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High RPM Knock at WOT

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VoodooXTC

Probationary Member
9
0
Jan 10, 2009
Carpentersville, Illinois
I can't figure out why I'm getting knock at higher rpms at WOT. Below is a 2nd and 3rd gear pull from a log done this morning. I don't see knock in 1st just 2nd and beyond.

I originally thought it was a spark problem so I switched to bpr7 gapped to 30 and a set of Taylor wires with no change. I tried using 100 octane which didn't help either. The car pulls hard and I don't feel any hesitation when the knock starts.

My current mods are: Big 16g@ 15psi, 2.5" turbo back exhaust, FMIC, 3" GM MAF w/MAF-T, AEM UEGO, Walbro 255, Aeromotive AFPR, boost gauge and SAFC-II.

Any help would be much appreciated.

Timing AFR TPS MAF RPM Knock
20.00, 10.41, 100.00, 1603.95, 5343.75, 2.00
19.00, 10.24, 100.00, 1603.95, 5312.50, 6.00
18.00, 10.29, 100.00, 1603.95, 5406.25, 6.00
17.00, 9.94, 100.00, 1603.95, 5687.50, 9.00
18.00, 10.06, 100.00, 1603.95, 5687.50, 16.00
15.00, 9.82, 100.00, 1603.95, 5968.75, 16.00
16.00, 9.71, 100.00, 1603.95, 6000.00, 16.00
16.00, 9.76, 100.00, 1603.95, 6125.00, 16.00
15.00, 9.82, 100.00, 1603.95, 6062.50, 15.00
16.00, 10, 100.00, 1603.95, 6281.25, 16.00
14.00, 10.41, 100.00, 1603.95, 6375.00, 22.00
12.00, 10.82, 100.00, 1603.95, 6406.25, 21.00
12.00, 10.82, 100.00, 1603.95, 6500.00, 25.00
11.00, 10.88, 100.00, 1603.95, 6718.75, 24.00
10.00, 11.19, 100.00, 1603.95, 6687.50, 25.00
8.00, 11.24, 100.00, 1603.95, 6750.00, 25.00
9.00, 10.82, 23.14, 1308.32, 7343.75, 24.00
35.00, 9.53, 11.76, 150.96, 6656.25, 4.00
45.00, 11.66, 100.00, 1283.16, 6343.75, 0.00
26.00, 12.12, 100.00, 1434.12, 5281.25, 0.00
19.00, 10.06, 100.00, 1515.89, 5187.50, 2.00
21.00, 10.29, 100.00, 1553.63, 5312.50, 8.00
17.00, 10.29, 100.00, 1603.95, 5343.75, 8.00
16.00, 10.12, 100.00, 1603.95, 5281.25, 7.00
17.00, 9.88, 100.00, 1603.95, 5437.50, 14.00
16.00, 10.06, 100.00, 1603.95, 5562.50, 14.00
16.00, 9.94, 100.00, 1603.95, 5437.50, 13.00
16.00, 9.59, 100.00, 1603.95, 5593.75, 20.00
14.00, 9.59, 100.00, 1603.95, 5562.50, 20.00
14.00, 9.35, 100.00, 1603.95, 5750.00, 20.00
14.00, 9.59, 100.00, 1603.95, 5687.50, 20.00
14.00, 9.35, 100.00, 1603.95, 5687.50, 19.00
15.00, 9.41, 55.69, 1603.95, 6281.25, 19.00
17.00, 9.53, 11.76, 176.12, 6156.25, 1.00
45.00, 11.53, 11.37, 106.93, 5531.25, 0.00
 
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Yeah looks a little lean. Adjust the AFR's and try again, hope you aren't on stock injectors...
 
Upvote0
9.5 is lean? You guys mean rich right? The higher the number the leaner the AFR.
 
Upvote0
Even with all the timing being retarded you dont feel anything at all? No loss of power? You're running pig rich too.
 
Upvote0
Well, I have never heard of "rich knock". Knock is also known as "ping", also known as pre-detonation. Whatever you want to call it, it is caused by the air/fuel mixture igniting before it is supposed to, causing the piston/rod assembly to be shoved downwards. If this occurs before about 10 degrees BTDC, it can blow a hole through the piston or destroy the piston 'lands'. The 4g63 knock sensor is at best a useless piece of overly sensitive crap and cannot be relied upon. Many 4g63 enthusiasts come to realize that increased engine noise at high rpm are picked up by the knock sensor and the ecu interprets this data as "knock" when in fact it is not.
So I ask you, how do you know it is "pre-detonation"?
 
Upvote0
TOONAH said:
Well, I have never heard of "rich knock". Knock is also known as "ping", also known as pre-detonation. Whatever you want to call it, it is caused by the air/fuel mixture igniting before it is supposed to, causing the piston/rod assembly to be shoved downwards. If this occurs before about 10 degrees BTDC, it can blow a hole through the piston or destroy the piston 'lands'. The 4g63 knock sensor is at best a useless piece of overly sensitive crap and cannot be relied upon. Many 4g63 enthusiasts come to realize that increased engine noise at high rpm are picked up by the knock sensor and the ecu interprets this data as "knock" when in fact it is not.
So I ask you, how do you know it is "pre-detonation"?
Click to expand...

That's exactly what I was thinking. If it was pre-detonation, putting 100 octane in would've helped but didn't. I am gonna work on getting the AFR closer to 11-11.2. Very time and gas consuming. Lol
 
Upvote0
OH there is definitely such a thing as RICH KNOCK. Not to mention you are likely getting "BORE WASH" meaning you are flooding you cylinders with fuel. That Over excess of fuel gets in your oil and thins it out. Eventually leading to premature bearing wear. LEAN it out some and see if the knock goes away.
 
Upvote0
mheidemanjr said:
ooops my bad rich is what i was trying to say!
Click to expand...

The 9.5 - 21.8 number is referring to the Parts of AIR per parts of fuel being burnt. So if the wideband reads 14.7 that means there are 14.7 pounds of AIR to every pound of fuel. At this ratio, theoretically, all available oxygen in the air
combines with all available fuel. This ratio is called stoichiometric ratio. Anything under 10.5 at WOT is too rich IMO for Gasoline.

Race gas you can usually lean out to around 12.1 or so at WOT thanks to its Higher octane resistance to knock.

For the OP I would look for AFR's around 11.2 - 11.5 at WOT and I bet you will see most of that knock go away!

I would also recommend changing your Engine oil and filter. With your car running that rich I'm willing to bet that your oil is saturated with fuel rendering it useless. So swap it out for some fresh oil if you want to save your engines life.
 
Upvote0
Jeff99GS said:
The 9.5 - 21.8 number is referring to the Parts of AIR per parts of fuel being burnt. So if the wideband reads 14.7 that means there are 14.7 pounds of AIR to every pound of fuel. At this ratio, theoretically, all available oxygen in the air
combines with all available fuel. This ratio is called stoichiometric ratio. Anything under 10.5 at WOT is too rich IMO for Gasoline.

Race gas you can usually lean out to around 12.1 or so at WOT thanks to its Higher octane resistance to knock.

For the OP I would look for AFR's around 11.2 - 11.5 at WOT and I bet you will see most of that knock go away!

I would also recommend changing your Engine oil and filter. With your car running that rich I'm willing to bet that your oil is saturated with fuel rendering it useless. So swap it out for some fresh oil if you want to save your engines life.
Click to expand...

I didn't think about cylinder wash, thank you for reminding me!!!
 
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