i got the fmax on my 1998 honda accord
i get the problem with the flutter sounds
air coming out from the inlet side of the turbo
instead of making the cheeeeeeeeee sound
it made a che che che che che che then no sound, it's like farting.

do u guys have any idea?
i used the HKS BOV from f-max and i put in a Blitz BOV, but same thing.
sigh

the vaccum line is hooked up correctly, it flutters even with the lighest and harderst adjustment on the bov, could it be the angle of the pipe and bov?
coz it's going from the intercooler to the throttle body air going from lower left to upper left 45 degrees, bov in between. could it be the automatic transmission?
please help
-chris

 

if its an hks super sequential, its supposed to sound like that, its not one straight phsssss. its supposed to go in steps like, pst st st st..........and the auto tranny, well, your on your own on that one......

 

it's not the super sequential, it's the Racing BOV, and i got the blitz one
sigh
this is really annoying, i'm afraid to drive the car since it's compressor surging....

 

compressor surge dude....you need to adjust your BOV, its too tight....

 

i already did, could it be the spring that is too hard?

the adjustment is already at it's loosest man
one more turn, the bolt on top will fall out

 

any leaks? maybe a bad BOV or vacuum leak?

 

blow off valve must be good, coz i tried both the hks and blitz
i doubt there is a vacuum leak or else the sound will be big
could it be there the vacuum ports are?
should thhe vacuum port tee with bov and wastegate?

 

Could it be an exhaust leak? I've heard that the turbo's in the Prelude FMAX kit hits an engine mount or something which doesnt allow the turbo to properly seal which leads to exhaust leaks at the manifold... talk about a run on sentence. :D

EDIT: you're not loosing boost are you? I would check the manifold for black soot arout the manifold flange. I dont know if the Accor kits have the same problem as the Lude kits but I would check.


[Modified by BlueShadow, 2:03 PM 12/19/2001]

 

i'm not loosing boost, i don't think there is leak
maybe i lift the car up and check below it

does it matter what comes first and what comes second at the vacuum tee?
sigh

 

Make sure the vacuum line to the BOV is very short and a good sized diameter. Long thin tubes don't work for ****.

Randy

 

What he said... I'd double check all the vacuum connections to the BOV and make sure they're correctly hooked up...

Here's somethin else. Start the car and pop the hood. Rev the engine and watch the BOV. If you rev it up, the BOV should open when the throttle is closed. If it's not moving, you have a problem. Most likely a connection issue.

 

yea, i talked to all these import people and they told me before full boost, the sound should sound like that
che che che, and the air coming out from the inlet is normal, it's not compressor surge, just air going everywhere since blow off valve is not open
he then tested it at full boost and the blow off valve actually did taht swish sound, so i guess low throttle, i get that flutter, snake, che che che che...... sound and full bost i get the deep swoosh

 

Hey CANN,

I was wondering at what RPM do you start hearing it? and what boost are you at at that RPM?

I was answering an unrelated question and I had to look up the exact definition of compressor surge. There are 2 kinds of surge:

#1 throttle shuts turbo is still compressing air against closed throttle air oscillates BOV not opening or not present.

I think you fall under reason number 2
#2 too much boost pressure not enough airflow through the system. The chirping sound heard from the turbo when lifting off the throttle while operating under boost results from the oscillating air volume.

so maybe your hitting too high of a boost setting at a low RPM (low airflow), thats what it sounds like to me.

EDIT: as for getting a recommended fix, what size turbine A/R do you have? and what size is your compressor? I dont think adjusting your BOV will help any, cause if I'm right, your surge is caused by LACK OF AIR.


[Modified by BlueShadow, 11:19 AM 12/21/2001]


[Modified by BlueShadow, 11:33 AM 12/21/2001]

 

Just to help you visualize reason #2 for compressor surges.

looking at the chart below If I was to hit 15 PSI at 2000 RPMs i would be in the surge area on the compressor map (the left side of the dotted surge limit line).

my pressure ratio and airflow rate at 15 PSI at 2000 is:
pressure ratio = 2.00
airflow = 10 LB/MIN

look at where the 2 above intersect on the compressor map. this is where my turbo would be operating in. I would be in compressor surge (high boost not enough air) and would have similar symptoms as cann.




