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[Datsun 1200 encyclopedia]

E85

From Datsun 1200 Club

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Category: Fuel System

E85 is a blended fuel composed of a variable amount of Ethanol and Petrol. It requires a much richer mixture then straight gasoline, so an upgraded fuel delivery system is required. As of now in most countries, it will cost more per distance traveled than straight gasoline. Ethanol, being a form of alcohol, has less energy per litre -- and as with any high-octane fuel, E85 or petrol, the engine needs different tuning to take advantage of it. However, E85 has more octane than regular gasoline -- so if the engine is built for high compression, E85 can make more power than gasoline.

Contents

Overview

E85 is a variable fuel, with up to 85% alcohol and the rest is gasoline/petrol.

Any gasoline engine can run E85 with a carburetor change and (in some cases) larger fuel lines and a higher capacity fuel pump.

Modifications for E85

  • Carb jets replaced with bigger ones
  • Timing and spark adjustments
  • Tank and fuel lines should be lined (but not required)
  • fuel lines replaced with larger ones (in some cases)
  • Seasonal/periodic rejetting (when the E-content varies)
  • Compression upped from 9:1 to 12:1

E85 will work with the normal 9:1 compression, but power will be down about 15%. And fuel range will be cut 25%. To make effective use of E85, the compression ratio can be raised. A change from 9.0 to 12.0 will make the same power as on straight gasoline.

A turbocharged engine can be more easily modified. Raise the boost to make up the lost power - and then gain some more. Alcohol fuel has a significant cooling effect and so permits higher boost levels.

Power Gain Requirements

Discussions

benny: Power delivery is awesome, compared to pump fuel ... The engine was built specifically to take advantage of burning an alcohol based fuel ... the comp ratio was ~ 13.8:1 ... Basically more power to be had from e85 over pump fuel, but the trade off is that you use considerably more of it.

Engine Modifications

Ignition

  • different spark plug temperature range and electrode type (as with any modded engine)
  • recurve the distributor Spark Curve


Carburetor

  • Larger main jets & air jets
  • Larger idle jets
  • Larger power jets
  • Different emulsion jets, suitable for alcohol (thinner and with different hole pattern)
  • Different accelerator pump setting

Fuel Economy

With the same size fuel tank, E85 will travel fewer miles. According to the US Government:


FFVs [Flexible Fuel Vehicles] operating on E85 get roughly 15% to 30% fewer miles per gallon than when operating on regular gasoline fueleconomy.gov

E85 is about 70% the energy per volume of gasoline and so will require about 30% higher fuel flow.

In a typical older gasoline engine, power will be down about 30%. The "lost" power can be recovered by large compression ratios changes or by higher supercharger boost. Some manufacturers of turbo engines report equal or better fuel economy by using higher boost levels.

Octane and compression ratio

  • Australia: E85 have been tested with a RON anywhere between 100-110. It's burn rate is around 30% more then 98 RON fuel.
  • USA: octane rating of E85 is 94-96 (R+M)/2, though it is commonly marketed as 100. The Chevy hot rod crowd say you can generally only run 13.5:1 ratio with E85, so it seems consistent with the higher number.

NOTE: Pump gasoline 98 octane can do 12:1 already, depending on the engine design

An engine designed for a lower octane will not make more power with higher power fuel. To take advantage of the higher octane and so boost fuel economy and/or power level, mods are required.

  • More spark advance will gain a little more power
  • Higher effective compression ratios can gain a lot more power

Both can result in higher fuel economy.

Corrosive effect

If any water vapor gets into Ethanol, it creates a corrosive acid, which can eat through rubber parts.

For this reason a sealed fuel system is used, such as all modern cars use anyways for emission control purposes. The Datsun 1200 went to a sealed system in 1972 for North America, 1973 for Japan, and 1978 for Australia. But it's not as well-sealed as cars made in the 1990s.

Ethanol absorbs moisture from the air so must be kept air tight when in storage. Steel fuel lines would be fine. There have been some stories about the rubber lines eating out, while theoretically true, there are people that have been running rubber lines with no problem.

You also need to consider a fuel pump that is compatible with alcohol, which has seals, diaphragms and valves resistant to alcohol.

Environment

Burning any hydrocarbon fuel releases COx to the atmosphere. It appears that E85 has overall reduction compared to gasoline, but this is a complex topic. See wikipedia:E85 for more information.

Sugar cane-based ethanol is used in some countries, notably Brazil where it is the #1 fuel.

At this time, corn-based methanol is not cost-effective with gasoline except with government subsidies. A concern is the replacement of food crops with fuel crops, possibly causing food prices to rise.

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This page has been accessed 11,526 times. This page was last modified 02:59, 22 January 2016. Content is available under Datsun 1200 Club.