How to read intake manifold and oil pressure on defi guages??

[Zoomprotege]

Hey guys,

 

Itchy hands again and installed oil temp, oil pressure and intake manifold defi guages on my IS200 today. Thought intake manifold is essentially a vacuum guage, but the reading is so different. Any idea how to read it?

 

What's the ideal oil pressure on my ride when idle and when revving it?

 

Thanks for your help.

[Elfenstar]

The readings for your manifold gauge should be the same as your vacuum gauge as they record the same thing. Its good for controlling your foot to get good FC (higher vacuum is better).

 

As for oil pressure. The general guide for a target is 10psi increase for every 1000rpm increase. When the pressure stops increasing although the rpm does it means that although the engine speed is increasing, the flow of oil is the same (There is a fixed maximum pressure the oil pump can maintain).

 

What is ideal is that as long as the engine speed is increasing the oil flow should be increasing.

[Zoomprotege]

Problem with the intake manifold pressure guage is that it's reading in x100 kPsa. How do I translate that to inch per mercury? It seems to fluatuate often when I step on the pedal.

 

This is the range according to Defi website.

Intake Manifold -100kPa ~ +20kPa

[Dwoon]

1Kpa = 0.01bar

20 Kpa =0.2 bar.

 

For your request.

 

1Kpa = 0.2953 inches of mercury.

[Elfenstar]

Considering your needs, the actual figures don't need to mean anything to you. Just know that the higher the vacuum, the better the FC. And yes it is supposed to fluctuate in those circumstances.

[Dwoon]

Errmm... can NA cars actually run into the positive pressure range??? By a wee bit?

 

Wonder why they have a positive range of 0.2 bar for?

[Yeobh]

See attached photo- this is a professional vaccum gauge used by mech for troubleshooting. The info on the gauge face will be of great help to you.

[Elfenstar]

if the opening for the intake that leads to the filter is at the correct location (be it a CAI or even the factory snorkel), at faster speeds positive pressure can be created.

 

Vehicle aerodynamics is something i only know the basics about, but i know if the opening needs to be situated at a high pressure area.

Edited May 29, 2007 by Elfenstar

[Dwoon]

So if my idling, the manifold pressure is -0.5 to -0.6 bar (~ -375 to -450 mm Hg). I noticed that the gauge indicates a red region of "late ign timing"...... errmmm is this the case if it is during idling???

[Yeobh]

See attached info, they are great guides for troubleshooting. I have forgetten most if not all the needle dislay indications - last use this type of gauge more than 25yrs ago.

[Yc86]

I think what TS means is that he's not used to the units used on the Defi gauges?

 

Defi reads in Pascals(?) while the conventional vac gauge reads in inches mercury (inHG)

[Zoomprotege]

 

Ok, managed to get a pic of the defi guage. How do you decipher what you've shown me into this guage?

 

Thanks.

[Zoomprotege]

Managed to find one with PSI reading. Side by side comparison... can anyone help me to determine the healthy range and trouble-shoot problem range?

 

[Ronnchee]

Got pictures to show ?? must be very chio nah

[Elfenstar]

dwoon already put the conversion figure up for you. just do some math

[Yeobh]

Never will a NA engine " breathing" goes above atmospheric pressure. For carb NA engines the highest possible vacuum reading generated by the car venturi is = 27mm of hg 0r 685mm of hg.

The 0.2 bar is for measuring TC engines, when the exhuast is hot enough to spin the turbo exhaust impeller to a very high rpm ( 10,000 or more) thereby creating a + pressure in the intake manifold.

[Yeobh]

Using highest possible vaccuum is 27inch of HG or 685mm of HG.

[Zoomprotege]

Thanks guys!!!!