Page 1 of 3
moving to E85
Posted: Tue Sep 30, 2008 6:26 am
by duncan
Some of you will know that I am moving in this direction with the current tune based on mixing E85 with normal pump fuel similar to the way that some (incl me) have done with methanol.
Reasons:
Why is E85 a better fuel ?
Ethanol and is a very turbo friendly fuel for many reasons.
1. It has a much higher evaporative cooling power than gasoline so the intake air charge in the cylinder is significantly cooler that it is with a comparable mixture of gasoline --- that means higher VE.
2. Its octane as blended in E85 is about 100, its blending octane when added to gasoline is rated at 118, so it is a very cost effective octane booster.
3. Ethanol burns faster than gasoline but has a slightly longer ignition delay during the slow burn phase of combustion so the engine does not do as much negative work fighting rising cylinder pressures due to large ignition advances. The total ignition advance for E85 is almost identical to the ideal advance for gasoline so it does not cause the ECU problems when you mix them.
4. At proper mixture you actually are releasing more energy in the cylinder due to the higher quantity of fuel you can burn. ( Ethanol can burn effeciently at much richer mixtures than gasoline can) That means about a 5% increase in energy release all by itself.
5. Peak combustion pressures are actually lower for ethanol than for gasoline but the cylinder pressures stay higher longer, so you have more (longer) crank angle that is usable by the engine. This lower peak cylinder pressure also helps with detonaton control.
6. It will, at proper mixtures lower EGT's by around 200 deg F, but due to the higher quantity of exhaust gas products it produces you do not lose any spool up (in fact I would wager spool up is better).
This all sounds good but now that I have had a chance to really compare the two and adjust the map to adapt to it. (it needed massive changes to timing and afr's - way beyond the quick map that I ran at Gary's when on a 10% mix).. I am excited about the real-world effect of this fuel and have been able to notice the difference in the drive characteristics.
I filled up a couple of jerry cans from morrisons and have mixed it now at 20/80 with tesco 99 and love it
The lower figures are from between the 490 bhp runs at APT and Zen, the higher figure is on sunday using the adapted map. (all are wheel figures and using the same stretch of road, same fuel level, same gear and almost identical ambient temp)
I will be getting it properly dyno'd this week to see whether the dyno shows a similar improvement.
Posted: Tue Sep 30, 2008 7:59 am
by ScoobieWRX
Duncan, this is really interesting stuff. I have a Morissons near me and was thinking of doing the same to get a bit more go with the current VF35.
I take it this time you mapped in more timing advance and made AFR's a bit richer. Does this mean you can run a bit more boost as well instead of timing if required, or a bit more of both with no ill effects??
Also, when you ran a 10% E85 mix before you made any changes to the 99RON map how did the car run straight off. Was there a big difference? Did the ECU automatically dial in a bit more timing advance than when using 99RON by itself?
Also was thinking about a 20% mix. How do you think that will affect things?
Posted: Tue Sep 30, 2008 8:34 am
by duncan
It wont dial more timing advance automatically unless you are running with the IAM below the optimum 16.
Had to dial in more fuel - straight e85 needs about 30-35% more fuel. So apportion that according to the mix you run but it ran fine on the std map at 10% mix. It depends on how much IDC you have left as to how much room you have.
Dont think in terms of AFR though.. work with lambda :thumb:
Like methanol, it does need more advance though and it has been quite revealing as to just how much I could add to get it closer to MBT. On the dyno on thursday to see if I can fine tune this element of the tune.
Posted: Tue Sep 30, 2008 10:10 am
by ScoobieWRX
I need to get my head around Lambda, have been using only AFR so far. What are the advantages of working in Lambda?
My IAM never dips below 16 but i noticed that on V-Power i see less knock advance than with T99RON. V-Power c.10.5, T99RON c.12.5
I'm going to try a 10% E85 mix and see how i get on with that. Sounds like you're getting on really well with it so got to be worth a play.
I'll take a couple of 20ltr jerry cans full of E85 with me to Scotland and have a bash up there but i will have to mix it with V-Power unless i take a 70mile round trip to Perth for Tesco 99RON. Hazel's sister has 2 big sheep farms in the highlands and the super quiet roads around there are ideal for a bit of mapping and logging. Should be fun.
I assume you will be running a mix for TA at Snet. Will be interesting to read your findings on that. Nice one!! :thumb:
Posted: Tue Sep 30, 2008 10:22 am
by duncan
There is no such thing as knock advance in the subaru maps. The Advance map shows the additional advance (added to the base timing & some other factors) that can then be scaled down according to the happiness scale (IAM).
If this advance map calls for 12.5 degrees and it is only adding 10.5 deg then it is detting and taking 2 degrees of timing out. You can still get positive knock correction according to logging and yet it has taken huge chunks of timing out for knock.
If base timing is 10 degrees and advance is 12.5 degrees - it should run 22.5 degrees total timing if all is well with the map. If it runs less than this, there is something amiss with fueling or timing or another issue.
Lambda is consistent irrespective of fuel used.
Posted: Tue Sep 30, 2008 10:51 am
by ScoobieWRX
This is another reason why i need a wideband and proper knock detection. I'll need to keep a close eye on that.
Cheers
Posted: Tue Sep 30, 2008 11:35 am
by duncan
Thought you had sorted those out?
Didnt you order one a couple of months back?
Posted: Tue Sep 30, 2008 12:25 pm
by ScoobieWRX
Nope. I never got round to ordering in the end and i had the funds as well to get both. Typical of me at the moment and i was going to get an LM-1 and a similar knock detector to the one with the cans and everything. You only buy these things once so may as well go for the best i could afford at the time.
My own fault really but i have a lot personal crap on my mind at the mo including looking for something new to do. Electronics recruitment has been hit somewhat by current economic circumstances and funds have taken a hit as a result, but although i'm not shutting the business down i need something else to do to earn some dosh and prop things up until the situation improves.
Right now i have to watch what i spend and i'm only going to Scotland to help Hazel's sister out and look after her farm while she takes her first holiday with the kids in 3years, otherwise i would stay home and save the money instead but these things have to be done to help family out
Posted: Tue Sep 30, 2008 12:32 pm
by tomcat
Sounds good if you have aftermarket managment
Question
Would I be likely to see any gains using a 5-10% mix of methanol -without ignition/fuel changes?
(if it was lean I could alter fueling to suit) but my ignition is not adjustable on my std ecu
I already have some methanol already :?
Posted: Tue Sep 30, 2008 12:46 pm
by duncan
I feel a little uncomfortable advising to be honest but I would say that from my own experiences on methanol it gave a little more performance and a degree of det mitigation without any other changes.