Ethanol - Impala Tech
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post #1 of 8 (permalink) Old 07-04-2010, 11:24 AM Thread Starter
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Ethanol

I had planned to put a late 80's IROC injection system on my 66 327 Impala for looks and performance. I recently heard from a friend that Oregon's 10% ethanol fuel destroyed the injectors in his stock Camaro, so now I'm worried. Can anyone give me or direct me to information on what I can do to avoid similar issues, or is it even worth the money to update the older system (which I already own, unfortunately). Will I also be required to make changes to the computer?

Got to love the government for protecting us against ourselves.

Thanks,
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post #2 of 8 (permalink) Old 07-04-2010, 02:10 PM
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Alcohol is acidic and it is absorbic (acts as a desiccant pulling moisture out of the air). So anything that is going to be affected by a strong polar compound or acidity will have problems (such as paper fuel filters). This includes natural gum rubber used as a seal in a lot of places, or as a lining of old fuel lines.

President Jimmy Carter (remember him?), that’s how long ago this has been in effect. What you say? A presidential order stating that all cars manufactured after 1973 (which includes the tuned port injection system off of the Camaro's 305 motor) where to be made capable to use alcohol instead of gasoline. This was because we were going to stop buying gasoline from our friends the Arabs (and Persians) in the middle east and grow our own fuel supply.

Well as with any bureaucracy it took a little longer to implement the presidents decree (from 1980) and enact it into law. But it finally happed in 2003 when congress mandated by law that all fuel sold in the country should have at least 10% by volume alcohol (the goal is 85% according to the law but don't hold your breath as the gas companies are fighting the conversion tooth and nail the only way they know how by buying congressmen and senators to vote foe them and not their constituents). All cars should work fine with gasohol and I do not believe the injectors where the problem with your friends car (they are made by Bosch and the Germans have used gasohol for decades).

What probably happened is the duty cycle to supply the engine caused them to burn out. When running gasohol you have to burn more of it to get the same mix of fuel to air that you do with gasoline (stoichiometric) Add to this an engine requiring more fuel than a stock 305 would want to deliver normally and you exceed the 75% duty rating of the injectors (you are supposed to use a bigger injector rated in pounds of fuel per hour when using a 305 manifold on a 350, or even a 327 if your going to be revving it up).

Big Dave
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post #3 of 8 (permalink) Old 07-04-2010, 09:58 PM Thread Starter
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Quote:
Originally Posted by Big Dave View Post

...What probably happened is the duty cycle to supply the engine caused them to burn out. When running gasohol you have to burn more of it to get the same mix of fuel to air that you do with gasoline (stoichiometric) Add to this an engine requiring more fuel than a stock 305 would want to deliver normally and you exceed the 75% duty rating of the injectors (you are supposed to use a bigger injector rated in pounds of fuel per hour when using a 305 manifold on a 350, or even a 327 if your going to be revving it up).

Big Dave
What my friend says is that the alcohol ate the coating off the injector coils, causing the CPU to blow a circuit or some darn thing. I was talking another friend today that says he sells a product at his business that breaks down the ethanol. Cost of the product adds about $0.20/gal to your fuel costs. Still cheaper than replacing a computer and injectors for a car that is not a daily driver.
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post #4 of 8 (permalink) Old 07-05-2010, 12:41 AM
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There have literally been tens of thousands of TBI 305 cars on the road and yours is the first that instance that I have heard of that had a problem with alcohol. The insulation on the injectors will over heat and break down if you run them over their duty cycle.

Big Dave
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post #5 of 8 (permalink) Old 07-05-2010, 12:47 AM Thread Starter
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Maybe that is actually what happened, I'm only going by what he said, or thought. So larger injectors may be at least part of the answer? Any kind of guidelines on what is the best size to use?
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post #6 of 8 (permalink) Old 07-05-2010, 01:25 AM
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They are sized by pounds of fuel per hour, the same way you chose a carburetor size. It is cubic inches times volumetric efficency (and don't think it is 100%. It isn't hardly ever that high on a street motor, and even with a race motor it hits 100% VE only near the torque peak) but you have to factor in the RPM you intend to use the car (a TBI is only makes power 5200 RPM) and finally the nuber you come up with has to be multiplied by 1.25to get a duty cycle of 75%.

You can figure about 219 pounds per hour for a 6,000 RPM with a 327 divided by 8 for the number of cylinders yields 27.4 lbs per hour injectors times 1.25 gives 34 pounds per hour on the size. This is a ball park and needs to be computed or verified with someone more knowledgable than me on EFI.

Big Dave
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post #7 of 8 (permalink) Old 07-05-2010, 09:45 AM Thread Starter
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Thank you very much for the input, Big Dave. At least this get me on the right path. Will the CPU take care of itself with the larger injectors or will that also need some modification? If you can't tell, this is my first venture into modifying a car with components that are computerized. I have no intent to race the car. It's being built as a cruiser.
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post #8 of 8 (permalink) Old 07-05-2010, 06:01 PM
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You will probably need to modify the fuel map as the 305 is a long stroke slow rev small displacement engine. The 327 will really rev due to it's shorter stroke and it breathes much better at any RPM than a 305 would as your valves are unshrouded by the larger bore, and it is bigger than a 305 so it will want more fuel. The small diameter long tubes of the tuned port injection system are tuned for a 305 at 2800 RPM to ram air into the cylinders. They are restrictive in terms of air flow but will respond to the usual trick (smoothing the air inlet, enlarging the air inlet and enlarging the plenum air box, as well as increasing the size of the tubes and a change of the manifold to loose the ninth injector which is your choke and the EGR valve.

Big Dave
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