NEED HELP: Vacuum hose routing - Profec B/C2 boost/FM clamp, etc.

**I think it would be great if we could post some diagrams or even get pictures of how you have your vacuum lines set up.**

Alright, I was trying to install everything this weekend, and I can't get it all to work properly. For one thing, my Autometer C2 boost gauge doesn't read accurately. I can rev the engine and it runs to about 10 PSI without ever moving. It sits at only about -10 PSI vacuum at idle. Also, when I shift about 8 PSI on the Greddy Profec B, the Autometer C2 is reading about 14-15 PSI, and my old manual boost gauge is only reading about 6-7 PSI. It is driving me insane. I will explain how I have it routed currently.

At first, I had a long vacuum hose running from the "brake booster" line, I guess it is called. This is the vacuum line on the top of the engine at the rear, closest to the firewall. I ran a T there, and ran it into my interior, where it split to another T immediately and ran into the C2 electronic boost module with a vacuum hose (as well as with the thin plastic tubing it came with, no difference with either hose), then it runs over to another T behind my center console, where it runs up to the Greddy vacuum filter then into the Profec B Spec II unit; finally, it runs from that T over to the Flying Miata FM clamp/O2 signal modifier (not wired up to the ECM yet). The other vacuum line runs down to the stock T, which splits to the Greddy boost controller valve, then down to the wastegate and over to the stock BPV (sold the hardpipes and HKS BOV).

So yeah, with this setup, my boost was holding fairly steadily, but the stumbling problem I have been having was there, feeling like a boost/vacuum leak. My gauges are obviously reading all differently also.

I switched this late last night, so everything is running off the same vacuum line now. I just pulled the hose that ran down to the wastegate, and moved the T over so everything is in-line. I was told by some people who have done some extreme turbo tuning that it is best to have everything run off of one vacuum line. My gauges still don't read accurately, and I am in fear of over-boosting. This morning on the way to work (5:30 in the bloody AM, cool air), Profec B was spiking to 8.5-8.7 PSI?!

I really need help. If people could post their vacuum diagrams, this could be a valuable resource, like the MPI and Profec B Spec II maps I have been creating Word documents to help tune with. I know others have problems with the C2 gauge not reading properly, so this would help a lot of people.
Thanks very much!!
Nic
nictlg7@yahoo.com

Here is how I have mine set up:

505zoom said:

Here is how I have mine set up:

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What size is the line, 3/8???? I need to setup a temp thing until I get the distribution block.

Bigg Tim said:

What size is the line, 3/8???? I need to setup a temp thing until I get the distribution block.

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I want the distribution block too! I was told this was the best method by a bunch of RX-7 gurus (different times). I actually have this diagrahm printed from when I was running a BOV/BPV setup and wanted to get it running properly. Do you have one dedicated line running to the wastegate, or does that line also have the boost controller on it? If I run a line from the front vacuum hose down to the Greddy boost controller valve, then down to the wastegate, and run everything else off that rear vacuum line, I shouldn't have any problems? Does it matter if I mount the C2 boost control unit in the engine bay close to the intake manifold, or on the interior further away? Does it matter how many things are in the same vacuum line? Thanks!!

nictlg7 said:

...Do you have one dedicated line running to the wastegate, or does that line also have the boost controller on it?


If I run a line from the front vacuum hose down to the Greddy boost controller valve, then down to the wastegate, and run everything else off that rear vacuum line, I shouldn't have any problems?


Does it matter if I mount the C2 boost control unit in the engine bay close to the intake manifold, or on the interior further away?


Does it matter how many things are in the same vacuum line? Thanks!!

Click to expand...

I have that line running to the controller, and then to the wastegate.


I think that would clear up some of your issues. It sounds to me like you just have too much on that single source right now.


I would mount the box as close to the manifold as you can. It is better to send a longer electrical signal than it is to send a longer mechanical signal. It shouldn't matter too much either way though.


I have found that at least with my car, it all works better if you have as little on each source as possible. The BB line is by far the strongest, and I reccomend tapping into that as much as you can.

505zoom said:

I have that line running to the controller, and then to the wastegate.


I think that would clear up some of your issues. It sounds to me like you just have too much on that single source right now.


I would mount the box as close to the manifold as you can. It is better to send a longer electrical signal than it is to send a longer mechanical signal. It shouldn't matter too much either way though.


I have found that at least with my car, it all works better if you have as little on each source as possible. The BB line is by far the strongest, and I reccomend tapping into that as much as you can.

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So what's the size of it?

Bigg Tim said:

So what's the size of it?

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Sorry man, I was hoping someone else would field that one. I got a variety pack of T's and it has been so long since I put it in I don't remember. It is smaller than it looks from the outside though, because there is a thick sleeve on it. I'll go out and measure for you later when I pull the car out of the garage.

3/8" is sounding about right to me though.

505zoom said:

3/8" is sounding about right to me though.

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Cool, I thought it looked like 3/8 hose. I'll find out tomorrow when I cut it.

GReddy's install instructions for the Profec-B Spec II internal wastegate setup are screwed up. It might've gotten fudged up when translating from japanese to english. just incase it may be the issue check your connections going to the solenoid and wastegate itself.

Interesting, I will have to check that out. This is all good info. Thanks everyone.

So do you think I should run a seperate line for the wastegate and boost controller, or is it best to have everything on one vacuum line, or what? Also, is it better to use the front or rear vacuum line (on top of the intake manifold, or behind near the firewall?).
Thanks!