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MAP sensors affect auot transmissions?
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Nico Offline
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Post: #1
MAP sensors affect auot transmissions?
Hi. I have a 98 Doge Dakota. I have a friend who installed an HHO system onto just such a truck not three weeks ago. He put a potentiometer on the MAP sensor in order to tune to the HHO enhanced system. So far so good. The results are being charted but one thing he got very excited about is that going uphill on the 2 Fwy N. His RPMs were 1k fewer than normally going up that fwy at 80 miles an hour.

He attributed this to a better performing engine. I think it was the MAP sensor adjustment. By ajusting the MAP sensor I think you are telling the ECU that there is a smaller load on the engine in order to reduce fuel flow to the engine. Correct me if I am wrong.

But by doing that the transmission kicked into OD and brought the RPMS way down, no? My questions are: Is it damaging to the tranny to operate on wrong data from the MAP sensor? Can you inhibit the flow of gas without fooling sensors that are needed for other systems such as cooling or transmission? What happens if you simply put a regulator on the gas supply line and use that to tune?

Thanks for your help I am trying to get this installed in my truck next.
04-07-2008 03:26 PM
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mike Offline
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RE: MAP sensors affect auot transmissions?
Your analysis of the MAP sensor adjustment is correct. The ECU thinks less gas is needed and drops down it's fuel requirements. However, this should not bother other systems.

Adding HHO causes the petrol to burn more completely adding power. However, it also causes more oxygen to be in the exhaust. The ECU will then "see" a lean condition and add more gas. Oxygen sensor adjustments and MAP adjustments are really just to compensate for this factor. It's really just to get the Air/Fuel ratio back to where it should be, and not too rich.

Further leaning can be done. But that's another subject. We just don't want the ECU to ruin our gains with the HHO.

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04-07-2008 03:58 PM
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Nico Offline
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RE: MAP sensors affect auot transmissions?
mike Wrote:Your analysis of the MAP sensor adjustment is correct. The ECU thinks less gas is needed and drops down it's fuel requirements. However, this should not bother other systems.

Okay. But my if the MAP sensor measures load on the engine, could that tell the ECU to go into OD when their is too much load on the truck to warrant OD being used? If you don't know one way or the other I don't expect you to do my research for me but I would like to leave the question open in order to get it answered. I am definitely installing on my truck I just want to do the fuel adjustment as intelligently as possible.

Also is there any way to lower fuel input without changing any sensors. (Of course you have to put a device on the O2 sensor, but besides that.) Can you simply restrict the gas flow physically? What happens?

Thanks for any answers.
04-08-2008 05:03 PM
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mike Offline
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RE: MAP sensors affect auot transmissions?
I'll leave the MAP question open to others at this point. My two cents worth is though that these adjustments are not that great to cause problems with gear shifting. The author of Tuning For Mileage is a mechanic who has the experience with these things. You might post to mpgmike at mpgresearch.com.

Re restricting the gas flow. I've never heard of this approach being used. I suspect that it would cause the engine to stutter rather than smoothly gain or lose power. But again, I'm not expert to answer this question for you.

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04-08-2008 08:52 PM
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colchiro Offline
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RE: MAP sensors affect auot transmissions?
If you restrict the gas flow (lowering the fuel pressure), the ecu will just hold the injectors open longer and maintain the same air/fuel ratio. If you restrict more, eventually you'll throw a code. If you restrict even more, as Mike suggested, you'll have driveability issues.

This is the opposite of one way to convert to E85 (increasing the fuel pressure). E85 needs about 25% more fuel to keep the ecu happy and in some instances, this little bit is all it takes.

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(This post was last modified: 04-08-2008 09:13 PM by colchiro.)
04-08-2008 09:07 PM
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Nico Offline
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RE: MAP sensors affect auot transmissions?
colchiro Wrote:If you restrict the gas flow (lowering the fuel pressure), the ecu will just hold the injectors open longer and maintain the same air/fuel ratio. If you restrict more, eventually you'll throw a code. If you restrict even more, as Mike suggested, you'll have driveability issues.

Okay. That answers that question. Thanks. I will let you know how goes.
04-09-2008 07:53 PM
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AlexR Offline
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RE: MAP sensors affect auot transmissions?
Nico,

The fuel injectors are also designed to operate at a certain fuel pressure to produce a decent spray. I think reducing the fuel pressure would lead the the fuel slobbering out of the injector instead of spraying the way that they were designed to do. Also depends on how much you drop the fuel pressure, 1 or 2 psi or so may be OK, but a significant amount would create problems. One of them being your fuel pump working harder than intended. If you want to try dropping the fuel pressure, perhaps change the way the fuel returns back to the tank from the fuel rail, this would reduce your pressure.

Do post your results if you try anything.

Alex

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04-09-2008 08:55 PM
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