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Old Jan 21, 2009, 08:40 AM
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MDP questions? ?
Can the MDP sensor be used to monitor vacuum conditions?

I ask this because I cannot get a vacuum reading. Boost (MDP) in EvoScan reads in the 50s at idle which I know is incorrect because of the vacuum condition at idle.

I assume most of you will tell me to get the JDM MAP sensor and be done with it.
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Old Jan 21, 2009, 10:24 AM
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Originally Posted by Appauldd
Can the MDP sensor be used to monitor vacuum conditions?

I ask this because I cannot get a vacuum reading. Boost (MDP) in EvoScan reads in the 50s at idle which I know is incorrect because of the vacuum condition at idle.

I assume most of you will tell me to get the JDM MAP sensor and be done with it.
nope. i think all of our sensors are MAP only even the stocker. thats why the map to maf patch is really just a MAF emulator-this misguided me when i originally ported the stuff over.

would be great is there was a two way pressure sensor heh....

correct me if i'm wrong please.

EDIT: please do tell me there is vacume resolution on the JDM 3bar and i'm wrong. if so, i'm buying one right now.
Last edited by evoredy; Jan 21, 2009 at 10:27 AM.
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Old Jan 21, 2009, 11:57 AM
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^MAP sensors measure absolute pressure. From -14.7 and up. Meaning vacuum is seen as pressure by them. So yes there is vacuum resolution, if that's what you're asking about JDM MAP...

OP, stock MDP is a 1 bar, meaning it should show vacuum values.. Maybe Evoscan calculation/address is wrong?
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Old Jan 21, 2009, 12:08 PM
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Originally Posted by mplspilot
^MAP sensors measure absolute pressure. From -14.7 and up. Meaning vacuum is seen as pressure by them. So yes there is vacuum resolution, if that's what you're asking about JDM MAP...

OP, stock MDP is a 1 bar, meaning it should show vacuum values.. Maybe Evoscan calculation/address is wrong?

what should the EvoScan calc be???
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Old Jan 21, 2009, 02:23 PM
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Originally Posted by mplspilot
^MAP sensors measure absolute pressure. From -14.7 and up. Meaning vacuum is seen as pressure by them. So yes there is vacuum resolution, if that's what you're asking about JDM MAP...

OP, stock MDP is a 1 bar, meaning it should show vacuum values.. Maybe Evoscan calculation/address is wrong?
i never quite understood that. i *thought when the pressure between the vacume source and sensor equalized from negatives to 0psi, then the map sensor would report accurate values after that point to 14.7psi say for a stocker 1bar. i'm seeing this in my logs.

to OP, i get your same issue when logging the MAP with evoscan--i gave up a while ago lol. i'll check this out in detail again tonight.

thanks
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Old Jan 21, 2009, 02:35 PM
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atmo isn't 0v on the MAP sensor, its like 1.6v.

so anything under 1.6v is considered vacuum.

I dont know what formula to convert -psi into hg/mm (orwhatever vacuum is measured in)
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Old Jan 21, 2009, 02:49 PM
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Originally Posted by tephra
atmo isn't 0v on the MAP sensor, its like 1.6v.

so anything under 1.6v is considered vacuum.

I dont know what formula to convert -psi into hg/mm (orwhatever vacuum is measured in)
1.6 on a 3bar MAP

i have the crappy usdm MAP. it's a hair under 4v or so it says lol.

i tried manipulting the cal tables a while ago to the usdm linear curve, but i still couldn't get proper vacume tunability [with bez's code]. i'll try again as maybe i gave up too quick lol.
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Old Jan 21, 2009, 03:41 PM
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Originally Posted by tephra
I dont know what formula to convert -psi into hg/mm (orwhatever vacuum is measured in)
Multiply psi by 2.036 (or to make it simple, just 2) to get in. hg.
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Old Jan 21, 2009, 07:29 PM
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My question still remains......what should the proper calculation be set as in EvoScan for reading the MDP???
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Old Jan 21, 2009, 07:42 PM
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depends on the MDP. what one is it?
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Old Jan 21, 2009, 07:44 PM
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Originally Posted by tephra
depends on the MDP. what one is it?

Stock

The reason for my request is because I am working on the MAP to MAF patch. I have my car running pretty well but I cannot get accurate with VE if I don't have accurate vacuum.
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Old Jan 21, 2009, 07:54 PM
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what the 1bar version?
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Old Jan 21, 2009, 07:56 PM
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Originally Posted by tephra
what the 1bar version?
Yes.

I am also running the 94170015 with your 5.10 mods. You really are the man!
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Old Jan 21, 2009, 08:09 PM
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hrmm not sure what the scaling for the 1bar map sensor is. actually isn't it in evoscan already?
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Old Jan 21, 2009, 08:11 PM
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Thats the problem. I cannot get a vacuum reading. The Boost(MDP) setting in EvoScan never goes negative. At idle it hovers in the 30s.
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