Hey everyone, I'm running into some issues on my recently finished engine build and I'm hoping to get some ideas as to what the problem could be. I've searched through a ton of the VVT related threads but I haven't found anyone else with this particular problem.

Engine build related details first. I'm at around 750 miles into my full BP6D engine overhaul with ST 8.7 pistons, Weisco rings, Manley Rods, BE Stage 2 pump 0 shims (more on this later). I did not delete the oil squirters. Bearing clerances are all within spec with the rod bearings being on the looser side of the factory range. Outside of this strange issue, the car has been running great at ~10psi. It's 100% street driven. The oil change history post rebuild has been as follows: 2miles/20mins, 50 miles, 250 miles, and 500 miles with T5 15w40. I'm planning to switch to T6 15w40 at 1000 miles. Nothing of suspect from any of the oil changes outside of a little bit of mettalic shean.

Now, the issue - VVT. I was noticing a seemingly random oil pressure osscilation on the OEM oil pressure gauge (NA6 OP sender) when I'm giving her the sauce. It would occur when I'm north of 4k rpm and OP would dip momentarily to ~30 psi and back. it might happen a couple times in a 3rd gear pull. Seeing this I took a look at a datalog and noticed this...


Crazy right? You can see that before it goes wild, vvt angle tracks the target very well up until ~4k RPM. This issue doesn't appear to be load dependent but strictly rpm related. Here is another screen shot showing this.


I'm pretty stuck on what the cause could be to be honest. When in boost, you can feel some of these vvt fluctuations as a momentary dip in power. I never had this issue before the engine rebuild. My NA has been VVT swapped for probably 25-30k miles? 20k of which on the MK Turbo kit. I've tried swapping to another known working OEM vvt solenoid off of my NB2 but I get the same problem. Disabling VVT stops the issue (obviously) and it pulls just fine to redline. I'm really hoping any of you fine folks could help point me in a diagnostic direction here.

ALSO, while investigating the VVT/Oil pressure fluctuation I came to the realization that during the engine rebuild, I never checked the BE S2 pump for the number of shims installed. I bought this pump BNIB from Sixshooter on here back when I was starting the rebuild. He had crossed out the "2 shims" on the paper they sent and replaced with "0." From all the other 1,483,021 things I was focused on during the rebuild, I never confirmed this nor did I confirm the relief valve was functional and not sticking. Sooooo I'm pretty sure my BE S2 pump has 0 shims.

I talked to BE about this and they said it should be fine for a street car as long as OP doesn't drop below 20 by redline. That's,.. comforting? But I trust your guys' opinion way more on this. I'm currently seeing 15-20 psi idle, 40 psi around 3.5k and it'll rise close to 45 psi before dipping to ~35 by redline. These values are all with oil up to temp with the OEM NA6 op guage in the cluster. I really don't like this. This seems to be pretty low, most people that I've read about state around 50-60 psi at red line. I have revlimiter gauge faces, so the OP could be off a little when I went to set the needle many years ago. I'm looking to order a mechanical Autometer guage to verify before I do anything big. I know 0 shims is the factory 60 psi relief pressure and adding shims doesn't increase pressure, just increases the point when the relief valve opens to bypass. Should I look to drop the pan to add 1 or 2 shims and verify the relief isn't stuck open? I'm hoping some of you guys can advise before I go through all of that work. I have a friend with a lift and he'll help me drop the subframe and pan to do this.

I know this is a lot and probably more context than needed. I know we operate better here with too much info than not enough. I'm hoping I hit the word count to summon some of the greybeards. ha! I've attached my current tune and a datalog of a drive from a couple days ago.

Thanks in advance.

 

Not sure if it has anything to do with the issue, but I noticed your fuel injection timing corresponds to the VVT inaccuracies pretty closely as well. I assume the tune you uploaded here is based on the tune you've been running without VVT issues for the past 20K?

I don't have VVT on my car so I'm not familiar with the intricacies there.

