Can't shake the knock...

[alexeiwoody]

Have been speaking to some other people too... Michael South said "Put the wg preload back to where it was, knock in high rpm is from turbo back pressure pre turbine, that can blow your engine".


He suspects it is more likely cam gears... suggested "hold 1500 rpm and see if the cam advance is stable or mores more than 1 degs". Will give that a go...

dr20t and Alexi - would the actuators you have suit a blouch td05 18g? I'm told the blouch's have something unusual as far as how their actuators hook up or something?

Mine is off a blouch 20G, they have the weird bend which makes finding actuators really annoying - hence I asked

Will let you know how I go by end of today

[KiDo_Tuning]

Have been speaking to some other people too... Michael South said "Put the wg preload back to where it was, knock in high rpm is from turbo back pressure pre turbine, that can blow your engine".

Never had knock at high rpm though, it has all been at spool around 0 to 7psi and cam timing/fueling/ignition timing is right. Miff88 on ozfoz had the same issue with it rattling... but the range was at 1.3g/rev so it never listened for FLKC where yours is listening for it in that range.

[cynner]

Since tightening the actuator preload, the highest RPM/load/boost when knock is occurring is 9.2psi, 3400rpm, 2.05 load. No chance of that being turbo back pressure issues?

[KiDo_Tuning]

Since tightening the actuator preload, the highest RPM/load/boost when knock is occurring is 9.2psi, 3400rpm, 2.05 load. No chance of that being turbo back pressure issues?

No, just has more spring holding against the housing to stop rattle, as the flap wont move. Thats why it moves with spring pressure and is why we did the WG tune to confirm its noise from WG. We used to do this 20 odd years ago with SR20DET's as they had the same issue with WG flaps on T25/T28's

[cynner]

I'm still confused as to why the noise was still there after disconnecting the vacuum line to the actuator. Wouldn't that hold the flap shut all the time?

[dr20t]

Matt is right - and unplugging boost control won't stop the wg from chattering completely

[KiDo_Tuning]

It is mechanical. The solenoid connected can only hold 0psi since that is boost pressure but also ambient pressure(or close enough)

So the air pressure inside the WG can is still the 'same' regardless. More preload just holds it tight until it opens and chatters

[cynner]

May have had a little success... I have tried tweaking the tune very slightly.

Since increasing the actuator preload, there's no longer any knock at low load (0.97), low rpm (1900rpm), low boost (-1 to +1 psi... around atmosphere). Instead there was a tiny bit of knock on medium load (1.80), medium rpm (3300rpm), medium boost (+3 to +6psi). At first I thought it has simply moved the actuator "noise" to higher boost because it is opening the actuator later.

However, I tried pulling -1.4 degrees of timing from the cells where the knock was occurring (1.4 being the amount of timing it was pulling in LV) – and now I no longer get knock there. Just got back from about 1 hour of driving, and it seems good.

Here is a new LV:


Here is a log - it seems to come onto boost nicely, hold it nicely, and no knock anymore:
http://www.datazap.me/u/cynner/logs-les ... a=1-2-4-13

My only concern is that now when I change the Feedback Knock Correction settings back to factory settings (FBKC enabled at low loads and FLKC enabled at higher loads)... it picks up FBKC very easily on low load again. Is it safe to adjust these so that FLKC is enabled at lower loads instead? For whatever reason FLKC seems more resistant to picking up this random noise... apparently all COBB tunes are like this?

Kim

[cynner]

Gah, spoke too soon - it just dropped -1.4 timing into the 0.00 Load/2000 RPM LV cell...

[bigBADbenny]

Forge might have an option for you:
https://www.google.com/search?q=forge+m ... 72#imgrc=_
Actuators:
http://www.forgemotorsport.com/content. ... talog=0001

Actuator components:
http://www.forgemotorsport.com/content. ... talog=0019

Quality stuff, PROVA rebrands their IWGA's and BOV's.



So is there anything wrong with disconnecting the actuator rod and wiring the flapper open for testings sake?

[cynner]

Yeah I emailed Forge after you suggested them, they look really good! A bit more solid looking than the cheaper brands. For the sake of $100 I'd probably go for better quality.

I suppose the only downside of wiring the wastegate actuator flap open would be that it might be hard to make boost, but I suppose it's a way of testing. Although Alexi has found his old Blouch TD05 20g actuator, so I'd probably just bung that in for a test if I'm going to pull the TMIC, heat shield, etc. of again...

[cynner]

Just an update - Matt did some testing in person while in Tassie, and is certain it is the wastegate flapper (on the turbo itself, not the actuator). His theory is that sudden changes in exhaust pressure are causing the flap to knock (he was able to reproduce it quite loudly, and it made quite a thunk).

This means there's no point replacing the actuator. A bandaid fix may be attaching a spring to the swivelling part of the wastegate flapper, putting tension on it and stopping it wobbling about...

Other than that, maybe changing to an external wastegate...

[cynner]

I'm pretty sure things are fixed!

Replaced the actuator with a Turbosmart one, but while doing that my mechanic noticed the dog-bone that goes between the firewall and the transmission was rattly... the bushes had perished and one was split. So that was replaced too...

So I'm not sure which was the problem exactly - but either way, so far it seems to have fixed. I just need to load a new tune on with the knock thresholds settings back to stock to confirm.

The new actuator has made a difference to the boost too - it pulls a lot harder. I got one of the Turbosmart twin port actuators (14psi)... with a custom bracket and the rod fabricated to suit the blouch.

[bigBADbenny]

That's awesome
So the stock pitchstop bushes were shagged?

Those TS iwga's look great too, quality

[cynner]

Yeah, the stock bushes were fairly well stuffed, and one of them was cracked right through. It mounts so close to the knock sensor, I'm pretty sure that was the issue.