ok fitted my new sec's monitor, and its readin 3psi less once on boost then 3 gauges i've got. and also stops readin over 27.5psi on monitor, 30 psi on other gauges, inc autometer, racetech and a mocal boost gauges.

it's a 3 bar map, on 3 bar map settings on monitor. its running off the same vacum pipe, and no boost leaks in pipe work.

gonna try a mates brand new 3 bar map.

anyone seen this b4?

 

Thought the 3bar read to 30-31psi ?

 

I dont think the SECS moniter will read over 28psi

 

3 bar is 2 bar boost i bar air pressue or summit aint it? so it wont read over 29psi, there was talk of a 5 bar map sensor a while ago wernt there?

 

well it bein a 3bar should be able to read to 31-2 psi,

but mines readin 2-3 psi out on vac and boost, so on gauges say 10, monitor is 7.5psi, and same alway upto 30.5 psi on gauges and 27.7psi on monitor, and over that dont read anymore.

just tested a brand new 3 bar map sensor, and doin ex same?

so most be ecu or monitor.

 

dodgy map sensor

dodgy wiring

dodgy SECS monitor

nothing wrong, you toher 3 gauges are misreading

take your pick...

 

aye it may be 3 bar but it aint 3 bar of boost it measures though, its 2 bar (29psi) of boost and 1 bar of air pressure iirc

 

what does it read with the vac pipe disconnected from it? (engine not running?)

i knwo you have an a/f ratio meter,,, is all fine? if so,, theres nothing too worry about

 

I thought 3 Bar map sensor, read something like -0.5bar to +2.5bar,

Or something like that??

Steve

 

3 bar is only a rough approximation of how much positive pressure it will read (with the first bar being atmospheric) it should read to just over 30psi as stated in this thread already.

Im sure SECS will have some useful comments on the subject as he knows far more about his monitor and cossie map sensors than anyone else on the planet does!

Pm him to make sure he notices this thread as the board moves so fast he might miss it other wise.

 

Hi Danny,
Just to clarify what has already been said, the 3 bar MAP sensor will only "see" boost pressure of up to "29.4psi", this is the nature of the sensor (it is called 3 bar, because it reads atmospheric pressure + 2 bar). This is why people harp on about fitting 5 bar map sensors when running big boost, because the ECU will only be told that the engine is running 29.4psi, even if it was seeing 35psi, because that is the limit ("end") of the sensor range... The way tuners get round this when running big boost and the 3 bar MAP sensors, is to extrapolate the afr curve and throw sufficient fuel in to suit the required boost.

Be aware that the SECS monitor is just telling you what the MAP sensor is seeing and it is not a boost gauge as such. Saying that, usually the MAP sensor is calibrated to "see" a max of a fraction over 30psi.

 

What does your SECS monitor say at the point where your guage says 20 psi BTW?

 

chip-3door,

any pressure off absolute is a positive pressure,, even space which is around 0.0000000000000000000000001 bar (1x10 (-25))

Mike Rainbird,
isnt it interpolate mike and it dont really know if you call you would call what they do that!

remember running boost over your map sensor isnt smart,,, it will fuel the same for 29psi the same it will for 36 psi

 

No interpolate is for in between values, extrapolate is for going off the end of a set of values.

So mike was 100% correct

 

well i never knew that

 

All ecu's interpolate all the time anyway, as the map only ever has a resolution of at most about 20*20, so its the only way it knows how much fuel to have at 23psi if you only have a value for 22 and 24 etc.

As you say though, thats a lot safer than having one value for 29+ and using it for everything.
But there is more to it than that, you can use TPS and RPM to effect it too of course, in which case the 29 at 7000rpm@100% throttle is only ever going to occur for a split second during spool up anyway, so you can live with that if you have a value suitable for the 32psi it ends up holding (just example figures)

 

i know what interpolate means,,, but never heard the term extrapolate

 

dont worry my boost gauge reads 22psi then backs down to around 16psi.

while my SECS monitor only reads a maximum of 16psi.

 

Just checking, but peeps have got it set to the correct MAP sensors they are using haven't they?

Gareth,
You can go beyond the end of the MAP sensor, providing you know how to EXTRAPOLATE. Probably wise if YOU don't, as you didn't even know the meaning of the word... .

 

yup, I think its more of a case of my gauge is a bit out. Doubt there's anything wrong with the readings from the SECS monitor.

