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Old 12-13-2010, 10:52 AM
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subzali subzali is offline
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Default Desmog

So I started a thread on MUD about fully desmogging my FJ40 - it's kinda sorta already desmogged (no air pump, ABV, EGR/EGR cooler or air rail), but I thought there was still more I could do to clean up the engine bay a little bit and get rid of vacuum hoses that I don't need and aren't really doing anything. AFAIK, you can't just go in and remove every vacuum hose, because some of them are good, like for distributor advance, throttle positioning system etc. But I've been getting the beatdown pretty much:
http://forum.ih8mud.com/40-55-series...2f-desmog.html

I guess I understand some of them saying that I should keep the stock system, that the carb and dizzy control is electronically actuated with the smog "computer", blah blah blah. But the other part of my problem is that I have a '78 dizzy (fully electronic) and '78 carb, both of which have some differences as compared to the '77 setup. So I'm trying to decide how to go forward:

1) Keep it the way it is and not worry about it because it runs fine (still have some vacuum hoses, VCVs and VSVs, but they don't seem to do much). Or maybe make some slight tweaks to make sure it's hooked up properly (wrt dizzy vacuum advance etc.)

2) Restore back to stock '77 setup, including points ignition (semi-electronic, which means I would need a '77 carb, '77 dizzy, and '77 igniter) and smog equipment (unfortunately I tossed my EGR cooler when I did my p/s conversion, kicking myself for that now because I intended on keeping it in a box, guess I wasn't thinking clearly - so anyway I'd have to find another one)

3) Keep trying to figure out how to fully desmog my current setup, because I like the fully electronic ignition, and play with how to properly hook up my '79-'80 dual vacuum advance dizzy.

4) Get '77 stuff and desmog that so I know the computer, dizzy, carb, everything works together the way it should. Which isn't really true because it was designed to work together with all the emissions stuff, not just with some of it.

So I guess No. 3 was what I was trying to do, No. 2 was what I was recommended to do, No. 3 and No. 4 sound like a bad idea after asking MUD, and No. 1 is what I'm inclined to do now because I'm sick of thinking about it and it's the path of least resistance

Help?
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1977 FJ40 2F "Brahma" + Lockright, tach, Warn 8274, FJ60 Power Steering, soon to lose the Sanden OBA to go back to factory emissions
1996 FZJ80 1FZ-FE factory lockers + Safari Turbo , CDL switch, cup holder, AATLAS1X leather, heated seats and JDM switches
2000 Tundra Limited TRD 2UZ-FE SOLD

Last edited by subzali; 12-16-2010 at 10:35 AM.
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Old 12-13-2010, 11:34 AM
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I've been following your thread on Mud and it is interesting. Personally, I like the simplicity of the F engines without the smog equipment but I don't know that I would go through the process of a desmog if my smog equipment was working and serviceable. I'm sure it robs some power, but I don't believe it is enough to notice.

From what I can tell, you are not that far away from being able to get rid of most everything smog related. In very simplistic terms, you will end up with a 2F that looks like an F. The one constraining factor that I see is your carb. That is to say, you don't really know what you have to keep (or can toss) for the carb in your truck - so eliminate the constraint and swap your carb in favor of:
  • Trollhole carb - linkage and de-smogged
  • 1974 DD38 Aisan - linkage and de-smogged, needs to be drilled for ported vac.
  • 1970 to 1973 DD38 Aisan - cable activated and de-smogged,needs to be drilled for ported vac.
  • Weber

As your truck is set up with linkage versus a cable, the Trollhole carb will be easiest (basically plug and play) whereas all the others (except Weber) may need some modification. A two barrel carb with mechanical secondaries and ported vacuum works just as well on a 2F as it does on the F.

You can keep your 78 electronic ignition. It is a very good (and serviceable) ignition system. I've run a 78 dizzy (vac retard) with the vacuum ports capped off for a year. There is not anything wrong with running the truck with just mechanical advance; I did notice an improvement once I added ported vacuum (and vacuum advance) - but I got everywhere I was going without it too. That said, it is pretty easy to "upgrade" to the 60 series big cap dizzy and have it recurved or run an HEI dizzy. The HEI is a very straight forward swap.

