turbo noise
03-25-2002, 02:31 PM
#1
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turbo noise
The weather was finally good enough for me to go out and drive my Z. I did a ton of mods to it this winter and one of them was a new intercooler (shown in my profile). Now, whenever I give it more than 3/4 throttle and let off to shift, I hear a funny noise that sounds like moving air causing something to flap back and forth fairly fast. It didn't do this before I put the intercooler on and only does it with the intercooler installed. I know this because I disconnected it to see if it was causing the noise. Let me know if any of you guys have heard of this before.
-jeremy-
-jeremy-
03-25-2002, 03:19 PM
#2
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Location: San Diego
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Re: turbo noise
Is it like a fluttering noise? Do you have a compressor bypass valve installed that's plumbed back into the intake? A bypass valve would make that noise, and if you don't have either a bypass or bov installed, then the noise you're hearing is compressor surge. You probably didn't hear it before (assuming the intake pipe to the turbo was still the stock rubber) because the rubber insulated the noise, but since you have an intercooler and metal piping (again assumed), the metal amplifies the sound (kinda like intakes on n/a cars like hondas). I could hear the fluttering on my car when I had a cone filter installed and put my ear next to it, but now that I gotta bov, I don't hear it at all. Hope this helps.
82ZXT
82ZXT
03-26-2002, 09:31 PM
#3
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Re: turbo noise
Hi Zguy36----if you read the post just before this post he is right on to your problem-------------From your pictures I discovered that for one you removed the stock/factory blow-off valve------------this is part of your sound------------the other as the other poster described comes from your piping---------the factory used their blow-off valve to maintain a maximum boost level for longevity of the engine--------which you have now created obsolete-----------the factory also used a short pipe between the turbo and the intake coated in a sound deading material----------------as you stated the stated the sound is concurrent to the new intercooler and piping----------To start off you need some sort off Pop-off valve/Compressor valve/Blow-off-Valve(they go by numerous names)-----this valve releases the boost/pressuse that is built when either you shift or the tranny shifts for you to help maintain/ contain maximum boost levels-----------this is what is more than likely causing your "FLAPPING" sound in your Air Flow Meter------without this or any other similiar device you are cuasing a cascading event of boost----------"you must release boost to create boost"-------It may be easier to describe back-pressure-----or maybe even a "BURP" as what you are witnessing--------either way you have removed certain "Factory-set" items that elliminate these problems--------
Solution------Install Blow-Off-Valve/Pop-Off-Valve/Compressor-Valve-------------------this will eliminate the "gurgling" sound you describe........................
Solution------Install Blow-Off-Valve/Pop-Off-Valve/Compressor-Valve-------------------this will eliminate the "gurgling" sound you describe........................
03-27-2002, 01:28 PM
#4
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Location: Canada
Posts: 15
Re: turbo noise
a pop off valve and a blow off valve are 2 totally diferent things... a pop off valve is a saftey device made to "pop off" when the turbo over boosts.. a blow off valve only opens between shifts so the turbo doesn't stall therefore illiminating turbo lag.. there are no-such factory device... the turbo came with a pop-off valve that "poped off" at about 9psi to run any more than that you iether have to illiminate it or add stiffer springs... most people take it out and put in a pipe plug..
03-28-2002, 06:54 PM
#5
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Re: turbo noise
yes, that is totally correct. The stock setup is only to protect the engine in case of a wastegate failure. It will NOT realease boost pressure during shifts because it is on the wrong side of the throttle body. Now, back to my problem. The fluttering noise that I hear isn't just at full throttle when I shift. It will flutter at half throttle, no boost during a shift. The more boost during a shift, the more flapping noise. So, if I get a blow off valve, is won't fix the problem when there is no boost built up, thus the noise would still be there. Any more ideas?
