TBI upgrade and smog disconnection

[Gramps Old Jeep]

I'm going to upgrade to a TBI systems on my 1974 J-10 360.

I was hoping to be able to disconnect a lot of the smog systems at that point. I'm not really against them, but they are all mechanical and over 30 years old and I believe some are not working.

Here is the list.

AIR
EGR (California version)
Themostatic Controlled Air Cleaner
Thermal Vacuum Switch
Spark Coolant Temp Override
PCV
Back Pressure Senssor

It's a California Jeep so there is no TCS.

I figure the AIR and the PCV are not really bad things but I would like your opinions on them and the rest.

Thanks

[Chevelleguy]

If you are using a closed loop EFI system you cannot use the AIR system as it will confuse the O2 sensor. The EGR is needed to cool the combustion chamber to reduce NOx emissions and reduce detonation. PCV must stay to reduce crankcase pressure. The rest of them can be eliminated if you can get them working right.

[Gramps Old Jeep]

Thanks David.

Any way to shut the AIR off while leaving it hooked up? Mayber a hose block with an openning to the atmospher?

[Chevelleguy]

Originally posted by Gramps Old Jeep:
Thanks David.

Any way to shut the AIR off while leaving it hooked up? Mayber a hose block with an openning to the atmospher?Don't hook up the hoses to the exhaust manifolds or just take the belt off.
Even with EFI you need the EGR to prevent detonation unless you are running too rich.

[Rande]

By all means, keep the EGR. Contaminating your incoming air/fuel mixture with exhaust gases is a GREAT idea! Another "Band Aid" type fix that turned out so well.

Notice what it does: reduces combustion temps.
That means: less power.

The AIR system was a good one though. Dilute the exhaust gases with clean air and get cleaner exhaust out the pipe. Hmmmmmmm.....

[Chevelleguy]

Rande, the EGR only works at cruise so there is no noticable power loss and it works very well, still in use in new cars.
Think of an AIR pump as blowing on a camp fire to get it started. The added fresh air makes the exhaust coming out of the head hotter to burn off any unburnt fuel (hydrocarbons).

[ August 07, 2005, 12:27 PM: Message edited by: chevelleguy ]

[Gramps Old Jeep]

Pretty differing views here (which is a good thing). What about the theory on the AIR confusing the oxygen sensor?

How about a lively discussion on that?

[FSJ Guy]

Don't disconnect your air pmp or it will freeze and you'll have to pay about $50 or so for a NEW one. If you are able to disable the AIR injection system, make sure you cap or block the AIR injection ports on top of the manifold. DON'T cut the tubes off and weld the holes shut!!! You never know when you'll need it or need it to "look like" it's operational.

I have a Howell TBI system and I have set up the AIR injection so that it does not "work" but it is not removed, either.

[Gramps Old Jeep]

Guys, thanks again for the help!

FSJ, how did you disable your AIR?

[Serious Johnson]

Some of the info here http://customefis.com/emissions.html is pretty good.

S.J.

[JeepinPete]

You can indeed use the AIR system with TBI. Chevy did this in their TBI trucks. What you would need is a computer controlled diverter valve, the same part that is used on those trucks. Since the computer controls it, it knows when the air system is operational, and what mode it is in.

When the truck is cold, air is injected at the exhaust manifolds. During this period of time, the O2 sensor isn't working anyhow. When the computer is ready to start using the O2 sensor, it will switch the diverter valve so that air is injected directly into the cat. Since the O2 sensor is before the cat, it isn't effected at all.

Now on the flip side, it probably isn't necessary to keep the air system. The emissions on a properly tuned TBI system will be way less than what the Jeep put out on its best day.

[pb]

If you want to get rid of the EGR, just retard the timing a few degress. Why put exhaust gases in the combustion chamber to take up space. That means you are gettting less air and gas in there. Kinda negates any air/fuel system mods or upgrades.

As mentioned, the AIR system will mess with the O2 sensor once it is heated up.

On my '75, I only have the PCV. Everything else is gone.

Anti-riced: I wasn't able to log the data yet, but will try to as soon as I can and get that to you.

[crispyboy]

customefis made the chip work on my truck so I could fully use the egr and original emission equipment. seems to be doing ok.

[Rande]

David, please don't bother me with facts....... ;)

[mdill9]

Originally posted by pb:
If you want to get rid of the EGR, just retard the timing a few degress. Why put exhaust gases in the combustion chamber to take up space. That means you are gettting less air and gas in there. Kinda negates any air/fuel system mods or upgrades.

As mentioned, the AIR system will mess with the O2 sensor once it is heated up.

On my '75, I only have the PCV. Everything else is gone.

Anti-riced: I wasn't able to log the data yet, but will try to as soon as I can and get that to you.At part throttle cruise, this is a good thing, requires slightly more throttle/lower manifold vacuum, (reduced pumping losses) more ignition advance and leaner
mixture all contributing to better fuel efficancy.

