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Miata Oil Pressure


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Noticing that our NA6 miata has 48psi of oil pressure when racing but 52psi (relief pressure) under caution (elevated RPM). I do not feel oil temp is the cause as the change appears immediate. When racing at 5500-7200rpm oil pressure reads 48psi; under caution 3500-4500rpm the oil pressure is back up at 52psi. My Concern is aerating or cavitating oil. Is this an Aeration problem and if so.

-Problem with oil (SAE30, straight, non motorsports specific)

-Oiling system (any known improvements?)

 

Thank-You

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Minor aeration or oil temp swings perhaps. Need moar info. Got a real oil temp gauge?  Not overfilling?
I’d also suggest a proper race oil.

 

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Posted (edited)

No temp gauge. Not overfilling. It looks like according to spec 48psi is acceptable. It is more concerning that the psi is lower than that if a lower RPM which then makes me question its presence of air. Previously I ran a CJ4 rated sae30. At watkins glen I ran an SN rated sae30 to hopefully get greater anti foaming additives. If this is foaming/cavitation, it could not be solved with viscosity right? That will only mask the presence of the air in the oil.

Thanks 

Edited by wd6681
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So it is lower under load than free reving?  But you're reading the pressure at the same RPM, the only difference is under load vrs under no load?

 

48 is a bit lower than I would want for 7k RPM.  Rule of thumb is 10psi per 1000 RPM.

 

Unless you want to be nervous about oil temps or want to add an oil cooler, don't look at oil temp in the pan.  It will tend to scare you.  Just follow the motto that "ignorance is bliss and I can't do anything about it so I'm better off not knowing".

 

Did it do this all day and not blow up?  Then you're good.  a 1.8 Miata motor will not last long with oil pressure that drops out.  FWIW, they will run about 8-10 seconds at full song with no oil pressure.  

 

 

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So 48psi vs 52psi? 

 

What sensor? If using the typical 5v 150psi / 10 Bar sensor:
 

48psi = 0.5+(48/150)*4 = 1.78v 

52psi = 0.5+(52/150)*4 = 1.88v

 

A difference of 0.10v, not a lot. Higher draw from injectors/coils could create a voltage drop over a ground wire.  

Edited by turbogrill
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7 hours ago, Team Infiniti said:

Is this something new with no other changes?

No, it has happened at the 2 race weekends the car has been run at. Miatas are new to me. Sounds like the general consensus is I am over thinking it.

 

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Just to add a thought to this we raced a 1.6 for about three years and always ran Valvoline 10-30 or 10-40 racing oil. May make no difference to your thinking but never had issues with oil pressure. In three years of hard racing only lost one motor which was my fault but it was spectacular, as we were about to cross the finish line on the home straight at NCM rod four let go and provided a great smoke show. We even got a standing ovation. Seems the wrench missed the correct torque on the rod caps when doing bearings.

Edited by 55mini
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56 minutes ago, turbogrill said:

In my thinking the only thing that can destroy a Miata engine is external factors such has slipped belt, broken radiator, loose oil plug, etc. How much damage can 80hp really do :)

You forgot self inflicted issues.  We also broke a valve once, too many money shifts so I guess its the same issue really. And for the record

we had 118 to the wheels 🙂

 

Edited by 55mini
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If its an electronic gauge I would think it could just be minor variance in the signal due to other things happening at those two moments.  If its a mechanical gauge then start with questions like is the oil level too high?  Too much oil can cause the crank to whip up the oil.

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