Help me with ignition knock (UPDATE)

[BAH2SS]

Originally Posted by acammer

Seems very odd to have that much knock under steady state. What's the AFR look like? What's your tuning buddy think of it?

I am going back to the dyno now to make further adjustments after the cat delete

Originally Posted by gtstorey

Looks like Bahrain uses the RON octane rating so 95 RON is about 90 by us ratings.

We are using MON and i am working in Bahrain petroleum company lol. So i am 110% positive that our fuel is goof

Originally Posted by davidscamaro

Your using the wrong spark plugs , 41-110 are the plugs you need , 41-104 are for zl1 or ls9 corvette

Yup, smaller gap and one step colder plug to help woth knocking issues. It had 41-110 in it. Going to a step colder plag and closing the gap should've made things better though nothing changed.

[RobZL1]

Have you checked to make sure you don't have the exhaust system physically knocking into something, or something else causing external noise that might set off the knock sensor? Maybe a failed motor mount causing excessive motion which leads to hard metal contact under load?

If you've got that amount of knock with only 18deg max timing and known good fuel, it's not real knock. You've got something else going on in my opinion.

[acammer]

Originally Posted by RobZL1

Have you checked to make sure you don't have the exhaust system physically knocking into something, or something else causing external noise that might set off the knock sensor? Maybe a failed motor mount causing excessive motion which leads to hard metal contact under load?

If you've got that amount of knock with only 18deg max timing and known good fuel, it's not real knock. You've got something else going on in my opinion.

Agree. The 104s should be fine, that's a cooler plug than a 110 and should help. Doesn't seem like it's real knock. I would toss in some high octane fuel, or a bottle of booster, and see if you note any changes. If it's real knock, that ought to help and you'd see a decrease in KR. If it's false, it'll stay the same.

[BAH2SS]

Originally Posted by acammer

Agree. The 104s should be fine, that's a cooler plug than a 110 and should help. Doesn't seem like it's real knock. I would toss in some high octane fuel, or a bottle of booster, and see if you note any changes. If it's real knock, that ought to help and you'd see a decrease in KR. If it's false, it'll stay the same.

So currently at 18 degrees of timing after deleting the catalytic converters with 1-2 degree of KR. However, after the dyno i did two pulls the first one couldn't hear any actual knock at all although it's been detected randomly on different cylinders.
We actually have 98 octane fuel here and used it twice with the same results.

Second pull, 2nd gear 3500RPM TO 4500 I heard the most awful knock ever though the ECU did not detect the knock it self and it waa for a split of a second.

Originally Posted by RobZL1

Have you checked to make sure you don't have the exhaust system physically knocking into something, or something else causing external noise that might set off the knock sensor? Maybe a failed motor mount causing excessive motion which leads to hard metal contact under load?

If you've got that amount of knock with only 18deg max timing and known good fuel, it's not real knock. You've got something else going on in my opinion.

The exhaust sounds loud after the cat delete so i am positive there is no restrictions in the exhaust.

On the dyno removed the paper air filter today it made 404. With the air filter it made 397 although the air filter is quite clean not that bad.

[RobZL1]

Originally Posted by BAH2SS

So currently at 18 degrees of timing after deleting the catalytic converters with 1-2 degree of KR. However, after the dyno i did two pulls the first one couldn't hear any actual knock at all although it's been detected randomly on different cylinders.
We actually have 98 octane fuel here and used it twice with the same results.

Second pull, 2nd gear 3500RPM TO 4500 I heard the most awful knock ever though the ECU did not detect the knock it self and it waa for a split of a second.



The exhaust sounds loud after the cat delete so i am positive there is no restrictions in the exhaust.

On the dyno removed the paper air filter today it made 404. With the air filter it made 397 although the air filter is quite clean not that bad.

I'm not saying you have an exhaust restriction. I'm saying that the exhaust pipe (or something) is probably smacking something under the car. If you are saying that you increased the octane and still get the same knock, then it only confirms that the knock isn't real...

[Moto-Mojo]

You guys are way ahead of my skills and mods but I haven’t heard an ignition knock since I fixed one in my mother’s 1975 Cutlass...in 1978. I though that’s what knock sensors were for? Did they get tuned out?

