Mistakes were made, my R34 Story

[Kinkstaah]

Went over my datalogs on a whim and noticed a worrying combination of events.

High RPM
High Temperature
Low Oil Pressure
Knock Retard

I bought some 10w-60 because I actually think this will be better going forward given track temp is 125C and 10-40 will actually be thinner in those environments. I know I had a leak but it's not entirely sure how much pressure loss can be attributed to that.

The knock retard does correlate with all of the above. When it's not present oil pressure is higher. And by 'low' I mean at 6800 RPM the oil pressure was recorded as low as ~35psi pretty constantly. Which is obviously very not good. I'm hoping that thicker oil that ISNT LEAKING will result in a bit more pressure when I need it.

Also in the last session I got a very spongy break pedal. I bled the lines as the car is on jack stand right now with the wheels off and I noticed... no air in the lines? Maybe the tiniest bit of tiny frothy bubbles for the first 0.1 seconds of bleeding the whole car?

The breaks did come back to me after I backed off (and felt fine driving normally). Doesn't appear to be any leaks anywhere that I can see. Any thoughts on that?

[Duncan]

I don't know what you should expect with an LS, but the oil pressure sounds terrible, sorry.

As for the brakes, you can get fade from the pads not just the fluid, although generally that feels like a wooden block not doing anything while fluid feels like an oh shit there is no pedal so you can generally tell. What pads are you running front and rear?

[Kinkstaah]

Yeah the rule of thumb with an LS is 7psi per 1000rpm. That is decidedly not enough at 6800rpm. I mainly looked for the scenarios where knock started to be picked up and it was later in the session when things were hotter, and oil was thinner, and the pressure was lower than it should be.

(i.e very horrible).

I am hoping with thicker oil (I was running Penrite ten tenths 10-40, the manual specifies 10-30) that does not leak that it's much improved at that time!!!

I am using Project Mu Club Racer CR pads. I'm also using the Project Mu 335C fluid. The symptoms imply that it was fluid that boiled, but no bubbles seemed pretty weird to me when I bled it today. I want to try Castrol SRF as it has a much higher wet temp but, well, I have new Project Mu fluid lol... so I should at least use that.

The pedal on track was really noticable. It went from basically normal feeling to instantly near-floor. The car did pull up as before, it was just very much nearly at the floor before the brakes engaged. At that point I pretty much decided the day was very done, it did *kinda* come back during that very slow cooldown lap into the pits. Felt perfectly fine driving home.

[The Bogan]

Would a Mellings oil pump be a viable option 

From my time with a LS, and talking to tuners and LS specialists, the "weak" OEM oil pump is one of the first things they recommend to swap out if I was going to give the engine any high RPM

I opted for a Mellings high volume, with the high pressure springs and I never had a issue with it

Cost wise they are not expensive in the scheme of things 

[Kinkstaah]

(it is a brand new ported mellings pump)

I suspect the lack of pressure is due to the leak. It was *not* that low in other logs of oil pressure in the past. It wasn't that hot either, but not far off.

[GTSBoy]

I take it that the knock retard is from bearings tapping a little tune?

Thicker oil is a fragile bandaid. You need a much bigger oil cooler and probably the bigger pump being discussed.

[Kinkstaah]

1 hour ago, GTSBoy said:

I take it that the knock retard is from bearings tapping a little tune?

Thicker oil is a fragile bandaid. You need a much bigger oil cooler and probably the bigger pump being discussed.

I don't know it is due to that. It could just be due to load on track being more than a dyno. But it would be nice to rule it out. We're talking a fraction of a second of pulling ~1 degree of timing. So it's not a lot, but I'd rather it be 0...

Thicker oil isn't really a "bandaid" if it's oil that is going to run at 125C, is it? It will be thicker at 100 and thus at 125, where the 40 weight may not be as thick as one may like for that use. I already have a big pump that has been ported. They (They in this instance being the guy that built my heads) port them so they flow more at lower RPM but have a bypass spring that I believe is ~70psi.

I have seen 70psi of oil pressure up top in the past, before I knew I had this leak.

I have a 25 row oil cooler that takes up all the space in the driver side guard. It is interesting that GM themselves recommend 0-30 oil for their Vette applications. Unless you take it to the track where the official word is to put 20-50w oil in there, then take that back out after your track day is done and return to 0-30.