99+ VICS reroute, plus question - Miata Turbo Forum - Boost cars, acquire cats.

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Old 01-13-2008, 02:28 AM   #1
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Default 99+ VICS reroute, plus question

OMG! The routing on the VICS is so dumb. It runs back and forth across the manifold a bunch of times. No idea why.



So here I was, looking at this mess, thinking, where do all these lines go (got the carbon canister system down to ONE LINE).

The VICS stuff was crazy, here:

Ok, Vacuum, from the purple line starting at the front of the motor, goes into the curl of the intake manifold, through a check valve. Then it enters a nipple and takes an isolated but internal channel (blue line) though the manifold, comming out on the "outside" of the curl. There (green line) another hose leads to the valve. The electrically controlled valve closes, allowing the vacuum to pass along another long hose (red) to the opperating solenoid, mere inches from where it started.



Here, I let the electrons do the walking. I bent the tab for the holder for holding the holder for holding the hose that went to the VICS solenoid (itself held by another holder bolted to a bracket bolted to the manifold), and reused the check valve.

How all this functions in boost, I have no idea. It seems to me you're going to be in boost for a LONG TIME come 4000 rpm, and with no vacuum on the line, what's to open the flappers. So, I guess I'll get VICS-power when I'm cruising at vacuum on the freeway, sometimes. Kinda annoyed about it.

I want to make a vacuum resivoir out of maybe the brake assist, but every time I buy a PCV valve, they leak like crazy. I honestly couldn't tell which way was "open" on the one I got. I tried and tried.

Anyone have a suggestion for a resivoir for all my vacuum powered devices?
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Old 01-13-2008, 09:29 AM   #2
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i'm gonna just gut that intake mani and see what happens. if i lose power i'll put the spare on.
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Old 01-13-2008, 03:22 PM   #3
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Gut the spare, then. :-)

There are a few graphs of what VICS does for you - it makes sense, at least. It's not as dramatic as I was hoping for, though. Really, you want runners that get shorter linearly, and have a very sharp response.


Anyway, long before I would gut an OEM one, I would build a proper log manifold. At least for those the theory is easy, and there's not even a chance of restriction. If it works well, port the head to match. People do it, but the gains in increased flow only happen above some certain HP range, below that the gains from resonances outweigh the losses from restrictions.

Now I just need to figure out when to "fire" the solenoid. Looking around (thanks to being pointed there by helpful MT.net users), I've seen graphs of where you get more power in each mode:
N/A it crossed at 5,500
11 psi it crossed at 5,000

The factory switch point is at 5,250 or so.

I might try to find a dyno, or maybe I could somehow log my OEM airflow meter, and try to figure out the best place to switch it. That would at least remove factors of "tune" from the equation. The intake's job is to get in as much air as possible, the tuner's job is to do something useful with it.


Back on topic: The cruise control is also vacuum opperated. Maybe I could use the fuel tank as a vacuum resivoir? There's already a sensor there for watching it. It's certainly big enough for brakes, cruise control, and VICS. And there's already a check valve I trust going to it.

What do you guys think?
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Old 01-13-2008, 05:09 PM   #4
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Default Going for a ride in my failboat

<short version: Don't do the re-route posted here>

Ha. Awesome. Thinking even Mazda couldn't be that dumb, I decided to fill the pass through with water and see how much it took (in practice, I filled it and saw how much came back out). I think my squirt bottle is 250 cc, maybe 300? Anyway, here:


So, yeah - there's a reasonable vacuum resivoir in the manifold. I still don't like the routing, but it's a good thing. And the check valve, which is OEM, is the only check valve I've ever seen that really really works. Kudos Mazda.

So here's my final instal (for now). I'm still happy with it, shorter lines, etc. But in reality, I doubt it matters.
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Old 01-13-2008, 05:19 PM   #5
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Abe, you need to do some serious house cleaning in your engine bay already, what a bloody mess, even the COP harness looks insane. Glad to know i won't have to copy any new crazy vacuum resevoir system to make my VICS work perfect.
Now just waiting on paul to port out his beast.
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Old 01-13-2008, 05:44 PM   #6
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the porting started today. i'll take some pics and post em in that other thread so as not to hijack abe's mess i mean thread.

seriously though. 1 project at a time man...
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Old 01-13-2008, 06:35 PM   #7
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On project at a time gets boring!

Also, since my injectors I bought didn't fit *GRRRRRRRR* I've got some time to kill.

And it's been a goal of mine to replace the bottom intake manifold, get rid of the FM disaster. The EGR is easier to remove now than when it's on the car, etc.

Yes, it's a lot of ***** to tweak at once, but my only real concern is creating a vacuum leak and blaming a poor idle on big injectors instead of on a leak. But I'll be looking for it.

I also re-routed the BOV signal to something MUCH closer. I worry a bit about feeding it with a small signal line, but I guess it's ok.
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Old 01-14-2008, 03:47 AM   #8
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Here's a question: How much vacuum can you pull on the fuel tank before it implodes? I hooked just a check valve to the manifold, now I'm worried it'll crush.
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