Author Topic: Oil Pressure (Read 10514 times)

tim_s · « **on:** December 19, 2006, 05:03:37 PM »

Hi guys,
I'm going to rebuild the spring assembly for the oil pump shortly, and was wondering if anyone had attempted to slightly raise oil pressure by packing washers in the spring assembly? I'm not too happy with the oil pressure at the inlet side of the cylinder head; but this has been an issue since before I owned the car (I bought the car prob 5 years ago at 70k miles); while replacing parts in there I'm wondering if i could just tweak it up to help with higher rpm running. Just an idea at the mo, but was wondering whether anyone has any thoughts?

nickmpower · « **Reply #1 on:** December 19, 2006, 05:58:24 PM »

seems like it should work, i would talk to a machine shop or something before you go through with it though

silverblades181 · « **Reply #2 on:** December 19, 2006, 06:24:44 PM »

Adding shims will only compress the spring, it won't add to it's calibrated strenght which is what holds the valve. If you want more oil pressure, I'd suggest getting a stronger spring or better pump. But too much pressure is not better then not enough. If I were you, I'd go another route to ensure that the head is lubricated appropriatly. See how they do it in high reving race cars that are subject to big Gs.

romkasponka · « **Reply #3 on:** December 20, 2006, 02:16:05 AM »

Quote from: silverblades181;15890

Adding shims will only compress the spring, it won't add to it's calibrated strenght which is what holds the valve. If you want more oil pressure, I'd suggest getting a stronger spring or better pump. But too much pressure is not better then not enough. If I were you, I'd go another route to ensure that the head is lubricated appropriatly. See how they do it in high reving race cars that are subject to big Gs.

washers will help.

tim_s · « **Reply #4 on:** December 20, 2006, 10:53:35 AM »

Quote from: silverblades181;15890

Adding shims will only compress the spring, it won't add to it's calibrated strenght which is what holds the valve. If you want more oil pressure, I'd suggest getting a stronger spring or better pump. But too much pressure is not better then not enough. If I were you, I'd go another route to ensure that the head is lubricated appropriatly. See how they do it in high reving race cars that are subject to big Gs.

Any more info regarding other routes etc?
I understand what you're saying regarding spring rate remaining unaffected by adding shims (assuming that the spring rate is not progressive), but regardless increasing the compression on the spring, the force on the valve will be greater, right (and thus more force required to move the valve and relieve oil pressure)? I'm not looking to significantly raise oil pressure, but am not too happy with the current state of affairs with regards to the inlet side of the head; its caused light scoring of the cam bearings etc over time, which I've polished out, but don't want a repeat. I also think this may resolve some tapping from the inlet tappets.
On another tack, anyone know what the difference between m42 and m44 oil pump rotors is? They have different p/nos, and the m44s I've worked on seem to have impressive oil pressure.

sheepdog · « **Reply #5 on:** December 20, 2006, 12:52:35 PM »

Too much pressure is not a good thing. Racers use high volume pumps which gives them slightly higher pressure due to the extra fluid, but just raising pressure can damage the bearings. Febi's pro-built engine uses a stock pump, I think we should be fine.

If your head is not getting enough, either look into a new pump and timing housing (you need both) and get some brushes to run down the oil channels and clean out the sludge (brushes made for this purpose are available, try Summit or PAW). Even if you managed to raise pressure and vollume, there is nothing to say it will do anything dramatic on the top end if there is a restriction in the feed channels.

silverblades181 · « **Reply #6 on:** December 20, 2006, 02:19:31 PM »

Yeah I thought about it a little more and adding shims will slightly raise the pressure but like Sheepdog said, more pressure might not be the answer. When is there an oil shortage in the head? During normal driving or during hard driving and high revs? How old is your pump?

tim_s · « **Reply #7 on:** December 20, 2006, 03:15:13 PM »

Thanks for the replies!
The engine is clean throughout, and the oil pump rotors are in good condition. I only built the 2.1 about 10k miles ago. All oil channels are clean, there is no sludge anywhere; I've owned the car since 70k miles, done 5k oil changes with synthetic oil, plus I cleaned every single component when I rebuilt the engine. It's safe to say the engine is very clean and no passageways are blocked. I'm going to change the spring, valve and pickup soon, as I didn't do these when I rebuilt; i'm regretting that now! Will prob do the oil pump rotors too for good measure.
The oil pressure at the oil switch was ok when I last tested it. This is not a major issue, but the oil system doesn't seem to be as good as perhaps it might:
Cyl head pressure seems low as there's more or less no oil being blown out the rocker cover breather and there's inlet lifter noise. Coupled to the fact that the inlet cam had some scoring, and whirred since I owned this car (until I polished the bearings etc), I've come to the conclusion that even before I owned the car (the inl cam whirred when I bought it, over 50k miles ago), there's prob been an issue with oiling on the inlet side of the cyl head.

