Do some ECUs adjust for oil pressure?

[SiRDOHC]

I searched this site and everywhere else all I could find were some scion frs/86/brz guys talking about this phenomenon I have experienced when using heavier weights but here goes with a bit of background…

I’ve been driving smaller 4 cylinder cars since the 90’s and I have come to know what kind of power to expect based on the vehicle’s power to weight ratio and gearing.

Most of these cars were 80’s 90’s early 00’s without electronic throttle so what your right foot put into the equation was exactly what you got out of the engine power wise. My most recent vehicle I have owned for 8years now, a ‘13 mazda2 5spd. Older engine design retrofitted to drive by wire at some point , I would assume for emissions purposes. Up until this summer I was a good boy and followed the OM and used 0w20, except for the time I tried m1 0w30 afe. Mileage has been good, but not stellar for a small car with a manual. The engine is low mileage and in good overall health except the thing would just not rev and breathe and give me everything it had in it when I put my foot into it, especially around downshifts and upshifts.

Sump holds 4L, and I had 3L of PP Euro LX 0w30 leftover from another car and went out and bought a 1L of M1 0w40 euro and dumped it in for this year’s oil change. I wish I had tried this sooner because it has drastically reduced rev hang and improved throttle response, in any gear, at any speed, the car now accelerates as a 2300lb vehicle should. If I can keep my foot out of it mileage hasn’t really changed. If I am driving spiritedly the mileage is down, because more fuel is being burned with the additional air that is being let in. Smiles per gallon have gone up

My question to everyone is have you experienced this with any other makes, models? I can only assume its an on the fly adjustment the ECU makes based on oil pressure which is now considerably higher with the heavier weight, euro oils.

 

[Jetronic]

most engines have no idea what the oil pressure is and don't care.

there must be an oil pressure sensor there, not just an oil pressure switch before it's even possible. But those engines that do need oil pressure will constantly monitor it because it's not a static thing anyway. it changes by oil weight, oil degradation (up or down), temperature, revs and speed.

 

[Jetronic]

of forgot to add, even if they would ajust for oil pressure, they adjust the wrong way... more oil pressure on a low viscosity means faster filling of chambers (I assume these are VVT engines you are referring too), but higher oil pressure on a higher viscosity means relatively less fast filling.

They would be monitoring the reaction times of the VVT IMO, much more useful.

 

[eljefino]

My old saturn ran differently on different oil but it's not what you think.

The piston rings were shot. If I coasted down a hill in gear then hit the gas at the bottom, it would suck all sorts of oil up past the rings during fuel cut off then try to burn gas and oil when I nailed the gas at the bottom.

Oil has very low octane when it burns. This lead to knock retard and less power. That car "remembered" knock retard for a couple hundred miles for a given combo of load and RPM, so I could feel various flat spots.

If I ran thicker oil (it loved 15w40) it did this less and ran better in day-to-day driving. Might have been slower reaching redline but it was smoother doing so and therefore more satisfying.

Eventually I changed the rings and the car ran well, all of the time.

 

[Slow Car Sport Mode]

A lot of cars like VTEC, Nissan DOHC engines, their VVT systems (VTEC on a Honda, anyone?) are operated based off oil pressure so it certainly does matter.

Now, you're asking if an engine CPU can make adjustments based on a reading off an OPSU.. that, I don't know, seems unlikely to me though cars ARE becoming more sophisticated. Your engine acting differently based on a more viscous oil tells me maybe something has changed, that as @eljefino mentioned maybe the oil rings were showing their age and probably would have done so on any thicker HTHS within the grade oil, M1 0W-40 is a thin 40 and much loved.

I am not a tribologist but I do read and get educated from here, knowledge bank grows every day.

 

[Wrenchturner44]

SI, The oil you are now using may be providing different valve timing changes vs what you experienced previously. Some OEMs have published warnings on using thicker grade oils in cars with VVT engines as you probably already know. Glad your Miles To SMILES rating has increased. Enjoy your new found driver feelings.

 

[SC Maintenance]

Never heard of an engine that uses oil pressure as an input to control. They do use oil pressure to move the cam posiiton in vvt - but it simply provides the hydraulic force and its typically controlled by the ECU to electrically turn the cam phasers on and off - to allow the oil pressure to actually do its thing.

In the old days oil pumps had a simple pressure relief valve based on a spring, when the pressure reached a max point, it released the pressure dumping the excess oil back into the pan. This uses extra power / fuel so some new cars have electrically controlled bypass valves that actually lower the oil pressure under certain conditions to save fuel. For example some new Toyota's do it if the engine calculated load is less than 50%.

Dirty oil can make your VVT sticky, so maybe the new oil cleaned them up or there otherwise responding faster now. Sounds plausible at least.

