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Burned Exhaust Valves on 1.0L G10 Engines; GM technical notes regarding Geo 1.0L G10
Topic Started: Nov 22 2011, 09:33 PM (4,847 Views)
nerys
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Grr

I would say 3tech has more "real time in fixing real cars in the real world"

SO why not advance the timing and only retard it when you need to run it through emissions?
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Bad Bent
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Facetious Educated Donkey

:gp Which is what I plan to do if I get out of central Idaho.

"if you describe following original specifications for setting base ignition timing to 5 degrees BTDC which results in peak combustion pressure occurring around 14 degrees ATDC under all driving conditions with the exception of idle and DFCO "

So we remove any advance mechanism like vacuum and the ECU. Then we set the timing at 5o which "results in peak combustion pressure occurring around 14 degrees ATDC under all driving conditions...exception of idle and DFCO"

It makes me wonder why I have one of these Posted Image and an ECM

But it allows the ECM to change the 5o - 14o relationship based on mapping, rpm and any data it gets from the sensors. Checking out http://www.miata.net/garage/KnowYourCar/S10_Timing.html there is a good explination on what happens ATDC:
15. Combustion actually commences while the piston is on its upward journey. The time it takes for the flame kernel at spark plug to expand to the top and sides of the chamber permits the piston to pass top dead centre before it receives the flame front. The expansion of the gasses during the period from ignition point (BTDC) to flame front reception (ATDC) increases the volume in the chamber and effectively creates higher compression.
16. Now we can see why it is that when the timing is advanced the higher position of the piston at 11 degrees ATDC (compared to 15 degrees ATDC) increases the effective compression and gives more power on the downward stroke. That equals more torque. See rule number one above.


The risk in advancing the timing is that the flame front (the increase in pressure) from the burning air/fuel mix strikes the piston head before, at, or too close to TDC to create the optimum forward rotation of the crank.

If the downward force reaches the top of the piston before the piston is able to react with a downward motion then the force is directly to the crank, rather than to the rotation (a bit like how landing on a stiff leg transmits the jar to the hip).


So if 5=14 then 8=11, 10=9, 15=4 and 19o BTDC would be :die :x

BTW, my hood sticker says 6o for my engine so you are saying I should actually retard my timing. :scared
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billy508
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billy508

@ Mwebb ...........It really dosent help the forum very much when you makes statements such as "so anyone
who
doubts that
"oil quality or viscosity has anything to do with it"

needs to study and learn and get some real time in fixing real cars in the real world
imho
again
Some where along the line you seem to assume that you, and you alone, have all the definitive answers to all automotive issues. Sounding arrogant and belittling to many of us who have spent many years in the mechanical world does not set well with me. I have stayed out of the oil debate because my "real" world results differ from yours. The tone and condescending style of your posts are not appreciated by me. :banana :banana :banana
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nerys
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Grr

he is arrogant but thats part of who he is. his info is usually good so we just jab at the arrogance for fun now and then and take the good bits as they come :-) hehe
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Alpine
1020cc G10 GOML

i found out why we burn valves!

http://en.wikipedia.org/wiki/Murphy%27s_law
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clarkdw


Alpine
Nov 26 2011, 06:28 PM
i found out why we burn valves!

http://en.wikipedia.org/wiki/Murphy%27s_law
That explains an awful lot more than just burned valves. Now I know why I have hemorrhoids, why my fridge stopped working and many other things. :D :D
Edited by clarkdw, Nov 26 2011, 07:43 PM.
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