 

I appreciate the reply. I could very well be wrong here, but I believe the injector timing is relative to the intake cam position. Therefore, as the intake cam is advanced, the injector timing is shifted along with it. I'm not certain, but that would explain the injector timing matching the erratic vvt angles.

To answer your question though, yes, this tune is the original tune I've used since vvt swapping - with obvious adjustments along the way as my setup changed.

 

That is correct, the injector timing is adjusted relative to the actual cam angle based on the MSQs configuration.

Regarding your oil pressures, if that gauge is accurate I would say it is borderline for VVT actuation at mid-RPM and below the minimum in the manual at high RPM. The manual states a minimum of 45psi above 3k for proper VVT actuation. Definitely verify that with a proper gauge, and if under 45psi investigate further. For reference, I'm running a Stage 2 boundary pump, and I see no lower than 63psi on hot oil at 7k RPM using a Bosch sensor in the stock location.

This one seems confusing to me. It could certainly be an oil pressure issue, but I would expect lack of oil pressure to cause lower than target VVT angles, not higher. But then I also see the duty is increasing in areas it should decrease, and makes me wonder if you've hit some weird bug in the firmware. I wonder what would happen if you change the Load Y Axis from Fuelload to TPS and then adjust that Y axis to match. This is just to rule out an overflow condition in the firmware. I would also suggest you check your VVT feed and make sure that little filter is in place and hasn't spat a piece of plastic into the VVT solenoid. Someone on here had some odd VVT issues that turn out to be that. But definitely verify your oil pressure no matter what.

 

Yeah, that tracks with some of the values I read about. I'd like to take the car back out and take a video of the gauge from a 3rd gear pull, but I'm scared to go much above 5k rpm now. When I noticed the OP sag at red line, it was a 2nd gear pull that I was watching the gauge and things were happening pretty quick. It may be of note that the oil feed to the turbo is taken from the stock OP sender location. So, I have a T fitting there. Could this contribute to lower-than-actual pressure readings? Also, should I bother with a mechanical gauge or just go with electrical sensor+gauge? I'd prefer electrical so I can run it to the MS but I figured a mechanical would be better for a quicker/easier sanity check. I'll do some research on the preferred turbo oil feed and oil pressure sensor fittings/locations/combinations.

Hmm, the firmware is an interesting idea. When I get some time I'll see if I can rule this out. Checking the little vvt feed filter is also a good shout. I may just order a new one to be sure. I dropped mine and lightly stepped on it months ago so it's a little mangled. Typing my goofs out on here is very humbling. lol I appreciate the help on this.

 

Tee-ing off the stock oil pressure sender port shouldn't cause low oil pressure. That's probably the most common place to get an oil feed for the turbo. FWIW I've got a tee there for my oil feed but am hoping to move to a more robust setup this winter.

I have a (stage 3?) boundary pump, no idea on shims. Running T6 15-40 or 5-40 I'll usually see ~24-30 oil pressure at idle putting around town and closer to 18 PSI at idle immediately after a hot autocross run. Hot summer highway cruising at 80 MPH is usually in the low 50s and maybe high 40s if it's really hot out and we're going up some mountain passes. Redline is around 60-70 PSI depending on how hot the oil is.

Not the best way to deep dive on the data, but here's a quick screenshot from an autocross a month ago. You can see the lowest it dips is around 25 PSI on decel and presumably cornering reasonably hard.

 

Thanks for sending over that screen shot. It, uhh, makes me feel even worse lol. I didn't mean that the T fitting would cause lower oil pressure. I meant could it cause an observed lower pressure reading due to some interference from the turbo feed being so close or from the same location? Thus, the oil pressure sensor would be more innaccurate than it arguably already is.

The oil pressure from idle up to cruise rpms of 3-4k rises very quickly with the rpm sweep up until it hits a wall at 40psi and basically flatlines until redline. It may creep up a few psi but then falls back to 38-40psi at redline. Again, this is on the oem OP sender with revlimiter gauge faces which may change the actual readings a little.

