WRX knock problem
WRX knock problem
(OP)
This is just an FYI, really. But....
We just, after several days of fiddling, found out why my crew chief's somewhat modded WRX would just 'lay down' at several different RPM's, always the same. Apparently the knock sensor would retard the timing when it "heard" the rear alternator bearing that was going bad 'vibrate' at certain rpm's. New bearing and now the thing runs like stink. It's making good power at 18psi boost with no flat spots now. I'm too far out of the loop on some of the newer technology, I guess...Whoda thunk it?
Rod
We just, after several days of fiddling, found out why my crew chief's somewhat modded WRX would just 'lay down' at several different RPM's, always the same. Apparently the knock sensor would retard the timing when it "heard" the rear alternator bearing that was going bad 'vibrate' at certain rpm's. New bearing and now the thing runs like stink. It's making good power at 18psi boost with no flat spots now. I'm too far out of the loop on some of the newer technology, I guess...Whoda thunk it?
Rod





RE: WRX knock problem
How did you manage to figure it out?
RE: WRX knock problem
It used to run alright. What changed, how long has it been making that noise. Then noise is vibration, knock is vibration, I wonder?
Using the old knock sensors on the sides of the head heard the bearing and replaced it and then it was noticed the problem coincidently went away.
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RE: WRX knock problem
RE: WRX knock problem
Also I expect that an exhaust rattle is a very different frequency to knock, where a noisy bearing might be in the same frequency as knock.
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RE: WRX knock problem
www.retallickeng.com.au
Was told it couldnt be done, so
i went and did it!
RE: WRX knock problem
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RE: WRX knock problem
The 1085s didn't have them. That 1985 did. Most US models of 240 got them in 1983 or so.
The factory recommended valve clearance for 240s got tightened up at some point, reportedly to avoid fooling the knock sensor with heavier valve clickety clack.
RE: WRX knock problem
Rod
RE: WRX knock problem
RE: WRX knock problem
Obviously you place the blunt end against your ear and touch the sharp end on the susso part. It is quite an efficient stethoscope and makes one realise just how much engine noise can be transmitted into the passenger compartment via control rods, cables and levers.
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RE: WRX knock problem
Rod
RE: WRX knock problem
Some of the folks on the vibration analysis groups call them "yellow handled analyzers"
RE: WRX knock problem
RE: WRX knock problem
RE: WRX knock problem
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RE: WRX knock problem
RE: WRX knock problem
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RE: WRX knock problem
RE: WRX knock problem
Thats an interesting case though
RE: WRX knock problem