 

[SiRDOHC]

Why but for the sake of discussion:

1989 Dodge Daytona
1993 Toyota Tercel
1997 Dodge Neon
2002 Toyota Echo
2003 Toyota Corolla
2005 Toyota RAV V6
2010 Subaru Legacy
2011 Volvo XC60
2012 Honda Pilot
2013 Audi S5
2014 Mazda3
2014 Mazda5
2018 Honda Pilot
2019 RX 350
2020 Toyota Tundra
2022 Kia Soul

Nice list with good variety. having driven the Tercel, Neon and Echo you understand the importance of having the few ponies you have actually show up when called upon. You also understand that smaller engines are under greater load to maintain highway speeds than a silky smooth v6, in a vehicle that doesn't really need one. This is the situation I'm faced with on this little 1.5L.

Manual transmission vehicles in the drive by wire era (such as your 1st gen mazda3) have switches to tell to the ECU when and how you are using the clutch so that it can alter the throttle position. Disconnecting one of the switches confuses the ECU and removes lag when applying throttle. In my particular model this improved response in pretty much in all scenarios. This isn't a "feeling", the throttle actually opens WOT when you floor it at any speed and in any gear, where as normally it would reject your throttle input unless you were in a more appropriate gear. Under this mode the car continues to accelerate, rather than puke and die in between shifts. I was running the car this way the last few summers because it is the only way that I could tolerate driving the thing despite the worsened mileage and the bit of oil it would consume. Why in the summer only? If I left it stock the throttle response would worsen as it got hotter to the point where I could slap the accelerator with the clutch down and the engine rpms wouldn't budge. This again is not a "feeling". Where I am from the ambient temperatures range is -28C to +37C.

I changed the oil in late fall last year and re-connected the clutch switch, because my commute was short and the temperatures were low, so throttle response was not of much concern. That fill is still in the sump and it is considerably thicker when heated up than any 0w20 oil that I had run previously. I haven't had to go under the dash to disconnect the switch to have a vehicle that I can tolerate driving once it gets hot out. This is the only variable that has changed since last year unless I suffered an undetected mild stroke in my sleep sometime between last summer and this summer. I am even the same weight I was last year.

Some people are more sensitive to changes in sound, vibration and some people truly can't hear and can't feel ****. Some people don't notice a picture frame hanging on the wall off level by a couple of degrees and to others they notice it instantly and it drives them crazy. There is variance in how people notice things that can be quantitatively measured.

Lets keep this thread on topic please.

 

[SiRDOHC]

A lot of cars like VTEC, Nissan DOHC engines, their VVT systems (VTEC on a Honda, anyone?) are operated based off oil pressure so it certainly does matter.

Now, you're asking if an engine CPU can make adjustments based on a reading off an OPSU.. that, I don't know, seems unlikely to me though cars ARE becoming more sophisticated. Your engine acting differently based on a more viscous oil tells me maybe something has changed, that as @eljefino mentioned maybe the oil rings were showing their age and probably would have done so on any thicker HTHS within the grade oil, M1 0W-40 is a thin 40 and much loved.

I am not a tribologist but I do read and get educated from here, knowledge bank grows every day.

I have had the car since 9000kms and it has had the now nearly gone throttle lag since day one on 0w20.

 

[SiRDOHC]

This is all I could find on my particular engine.

 

[PWMDMD]

This is all I could find on my particular engine.
View attachment 113475

Think about this scenario. Every time you start your vehicle with a cold engine (even on an 80F day) the oil is orders of magnitude more viscous than at operating temp. The engine and all of its components must have some way of adjusting for this increased viscosity until the engine oil is at operating temp. The difference between cold/cool 0W20 and hot 0W20 or 0W30 or 0W40 is very significant but no one talks about their cars feeling supercharged during warm-up only to have it disappear at operating temp. Engines must be designed to be able to adjust for a wide range of viscosities during operation.

 

[OVERKILL]

Think about this scenario. Every time you start your vehicle with a cold engine (even on an 80F day) the oil is orders of magnitude more viscous than at operating temp. The engine and all of its components must have some way of adjusting for this increased viscosity until the engine oil is at operating temp. The difference between cold/cool 0W20 and hot 0W20 or 0W30 or 0W40 is very significant but no one talks about their cars feeling supercharged during warm-up only to have it disappear at operating temp. Engines must be designed to be able to adjust for a wide range of viscosities during operation.

Yup.

If we entertain this for a minute, and say that this could be verified, the only thing I can think of would be the FM chemistry of the Euro lubes is better and this has slightly reduced the lag of the VCT system's ability to change the cam angle. But that's a long shot.

 

[Slow Car Sport Mode]

I have had the car since 9000kms and it has had the now nearly gone throttle lag since day one on 0w20.

Well, you have a Toyobaru FRS/86/BRZ (Scion. LMAO!) I always glanced at these, always caught my eye.

I was involved with production of Siennas and Highlanders. Yours was made somewhere else.

Your Toyobaru likely came with the 0W-20.. somewhat surprised, other engines are FFed with 0W-16.

Maybe you gave your oil pressure the boost it needed to really be GREAT!

