Can you helpful people out there give me an idea of what readings you get on you oil pressure gauges. On my roadster it reads in kg/cm3. on start up from cold it reads about 5 then once up to running temperature reads as follows. At idle just below 2kg/cm3, between 2000/3000 rpm about 3kg/cm3 and at 3000+ rpm just below 4kg/cm3. Now I think this equates to about 25psi,45psi and 55psi respectively. Does this sound about right and how does it compare to what anyone else is reading.
Hi Phil,
This might help, mine read the same.
http://www.mx5oc.co.uk/forum/forums/p/3931/20196.aspx#20196
The oil pressure on my rebuilt engine has increased slightly as its run in when idling cold, it now sits at about 2 to 3, and sometimes gets nearer to 4.5 or 5 when cold driving. Apart from that its the same as in that other thread - hot idle about 1, hot driving anywhere between 2 to 4 dep. upon revs.
Seems about the same as mine then. They do seem to be rather RPM dependant. I did find this link that was quite interesting and seemed to confirm that the oil pressure readings do seem to vary quite a bit. http://www.miata.net/garage/opg_diagnostics/index.html
I think an old mechanical gauge would be the best way to go to get an accurate reading but as mine appears to be about normal I dont think I will bother.
Would have thought it was logical that the pressure will rise as the rpm increases. Nothing to do with the gauge.
On mine, hot pressure at idle is 1kg/cm2 and hot at 3000rpm is 3kg/cm2. I believe the engine has covered less than 75,000 miles. Oil is currently Comma Motorsport 5W50 but I got just about the same pressures with Mobil 1 0W40.
Just noticed today on my Eunos that braking heavily will drop the oil pressure gauge to just above 0! If you brake to a standstill, the needle will flick sharply then sit at about 1Kg/cm, rising to 2/2.5kg/com under acceleration.
I let the engine sit for a couple of hours when I got home & dipped the oil, but running mobil 1 it’s nigh impossible to see the level on the dipstick lol! Although quick application of kitchen roll to the dipstick suggests the oil levels fine.
Maybe a bad connection somewhere, check the connection at the oil filter end first. Very few things will cause total loss of oil pressure without a catastrophic engine failure—
I had a quick check of the connections, and although the gauge does still drop significantly under hard braking, it doesn’t go much below 0.5(ish) and flicks straight back as soon as the go pedal gets a blip.
Nothings come through the bonnet or the floor yet so I’ll give the rest of the connections a fiddle & a clean.
Cheers Geoff [H]
Oil pressure is generated by a pump running at engine speed - it isn’t load dependant, it’s just dependant on engine revs (increasing until the pressure relief valve is actuated) and temperature (cold oil is thicker - so higher pressures until I warms up a bit).
So braking shouldn’t make any difference. Unless you dip the clutch and let the revs fall to idle, in which case you’ll get idle levels of oil pressure, not zero.
If your pressure drops on braking it suggests oil surge in the sump or low oil level. Though the sump may have baffles to reduce this if the oil level is low the oil pick tube could be momentarily starved of oil under heavy braking and hence a lack of oil pressure.
Good point, I hadn’t thought of that.
The guy has checked his oil level and it seems OK
"I let the engine sit for a couple of hours when I got home & dipped the oil, but running mobil 1 it's nigh impossible to see the level on the dipstick lol! Although quick application of kitchen roll to the dipstick suggests the oil levels fine."
I've never pulled the sump on a '5 engine, but have done on loads of other engines, you nearly always find that the dipstick minimum level is well above the point where the oil pump pickup comes out of the fluid. If you think about it, full to min on a 1.6 '5 is 0.8lt, and there's 4&1/2 litres of the stuff circulating.---[IMG]http://i80.photobucket.com/albums/j183/gwa_2006/aussie-emoticon1-1.gif[/IMG]
Only a curiosity , but in old money , British cars anyway , the minimum to maximum was always 1 Quart .
Only a curiosity , but in old money , British cars anyway , the minimum to maximum was always 1 Quart .
Not far different then, 0.8l +1.4 ish pints—