Oil pressure increasing while in boost, drops after throttle lift
#2
Boost Pope
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Neither.
Boost leaking past the rings would not increase oil pressure measurably. The interior of the crankcase is reasonably well ventilated.
And it's not normal, either. Oil pressure tracks RPM, not load.
How bad is the detonation you're experiencing?
Boost leaking past the rings would not increase oil pressure measurably. The interior of the crankcase is reasonably well ventilated.
And it's not normal, either. Oil pressure tracks RPM, not load.
How bad is the detonation you're experiencing?
#6
Retired Mech Design Engr
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Joe asks about detonation because it is a known phenomenon that detonation can cause real gauges to fluctuate. He is giving you a nice hint, listen to him.
Oil pressure fluctuating during boost. [Archive] - MX-5 Miata Forum
Oil pressure fluctuating during boost. [Archive] - MX-5 Miata Forum
#11
Yeah tach doesn't work anyway, need to get that resistor installed. It just seems like it's related since, when I lift off throttle the oil pressure drops after about a second by 10-15 psi, while still in gear. Will have to get an aftermarket gauge just to verify I'm not chasing a bad sender
#12
Boost Pope
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In short: the thing you are describing (with RPM constant, oil pressure goes up and down by a large amount according to throttle) is impossible. I don't mean "impossible" in the sense of "wow, that's really improbable," I mean there's actually no chance at all of it actually happening.
So the question becomes why your gauge is telling you that it is.
#13
In short: the thing you are describing (with RPM constant, oil pressure goes up and down by a large amount according to throttle) is impossible. I don't mean "impossible" in the sense of "wow, that's really improbable," I mean there's actually no chance at all of it actually happening.
- Oil level is low enough that at WOT the weight transfer starts to starve the pickup.
- Some kind of crazy resonance between engine vibrations and the pressure relief valve.
- Throttle-based control of VVT cam with VVT actuator mechanism that's mechanically damaged such that it represents much lower resistance to flow in some positions than others.
I'm not actually proposing any of these in this case, just taking issue with the word "impossible". I agree it's more likely to be an instrumentation error.
--Ian
#14
Boost Pope
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I can think of a few wildly improbable but theoretically possible causes.
- Oil level is low enough that at WOT the weight transfer starts to starve the pickup.
- Some kind of crazy resonance between engine vibrations and the pressure relief valve.
- Throttle-based control of VVT cam with VVT actuator mechanism that's mechanically damaged such that it represents much lower resistance to flow in some positions than others.
- Oil level is low enough that at WOT the weight transfer starts to starve the pickup.
- Some kind of crazy resonance between engine vibrations and the pressure relief valve.
- Throttle-based control of VVT cam with VVT actuator mechanism that's mechanically damaged such that it represents much lower resistance to flow in some positions than others.
And the OP doesn't have VVT.
I'll agree that it's possible the ghost of John Muir may be reaching down and pressing on the oil control plunger a bit when the driver is at WOT, however this seems improbable.
#15
My oil pressure sender was doing something similar when it was fucked. I thought it was like the engine movement tugging on a wire changing the resistance, but instead I determined the oil pressure sender was fucked by using the multi meter. I only really noticed it when I was doing practise starts at prosolo nationals and noticed I had zero oil pressure till like 3k rpms or full throttle but no bad noises or holes in the block.