custom AN cam lines

[proffighter]

Originally Posted by wprater

Roland, how do you control the pressure the sender sees? Per comments above, it's supposed to be calibrated to what a bearing would see.

Well, that's nonsense. 964 console has no orifice either and sensor has one calibrated port built-in.





No need for anything else

[wprater]

Im not clear on the issue, but some seem to think we need to calibrate the flow with that tube that goes through the sender block.

I have the same t-stat but its just hollow inside, so it'll see full flow from the system. The sender I have only has one connector on top for the wiring.

I'll see correct pressure on my 3.0 case if Im to move the sender to the 964 t-stat? Here are pics of me moving it.

[Walt Fricke]

wprater:

I think Soy Racer had ingested too much soy sauce when he said that the hollow banjo bolt for the stock location of the oil pressure sensor was somehow calibrated to make the pressure read by the pressure sensor come out right. Several subsequent posts corrected this, and one in some detail (also noting that the sensor itself has a very very small hole letting the oil in, and explaining why, which I had not previously understood).

So just cross Soy's post out on this one. He got that one wrong.

Pressure is pressure. The sender is calibrated so that X amount of pressure pressing on its Y area of diaphragm against a spring of Z rate will move the wiper on a potentiometer a distance which produces the resistance the gauge shows as the PSI or bar pressure in the oiling system.

One engine I bought had, instead of the steel block, just a banjo sandwiched in there with a shorter hollow bolt. Maybe the 2.4s came that way, or some earlier motors? The OP sensor just screwed into the banjo. Plenty of oil flow area, much bigger than that hole in the picture, worked just fine. As does putting the sensor where the idiot sender goes, or into a modified piece (or the 964 - I didn't know they had that) which goes where the thermostat valve for the engine mounted oil cooler goes on 3.2s and earlier motors. Those all see the full pressure the pump puts out against the total flow resistance of the engine (and the relief valves which limit its maximum).

Someone out there surely sells an M12 to M10 adapter, if that is needed. I think some 911 models came with just that for the idiot sender. Look at part 61 in the parts catalog for a '72/3 - 901 101 175.01. It doesn't give sizes. Those years did have the banjo for the pressure sensor.

Me, I've decided the way to go is to weld or braze AN3 fittings onto the stock lines where the crimped on rubber starts. If you bore out these fittings a little bit, and cut off the bulge in the steel line, it will slip nicely inside the AN fitting. Haven't done it yet, though, as I don't really need to (despite having acquired a number of spare stock parts here and there and from Carrera Tensioner kits), and my attempts at brazing have never been all that successful - it never seems to wick up like solder on copper plumbing pipe.

I modified a thermostat valve to be always open (oil always goes to the cooler ports, though I put an oil filter on those ports, not a cooler), and put the pressure sensor there. Worked fine.

A simple solution could be to buy a combined idiot sender and oil pressure sender. The picture showing that fat sender can with two terminals on top is such a sender.

Me, I like to install a 30 pound idiot sender. You can buy an adapter to go from 10x1.00 thread to 1/8th inch IPT, and use an Autometer sender. If you try to screw 1/8 IPT threaded things into the idiot sender hole, you might think it fits, and it might work - once. The threads are almost the same pitch The threads will be mangled some after that, though, as the IPT is tapered, which is how it seals. Porsche used machine threads and a crush washer to do the sealing, which is the way to go.

The issue with the substitute hollow bolt fitting is that its holes won't line up with the hole in the big steel block which holds the pressure sensor. Porsche put that groove there so that the groove would always line up with the hole in the steel block

[wprater]

Walt,

Thanks for the detailed overview! I should have re-read my whole thread after coming back at this, it's clear now that the details of how the pressure system were indeed laid out for me.

Really appreciate all the info everyone in this post has laid out, it's extremely helpful!! Hope this thread will be helpful to others as well.

Im going to move the sernder to the M18 port of the t-stat and keep the idiot sender where it's at. I have all the parts for this now.

Already have my AN lines and adapters on their way and will be putting this all together next week when they arrive. Will update the thread with my completion!!

Cheers,
Will

[KTL]

Good info from Walt as always. He makes a good point about the warning light sender he uses. I'll add to what he's saying & why he's saying it. He chooses to use a 30 psi warning light switch because it gives him additional protection against massive failure when oil pressure is lower than desired. I've been there, seen that in my own engine & I totally agree with what he's getting at. Point being here is that the Porsche warning light switch comes on at nearly zero oil pressure. I don't know the number off the top of my head but it's really low- too low.

Reason Walt mentions the 1/8 NPT thread issue is because he's exactly right. M10x1.0 thread size is so darn close to 1/8 NPT (27 threads per inch) that you can mistakenly think you have one or the other and be wrong.

All the above I shared is moot if you're sticking with the Porsche switch. Just wanted to give you a heads up on the benefit of the higher pressure switch. The downside is that a high pressure switch will typically turn on the light at idle when the engine is warmed up, since the engine usually makes a little more than 1 bar (~14 psi) at idle. So it can be a nuisance to some people to see the light come on all the time. On a racecar/track application, the nuisance is much less and we're always hoping we don't see that light at all when the car is cruising around on the track.

[willtel]

Just tagging along to see how this turns out. I thought I was the only one that cared what that stuff looked like.

[wprater]

Just realized that I never sent an update on my lines that I made! tsk tsk on me.

Ended up moving the pressure sending unit and oil temp to the t-state in the rear of the motor. Removed the idiot light for now, but I could place it in the other block off port of the t-stat, or get awn external unit as Walt suggested.

Here is the end result, but Ive swapped out the fitting for black ones.