Getting ready for BG and now knock at WOT

[huntsg]

Two days ago I was driving around town and got on it for a few seconds from a light. Pushed the recall on the scan master and saw exactly 15.0 degrees of Kr. I've had knock on shifts before but never that high. Put the car away for the night thinking/hoping it was from a shift. Then today I rolled into it at about 25 mph and checked the scan master and once again saw exactly 15.0 degrees of Kr. So I hooked up the laptop and recorded the attached file. It was from about a 40 mph roll and the scan master read exactly 15.0 degrees of Kr. Three times at exactly 15.0 degrees on the scan master. Is that weird? Needless to say, there is something going on. Both my NB and WB readings look good. The injector DC is maxed. Any ideas? Thanks.

 

[we4Mateo]

Hmmm, you're not seeing it happen? Is it on the shift?

 

[huntsg]

Right when the Kr starts in the log, the check box for 3rd gear becomes unchecked as it down shifts to 2nd. So yes it starts knocking right at the downshift, but in the past it was less Kr at the shift and it "spiked". As you can see on the graph this Kr is kind of flat lined at 15 degrees. Once it shifts back into 3rd the Kr starts to go back down.

 

[huntsg]

Here is a screen shot with the Kr in case you don't have a power logger.

 

[Pronto]

Does it happen with normal WOT upshifts?

 

[huntsg]

Do you mean from a stop and then go WOT? It hasn't in the past other than at shift points. This was throughput 2nd gear??

 

[huntsg]

I think I'll go slow wot at around 60 mph so it doesn't downshift and see what happens.

 

[Pronto]

Review your SD2 chip setting to make sure nothing has changed as well

 

[Eric Stage I]

It's flatlined because that is the max retard in that chip.
Are you sure your alky didn't stop spraying? Is your duty cycle normally that high?
Turn the boost down and see if it goes away.

 

[huntsg]

Ok. I did not realize the chip had a limit. Will try that. The test button works on the Alky kit. My duty cycle has been in the upper 80s previously. Even if the Alky wasn't spraying my AFR is around 10.3.

 

[Eric Stage I]

The test button doesn't tell us if you are spraying enough alcohol.

An AFR of 10.3 can't make up for the octane/cooling that the alcohol provides.

 

[OneQuikSix]

At first glance, this looks like an octane/alky issue to me. It almost appears the alky didn't arrive fast enough and then gradually caught up to the timing and boost you were running...hence the gradual decrease in knock (even though you kept your foot in the throttle). As stated earlier, the stock ECM can only retard timing 15 degrees max upon sensing detonation. Assuming your knock sensor is working properly, you definitely exceeded that threshold I would guess by quite a bit.

 

[OneQuikSix]

Another note, I too run an SD chip from Eric. Despite mixed opinions on where to mount the IAT sensor, I have installed mine after the alkycontrol nozzle for two reasons. One, temperature of the incoming air charge is directly related to charge density; so I figure the chip will do a better job adjusting for the amount of air entering the intake if it knows the true temperature. Second, I like to monitor the IAT's before and during a WOT blast to see how cold things are getting. To me, this is especially important in the cooler months to avoid spraying too much alcohol. In your case, it would help you see how fast the alcohol is coming in relative to boost. I like to see the IAT's begin to drop a few pounds prior to where knock would occur without the alcohol. Just a thought...

 

[huntsg]

Another note, I too run an SD chip from Eric. Despite mixed opinions on where to mount the IAT sensor, I have installed mine after the alkycontrol nozzle for two reasons. One, temperature of the incoming air charge is directly related to charge density; so I figure the chip will do a better job adjusting for the amount of air entering the intake if it knows the true temperature. Second, I like to monitor the IAT's before and during a WOT blast to see how cold things are getting. To me, this is especially important in the cooler months to avoid spraying too much alcohol. In your case, it would help you see how fast the alcohol is coming in relative to boost. I like to see the IAT's begin to drop a few pounds prior to where knock would occur without the alcohol. Just a thought...

Seems like a good thought. My IAT sensor is in the up pipe before the Alky nozzle.

 

[huntsg]

The test button doesn't tell us if you are spraying enough alcohol.

An AFR of 10.3 can't make up for the octane/cooling that the alcohol provides.

I have a second nozzle I could add to spray more.

 

[Lil Truck]

How old is your Alky pump? You may have a leaking pump under pressure? Do you smell a sweet odor during boost...? That is the smell I had when my pump was leaking. If your octane is low it will knock hard!!!

 

[huntsg]

It's a pretty new pump. No more than 6 months old. I replaced my old one with this one but I I also have my rebuilt old one on the shelf. No sweet smell and I'm pretty sure it's not leaking.

 

[salvageV6]

I'd check your mechanical stuff and motor mounts.

That amount should be audible if real do you hear the pinging?

 

[Lil Truck]

It's a pretty new pump. No more than 6 months old. I replaced my old one with this one but I I also have my rebuilt old one on the shelf. No sweet smell and I'm pretty sure it's not leaking.

If your running the same boost level, alky settings and your injector DC is maxed you have a alky problem....... blocked filter? What octane are you running ?

 

[huntsg]

93 octane. Boost is maybe 3 lbs higher than I had it at this Alky setting. Alky dial is just shy of 6. I haven't heard any audible knock but it's quick and the windows are open. I need to get a passenger for more eyes and ears.