Thread: Desmog
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Old 12-15-2010, 11:27 AM
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subzali subzali is offline
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Join Date: Aug 2005
Location: Denver CO
Posts: 8,619

I think I have something figured out that I'm going to try. I went through the emissions manual and picked out the various pieces of the system.

Exhaust Gas Recirculation (EGR): recirculates exhaust gases to lower combustion temperatures and reduce NOx emissions. Also allows a more lean fuel/air mixture at cruising speeds. I don't like the idea of putting exhaust back into my combustion chamber, and I can adjust the fuel/air ratio of I need to. Off comes the EGR pipe, EGR cooler, and EGR valve. The EGR valve is vacuum controlled, so I can cap that hose.

Air Injection (AI): air pump injects clean air from air cleaner into exhaust via the air rail to burn HC and CO in the exhaust. So actually it's not a "smog pump." Anyway, totally emissions related. Also, smog pumps sometimes have a tendency to freeze up. So off it comes along with the Air Bypass Valve (ABV). Plugs in the air rail holes.

Spark Control (SC): delay vacuum advance to minimize NOx and HC. To me, that sounds like detuning the engine. Remove VTV, VCV No. 1, VCV No. 2, VSV, BVSV, vacuum surge tank, orifices, and connect distributor vacuum advance straight to early ported vacuum (advance port on my '78 carb). This VSV also controlled the EGR valve, so now that hose is completely gone.

Hot Air Intake (HAI): Keeps intake air temperature hot even when it's cold outside. I haven't fully figure this out yet, I know that it's a thermally controlled valve on my air cleaner housing. I'm not sure where it draws the hot air from; I'll have to look into that. This may or may not be worth messing with. At this altitude I would imagine that cooler, more dense air would be a good thing.

Evaporative Emissions Control (EVAP): draws fuel vapors from fuel tank through charcoal canister and directs into intake. Controlled by VSV (different VSV than SC system). This isn't hurting anything, and is probably more beneficial than anything, so I'm leaving it.

Throttle Positioner (TP): this keeps the throttle plates open just slightly when decelerating to keep the mixture from running real rich, reducing HC and CO emissions. It also can help prevent backfiring, both of which sound like a good idea to me. It connects to the VSV for the EVAP system, which I've already decided to keep, so that works out great.

That's about it; I will get a diagram up later. But basically I will have a vacuum line running from the dizzy to ported vacuum on the carb, and two vacuum lines running from the driver's side fender (where the VSV is located): one to the TP diaphragm on the carb, and the other to manifold vacuum, which draws through the charcoal canister as well as activates the TP diaphragm. The other vacuum port on the dizzy will be capped, the other vacuum ports on the carb will be capped, there will be one empty electrical plug on the driver's side fender, and the BVSV will not be hooked to anything (or will be replaced with a plug).

EDIT: BTW I found a good series of info on US dizzies from Jim C....
Here is the real deal on 49 state US distributors from the beginning of time.

All early - 1987 have mechanical advance. Curves vary from year to year.

Early - 1968: Xtra small distributor, vacuum advance (correctly called "non-smog", also sold as "non-USA").
1969 - 1974: XS distributor, but w/ vac retard.
1975 & early 1976: small distributor, completely redesigned, very good quality points distributor. Vacuum retard.
Late 1976 & 1977: Same, but w/ vac advance
1978: redesigned w/ Med. size screwdown, waterproof cap, electronic ignition. Vacuum advance & retard.
1979 - 1980: dual diaphragm advance. One big advance stage for normal operation, small second stage for extra advance at hi-altitude
1981 - 1987 distributor body redesigned to use large cap. Same dual diapragm advance introduced in '79.
1988 - 1992 distributor redesigned w/ out advance. Distributor pickup is a crank angle sensor, advance curve is controlled by computer.

Posted December 15, 2000
Matt Miller
TLCA# 13684
1977 FJ40 2F "Brahma" + Lockright, tach, Warn 8274, FJ60 Power Steering, no more Sanden OBA (factory emissions), so Puma OBA
1996 FZJ80 1FZ-FE factory lockers + Safari intercooled turbo, Warn M12000, OEM CDL switch, cup holder, and hand throttle, Metric TLC leather, heated seats, JDM switches, Puma OBA
2000 Tundra Limited TRD 2UZ-FE SOLD

Last edited by subzali; 12-15-2010 at 02:28 PM.
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