ACV Question

BinoX · June 07, 2011, 08:53:22 PM

On a 1989 Turbo II, if you install an aftermarket exhaust with no cat am I right in thinking that the ACV doesn\'t actually do anything any more?

If it doesn\'t where\'s a good place to get a block off plate from? (My fabrication skills leave a lot to be desired)

If it DOES still do something, what does it do?

m1tch · June 07, 2011, 09:02:56 PM

I am guessing you mean the air pump? The air pump also pumps air into the exhaust, mine decatted, but its running air via the port air valve, you can get blanking plates from DM motorsports I believe

BinoX · June 07, 2011, 09:15:36 PM

Thanks for the quick reply

Well, I assume the port air valve is probably what I called the ACV... Yeah, I meant get rid of the air pump AND the port air valve all in one swoop...

But since it still pumps air into the exhaust it must still help with emissions a bit.. how much difference does it make?

m1tch · June 07, 2011, 09:20:58 PM

Quote from: BinoX;767457Thanks for the quick reply

Well, I assume the port air valve is probably what I called the ACV... Yeah, I meant get rid of the air pump AND the port air valve all in one swoop...

But since it still pumps air into the exhaust it must still help with emissions a bit.. how much difference does it make?

My car with airpump and no cat is running a CO of 0.18%

BinoX · June 07, 2011, 09:26:26 PM

That\'s actually very good... Hmmm, I guess it must still do something, although I may end up removing it anyway if I can get away with it... might wait until after I\'ve had the MOT done so I have time to put it all back if it is gunna be too high without it...

Thanks

m1tch · June 07, 2011, 09:32:26 PM

Quote from: BinoX;767463That\'s actually very good... Hmmm, I guess it must still do something, although I may end up removing it anyway if I can get away with it... might wait until after I\'ve had the MOT done so I have time to put it all back if it is gunna be too high without it...

Thanks

You can just fit an electric smog pump from a corvette, im keeping mine for a while, running a stock turbo so don\'t need the space at the moment and it doesn\'t really affect the rev speed

BinoX · June 07, 2011, 09:46:49 PM

Might try that, thx

I don\'t really NEED to get rid of it, I just want to...

Prof · June 07, 2011, 11:19:20 PM

The ACV contains the port, split and relief valves for the secondary air system.

Basically depending on revs, and deceleration or not, it will direct air either to the split air pipe which goes to the side of the cat if you have it), or to the port air - which injects air direct into the exhaust baffles and into the exhaust system, or via the relief valve into the silencer at the front of the car (white device behind/under drivers headlight)

If you remove the Air Pump, then the ACV and all it\'s associated plumbing can be removed. The ACV hides a 1 way valve that stops exhaust getting into the ACV, 3 vac holes from the LIM that feed the valves in the ACV, and a hole that feeds the split air pipe towards the back of the engine. If you get blank off plates, use some gasket sealant, otherwise you\'ll get vacuum leaks.

You get \'falsley\' low CO readings with the air pump installed because fresh air from the air pump is being injected into the exhaust diluting the exhaust and improving the readings

The smog pump can also do that for you.

BinoX · June 08, 2011, 09:29:56 AM

Thx for the info

I\'ll definitely have to get a smog pump then, as I imagine that I can hide that away more easilly

1990_fc3s_t2 · June 08, 2011, 12:46:23 PM

My car passed emissions easily with no air pump or acv, also walbro full 3.5inch exhaust an chipped ecu. I made my own blanking plate from ally, it\'s easy really cos you can use the acv as a template.
Don\'t know my CO numbers off hand I\'ll have a look tonight.
I say chuck it out if you have no cat. :p

Kamatari · June 09, 2011, 12:42:25 AM

Does removing the air pump etc effect the idle at all? i feel like ive read some things that said people have had idle problems after, but then could that be down to not using the blanking plate?

Prof · June 09, 2011, 07:21:38 AM

Quote from: Kamatari;767693Does removing the air pump etc effect the idle at all? i feel like ive read some things that said people have had idle problems after, but then could that be down to not using the blanking plate?

It\'s more likely they\'ve also removed the BAC valve as part of their obsessive declutter program

It is important to get or use thick plates that won\'t bend for the blank offs.