Knock Knock Knock

[Lakegoat]

Last little pull that I did in my backyard had some pretty good knock. 10 degrees. It had been showing about 4.5 degrees, but this last run was A LOT ! Engine is all forged 5.3 with a Whipple, open exhaust---about 40" past the exhaust manifolds with 11" dirt track mufflers. Wideband was showing about 2% rich in that area. Runs great, but I would like to get rid of that knock if it is real. The exhaust isn't hitting anything, but it is dam noisy.
I richened up the 112 kpa cell that shows 11% lean---blip in the VE table. Fuel pressure is increasing with boost.
Any ideas? Thanks

[GHuggins]

Are you sure your wideband is reading right? I'm just looking at your O2's and I'm seeing near 100 mv with the eq error still showing 1 to 2 % rich. Only time I had this bite me before it was because of the wideband reading 1 full point off. Might be worth checking or even throwing another one in for peace of mind. 300 is a lot cheaper than lifting the heads. O2's are showing 880mv when it was showing all of the knock. That seems more like a high 12 afr than a high 11's. You can even command it 10% richer to see if anything changes.

[Lakegoat]

I have another wideband. I will swap it and see if it is different. I didn't know to check the O2 mv.
How does 880 mv relate to high 12 afr?
Thanks!

[Lakegoat]

Changed out the wideband--(calibrated it). I only got a blip of the throttle to 6400 and it showed 15% rich. Only one cell. I didn't want to hold the pedal down and hurt it.
Still had 4 degrees of knock. O2's were at about 930mv. It's running 93 pump octane. Is the boost high enough to need a better fuel? Do you think this wideband is working correctly?
Thanks

[ns158sl]

That seems uber rich. Id also be curious what your manifold intake temps are. Does whipple have a spot in the manifold to put a sensor? 14ish lbs is probably a little much for pump gas depending on the blower outlet temps.

[edcmat-l1]

What's the compression ratio? What spark plugs are you running? How new is the engine?

[edcmat-l1]

KS initial threshold.jpg

Your knock sensor initial threshold has been lowered, which increases the sensitivity. I'd put that back to stock (120) and see if it makes any difference.

With a forged piston engine, if I was confident in the build, top ring gap, etc. I'd have no problem desensitizing the sensors somewhat. But you need to know the compression so you know how much timing should be appropriate. A dyno would be really helpful here.

[Lakegoat]

That seems uber rich. Id also be curious what your manifold intake temps are. Does whipple have a spot in the manifold to put a sensor? 14ish lbs is probably a little much for pump gas depending on the blower outlet temps.

Iat's are in the channels. I think it was about 90 degrees where it was knockkin'

[Lakegoat]

Compression is 10.7:1
Spark plugs are NGK Iridium #7 heat range---Gen V heads.
Engine is new ---only about 15 miles on it. Ring gaps are .026 as recommended by Diamond.
I will change the knock sensor threshold back to stock. Is 140.000 too much to desensitize?
Thanks

[ns158sl]

Is the sensor pre or post blower? That is a lot of compression. Im surprised it doesnt ping sooner lol.

[Lakegoat]

Since the two widebands do not agree, I am concerned that this is not going to be right. The only time the widebands are used is when I am tuning my car. They don't stay in the exhaust every day.

[Lakegoat]

Iat is in the blower lower housing. Post blower.
Thanks

[edcmat-l1]

I prefer non projected tip plugs. BR7EF for that thing. That's what I would put in it.

[Lakegoat]

Is the sensor pre or post blower? That is a lot of compression. Im surprised it doesnt ping sooner lol.

I had a LS3 that was 10.9 compression with a Magnuson at about 12psi and never had a knock problem. The spark table for this engine is the same one that I used for that setup.

[Lakegoat]

I prefer non projected tip plugs. BR7EF for that thing. That's what I would put in it.

That's what I used before---your recommendation. These Gen 5 heads take a lot longer plug. I don't know how that short plug would work out??

[ns158sl]

Oh wow. I was surprised the IAT didnt jump after getting into decent boost. Did you try to get the AFR closer to commanded and then pull a bunch of timing out just to see what happens?. Kind of getting sidetracked, but what cam are you running? I can barely get 17 degrees of timing out of a N/A 10.8 ls3 before it starts losing torque, lol.

[Lakegoat]

I prefer non projected tip plugs. BR7EF for that thing. That's what I would put in it.

I thought I replied?? Don't know where it went
The Gen 5 heads use a longer plug. Would the shorter BR7's work?

[edcmat-l1]

I thought I replied?? Don't know where it went
The Gen 5 heads use a longer plug. Would the shorter BR7's work?

No, they won't work in a GEN5 head. You need some Brisk plugs for those. Brisk Sliver Racing I think they're 14s you need.

[Lakegoat]

Oh wow. I was surprised the IAT didnt jump after getting into decent boost. Did you try to get the AFR closer to commanded and then pull a bunch of timing out just to see what happens?. Kind of getting sidetracked, but what cam are you running? I can barely get 17 degrees of timing out of a N/A 10.8 ls3 before it starts losing torque, lol.

Cam is CamMotion 230/248, LSA 115.5, Timing 4.5 advance, Intake CL 111.0, Exhaust CL 120.0, .631/.629 lift @1.8, Overlap 8.6
IAT's will get up to 127 with a longer pull.
First post shows closer afr's, but wideband is not reading right compared to the second log with another wideband.
Now I am just head scratching.

[Lakegoat]

No, they won't work in a GEN5 head. You need some Brisk plugs for those. Brisk Sliver Racing I think they're 14s you need.

I changed the knock sensor number to 129.. Bad thing is, I don't know if the wideband is correct, so I can't adjust anything til I get a new one. Crap!! I will check to see if the knock goes away but it will still be rich or lean--- who knows. What is a good wideband that doesn't break the bank.