Vacuum Manifold Replacement

[Flash517]

Is it possible to replace the Vac Manifold/Tree with an aftermarket one like this https://tinyurl.com/y4cuc6oy, I happen to have one already from a previous project and wouldn't mind using it.

[John Brennan]

Is it possible to replace the Vac Manifold/Tree with an aftermarket one like this https://tinyurl.com/y4cuc6oy, I happen to have one already from a previous project and wouldn't mind using it.

Sure-- anything with the right number/size of bayonets will do. It's just air pressure, and a way to control it.

[my8950]

Where is this part from?

[hEaT]

I made my own and threw it behind the false firewall. Easy to do.

I used this:

https://www.amazon.com/gp/product/B00AKVF6FI/

And then used the appropriate thread-in fittings with hose barb ends. Also lets you convert any critical vacuum lines to -AN braided if desired.

[my8950]

I made my own and threw it behind the false firewall. Easy to do.

I used this:

https://www.amazon.com/gp/product/B00AKVF6FI/

And then used the appropriate thread-in fittings with hose barb ends. Also lets you convert any critical vacuum lines to -AN braided if desired.

Interesting...Curious about the diameter being only 1/4" dia. I am not sure about the size of the original, but it seems like if it were a little bigger diameter, it might buffer better. It's working for you though, so...

[thesameguy]

The other side of that argument is that smaller lines react faster, so it's a matter of figuring out what's at the other end, and whether you want fast reaction or more consistent behavior.

[hEaT]

True. Seems to be working well and I get a consistent MAP signal at the ECU.

Similarly, does intake plenum have a similar affect as a vacuum manifold size? I have a BIG plenum on mine welded to an inline lower...vs the stock no plenum at all.

[thesameguy]

It does! Google "intake velocity" for some theory. TL;DR is you want the volume of the intake system to be big enough to pass enough air, but no bigger as excess reduces intake velocity and costs power. There are formulas for right-sizing the intake.

[Ed Lijewski]

True. Seems to be working well and I get a consistent MAP signal at the ECU.

You are running a MAP rather than a BAP?

YMMV

[hEaT]

It does! Google "intake velocity" for some theory. TL;DR is you want the volume of the intake system to be big enough to pass enough air, but no bigger as excess reduces intake velocity and costs power. There are formulas for right-sizing the intake.

Makes sense. I think this one was sized to match engine displacement, but I'd really need to test it and see. It's one of the older 40Bob plenums welded to an inline lower, which a bunch welded onto the runners to port them.

True. Seems to be working well and I get a consistent MAP signal at the ECU.

You are running a MAP rather than a BAP?

YMMV

I have both (Stinger PimpX; MS3x). BAP sensor is inside the ECU case, and 4 bar MAP sensor reason manifold vacuum/pressure.

[thesameguy]

Makes sense. I think this one was sized to match engine displacement, but I'd really need to test it and see. It's one of the older 40Bob plenums welded to an inline lower, which a bunch welded onto the runners to port them.

There are also goal variances between turbo and non-, but I'm not smart enough to remember... I think the gist is that a good size plenum is useful for a turbo as a sort of "pressurized air reserve" whereas wheezy motors care less about the plenum and more about the runners. That would be a search for "intake resonance" - mostly a feature for naturally aspirated motors to achieve greater VE, since turbos don't have a problem getting air into cylinders. But, "intake velocity" and "intake resonance" are surely some good research points for smart people to build a better intake.

(Incidentally, I always wonder about "2.3 tuning parts" since so many tuned 2.3s are circle track motors and not forced induction... two totally different problems!)

[my8950]

I have both (Stinger PimpX; MS3x). BAP sensor is inside the ECU case, and 4 bar MAP sensor reason manifold vacuum/pressure.

Are you running in excess of 35 psi manifold pressure?
I'm not really clear on how the Pimp system works...

[hEaT]

I have both (Stinger PimpX; MS3x). BAP sensor is inside the ECU case, and 4 bar MAP sensor reason manifold vacuum/pressure.

Are you running in excess of 35 psi manifold pressure?
I'm not really clear on how the Pimp system works...

Nope, only at 15psi, but will likely inch up to 17-18. The sensor is absolute (atmospheric pressure is already 1 bar). That gives you 3 bar/44psi of boost potential. No reason not to have it or spec something less. They still read the same level of resolution so there's no benefit of running a 3 bar for instance. My last setup was a 2.5 bar sensor and worked fine, just had to be mindful of overboosting.

[my8950]

I guess I'm curious about what sensor you're using then. I used GM 1/2/3 bar sensors before, 3 bar did not have the same resolution for the map as 2 bar. If I was only going to 10psi, I didn't need a 3bar. Seems like a lot of people just bought 3 bar sensors to pretend they were cool, even though they didn't need them.

[hEaT]

I guess I'm curious about what sensor you're using then. I used GM 1/2/3 bar sensors before, 3 bar did not have the same resolution for the map as 2 bar. If I was only going to 10psi, I didn't need a 3bar. Seems like a lot of people just bought 3 bar sensors to pretend they were cool, even though they didn't need them.

I could open the ECU case and look, but guessing Stinger when they build their kits use this one:

https://www.diyautotune.com/product/map ... orrection/