Oil level and pressures

[james fillingham]

A regular topic I know, but a couple of questions:

 

- I regularly check my oil levels, but when warm the oil is so thin and so clean that it is almost impossible to assess where the level is on the dipstick. There's definitely some there (you can see it on the cloth), but as to where it is, who knows. Is this a frequent issue and if so is there some easy test? Does it just mean that my engine runs very smoothly and clean? There is nothing on the garage floor or around the engine bay.

 

- The oil pressure gauge tends to start at just over the mid mark (4 I think?) and increased when I topped up with a oil a month or so back. However, it drops off quickly as a running temperature is reached, especially when I have a bit of a thrash. Dropping off can be translated as reaching 2 or less and sometimes verging towards the redline when at idle. When revved I'm back at 3-4. My gut instinct (and a trawl through the archives) tells me this is OK, but it does worry me when sitting in a traffic queue wondering if the engine is about to seize. Any thoughts?

 

The car is a 1600SS and by virtue of upgratitis I am planning on getting an Appoll/Anti-Cav fitted at the next service. I hope that this might go some way to adding an extra comfort zone or margin for error around these matters. Also, I do a little bit of trackday work, but don't want to splash out for a dry sump.

 

All ideas gratefully received by an owner of a mere 6 months.

 

James

[PeterS]

Also have the same characteristics on oil pressure loss, even though we've fitted an anti-cav tank.

The anti-cav gets rid of the air, but isn't likely to raise the pressure. I seem to remember someone on one of these threads thought that it caused an apparent drop. So don't expect that to solve your problem as stated. It might however save the cavitation problem, depending on how you drive and whether you are doing track time.

I'm sure someone else will give advice about dry sumping, and whether it helps your problem.

[Graham King]

James, I too have suffered the same problem, I have owned a 1.8K Roadsport for all of 6 weeks now, oil pressures very similar on both idle and running when warm (2 bar idle 4-4.5 bar when running). When checking the level I have found it impossible to read the dipstick accurately. The only way I have found is to see if oil is in the notch in the dipstick showing the correct level, I have found this easier to check out of direct sunlight (eg in the garage).

 

If anyone else has any better suggestions I too would be interested, but having read previous postings on oil pressure I think yours are fine.

 

Graham.

 

R7 GPK

[Simos]

Your pressures sound fine.

 

Oil pressure is function of pump pressure, oil viscosity at whatever temp and flow resistance in the engine.

 

Flow resistance is going to be fixed unless you drill holes and change piping.

 

Pump pressure will remain unchanged at x revs unless you change it

 

Oil viscosity will change with temp and type. E.g it is more viscous when cold so pressures will be higher at x revs than when it is hot. If you changed from 0w/40 to 15w/50 then oil pressure will rise across the rev range, though this will probably be a bad thing for your hydraulic tappets.

 

Adding apollo won't change the pressure unless it changes the piping significantly or you change your pump. For a dry sump, the latter is a given because you need a scavenge side as well as a delivery side and these pumps are often "stronger" resulting in higher pressure. However it is the pump change and not the dry sumping per se which makes the change.

 

Overall the rule of thumb is 2bar at tickover and 5bar at full bore is fine, outside this range you should seek advice (or already know).

 

If the engine is extra hot (in traffic) and revs are low then it may dip below 2, however if it instantly jumps when you blip the throttle this is ok. You can always adjust the idle screw to idle at 1,000+ if it really worries you which should keep it up (the revs that is smile.gif)

 

The engine is doing little work in this scenario so does not need loads of oil. On a blat it is a differnet story.

 

Cheers, Simon.

[John Vine]

Adding apollo won't change the pressure...

 

Well, it won't increase it, but it sure will reduce it (by about 0.5 bar) because of the air-bleed to the cam cover.

 

JV