[Diy_efi] The Hunt effect

[John Gross]

I'm assuming that you lose power with the oxygenated blend because of the
computer's adjustment for the blended fuel?  All else being constant, you
should make more power on the oxygenated fuel, assuming the same lambda is
maintained in the cylinders, which in the case of the oxygenated fuel, means
that you have to deliver more fuel to maintain the same lambda because of
the fuel's oxygen content, which is one of the reasons for the expected
decrease in mileage.  Of course, all of this goes out the window if the ECU
is actually changing it's calibration to a more conservative fuel-air-spark
map.

-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org] On
Behalf Of Ulmer, James D - Denver, CO
Sent: Tuesday, October 04, 2005 12:15 AM
To: diy_efi at diy-efi.org
Subject: RE: [Diy_efi] The Hunt effect

In our case (Denver is a non-attainment area) we get normal gas in the
summer and oxygenated (alcohol blended) stuff in the winter. The blended
stuff always drops power and mileage some. In my Caddy, cheap gas never
knocks but the sophisticated engine management computer backs the engine
down so it will run on almost anything just not too well. I proved to
myself that mid-grade is an economical choice but full premium offers no
noticeable benefits.  With computers and knock sensors, you can't use
your ear any more, you have to run controlled tests to tell what's best.

Big Jim

> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]
On
> Behalf Of Dustin Lof
> Sent: Monday, October 03, 2005 9:57 PM
> To: dh at busb.com; diy_efi at diy-efi.org
> Subject: Re: [Diy_efi] The Hunt effect
> 
> I have never heard anyone say more octane produces
> better mileage, I was always told to burn, and to
> reccomend to my customers the lowest octane it wont
> ping on....?  what is the ethanol content in the 87
> v/s 89.  Around here it is 10% corn ethanol in
> everything but the 91 and your not suposed to burn the
> 91 unless your driving a collector car or a snowmobile
> and most snowmobiles are jetted to run on 10% now too.
>  I am just wondering if the alchol content is what is
> effecting the mileage.  I know its eating up a lot of
> fuel pressure regulators.   There is also the r*m/2
> factor which is how octane is rated the r factor is
> what the guys in white coats in a lab say the octane
> rating is the m is how it actually performs in a
> single cylinder test motor.  If one of those numbers
> is skewed, for example crappy gas doped up with an
> additive package it will make your mileage compairson
> way off.  it is all way more scientific than all this
> but that is all I remember from the one day we talked
> about this in college so please dont ask me to explain
> in any more detail.  just my $0.02---Dustin Lof
> 
> p.s. last week Minnesota mandated all diesel be 2%
> bio-diesel.  Made from soybeans.
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> 
> 
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