E85 Tuning and general info thread.

[NitroDann]

Its been suggested a couple times now I start an E85 thread, where I could post some useful links and info.

I figure Ill repost a link just posted now as its a good start.

And Ill debunk some myths to do with E85, and whats needed to do the swap and what can be expected.

Heres the reposted link containing plenty of info.

http://www.toymods.org.au/forums/tech-conversions/62301-e85-petrol.html


MYTHS

So Ive been on E85 for 6 months now or so. STOCK STANDARD FUEL system.
There has been much rubbish about the corrosive nature of e85 thrown around. Ive had no issues at all and neither have any of the hundreds of turbo mx5 boys whove been running it in the states for years.

Yes its true that old carbie clunkers were not designed with modern fuel system technology. But almost any car that came out fuel injected has the exact same fuel lines, as the high pressure fuel injection fuel systems had to be redesigned to comply with new laws pertaining to fuel hose and O ring quality.
Carbie cars dont have super high fuel pressure systems like injected cars do.

This means all mx5s fuel systems are totally safe to run e85 through.

For the haters, after 6 months, on the stock 20 year old lines all the insides of the lines are in great condition, as is the pump and associated seals and O rings.

ADVANTAGES

Each kilogram of E85 has a lower calorific value than a kilo petrol, just like a kilo of water has less calories than a kilo of coke. Im talking in kilos not litres for a reason that we will come to. This means that for each tank of e85 you will get less energy out. This does not mean less power necessarily, it means less total distance.

Fortunately E85 is denser than petrol, meaning that a litre weighs more, and therefore has more atoms and holds more energy than we first realise, though it is still less per litre than petrol. Its just not as bad as it first sounds.

Now some nerdy stuff.
For something to burn, it needs the right amount of oxygen atoms for each atom of fuel, if we compare this by weight as a ratio, its called the stoichiometric ratio. for example many will have heard that the stoichiometric ratio for petrol is 14.7:1.
This means that if you burn a kilo of fuel with 14.7 kilos of air it will burn in the perfect ratio, with no air of fuel being left over when burned in those proportions.
E85 has a stoichiometric ratio of 9.7, meaning you only need 9.7 kilos of air per kilo of fuel.

Because your engine will always suck in the same amount of air regardless of fuel, we have to add more fuel, we cant add less air.

Soooo...
Although E85 produces less power per kilo, we actually need to add 51% (14.7/9.7 = 1.51, hence 51% more) more to run the car. This addition of 50% more fuel means the car makes MORE power. Its a bit weaker but we add so much more we actually end up making about 18% more power (torque actually)

So we add 51% more fuel by WEIGHT, but because its heavier than petrol we only have to add approx 32% more by VOLUME. Because we buy it by the litre not the kilo, and our injectors are rated by the CC not the gram, this 32% is what we have to remember when tuning or sizing injectors.

Heres the good bit in bold for the TL:DR type guys:
On E85 you will make 18% more torque and power all the way from idle to redline than petrol, and thats without taking into account the extra timing you can add and the charge cooling effects (chemical intercooling)!!!


DISADVANTAGES
Availability. Both Caltex and United servos are selling it at the pump, and its as cheap as $1.05/L on a good day. Use this link to find a caltex servo near you. Just tick the E-Flex box and find a local servo.
http://www.caltex.com.au/HelpCentre/SiteLocator/Pages/FindAServiceStation.aspx

It gives a lower range, 20% less per tank, but a tank is 20% cheaper. its almost the exact ratio too, so youll end up just about dead even.

You have to have an aftermarket ecu to run it.

Thats it, for 20 odd percent more power thats all the bad bits.

EXTRA BITS OF INFO YOU SHOULD KNOW

Caltexs E85 changes ethanol percentage throuhgout the year. basically its 85% in summer and 70% in winter. It isnt gradual, you will fill up one day and within a minuet go 'Wow what happened to my tune'. So you either retune, and then when the summer blend comes back you just swap maps in 5 minutes. Or you purchase from united servos which are actually 90% ethanol year round. Or you purchase a flex sensor, this goes in the fuel tank and measures ethanol percentage, with a compatible ecu, it will actually modify the fuel and timing map as you drive and you never even know its doing it, from 0% ethanol to 100% (assuming you give it a 0% tune and a 100% tune).
It IS harder to start on a cold day as it isnt as volatile as petrol, it has a far higher capacity. it takes much more heat energy to convert it from a mist (from your injectors) to a vapour. this is actually why it has a huge chemical intercooling effect within the cylinder just like methanol, but it means on cold mornings its a little harder to start. I strongly suggest going to a strong coil over plug ignition, it will net you plenty of extra horsepower with e85 as well (I could NOT believe the power difference when I went to cops on my e85 setup, it was like a couple pounds extra boost I swear!)

