Aces IV additive/octane enhancer

[markmurfie]

I changed gas stations and I'm still seeing about 4* of positive knock with 91 octane and 3.75 pulley. Should I be concerned or is this normal with 91 octane?

Its very likely you have something loose or an exhaust bolt hitting the frame causing false knock. you could try an octane booster and see if it goes away.

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[Whipple SC]

I'm sure whipple's calibration and use of the knock sensor system is optimal. I am and was disputing positive knock values are where you will see the most power. If the value goes positive its saving your engine from knock. If you look at the picture in my last post you will see the red line (knock value) is in the negatives. It has small ups and downs as the system follows what its sensing as borderline knock for the fuel. I have never seen a log that shows this behaviour when this values is in the positives. It's always more staircase looking. If the system is in the positive knock values often from fuel quality, you would want the octane adjustment table from the knock learn to be applied so that the system can use the feedback/overshoot to find the borderline of the fuel and not just be in "survival mode." Whipple flare tool mentions this as a feature so Im sure its in there. People running smaller pulleys and lower octane may have even triggered this and actually be running a lower total ignition advance, but you would have to see logs to confirm. Most tuners also zero out this table and tell customers you need better fuel. When you're selling a 93 only tune I guess that's an acceptable response. Some tuners also zero out ignition tables based on coolant temp, head temp, IAT1 and IAT2, IAT differential, cat temp, etc. compensation tables and make it rely solely on the knock system or noting but what they have in the borderline table. If you add up the compensation needed for each of these that could be plus or minus 5* in its self if environmental and engine conditions lined up just right. Makes it simple for the tuner but not better for the ECU to control the engine with.

The nominal difference between quality 93 and quality 91 is 5 degree's of spark, everything being equal. The octane is not the only thing that makes the motor act differently. The actual chemical mix and specific gravity can range drastically. The PCM is actually calculating through its modeling the specific gravity of the fuel. Peak power is at level 1 knock, level 2 knock is controllable and level 3 is catastrophic. You can run constant at level 1 knock.

Having 1-2 deg of retard @ WOT is fine as the system is still in control of knock. It's when its not in control that is the problem. Of course you want to just add add add, that's a perfect world and in some cases it does that. Locking timing out with no adder is the way our GM and Dodge systems work since they don't use the same logic. But we still get them as close to knock as possible and let the knock sensor catch the few that are just past the threshold.

We do have the octane adjust feature, it takes between 2-4 deg's out depending on area. We have used this for applications in China and some other countries where octane is questionable. It can be used as a tuning tool with pulley changes, we in fact state this in the instructions with 91 octane. If someone changes the pulley with 91, they should be flipping this but of course nobody does. The issue is, you will make more power with less boost and more timing then the opposite at this range. That is not always the case, but it is in this 9-12psi range on pump gas with cats and stock headers as the heat is an issue, which helps instigate more knock. Guys that remove kitties and have LT's get away with a lot more airflow and spark as it lowers the cylinder heat.

If timing and knock is being controlled, its not in survival mode, it is looking for what max timing and or cylinder pressure can be run as the PCM is in control. During durability testing, which in our last case was 50 hours at peak HP, 50 at peak trq, at level 2 knock constantly, steady state. The PCM is in control of it at all times in order to pass. You can't pass the test unless its knocking as that's the torture it must endure. Factory test are even greater then this to prove they will live in all environments.

 

[Whipple SC]

Its very likely you have something loose or an exhaust bolt hitting the frame causing false knock. you could try an octane booster and see if it goes away.

Almost all "false" knock is from valve train. We had some cases where this was tested with LT's and loose exhaust, etc and it does nothing. The frequency is filtered multiple times to get the exact freq of knock. I once thought the same but I was proven wrong with incredible detail of a knock calibrator...

 

[Whipple SC]

I changed gas stations and I'm still seeing about 4* of positive knock with 91 octane and 3.75 pulley. Should I be concerned or is this normal with 91 octane?

You should contact us, consistent 4deg of knock with Tier 1 fuel is not normal. In the meantime, you should flip the octane switch in your flight control software to minimize potential knock.

One easy test is as the others mentioned, put some good gas in (not octane booster) and see if it goes away. This is the simplest way to determine real vs false.

