Has anyone tried an passed the sniff test
by only running air to the stock main cat?
I want to delete the air control valve from
the lower manifold, which is normally used
to divert air to the cat and intake.I don't
know if it will pass the sniffer without the
air control valve operating.Has anyone done
this, and what happened?
Thanks!

 

With no air going to the cat, your HC and CO emissions are going to go up by several times. I do not think you will be able to pass with no air going to the cat. If you drive the car a lot with no air, the cat will die too and then it will be even WORSE!

I have a 1997 vette electric air pump rigged up for emissions testing purposes that can get you through a test... but it's not suitable for daily driving like that.

Brian

 

Thanks for your reply but you misunderstand
the question.Please read the first sentence
of my tread again.I'm talking about running
air only to the cat and deleting the air
control valve.I want to remove anything
thats not serving a purpose but, I still
need to be able to pass the sniff-test.
Any info is welcome, thanks!

 

oh sorry!!! Yeah if you run air straight to the cat, that should be OK. I don't know if it's bad for the cat to have air running to it all the time though.

 

here's a link: https://www.rx7club.com/forum/showth...+control+valve

here is a cut and paste of that link:

After 10 times through the e station I finally passed. My numbers were horrible before. I checked my air pump and it was blowing alot of air but it was just trickling out to the cat. I had an idea to bypass the air control valve and just run a big hose stepping down in size to my cat. That air pump moves alot of air I had no trace of co i am talking .000 out of an alotted 1.2. If anyone is having problem with emissions try it I searched everywhere on this forum for ideas the best thing i found was alcohol in the gas tank and there was really no straight answer for how much to put in.

 

Thanks guys, yea thats what I intend to do
is buy and electric smog pump to supply the air needed to fire off the cat.Unless the
cat is supplied with air it want get hot
enough to burn up the unburnt fuel, and you'll fail the sniff-test and the operator
of the machine will have never seen numbers
that high before! Ask me how I know.
I just wanted to see if someone else has
gotten this to work before I removed the
air control valve and the rats nest which
controled the various valves associated
with the emissions system.
Phil

 

Phil,

Please post your results.

Dave

 

Yea i removed the ACV valve...but never knew if air was getting from the airpump to my Bonez hi-flo...any writeups/pics on where the lines go??

-Zach

 

I've spent a good amount of time in the past reading up on the smog controls of a FD to try and blame the control system on why it was so "dirty".

If your goal is to bypass the ACV and hook up the airpump directly to the cat only to pass an idle smog test, then it isn't a problem. I know it to work in the case of a stock airpump plumbed directly to the main cat just for the smog test on a 1st gen, which had defective ACV/solenoids. It should work equally well for a 3rd gen with an electric pump.

I'm not sure if Phil plans to run the cat all the time with the airpump, which brings up another issue.

That issue, is if the ECU toggles the airpump on and off at appropriate time to maintain the cat's temperature and prevent it from overheating (not good).

If you run the electric airpump off the stock airpump electrical signal with a relay on the signal, it will run it constantly until around 3000rpms when it shuts it off solely due to the engines rotational speed above that not being too healthy for the mechanical airpump (similar to the A/C's clutch).

The piece from the equation that is missing, is that the stock ECU controls air flow to the main cat through the ACV, which does the determination of when to flow air to the cat, exhaust port, or bypass (relief), and thus, controls the cat's temperature.

I would imagine that you could achieve this functionality easily with a standalone EMS. Alternately, you could achieve the same, by studying the electro-pneumatic routing, and wiring the electric airpump "on" signal to the appropriate signal wire for the solenoid in the ACV that supplies vacuum to the appropriate port to "send" air to the maincat.

Regards,
--Ashraf

 

yeah could we just kind of hook up the ACV separate from the LIM? and just use it for its air routing properties and not have it **** with the idle?

