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possible to trick the rtek into using a 3 bar map sensor?

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Old 05-04-16, 02:04 AM
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Question possible to trick the rtek into using a 3 bar map sensor?

I was doing some thinking, since I would like to run a bit more than 14psi and this seems like something that should work given the proper sensor and tuning.

The rtek uses the stock map sensor which is limited to 14.7 psi and the tuning tables reflect that.

I believe that the stock sensor uses a 0-5v signal to convey 0-2 bars. It seems that you could use a 0-5v output 3 bar map sensor and simply modify your tables to suit, even through they would still say 14.7 psi, they would effectively measure to 29.4.

So (table pressure)=>(actual pressure) -14.7=-14.7, 0=7.35, 14.7=29.4 etc.

Has anyone tried this? Can anyone see why this wouldn't work? The only downside I can see is a loss in map resolution.
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Old 05-04-16, 08:02 AM
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i'm not surprised you have the same ideas as me, as im sure your not surprise i've been looking down this path for my upgrade to a 7670.
I'm ok with the ecu thinking 30 psi is 15 psi. the problem is the scale of the vacuum range..
the good news is i have a snap on scope at my dispoal now so i will be making a thead on how to do this vary thing with all the good info. the biggest thing is 0 psi may not be at 0 it may be 5 psi or -5 on the ecu.. i just have to find out the full scale with the scope.
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Old 05-04-16, 10:25 AM
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Here you go.

Edit: I swore this was a 3 Bar MSD sensor but it appears to be a 2 bar.
Attached Files
File Type: xls
MSD Map Vs stock Map.xls (18.5 KB, 28 views)

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Old 05-04-16, 12:24 PM
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so stock is really 2v to 5v. and after market is 0v to 5v. so electronic trickery is needed. noted.
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Old 05-04-16, 12:42 PM
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Im pretty happy with my td06 turbo, it spools quick and has plenty of work left in it.

Looking at GM 3 bar map sensor pressure-voltage chart, it seems to be extremely linear through the entire range. So long as the factory sensor operates in the same fashion, it should be a work well. I'll take a look at that spreadsheet when I get home, phone won't open it.

I'm actually surprised that this hasn't been explored previously (atleast not that I've come across). It would make the airflow meter the only real bottleneck for the rtek.
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Old 05-05-16, 08:34 AM
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It looks like to use a typical 3 bar map sensor you would have to use a voltage divider to drop the map output signal to 0-3v then bump it with a +1.8v offset. Then voila! 1.8-4.8v signal that translates 3 bars of pressure. I'll see if I can mock the circuit up at school today.
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Old 05-05-16, 11:30 AM
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It has been explored....and determined the gains weren't worth it.

The problem I see is what does your proposed circuit do to the 0psi point? Maybe it will work fine, but I'm not sure what will happen if you change the voltage that the zero PSI point occurs.
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Old 05-05-16, 05:37 PM
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I worked at it a little and was able to a fairly linear conversion based on the table you provided. It wasn't perfect but it looked like you could retain the factory start and zero values while extending pressure measurement ability to 20-25 psi. Granted this is without building an actual circuit.

What has caught my attention from looking into this is that the stock map sensor tops out measurement by 10 psi.. So any boost based tuning done above that is null..
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