as the MAP sensor obviously reads the pressure in the vacuum (and i think the standard ones go to about 1bar? ) would i be able to tap a feed off the signal to get a voltage which i could then translate into a 'boost' reading?

if so, does anyone have a chart of the various voltage readings according to boost pressure?!

thanks,

p.s. it seems like a reasonable idea to me so don't laugh/take the piss

 

Hofajoab, no reason why you cant,, this is how the secs monitor works

 

yes you could, but you will need to be careful not to load the signal, or introduce electical interference into what is a sensitive signal as far as the ECU and fuel map is concerned

 

LOL - Gareth sitting at home with no work to do this afternoon LOL ... beat me
to it

 

well i was just going to use my multimeter to test it until i get a boost guage. I presume the multimeter wont load it too much? and it should be pretty accurate being a Fluke

 

omg do you know jim galbally by anychance


why not get one of them really really rare things that somne cars have fitted to em



what they called






thats it a
















boost gauge , tim to a 1 bar boost gauge that would be perfect and no need for 2 years or enginering to make one, pop in to halfords with 20 quid and buy one

infact when i get my new one ya can have mine free but mines a 2bar one


why do people make things hard for em

 

Typical Readings:
Sensor output voltage range is 0.5 to 4.5 volts.

Output voltages between 0.5 and 1.5 volts indicate a high vacuum (low pressure) situation, such as idle or deceleration.

Output voltages between 1.5 and 3.0 volts indicate a medium level of vacuum (pressure) such as a cruise or slight acceleration condition.

Output voltages between 3.0 and 4.5 volts indicate a low vacuum (high pressure) situation such as hard acceleration or a mechanical failure.

Any reading of 0 volts or over 4.5 volts indicates a problem.




Found that but it doesn't exactly give me a precise reading

 

http://www.emergent.com.au/200sx/boost_gauge_1.html

Voltage readings

how to make a boost guage too! i've already got a schematic on how to make an Air/Fuel meter as well but Maplin don't sell LM3914's RS, or Farnell me thinks

 

multimeter will do lovely as they have nice high imput impedance

 

Marelli MAP sensor voltage characteristic:
APS02 (standard 2-bar)

0.25V @ 17KPa - 4.75V @ 216KPa

and linear response of 22.61mV per KPa between these two points

 

flukes - pah - they would be high enough input impedance as to not affect the circuit, but you really want an avo , proper moving coil meter - have you ever been chasing voltages that dont actually exist with a fluke.... like in you house, neutral to earth - 60 volts says fluke - bollox i say, mr avo confirms - they do tell big fibs sometimes that u need to be aware of.

 

cheers RIch again for your info

i do have a big old Avo meter, think it's an RF meter of some sort, i might dig it out

 

many apprentice make that mistake,,, thats why i use a voltage indecator most of them time when fault finding

 

well i tried it.. i looked up Haynes and i gather the Brown wire is the one i want but i get a constant 0volts on it, so i tried the other ones, one was a constant 5volts which would be the feed and the other was a constant 2.5volts... i couldn't get a reading!

fooked MAP sensor?

 

was the engine running?
if the engine is not running, you will get a nominal 2.5Vdc signal which corresponds to atmospheric pressure - ie no boost pressure and no vacuum - ~1bar absolute.

 

yeah i checked that with the ignition on and thought, cool, 0psi.. so i went a drive and it didn't change at all

 

wait wait wait! can we all hold on for a second...

hoofajab, you have a 1bar map sensor...

this reads upto 1bar ABSOLUTE (which is nornmal atmospheric pressure)

this CANNOT read boost

a 2bar MAP sensor reads upto 2bar absolute (1bar boost)

you dont have one of those...

so sorry, you can't do it ai'm afraid.

also i beleive the standard map sensor on the DOHC is frequency based not voltage based, so you'd need an oscilloscope to read it anyway!

 

nice!.. ah well that's that idea oot the window! unless i use a 2bar MAP sensor and run it seperately just for the meter, but then i may as well buy a proper guage

It was worth a try anyway!

cheers folks!

 

Ah!!!! LOL - I missed the point completely!!
Made the rash assumption we were on a cossie here.. then after Jims post I actually read ya sig properly.. DOH!
Yeah, frequency output MAP sensor will read 2.5V nominal on a DC meter..
Well spotted Jim!!!

 

yep well pointed out jim

you can get a freqauncy to voltage chip though,,, and start all over again

 

dont worry guys, i woulda made the same assumption if it wasnt that ive been following hofajoab's other posts

 

ps what method are you using to put in extra fuel when on boost?

as the TT DCU uses a seperate map sensor...

so does an MF2 (kinda)

just wondering how you're fueling it, as im thinking your either running a pressure switch bodgeup thing (which i know will work by the way not knocking it) or youre not doing anything at all... lol

 

aye sorry about that, i don't have a cossy, a mere 2.0DOHC effort and my pikey sig doesn't exactly show it too well eitehr.

I'm using a 'bodged' up 5th injector with a pressure switch. i've come to realise it's a sheer sh*tbox, but it's my sh*tbox lmao!