camshaft oil line restrictors- two thumbs up!

[haycait911]

installed the camshaft oil line restrictor kit from our host on my 2.7 yesterday. can someone tell me if there's such a thing as TOO MUCH oil pressure? seriously, am very pleased, particularily with the idle oil pressure. previously I had to convince myself that it wasn't actually reading zero. now it doesn't get below 20 psi at hot idle! the kit was about a 15 minute install and most of that was getting the squished aluminum seals off the bolt. at 180 degrees it's at 100 psi at 4000 rpm. also, it might be un-related but my oil gauge seems a lot less psycotic, it's not bouncing around now. I can't imagine why anyone would not put this kit in considering the cost and ease of install. Don

[HarryD]

Do what you think is best but I offer this (from this thread - 3.0 Liter upgrade horsepower):

Originally posted by Grady Clay
"so are you suggesting not running cam line restrictors??”

Absolutely.

In my opinion this was a “fix” that Porsche did picking the lesser of two evils. The issue stems from the ability of an SC or Carrera being comfortable to drive at 2000 rpm and sometimes less. The piston squirters are necessary to keep the pistons cool. However they don’t open until 42-56 psi. With full flow to the cams, the main oil pressure at the squirters was too low. They didn’t open until the engine was above 5000 rpm when hot – too late.

Porsche’s “solution” was to limit (restrict) the oil flow to the cams, rockers and all the parts in the top end. Note this also includes valve guides. Of course the restrictor raises the pressure in the main galley that feeds the piston squirters. They then open at lower rpm. The problem, IMHO, is there was already marginal oil to the valve train when hot and low rpm. The restrictor exacerbated the problem

I think Porsche chose to improve the piston cooling at the (evil) expense of valve train lubrication and cooling.

I’m not willing to build a nice engine with any preventable shortcoming.

Originally posted by Steve@Rennsport
I'm in total, complete agreement with Grady on this issue.

Some of the hottest parts of the engine are in the heads and its totally counterintuitive to REDUCE oil volume & flow to these areas that need all the cooling and lubrication they can get.

Personally, I will not use the cam line restrictors and in fact, prefer to upgrade oil pumps where feasible. In addition to Grady's comments about power, improving oil scavenge in the sump by using either the 930 or GT-3R oil pump reduces oil temps and helps power output by keeping the oil level in the sump well below the spinning crankshaft.

After all, what would these guys know that we don't?

[haycait911]

OK, did a bit of math . the stock restrictors have an opening with a cross sectional area of 25mm. new ones have 4mm! I'm leaning toward drilling out the new restrictors to about a 4mm diameter hole which will give me a x-section of 12mm. this will still give me somewhat increased pressure while giving much more flow than the new restrictors currently provide. I would really like to get the hot idle pressure to at least show on the gauge. thoughts? Don.

[Steve@Rennsport]

Don:

FWIW,........These motors really don't need much oil pressure at idle,... Many people get upset when they see the pressure gauge below 10 psi at a hot idle and its a perceptional issue far more than an operational one.

What you really need is sufficient oil pressure above 5000 RPM. Oil viscosity, temperature and bearing clearances determine that.

[HarryD]

Originally posted by haycait911
OK, did a bit of math . the stock restrictors have an opening with a cross sectional area of 25mm. new ones have 4mm! I'm leaning toward drilling out the new restrictors to about a 4mm diameter hole which will give me a x-section of 12mm. this will still give me somewhat increased pressure while giving much more flow than the new restrictors currently provide. I would really like to get the hot idle pressure to at least show on the gauge. thoughts? Don.

Don,

I bit of a thought experiment. The restrictors appear to raise the system oil pressure because the pressure transmitter is on the upstream side of the restrictor. If you move the transmitter to the downstream side, you would see a much lower pressure on the gauge but the reality is that the system pressure is still the same. Would it still feel OK to you?

[haycait911]

Harry, I see what you're saying, I think. my thinking was that the upstream side of the restrictors is where bearings, squirters, etc. are and that's where you need the oil pressure to provide a cushion between the metal surfaces. or, is it more important on an oil/air cooled engine to have the oil moving more quickly/freely thru the engine to aid in cooling. I've opened the restrictors to the aforementioned 4mm diameter orofice and re-installed. before all this the engine had 60 psi at 200 degrees and 6000 rpm, which seems dead-on spec. am I wasting my time on this? maybe I should leave well enough alone and live with a low idle pressure? I'm starting to get that " if it ain't broke don't fix it " feeling. Don.

[haycait911]

Steve, what would you consider 'sufficient' oil pressure above 5000 rpm? I could just keep opening up the orofices until I hit a 'target' oil pressure at a specified rpm. Don.

[TimT]

Note that the VDO oil pressure gauge has been known to be off a few psi.

On my car I was concerned about low oil pressure at idle.

I removed the stock sender, and connected a mechanical pressure gauge...

Which read 12psi at idle, where the VDO gauge didnt register at idle.

[psalt]

"Harry, I see what you're saying, I think. my thinking was that the upstream side of the restrictors is where bearings, squirters, etc. are and that's where you need the oil pressure to provide a cushion between the metal surfaces. or, is it more important on an oil/air cooled engine to have the oil moving "

It does not work that way. The gauge oil pressure has little to do with the "cushion between the metal surfaces". The cushion is supplied by the hydrodynamic pressure created by the rotating crankshaft. This pressure can be as high as 5000 psi. The pressure created by the oil pump is used only to delivery enough oil supply to the bearing. How much is enough ? At idle there is no load and a few psi is sufficient.

Oil pressure gauges have presented psychological problem for OEMs for years. There are famous cases at BMW and Jaguar with customers insisting there are problem when none exist. Check you pressure with a mechanical gauge and forget about it.

[mb911]

I suggest you talk with engine builders regarding this. some of the information out there is misinformation. actually allot of it is so be careful. I concluded that after much research that the guys building engine after engine would know best not the weekend warrioir that has done a hanful. so when rebuilding mine I called around and the conseses was use them as all 911 engines from 91 up used them. allot has to do with quality of oils these days it is not as bad as every body says.. Actually oil quality is very high so another example of mis information.. I know flame away ! But if most the respected engine builders use them thats another vote for them


anyhow looks great