Can a LWFW cause Knock?

[Mr-C]

Hey gang,

 

Troubleshooting some knock issues and wondering if this can be a leading cause?

 

I have an ACT LWFW since I've purchased the car in 2011 (installed by previous owner) at the time it had an Exedy Stage 1 clutch kit....I've always heard a chatter/gear rattle type noise and while the car was still on guarantee the transmission got changed 1-2 times for a new tranny thinking it was the issue but the noise persisted.

 

Some little time later I ended up installing a TSK3 kit and a new Bully Stage 2 kit (stage 1 started to slip).....didn't improve much if anything at all. I even started to hear a "wizzz" type noise when declutching in 1st gear (maybe due to the TSK?). Everything seems to drive/clamp ok, the pedal feels nice also but that damn noise is always present when coming to a stop and taking off....even at idle I can hear it but disappears as soon as I engage the clutch.

 

All this to say I recently swapped in a new forged block and got a tune and since then I'm getting ALOT of fine learn knock (as high as almost -12 at around 2200 rpm), this after changing the knock sensor (tuner recommendation) and a leaky vacuum hose.

 

In learning more about knock, many talk about "false knock" due to the sensor picking up vibrations/frequencies other than the actual knock events happing in the engine. I've sent data logs to my Tuner but he's on vacation right now and will only hear back from him in about 1 week or so.

 

I'm starting to wonder if perhaps the LWFW gear rattle is being pick up by the knock sensor and affecting things? I should have an 06-07 WRX SMFW at home and thinking of installing to see if that would change things, but that's no easy job when you don't have the right set up at home.

 

Would love to hear your thoughts....am I completely wrong in my thinking?

 

 

Thanks,

[m sprank]

If the fw is in the 12lb range it can cause all sorts of issue. Crank angle sensor misses the pick up, etc.

 

With anything above -4deg flkc you need to find the issue with minimal driving. If the knock is real you will lose a piston.

[Mr-C]

If the fw is in the 12lb range it can cause all sorts of issue. Crank angle sensor misses the pick up, etc.

 

With anything above -4deg flkc you need to find the issue with minimal driving. If the knock is real you will lose a piston.

 

Ok, so my thinking is not that crazy!!

 

I believe it might be around 14lbs +/-.....I really should have weighted it when I sent it to get resurfaced during the motor swap (DOH !!!).

 

Those flkc numbers definitely had me worried, especially when I saw the DAM drop to 0.375 then came up to 0.875 and stayed there the remaining drive back to my GF place, when I went back home that night the DAM came back to 1.0 after less than 3min of driving.....as I mentioned earlier the flkc would appear up to about 2200-2400 rpm range then goes to 0, so perhaps that's the "zone" I'm getting the gear rattle from the lwfw?

 

Haven't drove the car since (almost 2 weeks now) and waiting to hear back from my Tuner once he reviews the logs.

[xtea]

If you have light weight crank pulley and light weight flywheel this makes

Sense.

[KevinEdgar]

Just chiming in to say I also have a LWFW and I get crazyyy knock readings probably due to the chatter of 6 puck unsprung clutch and the LWFW.

[Mr-C]

Just chiming in to say I also have a LWFW and I get crazyyy knock readings probably due to the chatter of 6 puck unsprung clutch and the LWFW.

 

Thanks for the feedback.....is your car tuned by a tuner, wondering if he had problems tuning your car?

[KevinEdgar]

Thanks for the feedback.....is your car tuned by a tuner, wondering if he had problems tuning your car?

 

No my car is only tuned by cobb APv3, OTS stage 2+