Forged Rb25 Lifter/possible Oil System Problems.

[Dale FZ1]

Powercruise format with a few successive squirts along straights but nothing really sustained isn't likely to result in extreme oil temps that requires a cooler.

Suggest you concentrate on the issue which appears to be the lifters. Removing cams and lifters for cleaning/reinstall will take time but not lots of $$.

Also suggest you speak with the cam manufacturer and determine whether the profile you are running is compatible with hydraulic lifters.

[89CAL]

The problem with having nothing to cool the oil (e.g. removing the heat exchanger) is that if the oil does get a little warm, there is no failsafe. The 25 comes with a cooler, not to mention its designed to work in Japan which is cooler than here.

Im not saying it absoloutly 100% will cause issues. Its just not a risk I would like to take.

As for the cams, im still a bit confused why people fit big cams on 25's that, at the same time, remove VCT. I know with my baby cams ive 'just for fun' unplugged the VCT solenoid and gone for a drive and its not anywhere near as nice

These are only my opinions, I dont expect anyone to agree/follow what I say. Noone is necessarily 'right' when planning an engine build

[DanielH]

The cams are a drop-in hydraulic cam for an rb20det, I think you're right about the oil cooler situation, and I opted for these cams because the car (VS commodore ute) was already running an rb20det, I got the car and put together the rb25 so it would be a "drop in" plug and play affair, already had the nistune so it was just a matter of running all the rb20 accessories, some gtr injectors, give it a tune and call it a day, I really wanted the aggressive idle and a bit of an increase in top end was always a bonus.

It's running a big equal length highmount manifold, gt3076 with .86 rear and a greddy intake, it was never gonna be like a stock 25 and I love the way it goes, it's so aggressive, tons of fun to drive, I just need to sort out this problem.

I'm gonna slap the cooler on as quick as I can with some gauges and put some good oil in it, if that doesn't work ill disassemble and clean up a spare set of lifters and swap them in.

Edited January 6, 2015 by DanielH

[DanielH]

Don't forget your car is tuned to have the VCT working, with it turned off the tune would be way off and the cam profile probably wouldn't work that well either, my cams are designed to be used in a fixed situation and you don't notice it, once the turbo hits its on, in my case it's just wheelspin everywhere for the first 3 gears!

[DanielH]

Have fitted a cooler/relocation kit and my gauges as seen below.

Have yet to drive the car and test any changes but I have just over 5 bar of oil pressure when cold at 1000rpm, drops to just above 4 when warm, and sits on about 5.5 at higher engine speeds.

Has anyone got any rough guidelines on a good safe oil temp for 20/70 mineral oil? It's Penrite hpr30.

Also the coolant temp gauge sender was not connected in the photo.

[DanielH]

Also I previously had completely isolated it engine temp, after the engine had completely heat soaked after numerous dyno runs or sustained load on the road it would start to tick.

You can see the little dip in power right at the end of the run.

[jiffo]

Cal from memory the 25's VVT is activated through to around 4700rpm, then is switched off.

It's primarily designed for easier starting and then a "normal" driving range.

As you've got Poncams, I'd suggest the tuner will have raised the cut off point to around 6000?

In your situation, from around idle to 6000 could be similarly accomplished with a solid advance of the inlet cam.

So unplugging the VVT solenoid would certainly make your setup feel lazy.

[Badgaz]

try running some pro-ma mbl8 through it as another cheap solution, fixed my lifter problem....and personally i wouldn't run anything above 10w50 oil.....70 is too viscous when hot for the lifters IMO.

[KiwiRS4T]

I use Motul 15 40 - why do you want to use mineral oil? Full synthetic gives you a better safety margin for the track.

[DanielH]

I went with the thicker oil seeing as though my problem only rears its head when everything including the oil is fully hot, and presumably thinned out, went with the mineral oil due to price and availability at the time, it doesn't see the track, with exception to powercruise where it will see a bit of abuse but nothing like a drift/track car.

Edited January 12, 2015 by DanielH

[Badgaz]

oil gets thicker when its hot.... full synthetic is best. run a flush everytime you do an oil change...

[AngryRB]

Are there any air bubbles in the oil, some lifter problems are caused by air being sucked up through a leaking pickup seal/gasket

[GTSBoy]

oil gets thicker when its hot.... .

Not true. Not true at all.

Oil, as with pretty much EVERY liquid, becomes less viscous as temperature increases. Motor oils have long had viscosity modifiers in them to change the behaviour of the oil's viscosity with temperature. So your 10W-40 oil behaves like a 10 weight oil at low temperatures and like a 40 weight oil at high temperatures. But I can assure you that it is still less viscous at engine operating temperature than it is when it's cold. You only have to look at the difference in flow/pour speed between putting fresh oil into the engine compared to dropping hot oil out of the sump. If you doubt me, put your fingers in each of them and feel it.

Edited January 12, 2015 by GTSBoy

[Badgaz]

Lol stop trolling me, so i can see what you are saying it's now confused me somewhat.... But i can't type what's in my head on my phone lol

[GTSBoy]

[Badgaz]

but thats not pouring the oil through a fixed diameter like a lifter...so surely the higher viscosity means its thicker through a given sized hole? does the oil expand with the heat also? i understood the thicker/more viscous oils at temperature don't flow so well but do provide better oil film on the surfaces?

[GTSBoy]

It doesn't matter. Viscosity is viscosity. If it is thinner and easier to shear between your fingers, then it will flow more easily through a hole too. Same same. Hot oil is thinner than cold oil, regardless of multi-grade. So you have to forget your idea that the hotter oil is more viscous, because it simply isn't. It behaves AS IF it was a 40 weight oil at that temperature, but that viscosity is still lower than what the 10W-40 is when it is cold. ie, it is thinner than what a 10 weight oil when cold.

This graph is nice. You can see the red line is 40 weight oil. The purple line below it is 10W-40. So when you have those two oils up at 100°C then the viscosity is a lot less than the 10 weight's viscosity is at 40°C. It's like 25% or so.

Density will change with temperature. Like most materials, oil will get less dense (ie, expand) as it gets hotter. But this effect is of no importance in this discussion. The oil pump pumps on a volumetric basis, not on a mass basis.

[Badgaz]

sorry so i guess i was saying earlier that 70 is too viscous for the rb25....is that better?

[Badgaz]

http://www.bobistheoilguy.com/motor-oil-101/

just read that ...pretty good read.

[AngryRB]

interesting read, so if that's correct we should be running thin oils like 0-30w for the street and if the lifters are dirty you'd need thin oil to up the flow into them?

Edited January 13, 2015 by AngryRB