G'day!

I been reading through aircooled.net's catalogue about the use of high volume oil pumps and using thinner oils to maintain same typical stock oil pressure (to not overpower the relief system), but the combo apparently results in increased oil volume/flow rate for cooling bearings etc.

Is this worth while for a hypo motor? If say i had a 30mm or 32mm oil pump, how low a viscosity oil would you go?

Thanks,
Just shopping around
Chris.

For what it's worth, Chris, I changed to lighter oil about 2 years ago [No.8 Beetle]. Dave Mawer, a friend who would know more about race cars than most, suggested that the reason for my high oil temps could be because the oil flow through the external oil cooler was too low.

As usual, Dave was right, and after changing to 5W-50, the temp. dropped by 10-15 degrees. There was a slight drop in pressure at idle, but none at normal running speeds.

No other changes were made - just the oil.

Greg

Be aware that higher flow oil pumps and high revs have the ability to drain your sump quicker than oil can flow back.
I had an extended sump on my car and was using a 26mm pump and still the main bearings showed signs of starvation.
I am now fitting a 4qrt sump. Mind you I am revving to 6800rpm but you mention hypo motor also.

I agree with moderation regarding the size of the pump. biggest I'd go for in the average full flow system is 30 mm for the draining of the sump problem. Oil viscosity is relative to bearing to crank oil clearances so if running tighter oil clearance (around .002") a very light grade oil is useable. Normal clearances are around .0025 - .003" and the oil should be in the 30 - 40W range. Heavier oil, 50W> is if your bearings have excessive clearances either by design or more likely age related.
I also believe the oil volume is important. The only cooling the piston receives is from the oil wash it gets from the big-end beside it. High viscosity oil is more dificult to squeese through the bearings, resulting in potentialy higher pressures, but less volume, ie. less cooling to internals.

Thanks lads.

I'll be having the bottom end dynamically balanced for a max of 6000rpm however the plan is low down torque for the baja with possibly future flexibility and adequacy for hyper revs (to 6000rpm) if i decide to change the head combo i'll be running, which at the moment is for torque focus (high velocity, lesser volume etc etc with the a pair of rebuilt single port heads sitting in my office fitted with 39x35.5 valves, dual 32DIS turbo carbs adapted to dual kaddie manifolds, CT25 scat cam, 74mm forged CW crank, forged chomoly H rods, ratio rockers, aluminum case with 3.5mm raised deck, about 8.5:1 CR). Bit of a 'wierd' combo.

But at the moment a rebuilt CT26 turbo and air-to-air intercooler awaiting the 2054 which will assist mid to top end when the heads start choking at high revs, and i'm thinking more oil wash/slosh will help relieve that induced bearing heat from the greater pressure on the conrods when boost hp kicks in. That will be stage two after N/A run in, and will subsequenty bring the CR down with some barrel shims.

The toyota engines used to run (dunno if still do) oil squirters on the piston skirts to cool down their turbo engines, i spose more oil slosh will assist the same. The oil spraying on the piston skirts i read was an issue with the single relief cases increasing oil consumption but would assist i guess in cooling them down haha. Particularly with the alum case apparently running hotter.

The engine won't be crazy like what you guys run, but i assume the greater oil volume/flow will help i assume? Although prime cooling focus is in the heads (going to be looking at undersized alternator pulleys with welded fan), just shopping for the right oil pump for this combo with longevity the key and a dream goal of around 130-150hp boosted, maybe 85hp n/a. What you guys think? I know there is generally an angst against single port heads, but i hear they are strong so boost wise it should tolerate.

Quote:

Originally posted by HappyDaze For what it's worth, Chris, I changed to lighter oil about 2 years ago [No.8 Beetle]. Dave Mawer, a friend who would know more about race cars than most, suggested that the reason for my high oil temps could be because the oil flow through the external oil cooler was too low. As usual, Dave was right, and after changing to 5W-50, the temp. dropped by 10-15 degrees. There was a slight drop in pressure at idle, but none at normal running speeds. No other changes were made - just the oil. Greg

gtx2 is or was 20w50