This is about doing a vacuum test on a 6th gen 4cyl(F23A1) accord.

1. When I connect the vacuum gauge to a point on the intake manifold I have to disconnect one of the vacuum line going into it to free up the point for testing. Should I use a "T" or should I just leave the disconnected vacuum line by itself and connect the vacuum gauge straight to the point on the intake manifold ?

2. Is it possible to use a vacuum test to determine if you have a restrictive intake ? i.e. if the intake is big/free enough to supply the air on demand by the engine.

 

Yes a tee and go off the fuel pressure reg vac line.

And as using vacuum for flow, aaa NO at idle around 20 in.hg and after you go past 1/4 throttle vacuum is not present. I should say very little.

Don't think air is like water.... air flows much easier.

The newer trucks have an flow meter on the side of the air filter housing. But your air filter would have to be very plugged Did I say VERY.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thesmogman &raquo;</TD></TR><TR><TD CLASS="quote">at idle around 20 in.hg and after you go past 1/4 throttle vacuum is not present. I should say very little. </TD></TR></TABLE>

understood about the idle but what do you mean by very little vacuum past 1/4 throttle ? even at 4k rpm I get about 18inHg of vacuum.

 

Your throttle is not open 1/4 at 4000rpm maybe 1/16th open.

At 1/4 throttle while driving, not in park.

You will see what I mean. If in park or not driving if you go to full throttle for a second the vacuum will drop to 0

So here is the test.
Hook up vacuum and tape to windshield.
Go driving and get on freeway.
At full throttle you will see it drop to 0 vacuum. or very very close to it.

And when you decellerate? you should see 30 in.hg

 

yeah I was going to do just that but cant seem to find a good place to route the vacuum gauge's pipe out back from the hood.
btw, quick snap and release does result in 0 and 27inhg respectively.

 

well somehow managed to keep the hood semi-closed so as not to crush the vacuum gauge pipe and took readings (but not on the accord, on the other car - Acura MDX 3.5L V6) and at 1/4 to 1/2 throttle it showed about 8-10inhg. Above 1/2 throttle it went close to 0 (3-4).