The 2F that Randy put in the Blue Mule is from an 80 2F. The smog equipment has been removed and it really looks pretty much like an F engine in its simplicity - he just moved over all the F.5 accessories. IIRC, the 2F Kvanoort put into his 1972 is pretty much the same.

On my truck, vacuum connections exist for PCV, brakes, transfer case and dizzy - and it is only recently that I added the ported vacuum for the dizzy.
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Old 12-13-2010, 11:44 AM
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Thanks Ricardo, I'm going to digest this a little at a time. But I want to focus on one statement right here quick:

Quote:
Originally Posted by RicardoJM View Post
I've run a 78 dizzy (vac retard) with the vacuum ports capped off for a year. There is not anything wrong with running the truck with just mechanical advance; I did notice an improvement once I added ported vacuum (and vacuum advance) - but I got everywhere I was going without it too.
Mechanical advance is just rotating the dizzy to set the nominal advance with the bb on the flywheel right? Right now I have that a little over 7* IIRC. EDIT: the dizzy has built-in mechanical advance based on engine rpm. Vacuum advance gives an additional sensitivity to engine load.

Right now I have the primary vacuum advance can (closer to the dizzy body) hooked up to what is basically the stock emissions hose routing. I think I can play with which advance can I can hook up and which ported vacuum port I hook it to, and as long as I don't have pre-ignition I should be fine. And I think I know what ported vacuum is, but I'm having trouble visualizing which port that is on my carb...

Thanks
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1977 FJ40 2F "Brahma" + Lockright, tach, Warn 8274, FJ60 Power Steering, soon to lose the Sanden OBA to go back to factory emissions
1996 FZJ80 1FZ-FE factory lockers + Safari Turbo , CDL switch, cup holder, AATLAS1X leather, heated seats and JDM switches
2000 Tundra Limited TRD 2UZ-FE SOLD

Last edited by subzali; 12-16-2010 at 10:41 AM.
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Old 12-13-2010, 12:34 PM
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I enjoyed reading the thread as well - just a good overall view of the emissions systems on these trucks. Other than a deleted air pump, mine is mostly original and I'm afraid to touch it....

I don't have anything to offer technically, but I too would question the reasoning if you stand to achieve little or no functional gain, but risk "destabilizing" the system to eliminate a few hoses? Or are you trying to solve another problem as well?
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Old 12-13-2010, 12:50 PM
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Quote:
Originally Posted by subzali View Post
...Mechanical advance is just rotating the dizzy to set the nominal advance with the bb on the flywheel right? Right now I have that a little over 7* IIRC.
Yes and no; mostly no. You are correct, setting the timing is a "mechanical" action, i.e. you turn the dizzy. Each distributor has a "mechanical advance" system built in. As the engine RPMs increase the dizzy's built in advance system ( "mechanical advance") changes the timing - it advances it. The basic principle is that at high RPM, each cylinder can spark a little earlier than at low RPM - so that power and fuel usage are "maximized". In the evolution of things, a vacuum advance system was added to use ported vacuum to further maximize power and fuel usage under certain conditions, i.e. when ported vacuum is high.


Quote:
Originally Posted by subzali View Post
Right now I have the vacuum retard can (I think - the one closer to the dizzy body) hooked up like my '77 is normally hooked up (I guess, I don't understand why there is vacuum retard, I always thought that as your engine speed increased that more advance was needed on the ignition (which it doesn't seem that there is any provision for with a stock '77 setup), but I also know that higher speed doesn't necessarily mean higher vacuum). So are you saying if I hooked up the advance can in addition to (or instead of?) the retard can that might be a better way to go? Do I just have to be careful of pre-ignition? And I think I know what ported vacuum is, but I'm having trouble visualizing which port that is on my carb...

Thanks
Much of the above is mystery for me as well, relative to the late 70s Aisan carbs. I am hoping that your thread on MUD will result in some additional insight and understanding - someone out there has to know this stuff.

