Tom,
Just wanted to thank you for your help with my emissions questions. I'm
sending this post directly to you, as for some reason I'm having trouble
posting to the digest today.
Harvesters,
On the third try, I finally passed my emissions test yesterday. Last year
it took me five tries, so I guess I'm improving as a mechanic. :)
My problems (both this year and last) are all related to carburetion. That
is, the only measure I was failing was CO. I thought it might be
interesting or helpful to show my test results, the changes I made, and
what effects they had on the next test. This pertains to a '75 Scout II
with stock ignition, 345, 727, and the Holley 2210c carb.
I hope this comes out all right with the tabs and all.
First Test - Timing at 12BTDC, jets: one .532 and one .50, high (91) octane
gas
%CO2 %O2 HC (PPM) CO% NO (PPM)
(Max / Measured)
15mph 9.8 0.6 510/175 3.78/7.08 3752/816
25mph 10.9 1.2 490/152 3.68/4.84 3552/704
After the first test, I retarded the timing back from the 12 BTDC where I
usually run to about 2 BTDC. I also changed out the power valve for an old
one left over from a previous carb rebuild that I *thought* was good. I
also put in a new air filter, which I needed anyway.
Second Test
%CO2 %O2 HC (PPM) CO% NO (PPM)
(Max / Measured)
15mph 7.8 0.7 510/260 3.78/10.05 3752/525
25mph 7.9 0.7 490/278 3.68/9.94 2524/507
These results led me to believe that: a) retarding the timing provided no
benefits, as seen by the rise in HC numbers, and b) the "new" power valve
was worse than the old one. I advanced the timing back to about 14 BTDC,
and installed a power valve from a new GP-Sorensen rebuild kit. I also
changed out the .532 jet for a .50. Now I had two .50 jets.
Third Test
%CO2 %O2 HC (PPM) CO% NO (PPM)
(Max / Measured)
15mph 11.9 .07 510/132 3.78/3.20 3752/1254
25mph 12.9 1.4 490/128 3.68/1.15 2524/2135
It should be noted that these tests were conducted in Salt Lake County, and
that the only measures that "count" are the HC and CO. You can bet they'll
add NO in the next couple of years, though.
Strange aside: one the first and third tests, they listed my exhaust as
"Single". On the second test, they accurately had it as "Dual." Does
anyone know the procedure well enough to know if this matters? I assume on
dual exhaust, they just average the two tailpipes, or just test one. I
didn't watch close enough during these tests to see if they used 1 or 2
sniffers. I don't think this would have an affect, would it?
Something occurred to me as I brainstormed for ways to bring my CO down.
Would oxygenated gas help? That's the whole purpose of MBTE, isn't it? To
reduce carbon monoxide emissions? If it does help, then people in Utah
County who have their registration renewal in the winter have an advantage,
because Utah County uses oxygenated gas from November through February.
And in CA, don't you have oxygenated gas all the time? Maybe I should have
roadtripped out to Cali to get some "emissions gas" for my test.
Also, does octane have any effect? I guess I don't really know what octane
means. Any chem folks want to enlighten me on these issues?
rob hughes -- passed!