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Old 01-22-2009, 04:39 AM   #1
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Default Vaccuum block a solution for strong boost signal?

I've read more than one thread from people trying to get a good strong boost signal to their MS and that has gotten me thinking.. I seem to have a good vac signal to my MS - the line is straight off the intake manifold and has no T's or anything, but my MAP does oscillate a bit according to my datalogs and I wonder if an even cleaner signal could be had... also, my boost gauge is not spot on accurate - it seems to read just about 1 psi lower than what the MS is seeing. The vac line for my boost gauge T's into the same line that supplies my FPR.. So I got to wondering if using a Vac distribution block could ensure a clean MAP signal to the MS, boost gauge, FPR, etc. better than all these T's and stuff and if buying one would be worth it... anyone's thoughts?

If I knew how to take a screenshot I would take one of a datalog to show what I mean about my MAP oscillations.
-Ryan
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Old 01-22-2009, 07:07 AM   #2
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on the ms pages theres a solution to this

they recommend taking a good old fashioned fuel filter and putting that inline from the mani to the map sensor

i have jsut run a really long pipe and looped it and it worked well for me
try the fuel filter and post back if it solves it
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Old 01-22-2009, 07:47 AM   #3
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I will give that a shot but I am also very curious about why my boost gauge (jackson racing brand if it matters) is reading lower than what MS tells me the car is seeing..
On partial throttle, when I start hearing the turbo begin to do some work and the MS is registering 0 - 0.5 psi, the gauge is pointing at -2 psi. At full boost if I have the car set for 7 psi according to MS, the boost gauge will only go up to 6 psi. This seems to me that perhaps T'ing off an existing vac line is not the optimal way to supply things like the gauge or the FPR with vac signal... this is why I was looking into the vacuum blocks..
I liked the look of the one Tuner Toyz was selling but their website now says the 'merchant's store has been closed'...

-Ryan
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Old 01-22-2009, 08:39 AM   #4
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Differences in calibration and/or accuracy (and resolution) of the design. If you try a third gauge, you will either get a consensus with one of your other gauges or a third answer entirely.

I have three dial type tire pressure gauges (one in each of three different vehicles) and they have a 4 psi variance between them. Go figure.
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Old 01-22-2009, 09:48 AM   #5
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I was going to post this same question today. Begi says to cut into the line going to the brake booster before the check valve and install their "line tap". I was wondering if the vacuum signal is the same everywhere, whether pulled from the booster line or the manifold. At this time, I only need vacuum for the recirc BOV.
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Old 01-22-2009, 09:51 AM   #6
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use the boost gauge as an idiot light, the accuracy isn't really important like it is for temperature gauges.
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Old 01-22-2009, 10:14 AM   #7
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I had my gauge and ECU tapped into the brake booster line and didn't like it. You could even see in the datalogs each time that I hit and released the brakes. It's also not a good idea to share a vac port between the BOV and ECU, that caused some really wacky stuff when I was at part throttle just enough to make the BOV bounce a bit. I finally tapped two 1/8 NPT holes on top of my manifold. One offset a little from the PCV line with a T on it for the gauge and BOV, and one by itself offset a little from where the brake booster connects for the computer.
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Old 01-22-2009, 11:09 AM   #8
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Quote:
Originally Posted by DammitBeavis View Post
I finally tapped two 1/8 NPT holes on top of my manifold. One offset a little from the PCV line with a T on it for the gauge and BOV, and one by itself offset a little from where the brake booster connects for the computer.
I have the vacuum line from my cruise control and there is the extra plugged line on the front of the IM near the TB. Can either or both of these be used with equal success? Also, what about an old style vacuum cannister in line to stabilize the vacuum?
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Old 01-22-2009, 12:20 PM   #9
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Quote:
Originally Posted by Stein View Post
I have the vacuum line from my cruise control and there is the extra plugged line on the front of the IM near the TB. Can either or both of these be used with equal success? Also, what about an old style vacuum cannister in line to stabilize the vacuum?
Not sure about the other ports. IIRC some of them weren't beaded so you might have trouble with hoses popping off under boost. Make sure they have sufficient flow (not just a pinhole) and that they don't have an internal check valve or anything.

You don't want to 'stabilize' the vac, a vac canister will dampen and really slow the response. That would cause even more problems. You just want a good reliable representation of the current manifold pressure.
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Old 01-22-2009, 12:50 PM   #10
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Quote:
Originally Posted by DammitBeavis View Post

You don't want to 'stabilize' the vac, a vac canister will dampen and really slow the response. That would cause even more problems. You just want a good reliable representation of the current manifold pressure.
I think that I am getting confused here. Vacuum is different from manifold pressure, right? I mean, manifold pressure can go from negative to positive, depending on whether you are in boost or not. This obviously won't work for, say the brake booster which is vacuum only. The BOV needs to be attached to vacuum. I guess that is why Begi cuts it into the brake booster line. Vacuum all the time. Positive pressure would be bad, right?
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Old 01-22-2009, 12:58 PM   #11
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Quote:
Originally Posted by Stein View Post
I think that I am getting confused here. Vacuum is different from manifold pressure, right? I mean, manifold pressure can go from negative to positive, depending on whether you are in boost or not. This obviously won't work for, say the brake booster which is vacuum only. The BOV needs to be attached to vacuum. I guess that is why Begi cuts it into the brake booster line. Vacuum all the time. Positive pressure would be bad, right?
I think all the attachments and fixtures you buy for these purposes are called "vacuum" parts because that is all they would be used for in most applications. We are not normal...

Positive pressure for the BOV is not bad, it's actually helpful for keeping the valve closed. I *think* the check valve for the brake booster is very close to the booster itself, leaving plenty of room for your BOV attachment before that check valve.
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Old 01-22-2009, 12:59 PM   #12
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As for a signal to MS, you want a very small diameter vacuum hose going from the back of the manifold to the MS. You don't want a "strong" signal. You just want a smooth signal as to reduce noise and keep acceleration enrichments from coming on. As mentioned, a filter inline helps to damp the signal. Running a huge line to MS would be a bad idea. Oh, and this topic has been beat to death by the way.
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Old 01-22-2009, 01:00 PM   #13
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vacuum blocks FTW.

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Old 01-22-2009, 01:02 PM   #14
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Yeah there is some confusion and I'm partially responsible, sorry.

The ECU, Boost Gauge, and BOV need to see manifold pressure.
The brake booster, cruise control, emissions stuff and VICS need to see vac only.

For an accurate signal to the ECU, you need a narrow ID hose attached to an independent tap on the manifold to reference manifold pressure.

For things that need vac only you can install a check valve and a vac canister to ensure that they still have vac while the manifold is under pressure from the turbo.
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Old 01-22-2009, 01:25 PM   #15
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Quote:
Originally Posted by Braineack View Post
vacuum blocks FTW.

can you post a pic from further away, at lower resolution, with less detail please?

I assume you have a perfect MAP signal too?
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Old 01-22-2009, 01:43 PM   #16
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I wanted to purchase the TunerToys vacuum block,but it looks like they are out of business,are they even still a sponsor here?
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Old 01-22-2009, 01:45 PM   #17
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Quote:
Originally Posted by spike View Post
I wanted to purchase the TunerToys vacuum block,but it looks like they are out of business,are they even still a sponsor here?
TunerToys - Turbocharging, Supercharging, and Performance products for your car!
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Old 01-22-2009, 02:02 PM   #18
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^^ Thanks Pat.
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Old 01-23-2009, 10:08 AM   #19
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Guys, for a vacuum manifold, make your own.

McMaster Carr has all the parts you need.

McMaster-Carr
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