At any rate, I was looking into electronic oil pressure + temp sensors to wire into MS to verify the oil pressures I'm seeing. I happened upon this thread. There are a couple of good options discussed here but the Bosch sensor seems like the way to go. I am interested to hear from you @redursidae about your mounting location for the sensor. You mentioned you have it mounted in the stock location but it appears to be a no-go from Bosch as it is outlined in the thread I linked. Have you had any issues with this sensor mounting point? I may place an order, but i'm concerned on the longevity and possible failure point as some others alluded to. I'm interested in any other options for electronic oil pressure sensors if anyone cares to provide them. The oil temp combo is also nice, but by no means a requirement.

I'm hoping to dive into some diagnosing sometime this week when I have time. Again, I really appreciate the conversation here.

 

I like the Bosch sensor in the stock location. The main concern you may see is with vibration, and all I can say is it hasn't been an issue for me, but if you're worried you can remote mount it. Make sure to get a genuine Bosch from a reputable source, because the knock offs leak through the plug. The only issue I had was that I either forgot to tighten it, or didn't do it correctly and found it leaking A LOT before a trackday a few months ago. Gave it a good snug and no issues since. I used a stainless steel 1/8 BSPT male to M10x1.0 female adapter in place of the OEM sender, and have used the same setup for about 2 years. You'll need a pullup for the temperature signal to work on MS3.

Hopefully some of my babbling here helps: https://www.miataturbo.net/build-thr...3/#post1647286

and the adapter is something like this: https://ebay.us/m/igfavE

 

That's super helpful, I appreciate it. I'll likely go with this. If you've had minimal problems with track duty conditions, I'm sure it'll be fine on a street car with split DD duty when the weather plays nice. I'll order up a sensor, get it wired in, and report back with more accurate oil pressure readings/logs.

In the meantime, I'd like to get some more ideas for the cause of the low oil pressure if anyone else would like to chime in. I'm not sure if I mentioned it earlier, but the BE S2 pump was purchased BNIB from Six on here but he purchased it wayyy back in 2019. So it sat on in his garage for awhile. I'm really wondering if the pressure relief could be stuck partially open or something? or if the fact I'm almost certain it has 0 shims could play a part? Maybe over the years of sitting the spring lost some tension and opens at ~40 psi instead of 60? That would maybe explain how OP quickly builds but hits a wall at 40psi from 3500 to redline. I'll go through the work to drop the subframe and oil pan if I have to, but I'd like some confidence this is the issue first. Any thoughts or ideas from the masses?

 

I think getting some actual logged data from a reliable sensor is the best first step, which you’re doing. If it’s confirmed to build pressure fine until ~40psi and then just flatlines, that behavior really seems to me like it’s the bypass opening. If that’s the case, some shims should solve it.

If it were me I’d plan to replace the spring itself as well while you’re in there, just in case BE swapped in some other spring when it was built. I don’t think sitting for a few years would cause the spring rate to drop significantly, but there’s been enough threads about sketchy/poorlymassembled pumps from BE to make me wonder if it’s just not an oem equivalent spring.

 

Yeah, It's looking more and more like I'm pulling that pan and adding a shim or two. Idk how many yet. That's a good shout to replace the spring while I'm there. I'll also check the oil pickup and ensure it's still properly torqued, too. It'll be a few weeks before i can dive into it though.

As for the oil pressure sensor, I did a bunch of reading and decided I really don't need the oil pressure+temp sensor. It's a street car that really doesn't get beat to death. That, and the pricetag for the Bosch sensor is more than I'd like to spend at the moment. I wound up ordering this:

https://www.bmotorsports.com/shop/pr...28ee5h23v5vbh4

I'm also at a bit of a crossroads now. My shiny new kraken mani/dp/exhaust is getting delivered today and I'm really eager to rip out the MK Turbo bits and slap on the kraken + PTX2860 gen 2 on. I know I should wait to solve this OP/VVT issue first. I'm going to try to be a good boy and wait it out.

