Talk about the tools we use to give GREAT mileage on engines.
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TOPIC: MAP Enhancer/modifier circuit

MAP Enhancer/modifier circuit 13 Feb 2020 12:31 #1

  • GregK
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For those of you who have seen me mention or advise including this mod on grooved vehicles that may not have seen gains to take more control of fuel delivery, you might've followed a link I included to an article explaining how to incorporate it.
Good news: the author of that article has joined the 21st century, started a YouTube Channel and is posting videos!

Dig into his channel - his aerodynamics mod videos are what I'm binging on since he popped up in my feed, but there is a TON of good stuff in there for us (like his EGR mod suggestions).

Here's the MAP:


In my case, I'm adding a wee tiny bit of voltage. You may need to subtract it, but this video shows how to do both. a good weapon to have in the arsenal you use to slay the dragon of big oil.
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MAP Enhancer/modifier circuit 19 Feb 2020 20:59 #2

  • GregK
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Here's an update on my implementation of this circuit:

Because I'm adding voltage (as most of us who live below ~3000' elevation above sea level probably will), I've had to add a resistor to the +5VDC leg of this circuit before it connects to the potentiometer. why? Well, when I tried to trim just that wee bit more lean, I'd get an engine code (I never bothered checking it but I'm sure it has something to do with the MAP sensor), and the EGR valve would slam wide open causing the engine to stall. as best I can reckon, I'm knocking the 5V down to around 1V, which is still plenty of offset to add to the MAP signal, and I may be using maybe 0.3V of that. I'm not especially savvy when it comes to electronics, but I can probably find the right things to measure and formulas to plug those numbers into to get the REAL answer.

It is possible to get VERY lean with this circuit, In other words. This may have (well, probably has) something to with the EFIE I have on my o2 sensor as well. I'm still tweaking, so mileage is off my benchmarks, but it looks like when I'm in the zone, I'm getting slightly better mileage than I do when it's summer, and that's including some warm-up time (yes, I know it's bad...) BUT I think it's a bit too lean, because the power feels to have dropped off, and that could be a danger. I can now idle smoothly below 500 rpm...somewhere between 450-475 as it appears on my tachometer, whereas before it was a rough, stumbly idle

This is weird to report: I may have taken things too far. now I need to back off some, and find the happy medium between drivability and efficiency.
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MAP Enhancer/modifier circuit 24 Feb 2020 06:16 #3

  • GregK
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Another update here, for those of you tinkering along on your own rides.
The best procedure I’ve come up with for avoiding engine codes is to check the voltage the computer sends from the MAP at KOEO, flip over to the output of the pot and adjust to that voltage, THEN start the engine, wait for hot idle/closed loop, then tweak.
For me, there is a sweet spot, where the engine is simply and ridiculously smooth. And it always has been what I thought was smooth, but this puts a fine polish on that.
I’m still working on the balance between MAP and EFIE. But, mileage seems to be on a not insignificant uptick.
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MAP Enhancer/modifier circuit 15 May 2021 10:56 #4

  • GregK
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If you've stumbled upon or otherwise found this thread, I just wanted to post a test procedure for you to be able to determine whether you need to use the pull-up or pull-down method from Julian Edgar's video...in the form of another video, lol.
Because while it's good to trust what you see online, you should also verify it: some MAP sensors increase their voltage output under vacuum (from what I understand) and others, decrease it.
what you want to do with the resistor is tune your MAP circuit so that it's reading correctly, at the end of the range it should be at when sitting at idle and/or at WOT. (I'm looking into seeing if this method can be applied to electronic throttle controls so that WOT is actually happening when the pedal is floored...it's the throttle position sensor, right?)



I don't have a brake bleeder pump, and luckily my MAP sensor marked which pins were what, so the only thing I had to do was backprobe the signal wire, attach a hose, and then suck the air out. the needle moved in the direction I expected it to, and after i put the resistor in-line, it was just a matter of tweaking the voltage to the end of the range it was supposed to be at.
I check it from time to time, between the MAP and EFIE - these adjusters do drift and vary with the weather/seasons, so it's important to recalibrate every so often to keep your fuel economy close to the best it can be.
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