Please help knock

[xrunner123]

Can someone review these powerlogger files? I'm going to give up....

I have knock on the instant of boost with the first gear being the worst. I assume this is false? I had fueling issues which I've resolved and I recently added Alky so I can run more boost but now I get knock. It was fine at 16-17lbs but I guess more power is doing it??? I'm at around 20lbs now.

Downpipe is not banging and I have HR motor mounts. I've replaced the knock sensor and made sure it's not torqued down tight. What else can cause such bad knock?

I'm logging PLX wideband and fuel pressure on analog 4

Thanks so much.

 

[Raeban]

I looked through alk4 log and didn't see anything that jumped out at me as drastically out of whack. It did look like you had a couple knock events during the KR around frame 1118 and your bat voltage at the Scanmaster at WOT is lower than what would make me comfortable. Have you tried a third gear soft roll into WOT?

 

[SCOOBY DOO]

Your low battery voltage coincides with your KR.

 

[xrunner123]

That's interesting. Why would it knock at the lower voltage? Is this definitely false?
And how do I increase this? Alternator or new battery or both?
Thanks

 

[87-WE2]

Lowered voltage would reduce the output of the fuel pump. Reduced fuel pump output = KR = KABOOM!!!!


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[SCOOBY DOO]

Take a reading from the back of the alternator with the engine running. Throw everything on...AC...high beams...blower on high...and see what you get for voltage.

 

[aminga]

In the file fromastop I see the vehicle speed as zero but the third gear switch is on.

 

[Raeban]

Here is a SS of the log for those that can't view it. Looks like fuel pressure rises even with the voltage going low so I'm not sure its a fuel supply issue?

 

[xrunner123]

Lowered voltage would reduce the output of the fuel pump. Reduced fuel pump output = KR = KABOOM!!!!
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Yes but I'm not running lean. Wideband shows this and my fuel pressure is in line.

 

[big steves gn]

I had this problem before it was my alternator and still having this problem every once in awhile the car runs fine with over 13 volts as soon as it goes to 12.8 12.7 I start getting knock over 16 psi

 

[GNRick]

I have an Interstate battery about 3 years old. Added water to it today and voltage seems to be a bit higher on my volts gauge.

 

[Turbo6Smackdown]

I have the same problem. Wide band says ok, but still getting knock. I should look at my battery as well.

 

[VtheGNMan]

Would one of those Casper's Volt boosters work good in this case? I don't know much about them so I am asking as much as anything on this one. If they work as they say they do, it seems like having one is a little insurance against low voltage.

 

[Turbo6Smackdown]

They're band aids. Something's not right. Wiring loose, or improper diameter, corrosion somewhere causing the resistance, pumps wore out, faulty connections etc. I'd fix the problem before using a volt booster.

 

[xrunner123]

I'm going to try a new battery and/or a new alternator and recheck all my grounds.

 

[earlbrown]

Check all your positives too

 

[xrunner123]

Where does the ECM measures battery voltage? ECM power wire?

 

[earlbrown]

Yes, relative to the ground wire. Don't forget, a circuit is a loop.

 

[Eric Stage I]

The voltage reading comes from the ignition switch input to the ECM.

 

[dynoman]

You say you recently added alky , maybe you just have to dial it in a little better. You get KR right at the beginning of max boost then no more, also like Scooby Doo said check your voltage at the alternator , if it's not over 13v you won't even charge the battery.