Running a car on ethanol?

Dogbreath said:
The answers are in the thread if you read it!

If you want to use something like E85 you need to get the car remapped, and may need larger injectors since they will be flowing quite a bit more fuel. To take advantage of the higher octane the compression ratio needs to be raised, obviously this means you can no longer safely run on standard unleaded. You will also need to check that all parts of the fuel system are compatible with ethanol based fuels.
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(my emphasis): no, you just need to advance the ignition. If my car was remapped for E85 I'd get about another 30-40 bhp (call it 8-10%) almost entirely from the ignition - I believe another 3-5 degrees is possible. On an auto-adjusting ECU you can go back to odinary unleaded and the ECU will just retard the ignition again as soon as it detects the inevitable det. But you will probably struggle to advance the ignition very far just by running E85 without the map.


M
 
I agree, and think most engine management and fuel systems have the flexibility to adjust to the fuel to give extra performance. By the time you needed think about compression ratio's you would have gone past the point of looking for a quick and easy performance boost.

I have had 17 and 18 degree's of advance on a SR20DE.
 
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Meridian said:
(my emphasis): no, you just need to advance the ignition.
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No, you need to increase the compression ratio. If your engine is already running retarded to prevent detonation on petrol then there will be some gains to be had, but all the ignition advance in the world is not going to extract all the potential from ethanol with a low compression ratio. With a higher CR you would need less ignition advance and the engine would make more power (and use less fuel under non-WOT conditions).

I don't honestly understand why so many people appear to think that lots of ignition advance is some kind of goal when trying to extract power. Ideally you want to run the absolute minimum advance possible, consistent with achieving peak cylinder pressure at the correct time. A high CR delivers higher peak pressure, and makes the mixture burn faster so less advance is required.
 
A lot of people use the Lotus E85 as an example too. They think that because the E85 version makes more power than the normal Exige S then it must be the same on all cars.

One of the massive advantages - if you exploit it - is that you can use the process of the fuel turning from a liquid to vapour to help drop inlet temperatures massively

If you ran E85 on a standard fuelling setup and just alter the ignition then the engine may last 5 seconds before it melts.
 
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jigger said:
I agree, and think most engine management and fuel systems have the flexibility to adjust to the fuel to give extra performance. By the time you needed think about compression ratio's you would have gone past the point of looking for a quick and easy performance boost.

I have had 17 and 18 degree's of advance on a SR20DE.
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50% more fuel. Vary rarely will the fuel system have such redundant fuelling capacity
 
Dogbreath said:
No, you need to increase the compression ratio. If your engine is already running retarded to prevent detonation on petrol then there will be some gains to be had, but all the ignition advance in the world is not going to extract all the potential from ethanol with a low compression ratio. With a higher CR you would need less ignition advance and the engine would make more power (and use less fuel under non-WOT conditions).

I don't honestly understand why so many people appear to think that lots of ignition advance is some kind of goal when trying to extract power. Ideally you want to run the absolute minimum advance possible, consistent with achieving peak cylinder pressure at the correct time. A high CR delivers higher peak pressure, and makes the mixture burn faster so less advance is required.
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But you've painted yourself into a corner: now you can only run on ethanol/E85 etc surely? The beauty of advance is that it's reversible. And cheap(ish). There's a price for everything, and most people I suspect aren't willing to pay that one. Race cars yes, road cars no, until (if ever) E85 becomes common.


M
 
Meridian said:
But you've painted yourself into a corner: now you can only run on ethanol/E85 etc surely?
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You simply need a car with variable compression, say one with a turbocharger.

You can't make the best use of both fuels with a fixed compression ratio, it will always be compromised on on or the other, or likely both. Given the considerable increase in fuel consumption with running on ethanol, it makes sense to make the most use of the extra fuel you are pushing through.
 
Dogbreath said:
You simply need a car with variable compression, say one with a turbocharger.

You can't make the best use of both fuels with a fixed compression ratio, it will always be compromised on on or the other, or likely both. Given the considerable increase in fuel consumption with running on ethanol, it makes sense to make the most use of the extra fuel you are pushing through.
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Fuel use wouldn't be overly changed though would it ?

If you are talking about the American E85 fuel thats 85% ethanol 15% petrol.
 
jigger said:
Fuel use wouldn't be overly changed though would it ?
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Yes, as mentioned previously in the thread you need 30% more ethanol to get the same energy as petrol. Raising the CR will slightly offset this, but it's not going to make up for that kind of deficit.

Look at the figures for the current "Flexible fuel" cars, they take a good 25% or more hit on economy when burning E85.
 
jigger said:
I agree, and think most engine management and fuel systems have the flexibility to adjust to the fuel to give extra performance. By the time you needed think about compression ratio's you would have gone past the point of looking for a quick and easy performance boost.

I have had 17 and 18 degree's of advance on a SR20DE.
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What?
Vehicle ECU's generally don't alter the fuelling at all for large throttle opening situations.
EDIT** I worded that badly... of course the fuelling "requirements" change, however it isn't looking to adjust it from some external sensor input.
It just has a look up table of how long the injector should be open at a given rpm / load. This is what never changes

The only time it'll will adjust will be when you are sat at traffic lights or cruising steady state down the motorway

It's the timing that is constantly adjusted, so your 17-18 degrees of ign advance means nothing in the real world
 
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nokinidea said:
What?
Vehicle ECU's generally don't alter the fuelling at all for large throttle opening situations.
EDIT** I worded that badly... of course the fuelling "requirements" change, however it isn't looking to adjust it from some external sensor input.
It just has a look up table of how long the injector should be open at a given rpm / load. This is what never changes

The only time it'll will adjust will be when you are sat at traffic lights or cruising steady state down the motorway

It's the timing that is constantly adjusted, so your 17-18 degrees of ign advance means nothing in the real world
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a lot of cars do have long term fuel trims that can be applied to the full map if the short term trim fuel correction is required consistantly to maintain stoich under closed loop lambda. This long term trim is applied to all load sites, including WOT.
 
Yes but it's not trying to achieve a set figure it "sees" at full throttle, only a guess adjustment from what it saw whilst in cruise. (which is what you said I guess :D)
As has been already said running E** requires a different stoich point anyway so it'll always be wrong.:D
 
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