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kenewagner
02-03-2010, 10:27 AM
What is the best area to pull vacuum from on the TB plenum. I am not talking about stock plenum locations. I am in the process of re enginnering my TB plenum for the whipple. I am interested in knowing if it makes a diffrence pulling vacuum closer to the TB or closer to the supercharger or it makes no diffence at all. I am trying to make it easier to hook up vacuum lines when installing the supercharger. My overall plan is to build a vacuum manifold that I can run all the diffrent vacuum lines from and feed it with one line from the TB plenum. I could clean up a lot of the mess on the firewall and have one vacuum line to attach to the TB plenum rather than multiple ones that are hard to reach and hook up as the supercharger is being set on the intake. Any ideas, thoughts???

Ken

artic94sc
02-03-2010, 11:24 AM
would really be interested in your design bro....

ricardoa1
02-03-2010, 11:48 AM
I dont think it makes a different Ken closer to the TB or SC. That area will get the same amount of VAC.

kenewagner
02-03-2010, 01:03 PM
I dont think it makes a different Ken closer to the TB or SC. That area will get the same amount of VAC.

Thats what I am looking for is opinions on if vacuum ports are located where they are for convience or because they are located where they will pull a greater vacuum. Seems to me like it would make no diffrence but assuming gets me in trouble every time

Ken

old_coot
02-03-2010, 01:26 PM
since most of the flow inside the intake runner is toward the back I would put the port on the front side so as not to disturb the flow with eddy current type swirling. If you are trying to maximise vacuum though then a high velocity port on the rear would be the ideal spot. I would keep the flow side as smooth as possible if it was me.............Dan

kenewagner
02-03-2010, 01:58 PM
since most of the flow inside the intake runner is toward the back I would put the port on the front side so as not to disturb the flow with eddy current type swirling. If you are trying to maximise vacuum though then a high velocity port on the rear would be the ideal spot. I would keep the flow side as smooth as possible if it was me.............Dan

Nothing would be sticking into the flow of air. Just a hole with a threaded alu coupler welded over.

So you are saying that there are better areas where vacuum would be higher than others? Hate to pull off the back if I could avoid that. I do have one vacuum port there already I could use if I decided to go there.

Ken

David Neibert
02-03-2010, 03:10 PM
Ken,

I don't think it matters where you position the vacuum nipples, so long as it's after the TB and prior to the supercharger inlet, vacuum readings should be the same.

Suggest adding an extra port for a vacuum test gauge to see if you are getting any inlet restrictions at WOT max rpms. I'd really love to see some test data on that blower with an 85mm TB.

David

kenewagner
02-03-2010, 03:25 PM
Ken,

I don't think it matters where you position the vacuum nipples, so long as it's after the TB and prior to the supercharger inlet, vacuum readings should be the same.

Suggest adding an extra port for a vacuum test gauge to see if you are getting any inlet restrictions at WOT max rpms. I'd really love to see some test data on that blower with an 85mm TB.

David

I have (3) vacuum ports on the top (see picture) I was only using one of them since I moved the bypass vacuum line to the return intake plenum from one of those fittings. I will leave one open and use the other to feed a vacuum manifold. I just want to figure a way to simplify all these vacuum lines into one spot and than supply one line or maybe 2 to that manifold using AN fittings so that there is more easy to installing and removing the blower.

With a vacuum line fitted to the tb plenum and at WOT, what kind of reading am I looking for?

Ken

old_coot
02-03-2010, 04:05 PM
Any obstruction whether it be a protrusion into the path or an absence of wall will cause a decrease in overall flow----I would put the port on the low speed side of the port which should be the inside of the curve....Dan

David Neibert
02-03-2010, 05:22 PM
With a vacuum line fitted to the tb plenum and at WOT, what kind of reading am I looking for?


Ken,

You are looking for vacuum, as a measurement of restriction to the blower inlet. In a perfect world, there would be no restrictions (vacuum) in the inlet plenum at wide open throttle max blower and engine rpms. I would expect you to find the highest amount of vacuum in the inlet plenum and readings taken at various points of the inlet system (includes air filter, mass air meter, air intake pipe, throttle body and inlet plenum) will gradually show less and less vacuum/restriction the further away from the plenum and closer to the air filter you get. If you are showing the same restriction/vacuum between the air filter and mass air meter as you are in the inlet plenum, that would indicate the air filter is really the problem.

Any measurable restriction (even 1 inch of vacuum) will cause a reduction in blower efficiency. I know the 85mm TB is not large enough to flow the full CFM the 2.3 blower is capable of moving at max blower rpms without creating a restriction, but I don't know if it's going to be a restriction at the blower speeds/CFM we are likely to be moving to achieve 22 pounds of boost on a heavy breathing 3.8 SC motor that is limited to 6500 rpms. Might be a different story at 7500 rpms.

I don't have the data to back it up, but I suspect we will find that ultimately the heads are going to be a bigger restriction than the 85mm TB, especially on a high revving 4.2/4.3 motor.

David