18 replies to this topic

[Steve220]

A few bits wrong on that i think, Chris. I've built several MPi engines, and worked with them exclusively now (only A+ i've ever owned is the 998cc in the van lol). Pressure at idle i've never seen below 1 bar - only time it's been close (20psi) is running 20w50 with the oil temp being c120C and worn bearings (race engine on a standard pump). I've logged Felix's engine on the standard pump when i first built it and it was 110psi cold at idle, dropping to around 40psi when at operating temp. Gav Wilkinson, who has a standard MPi block but turbo'd, also sees above 100psi from cold. They really are a perculiar engine!

OK cheers for that Steve. As I did mention, I haven't worked on them, however that figure I have seen in another publication.

I gotta say though, 100 PSI ? That's pretty high !!!

Its ridiculously high! I'm running oil jets and oil fed drop idler and it's still high 🤣

[goudoogje]

can oil pressure be to high?

[Steve220]

can oil pressure be to high?

 

Very much so! It creates an immense amount of drag onto the camshaft, and therefore the engines, so you're losing power. 

[Spider]

 

can oil pressure be to high?

 

Very much so! It creates an immense amount of drag onto the camshaft, and therefore the engines, so you're losing power. 

 

 

As Steve has said and it also heats the oil up a lot.

I made a detailed post some time ago if you'd like to do a search, suffice to say, getting oil where it needs to be is more to do with where the oil is 'injected' in to the various parts than the pressure itself. As one example, a typical A Series Engine developing around 50 HP will have spot pressures in the engine bearings of around 5000 PSI. If we were just relying on Oil Pressure to lubricate these parts, with Oil being fed in at say 100 PSI, which would win out ?

Another factor here to keep in mind is that most Spin On type Oil Filters are only rated to 100 PSI, this is why the Autos retained a Cartridge type Filter.