What is your map reading at idle?...and what does your boost gauge read at idle?

...i seem to be SECS saying -6.5psi and gauge -10psi at idle does that look ok?

 

Phil, the map sensor signal will NOT be accurate at idle with a large
plenum chamber due to air pulse and volume sizes.

 

...does -10psi on the gauge sound correct then?..I want to make sure i have no vacuum leaks.

 

Phil,

The SECS moniotr and my boost gauge never show the same values. For instance today: 2 bar on my boost gauge. SECS monitor showed 26.4 psi.

 

The SECS monitor is NOT a super accuarte measurement device
as stated in the instructions.
It is a guide and more used for diagnosing faults.

It is ONLY as accurate as the map sensor which isnt that good by todays
hi tech standards.

Besides, put 2 gauges side by side and they will always read different
especially during transient changes.

 

Rich what does your gauge show at idle?

 

Simon, before the parnoia sets in pal. I was not having a dig. I think the SECS monitor is brilliant. Just telling Phil that its not only at idle that the gauge and monitor differ

 

CossieRich,

The monitor is far more able to read peaks than a gauge that has
been mechanically damped.

 

the proper way to do things is to use the 'pectel' datastream to see what the ecu is actually seeing

why not get the IAW monitor software from Stu?

 

Phil,

Gauge shows -0.6 bar. Not sure what SECS monitor shows. Will check tomorrow for you

 

...so thats -8psi Rich and mines -10psi so sounds ok to me

Cheers.

 

Phil,
Are you ignoring me



Rich,
Unless your inlet manifold is the same as Phils, any tests at idle
are irrelivant.

Nick,

The monitor reads RAW data from the map sensor and performs
limited digital filtering.

The ECU internal value is highly averaged.

In any case the ECU only has 8 bit resolution and the map sensor isnt
that accurate anyway otherwise it would cost much more to buy.

 

SECS

i know all of that, but worth pointing out to others

my point is, that if you are interested in knowing what pressure that the ecu is seeing, and hence using to look up stuff from the maps, is to use the datastream. although the monitor (for thicko phil ) tells you more or less what the ecu should see, there could be an internal fault (very unlikely) meaning that it doesn't

 

...i have a swedish plenum so that accounts for the -2psi defficit on my gauge to his

...i know it aint accurate the fooking boost gauge told me that i was merely asking as i want to make sure my vaccuum is correct.

 

foreigneRS,

 

Phil,
I wasnt joking.

Due to the large internal volume of the plenum you get pulses of air
at low rpm. This is measured by the map sensor and averaged.
The result is that the ACTUAL cyclinder charge pressure will be different
on that the map sensor as it reacts much quicker.

Mechanical gauges are dampened to stop them vibrating and jumping
around making them hard to read.

The ecu corrects this internally to provide a stable value for map value
selection but this will ALWAYS lead to an averaged value as you cannot
measure it accuartely no matter what ecu you have.

 

SECS

No i dont have the same inlet as Phil. What is likely to be more accurate then? My boost gauge showing 2 bar or the monitor showing 26.4 psi?

 

CossieRich,

The accuracy problem I menationed related to low rpm,

How did you measure that ?
Was it the peak reading ?

Unless you can hold the pressure steady accurate for a period of time
you cant compare the values as both will update at different rates.

Do both read zero when the engine is switched off ?

If so, then its ok as you are implying a larger difference.

(0 psi is not actually 0 volts on the map sensor wire)

 

Simon,

I reset the peak data on the monitor. I then floored it in 4th until the needle got to 2 bar on my boost guage. I then checked peak data under MAP and it said 26.4 psi

I know my gauge reads 0 when engine is off. Never actually looked at he monitor though. Will check it out

 

The peak data will ALWAYS read higher than a gauge.

For the reasons explained above.

I.E. The monitor reacts MUCH quicker that a gauge and records the peak.

Check the ZERO points are about the same.

Zero is actually 14.5 psi in absolute pressure terms
(The pressure of the atmosphere).

 

Simon, am i mis-understnading you completely The peak data was lower than my gauge reading, but you are saying that the peak data will always read higher than a gauge.

 

Rich,

I missread what you originally said

However, I have yet to find a mechanical gauge under Ł200 that
has any sort of reasonable accuracy.

However....

2 bar = (2 x 14.5 psi) = 29.0 psi
(rounded down to one decimal place before anyone moans)

29.0 - 26.4 = 2.6 psi

If you allow 1% for monitor accuaracy (0.9 psi for a 2 bar scale/3 bar map)
That means the gauge at best is 1% in-accurate.

(Assuming all is functioning correctly)

Also, dont forget,, the viewing angle of the gauge will affect how you
read the scale.

 

Simon,

thankyou for your replys mate

So are you saying that is ok then? Is a racetech gauge which is well under Ł200

 

i had a pectel monitor in my car the other day and it was reading 28psi at peak and secs was reading 23psi

 

so is a normal vacum i.e standard inlet-10-15 psi then

 

r5jame5

When comparing peak data....

Different update rates will yeald different results.

If you apply a static pressure for enough time they will equalise.

jaycos,

Generally, yes.

 

and wouldnt bigger cams create mor vacum at idle ?

 

it was held on full boost for quite a while and there was still 5 psi in between them i was sat watching both from the passenger seat they had plenty of time to equalise . not slating the product in any way because all the other functions are spot on except this one .

 

jaycos,

NO, generally bigger cams reduce idle vacuum due to overlap

 

r5jame5,

When ever you get 2 measuring devices side by side, tehre will ALWAYS
be a difference.

Which one is correct....


In my instruction manual, I do quote accuracy percentages.

I bet Pectel dont...

 

turned into a interesting thread this

 

my defi boost gauge is the same as the pectel monitor .

 

tis intersting this

 

Then your defi is wrong too

Seriously, said this before but the monitor was only ever meant to be a
guide and diagnostic tool and many things can affect accuracy.

If you wanted an officially calibrated accurate device then double
the price and people wouldnt buy them.

They do the job they were designed to do

 

not having a dig at you . just pointing out it does exactly what you say in the instructions still a really good product thats priced well

 

see my zeixtronic gauge reads -16.7 psi normal gauge -15psi my ecu data screen -8 psi so working on what si says about gauge accuracy is right beacause the load points on my ecu start at 0 kpa then the next is -8 (50 kpa) ,and its the second site thats adjusted for idle if i went purely by a gauge which you wouldnt id be mapping the first site at 0 kpa

 

just to add the zeixtronic has its own map sensor and is spot on past 0+ psi

 

r5jame5,

No problem, didnt think you were.