[Russell James]

What brand of air filter? And I wouldn't run it without an air filter. The air filter pleats are there to create laminar air flow across the MAF. Without laminar air flow across the MAF - ie either a stock air filter or a properly engineered aftermarket one, the MAF reading will be all over the place from turbulence.

Take a close look at the MAF sensor, pulled out of the intake. Make sure there are no fuzzy fibers burned on the hot wire element. That can cause a lean condition/knock.

Once in closed loop, the ECM uses the MAF and front O2s to adjust fuel. So I would look to something up in those, or the tune as the culprit. It should be able to handle way more than 18 deg timing.

I'd use the stock plugs and whatever fuel over there is closest to 93. After verifying the MAF is reading correctly, and the O2s are active/cross counts, using a proper air filter. Those air filter pleats are critical to having a correct MAF reading. With a known good air filter in, can also just unplug the MAF temporarily. The engine will run on a set speed density cal and ignore the MAF. If it runs great with the MAF unplugged, something is up with either the MAF or filter.

Also, what did you do or change right before it started knocking? I believe in the - you touched it theory. If you messed with something and now things aren't right, reverse what you messed with.

[BAH2SS]

Originally Posted by Moto-Mojo

You guys are way ahead of my skills and mods but I haven’t heard an ignition knock since I fixed one in my mother’s 1975 Cutlass...in 1978. I though that’s what knock sensors were for? Did they get tuned out?

They are working and doing their job that last knock it didn't detected

Originally Posted by Russell James

What brand of air filter? And I wouldn't run it without an air filter. The air filter pleats are there to create laminar air flow across the MAF. Without laminar air flow across the MAF - ie either a stock air filter or a properly engineered aftermarket one, the MAF reading will be all over the place from turbulence.

Take a close look at the MAF sensor, pulled out of the intake. Make sure there are no fuzzy fibers burned on the hot wire element. That can cause a lean condition/knock.

Once in closed loop, the ECM uses the MAF and front O2s to adjust fuel. So I would look to something up in those, or the tune as the culprit. It should be able to handle way more than 18 deg timing.

I'd use the stock plugs and whatever fuel over there is closest to 93. After verifying the MAF is reading correctly, and the O2s are active/cross counts, using a proper air filter. Those air filter pleats are critical to having a correct MAF reading. With a known good air filter in, can also just unplug the MAF temporarily. The engine will run on a set speed density cal and ignore the MAF. If it runs great with the MAF unplugged, something is up with either the MAF or filter.

Stock air filter, removed it on the Dyno for test purpose only. The MAF was checked and found clean no issues with the MAF. After the cat delete the O2 sensors are also doing their job. I'll buy a drop in K&N filter and see what happens. I am guessing it's one of those engines that don't like timing. On the dyno on 20 degree it made 394 and in 18 degrees it made 404. That alone is confusing.
I will however disconnect the MAF and see what happens. But for speed density I'll have to tune it and go for a MAF less tune so it could run properly.

[G8One2]

I'd start checking heat range on your plugs. May need to go a step colder.

[BAH2SS]

Attached is Dyno sheet last two runs without air filter

399 with 19 degrees of timing
403 with 18 degrees of timing.

Why!!
I know for a fact the increasing timing will gain top end and lose low end power.

We are decreasing timing and gaining low and top end !!!.

Is it really one of those engines!

[BAH2SS]

Originally Posted by G8One2

I'd start checking heat range on your plugs. May need to go a step colder.

I am already at a step colder. Went from 41-110 to 41-104 which is equivalent to TR6

[gtstorey]

Originally Posted by BAH2SS

We are using MON and i am working in Bahrain petroleum company lol. So i am 110% positive that our fuel is goof

95 MON is about 100 in US so I would think you have major problems if you are getting that to knock.

[BAH2SS]

Originally Posted by gtstorey

95 MON is about 100 in US so I would think you have major problems if you are getting that to knock.

Wait wait, i apologize we are RON not MON i got confused, I just checked the lab results and they are using RON

[Greenhornet2]

95 RON is probably a bit too low octane. Since you are fooling around you might pull even more timing and see if it changes the knock, I am thinking you have something physically making noise and the knock sensors are picking it up and it is not a true ignition knock. I do know there is also a way to reduce sensitivity of them but if you are actually hearing a knock then I wouldn't mess with that.