Where do you guys pull your vacuum reference from. I have mine tapped into the base of my elbow and my readings are way off. I'm only reading 2" of vac at idle and even if I rev it up my guage barely moves and will only drop to 4" when I snap off the throttle. My power brakes seem adequate...so it seems like I have more vac than my guages say(boost gauge, and AEM map both read the same). Could I be getting a false reading or should I be looking for leak?

Rick

 

I pull mine off of the base of the elbow and it reads fine.

 

I did too and my brakes worked fine. But I think my guage was reading wrong as well!!

 

I tapped a hole in the bottom of the elbow, mine was fine.

 

same here

 

Mine is set up like Bens also.

 

Okay.so I'm not crazy for tapping the base for a vac source. Are all you guys getting propper readings for vac??? Is this just a characteristic of the elbow and the fact that it has no plenum volume? IT is really messing up my AEM tun as it relys totaly on MAP readings for everything.

Rick

 

Is it showing 2" of vacuum on the guage or on the AEM?

Thats where my buddies Capri is hooked up with the Gen 7 and its never been a problem.


Chris

 

both my AEM map and the gauge are reading close to the same. I trust the AEM map more than the gauge but so far they are pretty close.

 

That's really odd because I believe I'm seeing a valid reading.

When I had a Novi 2k and Shane Fought's old cam I saw about 10" of vacuum at idle. With my turbo setup and a smaller Cam Motion cam I see 15" of vacuum at idle...which I expected due to the cam being smaller.

 

Damn...thanks for the input. I guess I need to figure out where my vac is going.

Rick

 

is there another place to install a vacuum reading other than the elbow itself?

 

A little off topic but do/can any of you guys take a pic of the inside of one of the runners with a fuel injector installed?? I want to see what the position of the nozzle is inside the runner.

 

UPDATE: My boost vac guage is still reading way off. Perhaps the line is plugged up I have not checked. However with my timing set properly and my A/F in check my MAP is reading around -6.0 to -6.6 psi at idle which is around 12-13" of vac. SO all is good.

Rick

 

What side of the elbow is tapped? Theoretically the pressure (or vacuum) will be different across the x-section of a bend because of the centrifugal force acting on the charge as it rounds the bend. This will have an effect on the charge even after the bend as the pressure profile tries to come back to an equilibrium. I'm not sure how great of an effect this would have in your situation, but maybe some food for thought'¦

 

I have my vac sources all tapped into the base at the back of the elbow. I'm hopping mynboost/vac guage hose is just plugged or kinked.

Rick

 

I had to run my EGR spacer so the TB linkage would clear the valve covers. Tapped the back of the EGR spacer and pulled vacuum from there to run the brakes. Worked fine for me.

 

i agree with russel, theoreticaly its kinda like water running around a sharp radius, the water would tend to "skip over " the hole, and what did enter the hole would be turbulant.