Paradoxial drop in oil pressure with throttle... ???

[cambelt]

Struth 3 thou is far too large .Who suggested those clearences?
1 thou big ends and 1.5 thou mains MAX .
Dave

[ed]

youre dreaming dave. seriously. 9500rpm is a completely different engine to whatever it is your thinking about. different bearing tolerances, different oil dynamics, different loads, different temps...

[rms]

Struth 3 thou is far too large .Who suggested those clearences?
1 thou big ends and 1.5 thou mains MAX .
Dave

Dave,
I would suggest that you have had limited experience with race engines based on a production block.

A Cosworth BD series would be lucky to survive a single lap at your suggested clearances !

I have found that a 1UZ with std clearances will not survive at 8000 rpm, let alone 9000/10000 rpm.

So far as I know, Ed and myself are the only private 1uz's with max power above 8000 rpm and turning in excess of 9000 rpm. Both engines N/A and no nitrous, both well in excess of 500bhp at the flywheel.

[jeffro ra28]

I stress that 9000/10000rpm is also alot to ask from a standard oil pump

I spose it depends on how good the stock oil pump is, which i have no idea about.

[Norbie]

I saw similar things with my electric oil pressure gauge, inexplicable fluctuations based on throttle input and other non-relevant factors. I fixed it by running an earth wire directly from the gauge to the body of the pressure sensor; apparently earthing via the block isn't good enough. Maybe give that a try, it's easy to test?

[cambelt]

Yes you are right i havent had a lot of racing engine experience but 3 thou big ends , I spose it also comes down to how a engine is run in and if one wants to spend 20000klm running a tighter one in . Also depending on what sort of job is done on keeping everything straight when machining .
I can chime in in saying that 3 thou clearance will use more oil supply than at 1 thou for the same pressure. And 3 thou will grow once its run in.
Dave

[jeffro ra28]

If the oil is doing its job, the clearance should stay the same throughout engine life. Regardless of run in or not