Technical Ignition advance on E85

veer90

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How much should I run? Gonna take a stab at tuning the car myself.

Most logs I've reviewed from others with my setup (Doc Race / gen2 precision 6266 on full E85) have timing around 10* up top, but that's on a stock motor. I have a built bottom end and JE pistons with beefy ringlands and rings gapped for high boost, so I'd like to push it (safely). Current BMS BEF is at ~7*, car feels quick to me but the other day I got mopped by a GTR so definitely time to crank it up lol

I've always read that for E85, the proper way to tune timing is to hit the dyno. Increase timing until you go past MBT then run the timing at which MBT was achieved.

Any danger of knock / pre-ignition if I try that at 30 psi?
 
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colo_evo

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You're on the right track.

Most people advance until no more power is achieved then back off a degree or two.

You'll want to disable knock sensors on the dyno so they don't hold you back. Re-enable them when you get done on the dyno.

Post up graphs when you're done.
 

veer90

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You're on the right track.

Most people advance until no more power is achieved then back off a degree or two.

You'll want to disable knock sensors on the dyno so they don't hold you back. Re-enable them when you get done on the dyno.

Post up graphs when you're done.

Isn't disabling knock sensors dangerous? Or does that only apply for pump gas?

Last thing I want to do is grenade my built motor lmao
 

bahn

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Do not disable the knock feedback system. The proper way to do this is to start low on timing and work your way up until you either hit MBT or you start seeing a large amount of timing corrections. I would highly recommend audio knock detection headphones (really just headphones with an amplifier connected inline with the knock sensors). I would recommend a set of noise canceling headphones as well since Dyno bays are loud by nature. You can then hear actual knock in your ears during a pull and if needed adjust your knock sensitivity tables to eliminate false positive knock. Once you find MBT or your knock threshold, take 2 degrees out for safety margin.
 
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colo_evo

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Isn't disabling knock sensors dangerous? Or does that only apply for pump gas?

Last thing I want to do is grenade my built motor lmao


Only for the dyno. On a built engine single turbo stock kr settings will pick up false knock and get in the way.

You'll likely need to dial back in the knock sensors on the street when you determine mbt on the dyno.
 

doublespaces

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Do not disable the knock feedback system. The proper way to do this is to start low on timing and work your way up until you either hit MBT or you start seeing a large amount of timing corrections. I would highly recommend audio knock detection headphones (really just headphones with an amplifier connected inline with the knock sensors). I would recommend a set of noise canceling headphones as well since Dyno bays are loud by nature. You can then hear actual knock in your ears during a pull and if needed adjust your knock sensitivity tables to eliminate false positive knock. Once you find MBT or your knock threshold, take 2 degrees out for safety margin.

Is this still common practice on modern engines?
 

veer90

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Only for the dyno. On a built engine single turbo stock kr settings will pick up false knock and get in the way.

You'll likely need to dial back in the knock sensors on the street when you determine mbt on the dyno.

I'm on factory knock tables but have already desensitized the knock sensors on the hardware side (trim pots wired in at 70k ohms). @V8bait Justin figured out my motor was false knocking when he was tuning it with upgraded twins; it couldn't be tuned out so I had to resort to a hardware solution.

I could turn it up all the way to 100k ohms (maximum signal dampening) but I'm not sure how safe that would be, lol

Is this still common practice on modern engines?

I'm not an expert but I feel like sometimes the factory knock systems are excellent, and sometimes they get in the way (depending on your hardware). But disabling it altogether without any testing seems sketch.
 

bahn

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Is this still common practice on modern engines?
Yes, especially when using aftermarket flywheels as most of the time you'll have to reduce the knock sensitivity or eliminate the frequency. Headphones work well and so does an oscilloscope. The knock sensors are just piezo microphones.

Edit: I should say I haven't seen anyone else in the N54 crowd doing this, but it is still standard practice and should be used more often.
 
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veer90

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On a real development car we use combustion analysis software and cylinder pressure sensors.

On backyard projects like this, yes, tuning on the dyno watching torque is just fine.

So what you're saying is, the knock threshold for E85 is so high that a stock compression N54 at 30 psi of boost should be nowhere near it? Please correct me if I'm wrong.
 

veer90

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How did v8bait figure out that it was false knock?

Low boost / low timing map on full e85, then compared timing corrections in 2nd gear, 3rd gear, and 4th gear WOT pulls.

It was pulling timing badly and consistently across all gears (on a super conservative map on E85) which meant false knock.
 

colo_evo

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So what you're saying is, the knock threshold for E85 is so high that a stock compression N54 at 30 psi of boost should be nowhere near it? Please correct me if I'm wrong.

No, the knock sensors are calibrated for a stock engine with stock ptw clearance and low boost to last 100k+ miles. Your setup is entirely different and needs adjusted for your changes.
 

langsbr

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There was a thread on a different forum where some guys were running 18* of advance on stock turbos. I'd have to hunt for it, but I believe he was still making power. I swear I read somewhere that MBT was around 21 degrees on these, which seems crazy high considering the most I've seen from fast cars is in the 12 - 13 range, and people see timing corrections even at 10 or less.

Wasn't Doug running 20+ on his setup with meth? Definitely ragged edge on a stock motor, but if it makes power there, and you have the octane, what is the harm? Why would you not run the most you safely can?
 
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colo_evo

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For what it's worth I tune many other boosted e85 platforms(all port injection) to 15-25 degrees advance.

N54 is by far is the lowest timing advance of anything I've seen.
 

bahn

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There is this tool that most N54 tuners aren't familiar with. It's called a dyno and it's great for finding MBT. Or you can pay one of the "pros" on here to ride your knock sensors on an e-tune lol
This, so many etuners on this platform.
 

veer90

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There was a thread on a different forum where some guys were running 18* of advance on stock turbos. I'd have to hunt for it, but I believe he was still making power. I swear I read somewhere that MBT was around 21 degrees on these, which seems crazy high considering the most I've seen from fast cars is in the 12 - 13 range, and people see timing corrections even at 10 or less.

Wasn't Doug running 20+ on his setup with meth? Definitely ragged edge on a stock motor, but if it makes power there, and you have the octane, what is the harm? Why would you not run the most you safely can?

That's nuts.

I definitely have the octane, my concern is desensitized knock sensors and HIGH boost (whatever the 6266 will do, idgaf) and how close that puts me to the E85 knock threshold, which no one seems to know.

For what it's worth I tune many other boosted e85 platforms(all port injection) to 15-25 degrees advance.

N54 is by far is the lowest timing advance of anything I've seen.

I've only seen it once but Jake H. mentioned that timing values for same ballpark power tuning the factory DME vs. tuning a standalone are significantly different. There may already be an offset in the factory DME initially before it applies whatever you put in the timing table. Just a hunch, and doesn't matter much to me for my purposes

I'll most likely be hitting the dyno with trim pots cranked all the way up to 100k ohms and some DIY det cans.
 
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