The boost sensor can measure vacuum too. it will read from -14psi to around +23psi

 

good luck finding a step-up resistor :P i kid..

depending on sensor power requirements you could use simple resistors to achieve 5V depending on how stable your 12V supply is. i think realistically a voltage regulator is gonna be easiest. Google data sheets or diagrams for LM317(iirc off the top of my head this is a regulator and VERY easy to setup)

if you guys decide you are REALLY serious about making this work, i can draw up what you need and even break it down barney style for ya for your 5V power source. Maybe even something for your units that dont have a 0-5V output. lemme think about that one for a bit

 

**** that reminds me of another gauge, would it be bad to measure fuel pressure off of the same "T" that feeds the nitrous?

 

I am serious and Barney style works for me

 

I'll cancel my beach excursion with a delicious European fashion model and work on it this weekend.

Sorry, it's a "pull-up" resistor as in the "circuit diagram" on this pdf:

http://www.aemelectronics.com/files/info/30-2011_1.pdf

I want to make a step-by-step example of taking some random resistive temp sensor, determining the value of "R pullup", calibrating it, and getting the calibration into the Goodbox. (One has mechanical-types and electrical-types. What's trivial for one is rocket science to the other and vice-versa.)

Yes I think one could also use the 14.x or so car voltage to drive it, but that's not always stable. At the current required, a 12V-5V converter should be cheap and give better results.

To summarize the options in one place:

(a) If one has a gauge that already has a 0-5V (often called datalogging) output and wants to keep that gauge, getting the signal into the goodbox is trivial - you only have to enter the calibration formula.

(b) If one has a standard gauge without such an output and wants to keep that gauge, and additionally, in the range of operation of that gauge, the wire-from-the-sensor voltage falls in the 0-5V range, it's a variation on the case above.

(c) If one wants to get a signal from a normal (resistive) sensor into the Goodbox without any additional gauge, then you have to get a source of power and add an appropriate resistor in parallel with the sensor to get a signal that falls into the 0-5V range.

(d) If you want to measure pressure using the goodbox without any additional gauge one has the option of buying a "special" sender that has a built-in 0-5V output; it will still require its own power though.

 

Uh, I hope you don't mean t-ing the fuel line into the nitrous bottle .

Since there are only the two inputs, getting more signals in would require a separate switch to get them into those inputs. Of course one could do that, but each input can take only one calibration curve. Switching between oil pressure and temperature for the same analogue input wouldn't make sense because their calibrations are going to be very different. However, and I'm tempted to do this, if one shared the same type, as in exactly the same type of sensor on one input, that's very doable. For example, switching between a water temp and an oil temp.

If you had exactly the same sensor for both nitrous and fuel, that could be switched, but (always a but ...), fuel is 0-70psi and nitrous is 0-1000 psi. To get the same calibration, you'd have to use identical sensors. Measuring 50 psi with a 0-1000 psi sender is not going to be very accurate.

(Too bad OBD-II doesn't include a requirement requiring inclusion of nitrous pressure information.)

 

It's cool that the supplied gauge is PSIa which allows this. Physically speaking, there is no such thing as vacuum, only the absence of pressure. I will change that calibration to run from 0 to 37 psi (or 0 to 75 inHg in airplane units), assuming that's possible. That way, it measures manifold pressure, not what's called manifold vacuum.

For the street, I find oil pressure to be most useful in telling me if the engine has warmed up - it's a more sensitive indicator really than water/oil temp.

 

Being silly, if you leave it disconnected you have a barometer/altimeter... <grin>.
(http://wiki.xtronics.com/index.php/P...o_Air_pressure)

Or, attach it to a pitot tube, and make an airspeed indicator.........

 

"Why is this?" he asked, hoping to learn something.

 

no, no, no. I meant installing the a fuel pressure sensor in the same T in the factory fuel line that supplies the nitrous system fuel.

 

this thread needs a good bump. No install pics yet? Mine should be installed on Monday

 

my install pics are on the last page..

 

car gets dropped off at the body shop monday. wont get this installed unit late this week possibly early next week

 

Was going to do it yesterday, but the external temp gauge on my truck was displaying 111 degF and I just couldn't get motivated enough to deal with that

 

highflight/9krpm: i havent forgotten this yet... i am thinking on it. right now my head is wrapped around OpAmps for current to voltage conversion. i'll get back when i have a better mindset on it

 

No Problem; I think I've got a $1.59 solution - maybe $5 with box, resistor, and connectors.

http://www.radioshack.com/product/in...99#tabsetBasic

 

i realize its only a buck and a half, but thats ridiculous. shouldnt cost more than 50 cents, typical rat shak. i would still use the LM317 personally, but thats because i like its thermal properties and i have a few of them laying around... plus the fact that i mentioned it already

 

mine came in Friday... Not sure when I'll get to installing it but I realized I have a real problem.

I already have an analog boost gauge, along with oil pressure, and oil temp.

So lets say I move my boost to the Goodbox... WTF am I going to put in my RB ashtray mount where my current boost gauge is?

For that matter, WTF am I going to put my goodbox? I was thinking glove box, but I like the idea of it being accessible. Also considering center console... hmm...

 

All good reasons. The 7805 runs hot at the full output of 500 mA, but the sensors take more like 10 mA so it shouldn't be a problem. Also, there's a ratshack on every corner in the USA and if you can get past the cell phone salesman to the tiny dark corner where they have the few remaining component parts for sale, it's generally in stock.

 

You could fill the holes with small cans of Red Bull.

Here's a little sweet surprise I was waiting to reveal until later. With much hacking along the hidden sides of the coin holder, the Goodbox fits snugly but neatly in the coin tray. You can open the tray to see and manipulate the buttons, and close it to hide it entirely. The supplied harness is long enough to reach, though you have to extend the power lines a little to reach the cigar lighter wires in the center console. I'll put up pics tomorrow sometime, since several people are in the install phase.

 

^................ I was wondering if it would fit over there and if the cables would be long enough without having to lengthen them.
Good.......can't wait to see the pics.

 

^.............this is why I'm not jumping in on this.
While I'm still NA, I do have another OBDII setup + oil as well.

My gauges aren't in the ashtray, but I'm still not giving them up! If I did, I would certainly go this route.


Wow........ShellDude, you got some figuring out to do!
Let you know if I come up with a better idea....going to be tough.

 

Sweet!

 

well poo, i thought i was the only person to think of the coin tray

 

guess i should have shared this here awhile ago. no wire extensions necessary:

https://www.rx8club.com/showpost.php...&postcount=230