Was curious how does E85 does in regards to intake buildup on GDI engines?
E85 effects on GDI valve buildup?
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None I suspect, since the injectors are after the valves....
Originally Posted By: JLTD
None I suspect, since the injectors are after the valves....
GDI deposits are due to recirculated blowby from the crankcase ventilation system, so it seems reasonable to think fuel composition might make some difference.
Since ethanol is a small volatile molecule I'd guess E85 would either be the same or very slightly better, but I don't know.
None I suspect, since the injectors are after the valves....
GDI deposits are due to recirculated blowby from the crankcase ventilation system, so it seems reasonable to think fuel composition might make some difference.
Since ethanol is a small volatile molecule I'd guess E85 would either be the same or very slightly better, but I don't know.
I think oil volatility plays a greater role in deposit control than fuel choice.
I think that the amount of viscosity improvers in the oil is the big problem
Originally Posted By: Ducked
Originally Posted By: JLTD
None I suspect, since the injectors are after the valves....
GDI deposits are due to recirculated blowby from the crankcase ventilation system, so it seems reasonable to think fuel composition might make some difference.
Since ethanol is a small volatile molecule I'd guess E85 would either be the same or very slightly better, but I don't know.
Of course they are...you are missing the point that there is no spray of fuel to keep the valves clean; there will be the same levels of blow by and byproducts of combustion...those contaminants remain the same.
Originally Posted By: JLTD
None I suspect, since the injectors are after the valves....
GDI deposits are due to recirculated blowby from the crankcase ventilation system, so it seems reasonable to think fuel composition might make some difference.
Since ethanol is a small volatile molecule I'd guess E85 would either be the same or very slightly better, but I don't know.
Of course they are...you are missing the point that there is no spray of fuel to keep the valves clean; there will be the same levels of blow by and byproducts of combustion...those contaminants remain the same.
Originally Posted By: JLTD
Originally Posted By: Ducked
Originally Posted By: JLTD
None I suspect, since the injectors are after the valves....
GDI deposits are due to recirculated blowby from the crankcase ventilation system, so it seems reasonable to think fuel composition might make some difference.
Since ethanol is a small volatile molecule I'd guess E85 would either be the same or very slightly better, but I don't know.
Of course they are...you are missing the point that there is no spray of fuel to keep the valves clean; there will be the same levels of blow by and byproducts of combustion...those contaminants remain the same.
I dont, of course, know what you know, but I do know what I don't know.
I dont know "those contaminants remain the same."
I'd expect the "blow by and by products of combustion" to be slightly different, because combustion will be affected by the nature of the fuel, and blowby is likely to include some unburned fuel.
If there is fuel dilution of the oil (and I think there will always be some) then the carry over of light fractions of the oil into the intake tract may be affected by the nature of that fuel.
Such effects may not be detectable, but I dont know of any reason to deny their possibility.
Originally Posted By: Ducked
Originally Posted By: JLTD
None I suspect, since the injectors are after the valves....
GDI deposits are due to recirculated blowby from the crankcase ventilation system, so it seems reasonable to think fuel composition might make some difference.
Since ethanol is a small volatile molecule I'd guess E85 would either be the same or very slightly better, but I don't know.
Of course they are...you are missing the point that there is no spray of fuel to keep the valves clean; there will be the same levels of blow by and byproducts of combustion...those contaminants remain the same.
I dont, of course, know what you know, but I do know what I don't know.
I dont know "those contaminants remain the same."
I'd expect the "blow by and by products of combustion" to be slightly different, because combustion will be affected by the nature of the fuel, and blowby is likely to include some unburned fuel.
If there is fuel dilution of the oil (and I think there will always be some) then the carry over of light fractions of the oil into the intake tract may be affected by the nature of that fuel.
Such effects may not be detectable, but I dont know of any reason to deny their possibility.
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Fair enough. Without any testing we are speculating...but IMO there WILL be deposits, though they might be lessened by the alcohol in the fuel.
Originally Posted By: JasonC
Was curious how does E85 does in regards to intake buildup on GDI engines?
Probably good for prevention. If i remember right back when I was looking into how they tune the ECU for flex fuel vehicles, they really lean out the A:F and advance the timing for the higher octane in order to try and recover MPGs lost due to the ethanol energy decrease. This would lead to less fuel dilution reaching the oil, reducing oil volatility and decreasing the vapors coming back through the PCV that condense and grow on the intake valves.
Was curious how does E85 does in regards to intake buildup on GDI engines?
Probably good for prevention. If i remember right back when I was looking into how they tune the ECU for flex fuel vehicles, they really lean out the A:F and advance the timing for the higher octane in order to try and recover MPGs lost due to the ethanol energy decrease. This would lead to less fuel dilution reaching the oil, reducing oil volatility and decreasing the vapors coming back through the PCV that condense and grow on the intake valves.
Originally Posted By: Ducked
If there is fuel dilution of the oil (and I think there will always be some) then the carry over of light fractions of the oil into the intake tract may be affected by the nature of that fuel.
Such effects may not be detectable, but I dont know of any reason to deny their possibility.
I ran tests on my Mazda3 skyactiv when I had it. You'll notice most skyactiv UOAs from people who run 87 octane have fuel dilution problems. Mine and a few others who also ran 91 octane exclusively had zero signs of fuel showing up in the oil. The oils held their viscosity perfectly and flash points were not degraded. The fuel used will impact oil properties. Now whether that is enough to impact rate of intake valve deposit formation is another experiment I didn't have time to fully evaluate for my car. The valves were spotless when I got rid of that Mazda3 but it only had around 75k miles on it if I remember right.
IMO, it seems to be most tied to compression ratios. Engines with high compression ratios over 12:1 are the ones with the fuel dilution issues, so it isn't just DI but most DIs run high compression.
Ford's 2.0L DI doesn't run high compression and shows no signs of fuel dilution even on 87 octane. The non-DI engines that are running high compression are also showing signs of fuel dilution but they can keep their valves clean with fuel so not as big of a deal.
If there is fuel dilution of the oil (and I think there will always be some) then the carry over of light fractions of the oil into the intake tract may be affected by the nature of that fuel.
Such effects may not be detectable, but I dont know of any reason to deny their possibility.
I ran tests on my Mazda3 skyactiv when I had it. You'll notice most skyactiv UOAs from people who run 87 octane have fuel dilution problems. Mine and a few others who also ran 91 octane exclusively had zero signs of fuel showing up in the oil. The oils held their viscosity perfectly and flash points were not degraded. The fuel used will impact oil properties. Now whether that is enough to impact rate of intake valve deposit formation is another experiment I didn't have time to fully evaluate for my car. The valves were spotless when I got rid of that Mazda3 but it only had around 75k miles on it if I remember right.
IMO, it seems to be most tied to compression ratios. Engines with high compression ratios over 12:1 are the ones with the fuel dilution issues, so it isn't just DI but most DIs run high compression.
Ford's 2.0L DI doesn't run high compression and shows no signs of fuel dilution even on 87 octane. The non-DI engines that are running high compression are also showing signs of fuel dilution but they can keep their valves clean with fuel so not as big of a deal.
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