k startup procedure...
http://www.youtube.com/watch?v=IOn8xBHb0Zw
http://www.youtube.com/watch?v=IOn8xBHb0Zw
08-09-08, 10:35 AM
#14
Hey guys, I´m not really sure if this is the reason. Just for you to think about and take a look.
I don´t exactely know if the facts are right for the HKS SSQV BOV (as in the video!) because they work slightly different as the Blitz ones do, but for most BOVs this is important.
BOVs open by vacuum. So it is not only forced to open when you let off the gas AFTER you had built up boost pressure which is then wshhhhhhing away. It opens every time underpressure (vacuum) is applied to the vacuum hose of the valve. So at idle maybe the valve is leaking!
Normally they don´t open when no boost is applied, but it can!
So Blitz f.e. writes:
*The vacuum port must be located behind the throttle body. Make sure that the vacuum port receives both boost and vacuum pressure.
*Since different engines have different vacuum and boost pressures, set the Blitz blow off valve so that there is no air leak under idle.
Maybe your BOV is connected to the wrong hose, so your BOV is leaking at idle.
Maybe this helps!
Greetings Marc
PS: and please besure that you attached the BOV correct and you don´t replace the charge relief valve with your BOV!!
I don´t exactely know if the facts are right for the HKS SSQV BOV (as in the video!) because they work slightly different as the Blitz ones do, but for most BOVs this is important.
BOVs open by vacuum. So it is not only forced to open when you let off the gas AFTER you had built up boost pressure which is then wshhhhhhing away. It opens every time underpressure (vacuum) is applied to the vacuum hose of the valve. So at idle maybe the valve is leaking!
Normally they don´t open when no boost is applied, but it can!
So Blitz f.e. writes:
*The vacuum port must be located behind the throttle body. Make sure that the vacuum port receives both boost and vacuum pressure.
*Since different engines have different vacuum and boost pressures, set the Blitz blow off valve so that there is no air leak under idle.
Maybe your BOV is connected to the wrong hose, so your BOV is leaking at idle.
Maybe this helps!
Greetings Marc
PS: and please besure that you attached the BOV correct and you don´t replace the charge relief valve with your BOV!!
08-09-08, 10:51 AM
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Just to make extra sure, the hks bov should replace the valve closer to the front of the car shouldnt it? Does it look like it's in the right place in the vid? lol. I've just plumbed it straight into the standard location, with the standard hose... and again, vacuum hose is the standard hose...
08-09-08, 03:45 PM
#16
dgeesaman:
The large nipple on the Y pipe currently has a tube on it which is connected to the output nipple of the second (closer to the firewall) brown valve (bov).
He did that because while pressure testing the system we found that the brown valve closest to the firewall (bov) was bleeding off pressure. Is it supposed to? and if so, even if it were routed back to the intake, wouldn't that still count as a boost leak since the intake is pre-turbo?
If it were up to me, I'd put the stock airbox on an be done w/ it, or buy a proper intake system (like an A'pexi) that has nipples on it for proper hose routing. Be he seems hell bent on fashioning a working system out of this home made aluminum tube intake he built
moneyj51:
Thank you for the video. That is not the wooosssssshhhh sound that we were experiencing however. The sound was very close to the passenger side firewall and we have determined that it was coming from the BOV bleeding off pressure.
The large nipple on the Y pipe currently has a tube on it which is connected to the output nipple of the second (closer to the firewall) brown valve (bov).
He did that because while pressure testing the system we found that the brown valve closest to the firewall (bov) was bleeding off pressure. Is it supposed to? and if so, even if it were routed back to the intake, wouldn't that still count as a boost leak since the intake is pre-turbo?
If it were up to me, I'd put the stock airbox on an be done w/ it, or buy a proper intake system (like an A'pexi) that has nipples on it for proper hose routing. Be he seems hell bent on fashioning a working system out of this home made aluminum tube intake he built
moneyj51:
Thank you for the video. That is not the wooosssssshhhh sound that we were experiencing however. The sound was very close to the passenger side firewall and we have determined that it was coming from the BOV bleeding off pressure.
08-10-08, 06:30 AM
#17
The brown valve that connects at the fork in the y-pipe is the stock BOV. It's doesn't matter much where it vents to, so long as the rest of it is plumbed correctly. It should not vent anything under boost. It should only open when you let off throttle.
The brown valve that connects to the rear section of y-pipe is a relief valve that will dump air when the secondary is spooling boost. This is around 3300-4500rpm and when the primary is boosting. This is again normal.
Dave
The brown valve that connects to the rear section of y-pipe is a relief valve that will dump air when the secondary is spooling boost. This is around 3300-4500rpm and when the primary is boosting. This is again normal.
Dave
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