Anywho, I'll get the sensor wired in once it gets delivered, take some logs, and report back. Thanks again for the help so far guys.

PS: Anyone reading this and is in the market for a full mkturbo kit for a NA8, I'll have mine up for sale soon™. I highly doubt I'm willing to ship but i'll drive up to 1-2 hours outside of Knoxville TN to meet the buyer. It's almost everything you need - manifold, DP, <1k mile turbo, adjustable wastegate, full exhaust, IC and 90% of the IC piping.

 

The OP sensor hasn't came in yet, but I took the car out for a quick drive to get some data and observations.

On cold start the OP gauge quickly pegs up to ~80-90 psi. Below is a quick video of my cold start and OP behavoir.


After letting it warm up a bit I took it for a drive. The idle OP with it fully up to temp sits right at 20 psi @1k rpm. if it's hot out and I'm enjoying boost, it might sit at 15-18. These values at idle seem perfectly fine to me. Oh, btw, these values were taken after my drive when I parked it in the garage.

Now the weirdness begins. I took a video of a partial throttle pull up to ~5800 rpm here's the link to it.


From the video, you can see that OP on the gauge reads 40psi right at 3k rpm and stays there until slowly drifting down to low 30s by 5800 rpm. Why? I don't understand how oil pressure can decrease with rpm when the oil pump is directly driven by the crankshaft rpm. It should only increase right? Unless the relief valve opens I suppose. Also, in the video, when I say it's at 3k rpm, by tach reads 3200 rpm. The 3k was verified with my laptop in the passenger seat. This is another conundrum for another day, but recently my tach doesn't seem to be linear anymore. It'll read 500 when I'm idling at 1000, and apparently 3200 when I'm at 3000. This started sometime after I got it running on the fresh rebuild. I digress.

When I'm actually getting on it, the gauge will wiggle a noticiable (2-4psi)amount but I attribute that to the buzzyness from the SM hybrid mounts and related resonant vibrations through the rev range. I know knock can cause it to fluctuate, but I've taken out 4° out romped on it and it doesn't seem to rid of the wiggles.

Here's a summary of relevant oil pressures:

• Cold start idle ~70-80 psi
• Hot idle ~18-20 psi
• 1800 rpm ~30 psi
• 2800 to 4800ish rpm 40psi then starts to slowly dip downard.

Everything looks good to me up to the 3-4000 rpm range but it just stonewalls at 40psi. I know I'm ahead of getting real OP datalogs, but seeing the oil pressure DECREASE in the upper revs has me very perplexed and concerned.

 

Whoops, I forgot to add the datalog from this drive. Again, OP sensor hasn't came in yet so no hard data yet. The pull from the second video is at the 1300 sec mark in the log. I'd love some ideas on this OP behavoir. The pan will more than likely come off with a new oil pump relief valve spring and 1 or 2 shims going in. It'll be about a month before I can voluntell my buddy to let me use him and his lift. I'm not looking forward to it.

 

Basically for oil pressure to be decreasing with rpm, leakage is exceeding supply. Pressure leakage is gonna be anywhere oils getting pumped to; rod and main bearings, turbo bearing, cam journals, and of course the VVT solenoid. Are you positive the pump you installed is the higher volume VVT pump? During the rebuild did you remove the oil restrictor at the deck that feeds the head/cams? Could an oil squirter(s) have loosened and fallen out? You’re totally 100% confident on all your bearing clearances? Oil pickup tube sealed well to the pump and not cracked anywhere?

Unfortunately there’s a lot of backtracking to do it seems. The fact that it hits 80-90psi cold and then continues falling below 40psi when warm indicates to me that it’s probably not the relief valve. An overly low relief valve would level off hard at 40psi and maybe climb slightly with rpm as the relief valve just can’t divert enough volume above a certain rpm to limit the pressure perfectly at the given pressure set point.


Sorry to be the bearer of bad news. As a quick sanity check you could grab one of the cheap Bosch $20 mechanical gauges just to rule out some sort of electrical interference causing your gauge to read weird.