About all I know for sure is that automotive engineers have evolved things over time. In the 70s they started using engine vacuum, controlled by speed sensors (initially) and components/computers (next in the evolution) to advance or retard timing thereby altering the dizzy's built in advance system resulting in even better maximization of power and fuel. Like you, I'm not clear on the detailed specifics. We are now in the age where the dizzy is gone, and each cylinder has its own coil pack and the computer runs the show. Great for low smog, more power and improved fuel economy.

Not knowing how vacuum is routed through all the ports, it is not advisable to start changing connections on the dizzy. The results may likely not improve the performance of the engine. That said, I am pretty sure that if you have a ported vacuum port on the carb - it is ok to hook it to a vacuum advance port on a distributor.

Again, I'm not familiar with mid-70's and newer carbs - but on all the early carbs the ported vacuum port is just to the right of the idle mixture screw. This port does not exist on all early carbs but can be added. It is a real simple thing to do, but has to be very precise. I didn't have the confidence to do it on my own, so I sent my carb base out to get it done.

You are correct, when setting engine timing if you are pinging it has been advanced too far. Also, if it is difficult to start, it has been advanced too far.
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Old 12-13-2010, 01:27 PM
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Quote:
Originally Posted by Jacket View Post
I enjoyed reading the thread as well - just a good overall view of the emissions systems on these trucks. Other than a deleted air pump, mine is mostly original and I'm afraid to touch it....
That's where I've been for the past 5.5 years...

Quote:
Originally Posted by Jacket View Post
I don't have anything to offer technically, but I too would question the reasoning if you stand to achieve little or no functional gain, but risk "destabilizing" the system to eliminate a few hoses? Or are you trying to solve another problem as well?
When I first got my 40 I followed the herd mentality I guess of "desmogging is cool." I was always of the opinion that these trucks ran great before smog equipment came along, so all the smog equipment does is add weight, rob power (smog pump, EGR), and "de-tune" the engine to control the emissions. But what I think I'm hearing is that while the smog stuff does all of that, it's also tied in with other things that actually make the engine run better by optimizing fuel and spark a little better. To give up the "disadvantages" of one you pretty much have to give up the "advantages" of the other. This is a new concept to me, so that's why I'm thinking of either taking it back to the original configuration or leaving it as-is, since it seems to work fine.

But the smog pump location is perfect for the on-board-air compressor I had in mind

Quote:
Originally Posted by RicardoJM View Post
Yes and no; mostly no. You are correct, setting the timing is a "mechanical" action, i.e. you turn the dizzy. Each distributor has a "mechanical advance" system built in. As the engine RPMs increase the dizzy's built in advance system ( "mechanical advance") changes the timing - it advances it. The basic principle is that at high RPM, each cylinder can spark a little earlier than at low RPM - so that power and fuel usage are "maximized". In the evolution of things, a vacuum advance system was added to use ported vacuum to further maximize power and fuel usage under certain conditions, i.e. when ported vacuum is high.
I didn't know the distributor had a built-in mechanical advance system. That makes perfect sense and is what I would suspect, but I just didn't know that that was the case.

Quote:
Originally Posted by RicardoJM View Post
Much of the above is mystery for me as well, relative to the late 70s Aisan carbs. I am hoping that your thread on MUD will result in some additional insight and understanding - someone out there has to know this stuff.
Jim C. does but he doesn't frequent the 40 series section much, and Charlie Glabe (Pinhead) usually knows what he's talking about, so I have respect for his comments in my thread.

Quote:
Originally Posted by RicardoJM View Post
About all I know for sure is that automotive engineers have evolved things over time. In the 70s they started using engine vacuum, controlled by speed sensors (initially) and components/computers (next in the evolution) to advance or retard timing thereby altering the dizzy's built in advance system resulting in even better maximization of power and fuel. Like you, I'm not clear on the detailed specifics. We are now in the age where the dizzy is gone, and each cylinder has its own coil pack and the computer runs the show. Great for low smog, more power and improved fuel economy.

Not knowing how vacuum is routed through all the ports, it is not advisable to start changing connections on the dizzy. The results may likely not improve the performance of the engine. That said, I am pretty sure that if you have a ported vacuum port on the carb - it is ok to hook it to a vacuum advance port on a distributor.

