5100 oil system  

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RogerP
(@rogerp)
Active Member
Joined: 1 year ago
Posts: 5
17/02/2019 5:19 am  

Having split 2 oil coolers and just lately burst the oil line to the cooler I am keen to bypass the standard relief valve system.

Is there any reason I could not remove the relief valve and fit a remote filter adaptor and then fit a separate regulator (such as the Peterson unit), a remote oil filter, then to the cooler?


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Doug Smith
(@doug-smith)
Member Admin
Joined: 2 years ago
Posts: 82
06/04/2019 1:39 am  

Hi Roger,

No, that should work.  You'd have to make up something to block / stop the standard relief port and then to plumb into the rest of the oil system but that shouldn't be too hard.  Pluming the relief oil from the remote valve back into the sump will be a bit of a pain - you'd probably Tee it into the oil filler housing or make an adaptor fitting to go into the sump plug rather than try and weld new fittings into the sump.  And of course you'll have to keep an eye on the engine oil pressures as you're adding a degree of length etc to the system and you might find the flow rates and pressures drop somewhat.

The other thing would be to make sure you were using an oil filter appropriate to the remote housing - Jabiru filters have the internal bypass which allows oil through to get to the engine when the oil is too cold to flow through the filter element properly.  Some housings have their own bypass, but generally provided you're using a filter with the bypass you should be ok.

Regards,

Doug.


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RogerP
(@rogerp)
Active Member
Joined: 1 year ago
Posts: 5
07/05/2019 1:49 am  

Hi Doug,

Make that 3 oil coolers!

On re-reading Service Bulletin JSB 004-4 I am becoming convinced that this is the problem with my engine, especially as the porting plate is so similar to those in the JSB. Secondly, having seen the work done by others on you tube in altering the pressure relief valve, it appears as if they are partially altering the effects but are not getting to the root cause.

Since contacting you, I have now swapped to multigrade oil and made certain the oil is around 40+ degrees before applying power. Despite this the latest cooler lasted just over 6 hours of flying. Luckily I was turning base at the time so could drop in OK. Obviously a sure fix is needed and I feel that playing with the relief valve (3rd party remote OR altering the profile) is merely experimenting.

Could I use the template for the 4s and 6s to modify my port plate?

Regards,

Roger


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RogerP
(@rogerp)
Active Member
Joined: 1 year ago
Posts: 5
07/05/2019 3:21 am  

Hi again Doug,

As a post script to the last post, Rod suggested I adjust the relief valve to lower the pressure, but again, the experiments with the relief valve on YouTube suggest that the relief valve is bouncing possibly due to the cavitation. Is it possible, if it is bounce, then lowering spring pressure would exacerbate the bounce?

Roger


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Doug Smith
(@doug-smith)
Member Admin
Joined: 2 years ago
Posts: 82
19/05/2019 4:17 am  

Hi Roger,

If the valve is bouncing it's because it's being excited at a frequency at or close to its resonant frequency.  Reducing the spring tension will change the resonant frequency of the valve assembly a little - so altering that spring tension should make it less likely to bounce.  Changing the weight of the valve will have a similar effect.

Have you tried plumbing a gauge into the system upstream of the relief valve to see what's going on?  It should tell you if there's a restriction (steady high pressure) or cavitation (spiking / unsteady pressure) or something causing the issue.  Blowing a line is a pretty big call - they're usually the toughest part of the system - so it's probably nothing subtle.  I don't suppose the mods you've made to the relief valve would reduce its flow capacity back into the sump? 

Did you get a chance to confirm that your oil filter incorporates a bypass valve?

Regards,

Doug.


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