I now yield the floor... resisting every urge to totally post about your 86 and other related things to that

 

[SiRDOHC]

I am all for trying to verify this. I suppose even if I changed the oil back to a 0w20 i used in the past Pp0w20 or tgmo 0w20 canadia edition, the FM would still be present for a while and would take a few changes to flush it out.

Well, you have a Toyobaru FRS/86/BRZ (Scion. LMAO!) I always glanced at these, always caught my eye.

I was involved with production of Siennas and Highlanders. Yours was made somewhere else.

Your Toyobaru likely came with the 0W-20.. somewhat surprised, other engines are FFed with 0W-16.

Maybe you gave your oil pressure the boost it needed to really be GREAT!

I now yield the floor... resisting every urge to totally post about your 86 and other related things to that

I don’t own a Toyobaru. I mentioned that the only other mention of Ecus cutting power based on viscosity was on a FRS/brz board.

 

[Slow Car Sport Mode]

I am all for trying to verify this. I suppose even if I changed the oil the FM

I don’t own a Toyobaru. I mentioned that the only other mention of Ecus cutting power based on viscosity was on a FRS/brz board.

Ohhh... I see it now, you have a 2013 Mazda2. Okay I see it now. It's early. I apologize.

What I'm trying to say and add is.. you have an engine where it's Variable Valve Timing system is operated at least in part by oil pressure, so. While it will obviously work on the oil it comes with, maybe your new mix of mostly PP Euro lube and M1 is pushing it into territory where it is easier to do so.. that, or oil pressure/rings as @eljefino perhaps mentioned.

Of course you're learning that this kind of thing doesn't/shouldn't matter and you are also seeing firsthand how it does.

 

[PimTac]

This is all I could find on my particular engine.
View attachment 113475

Is this the SkyActiv or the Z engine?

 

[SiRDOHC]

Is this the SkyActiv or the Z engine?

Mzr engine. dates back to 2001, used to have a cable actuated throttle body although the 1.5L was only in north america in 2011-2014 with a drive by wire system.

 

[SC Maintenance]

This is all I could find on my particular engine.
View attachment 113475

So I think the key phrase in here is "according to the PCM Signal". So again the engine control computer is deciding what the cam advance position should be, it sends a signal so the hydraulic pressure from the oil pump can move the cams, and then I assume this engine also has cam sensors which will verify back to the PCM the actual cam position. So the viscosity doesn't matter because the PCM will continue driving the cams to the position it wants until the cam sensors say its there.

If it never gets to position you will get an error code - so the oil pressure will affect it from that standpoint. Also the wrong viscosity might slow response of the actual positioners, which I suppose could also make it feel slugish.

At least that is the way any I have worked on operate , but I am a shade tree mechanic and my sample size is very small, so I am certainly not any kind of authority on the matter.

 

[KrisZ]

It is pretty much an almost 100% guarantee that there is no open loop type feedback between the oil pressure sensor and the ECM. Perhaps if we were talking some high end model, then maybe and even then it would be highly unlikely. But Mazda 2, no way.

As mentioned above, perhaps the slightly thicker oil actuated the cams a little bit faster, that is certainly a possibility. In a drive by wire system, that could result in better throttle response I guess.

 

[SiRDOHC]

So I think the key phrase in here is "according to the PCM Signal". So again the engine control computer is deciding what the cam advance position should be, it sends a signal so the hydraulic pressure from the oil pump can move the cams, and then I assume this engine also has cam sensors which will verify back to the PCM the actual cam position. So the viscosity doesn't matter because the PCM will continue driving the cams to the position it wants until the cam sensors say its there.

If it never gets to position you will get an error code - so the oil pressure will affect it from that standpoint. Also the wrong viscosity might slow response of the actual positioners, which I suppose could also make it feel slugish.

At least that is the way any I have worked on operate , but I am a shade tree mechanic and my sample size is very small, so I am certainly not any kind of authority on the matter.

I appreciate your putting some thoughts into this, as I will be the first one to admit this stuff is over my head, and I would probably need a really clear explanation in an animated video, or to have it explained to me with a torn down engine right in front of my face to have a clear picture of what is going on. The Ford Duratec engine design is very similar (shared design) so perhaps I can gain some insight by looking into those engine designs too.

As far as what would be the wrong viscosity goes for this engine, anything from 0w20 to 10w40 is recommended (globally) so your guess is as good as mine as to what the optimal viscosity is. It was only used in a relatively low volume vehicle in the USA/Canada for 4 short years in the beginning of the 0w20 goes in everything but high performance vehicle era.

Before I go further down this rabbit hole I need to verify that the swirl flaps in the intake runner are not jammed open because I will feel like a fool if that is the cause of the significant improvement in throttle response and power I am experiencing. I will do so and report back. If they are not I need to get to the bottom of why the throttle is so responsive and why the annoying flat spots in the factory tune have disappeared. I just finished 600 mile Highway trip and the vehicle IS NOT the same vehicle I bought and drove for the last 8yrs.

If I was fully convinced myself it was the thicker oil I wouldn't be posting this as a question here.

I am here on this forum to learn from the knowledge that others have while also sharing my findings.