Whats the PSI of Atmosphere?

[Martiny]

Hi All

I am trying to determine the fuel cut point/s of my 92 FD. I have found a set of readings, but they are for Absolute Manifold Pressure, which is the boost gauge reading PLUS the atmosphere.

So, whats the Atmosphere PSi in London please, anyone?

[nikp]

uh? Atmospheric pressure at sea level shoulds, on average be 0.

However, that\'s not strictly true - on a boost gauge it will be zero. But on average, it is actually 1bar (Or one thousand milibars!) This varies slightly due to weathewr conditions, etc - but use 1000 (i.e. 1bar - 14.7PSI) as the figure to go from.

[noyzboy]

14.7 PSI is standard atmospheric pressure at seal level
If your gauge is reading absolute pressure, then it should show 14.7 PSI with the engine turned off.
If it\'s reading Zero with the engine turned off then the gauge is reading " Gauge pressure"  which is more common in industry. The tyre pump gauge at your local garage reads "Gauge pressure", which is the pressure above atmospheric.

Atmospheric  pressure decreases by approximately 1.0 psi for every 2,343 feet. For the London Area 14.7 PSI is good enough

[nikp]

Well,  how abvout that for a more comprehensive answer!

[Martiny]

uh? Atmospheric pressure at sea level shoulds, on average be 0.

Err if it was really zero your body would explode !

However, that\'s not strictly true - on a boost gauge it will be zero. But on average, it is actually 1bar (Or one thousand milibars!) This varies slightly due to weather conditions, etc - but use 1000 (i.e. 1bar - 14.7PSI) as the figure to go from.

So, our boost gauges are calibrated to show zero for the Atmoshperic pressure, yes?

Ok, I found a website that says 1 Bar, or 1 kg/cm2, which equals 14.2 PSI.

[nikp]

Well, I meant that most people when talking about air pressure refer to it as zero. Perhaps i wasn\'t too precise when explaining it...but i did clarify my meaning in the next paragraph! :p

[nikp]

...plus, we\'d only explode if we had normal air in our lungs - at a pressure above that of the air pressure outside our lungs! So we would necassarily explode! So ner! :p

[Martiny]

...plus, we\'d only explode if we had normal air in our lungs - at a pressure above that of the air pressure outside our lungs! So we would necassarily explode! So ner! :p

Not so!!!!

Whats the pressure in your veins?

NER! :flamed

[Martiny]

...plus, we\'d only explode if we had normal air in our lungs - at a pressure above that of the air pressure outside our lungs! So we would necassarily explode! So ner! :p

Wait , we agree because you said  "So we would necassarily explode!"

 :p  :p  :p  :p  :rollin

[nikp]

Poo to you! Not fair! I blame it on monday morning syndrome!  

[Martiny]

Lol   !!!!

[Martiny]

After all that I discovered that the website did have them in PSI!

What you see here is RPM then Absolute Pressure, then Boost Pressure in the 3rd Column. These are supposed to be the point at which the standard FD ECU will cut fuel.

1000    26.5                    11.8
1500    26.5                    11.8
2000    26.5                    11.8
2500    26.5                    11.8
3000    26.9                    12.2
3500    27.1                    12.4
4000    27.5                    12.8
4500    28.0                    13.3
5000    26.9                    12.2
5500    26.0                    11.3
6000    25.8                    11.1
6500    25.4                    10.7
7000    25.4                    10.7

I am not sure I believe them, though, because my car is spiking much higher than these readings and I havent hit Fuel cut yet. Meantime I am looking for and analogue Air Fuel meter to check my 02 readings before I do anymore testing to try and solve my boost problem.

[Trevrx]

My car was hitting 1.1 bar spike after the decat, still no fuel cut!  Stock ECU - no sign of a fuel cut defender.
Are those figures for all Rx7\'s or the USA version?  You\'re not planning to check your air fuel ratio with a narrow band A/F guage are you?

So what\'s your boost problem?

[Jono FD3]

I agree with those figures being suspect, my FD is running stock gear and it\'s hitting 1 bar with no fuel cut! wether it\'s different between GB, Jap & USA cars I don\'t know??
Jono

[Martiny]

Yes, my figures are from a US website, so our cars might be different.