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Barra Phantom Knock


Dolan
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Hey,

I've been tuning spark on my FGX XR6 Turbo and my knock ears are showing some sort of 'phantom knock' on E85.

I've done 2 runs, one with 0deg timing at 17 psi boost (around 2.15 on the spark load) around 5k rpm and it sounds like its knocking but I'm pretty sure its not.

What sort of timing is everyone else running around that load and rpm level, that'd help me figure out about where knock starts.

I'm just going to have to drive the car easy until I figure out what's going on.

Thanks, Dylan

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You are gonna cook your setup running 0 degrees of timing, don't do that.

On E85 at 17psi you'll find your max power is close to 18 degrees of timing but you need to verify it on the dyno.

I run 18.5 degrees on E85 making a touch over 700awkw at 31psi. This is a built motor obviously.

Don't go crazy with timing, you can't just add more to make more power, it doesn't work like that. It'll stop making power before it knocks but it will stress the motor a lot more if you keep adding timing. It'll chuck the rods out if you go there. 

Maybe go back to 12psi and start from there, as it'll pull a lot harder than it is now with the correct timing in it.

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Posted (edited)

Yeah I thought it might not have been good at that timing so I stopped and asked 😁

I’ll have a look tomorrow at my knock setup, I’ll try moving the sensor and tuning it and my ears.

Thanks for the help!

Also, around the hat afr are you running? I’m running around 0.8 lambda on E85 and 98, but I’ve heard it’s okay to go a bit leaner for E85. I’ve been scared to lean it out any more so I’ve just kept it there for a bit of safety.

Edited by Dolan
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8 hours ago, Puffwagon said:

You are gonna cook your setup running 0 degrees of timing, don't do that.

On E85 at 17psi you'll find your max power is close to 18 degrees of timing but you need to verify it on the dyno.

I run 18.5 degrees on E85 making a touch over 700awkw at 31psi. This is a built motor obviously.

Don't go crazy with timing, you can't just add more to make more power, it doesn't work like that. It'll stop making power before it knocks but it will stress the motor a lot more if you keep adding timing. It'll chuck the rods out if you go there. 

Maybe go back to 12psi and start from there, as it'll pull a lot harder than it is now with the correct timing in it.

 

awkw? please tell me its in a territory :) 

 

as to your timing dolan, i try to stay above 5deg, egts will get too much and you'll melt something. what puffwagon said is spot on. 

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What does the factory knock system show? Does it correlate with the knock ears?

Could you be getting noise externally from somewhere else?

Do the knock ears have filtering built in or are they just a microphone? If you can turn the filtering off can you post an audio clip up?

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The factory knock system shows knock on the SPK_ADD_LIM param but not on the SPKAD_IND_AVG param.

I'd say so, I've got the bosch knock sensor for my knockears bolted as shown in the picture attached, its probably too far down to get a good reading.

They have filtering, but it can be turned off. I'll post up a clip tonight or tomorrow.

Thanks!

lead-image-1152009-1584486845.jpg

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18 hours ago, Dolan said:

Yeah I thought it might not have been good at that timing so I stopped and asked 😁

I’ll have a look tomorrow at my knock setup, I’ll try moving the sensor and tuning it and my ears.

Thanks for the help!

Also, around the hat afr are you running? I’m running around 0.8 lambda on E85 and 98, but I’ve heard it’s okay to go a bit leaner for E85. I’ve been scared to lean it out any more so I’ve just kept it there for a bit of safety.

Just use your stock timing map and switch off the knock sensors for a good starting point for E85 tuning. When you want to add timing you just highlight 1.0 load to max load at every rpm point and add it there. This makes it easy to remember and also is where it starts getting into boost. Start with a couple of degrees and see how that goes.

As far as afr goes you can go plenty lean if you want. I usually aim for 0.82 to 0.84 lambda on E85 as it makes a fair bit more power there than running it at 0.8 lambda. It really depends on how you drive and the weather conditions etc. For a quick hit every now and then in the cooler months, run it leaner cos it'll be fine. Middle of summer and doing a circuit day, you'll want to have it at 0.8 or so to help it cool down. Even if you're tuning and see it go to 13:1 it'll be completely fine to stay in it to log the run, and then add a bit of fuel afterwards. You'll see it lose power on the dyno if you lean it out too much, but that is usually mid 13's so it's clear that more fuel is needed to keep things happy power wise, and also happy heat wise for the engine internals etc.

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1 hour ago, Puffwagon said:

Just use your stock timing map and switch off the knock sensors for a good starting point for E85 tuning. When you want to add timing you just highlight 1.0 load to max load at every rpm point and add it there. This makes it easy to remember and also is where it starts getting into boost. Start with a couple of degrees and see how that goes.

Ill give that a go now and work from there

1 hour ago, Puffwagon said:

As far as afr goes you can go plenty lean if you want. I usually aim for 0.82 to 0.84 lambda on E85 as it makes a fair bit more power there than running it at 0.8 lambda. It really depends on how you drive and the weather conditions etc. For a quick hit every now and then in the cooler months, run it leaner cos it'll be fine. Middle of summer and doing a circuit day, you'll want to have it at 0.8 or so to help it cool down. Even if you're tuning and see it go to 13:1 it'll be completely fine to stay in it to log the run, and then add a bit of fuel afterwards. You'll see it lose power on the dyno if you lean it out too much, but that is usually mid 13's so it's clear that more fuel is needed to keep things happy power wise, and also happy heat wise for the engine internals etc.

Okay cool, I'll lean it out a little and aim for 0.84, thanks for the advice!

 

5 hours ago, Roland@pcmtec said:

If you can turn the filtering off can you post an audio clip up?

I've attached the log file and the raw audio

24-05-2021 08-18-38 PM Log.zip

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16 hours ago, Dolan said:

I've attached the log file and the raw audio

Just a heads up, your data log is doing the 'show only every 50ms' bug when you save from opening a saved teclog file.  You may need to update your version if not currently using the newest version.

Also your logging spark mod vct, not sure if you're intending total final spark. i cant remember the tag off the top off my head for it.

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3 minutes ago, finnigan001 said:

Just a heads up, your data log is doing the 'show only every 50ms' bug when you save from opening a saved teclog file.  You may need to update your version if not currently using the newest version.

I'm not sure if that is fixed in 1.25. It might have only been fixed in 2.00 which is not released yet.

The work around is to just use teclog format only.

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4 minutes ago, finnigan001 said:

Just a heads up, your data log is doing the 'show only every 50ms' bug when you save from opening a saved teclog file.  You may need to update your version if not currently using the newest version.

That's weird cause I saved to csv directly after logging... I'm on 1.25. Didn't even know that was an issue.

5 minutes ago, finnigan001 said:

Also your logging spark mod vct, not sure if you're intending total final spark. i cant remember the tag off the top off my head for it.

I'm logging SAFTOT, I think that's the final spark timing? I'm probably wrong though.

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