I am staring to hear a slight chatter/knock as the turbo begins to spool up. It is most evident when pulling away from a complete stop and steadily building up speed. As my boost gauge gets to zero from vacuum and starts building boost the chatter/knock starts. It is not very loud, but audible without the radio on; it does seem to go away if I clutch in. I cannot determine if the noise stays with higher speeds as the engine, exhaust and road noise become too loud.

The latest change to my set up was installing back the stock airbox with a drop in filter; the car originally came (and was tuned) with the SPT intake. I installed the airbox this morning (Saturday), but still had to use the car for work and errands throughout the day. Obviously, I was going to have the tuner look at the map as soon as possible during the week.

What can the knocking/chatter possibly be? There is no noise or knocking when then car is starting, idling or cruising below boost. The exhaust does not smoke or produce excessive condensation. Below is the listing of all the major modification (I am sure I am forgetting something). Thanks!

Stock WRX 2.5Lt block
FP 20G 8cm turbo
Spearco TMIC
Titek DP
Invidia UP
Borla “Hush” exhaust
DW 640cc injectors
Walbro 255 fuel pump
Agency Power crank pulley
Ported/polished/coated STi headers
Exedy Stage 2 clutch w stock flywheel
COBB AP w/ professional dyno tune
Mobil 10w30 synthetic oil

 

ill look at it tonight. if the piston is still in the block than your fine lol. or maybe its the fuel level again.

 

ouch, knocking on acceleration/load = rod knock, bet you a dollar

btw got the seat down to GST yesterday, thx!

 

Does it stay with your foot on the clutch? That will help figure out if its drivetrain.

Who tuned the car? Has anything been changed since the tune?
How much boost?

 

gasket leak?

 

so the noise is coming from the engine,
since you mentioned no noise when off the clutch, and if it was from the tranny, i wouldve guessed throwout bearing or input shaft..

 

Thanks for everyone's input! This is gonna be hella response...

It is not rod knock I figured out that much; its a faint clicking/ticking/chatter (I listened to rod know videos and had people at tonight's meet drive with me). Also, I thought rod know does not go away and is apparent when the car is just idling?

Sweet! Thanks for dropping it off; I will let you know when its ready

No, the chatter only appears under light boost (between 0 and 5 psi boost) and acceleration; like cruising or trying to hold slow speed in local traffic. If I cruise below boost, there is no sign of the noise. Or if I go above light throttle I cannot hear it either; I almost have to deliberately build boost/acceleration slowly and keep holding it at that pace to replicate it.

The car is tuned for 20 psi but tappers down to 18 well before the red-line. As described in the original post, the only thing changed since the tune is replacement of SPT intake back to stock. My hopes is it is just intake related (just different/restrictive flow that needs to be tuned for?), but its just too weird of a noise that I have not heard before or read about when going back to stock intake...so I got concerned.

I am not even certain it is a new noise since the SPT intake was so loud; plus I always drive with radio on and even with it as light background noise you would have hard time hearing it...

Hope not...there is no apparent loss in power, drivability, difference in idle, change in exhaust or oil/coolant levels...

I have had a throw out bearing before and the sound is totally different; a bearing is more of a continuous squeal instead of a repeating chatter, right? Input shaft is a good suggesting, but again, the noise only appears when lightly building up boost between to 0, up to 5 psi...I would think input shaft would not be limited to such a specific conditions?

 

thats funny i have a similar problem, noise in neutral or in gear when engaging clutch and at low speed...goes away when car is warmed up, is louder when car is really cold outside...and a shop narrowed it to the first slip fitting on my hush exhaust leaking (to stock dp with no adapter, even though it is completely tightened)

im gonna install a dp soon so im hoping itll go away when i put the maddad adapter on

 

What oil filter? I have found non oem oil filter cause valve train tick.

Could also be tip in knock. I found that with my tune from GST once. This happens just at throttle tip in.

You might also check your motor mounts too.

 

Hmmm your problem might be different than mine...Everything is normal in neutral or when engaging the clutch and I get my noise regardless of when (hot/cold) I drive the car. I drove the car around this morning trying different things and the noise is just isolated to what I have been describing. As far as the Hush, I got all new adapters and gaskets when I put the exhaust on, but I will double check for any exhausts leaks just in case.

I always use Subaru OEM oil filters and have the Group N engine and transmission mounts. However, how would the mounts make a difference? I am having a hard time picturing how they would cause chatter, if anything should it not be a vibration at higher rotations...

How bad is tip in knock? I am assuming it is nothing that can't be solved by some map adjustments? I am somehow thinking that any sort of knock would happen off and on boost; or am I wrong? I am meeting with the tuner later today to hopefully diagnose the problem.

Also, Nasioc people think it is the GM 3-port boost control solenoid...seems like another good possibility as well.

 

Go search romraider about tip in knock.
Also I hope you have logged the car before and after your tune. And log it again before and after the tuner looks at it again. That is most times the only way to prove later the tune is **** and caused a bad motor.

I think its tip in knock. Log it and see if its pulling timing right at 2-5% throttle input and any speed.

If the mount is bad it can vibrate. Or is loose....

 

Sounds like waste-gate clatter.

 

n00b question, how do I log my car? Apparently I have not do so since I have no clue what it is, but a very good suggestion for the future. Thanks!

As far as possibility of having a bad motor; I think it is a little early to go that far, start thinking the tune is bad or delegating fault. I fully stand behind my tuning shop, the tuner and the their work.

 

I would love so it to be something simple as that :banana:

That's what I am hoping it is right now, something simple that I just did not hear before or just comes with having a highly modified car.

 

Yea...mine started to make that waste-gate noise when I got turbo back exhaust. I was all worried about it at first...but I don't think it is a serious issue...just annoying.

Waste-gate clatter/flutter usually is at low RPM under lower boost during acceleration, very much during the times you describe.