Knock Retard LS3 E10 vs 98

[Daniel Souza]

I just wanted to share some data collected with OBDlink Mx and Torque app comparing the Knock Retard from Caltex E10 and Caltex 98.

Just some background first:

The ECU has a parameter called "Knock Learn Up Thresh" (HPTuners). The Knock Learn factor is incremented (moved towards low octane) if knock retard exceeds this value. A nice explanation can be found here

So values above 1.5 deg for the LS3 the ECU will start shifting to the low octane spark table.

The data is what one would expected. The E10 goes over the threshold much more often.


The interesting thing is that a combination of simple tools can be used to keep track if the car is running as expected and also help the early stages of learning tuning .

 

[Chookah]

I don't understand any of that, but I often choose E10 over standard unleaded cause 94 vs 91.
Am I doing it wrong?

 

[monstar]

I don't understand any of that, but I often choose E10 over standard unleaded cause 94 vs 91.
Am I doing it wrong?

You are correct in choosing higher octane is what the thread is saying, whether it contains 10% ethanol is almost irrelevant.
So e10 that's 91 octane is more knock limited than other retail products called e10 that are 94 or 95 or 98 octane.
In other words no matter what the fuel company calls it's retail product at the bowser it's not the 10% ethanol declaration that makes much difference to knock, it's the declared octane number that relates to knock limit.
@Daniel Souza what is the declared octane of the e10 you used?
As an aside if the ethanol fraction were legislated at even 20% (e20) there would be a huge difference in knock limit, much cheaper, less emissions, locally sourced and most importantly NA cars like ours could be tuned for better performance.
Then again if you were looking to limit knock, maximise performance, boom for your buck and do your car a favour you would dance from one pump to another with a $15-$20 squirt of inexpensive flex fuel into your full tank of whatever, whenever and wherever it was available.
The higher the ethanol flex content the higher the octane rating and less significant the base petrol's octane.
You don't need petrol in your L77/LS3 fuel at all in Australia, at 85% ethanol even water is a much better substitute as an additive to the blend (that's alcohol and water) in terms of emissions, torque and thermal efficiency.

 

[SuckSqueezeBangBlow]

I'm also interested to know whether the e10 94 from Caltex was used. I've been running Vortex 95 for the last few tanks and can't imagine 95 being that much better than 94?

 

[Daniel Souza]

The E10 is from Caltex and I believe they claim 94 RON. A quick search on Caltex site didn't mention anything. Just mentions it meets the requirements for Fuel Quality Standards Act 2000.
"
Bio E10 Unleaded

Caltex Bio E10 Unleaded Petrol is a high quality unleaded petrol formulated with 10% ethanol. It meets the requirements of the Fuel Quality Standards Act 2000. Ethanol is a renewable non-fossil fuel which helps reduce greenhouse gas emissions and reliance on fossil fuels. "

I regards the data, the interesting thing is the ECU spend most of the time on the high-octane table even using E10. It would be good to monitor the Knock Learning Factor to know exactly where the ECU is between tables.



Next tank I will use Caltex 91 and see the results.

 

[monstar]

TL;DR flagging which spark table is being used does not correctly reflect the quality or appropriateness of the fuel or its octane rating to the engine, rather says more about the state of tune and it's ability to adapt appropriately to various conditions, then as a lesser factor consider the impact of fuel. In the simplest case it is possible to operate on low octane using the high octane map, and vice versa. So which map doesn't tell you definitively about the fuel quality good bad or otherwise rather primarily tune vs conditions.
The delineation of which spark table is being used doesn't matter much, it's not that one is better than the other just whether state of tune seems more appropriate. For example because one fuel blend has a lower knock limit full bore at sea level in winter practically doesn't mean it is better or worse putting about a scenic alpine tour in summer on high octane. The tables swap, so that means the ECU maps spark not for octane per sé but as appropriate.
Could prolly say Lo map is like protection mode now with sophistication of the e38/e67 OS other tables come into play like ethanol blend, cam phaser, AFM, EGR, boost, IAT2 etc., so the alternate map is less about an octane delineation and more about state of tune and at what point it is dealing out conservative spark.

 

[Geoff6666]

I don't really care too much about the tables and graphs. I'd just like to know what is best to put in my car. Some fuels are supposed to be cleaner, some are supposed to improve performance and some are supposed to be better for the environment. So. . . . . I just want the fuel that makes my car go best, looks after my engine the best, and if it's a greener option that would be good too! Cost is not a major factor or I'd have bought a 4cyl! Which fuel should I use?

 

[monstar]

I don't really care too much about the tables and graphs. I'd just like to know what is best to put in my car. Some fuels are supposed to be cleaner, some are supposed to improve performance and some are supposed to be better for the environment. So. . . . . I just want the fuel that makes my car go best, looks after my engine the best, and if it's a greener option that would be good too! Cost is not a major factor or I'd have bought a 4cyl! Which fuel should I use?

To be exact depends on which year is your ute?
Practically depends on you locale?

 

[07GTS]

i was on the dyno the other week seeing what my gains were from going E85 and durin the 6 runs on the dyno i completely cleaned the WB sensor in the tailpipe so if u want a clean engine ethanol is the way to go, also when i had my headers off a while ago i noticed the exhaust ports were back to alloy again nice and clean i can only think the whole combustion chamber is nice and clean also

 

[monstar]

i was on the dyno the other week seeing what my gains were from going E85 and durin the 6 runs on the dyno i completely cleaned the WB sensor in the tailpipe so if u want a clean engine ethanol is the way to go, also when i had my headers off a while ago i noticed the exhaust ports were back to alloy again nice and clean i can only think the whole combustion chamber is nice and clean also

Same the entire engine internals while I had it apart were not only sort of clean but clinically sterile!
Check ethanol combustion at about 2:00