Fuel cut is dependant on atmospheric pressure. This could happen if you are at altitude. But much more likely to be your gauge.
Steve [Edited by StephenDone - 8/7/2002 12:41:25 PM] |
J
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Don't know, but MY99 AE801 peaked at 19.5 psi last night (the dawes needed turning down a bit :D ) Didn't fuel cut though ;)
Mines now running 17.5psi |
Fuel cut is 17.6 PSI held for about 4 seconds over this value.
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Thanks
I did think that it was about that but I was getting fuel cut at around 15.5psi. Maybe my boost gauge is wrong. J |
mine was cutting at 1,1 bar
how much is it in PSI? |
14.5 PSI is 1 bar.
Do gauges read absolute pressure or relative pressure? |
Absolute, don't they? Or relative, depending on what it's relative to :p
I think if you were up a very big hill, it would read under 0. So, if the car read +15psi over the local atmosphere (as it does measure locally), and the local atmosphere was 1psi under 'normal', then the gauge would read +14psi (with the car reading +15psi) as the gauge doesn't adjust. If that makes sense... I think that's how it would work anyway :) |
Boost gauges read relative pressure - if your engine is off, your gauge reads 0 doesn't it. That means 0 psi/bar above atmospheric pressure.
Manifold pressure sensors read absolute pressure, so with the engine off, they'd read around 14.5 PSI / 1 Bar. Steve |
Well I was thinking relative so fuel cut should always be at the same point on the gauge since it is compensated absolute = relative. However, I wondered since the gauges do not always show exactly zero - could be crap gauge or varying atmospheric pressure? Thinking about the construction I would think they are relative though?
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My boost gauge reads -12psi when the engine is off. It is a cheap one made by Mocal, should I take it back. Could it be why I get fuel cut at 15psi with my AE800 ecu? Perhaps it is mis-reading.
j |
Heh, Yeah i would take it back :)
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Well, that sorts the original problem out... but I still think that the gauge is absolute but the numbers are offset to read 0psi at 1 standard atmosphere.
Trying to explain more clearly, (assuming the gauge is accurate) the gauge will give a correct reading of conditions in the manifold if the local atmosphere is at 1 atmosphere pressure. However, if you were to take the car underwater into a big cave (!) and therefore increase the air pressure to say, 2 bar, the guage would read 1 bar at rest, not 0 (1 bar above what it's expecting local pressure to be). Driving about the cave...(!) if the car boosted to 1 bar - which it would read as 1 bar as it would be 1 bar above local atmosphere - the gauge would read 3 bar. If nothing else, I think I can spell gauge now! |
I'm may be reading less than you guy because the gauge are set up for 1 atmosphere (1015 mBar) and that here south of france we mostly have high pressure and you guy's in england have low pressure
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Well i've swapped the gauge and although it sits fractionally below zero with the engine off I am holding just over 16 psi with no cut-off. So that'll be 16.5psi in real terms.
I guess you get what you pay for. J |
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