The EGR should not be open at idle or at WOT so
any suggestion of reduced power falls on deaf ears.

Mike D.

[mdill]

Originally posted by JeepinPete:
You can indeed use the AIR system with TBI. Chevy did this in their TBI trucks. What you would need is a computer controlled diverter valve, the same part that is used on those trucks. Since the computer controls it, it knows when the air system is operational, and what mode it is in.

When the truck is cold, air is injected at the exhaust manifolds. During this period of time, the O2 sensor isn't working anyhow. When the computer is ready to start using the O2 sensor, it will switch the diverter valve so that air is injected directly into the cat. Since the O2 sensor is before the cat, it isn't effected at all.

Now on the flip side, it probably isn't necessary to keep the air system. The emissions on a properly tuned TBI system will be way less than what the Jeep put out on its best day.If your working on a later FSJ with the three way
cat system, you do not need to do any thing, other
than ignore the o2 sensor untill the engine is at
~150 degrees, the existing diverter valve and CTO
switch will take care of this probem automaticly.
The O2 sensor won't work when cold anyway, so
the only thing is you may have to run open loop
for a few more minuets to allow the stock AIR
system to switch than you would with the GM AIR
system.

Mike D.

[pb]

Originally posted by mdill9:
</font><blockquote>quote:</font><hr />Originally posted by pb:
If you want to get rid of the EGR, just retard the timing a few degress. Why put exhaust gases in the combustion chamber to take up space. That means you are gettting less air and gas in there. Kinda negates any air/fuel system mods or upgrades.

As mentioned, the AIR system will mess with the O2 sensor once it is heated up.

On my '75, I only have the PCV. Everything else is gone.

Anti-riced: I wasn't able to log the data yet, but will try to as soon as I can and get that to you.At part throttle cruise, this is a good thing, requires slightly more throttle/lower manifold vacuum, (reduced pumping losses) more ignition advance and leaner
mixture all contributing to better fuel efficancy.

The EGR should not be open at idle or at WOT so
any suggestion of reduced power falls on deaf ears.

Mike D.</font>[/QUOTE]I'm not an expert on the TBI yet, but I thought you can program the computer for a leaner mixture at part throttle cruise, plus the spark advance can increase by the computer.

[mdill]

Originally posted by pb:
</font><blockquote>quote:</font><hr />Originally posted by mdill9:
</font><blockquote>quote:</font><hr />Originally posted by pb:
If you want to get rid of the EGR, just retard the timing a few degress. Why put exhaust gases in the combustion chamber to take up space. That means you are gettting less air and gas in there. Kinda negates any air/fuel system mods or upgrades.

As mentioned, the AIR system will mess with the O2 sensor once it is heated up.

On my '75, I only have the PCV. Everything else is gone.

Anti-riced: I wasn't able to log the data yet, but will try to as soon as I can and get that to you.At part throttle cruise, this is a good thing, requires slightly more throttle/lower manifold vacuum, (reduced pumping losses) more ignition advance and leaner
mixture all contributing to better fuel efficancy.

The EGR should not be open at idle or at WOT so
any suggestion of reduced power falls on deaf ears.

Mike D.</font>[/QUOTE]I'm not an expert on the TBI yet, but I thought you can program the computer for a leaner mixture at part throttle cruise, plus the spark advance can increase by the computer.</font>[/QUOTE]Right, and with EGR you can go further than what
can be done without it, lean mixture -&gt;high temp
-&gt; with EGR you can go leaner with more advence
and still keep the piston tops on vs. without.

Mike D.

[Rande]

How can contaminating your incoming air/fuel mixture with burnt exhaust gases NOT reduce power?

This should be good.

[Spectre]

When your "burnt" exhaust gases contain additional unburned hydrocarbons.

Here's a quick test. Put an engine on a dyno. Run it with the EGR connected, then run it with the EGR disconnected and the engine retuned. Check out the numbers.

[mdill9]

Originally posted by Rande:
How can contaminating your incoming air/fuel mixture with burnt exhaust gases NOT reduce power?

This should be good.You are correct, but the EGR valve is not(should not)
be open when you want power (low manifold vacuum)
The EGR valve is only open are part throttle
cruise.
EGR is active when for example you are cruising
down the freeway at part throttle, you want best
fuel economy and you are only asking ~25 hp from
the engine. At this operating point you want a
lean mixture, ~15:1 Max ignition advance. The EGR
valve helps in this mode.
When you want power, large or wide open throttle,
the EGR valve is closed (or should be) the power
valve on the carb opens (riching the mixture)
Allowing the engine to produce the max power.
(Little less advance, and a ~12:1 mixture)

So yes EGR does reduce power, but it does it in
an area of the power curve where you don't care
about power and has no effect on peak or WOT power numbers.
Hopefully, you don't need to operate at WOT for
a very large % of your driving, and EGR valve allows
good things to happen at a point where the engine
will spend a much larger % of its operating time.

Mike D.