Please feel free to ask any questions here and Ill do my best to answer them.

Dann

[lightyear]

Nice write up. My c.f car was always going to be on e85. But didn't know as much about it as i do now.

[gslender]

Dann, thanks for the post and we should make this sticky. If only you could edit posts and update with further questions as you'll no doubt think "I wish I added that"...

Anyway, I have a few questions...

Do you HAVE to have bigger injectors, or would the standard NA6 ones work fine? I'm about to order my MS DIY PNP and was wondering if I'd need to get new injectors at that time?

Do you need to have a Flex Sensor to tune the car with your ECU, or will the standard O2 sensor work? (but use the stoichiometric ratio of 9.7 instead) ??

Cheers,
G

[Inksta]

Thanks for sharing, Dan. Very interesting stuff. I advanced to 16° yesterday on 98 RON and am pleased with the difference.

I have a (probably dumb) question: You talk about timing advancement as if it is always a good thing. Isn't there a fairly firm limit on how far you can advance? :confused:

[NitroDann]

Do you HAVE to have bigger injectors, or would the standard NA6 ones work fine? I'm about to order my MS DIY PNP and was wondering if I'd need to get new injectors at that time?

The stock na6 injectors should be big enough to run e85 just fine. I believe from memory they have plenty enough headroom. Its easy to find out safely though. You just start tuning it, and keep an eye on the duty cycle guage in tunerstudios, if it gets close to 90% dont rev it any higher and cruise home. Either up the fuel pressure with a fuel pressure regulator or change to bigger injectors.

Do you need to have a Flex Sensor to tune the car with your ECU, or will the standard O2 sensor work? (but use the stoichiometric ratio of 9.7 instead) ??

The flex sensor actually is only used to determine what % of ethanol is in the fuel. The way it works is that you tune on petrol, then flush the system, tune on e85, then the ecu can use the flex sensor to determine what % of ethanol the tank has. so if you ran exactly half petrol and half e85, the ecu would find the exact midway point between the 2 tunes you previously used and use those values to run the car, seamlessly.

You will never be able to tune on the standard o2 sensor, not only will it be rooted, you need a wideband sensor. factory sensors are narrowband and only tell you if its lean or rich, not by how much at all.

Heres the tricky bit.
o2 sensors like the LC1 dont know what fuel is in the car or the air fuel ratio. they only can tell if the engine is running stoichiometric or not. This is known as a Lambda of 1. A lambda of 1.1 might be 16:1 AFR (air fuel ratio) on petrol or 11:1 on e85. The sensor only displays 14.7:1 for stoichiometric because it assumes your tuning on petrol and a Lambda of 1 is 14.7:1 AFR.

With an LC1 you can either tell it your running e85, and it will display stoich as 9.7, or you can just leave it and remember that your aiming for 13:1 afr rather than 12:1 afr like you would on petrol (this is at full throttle areas of the map only guys). This is how I do it as I find it easier.

Dann

[gslender]

Cool. Thanks for the extra tips.

You will never be able to tune on the standard o2 sensor, not only will it be rooted, you need a wideband sensor.

Just to be clear, are you saying the standard o2 sensor would die subjected to E85, but the LC1 would survive ok?

Also, are you saying you tune with the LC1 1st with petrol and then swap to the Flex sensor, or do you add the Flex sensor and run both?

[NitroDann]

Thanks for sharing, Dan. Very interesting stuff. I advanced to 16° yesterday on 98 RON and am pleased with the difference.

I have a (probably dumb) question: You talk about timing advancement as if it is always a good thing. Isn't there a fairly firm limit on how far you can advance? :confused:

As you would know, the timing advance your talking about is STATIC timing, ie its the base timing figure your engine uses as a minimum. The stock ecu on an na6 or na8 actually will advance it all the way to 33 degrees at the right moments, advancing the timing from 10 to 16 degrees static means that you have a total increase of 6 degrees, so when a stock car is at 33 degrees you will be at 39 degrees.