 

I appreciate the write up and all of the pointers of things to look into. What you said makes complete sense. I'll go through and answer some of the questions you asked.

I verified my BE pump serial number with boundary that it is indeed a S2 pump. I did not remove the oil restrictor that supplys the head. I was able to look back at pictures and I can see the restrictor in place on the block. It's definitely not out of the question that an oil squirter came loose. I put them back in with the proper torque and blue loctite, but who knows. As far as bearing clearances, all were plastigauged with new plastigauge. Rods were checked twice. I forget the exact values, but they were a little on the looser end of the range. Not close to the max .0040" though. I want to say it was .003". Mains were like .0015"-.0020" IIRC. I should've wrote these measurements down for this exact reason. Lesson learned. Oil pickup tube was installed with a new gasket and torqued to spec with blue loctite.

You mentioning the VVT solenoid being a potential pressue leak is interesting since this all started with my whacky vvt angles at the higher RPM. So, that could be a potential link to the issue. I'll admit I'm not sure where to start looking here. The bracket itself is leaking a little bit onto the VC and could use a new gasket, but very doubtfull that's the cause. The front of the engine leaks a small amount and I might see a very small puddle (maybe an inch or two in diameter) develop over a few days on the garage floor. Really nothing major.

Now with the hard truth it's loosing oil pressure at high RPM, I'll likely just pull the motor. Bummer. It'll make inspecting the oil pump easier and I can better inspect stuff with the engine on a stand. at first thought, I'm thinking I would inspect the oil pump relief, the little O ring on the OP, pickup tube, Oil squirters and ??. I'll look into the VVT system first since that won't be as much work. I'll also get OP datalogs first before I tear it out to compare with when it's back together. Thanks again for the help.

 

Edit - I see someone else asked this just above, but I'm not sure it was fully answered.

Hey, I was saw someone list a Boundary pump in the classifieds and realized they mentioned they had to get a specific VVT compatible version of the pump. Sure enough, going to Fab 9's website they have specific VVT versions of the pump listed as well, although they're still a "stage 2" pump. Do you know if your pump is a VVT version? Sounds like it flows more volume than the standard pump.

 

[QUOTE=SimBa;1669847]Edit - I see someone else asked this just above, but I'm not sure it was fully answered.

Hey, I was saw someone list a Boundary pump in the classifieds and realized they mentioned they had to get a specific VVT compatible version of the pump. Sure enough, going to Fab 9's website they have specific VVT versions of the pump listed as well, although they're still a "stage 2" pump. Do you know if your pump is a VVT version? Sounds like it flows more volume than the standard pump.

/QUOTE]

Hmm. I was of the understanding the BE "stage 2" pump was VVT compatible, not that there were different types of "stage 2" pumps, one for vvt and one without.

I gave BE a call asking for clarification on this and they stated that the BES1 pump is for non vvt applications, BES2 pump for VVT applications. They also have a BES3 pump but IIRC, it's a BES2 pump but with a billet backing plate instead of the normal one? Not 100% on the BES3 details but that was it. BES1 non VVT and BES2 for VVT. I mentioned my question stemming from FAB9's listing and they laughed and said "oh, that makes sense. IDK what they're thinking." lol. The person on the phone relayed my OP behavoir (40psi dipping to 30psi by 6k rpm) to their engineer. He said that it sounds like the pump is getting air from the pickup like a crack or a bad seal at the gasket/flange. I'm not discrediting Monkeyman's other suggestions, but that was what the BE engineer's first thoughts were on this behavior.

Seeing a suggestion that the vvt solenoid, mechanism, or housing could be a potential source of my pressure loss has me intrigued to look here before I do anything big like pulling the motor. I have a spare VVT head and I'm thinking of swapping out the VVT intake cam gear/mechanism, solenoid, and even the housing just to rule out VVT being the pressure loss. I'll have to deal with resetting timing, but it's less work than yanking the whole thing out. Since this all started with whacky vvt behavoir north of 4k rpm which is where my pressure dip seems to start, this seems like the best thing to try first. I'm convinced the VVT system behavior is either the cause of the pressure loss or a byproduct of lower oil pressure in the top end.