 

[markmurfie]

Almost all "false" knock is from valve train. We had some cases where this was tested with LT's and loose exhaust, etc and it does nothing. The frequency is filtered multiple times to get the exact freq of knock. I once thought the same but I was proven wrong with incredible detail of a knock calibrator...

I know how much the stock calibrations put into filtering out false noise and I'm surprised by how often false knock still pops up. In these forums there's more threads on false knock fixed from exhaust bolts or body contact than anything else. Anything that can transfer a shaking rattle can noise into the block can potentially cause it. Of course if you try to cause it it won't happen, but that random bolt you left your exhaust to close to will definitely cause it every time. Murphy's law.

 

[TheHydro]

You should contact us, consistent 4deg of knock with Tier 1 fuel is not normal. In the meantime, you should flip the octane switch in your flight control software to minimize potential knock.

One easy test is as the others mentioned, put some good gas in (not octane booster) and see if it goes away. This is the simplest way to determine real vs false.

I do have the octane switch flipped in flight control. I have always been about running the safest tune vs the highest performing tune. The only time I see knock is at WOT and it has been as much as 4.5def but the last couple days it has been around 3.8deg. I will throw some 100 octane in the next time I fill up and report back.

 

[TheHydro]

To report back about my knock issues with 91 and 3.75 pulley, I just filled up with half a tank of 100 octane and half a tank of top tier 91 and I had no positive knock at all and was seeing negative knock and 22deg timing advance at WOT. So my issue definitely isn't false knock. I'll keep testing 91 from different stations to see what kind of results I can get. Hoping I'll be able to run straight 91 again without a bunch of knock.

 

[Bartly]

... Hoping I'll be able to run straight 91 again without a bunch of knock.

Don't hold your breath. FI doesn't really work well with 91, I haven't heard of anyone running 91 who doesn't get 3-4+ degrees of knock at WOT. Well I guess there are the manufactureres who claim they've seen it work great, but that probably just helps them sell product to the poor bastards being deceived in 91 octane states.

 

[markmurfie]

To report back about my knock issues with 91 and 3.75 pulley, I just filled up with half a tank of 100 octane and half a tank of top tier 91 and I had no positive knock at all and was seeing negative knock and 22deg timing advance at WOT. So my issue definitely isn't false knock. I'll keep testing 91 from different stations to see what kind of results I can get. Hoping I'll be able to run straight 91 again without a bunch of knock.

22 degrees even with the octane adjustment in the flight control?

 

[TheHydro]

22 degrees even with the octane adjustment in the flight control?

Yes

 

[Whipple SC]

Don't hold your breath. FI doesn't really work well with 91, I haven't heard of anyone running 91 who doesn't get 3-4+ degrees of knock at WOT. Well I guess there are the manufactureres who claim they've seen it work great, but that probably just helps them sell product to the poor bastards being deceived in 91 octane states.

All our product works with 91. That is why the kits ship with 3.75" pulleys and not 3.625". If everyone had 93 we would've shipped them with 3.625" but I can't control that so we went with safe for all places.

 

[Bartly]

All our product works with 91. That is why the kits ship with 3.75" pulleys and not 3.625". If everyone had 93 we would've shipped them with 3.625" but I can't control that so we went with safe for all places.

I'm sure that will make TheHydro feel better knowing that 3.8-4.5 degrees of positive knock means it's working correctly with the 3.75" pulley.

 

[Roh92cp]

Here is a snap shot of the 3.75" on 93. You can see the knock logic is happy at 7200 rpm and 9.3 psi it's advanced timing to 21. Knocker on the NGauge is lower right and total advance is above it.

 

[Whipple SC]

I'm sure that will make TheHydro feel better knowing that 3.8-4.5 degrees of positive knock means it's working correctly with the 3.75" pulley.

Yes, it will once he gets some other gas in there but thank you for your concern. FYI, were in CALI so I'm pretty confident we can make something work on 91 octane.

 

[Bartly]

Yes, it will once he gets some other gas in there but thank you for your concern. FYI, were in CALI so I'm pretty confident we can make something work on 91 octane.

I'd love to hear back from him that different gas did the trick.

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