Vac Advance Vacuum Port " "

nightsun · #1 October 4th, 2007, 01:14 PM

Anyone see a problem(s) with running the va vac signal from the last port near the firewall on the row of three on the tb? If so, what issues?? The first two ports are not usable. Supposedly, the first nipple on the tb was "specialized" for the vac advance since it only sees vacuum above idle. Is this the case...? This is on my custom 60mm built by Brian at LSP. Need help asap as I am trying to correct a very ````ty idle.

nightsun · #2 October 4th, 2007, 09:17 PM

Alright check this out...aside from responding to my own post, I wanted to update this to see if someone can respond with any direction here. Apparently, the last port on the tb (the one closest to the tb) absolutely will not work for the vac advance. Again, with it hooked up here idling, reving and driving was pretty bad. Their was a constant miss. It would hold an idle and was somewhat driveable but it did so poorly. I moved the va hose to the nipple on the mixer housing inlet right where the ovcp hooks up and capped the port on the tb. With it here, idle was darn near perfect. It was revving perfectly with no missing whatsoever. With the car idling at about 950rpm I removed the line at the va and timing didnt move at all and stayed right at 12btcd. I revved the engine to about 2500 or so and timing still didnt move. If I am not mistaken, the va should only adjust timing when under boost so this is normal???

I didnt take the car for drive since I am still not sure this is correct. I will have to install the wb first. Any input is appreciated.

nightsun · #3 October 4th, 2007, 10:27 PM

..okay so I took it for a 10mile drive...drove perfect...! Zero spuddering, smooth idle and acceleration. Need to get the wb and the afc hooked up to see what its really doing. 17 miles on the new motor and counting...

louswheel01 · #4 October 4th, 2007, 10:58 PM

The vacuum advance hose should go on the first port on the TBI. Standing over the drivers side fender, looking at the TBI three ports, the one on left closest to the Throtle Position Sensor is the one the vac advance goes to.

Try that.

nightsun · #5 October 5th, 2007, 09:33 AM

Both of those first two ports are gone. This is a custom 60mm throttle body built by lsp. Apparently, it was a "one-off" peice (and I now know why). I will ask Kelly to build me a decent throttle body and will remove the 60mm I have now. It will be fine with it hooked up to the inlet port on the mixer housing while breaking in the motor since I will very rarely get over 1-3psi for the next 500 miles. I think this one would be more at home for a race motor - which mine is not. If it was, I'd swap in a 4G63

nightsun · #6 October 5th, 2007, 12:37 PM

I dont have any pics of the actual ports but you get the idea....and yes I and unplugged the va and capped off the hose.

Kelly · #7 October 5th, 2007, 12:49 PM

Contact Brain at LSP and ask him if he can swap it out for a stock one with a little $$$. If not I'll be your Huckleberry

lol

nightsun · #8 October 5th, 2007, 01:32 PM

Tombstone...great ****ing movie. Stand by for payment...I'd rather not go thru Brian again.

nightsun · #9 October 5th, 2007, 03:56 PM

Here is a response from the manufacturer...

"There is no provision for the other vacuum ports because of the way the TB was bored. What you can do is just leave the vacuum advance off and set the total timing with the mechanical advance. As long as the car starts easily dont worry about it. The vacuum advance is primarily for fuel economy and I never recommend using it with any performance build. If you look at any performance / race car they lock out the distributor to get the most accurate ignition timing. Like I tell everyone who goes beyond the showroom stock Quest, when you do modifications to the engine / induction system you cannot refer to the factory stock service manuals for the tune up. If you do your going to have problems."

Weird. Does the ECU on these cars not control ignition timing whatsoever? "Lock out the distributor"...how can that be? On my 4g63, which I realize is a different animal, ignition timing is everything...the more boost I run, the more I have to control/adjust timing. Not only that, if the ecu detects knock via the sensor...it has to be able to pull timing. Thoughts please...

Totalconquest · #10 September 21st, 2009, 08:22 PM

After reading what Nightsun wrote i tried this on my car. I have the same sputter problem. I did have my vac advance plugged into the port to the left in the row of three like you guys stated but it sputtered. When i tried hooking into the first port where air first enters the top of the TB the sputtering stopped. My car accels better and no sputter or no hesitation of any kind. This just saved my the expensive of a new Distributor thanks man. I say if your car runs good man keep the custom TB on.