Yesterday I finished installing my intake (custom pipes and open K&N filters) along with removal of the AC and PS. I still have the airpump installed for now. My question is, is it normal to have less negative vaccum after doing mods that create less restrictive airflow both in and out of the engine. I was pulling around -17 to -18 in/hg prior to the intake install at idle. Now I see around -15 to -17 in/hg at idle. One thing I also notice was I disconnected the wiring to the airpump to eliminate the "moo" and notice that the vaccum dropped as low as -14 in/hg at idle and idle mixture became very rich and idle was slightly irratic. I have since reconnected the wiring because that moo is just too annoying!
Anyhow, does anyone have any ideas on the loss of vaccum.
One final question, when removing the airpump, ACV, etc., can idle mixture be leaned out with a standalone like the PFC or AEM EMS.

 

^Bump^

 

If you want more vaccum hold your hand over the intake. But seriously: If you reduce the intake restriction with K&N filters you will get less vacuum. That is teh whole premise of higher airflow... It is easier for the engine to suck air into the intake pipeing

 

Yes, you can program your idle using a programmable ECU like the PFC, AEM, Haltech, etc..

 

I figured that with a less restrictive intake I would pull less vacuum but just wanted to verify this as normal. Thanks guys.

 

i pull 7-8inHg of vaccum at idle











bridgeport though ;-) talk about airflow!

 

Man, I run a stock motor with K&N cone filters, a 3inch mandrel bent exhaust and I pull 13-12 at idle, 10 in Drive, 10 at idle with the A/C, 5 in drive with the A/C with a bouncy idle. Air pump is connected to try to stop the idle from dropping too low and stalling. (Happens sometimes...)

 

low vaccum on stock ports means you have engine problems, or a crappy gauge

 

Hrm yeah? Better get a comp. test done. (flushing sound ensues) Bye cash.

 

Update: Compression test shows that everything is good. (90's all rotor faces on both rotors) Looked at plugs and they foul every 3 or so days. Replaced the plugs and no more bouncy/hunting idle for a few days but vacuum with the A/C is still very low. Could it be my ignition coils or possibly the compressor going bad?

 

Now I'm getting mixed answers from various people. Some say that 90 PSI is really low while others say anything over 75 PSI is fine. Does anyone know for sure?

 

90 is good 75 is marginal

 

According to Rob Robinnete's site 90 (5.75kgf/cm2) is almost ready to go. He states that 5.5 is on the verge of death. Not too far off...

 

Do a quick search and see what others say. The manual for the car if i recall says diffrent numbers also.

 

when I changed to the hks rs intakes my vacuum stayed the same at 19