 

"Alternately, you could achieve the same, by studying the electro-pneumatic routing, and wiring the electric airpump "on" signal to the appropriate signal wire for the solenoid in the ACV that supplies vacuum to the appropriate port to "send" air to the maincat."

great idea!!
I would like to see someone do it

 

Ashraf,

I beleive the idea of the magnetic clutch on the airpump is for reducing parasitic losses at higher rpms rather than to prevent over running the pump itself. If you look at older rx-7's and most cars they continuously run the airpump and use the acv to route air to the cat at specific RPMs. The same goes for the A/C pump though with a slightly different use. It turns the pump on and off only when needed and on older cars didn't even shut off under full throttle. Only on the 3rd generation cars does it shut off under throttle. I beleive the sole reason for the shutoff is for reducing power losses. The other thing is that the airpump no longer needs to pump air above 3k rpms because the exhaust is then hot enough to keep the cat adequately heated.

I used the ACV deletion method on my N/A 6 port motor and was commented on how clean my tailpipe was. I hope to find the same when I do it to the REW motor I have now.

 

I believe you are missing a step here and blaming the wrong component.

The ACV doesn't affect idle (well, in theory).
It puts air in either the exhaust port (feeds air to the precat....who the heck has those?....SS autocrossers <grin>) or the cat to change the chemistry of the exhaust for cleaner emissions.

Both of those have NOTHING to do with combustion and hence idle speed of the car.

Now, activating the airpump causes it to "drag" the engine and you must increase the idle speed with the ACV to compensate for the drag (I'm getting to the post two below this one....)

 

I agree it does cause parasitic losses, but the fact it is spinning without the clutch engaged is a parasitic loss in of itself.

Don't want to lose horsepower from the airpump? Remove it and replace with electric, but you are going to draw power from the alternator, the question is which pump is most efficient in power consumption?

True, that is how my 1st gen ran, and how the 2nd gens run since I recall neither having a clutch.

True, but it is a different airpump design. I'm not sure what the guts look like, but they may not like being spun at high RPMS (probably causes more wear and tear and later on causes failure, probably observed in the 1st and 2nd gen cars and "fixed" here) and that is why I believe it is shut off in the FD's case (provided my memory isn't rusty enough to give one tetanus...<grin>)

The A/C is shut off because the A/C pump doesn't like being run at 7500rpms. It is bad for refrigerant pressure.

That's what I remember from the FD FSM. In the FD, there is the low pressure switch, a RPM on/off function via the ECU, and the ECU "turn on" signal because the HVAC switch is on (which also raises the idle).

Again, I'm really out of touch with this stuff, so if someone is looking at the FSM, please feel free to post references and amend this.

Smog tests don't test above 3000rpms, so it doesn't matter...

Regards,
--Ashraf

 

So what is the concensus?

I am planning to try this for my next smog check. Also I have some blockoff plates that I want to install; to eliminate the ACV.

I will probably try this as a test run first as I have to go to a test only station in Southern California.

I'm at 108K on the original engine and turbos. The engine is still running strong with good vacuum and still pushing 13 psi on the turbos.

The problem is that the coolant is being overpressurized, an indication that one of the O rings has a small leak. It's not burining any coolant just allowing some gases to get into the system. I hope that this will not affect the smog check.

Thanks.

 

I fully intend on removing it, especially since I will most likely be putting 1600 cc injectors. I don't have a precat so who cares about that. I think it'll be fine. I've done it with the older model with good results.

Ashraf,

My intent with the electric pump is that sooner or later I want to have a single turbo which will most likely result in the stock airpump location being unusable.

Greg

 

I recently removed/blocked off every emission component except the air pump and fast-passed the test in IL with a partial mixture of denatured alcohol. i have 1600 secondaries and the RX6 single turbo. you have to go easy on the car (no boost), but the alcohol is a huge help and can save you a lot of f'n around under the hood.

Have you seen this?

http://www.zeroglabs.com/rx7/emissions.htm

I don't know how bad your test is, but as long as you retain the air pump, this should work.

 

Let us know how it goes. I know of a place in Cerritos (test only) and the guy was pretty cool. Didnt even seem to do much of a visual inspection or care what was under the hood. I passed with a terrible idle on my 89 gtu (all emissions controls present).

BTW, Anyone pass doing the air pump trick without running that alcohol in the tank?