OP sensor came in the mail yesterday and I'm going to get it wired up and take a datalog this Friday. K, hopefully my next post in here has some answers and isn't me rambling. As always, I appreciate the help guys!

 

So, rereading the original post, obviously we’ve gone off on the tangent of oil pressure and dropped the VVT commanded angle issues. But you mentioned initially that when you disabled the cam control, obviously the cam angle remains consistent to redline, but, what did oil pressure do with cam control disabled?

I know some people have reported problems with the cam phasers themselves but not having a running VVT car I’ve never looked into it. Obviously the solenoid opens/closes to allow pressurized oil into the phaser to advance the cam, when the ECU calls for cam retard where does that oil go? I assume backwards through wherever it came in; are all the O rings on your VVT solenoid in good shape? Although I have a hard time believing the one in the car and the borrowed one from your NB would both have a leakage issue in the same manner. Hmmm, unless there is something amiss with the phaser/solenoid oil “manifold” on the valve cover, maybe the O-ring where it seals into the cam cap is torn/pinched/wasted?

Apologies for the overwhelming amount of suggestions/brain vomit. Just spitballing here. And of course taking the top of the motor apart is much much easier than the bottom end lol, be good if you could avoid that!

 

I agree, the thread has derailed into oil pressure diagnosis. I would adjust the thread title accordingly if I could. But, to answer your first question, yes. The video I posted previously is with VVT disabled. So the oil pressures I "recorded" were without VVT. For VVT solenoid O rings, I don't believe this to be the culprit. Since both solenoids I tried had the same results. Don't apologize for the brain vomit. I really appreciate the ideas.

ALAS! I finally have some oil pressure data to share. I got the OP sensor wired up and installed. I wanted to keep the stock OP sender in place for the gauge cluster. My adapter fitting thingy for my turbo feed has an extra port for this exact purpose, but the way it is oriented will not fit the new sensor. That, and it would be a total PITA to work under the manifold to install it. After doing some digging, I read that you can use an existing port on the VVT housing for oil pressure sensors. All I had to do was take out the 1/8 BSPT plug, find a 1/8BSPT to 1/8 NPT adapter and screw in my new sensor. Voila, OP sensor install done.



I am planning to remote mount this around the fuse box area using 3an lines. The lines and fittings are already on order I just wanted to get some data asap. I entered in the calibration for the sensor with a slight offset as it was reading about 0.5 psi at ambient pressure. Against my better judgement, I didn't wait for the thread sealant to set up before going for a drive. Thus, it leaked of course. I wrapped a paper towel around the sensor and went for it.

Come to find out. The stock NA6 OP sendor is pretty inaccurate when the oil is cold. The stock gauge was reading 70-80 PSI cold at 1k RPM but the OP sensor was reading 50-55 psi. Hmm. I let the car warm up a little while I tried to remedy the small leak at the sensor. I have good and bad news.



I didn't add any smoothing, so the signal is very jittery. It's annoying to look at, I know. I'll fool with the smoothing later. The good news is the oil pressure doesn't seem to be dropping at higher RPMs. The bad news is what we already knew. New OP sensor also shows it stonewalling at around 40-45 psi from 3500 - redline. Well, almost redline. I didn't feel comfrotable redlining it for obvious reasons. Idle pressures with the oil up to temp sits at around 20 psi.

So, I think that sets our sights back to the relief valve/spring/shims? Oil pressure dropping at higher revs makes sense to point to other interal pressure losses, but this doesn't seem to be happening according to the sensor. I didn't test with VVT enabled. I will go for another drive once I go back and make my wiring job more palatable and permenant. I'll get a log with much more smoothing and VVT enabled. It'll be a few days, though, I'm leaving for a camping trip later today.

I would post the log but it barely surpasses the 20mb upload limit. I'll get another one later and post it in here. As always, thanks for the help.