[Diy_efi] Exhaust gas temp

[sc7500]

EGTs used for tuning purposes, on their own, are virtually worthless.

> EGTs used as a tuning aid, in conjunction with other parameters, has
> it's purpose as backup verification.  Generally speaking, your highest
> EGTs will be generated with some form of forced induction, with max
> temps tolerated, dependant on duration.  The reading will also be
> dependant on the temp probe's location.  Max temps of 1550?+ F.
> (or 850?+ C.) can, and have been safely generated.
>  
> ----- Original Message -----
>
>     From: Diesel Services <mailto:dsl at airnet.net.nz>
>     To: A list for Do-It-Yourself EFI <mailto:diy_efi at diy-efi.org>
>     Sent: Thursday, March 31, 2005 1:35 PM
>     Subject: [Diy_efi] Exhaust gas temp
>
>     What do you guys think on max exhaust gas temps, you hear so many
>     different ideas.  thanks Brent
>
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>Diy_efi mailing list
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>  
>
Have to agree with Gary on this - use EGT readings as a REFERENCE, and 
EGR as a BASELINE for your particular application. No two engines are 
the same, all react differently to changes in tuneup, air density, and 
etc. Start slow, make ONE CHANGE AT A TIME, and you'll do fine.

EGTs can show you a dead cylinder, a clogged injector, or a plugged fuel 
distribution hose... but, except for using the info to equalizing your 
cylinder to cylinder egts at WOT, they're only a reference.

Regarding the heat of EGTs; having spent the better part of 11 years as 
a leading developer of ceramic metallic coating materials for industry, 
I have binders full of data on this subject.  45 years in professional 
drag racing taught me a few things too. Here - I'll share.

Here's how a "standard" EGT - to - application chart could read for IC 
engines with a  "standard" tuning job:

- Normally aspirated engine @ 8.5:1 CR - 1050 - 1250 degrees F *
- Normally aspirated engine @ 11.5:1 CR - 1150 - 1550 degrees F *
- Supercharged engine @ 8.5:1 CR, boost @ 6 PSI - 1250 - 1650 degrees F *#
- Turbocharged engine @ 8.5:1 CR, boost @ 6 PSI - 1250 - 1650 degrees F *#

* All info is for WOT or heavy loading w/ gasoline as fuel - see below   
     # Doesn't seem to matter what kind of boost it is

IF you run methanol in any of these situations, we've found that the 
average EGT could go up to 300 * F higher, due to the increased BTU 
potential of alky, and the "afterburn effect" that can be caused by 
exhaust dilution with bypass alky. Not that bad, really - if small holes 
are drilled into the headers to provide an auxiliary post combustion air 
source, a secondary ignition can occur down pipe which helps complete 
the burn cycle and evacuate the exhaust port.  Sounds pretty weird in 
action, tho... almost like a set of 180 degree headers. If you're too 
young to have heard this rip / tear live, talk to a drag racer and ask 
'em about how the Bean Bandit used to sound... special thanks to Smokey 
Yunik for telling me about this back in 1979.

NOW - if you want to talk about nitromethane in a supercharged [25 - 30 
PSI] application, all EGT rules fly out the window.  "Normal" Top Fuel 
EGT sensors see anywhere from 1680 to 1900 * F in a 4.5 second 1/4 mile 
pass... and people wonder why it's so hard to keep polished ceramic 
shiny in this type of environment... especially when you consider that 
the polished ingredient in most all ceramic header coatings [aluminum] 
oxidizes at 1475 * F.

Just as a teaser for you Salt Flats fiends - the max boost reportedly 
used by record holders at Bonneville these days is around 22 - 25 PSI. 
Seems the old timers have a speed secret they finally let outta the 
bag... heh heh heh.

Hope this helps. If nothing else, it may create a good base for discussion !

Best
-- 
B.T. Corneto
[The Mad Coater]
Occidental, CA 
 
"United We Stand - Remember 9-11"