Fergus,
HC and NO are usually inversely related. If one goes up, the other goes
down.
High HC is usually caused by running rich. High NO is usually caused by
high combustion temperatures; advanced timing, running lean, etc.
This suggests that you are not getting a complete burn. Especially when it
cleans up at higher RPM's when timing isn't as crucial.
I'd change the plugs, cap and rotor and check the wires before your next
smog check.
Steve
70' 1600
----- Original Message -----
From: "O'Farrell, Fergus" <Fergus.OFarrell@ngc.com>
To: <datsun-roadsters@autox.team.net>
Sent: Wednesday, April 23, 2008 7:54 AM
Subject: [Roadsters] OT: daily driver smog check results,suggestions for
next year
> Okay engine exhaust gas experts, I took my car in for a CA smog check
> yesterday (meaning they put it on a dyno and run it at 15mph and 25mph),
> and figured it'd pass no problem, so while I due religious regular
> maintenance, it does have 102k miles and I haven't changed the plugs in
> 3 years or so. (~45k miles)
> Brand new air filter. Toyota Tacoma 3.4L V-6 (5GZFE engine, from
> memory), auto trans, 2wd, 4 door (like that makes a difference).
>
> So here is what I got for results: (it passed, but a few were "by a
> hair", see below)
>
> 15mph, 1729 rpm: %CO2: 15.0, %02: 0.0
> 25mph, 1751 rpm: %CO2: 15.1, %02: 0.0
>
> And the 3 tested (pass/fail) readings
> Measured------- Average for Passing Vehicles----------Max Allowed
>
> HC (ppm):
> 15mph: 47------4-------51 (**)
> 25mph: 19-------4-------35
> CO (%):
> 15mph: 0.14-----0.00------0.65
> 25mph: 0.02------0.01------0.79
> NO (ppm):
> 15mph: 510-------18-------512 (**)
> 25mph: 168-------16-------765
>
> The two with asterisks are the ones I am most concerned about. Any
> suggestions on what to do for next test (reg for 2010)?
>
> Note: on a sideline, on the recent Iron Bottom, I met someone who was
> driving a '79 stock midget, and when I asked him about smog, he said
> he'd get "the new additive from CRC that nearly guarantees passing
> numbers". He intimated it was like "solvent in a can", not sure, never
> heard of it, but thought I would throw it out there as an idea /
> research opportunity for those who have one "on the edge".
>
> Thanks for the help, looking forward to seeing y'all in Solvang,
> Fergus O, 69 2000, HB, CA
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