MAP sensor waveform 5sfe. what it suppose to look like? digital or analogue MAP?

[bajachris88]

Hi, i'm fitting a digital air fuel controller, as some of you know.

At the moment, i'm doing some debuggin in regards to what makes my output signal from my controller different to the original map output signal, as the ecu does not like it.

I'm after anyones personal accounts inregards to what the signal's wave form should look like on an oscilloscope, between the maps output signal and ground.

My brother and i hooked up our oscilloscope to the output and ground with the map sensor's original signal, and with my controllers output signal.

We found both to be a sine wave form, both oscillating positive and negative at a high frequency, with frequency decreasing and amplitude increasing with throttle (ie: increase in load and decrease in vaccuum). the only difference was that the frequency of the controller's output was of a lower frequency, and we believe that was due to the controller having a max of 22Hz processing ability (which included it trying ot keep up with the signals wave form and opening up tabled stored values in its other IC's).

We believe that the controller can not keep up with the frequency of the map sensor, and hence it comes out at a lower frequency that the ecu doesn't like (and hence the engine light comes on and the car goes into a safe mode).

This sine wave form is typical (from my research) of that of a digital map sensor, mainly found on fords. My controller would work fine on an analogue map sensor with a voltage that just goes up and down according to throttle and does not oscillate.

What kind of wave forms do you get on your 5sfe map sensor? does anyone know conclusively if its meant to be digital or analogue? My controller is guaranteed to work on MAF, but says it also works on map. assuming it only works for analogue.

[oldcorollas]

digital as in has a DAC inside the MAP sensor???

i was unde rthe impression that the vast majority were analogue, with a DC output between 0 and 5V...

what voltage are you giving as Vc to the MAP sensor? AC?

[DrNick]

What year is your ST184? The ECU changed from series 1 to series 2 5SFE and the MAP sensor may be different.

[gixer]

I haven't tested the particular Toyota MAP sensor you talk about, but we have ALWAYS found the Ford ones to be square wave digital output. From memory about 110 hertz at idle, increasing with rpm.

There are alot of MAF's that are digital square wave as well. I'm thinking that that the contoller you have is designed to work on an Analog out put say 0-5v, wether this be a MAF or MAP sensor.

I recently fitted an Emange to an SR20 it's MAF was analog out put, easy to set fuel cut overide as we just clamped the voltage.

You will find with a frequency output that if you put a digital multimeter on it set to the Voltage scale that the voltage will stay around a certain value, switch to frequency(if your multimeter has it) and you will see the frequency change. If it has an analog output then obviously the reading will change on the multimeter set to volts.

Does it say in the instructions if it is designed to work with frequency outputs? I am thinking it's designed for MAP/MAF's with analog output.

[MWP]

Sounds like you guys are getting a little confused about the different types...

MAP (manifold are pressure) sensors are all analog, normally 0 to 5V.

AFM (air flow meter, also known as MAF) there are a few different types, some analog, some digital.

[oldcorollas]

just looked up a late model (97+) 3SFE and it gives voltages for a given pressure, not PWM/frequency.. fwiw...

[Gavatron]

Yeah, all Toyota MAP sensors are 0-5v analog. No frequency involved.

[gixer]

Sounds like you guys are getting a little confused about the different types...

MAP (manifold are pressure) sensors are all analog, normally 0 to 5V.

AFM (air flow meter, also known as MAF) there are a few different types, some analog, some digital.

INCORRECT.....Ford MAP's are digital out put in frequency! I KNOW THAT FOR A FACT!

and MAP stand for manifold absolute pressure

[MWP]

Thought we were talking about Toyotas here?

[oldcorollas]

page 222 here
http://www.scribd.com/doc/9571013/Toyota-5sfe-engine

apply vacuum to the MAP sensor, and compare against voltage drop.

[gixer]

Thought we were talking about Toyotas here?

ok sorry, I thought you meant ALL MAP's, as I gathered you read my post.

[gixer]

page 222 here
http://www.scribd.com/doc/9571013/Toyota-5sfe-engine

apply vacuum to the MAP sensor, and compare against voltage drop.

or just rev the engine, opening the throttle large amounts and check the voltage

that's if he doesn't have a vacuum pump......maybe he does

[oldcorollas]

sorry.. added image from the 5SFE manual i linked was a bti slow.. had to resize for attachment
plus it has +5V in and ground, and a signal wire.. and thats all.. just like all other 3 wire violtage based MAP sensors??

i'm still surious as to why it had an AC output... what input voltage did he feed it for Vc?

[oldcorollas]

fuggit.. does this help maybe we can stop talking abotu digital MAP sensors

[oldcorollas]

My brother and i hooked up our oscilloscope to the output and ground with the map sensor's original signal, and with my controllers output signal.

We found both to be a sine wave form, both oscillating positive and negative at a high frequency, with frequency decreasing and amplitude increasing with throttle (ie: increase in load and decrease in vaccuum). the only difference was that the frequency of the controller's output was of a lower frequency, and we believe that was due to the controller having a max of 22Hz processing ability (which included it trying ot keep up with the signals wave form and opening up tabled stored values in its other IC's).

was this with engine running?
is the oscillation you are seeing above and below zero volts? (ie AC signal)
or, is it oscillation from noise from the alternator?

what were you using to power the MAP sensor? from the ECU's 5V Vc? or from the digital controller thing?

what is the output of the MAP sensor on the scope if you hook it up to a stable 5V DC input, and apply vacuum to it?