Jab 3300 Oil Pressure Comparison and Oil Additives

[MichaelFarley56]

Hello Everyone,

I was hoping to start a thread to ask all of you Jabiru 3300 drivers what oil pressures you normally observe while flying.

I now have around 10 hours on my second generation hydraulic lifter engine post rebuild, and I normally see 36-38 psi in cruise (2700 rpm with oil temp around 190 F). I know that these numbers are "in the green" according to the Jabiru manual but I wish I could get it a little higher. I've added a third washer under the pressure maintaining valve and spring but my oil pressure didn't really change, so I was just curious what everyone else is seeing.

According to Nick at Jabiru/Arion Aircraft, it's common to see hydraulic lifter engines running cruise pressures in the mid 30's and even down to 30 psi with no issues, and the hydraulic lifter versions are happiest running mid range oil pressures.

On the other hand, I am happy to see oil pressures in the 20-25 psi range at idle after landing (hot oil) at 1000 rpm. (I know some people are having issues with low oil pressures on a hot idle).

And while I have you, does anyone use CamGuard or any other additive in their oil? I haven't tried it yet but I'm tempted (unless anyone knows that it's a bad idea).

Thanks everyone!

[tx_swordguy]

I think your numbers are fine. What is your WOT oil pressure. I would not use camguard until 50-100 hrs on your rebuild. I use it in my 3300 based on mike busch recommending it. I have heard you need to let everything run in and seat, Bearings, rings etc prior to putting it in or you may not get things seated properly causing more oil usage than you should be getting.

[MichaelFarley56]

Good idea Mark! Yeah my plan is to get 100 hours on the engine before any oil additives or oil analysis samples. Let everything get nice and broken in first!

WOT I will see oil pressure drop slightly: a full throttle climb out I generally see 32-35 psi for a few moments but it normally returns right back to 36-38 psi and stays steady after level off.

[wlarson861]

With generation 4 engine I see 50 psi through warm up and take off. At around 180 oil temp I saw 46 psi, a slight drop at 2700 cruise setting. Hot oil on landing and at idle still showed 40 psi.

[sonex892.]

Mike. If your engine has a VDO sender that could be giving you incorrect readings. A while back I was concerned to see the oil pressure reading getting toward the bottom end of the scale. It was down to around 29psi. I added a washer to the relief and even stretched the spring. It only went up very slightly.

I then did what I should have done first, tested the old sender. They are just a variable resistor with a diaphragm. I hooked it up to a compressor with regulator and measured the the resistance with a multimeter vs the psi. I found it to start to stick around 30psi and then get totally stuck at 35 psi. The sender doesn't know if it is air or oil.

I bought a new sender the oil pressure went straight up 60 psi. Which was then too high. I bought a new spring removed the additional washer it now runs around 50 psi. I have a gen 2 with almost 450hrs. Those senders also don't last forever. I'm now on my 4th sender. The first 2 were VDO copies, supplied by Jabiru branded ELO. They both failed very quickly but I got 300+ hours out of the 3rd, a genuine VDO.

As far as additives go Jabiru Australia say don't.

Steve
Sonex 892

[MichaelFarley56]

Great point Steve and thank you for bringing that point up! I have ordered a new VDO sensor, #360 001 and will swap them the next time the cowling is off. The sensor on my engine now came with the engine so I have no idea how old it is.

It sounds like the Jabiru is hard on these sensors anyway so having a spare on hand is probably a good investment!

[sonex1374]

Myt Gen 3 roller cam engine runs at about 45-55 psi, with a slight tendency to drop a few psi when warm and/or at idle. Ben and Pete at Jabiru USA always said that 30-35 psi when warm at cruise was fine, and dropping even into the teens when hot @ idle was still ok. The earlier hydraulic lifter engines were rather "leaky" inside and oil pressure was commonly lower than the older solid lifter engine. Even so, these engine never exhibited any signs of poor lubrication so long at the oil pressure was still in the green. I don't think you have anything to worry about.

The pressure relief valve on the Jabiru isn't really a pressure regulator, so adding washers or stretching the spring won't increase oil pressure under most circumstances. It is helpful, however, if you see fluctuating oil pressure at high RPM. This fluctuating oil pressure in the relief valve opening and closing rapidly, and stiffening the spring to help keep it closed in normal operation is a good idea. Of course, you can't go too stiff or you risk blowing something out if the PRV just won't open at all. Adding 1-3 washers is approved, and will be fine.

I use camguard in my engine, adding about 3-4 oz with each oil change. There seems to be a growing body of people using camguard that are happy with it, and the chemistry is pretty familiar stuff (similar to the anti-wear additives recently added to several oil blends). I also waited about 100 hrs to start using it.

Engine vibrations have been prematurely wearing out oil pressure senders for decades, and the Jabiru is susceptible to this. You can remote mount the sender using a flexible connection, and if done right will likely be the end of the issue. Of course there's the possibility of a leak, so you'll need to use care is the solution you craft. Otherwise, plan to replace the sender every 200-500 hrs and live with the added maintenance. The senders are in a demanding environment, so don't bother with low-cost knock-offs - I'm quite certain they won't last even this long.

Jeff

[sonex892.]

For engines still in the warranty period. The use of oil or fuel additives voids the warranty.
https://jabiru.net.au/wp-content/upload ... 0002-9.pdf page 95

[sonex1374]

The prohibition against fuel and oil additives has been something that I've struggled with. On the one hand I agree with Jabiru - why should they be responsible if you poor sand into the engine and call it an "additive". On the other hand, not everything is automatically bad, and is in fact already found in some approved gas and oil we already may be using (like techron in the fuel and anti-wear chemicals in Phillips XC oil). It's an area where the only safe option for Jabiru is to state that they haven't tested, nor have they approved ANY additives, and thus can't be held responsible for the outcome.

I hope that Jabiru doesn't use this policy to deny legitimate warranty claims as a catch-all defense, but at the same time if there's a clear connection to the engine problem that is traced any particular additive, then so be it.

As a last thought, Jabiru has variously approved AVGAS only, MOGAS with ethanol up to 20%, MOGAS without ethanol, AVGAS/MOGAS mixture, and now (I think...) MOGAS with up to 10% ethanol. They keep changing their mind on approved fuels. They do however talk about "bad gas" and that it might be damaging to the engine even if it falls into an approved category. The message to users is that we still are expected to exercise good judgement in what we feed our engines. That's a fair point, in my opinion.

Jeff

[MichaelFarley56]

Thank you for all of the reply's and information guys!

Just to write it down for future reference, I took Steve's advice and ordered a new VDO oil pressure sender, part #360-001 from Jegs automotive ($42 or so). After installing the new pressure sender my results mirrored Steve's. My readings then indicated that I was running around 65 psi under most flight conditions, so I ended up replacing my PRV spring and reducing the number of AN4 washers under the spring to 2 washers.

I now see oil pressure around 55 psi on startup and in cruise, and pressure stabilizes around 40 psi on a hot idle (taxiing back into the hangar).

I should have known; my old AeroVee had a tendency of eating those VDO sensors with alarming regularity ( I think I was on my 5th one after 300 hours), so I'll be purchasing a spare for the Jabiru and keeping it handy for when I need it!

As for the additives, I'll address that later after I get at least 100 hours on the engine. I now have just over 10 hours on it and I'm loving the perforamance boost thus far!

Thanks again to everyone who chimed in with advice...I really appreciate it!

Mike