As for increasing oil pressure not necessarily being a good thing, I understand that too much oil pressure can be problematic, but I'm only considering a very slight change, not to an extent where this would become problematic for bearings etc. I've seen similar methods used for a very long time in motorsport; in fact it was thinking about old rally minis that got the idea into my head in the first place!

I think I'll probably just rebuild the oil pump and check over the lower timing case to make sure all is well. I will do some comparisons between my oil pump once rebuilt and an m44; should be interesting.
I'm hoping that its just a partially blocked pickup, or some air getting through, but the engine is worth too much to take any chances with.
Any other ideas gratefully received!

tim_s · « **Reply #8 on:** December 20, 2006, 03:17:34 PM »

Oh and the lifter noise is intermittent; sometimes it does it more or less all the time (not at idle, but coming off throttle and often on throttle too!), other times I can do a journey and have very little sign of noise. And it is not timing chain (new) or injector tick!
It can be infuriating though, as an engine I've spanked all this money on should sound good, not like a tractor!

bmwman91 · « **Reply #9 on:** December 20, 2006, 03:21:02 PM »

Try something less viscous, like veggie oil.

lol
But seriously, I am interested in the results of this. My lifters are noisy as well and I have wondered about sufficient oiling.

tim_s · « **Reply #10 on:** December 20, 2006, 03:33:23 PM »

Oh yeah bmwman, you reminded me of something I hadn't mentioned to you guys. I changed my lifters over a few months back for some spare e36 lifters I had lying around to try to reduce lifter noise. My old lifters ended up in a much newer e36, in which they were jus about silent. In my car it is mainly the inlet lifters that make some noise.

kowalski · « **Reply #11 on:** December 22, 2006, 04:00:15 AM »

what if its the lifter tray that is worn, have you checked the bore sizes of each and compared? perhaps its moving around a little...

tim_s · « **Reply #12 on:** December 22, 2006, 02:02:42 PM »

nope, good call but its not that! Noise is intermittent for a start, plus i think the problem has spanned two sets of carriers. I drove the car for the first time in a while today and the noise really isn't too bad and is intermittent enough that i think new lifters would cure it; i'm still going to do some work on the oiling though as regardless I'm not convinced its getting adequate oiling there. The breather not getting much oil blown through, for instance, is not a good sign, nor the gradual slight scoring that the inlet cam had. I have a 264 inlet cam to put on at some point, I'll change the inlet lifters then.

bmwman91 · « **Reply #13 on:** December 22, 2006, 04:22:44 PM »

So you are not seeing any oil buildup in your throttle body? There really should not be much at all, with proper pressure or not. The tick is something I have tried repeatedly to figure out and have not as of yet. From the sound of peoples' experiences, it must just be some innate behavior. Both of the 318iS's I have owned tick loudly. Personally, I think the injectors play a big part in it.

tim_s · « **Reply #14 on:** December 22, 2006, 04:46:45 PM »

Hi bmwman, if you recall I'm running ITBs not a signle TB; but no, I don't see much oil coming off the rocker breather. I should be seeing some I'd imagine the way its been used; on m44s I've replaced the recirc valve in the past when they start to recirc oil too much and consume oil/foul up the inlet, I seem to have the reverse problem with mine.
tbh I'm a bit surprised at all the alternative theories, although I welcome the input and like the food for thought. I've taken the scored cam, lifter tick and not much recirc'd oil as pretty conclusive evidence that oil pressure is a bit low at the inlet side of the head. any other theories must be a fair bit less likely.

I don't believe its innate behaviour as such, but does seem to be pretty common on the older engines; I don't often see these problems with later cars. I'm interested to see what impact the work I'm going to do on the oil pump pickup and spring etc will have. I'll pop some new tappets in soon too.