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Old 09-08-2008, 04:27 PM   #1
#522
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Default Map Sensor Voltage Clamp Question

I have seen various voltages specified for this when running forced induction. It has no effect on timing in the 4v-4.7v range, but does effect fueling.

My question is: Am I supposed to clamp it at the voltage it registers at 0 PSI, or just clamp it around the 4.7 mark to prevent the CEL? My Sensor is at 3.85 at 0 psi/atmosphere. I was never to clear on this.

Thanks,
Ron
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Old 09-08-2008, 07:18 PM   #2
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I wouldnt use a voltage clamp at all. Its not very safe or effective.
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Old 09-08-2008, 07:50 PM   #3
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True, I am using an E-Manage Ultimate to do this, so not just the regular voltage clamps. I am just wondering if it is the goal to stop the voltage right before the ca sensor max's out, or to clamp voltage just as the car sees 0 psi.
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Old 09-08-2008, 09:29 PM   #4
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Well really it is up to you.

You could clamp it when you see boost, then tune with the greddy map sensor.

Or you could clamp it right before it maxes out then tune with the greddy map sensor.

Either way you are just doing it just so the stock ecu doesn't freak out.

Are you maxing out the stock maf right now?
I'm assuming you are using the stock maf also...
Do you have the Greddy map sensor?
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Old 09-08-2008, 09:45 PM   #5
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Since he has an 01 RS. I guessing he isn't worried about a MAF. Since it's a MAP car.
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Old 09-08-2008, 10:51 PM   #6
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Sorry, I should have included more details, but yes, 01 RS, MAP sensor stock with Emanage Ult with greddy map sensor to tune boost. I have more info in the Emanage Ultimate on MAP based RS's thread as well.

I was just wondering if there was any advantage to either method. Didn't know if it was better to take the factory ecu and MAP sensor out of the equation once into positive manifold pressure and take over from there with the EMU, or let it do it's thing until it reaches max voltage and then take over.

Thanks.
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Old 09-08-2008, 11:58 PM   #7
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oh ok, yeah i forgot about the whole map car thing.

I wouldn't really think that it would make any difference either way you did it. But I have never done it so I'm not positive.
The greddy sensor might be less accurate then the stock one because it covers such a large range of pressures...so it might be beneficial to use the stock map until it almost reaches max voltage
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Old 09-09-2008, 01:56 AM   #8
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How are you maps set up? Map voltage vs. RPM, or Boost vs. RPM?

I would think you would want Boost vs. RPM and then cap the MAP voltage at 0 psi. This way your ECU thinks your humming along at that steady state and just run timing and fueling off the greddy map sensor in boost.

I don't know for sure though because I have a MAF car, but this is how I would try it and see how it works.
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Old 09-09-2008, 12:27 PM   #9
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Thanks. I saw that you did that on your MAF car (morrocco88) and had good results.
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Old 09-10-2008, 10:34 PM   #10
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The most important thing here is to clamp it before you hit 5psi. The reason for this is that is the point at which the voltage you will pop the MAP. Once you do that, the car will run like crap because the ECU throws it into limp mode. Optimumly you want to clamp it low enough that it won't pop the CEL.
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Old 09-10-2008, 11:28 PM   #11
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Quote:
Originally Posted by Matt Monson View Post
The most important thing here is to clamp it before you hit 5psi. The reason for this is that is the point at which the voltage you will pop the MAP. Once you do that, the car will run like crap because the ECU throws it into limp mode. Optimumly you want to clamp it low enough that it won't pop the CEL.
4.7 volts on a 2000/2001 RS
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Old 09-10-2008, 11:52 PM   #12
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ok, so it is let it do it's thing until 4.7 and then clamp it, what I figured but just wanted to be sure. I guess I was overthinking it. Good to know it will actually damage it if the voltage exceeds 4.7.
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