Again, I'm not familiar with mid-70's and newer carbs - but on all the early carbs the ported vacuum port is just to the right of the idle mixture screw. This port does not exist on all early carbs but can be added. It is a real simple thing to do, but has to be very precise. I didn't have the confidence to do it on my own, so I sent my carb base out to get it done.

You are correct, when setting engine timing if you are pinging it has been advanced too far. Also, if it is difficult to start, it has been advanced too far.
I know I have ported vacuum, I'm just not exactly sure where it is. I think ported vacuum means it's located above the throttle plates, so it only sees vacuum when the accelerator is pressed and the throttle plates are opened.

My big problem with taking the system back to stock is with my ignition/dizzy/carb. The PO said that the vehicle backfired with the smog pump hooked up (I never experienced that but didn't have the smog pump on for very long), and I wonder if that's partly a function of the '78 ignition, '79-'80 dizzy, and '78 carb?

Sigh, I really like not having to adjust points...

Ricardo, doesn't the big cap dizzy have multiple vacuum cans on it as well? Do you just have one plugged off?
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1977 FJ40 2F "Brahma" + Lockright, tach, Warn 8274, FJ60 Power Steering, soon to lose the Sanden OBA to go back to factory emissions
1996 FZJ80 1FZ-FE factory lockers + Safari Turbo , CDL switch, cup holder, AATLAS1X leather, heated seats and JDM switches
2000 Tundra Limited TRD 2UZ-FE SOLD

Last edited by subzali; 12-16-2010 at 10:42 AM.
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Old 12-13-2010, 02:51 PM
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Quote:
Originally Posted by subzali View Post
...
I know I have ported vacuum, I'm just not exactly sure where it is. I think ported vacuum means it's located above the throttle plates, so it only sees vacuum when the accelerator is pressed and the throttle plates are opened.
Your first sentence made me giggle. If you have the port just to the right of your idle mixture screw - it is very likely ported vacuum. That is to say, while the carbs have changed year to year a port in that location is where I have always seen it.

Quote:
Originally Posted by subzali View Post
My big problem with taking the system back to stock is with my ignition/dizzy/carb. The PO said that the vehicle backfired with the smog pump hooked up (I never experienced that but didn't have the smog pump on for very long), and I wonder if that's partly a function of the '78 ignition, dizzy, and carb?
Yeah, because the systems and components vary year to year the one solid answer is to first determine where you want to be; desmogged, 77 year emissions or 78 year emissions - then you compile what is needed to get where you want to be. Easy to say (I know) and aside from dollars and sourcing parts; easy to do. Mix and match (what you have now) works, after all your truck is running proof.

Quote:
Originally Posted by subzali View Post
...Ricardo, doesn't the big cap dizzy have multiple vacuum cans on it as well? Do you just have one plugged off?
Yes they do. I only use one. As I understand it; one of them is for vacuum advance and the other is for additional advance that is triggered by the high altitude compensation system. I do know that it is not advisable to run them both without the appropriate equipment managing them. I had Mr. Chenworth re-curve a big cap dizzy for my F.5 engine. I have not installed it yet, but it did come back from him with one of the "vacuum cans" capped off.
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Old 12-13-2010, 03:08 PM
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The idle mixture screw is on the side of the carb facing the head right? I have 3 ports on that side with my '78 carb, but you said the one on the right is ported vacuum...
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1996 FZJ80 1FZ-FE factory lockers + Safari Turbo , CDL switch, cup holder, AATLAS1X leather, heated seats and JDM switches
2000 Tundra Limited TRD 2UZ-FE SOLD
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Old 12-13-2010, 03:29 PM
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It is marked with the blue arrow.

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Old 12-15-2010, 10:27 AM
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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
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1977 FJ40 2F "Brahma" + Lockright, tach, Warn 8274, FJ60 Power Steering, soon to lose the Sanden OBA to go back to factory emissions
1996 FZJ80 1FZ-FE factory lockers + Safari Turbo , CDL switch, cup holder, AATLAS1X leather, heated seats and JDM switches
2000 Tundra Limited TRD 2UZ-FE SOLD

Last edited by subzali; 12-15-2010 at 01:28 PM.
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