[Modified by BlueShadow, 11:28 AM 12/21/2001]

 

i'm running 7psi of boost and 11psi
ii hear that sound under 4k rpm, at 4k rpm, 7psi is acheived for about 1 sec and a different turbo sound can be heard, and when that different sound can be heard, the blow off valves work normal.
that 'snake' sound, chechehchehe, really should be cause by lack of air, i guess the only way i can fix it is turn down the boost i get
i get 7psi of boost at 3.5k and the bov works at 4k psi, under gear 1 and gear 2, and gear 3

is that snake sound a good thing?

 

when you hear the noise changing from 4000K it is probably the compressor moving out of it's surge limit area.


I'm almost positive that the noise you're dscribing is my reason #2 for compressor surge as described above simply put TO MUCH BOOST NOT ENOUGH AIR. With this kind of surge the BOV is not really doing anything (unless you let of the gas pedal) you're applying gas pressure and its making the "snake noise" right?

You said that you get 7 PSI at only 3500 RPMS right? can I ask you a few things about your car/turbo setup?

-exactly what size engine does your accord have 2.3L (I4)or 3.0L (V6)?
-what are the turbo specs? (compressor trim and turbine A/R)

If you can turn down the amount of boost at low RPMs your right, this may fix the problem.

 

when i release the throttle at over 4k, i get regular bov, when i release throttle at under 4k, i get the snake noise, i got a 98 accord 2.3 L AT, t3/t4 turbonetics turbo, Blitz dual bov, tial wastegate

i asked a couple of ppl saying that snake sound is normal, but i thought i wil get a quieter bov sound at low rpm and loud bov sound at higher rpm, instead of low rpm snake sound, high rpm bov sound,
i doubt i can turn down the boost coz it's an external waste gate, the lowest boost i can get is 7psi.
that snake noise could be because the gears are switching automatically since i got an AT. this f-max kit is giving me a headache

 

To me, this simply sounds as if your BOV spring is too tight...it releases at high pressures because the air pressure is high enough to overcome the resistant of the BOV spring...at lower rpms, the turbo is not producing enough air pressure to overcome the resistance so you get compressed air bouncing around in your intake pipe....

try a different spring or HKS SS...may be better for your setup...

 

seemed so, but i talked to both HKS and blitz, they said the bov should work even at 2psi, and i have 7psi now, he said the default spring is the loosest already, i can only get harder springs.
so that can't be the reason
it sounds very much to me about that enuf boost lack of air

 

How long ya talking? Mines 1/8 running almost a foot and 1/2 to 2 ft.. works fine

 

I think thats whats happening as well, we're describing the same thing just in different words. There is enough boost to compress the air but not enough to release the BOV. I just said "to much boost not enough airflow (to overcome the BOV spring)"

hey CANN,

you wouldn't happen to know the exact trim on the compressor would you? B,V,E? 50? 54? 57? what about the turbine? .48? .63? .82? A/R?

T4/T3 is not specific enough

 

ahh i don't
call up fmax and ask for me please :-P

 

uh you call FMAX and find out... or something

anyways, without knowing the exact specs I really can say. Maybe it's like everyone's telling you and it's normal.

If it's not normal than maybe it's the compressor surge I was describing (too much boost not enough air. 3500 RPMS is a normal point for 7 PSI ot hit UNLESS of course you have a wrong sized compresor. OR if you're actually getting 7 PSI earlier than 3000 RPM.

 

i'm actually in asia right now since break is over, i will be back in the stateees soon however, i'll find out from f-max then

 

It is relatively normal. I actually always tried to make that sound at low RPM on my old Civic . At low RPM, during regular daily driving, you are not putting a lot of load on the system, therefore, your are scooting along just fine, without a lot of stress, and without a lot of boost. It may also have something to do with the shifting characteristics of your automatic transmission. Automatic transmissions for the most part, do not shift as fast as people driving 5-speed, at low, or high speeds. Team the slower shifting with low amount of boost and low RPM, and you will get the lazy, snakelike blow off sound, rather than the quick snap of a blow off that is being utilized at 12psi and 8500rpm. I guess you can open the blow off valve more if you do not like that sound. That's really all I can think of. I know exactly what you are talking about, like I said, I always tried to make that sound, especially when other Hondas were around, because that just screams TURBOCHARGED BITCH!!!...without actually flying up on them and shooting a loud blow off valve sound. I wouldn't worry about it, I highly doubt there are any vacuum leaks or other problems.