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.

Does anyone know what the different brands are doing to keep 93 octane without MTBE?

 

Great, things get even more complicated for us. What a load of crap.

 

No joke, I feel sorry for the people who pay to have their cars tuned. Now they'll all need new tunes !

 

With a power fc, you can just go to the PIM volt menu and take the fuel from 100% to 103.5% at each 1000 rpm point.

 

At least it'll keep tuners employed!!!

 

With the PFC I went to the PIM volt and did 103.5% for 4.0 and 4.5 volts which covers 10+ psi of boost.

 

How often do you have to get those things re-tuned?

 

I check mine twice a year, summer and winter.

 

People switch their setups so damn often with these cars that the tuners make a killing anyway

 

Here is a USA fuel formulaion map from Exxon dated May 2006.

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

 

Chuck I cross posted this over to the 8 forum to get the turbo guys there too. I hope you don't mind.

 

Down here in Hawaii, that E10 crap is mandatory and in place for a few months now.
All the stations all should be running it.

Time to go stocking up on Toluene and MEK from Home Depot?


-Ted

 

Here is a site about Reid Vapor Pressure which shows on the fuel map as RVP.
Containes other info about ethanol and the btu differences between straight gas and 10% mix.


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

 

IM still surprised the toluene bug hasn't kicked in yet, its cheaper than race gas for most people, and its unleaded i have about 20 gallons sitting in my garage that i mix at a 50/50 ratio with the C16 i run when running 20+ psi. I usually also run at least a 15 percent mixture with pump gas when im running less than 20 psi.

I know a lot of people are still not sure about running the stuff, but i have done some long term (18+ months) degradation tests on fuel line, and other various parts, and they have all help up very well. I also have been running toluene mixed with pump gas for a long while now, with absolutely no problem.

Adam

 

So, say you wanted to run 17lbs, with pump gas, what kind of AFRs and % mixture would you run with toluene?

One positive about having to add 3% more fuel is that the guys who run 850cc primarys and are running rich, will now be a bit leaner at idle. CJ

 

Interesting.. Any good reading info. Anywhere?

 

yeah. There is actually plenty of good write ups on this. Do a search under toluene and see what comes up.

 

I did a speriment like in chemistry class and ethanol drops sank in a testtube of gas. That means ethanol is more dense then gas.

adding ethanol lol

 

And your fuel pump is at the bottom of the tank

 

Still got any plans to send me my UIM and TB Dave?

 

Good call!!! I would expect 5% more fuel for 10% ethanol though since it burns 2x as fast so 10% of that should equate to 5% more fuel....

 

We do not care about weight density which is what you are talking about.

We are talking about BTU density. Ethanol is BTU less dense per volume than gasoline. To produce the same power with ethanol as you would with an average gasoline mix, you need to flow about 40-50% more ethanol.
So the 10% ethanol/gas mix leans out you gas tune by an estimated 4-5%.

That is why tuners talk about having to run larger jets or more injector timing when running or adding ethanol/methanol.

GAFA GAFA!!

 

Chuck, I have to ask--what does gafa gafa stand for?

 

oh come on. people with half a brain should know what that means. but again, I don't know either so I have less than half a brain...... LOL

 

ok i'll bite,

German American Fellowship Assoc

or

Geometric and Functional Analysis