I bit the bullet and took the ACV and air pump off.

I found the nipple shown below with crappy, wrong size, un-secured vacuum cap falling off of it. What should of it be connected to originally and can I now use it for the vacuum line going to the bypass valve and boost gauge?


<a href="http://s222.photobucket.com/albums/dd66/crackattak/?action=view&amp;current=Nipple.jpg" target="_blank"><img src="http://i222.photobucket.com/albums/dd66/crackattak/Nipple.jpg" border="0" alt="Photobucket"></a>

 

Oh, and those three metal vacuum lines that lead to the ACV, should those be capped or left open?

 

The original owner had both the bypass/blowoff valve and pressure sensor connected to a T that went to the ACV.

From looking at the vac diagram that nipple was is probably the correct feed for bypass or the sensor, or am I wrong?

 

It's a manifold vacuum/pressure source, so you can use it for the bypass valve, boost sensor or boost gauge. In stock form, I think it was used for the boost sensor. It's used for the boost sensor and gauge on my car.

 

On a stk series four its for the airbypass valve/blowoff valve. The nipple on the ACV was meant solely for the boost/pressure sensor.

 

Alright, what about the three lines on metal spider going from the acv to the solenoids? Capped or abmient air?

 

cap them if you are not using them any longer.

also, that is a horrible spot for a boost gauge connection and even worse for a map sensor hose. that as well as the stock pressure sensor port have the most resonance and bouncy signal of all the ports on the engine.. i have seen signals bounce as much as 5psi in boost and 5"hg on naturally aspirated engines with that port, throwing your timing all over the map as well as fuelling(with a standalone ems) and causing inaccurate boost gauge readings.

i have no idea why mazda chose to put them there aside from they read the signal 1 millisecond faster than at the T/B. the stock line however was supposed to have a restrictor to smooth the signal but now with everyone changing their hoses most have long since gone and their owners not even realized that they have bad timing figures while driving. there are 3 ports at the throttle body that give boost+vacuum signals(top and bottom on the front side and i forget which one at the rear as there was 2 different configurations).

 

ABS, nice.

 

I'm currently using that nipple for my boost gauge and mega-squirt and I don't see fluctuations at all... it's pretty stable.

 

just speaking from experience, i have noticed it on a few cars. depends on the ports and depends on how fast your display reads. most boost gauges have a buffer built in, the megasquirt may also, but seeing figures with the rtek 2.1(what the stock ECU is compensating for) on a naturally aspirated engine at the stock LIM port it was very bouncy until i moved it, also on a turbo bridgeport off the BOV nipple with a microtech LT10s it was bouncing from 11-16psi rapidly until i moved it(very bad...)

sometimes you don't see what the ECU is actually compensating for until you read your logs, some ECUs will buffer the map signal, others will not because it causes a delay.

if you want to keep using it that's fine, it's just a suggestion.

 

Cap 'em off. Only one ever had vacuum on it on the original config. The other two are tied together in a since, since one line took airpump air from the ACV and sent it to the relief solenoid on the other side of the engine. Then at given times the Relief solenoid opened and sent that air back to the bottom of the ACV as air pressure to operated the diaphram for the ACV's air relief valve internal to the ACV. Caused airpump air to be dumped into the silencer in the right front fender next to the washer bottle.

If you still have the vacuum rack and solenoids on the left side of the engine then cap off the one that gets fed from the Switching solenoid (grey solenoid). The one of the three that got fed vacuum at times would be the most inbd one if memory serves. It had a hose on it that went to a nipple on the top side of the turbo ACV. Just cap all three and be done with it. Keeps dirt out if nothing else.