Re: Esso Supreme and knocking ....
Ok I found that it was my injectors in the end and got it replaced .......
But here's something interesting ... At least for me -
I was working in my tune and last week was pretty much focused on my AFR (air fuel ratio). This was part of my prep to make sure tunes are fully acclimatised to local conditions.
When I say local conditions - it's not just humidity and hot temperatures. Fuel is important as well.
Fuel in SG is distinctly different from the other countries like Germany, U.S. Or Malaysia. Sulphur content is different due to different regulations.
Emission requirements and politics are different as well. In the U.S. Ethanol content could be typically at 10% (E10) and if available as high as 85% (E85). Having Ethanol in the fuel system is a big deal in tuning the AFR. Ethanol compared to petrol has a stoic of only 6:1. And the energy potential it has is much less than petrol - burning ethanol is like burning alcohol - very weak - like what you would see in a cocktail at a pub. At the same time, mileage is also a lot less.
So why add ethanol ? It raises RON octane levels and aids in controlled combustion within the cylinders. And because Ethanol is a derivative of organic agriculture - it may become the replacement for fossil fuels which is not recyclable.
Being that the specific gravity (SG) of petrol is very different from ethanol - the fuel pump which is controlled by the DME (engine Ecu) needs to be tuned in such a way that it takes into account the change in SG when Ethanol is present - SG of 0.739 vs 0.787.
This would mean that the flow rate of the fuel pumps to maintain AFR targets would be influenced by Ethanol presence.
Do we have Ethanol here in SIngapore ?
Searched for a couple of hours for MSDS of the various petrol available here. Nothing except for 1 published by Shell. The chemical composition shows naphtha, toluene, benzine (even the carcinogenic MTBF which the U.S. regulated) is present and a bunch of trade secret stuff - but not a trace of Ethanol.
So I went to the nearby Esso and Shell and got samples of Supreme 8000 and V-Power.
Remember your chemistry lesson in school ?
Since the SG of Ethanol, Petrol and Water is different - we can separate the 3 fluids using their SG.
Bought and drank 2 bottles of mineral water till it has about 100ml left (why waste it the water...).
Then I filled it up with Supreme 8000 and V-Power in each bottle respectively. See the pics for the results. The masking tape shows the original water level.
Note that - the separation only shows 2 bands. Not 3. If ethanol is present - there would be a cloudy band in between the water and the petrol. Also the water level did not increase above the masking tape. Ethanol is miscible in water - so if ethanol is present the water volume would be raised.
So no ethanol in Singapore petrol. This would mean the Bros here that got an off-the-shelf tune from the U.S. probably get a tune that is calibrated for an E5-E10 petrol.
Made the changes to the tune and flashed it into the ride. And I tested the difference - E0 vs E5 vs E10. My fuel trims results range from lean to rich as read by the lambda sensors. Which to me is a big deal ..... My mech felt the diff when he used my car to collect parts from Eng Soon.
Supreme 8K
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V-Power
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