-jeremy-
-jeremy-
03-29-2002, 11:35 AM
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Re: turbo noise
How close is your boost gauge reading towards the 0 on the positive boost side? I used to own a Silvia in Japan, and at half throttle if the boost gauge needle was near the 0 mark, and I let off the throttle, it would flutter. If your gauge is below that, say at 10 in/vacuum or so and still making the noise, I really don't know what is making the noise then. Maybe the flap on the AFM is loose?
82 ZXT
82 ZXT
03-29-2002, 03:38 PM
#8
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Re: turbo noise
That's a good point. My L28ET will produce a beneficial power increase at around 6" mercury vacuum. And if the throttle was snapped shut, flutter would occur (until I fitted a BOV).
If you are still using a n AFM, you really need to plumb the BOV as a recirculating unit. Else when it leaks, you will run a lean mixture & have a crappy idle.
I'm running MAP & have done this in order to prevent unfiltered air entering the engine.
Ben
Adelaide
Sth Australia
IZCC#1902
240Z L31ETT
L28ET MR30 Skyline
FJ20DET DR30 Skyline RS-X
If you are still using a n AFM, you really need to plumb the BOV as a recirculating unit. Else when it leaks, you will run a lean mixture & have a crappy idle.
I'm running MAP & have done this in order to prevent unfiltered air entering the engine.
Ben
Adelaide
Sth Australia
IZCC#1902
240Z L31ETT
L28ET MR30 Skyline
FJ20DET DR30 Skyline RS-X
03-29-2002, 03:49 PM
#9
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Re: turbo noise
Yes, I am still using the stock AFM, but there is no way for unfiltered air to enter the engine. I have a K&N filter attached right onto the inlet of the AFM with a 3" hose going straight to the inlet of the turbo. There isn't really any place for it too leak. Now, how do these BOV recirculating systems work? I was under the understanding that the BOV would only vent air if the boost pressure is higher than it is supposed to be (i.e. during a shift, when the compressor is still pumping and the throttle is slammed shut, creating surges) I have the fluttering noise during shifts even when there is no boost, but vaccum is 0. I am using a Autometer boost gauge so it should be accurate on boost levels and vacuum readings. I don't think that it would be the AFM flapping, because the noise goes away with the intercooler disconnected and the stock "U" pipe hooked up. This has me really fooled!!
-jeremy-
-jeremy-
03-29-2002, 05:28 PM
#10
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Re: turbo noise ( kinda long)
I think you have the bov mixed up with a wastegate. Wastegates vent off excess boost to keep a car from the boost spiking, a bov vents off the boost to protect the compressor from surge, like when the throttle is shut off. When the throttle is shut, you create vacuum which opens the bov and releases that air. A wastegate opens when there is enough boost to force open the gate to prevent any more boost from occuring so if the spring is set at 6 psi, it opens at 6psi to prevent any higher than 6. If there is no bov, then the air that needs be vented just slams into the turbo and makes that sound you hear. If you are going to hook up a bov and recirculate it, just weld one on the intercooler piping and route a line from the vent of the bov to the intake tract after the AFM and you should be fine. The reason you get fluttering w/o boost at a 0 reading is that the turbo is sorta in a "prespool". You'll probably here it whistling slightly in that range. Don't worry though, surge isn't a problem for the turbo unless it's over 5 or 6 psi. Hope this clears up any confusion.
82ZXT
82ZXT
03-29-2002, 10:46 PM
#11
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Re: turbo noise ( kinda long)
hmm.... 5 to 6 psi is really slow. Is it going to damage my turbo with this surging noise? If this is going to pose a big problem, then I am going to definatly plumb in the BOV. Thanks for you input.
-jeremy-
-jeremy-
04-02-2002, 01:01 AM
#12
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Re: turbo noise ( kinda long)
The surging will damage the turbo over time, can't really say how much life it will cut from it or how bad the damgage will be, but surging at 10psi isn't the best thing for a turbo. It would be good to have a bov plumbed in, it's cheap insurance against a time consuming rebuild.
