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I recently purhased an Autometer A/F ratio gauge (the one with the LED's). At the present calibration the gauge reads from about 0-1V, which displays the Red / Yellow / Green LED's at the proper voltage levels.

Now for the plan - I am going to modify the gauge to be my boost gauge, custom calibrated so that each LED would represent 1 PSI or less. I have all of the LED's removed from the gauge now, and plan on making it green, yellow, than red (to represent high boost).

My question, for those of you who know - what are the limits / specifications on the stock Honda MAP sensor which our car uses? I've heard many different things, such as its a 1 bar sensor (which should in theory be good to 14.5 PSI), but that its only good up to about 12 PSI. Does anyone have any data that they've logged as to what their maximum sensor voltage was and what the boost was at that period of time?

 
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is this something that u want to do to be unique, otherwise why dont u just get a missing link and not have to worry about it

 
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At this point, unless I can get my hands on a stock MAP sensor to play with, I can't calibrate the settings properly (I need the voltage where the sensor tops out). I am doing this because I think it would be a cool looking boost gauge. There are no other LED gauges out there right now that look as cool as the Autometer gauges. Heck, as far as I know, there are no LED boost gauges at all. There might be, but they surely don't look as good.

The cool thing about the design of the Autometer gauge is that with some modification it can run in "bar graph" mode, ie instead of seeing 1 LED move around (as the normal operation shows), it can be configured to show a bar graph (ie, all the lights below measured value will be lit as well). And, by changing the color of the LED's, and calibrated voltage, it can be essentially used to measure any signal in the car (boost, temperature, oil pressure, etc).

Don't get me wrong, the dial gauges are cool. But I want a clean, digital look....

 
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ill admit it will be cool

 
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I can log it with the emanange and give you a graph. But until then, these are the numbers I remember:
-10psi = 1.0V
0 psi = 2.89V
4.5psi = 3.5V
8psi = 4.5V

I'd have to go back and check for more accurate numbers.

 
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Boosted, thanks for confirming my thoughts.....If you could post a graph from the emanage, I'd be more than grateful!! I am probably going to try and calibrate the gauge for 2.9 volts (0 PSI) to 4.9 volts (14.5 PSI). I'd never hopefully reach 14.5 PSI, but just as a safety to see if boost creep exists. This *should* in theory give me .725 PSI per LED segment (as their are 20 segments total in the Autometer gauge).

As far as my suspicions go about the missing link -

If you read over on the honda-tech forums, when people implement the AFC hack, most of them seem to have a smoother transition from NA to boost....I'm betting the reasoning behind that is because if you use the missing link, your TPS will show that the throttle is open, but the MAP sensor will show 0 PSI in the manifold, meaning that there is no air entering the engine! The ECU compensates by leaning out the fuel ratio. In the cases where people have the missing link installed (and don't have any transitioning problems), the only thing I can think of is that their fuel management compensates for the lack of fuel being injected by the ECU.....Don't quote me on this, I am just hypothesizing here, heh.....

 
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I will get you a graph of Boost vs MAP signal, but you are going to have to wait till this weekend. My laptop is in CT and I'm in NJ.

 
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No prob - thanks man!

 
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Just some more random values: These were mixed up and I put them in some order, so they aren't exactly correct because some were taken while going into vacuum, and other going out of vacuum. The ECU and E-manage don't sample at the same speed. Either way, when I go back, I'll get you some from a run straight from vacuum to boost so it is more linear. But in the meantime, you can play with these.

PSI Voltage

-12.3 = 0.46
-12 = 0.5
-10.8 = 0.54
-10.7 = 0.68
-10.2 = 0.99
-7.9 = 1.66
-6.4 = 1.52
-6.3 = 1.55
-6.2 = 1.53
-6.1 = 1.57
-6 = 1.61
-5.9 = 1.68
-4.8 = 1.74
-4.1 = 1.85
-3 = 2.01
-1.3 = 2.26
-0.3 = 2.58
0 = 2.85
0.1 = 2.75
0.4 = 2.86
0.6 = 2.91
0.8 = 2.95
1.1 = 3.01
1.3 = 3.03
1.4 = 3.08
1.6 = 3.12
1.8 = 3.13
1.9 = 3.18
2 = 3.21
2.2 = 3.23
2.3 = 3.26
2.5 = 3.3
2.6 = 3.33
2.7 = 3.33
2.8 = 3.35
2.9 = 3.39
3 = 3.38
3.1 = 3.43
3.2 = 3.46

 
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I'm bringing this back up again for a reason. I dunno why this just popped in my head. Unless you are using a voltage clamp from the Emanage or something, this won't work for you. (BTW, the Boost Limiter Cut setting on the Emanage works perfectly at hiding the voltage. I have mine set at 2.95V and it never goes over 2.94V). If you are using the missing link or some type of bleeder valve, than you are hiding boost altogether from the MAP, and it will never read those voltages. So if you want to do this, you need to use a voltage clamp, and get the real signal from the map before the Emanage, or whatever other unit does the trick. But in the end, the MAP needs to see the actual pressure.

Eitherway... even though I don't get any CEL from using the stock sensor without hiding boost, the ECU is worthless in the range of 3.0V and 3.2V, after that, the ECU can adjust, but in that range, it causes the injectors to screw up. That's why now I have it clamped not to go above 2.95.

 
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Yeah, I was planning on using the emanage to hide the voltage. That way it will transition to boost smoother too than using the missing link, which just cuts it off at 2.94 volts, which is essentially 0 PSI.....That shouldn't be a problem.

I actually have gotten my gauge somewhat modified already, the bar graph function works, as well as my new LED's. The only PITA is going to be hooking up a voltage regulator - I need a regulated 5 volts to the autometer for it to calibrate properly.....that's going to be hard!