[Shotimes] RE: 10% Ethanol and A/F ratio

[Ron Porter]

Yes "IF" the fuel & timing tables have enough range to compensate. Fuel
economy will still suck eggs, though.

 

The whole purpose of the alky exercise was to 'fake out" cars with
carburetors for emissions reasons.

 

FWIW, I read something the other day on a semi-related note.

 

The press has been talking about GWs SOTU speech about the ethanol thing.
Read something the other day that tied in to an earlier article, but anyway,
it claimed that a car on straight ethanol has 70% of the efficiency of a gas
motor (IIRC, that's way too high..50-60% max).

 

Anyway, this article claimed that better tuning of the cars on ethanol would
get the efficiency up to 80% (!!!!) of a gas engine. Besides not believing
that, I was trying to think "how" a car could be tuned to raise it's
efficiency on alky rather than gas. Seems that any tuning tricks that would
work for ethanol would also work for a gas engine. I dunno, maybe I'm
missing something...or it's just another clueless reporter getting fed a
line of bull.

 

Ron Porter

 

  _____  

From: Paul Nimz [mailto:pnimz@v8sho.com] 
Sent: Tuesday, February 14, 2006 8:48 PM
To: `TechSho@topica.com; `V6 SHOtimes; `V8 sho@v8sho.com
Subject: 10% Ethanaol and A/F ratio

 

I've always argued with Ron the fact that a 10% ethanol fuel will not
affect performance due to the lower BTU content as long as the injectors and
fuel pump are up to the job.

 

What I have found on my '97 running an 89 octane/10% ethanol fuel is the WOT
fuel tables are way lean and the timing tables are way low with the SCT
tune.  Both can be, or need to be increased about 10-15% to accommodate the
fuel.  Ethanol also allows a hotter spark as it will increase the octane.  

 

Around me only one station sells straight gas and that is 87 octane.  All
other brands/grades are 10% ethanol, 87, 89, 93 octane.  Casey's sells their
89 octane as the low end, as they should due to the state tax breaks on
ethanol, but their 87 octane straight gas is the mid priced fuel.  I feel
the 10% alky mix must raise the octane by 2 pts to 89.  So I deduce all
90/10%  87oct mixes out there start out as 85 octane fuel.

 

So what I have to log or know now is if the Long Term Fuel Tables write into
the Base Fuel Tables.  If so the change can be logged and compensated for
with a few tweaks.

 

I've also read that a 15.6 or so A/F ratio is the best for fuel economy when
cursing.  This would require an off set to the O2 voltages when the PCM is
in closed loop somehow.  It appears that the SCT Advantage software is quite
limited compared to the Tweecer stuff, or so I read.  This is due to the
limited decompiling of the SHO OBDII code by SCT, or so I surmise.

 

Paul