I got my blms in good shape 124-129.

I get knocks at 1400-1470rpm @ 40kpa only! Not that much, it pulls like 2-4 degrees. And when I get past that point, no knocks.
I have read the plugs, no sign of detonation.
I even set the knock attack rate to 0 to lissien for knocks.
I hear nothing and the engine is super smooth.

I got hotcam, 1,6rrs, headers.

I know its hard to tell, but could this be false knocks? I belive so I just would like to hear your ides?

 

Have you tried pulling timing?

The stock heads are really prone to causing detonation and it's not uncommon to see it begin in the low rpm range like you are seeing due to "lugging".

 

thanks for your answer

Yes I have pulled about 4 degrees of timing before and at the critical rpm, no change, Im running around 24 in that area ( 1400rpm 40 kpa ).
The strange thing is that the next point in my timing map is 32 degrees with no probleme? ( 1600rpm at the same Kpa range ).
And no knocks at wot. Its all around that 1400 rpm scale.
Could you explain about (lugging).
Also the car is very sensitive to a lean condition. If I get abow 132 BLM I get knocks.

Regards

 

What does your scan tool show for timing when this occurs? The same as the value in your spark table?

 

yes. no matter how much i retard the timing i still get it

 

I don't suppose you get the same condition in NEUTRAL or PARK? I was thinking about mechanical, harmonic noise.

 

Slightly mute your knock sensor with teflon tape. That little ammount of noise that KS is picking up could be from your 1.6 roller rockers.

 

Good suggestion Jeff. This will differentiate whether it is caused by "load" or happens at the RPM range regardless of load. Also, have someone slide underneath the car and see if the engine is twisting under torque and causing the exhaust to hit the frame.

Look at your motor mounts, transmission mounts and exhaust system too. I know a number of people who had an "irritating" buzzing sound that occurred at a very specific RPM range and it turned out to be the baffles in the muffler. You may a similar problem with your cats where the material inside is loose and causing vibration at a specific RPM range. And due to the proximity to the engine, is triggering the KS.

As for roller rockers, I have those and when properly adjusted I get NO knock indication. Try readjusting those too. And, if you have a high mileage motor don't overlook the possibilty of your roller lifters being partially collapsed - where they are a little loose at your problem RPM range and pumping up as the rpm increases.

I don't recommend "desensitizing" the KS by mechanical methods like teflon tape. You are disabling it THROUGH OUT the entire operating range. Control it within the ECM at the specifc RPM range is a better alternative.

Remember that the KS operates in a different frequency range than the human ear. The KS hears things the human ear does not and vice versa. It is not uncommon to have the "reverse problem" where the KS is NOT reacting but you can audibly hear the detonatation.

 

thanks for all the inputs

This is the update:

The knock counts are ridiculous at the critical rpm range ( 1300-1500 ). I get the knocks when i reeve the engine in neutral also. The knocks is less when I put load on the engine ( going uphill in the same rpm range). ANd they are less when the engine is cold. I get most knocks when crusing at around 40kpa around 1400rpm.
I noticed I got resonace from the exhaust just in that rpm range, I thougt mayby that could be something?

I have been under the car and lissen for strange sound while a friend reeve the engine, I cant hear nothing but the usal exhaust/engine noise. THe header does not touch the frame.
I readjusted all my RRs.
I tried to back out 10 degrees of timing in that area, whitout any luck! ?
And abow 1450rpm its like you turn off a switch, NO KNOCKS??
I also noticed that if I going on a higway at around 3000rpm then let off the gas pedal, i get knocks as soon as the rpm drops to the magic 1400rpm mark, and then when it past 1300rpm the knocks stops...

I read the plugs, no sign of knocks.
I used octan booster, no luck
I get no knocks at WOT
I backed out 10 degrees of timing before,at,and after that rpm range. I have pushed in alot of fuel also just to try that out ( hade the blms to 108 at one time ).
HEaders does not touch the frame
I got ALOT of header tick, mayby that could trigger it?
Im going nuts..
My next thing will be a new KS.

THanks for all the tips you are giving me.

 

You could buy a stetoscope from claes ohlson (swedish shop) for 95 kr and strap it to the block and then listen to the engine......


I know another guy in sweden who did this when he had false knocks. I will try this also with my knock problem......

 

Might try the Percy's aluminum header gaskets to repair the exhaust leaks. They seal great and might give you a little insulation from the headers to the block. They are very soft and thick. Just a thought

 

thanks will try that..

 

Yes

 

yeah im starting to think that to... I think i ruled out real detonation, i think....

I will set my spark retard to 0 in that rpm range now. And if she goes BOOOOM its time for 383

Serious, I think it will be ok..
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