You're not going to tell us what was wrong with the vvt are you?

Honestly, I can't point to any one thing! I rechecked the connections, made sure the wiring was good where the CEL output was changed in the harness, and redid the settings on the tune. Added a dial for vvt and the idle duty was changing so I called it a win. Earlier, the car wouldn't even start with vvt enabled so it was hard to troubleshoot.

Like Brain said, alternator is wired to vvt on the nb1 ms3x on his builds. It kept reverting for some reason and finally took to the change in output this time.

How convenient! I wish my car demons would just fix themselves

winner of the week

new title owes me a mouthfull of lunch, cuz mines on my computer screen now.

Haven't updated in a bit, but I've been plugging along. Few things:

-One of the oil leaks I had was the dipstick tube. Fixed that, but I still have a leak somewhere so going to work on finding that this weekend. Got an oem o-ring for the dipstick tube just to make damn sure that's not the issue.
-Idle was all over the place. Rechecked timing and it was off a few degrees. Fixing that, working on CL idle, and figuring out the steps for the valve helped things. I still idle a bit high (about 1k), but it's a lot more stable and now I can dial in closed loop a bit better which is nice.
-Power is not at all what I'd expect and I'm trying to figure out why... I'm down atleast 50hp from where I'd expect to be at 10psi on a 2871, so I'm a bit at a loss. I've checked timing, afr's and duty are fine, and nothing seems totally out of whack. Going to recheck for boost leaks next to make sure that's not the issue, but I feel like it would be pretty obvious to find a boost leak that was eating that much power. I don't have any weird smells or smoke out the exhaust, so that's nice.

In any event... still alive... still tinkering...

Open to any ideas if folks have some. I'll post a log and tune when I get back on my tuning laptop tomorrow. I don't think the power 'loss' is a tune issue though.

Posting tune and log.

This is 10 psi on a 2871 with a tune that's not exactly conservative.

https://cimg5.ibsrv.net/gimg/www.mia...93ecd14d96.jpg


I'm trying to figure out what the heck is going on. Psyber was giving me shit because it doesn't really make sense to compare to expected numbers, but I was making more power on my old setup on the 7psi ewg spring.

-Checked timing already and corrected that.
-Checking for boost leaks. I don't exactly see why this would be doing it because megasquirt is seeing 170kpa for MAP.
-Going to confirm that the motor is timed correctly (checking TDC)
-Going to check compression.

Car has been driving pretty well honestly, even when the WG was wired open for a bit. I can go through the steps above, but just looking for some input to see what else may be going on since I'm not sure what next steps would be once the above are done.

Wat du?

that doesnt look right at all. should be MINIMUM 50whp and tq higher.

did you put in the correct car weight, gearing, tire diameter, gear selection etc... info, into virtual dyno?

Yup. Log is attached if you want to run it yourself. I checked it like 3 times.

3.9 rear, 4th gear pull on a 6 speed. I weigh 170 and I had like a ton of stuff in the trunk (lots of exhaust stuff and parts). Changing weight barely does anything though. And my timing was advanced 5 degrees earlier, which was why my idle was total crap. But it's a bit scary to think I was still around this range when i was running 5 degrees more of timing up top...

Also, the 'timing fixed' label means that I used a timing light and fixed the offset, not that I was doing a pull with fixed timing. Just wanted to make sure that was clear!

As for setup:

VVT head, 84mm 8.6:1 supertechs, running 93.

Boost leak, bad turbo, timing belt off a tooth or two, using the wrong spark timing mark for 10 degrees, valve lash wrong, bov not closed in boost, others.

If the BOV wasn't closed in boost wouldn't I see less boost in the manifold referenced gauge/MAP sensor?
Stefanst had pointed out that it's possible that the turbo was being inefficient if there was a leak large enough to force it to overspin in order to have 10 psi get to the manifold. I feel like I'd hear that though.

With my timing light, I was able to adjust the offset on Tuner studio so the marks for T and 10 were illuminated. 949 damper has 2 marks and they were lining up with the TDC and 10 marks here:
https://www.miata.net/garage/timingmarks_closeup.jpg

I checked a few times to make sure it was right, so I'm confident that this isn't the issue. Will check the teeth as well, but car isn't backfiring or acting weird when it's not under boost.

I can't speak to the valve lash, but new felpro valve stem seals were installed along with volvo springs. The member I'd bought the head from said it had been gone over before he installed it and he ran it for a year or two AFAIK. Given folks success running used/junkyard heads, I figured things would be within spec though it's possible that running at 350+ for a while caused things to go out of spec faster. I can't really speak to that though.

