Robbks wrote:libz05 wrote:i have the same problem!! engine rattle and it gets quite annoying!
did u find out the issue ?
It's AVCS related
as you go from 1600rpm to 2000rpm, the AVCS system advances the intake cam by about 30 extra degrees. and as such the mechanism on teh front of teh camshaft rattles as it whips around quickly
see maps of AVCS angle here
viewtopic.php?p=304468#p304468
libz05 wrote:thanks rob!
what would you reccomend!
coyote wrote:Sure, a GTR is fast ... but it's about as interesting as listening to grass grow.
libz05 wrote:i spoek with jay.ritchie
he said it may be this:
viewtopic.php?f=16&t=19918
peadya100 wrote:Have you had your car looked at by a mechanic just to make sure there isnt something wrong with your engine? Better safe than sorry, theyll be able to diagnose it pretty quickly and on the off chance its something major at least you will have got to it pretty quickly.
coyote wrote:Sure, a GTR is fast ... but it's about as interesting as listening to grass grow.
Robbks wrote:libz05 wrote:i spoek with jay.ritchie
he said it may be this:
viewtopic.php?f=16&t=19918
well does it do it all the time like the video in the link above?
or is it just a quick chirp as you're driving?peadya100 wrote:Have you had your car looked at by a mechanic just to make sure there isnt something wrong with your engine? Better safe than sorry, theyll be able to diagnose it pretty quickly and on the off chance its something major at least you will have got to it pretty quickly.
Nope
I can tell when it's a concerning noise and know more about Subaru engine noises than half the mechanics around here.
it only does it at specific load and rpm conditions indicated by the ACVS advance maps posted before.
i.e doesn't do it when free revving
I'm always interested in these mysterious diagnostic powers that people believe some mechanics possess.
peadya100 wrote:Just curious Rob, how can you be so certain of the diagnosis when you havent heard the noise?
peadya100 wrote:Mine turned out to be something completely different to everyones guesses.
Robbks wrote:peadya100 wrote:Nah its not happening on boost, its happening at 1500-2000rpm.
at the point right before boost come one.. like 0-1psi on medium throttle..?
If so i had two causes of this noise on my GT Fozz.
1) Wastegate chatter. ...........
......................
2) Compressor Surge.....................
...................
otherwise it could just be a rattling heat shield.
coyote wrote:Sure, a GTR is fast ... but it's about as interesting as listening to grass grow.
Robbks wrote:peadya100 wrote:Just curious Rob, how can you be so certain of the diagnosis when you havent heard the noise?
I'm certain of the noise that I'm hearing in my car.peadya100 wrote:Mine turned out to be something completely different to everyones guesses.
as for your noise..you'll see my first post had the solution
my options 1 and 2 had specific conditions that were never commented on..Robbks wrote:peadya100 wrote:Nah its not happening on boost, its happening at 1500-2000rpm.
at the point right before boost come one.. like 0-1psi on medium throttle..?
If so i had two causes of this noise on my GT Fozz.
1) Wastegate chatter. ...........
......................
2) Compressor Surge.....................
...................
otherwise it could just be a rattling heat shield.
peadya100 wrote:For example, my car made its noise at the exact same engine revs, and didnt do it free revving, only under load.
Isnt it a little early to definitely say its the AVCS thing you were talking about?
bass_straitener wrote:peadya100 wrote:For example, my car made its noise at the exact same engine revs, and didnt do it free revving, only under load.
Isnt it a little early to definitely say its the AVCS thing you were talking about?
I think I predicted as well the heatshield noise. That area is subject to extreme heat and they tend to fail.
You only hear it due whilst under load due to the resonant frequency being different than when free revving.
My wife's Foz has a similar noise at the moment.
coyote wrote:Sure, a GTR is fast ... but it's about as interesting as listening to grass grow.
Robbks wrote:without driving it or opening the bonnet I can't
But that's why we ask the posters to provide very specific info which very few are capable of doing.
i.e how long does it rattle for. (in my case it's a very short "tiktik")
does the rattle stay constant if you can maintain the load and rpm for a few seconds
does it rattle on acceleration, deceleration or constant throttle?
if you hold rpm but quickly blip the throttle, does it change (This was the key to diagnosing my own compressor surge issue)
And provide a video/ sound clip/ logging info if you have it/ can get it
Some of these questions got lost in the earlier diagnosis.
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