[Diy_efi] A/F mixture, EGT and engine damage
gas- at charter.net
Tue May 17 17:55:54 CDT 2005
> The table I posted was running with a narrow band O2 sensor.
> I am pretty sure this is the worst case EGT as 1663 F is the
> highest I have ever seen on this bike.
Are you stating you are using a NB O2 sensor to do your tuning
with? *IF* that is the case, you can forget about obtaining
reasonably accurate info, as far as AFR is concerned. Figuring
you are using the more common 'Nernst' cell sensor, whether it
is of the single or multi wire variety, (single being worse) the sensor
will be too temperature dependant/influenced, to depend on for
worthwhile data. The NB sensor is designed to be accurate,
(as a glorified switch only), around .45 volts, which is the
stochiometric ratio of 14.7. The further (either direction) from
14.7, the more error prone (and unreliable) the sensor becomes.
If you at all serious in regards to achieving accurate data to use
for diagnosing, a WB sensor and controller is a necessity.
> As far as cruise I have experimented with running LOP 15.6:1
> or so. I get some surging at lower speeds and some pretty high
> EGTs. A/F seem to be all over the place(~14.5:1 - ~17:1).
Again, *IF* this is with a NB, I wouldn't give ya 3¢ for the accuracy
of that data. Accuracy aside, even for the use of comparison, as
that sensor is too influenced by temp, I couldn't/wouldn't rely on it.
----- Original Message -----
From: "Tim Marsteiner" <tmarstei at yahoo.com>
To: <diy_efi at diy-efi.org>
Sent: Monday, May 16, 2005 9:50 PM
Subject: Re: [Diy_efi] A/F mixture, EGT and engine damage
> Yes, for this engine the 13.2:1 is a good deal leaner
> than need be at wot. I have run as low as 11.5:1 at
> wot with good power and EGTs below 1400. That's a no
> At cruise it gets a bit more complicated. The table I
> posted was running with a narrow band O2 sensor. I am
> pretty sure this is the worst case EGT as 1663 F is
> the highest I have ever seen on this bike.
> I guess my question was not so much if either of these
> is ok, but rather which might be causing the most
> problems. What I am hearing is that to optimize engine
> life I ought to eliminate both and as long as I stay
> above 10:1 or so I should be ok in terms of wall wash.
> Here are the results of my fix (pretty fast huh!?:). I
> attacked both issues. WOT stays below 1400 F and
> cruise stays below 1450 F.
> I will be honest though I have not seen a huge
> reduction in cylinder head temps. Perhaps 10-15 F
> reduction. It does take longer to heat up though. This
> agrees with John Deakin's article "Mixture Magic".
> So I think the WOT part of the above tune is good
> except for maybe some fine tuning on a dyno and maybe
> some more ignition advance.
> As far as cruise I have experimented with running LOP
> 15.6:1 or so. I get some surging at lower speeds and
> some pretty high EGTs. A/F seem to be all over the
> place(~14.5:1 - ~17:1). Probably due to the ECU using
> alpha-N control or perhaps that pesky IAT heat soak
> problem. I will keep working on this to see if I can
> stabilize the mixture LOP and lower CHT a bit as Mr.
> Deakin's results indicate.
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