Timing is always run advanced. This means that the fuel is fired advanced in time before the piston gets to the top. Its actually fired as the piston is still moving up!
Because it takes a little while for the bang to get strong enough to matter it has to be fired before the piston is coming down, otherwise it will be too late.

The reason timing cannot be advanced too much is that if it was the powerful part of the band WOULD happen on the way up.
If the engine is hotter the fuel burns faster, so LESS advance is needed (it needs to be fired later, this is known as retarding the timing).
If the fuel has lower octane the timing needs to be retarded, as octane doesnt measure the explosive power of the fuel, rather high octane tells us how slow and even and controlled it will burn, so lower octane, faster burning, it needs to be fired less early, hence retard.
Finally, compression. Higher compression increases combustion efficiency by getting a bigger harder faster bang. being a faster bang, with more compression we need less timing advance (we need to retard the timing)

Clever fellas will have guessed that Boost is actually just the same as extra artificial compression, so it also needs less advance.

Anyways...

E85 has a huge heat capacity, so when it enters the cylinder muc more heat is taken from the charge than from petrol before the e85 is vapourised, so its cooler, and its 110 octane, so even more advance can be used.

As we worked out earlier, your car runs a maximum of 39 degrees advance, and this is about as far as you can go before you get detonation. Ive run mine past 60 degrees on e85 with no detonation at all, and I have lots higher compression than you.

Dann

[NitroDann]

Cool. Thanks for the extra tips.

You will never be able to tune on the standard o2 sensor, not only will it be rooted, you need a wideband sensor.

Just to be clear, are you saying the standard o2 sensor would die subjected to E85, but the LC1 would survive ok?

Also, are you saying you tune with the LC1 1st with petrol and then swap to the Flex sensor, or do you add the Flex sensor and run both?

Im saying thats its unlikely the stock sensor works right after 20 years inside the exhaust manifold.

You use the wideband to tune all the time because it tells you if the engine is running too rich or lean.

The flex sensor simply tells the ecu what the fuel mix is so it can adjust the tume between the 2 maps/fuels. EG if you tune on petrol and e85 you have 2 maps. Then you fit a flex sensor.

If you have 10% E85 and 90% petrol the ecu uses the petrol map but moves all the values 10% closer to those from the E85 map.

You get me?

Dann

[gslender]

You get me?

Yep

[NitroDann]

Ok whos next

Dann

[Inksta]

Thanks Dann. So... earlier spark is possible because e85 burns slower, which means there is more compression because there is more distance for the piston to travel upward from time of spark to time of max compression/explosion?

[NitroDann]

Thanks Dann. So... earlier spark is possible because e85 burns slower, which means there is more compression because there is more distance for the piston to travel upward from time of spark to time of max compression/explosion?

Well theres no more compression.
Static compression is set by the geometry of the engine and cant be changed by changing fuels.

Why more timing makes more power is not fully known or understood, there are general rules but none answer the thermodynamics end of the argument properly.
Now we're talking about combustion dynamics at the microsecond scale. Some of the questions regarding timing Ive asked experts have been answered 'Even F1 engineers dont know that yet'.

In short, no compression is never changed, but more timing generally means more torque/power. There is a limit, that limit occurs when you get detonation, and often 3 or 4 degrees before the limit produces just as good power as at the limit, but 10 degrees short is a huge torque/power loss.

I hope this answers the question.

Dann

[Inksta]

Excellent, yes, very good - I feel less of an idiot! No wonder google didn't give me much joy

Cheers. Now I'm off to learn about megasquirt

[PaulF]

DISADVANTAGES
Availability. Both Caltex and United servos are selling it at the pump, and its as cheap as $1.05/L on a good day. Use this link to find a caltex servo near you. Just tick the E-Flex box and find a local servo.
http://www.caltex.com.au/HelpCentre/SiteLocator/Pages/FindAServiceStation.aspx

I had a look on the Caltex site you posted and also on United's site. According to those sites there's only one Caltex in Newcastle that has E85 and no Uniteds. Is that the case, or are the websites a bit dated in their info?

[NitroDann]

That is currently the case, but with the current commodore a bio fuelled car and many others just about to be released it wont stay like that for long.

Dann