 

thats bollox mike, all you do is write your fuel for your highest boost on the top line of your map, the driver is the only person who can stop damage by keeping an eye on the boost gauge!

i wont be going past the end of my map as i have a five bar and a t34

 

5 bar renders the whole debate a bit pointless, anyone still mapping off the end of a 3 bar when they can get a five bar so cheaply is just bodging IMHO (unless its in motorsport and only the 3 bar is homologated or some other compelling reason to use it)

 

chip-3door,
theres other reasons for using a three bar on a cossie ecu and not a five bar!

a cossie ecu is a 16 bit ecu so the data word legth is set, so your loosing resolution if using a five bar with 16 bit

 

That depends on what you set the max and min values that the ecu looks for though surely?

Ie if you limit the voltage range over which you spread the available map you can limit it to just the boost you need to look.

Not sure if you can do that easily on the standard ECU, but its certainly possible on programmable ones where you have user defined map points.

 

i think you still would loose res, as im sure the voltage feedback from the sensor would go striaght into anologue to digital converter! (well maybe some filters first

 

You only have what 20 map points in the ecu?
Im sure even the most antiquated A2D can cope with many times that resolution mate!

 

16 x 16,,, how big would your brakepoints be for a 38 psi car talking some serious interpolation then

 

Id sooner lose resolution lower down though than have only one point for 29-38 in such an example!


After all, who cares if you interpolate a few % out at 7psi boost on a 38psi car anyway?

Id set the points (if i had 16) at something like:
-15
-10
-5
0
+5
+10
+15
+18
+22
+26
+28
+30
+32
+34
+36
+38


Or something like that personally, as you are far more bothered about getting the fuelling/timing right at high boost than low boost surely?

 

i dont realy knwo how you would define the brack points on a cossie ecu anyhow

 

I dont know either mate, i know almost nothing about cossie ECu's specifically, ive never mapped one as its not just a "laptop and a lead" requirement for doing so.

Im sure one of the mappers can clarify if you can user define the breakpoints or not like you can on say a DTA setup??????

 

Been here, done this on teh mapping topic, but if someone wants to start a fresh one, im game

This ones too off topic to generate enough interest IMO.

 

ok lads, as i sed b4,

tried it on two 3 bar map sensors, so rules out the sensor bein faulty,

on my mappers pectel unit read same as my gauges (2 months ago)

i knew a 3 bar map only can read 2 bar boost, and 1 bar vac.


but the problem is why is the monitor readin 2-3psi out, on boost and vacum, but fine wen ign on, but engine not runnin.

i have pm'd simon, and he's gonna ring me tomorrow about this and my coil pack runnin problems.

 

The SECS moniters have a dampened boost reading so not as quick as a gauge thats wot ive been told

 

but i tested them with and with out engine runnin.

with ign on, a pressure gun connected to all my gauges and moniter, thats the real only way to test a boost gauge.

 

would it be possible that where the boost pressure is measured by the boost gauge could be less/more than where the ecu reads the boost pressure as a result of a bigger cooler etc etc , i.e pressure drop or summit, so in effect you could have 2 different boost pressures in the system because of pressure drop because of large intercooler or summit else youve plumbed in? just a thought mate

 

the monitor dosnt see boost at all it sees is an electrical signal which in map sensors case is between 0 and 5 volts 5 volts being full boost at sensor it does vary a bit sensor to sensor also resistance in car wiring can cause irratic readings but they are all tested in the same way and when they leave they are all the same but each installation is different and thats generally where anomilies occur .some cars it goes to 29. ## others it does not you are more than welcome to send it back and i will gladly check it on our tester and in a car to be doubly sure .

 

My SECS Gauage is more accurate in measuring boost than my boost gauage

 

is yours only fitted with a 2 bar sensor though, ie std or stg 1 chip..?

 

i don tknow, but is there an offset facility in the monitor , so that you can calibrate it to read exactly? when secs comes round im sure he will know

 

Re the resoloution, debate.
The a/d on a cossie ecu will not be 16 bits. At most 12, but could be either 8 or 10 bit.
With a 3 bar the resoloution with 8 bit is to 0.01bar ish, with a 5bar sensor 0.02bar ish.

Resoloution is not a problem really, as all in all there are many factors that determine fueling, error between 0.02 bar (max error will be +-0.01bar) will be very low.

Darren