I'd be pleasantly surprised if it was something like timing being off a tooth, but I would hope that something like that would have been obvious when driving it around NA.

It would have been great to double check that valve lash when doing springs and seals. Or before installing the head.

If you drop a trans, do you not bother to look at the condition of a clutch?

Hopefully you can pressure check all your couplings and it'd be something easy. Also is vics being controlled, not that that would account for 50hp

I honestly assumed that the shim clearances etc had been done recently, so I didn't worry about it. Noted for the future though.
I built a boost leak tester so I'm going to use that with a friends compressor and soapy water spray etc to see if I can make sense of things. I guess I'm kind of confused as to how a boost leak pre TB would cause power loss if my manifold referenced MAP sensor is seeing 10PSI. I can understand a loss of efficiency, but would that cause a loss in power too?

Good call on checking VICS. I've actually never looked into that because I figured it was set up on brain's MS3X. VVT angle is changing on the log I posted, so I think that's working, but I'll have to hunt for the settings. It's off if it's on Injector E as written here: https://www.miataturbo.net/megasquir...ilt-ms3-84276/

So I can change that and see what it's doing.

It wouldn't account for 50whp IMO. Intake temps would be up and you might lose some power from that, but not to the extent that you're seeing.

Cam timing being off a tooth doesn't cause backfiring or hard starting. The only indicator I've experienced is lack of power. My money is on bad cam timing.

Just got a chance to look at the log. At the end you're jumping in and out of overrun fuel cut. I think you need to adjust your overrun map threshold under engine state settings.

Post the compression numbers you messaged me on FB.

Then do a leakdown and post those results.

Just got home from a friend's garage. We did a compression test, but he didn't feel like his compressor could handle doing a leakdown. Not my garage, not my place to argue.

Compression numbers were:
Cylinder 1: 150
Cylinder 2: 130 (FFFFFFFUUUU)
Cylinder 3: 150
Cylinder 4: 160

So... Cylinder 2.... What are you up to?

I'm checking with a friend locally to see if I can try to do it at his place. From what I've been told (by psyber and others), it shouldn't take much to be able to do a leakdown so hopefully I'll be able to give it a go over the next few days. Shammrock offered to let me come do it at his house, but he's an hour away so hopefully I can find a place to do it closer, otherwise... roadtrip!

At this point, cam timing would be nice, but I don't think that would really explain what's happening here although it could be adding to the issue.

I'm going to cross my fingers and try to get the leakdown done asap.

I hope so!

Thanks, will do. I feel like my car drops through the rev range pretty slowly off throttle as well, so maybe that'll help with that as well.

Not that much worse than mine. My leakdown was shit too. Not nearly bad enough to explain your results IMO.


Down on power with no other significant symptoms and compression numbers that aren't catastrophic. Sounds like timing to me.

I had a resent thread with the same problem. Mine was retarded ignition timing from a bad basemap setting. Cam timing would do the same.

May not account for all the power loss, but certainly isn't helping. My compression/leakdown was:

Cylinder 1 150 - 4%
Cylinder 2 130 - 38%
Cylinder 3 155 - 7%
Cylinder 4 150 - 6%

Felt a bit meh and misfires. But apples and oranges in terms of boost.

Now im not saying his will be the same problem, but on a head he made some changes on, but didn't check lash or inspect seats and guides, maybe there could be some other contribution for funky business.
​​​​

Yup, psyber is right.

I bought a head from Vtechkiller knowing that he'd pushed his stuff pretty hard with his setup which is pretty similar to what I'm running now. I swapped to volvo springs and did the valve stem seals (using felpro), but didn't check the lash or shims etc. Cameron had told me that he had the head worked on before he ran it, guessing maybe 3ish years ago? I figured it would still be in spec so I didn't want to mess with anything. I want to point out that he had zero issues with anything, so I'm not at all faulting him for this at all. Just wanted to be clear about that.

​​​​​​I'll check leakdown and timing as discussed. Would it make sense to redo compression and leakdown if timing is off?

Also, at what point should I let the engine builder know what's going on? I don't know what's protocol for things like this, but feel like it's something I should bring up if leakdown results put this on the rings. I've run 2 oil changes with break in oil and 2 with conventional. The oil has been pretty spotless. Motor has maybe 1-2k miles on it at most.

​​