Knock Reading

[Mr_G]

Hey guys,

Got abit of a myth about my knock level... My car has been running fine for the past 6 months, since getting tuned. With abit of flat stick, the max knock it would read on the PFC was around 30, and I always used BP Ultimate.

Just recently, I put in a batch of Vortex Gold and that seem to run alot smoother, and had no problems.

Went back and got some ultimate, gave it flat stick and engine check light came on. Knock was over 60,highest hit was 125 which isnt good!

I gave it a few squirts here and there, and it seems that the knock only goes crazy SOMETIMES on flat stick.

I put vortex back in, and the knock level has reduced, however its still hits higher than what it used to.

This usually happens downshifting from 4th to 3rd and giving it some stick.... No modifications have been changed since getting the car tuned, everything still the same way it was setup. The sparkplugs were last changed when the car was tuned.

Should I be changing the sparkplugs first to see if that does the trick?

My usual knock readings before this saga was around 10-20, 30 max!

[Sumo]

Spark plugs normally only cause a missfire.

I would think that something has adjusted your timing a bit, I'm not a mechanic but that would be my educated guess.

Cheers

Sumo

[Mr_G]

No one has touched the timing what so ever so that pretty much rules out the timing... Anyone else have any ideas?

[courier33]

If the fuel pump is the original one, maybe its on its way out and starting to run the engine lean under full throttle.

[GIGOLO]

Could be a bad batch of fuel, I have had "suspect" fuel require the ign timing to be reduced up to 3 deg.

Could also be your Crank Angle sensor, although if it doesn't knock with the Vortex gold I would suspect the Ultimate as being "suspect".

[mad34]

Hey guys,

Got abit of a myth about my knock level... My car has been running fine for the past 6 months, since getting tuned. With abit of flat stick, the max knock it would read on the PFC was around 30, and I always used BP Ultimate.

Just recently, I put in a batch of Vortex Gold and that seem to run alot smoother, and had no problems.

Went back and got some ultimate, gave it flat stick and engine check light came on. Knock was over 60,highest hit was 125 which isnt good!

I gave it a few squirts here and there, and it seems that the knock only goes crazy SOMETIMES on flat stick.

I put vortex back in, and the knock level has reduced, however its still hits higher than what it used to.

This usually happens downshifting from 4th to 3rd and giving it some stick.... No modifications have been changed since getting the car tuned, everything still the same way it was setup. The sparkplugs were last changed when the car was tuned.

Should I be changing the sparkplugs first to see if that does the trick?

My usual knock readings before this saga was around 10-20, 30 max!

<{POST_SNAPBACK}>

I hear you i have a powerfc and my knock count went to 133 now the stock knock sensors are prone to picking up extra noise from the engine, now if it is only happeneing at high rpm then it is definately a knock sensor picking up excessive noise BUT if it is doing it all the time then there is too much timing. ther is a timing correction function on the powerfc you might want to subtract 1degree of timing if that reduces the knock then you know that there is too much timing, hope this helps

[Sydneykid]

Hi guys, are you looking at the max knock reading? I find that to be a waste of time as it is missleading, the max knock may only be for split second, caused by exterior (to the engine) noise. I have had max knock at idle on more than one occasion. You really need to have the trace on and go for a drive with a passenger. That will tell you how often and at what RPM you get what knock readings, then you can make a decsion as to how relevant the max knock reading really is.

cheers

[TurbostyleR]

yeah my knock reading was a little funny when i had it on the dyno about a week back...

Im assuming its perhaps just exterior noise as there was no signs of pinging from the exhaust and my tuner did not hear any pinging through his ear peice...

I dunno, im putting my situation down to a faulty knock meter so im getting it replaced with another one i have lying around...

[Robo's]

I get a knock reading of 40 everytime i start my car up

[Cubes]

Even with forged pistons I get a max knock of 10 on the initial crank, idling in 4degree temps when you can hear the pistons slapping the knock sits on 1.

For mine to see the tell tale sight of a puff of fuel from the rear knock levels are around 100.

I never have the odd unusual spike, well I did, only when the injectors were clagged and dirty.

[Mr_G]

Thanks for the input guys, been prety helpful... Its usually only if i take the car over 5k rpm, that I would get a higher than usual knock level.

It never used to do it tho, and with the vortex gold in the car at the moment, it still does it... However I had the check light come up on the dash the other day with the ulitmate in...

I think ill go easy on the car, and take it to my tuner soon. I have had the fuel pump changed just before the dyno tune back in feb, with a 040 bosch, and was a brand new pump too.

[Cubes]

It does sound like a fuel pump issue, but you never know.

The joys of owning a performance car. Off to the dyno it goes.

Edited September 1, 2005 by Cubes

[Mr_G]

HAHA, ya, ill granny it till i have time to take it down, got to wake for uni semester break!!!

[Bl4cK32]

I have the same problems. My car was tuned a while ago, and max knock reading i got was 10.

Recently it knocked its head off when doing a wot run, i looked back and had a big puff of black smoke, knock was 110. When my car was in for the tune last time i had cas problems. My guess is that my cas is playing up again....

I wont know till i go back to the tuner for sure, but your problem sounds exacltly the same, as no one has touched my car. I reckon the timing is playing funny buggers...

Edited September 2, 2005 by Bl4cK32

[Mr_G]

I have the same problems. My car was tuned a while ago, and max knock reading i got was 10.

Recently it knocked its head off when doing a wot run, i looked back and had a big puff of black smoke, knock was 110. When my car was in for the tune last time i had cas problems. My guess is that my cas is playing up again....

I wont know till i go back to the tuner for sure, but your problem sounds exacltly the same, as no one has touched my car. I reckon the timing is playing funny buggers...

<{POST_SNAPBACK}>

HAHA, yeah, im going to change my fuel filter & spark plugs soon, so hopefully that might be the problem... Im only running coppers, so I could possibly have a fowled plug.

I cant see if theres a puff of black smoke, cause usually the car is pretty quick once giving it some stick, and you prob dont wanna look back, well my tints are pretty dark too...

[B0oStEr]

I have the same problems. My car was tuned a while ago, and max knock reading i got was 10.

Recently it knocked its head off when doing a wot run, i looked back and had a big puff of black smoke, knock was 110. When my car was in for the tune last time i had cas problems. My guess is that my cas is playing up again....

I wont know till i go back to the tuner for sure, but your problem sounds exacltly the same, as no one has touched my car. I reckon the timing is playing funny buggers...

<{POST_SNAPBACK}>

Why does it blow smoke when the knock reads high?

My car has started blowing black smoke when it's cold.

Can't say what the knock levels are as I haven't fitted my pfc yet.

What goes wrong with the CAS and how can you diagnose it?