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Old 09-25-2002, 10:35 PM   #1
Austin
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Default MAP Sensor Placement

Wouldn't it be nice to have an aftermarket ECU forum? Then I could've put this in there...

I want to pipe my TEC3's GM 3bar MAP sensor directly into the intake manifold. I want the shortest distance between the manifold wall and the pressure bellows in the MAP sensor.

For a while I ran with an 18" hose connecting my MAP sensor to the intake manifold. It caused alot of super low-load surging and around-town type problems. Not even problems, really... just annoying ticks.

I switched to a ~4" hose connecting the MAP sensor to the intake manifold, and the problems are almost fixed...

I think I'll be very happy if I can get my GM map sensor in a similar position to the stock map sensor - connected directly to the manifold. How can I do it?
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Old 09-26-2002, 01:26 AM   #2
WizardBlackWRX
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Are you running it from a tap by itself?
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Old 09-26-2002, 02:05 AM   #3
Austin
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Yes, my MAP sensor has it's own private nipple.
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Old 09-26-2002, 02:59 AM   #4
WizardBlackWRX
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Hmm, I can't really see how you could get less than 4" or so. If you keep it at that, you might be able to get it to an unused boss on the manifold. On mine, I need about 4" and then it gets me to a boss, but I know the holes in the MAP sensor body are pretty small.
Where'd you tap you nipple at? I did mine below the TB.
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Old 09-26-2002, 03:15 AM   #5
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I had the same question when I hooked up mine. I simply connected it to the FPR vacuum line using an adaptor to make the hose smaller.

You'll have to take a reading off the intake manifold (after the TB) to get a proper reading. I'm thinking either the one from the front which connects to the idle system or the FPR.

I don't know of any other connections...
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Old 09-26-2002, 09:53 AM   #6
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Default Re: MAP Sensor Placement

Quote:
Originally posted by Austin
Wouldn't it be nice to have an aftermarket ECU forum? Then I could've put this in there...
Hey bizotch! I'm working on it, damnit!
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Old 09-26-2002, 01:39 PM   #7
Austin
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Quote:
Originally posted by ScoobieSnaX
I don't know of any other connections...
Every vacuum nipple on the intake manifold is a viable connection. There's the small nipple above cylinder #1 intake runner (front passenger)(I use this for my FPR), two nipples in the center of the manifold opposite the throttle body (one of these is where my MAP sensor is from, the other I use for a boost guage), and one nipple below the throttle body, opposite the PCV valve (I use that one for the bov). There's also the huge nipple on the intake runner for cylinder #4 for brake vacuum assist.

Ideally, you want your MAP sensor to come off it's own nipple with the shortest possible hose.

What I'm asking is how to make my hose shorter or do away with it altogether, or how to safely connect a plastic bodied sensor directly to the intake manifold.
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Old 09-26-2002, 01:41 PM   #8
Austin
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Default Re: Re: MAP Sensor Placement

Quote:
Originally posted by 8Complex
Hey bizotch! I'm working on it, damnit!
Was that hint not subtle enough? hehe...
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Old 09-26-2002, 04:55 PM   #9
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Are you guys saying that the stock MAP sensor is not mounted directly to the throttle body and there is actually a hose going to it? Please confirm how the stock MAP sensor receives its pressure signal...

Thanks,
JC
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Old 09-26-2002, 05:07 PM   #10
Austin
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Quote:
Originally posted by thejean
Are you guys saying that the stock MAP sensor is not mounted directly to the throttle body and there is actually a hose going to it? Please confirm how the stock MAP sensor receives its pressure signal...

Thanks,
JC
No, I'm talking about an aftermarket MAP sensor. I tried to make that clear so I wouldn't confuse anyone...

The stock MAP sensor is directly mounted to the throttle body.
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Old 09-26-2002, 05:11 PM   #11
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Ok, thought so. You had me excited for a minute there. Thanks for clearing up.

JC
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Old 09-26-2002, 06:22 PM   #12
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Austin - as you long as you give it a good strong signal, it need to have its own vacuum port, though admittedly it is ideal...the FPR (one fo the strongest sources of vaccum on the cr) works well too.

I would try to keep the MAP on the firewall somplace...and make sure you install it correctly (nipple pointed straight down)

Adam
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Old 09-26-2002, 06:36 PM   #13
Austin
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Thanks Adam.

Right now it is mounted with the nipple pointing down.

I can't see how it would help if I mount it on the firewall. That would require (minimum) at least a 12" hose... and I want a 0" hose.
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Old 09-26-2002, 07:15 PM   #14
Z1 Performance
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I jsut prefer giving the MAP a vibration-free environment, so usually mount it on the firewall alnd use a rubber o-ring to insulate it...seems to react a tad faster this way...maybe it's all in my head though.

Why would it be 12" on hose though....firewall to back of intake manifold would only be roughly 5-6 inches? Or do you already ahve a dedicated port you had in mind to get signal from?
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Old 09-26-2002, 09:17 PM   #15
Austin
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Adam - I honestly don't see how you could get from the manifold to the firewall with anything less than 12" of hose...

This is where I had my MAP sensor mounted, and the nipple I was using. There was maybe 4-5" of hose between the end of the manifold nipple and the nipple on the MAP sensor. There was no other load coming off this vacuum line.

I think this is just a bad nipple to use for a MAP sensor. I just moved my MAP sensor, and now the BOV uses the nipple in the pic below and my MAP sensor has a 3" hose from the nipple opposite the PCV valve, below and to the driver's side of the throttle body. It opens directly into the manifold.

The reason I think the nipple in the pic is bad to use, is that if you take the TB off the manifold and look inside, that nipple extends to directly in the middle of the center of the manifold. Seems like it'd give a very accurate reading - it's piped in so that it's equidistant from all four runners, but it adds at least another 6 - 8" lenth of tubing the air must fight.

Now I'll go for a drive and see if this helped any
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