Knock Sensor Gain - 2015 Mustang

[Kryckter]

I have a 2015 Mustang, twin turbo on E85.

I had the car dialed in on 12lbs of boost on E85 with no knock and about 19 degrees of timing. It did 806/786 on this setup. I changed exhaust to the Magnaflow street setup and had a custom H-Pipe built. Ever since then I have been getting knock like crazy. I assumed its a loose clamp or the exhaust hitting the body. I have searched and searched and re-checked every clamp and fitting. All is good.

I assume it has to be false knock, even on about 8 lbs of boost and 16 degrees of timing it will pull full knock retard at 4k. The E85 tests great, almost a little high near E90 and AFR is mid 11's on the gauge or .77/.78 lambda. The upstream widebands read .72/.73.

I assume its false knock, I tried de-sensitizing the knock sensors in the gain table. I dont want to turn them off, just reduce them by 25%-50% to test.

Are the numbers on the table backwards? If I divide that number in half it gets WAY worse knock. But for testing purposes I doubled those numbers in the table and get 0 knock. Thoughts?

[redline5.0]

How close are the headers to the frame rail or steering shaft? Also the collector claps are they close to anything? What I'm getting at is when you start torquing the motor something must be hitting or rubbing something. I've saw bolts rubbing in places and the collectors hitting frames before when the motor was torqued and just rotating the clamps fixed it. Also saw some cheaper headers that were to close to the from in the engine bay and would hit the frame rails during wot.

[Kryckter]

How close are the headers to the frame rail or steering shaft? Also the collector claps are they close to anything? What I'm getting at is when you start torquing the motor something must be hitting or rubbing something. I've saw bolts rubbing in places and the collectors hitting frames before when the motor was torqued and just rotating the clamps fixed it. Also saw some cheaper headers that were to close to the from in the engine bay and would hit the frame rails during wot.

It is the Hellion kit so the manifolds are factory.

I have thought the same thing that something is loose or touching when the motor is under torque. I can not find anything that feels too close or see any marks on the frame/body near exhaust that would go with this assumption...

[Eric@HPTuners]

I believe the description is incorrect. Raising the values should help.

[txcharlie]

Shouldn't your AFR be in the 7s with E85 at .78 lambda?

[Kryckter]

Shouldn't your AFR be in the 7s with E85 at .78 lambda?

Yeah it would be 7.7ish. I tune off of lambda but my downstream gauge is still calibrated for gas stoich.

[txcharlie]

So you are using a WB in addition to the stock WBs?

[Kryckter]

So you are using a WB in addition to the stock WBs?

Yes. The factory wide bands stay in the manifolds so they are upstream/before the turbo. The AFR from them isn't the most accurate and tends to read about .05 rich lambda so I got a wideband after the turbos to get a better reading

[kris5597]

Perhaps the gain in Airflow has increased efficiency. Think of it like this, less back pressure will result in an increase in VE. Possibly your car is at a point now where the current timing is too much. Your probably making more power with less timing. Try dialing the timing back and see what the car does on the dyno.

However, being on e85, knock is not normally seen like this. Perhaps you have a lower content of ethanol in this tank gill up? Or as stated, false knock. Just considering all options.

[txcharlie]

Maybe your Exh VCT needs to be adjusted with the reduction in back pressure. Try increasing overlap 1-2* were you are getting knock and see if a difference is seen.

[Kryckter]

Perhaps the gain in Airflow has increased efficiency. Think of it like this, less back pressure will result in an increase in VE. Possibly your car is at a point now where the current timing is too much. Your probably making more power with less timing. Try dialing the timing back and see what the car does on the dyno.

However, being on e85, knock is not normally seen like this. Perhaps you have a lower content of ethanol in this tank gill up? Or as stated, false knock. Just considering all options.

I can try bring back the timing on the dyno and see what happens. I do test the quality of E85 everytime I gas up. Its always been right between E85 and E90...

Maybe your Exh VCT needs to be adjusted with the reduction in back pressure. Try increasing overlap 1-2* were you are getting knock and see if a difference is seen.

I can try this out, thanks!!!

[SYCK SS]

I can try bring back the timing on the dyno and see what happens. I do test the quality of E85 everytime I gas up. Its always been right between E85 and E90...



I can try this out, thanks!!!

Hey bud, I sent you a PM. Have a question about your tune unrelated to this.