I thought the turbo guys would be interested in this. This was posted on the RX7club forum by a local Houston club member named Chuck. Hopefuly he won't mind it posted here as it is good info.

This year after May, gas is no longer to contain MTBE as an octane enhancer.
What are different brands doing to enhance octane in place of it? One way is the 10% alcohol blend that is showing up here in Houston. I mostly use Chevron, and recently they have posted signs on their pumps stating that their gas may contain up to 10% ethanol.

For years my car had been running the AFRs that I had tuned for. But since May, I noticed that my smooth lean idle became rough. I had to add 3.5% more fuel to get it to smooth out again. If 10% ethanol is added, it will lean out AFRs due to it being less dense.

To test this, I added 3.5% more fuel to my boost area for over 10PSI. Then I went
logging with my wideband and DATALOGIT. With the additional 3.5% more fuel,
my AFRS are what they were last fall when I last logged AFRs.

If you are running 11.2 AFR for 14PSI boost like I am, this new ethanol induced 3.5% leanest; is leaning it out to 11.6 AFR.

This could be bad for your engine! If you tune for non-alky than get alky or vice versa, your tune will be off. I would like to keep it constant especially if traveling.


For the curious, here's a map of different formulations of gas around the country courtesy of Exxon. It was current as of May.

http://www.exxon.com/USA-English/Fil...p%20100102.pdf

If you want to know what all of this means, go here.

http://www.eia.doe.gov/oiaf/servicerpt/fuel/rvp.html

 

The DC area has been constrained by 10% ethanol for a long time.
Here in Phoenix, we have a version of Cali's CBG.
Its seasonal, too.

It all sucks.

Tune as rich as you can until it bogs then go back a point.
Will it produce maximum power? No.
Will it continue to make power for longer than max power. Yes.

 

That formulation map is interesting. Yesterday I drove through a Conventional & N RFG W/ Ethanol zone in Pennsylvania. The price difference for a gal of 87 was as much as .50/gal within the same state.

 

For an NA owner, then does it follow by the same reasoning that (unless our cars have a way of determining the new mix - I know that some cars do, but I don't know that the 8 does):

RESULT FOR NA: w/less dense fuel, we'll get an automatic leaning of the mixture overall.

Therefore, CLOSED LOOP, no dif, adjusted for.

However, OPEN LOOP, automatic LEANER mixture, and esp with the reformulations that now have a higher energy density, a small 'supercharging' effect (higher energy/same amount of oxygen).

Sounds like the lazy mans "dream-come-true" tuning method !

 

You noticed if there is less soot on your tail pipes? I have not been paying attention to that myself. Wouldn’t a leaner mix cause less tailpipe soot?

 

Only if you run open loop most of the time. Sounds fun, but a bit impractical!!!

Otherwise, to early to tell as this only started 6/1/06... also I don't know what "S RFG with ETHANOL" means as far as reformulation goes (where I am).

 

So in order to wean ourselves off oil...we'll be burning 3.5% more fuel.

Makes perfect sense. Thanks, corn lobby!

 

NYC has been using 10% ethanol for like a LOOOOONNNNNNNGGGG time.

this is gay, every states have different kind of gas.

 

I heard that because ethanol is very water soluble if you have any moisture in your tank it will cause the ethanol to mix with it which can screw up your engine. How am I supposed to pwn n00bs with a busted engine?

 

i thought the ethanol would absorb moisture therefor gettign it out of your tank. haha granted it gets out by being burned in your engine.

 

as for NA cars with this..i doubt we would need to add 3.5% more fuel as our engines aren't boosted (turbo's need more fuel for the added air being shoved in them)...bu tlet's say even if we do need to add 3.5% more fuel...can't the stock ecm change the fuel map +-35% or somethign like that (i'm not sure for mazda but toyotas will change fuel trim up to 35% befor throwing a code, i've seen toyota ecm's change trim up to 40%
)...so it should be a big deal for us....well as long as the car is in open loop mode and using values it gets from the a/f sensor to tune the fuel trim.

 

In closed loop mode your car will compensate. For boosted cars with custom ecu's tunes, remember they are running in open loop under boost. Some ecu's are set up to run full time in open loop. There is no compensation at this point.

 

I think you meant to say... "in closed loop it's no big deal."

In open loop (WOT) it may help us a bit... as that's where (blindly used) ECU maps are pig rich (and there is no compensation or checking on actual values....aka why it's called 'open loop') ?

 

^^^Could you please explain "open loop" vs. "closed loop" I'm pretty mechanically illiterate.

 

closed is when the ecu uses maps for fuel, but is watching the O2 sensors and adjusts to suit conditions. This is normal operating conditions.

open is when you go say 80% to WOT and the ECU uses maps (usually rich ones for safety of the engine under these extreme conditions), but stops trying to regulate or adjust the a/f ratio.

 

but the 8 uses the Fuel trim established during closed to trim the open loop

 

hehe yes i mean tto reverse that.. lol well you guys got the point

 

For N/A cars it means your mile per gallon go down and you pay more for gas as Ethanol is more expensive per gallon that gasoline. So basically you use more gas and spend more for it. If we are forced in the future to go to E85 your going to end up spending well over twice for your fuel.

It's a stupid solution to our oil usage by greedy companies like ADM and farmers. GM is also pushing it as a last ditch attempt to save themselves.

Ethanol also isn't particularly good for your engine either.

If you don't have it mixed in your gas you soon will unless you call your state and federal representatives and complain.

 

Ethanol itself isn't bad for the engine. It actually burns cooler. The thing that is bad about it is that it absorbs water easily. It'll suck the moisture right out of the air. It's water in the system that eventually corodes everything.

 

The bigger problem - now that it is mandated, is that 'they' (Washington politicos) passed the laws, but didn't bother with figuring out how to put in place the needed infrastructure to transport and distribute the ethanol where it's needed. It's a big country, the ethanol is in the midwest plains, and it has to be added just prior to local dispensing due to the problems w/mixing and storage of this combination of fuels.

Therefore California, Texas, and the east coast for the most part. Since most trains tracks are long gone, trucks carry the stuff around. Now that's smart.... how many million gallons of the stuff do we need anyway????

Then add the cost and problems in using it.....storing it...engines efficiency

 

I always run better when I put 10% alchohol into my system. However, I tend to crash more often. Did the politicians account for that?

 

Doesnt Brazil run their cars purely on eth? I believe there are RX8's running on eth. Wouldnt we be able to retune to do the same?

 

Yup my engine burns moisture out of the air all the time!

 

Just noticed we have 10%ethanol fuel available here now .

It is rated at 98octane (approx. 93 US) .
The fuel I currently run is 98 octane as well . Just wondering if the ethanol mix would be any better/worse as far as detonation goes ?

 

Down here in florida I've already seen the Ethenol stickers everywhere. So I'm already tuning for it