82ZXT
82ZXT
04-02-2002, 03:02 PM
#13
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Re: turbo noise ( kinda long)
If anything, the noise is really annoying, so I am going to plumb in a BOV anyway. I have been looking around and the prices for those things are outrageous. It is just a large valve with a diaphram on top. Have any of you guys found a cheap valve somewhere other than the usual GReddy or HKS overprices stuff? Thanks for the info.
-jeremy-
-jeremy-
04-02-2002, 03:20 PM
#14
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Re: turbo noise ( kinda long)
that noise is called compressor surge. Getting a blowoff will get rid of the annoying chatter and replace it with an annoying PSHHHH. Its cool for the first week, watching people trying to figure out what the hell that noise is, but then it gets annoying. I have a greddy type-s i bought for 85$ on the net. Look around and you can find good deals.
Z Ferrari
Z Ferrari
11-04-2002, 05:24 AM
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Re: turbo noise ( kinda long)
First off a plumb back BOV is supposed to minimise venting noise... so if you don't want a PSSSSHHHTT then get a plumb back instead of vent to atmosphere.... besides vent to atmospheres (as previously mentioned) stuff up the airflow meter and cause another set of problems....
Also depending on the type of BOV you get it might still get a slight compressor flutter if the BOV is set hard as it will not be able to open on low boost pressures. dont forget that the turbo starts spinning as soon as you start your motor .. just because it's not making positive boost doesnt mean its not spinning ..
BOV's dont eliminate lag either ... they aid in the reduction of lag between shifts by stopping the turbo wheels from loosing enertia...
if you are not planning on running much boost bosche make the factory standard plumb back BOVs for nissans for around $30 - $50 AUS they are good valves but have been known to leak at high boost ... they are easy to come by as people often upgrade to an HKS or Trust etc and pretty much throw out the stock plastic one ... so try a turbo shop or something they may give you one ???
Rusty Datsun x 3
Also depending on the type of BOV you get it might still get a slight compressor flutter if the BOV is set hard as it will not be able to open on low boost pressures. dont forget that the turbo starts spinning as soon as you start your motor .. just because it's not making positive boost doesnt mean its not spinning ..
BOV's dont eliminate lag either ... they aid in the reduction of lag between shifts by stopping the turbo wheels from loosing enertia...
if you are not planning on running much boost bosche make the factory standard plumb back BOVs for nissans for around $30 - $50 AUS they are good valves but have been known to leak at high boost ... they are easy to come by as people often upgrade to an HKS or Trust etc and pretty much throw out the stock plastic one ... so try a turbo shop or something they may give you one ???
Rusty Datsun x 3
11-04-2002, 05:29 AM
#17
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Re: turbo noise ( kinda long)
i just had a look at your photos ....
what boost do you run and do you live in a hot climate ??? that intercooler is very large ! have you noticed an increase in lag with the long return pipe on the cold side of the intercooler ? also you might want to look at some sort of heat shielding running the pipe so close to the raditor !! it may suffer some heat soak being there..
Rusty Datsun x 3
what boost do you run and do you live in a hot climate ??? that intercooler is very large ! have you noticed an increase in lag with the long return pipe on the cold side of the intercooler ? also you might want to look at some sort of heat shielding running the pipe so close to the raditor !! it may suffer some heat soak being there..
Rusty Datsun x 3
11-18-2002, 08:42 PM
#18
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Posts: 162
Re: turbo noise ( kinda long)
When I installed the intercooler, I also up graded the turbo at the same time. Along with that, I changed out the tranny to the T5, which has a lower first gear. With all of that, I didn't notice any difference in lag, and did notice the benifits of the lower first gear, ie. quicker accel from stand still. As the motor sits now, it is a detuned beast waiting for more fuel. I'm still gathering the money for a haltech unit and to take out all of the stock Nissan crap computer. My plans are for coil on plug ignition and sequential fire injection with much bigger injectors. I'm hoping for around 18 psi of boost when I am done. Thanks for the tip on the heat shield (already had plans for that too after adding the haltech).
-jeremy-
-jeremy-
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