Could be other things besides the head like head gasket thickness, shape of the bottom of valve .
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Stock engine, stock map running E85?
- Thread starter vwengineer
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Could be other things besides the head like head gasket thickness, shape of the bottom of valve .
vwengineer
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Yes, right
I actually posed this question to a group a few days ago. In California 91 is the highest octane available for public purchase. I was curious about slightly mixing E85 to get myself around 93-95 octane. Since all gas now has 10% ethanol here I assume that adding 2 gallons max of E85 at an empty tank would be fine. The ECM should be able to handle the fuel just fine. I'm on stock tune 2008.5 BPY.
Does it seem logical to give it a test run with enough E85 to hit 93 octane?
Plus I would rather not spend $20-$50 on octane booster when E85 usually runs $2/gal.
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Does it seem logical to give it a test run with enough E85 to hit 93 octane?
Plus I would rather not spend $20-$50 on octane booster when E85 usually runs $2/gal.
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vwengineer
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To me it makes sense. Although I don't run E85 for the moment (because I have no gas station that sells it near me), I tested both 40% and 20%. It seems that 20% is enough to prevent ignition timing changes due to knock at least on the stock map. So 2 gallons should be enough, from what I observed, the lambda sensor needs to be warm for the engine to adapt and the adaptation process takes about 2-3 miles so drive gently at first. If you reset the faults or disconnect the battery, take into account that no adaptation will take place until the engine is hot so don't floor it (you shouldn't anyway aha)
The computer can trim up to 25% but after 20% you get a check engine light, so I would not go further than 50-60% E85.
The computer can trim up to 25% but after 20% you get a check engine light, so I would not go further than 50-60% E85.
There won't be any gains until you up the ignition advance, but kudos for running up to 40% ethanol as an experiment. I've often wondered about doing the same, but I can get 99 octane in the UK, so the appetite to do it isn't there.
FWIW, the Hitachi HPFP is ethanol compatible and there is no rubber on the LPFP, and the tank is plastic, as are the lines, so all good there. The only rubber parts are the LPFP feed lines on the engine plumbing.
Your English is very good by the way!
FWIW, the Hitachi HPFP is ethanol compatible and there is no rubber on the LPFP, and the tank is plastic, as are the lines, so all good there. The only rubber parts are the LPFP feed lines on the engine plumbing.
Your English is very good by the way!
vwengineer
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Hey thanks! There are gains compared to 95 RON fuel as the ignition timing is heavily modified under high load due to knock (logged up to 6 degrees). No gains compared to 98 RON though.
My point was that E85 brings a win/win situation, it's cheaper than regular gasoline and it actually increases the octane rating of that gasoline. I admit that without a custom map the interest is limited unless you live in a country where the price difference is big (in France E85 is 0.7€/l vs 1.55€/l for 95 RON)
My point was that E85 brings a win/win situation, it's cheaper than regular gasoline and it actually increases the octane rating of that gasoline. I admit that without a custom map the interest is limited unless you live in a country where the price difference is big (in France E85 is 0.7€/l vs 1.55€/l for 95 RON)
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One thing to factor in would be that it takes about 35%-40% more E85 to make the same power. It does provide more knock protection but it provides less power than gasoline. So as you raise the E85 content of your blend you may not be getting any timing retardation but without a tune that significantly raises the amount of fuel you are using, it may not be entirely a complete win.
E85 with the right tune.... is definitely a win when it comes to making power with a big turbo. It will take a lot of it to make the big power so the tradeoff is that your mileage goes down considerably but boy does it work.
If I don't get the power levels I want out of my new setup which will be 91oct plus Aquamist direct inject 100% Methanol, then I will go E85 if I have to.
vwengineer
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That's right as I noted with 40% E85 the LTFT goes up to ~13%, so yes your mileage is a bit reduced, so without a tune if E85 does not come at a 30% discount it does not make sense (also taking into account that 98 RON is about 5% more expensive than 95).
The reason why you don't go to E85 directly is because of the higher fueling requirements? As I understood methanol injection can be unreliable sometimes?
The reason why you don't go to E85 directly is because of the higher fueling requirements? As I understood methanol injection can be unreliable sometimes?
No, mostly availability of E85 in my area. Only one brand of fueling station is currently carrying it at some of their locations in my area. Also I have used water meth quite successfully over the last 18 years on a number of forced induction cars so I am comfortable with it. E85 would be all new area to learn about for me.
vwengineer
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Ok I get it. I think it's also complicated to use E85 in big turbos setup because you need that much fuel. You cannot even do a stage 1 on E85 without replacing the HPFP so I think you are quickly limited in power even with bigger injectors and an upgraded HPFP.
vwengineer
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So new test this week, I am now running 65% E85 (well it's more E78 in winter apparently). Car still runs strong and very good, LTFT is at 20.3% with no CEL and no DTC. I am also not sure that fuel consumption is really 20% higher, still have to check on my usual routes.
vwengineer
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Had to scale back a bit, car ran well for 150 miles at the E85 ratio but today going on a uphill highway on cruise control I felt the car cutting for a second and then accelerating to regain the speed. Scanned for faults and got:
18609/P2177/008567 - Bank 1; System Too Lean off Idle
Not sure exactly what the "off Idle" means but that's not good. No check engine light car still pulled very well after this, LTFT was stable at 20.3%. For safety I decided to add some more gasoline, lowering at about 55% ratio which it should handle without issues.
I am still not sure what caused it to cut the throttle, a safety measure maybe? Or is that maybe a clog in the fuel system that cut the fuel supply for a second which then triggered the code (E85 can wash dirt in the tank or fuel lines and eventually clog the fuel filter or fuel pump but I didn't get a low pressure code though).
18609/P2177/008567 - Bank 1; System Too Lean off Idle
Not sure exactly what the "off Idle" means but that's not good. No check engine light car still pulled very well after this, LTFT was stable at 20.3%. For safety I decided to add some more gasoline, lowering at about 55% ratio which it should handle without issues.
I am still not sure what caused it to cut the throttle, a safety measure maybe? Or is that maybe a clog in the fuel system that cut the fuel supply for a second which then triggered the code (E85 can wash dirt in the tank or fuel lines and eventually clog the fuel filter or fuel pump but I didn't get a low pressure code though).