High load at idle
 

I've been attempting to remote tune a highly modified MSM and am coming across something I don't think I've encountered before, and am wondering if anyone else has. It's warming up nicely but we're still working on warm restarts, as rpm is currently fluctuating like crazy.

My main concern is that it's idling at 60kpa. I've looked over a number of my datalogs from other vehicles and usually see low 30s. Idle valve is in a normal range of ~30%, and the car refuses to idle leaner than ~13.0, which was apparently similar with his Hydra. Am I missing the reason for this?

Yes I have CL idle, idle VE, and a number of other features disabled as we try to work on just warming up and restarting.

.msq and log attached.

Shoot log is too big, I'll get a shorter one soon

Sounds like a vacuum leak? The other time I recently dealt with a high kpa idling car the intake came was off a tooth.

60kpa of vacuum at idle is way too high, something is wrong.

Can't open map at work, but definitely should not idle at 60 unless itb's or big cams. leak(s)?

It does supposedly have big cams. Adjustable exhaust cam was 6* advanced, I had the owner return to zero advance with no change in idle load. I'll have him double check for any vacuum leaks.

When my VVT was fuckity I also had huge MAP values at idle. Looking at the VVT map, you have 8.4 degrees at 60% fuel load. Might want to set all values to -1 until 2000 rpm.

Msm doesn’t have vvt unless its got a head swap

If it still has the MSM head then there is no VVT.

He did say highly modified... Looking at the tune, someone has definitely been playing around with VVT settings.

Sorry, wrote the original post too early. It's an 01

Here's the engine bay, I'm trying to find the description he sent me of the specs, but it's a built engine with a 3071 or something close to that.

which injectors

1000s, I'm assuming IDs.

02 with a 1952cc McCulley engine in it Skunk2 intake, GT3170R FM turbo kit

This is what the car has. (Curly is helping me)
 

02 Miata with a McCulley 1.8 (Bored to 2.0) Manley rods, Skunk2 Intake,
Skunk2 throttle body, Garrett GT3170R turbo with a 3” exhaust out the back. Wideband
sensor and 1000cc injectors

which 1000cc injectors

Large cam muscle cars don't even make enough vacuum to make good use of the power brake booster. It's not unheard-of.

Leaking junk2 intake?

He said he sprayed carb cleaner everywhere without an increase in RPM, I'd be doing a smoke test, but that's out of the typical home mechanic's abilities.

What is the idle RPM? Do throttle changes result in reasonable MAP/RPM changes? Is MAP stable? Unless the ignition timing, cam timing, or something else is totally fubar, I would expect the torque to prevent it from getting down to anything a normal person would call idle.

Continued...

I would start by targeting a stable afr of like 12.5. If the CAM profile really is that aggressive, you are probably getting all sorts of sporatic combustion behavior at 13 or higher. Once you get the AFR/rpm stabilized, you can try leaning it out.

Again...

drop idle timing to 14. This also gives idle advance much more to play with moving forward.

Idle is set to 950 right now. The more I tune it the more I want a 1000+ idle. Along with a 13 or less afr and yes, I'd be willing to try lower ignition too. I'm turning on CL idle in his latest tune to try and keep it from stalling when returning to idle. My own car will return to idle without an idle valve intervention, and can droop as low as ~300rpm without stalling, I really don't think this one will ever do the same.

I've never tried it, is there a way to trim a log down? I have a few of him driving with autotune on and/or idling, but they're both huge logs. This is one of the first times I've seen how it behaves while driving, MAP never reads above 109kpa, but I'm sure he's (hopefully) babying it.

Open it in excel and cut things out. It's just a csv file I believe.

You can trim logs in MLV by using the right click delete before and right click delete after function followed by file-export. You need to copy and paste the header lines from the original log back in with a text editor before you you reopen the log IIRC

edit: get used to it and it takes less than a minute. Awesome for VD!

109kpa is a tough number to hit. Is the WG wired open?

950 is really low for an engine that isn't misfiring or badly timed at 60kpa. I suspect either a badly calibrated/faulty MAP or an average of 2-3 cylinders firing per cycle.

You can also upload the logs to https://mega.nz/. Quick howto:
1) Create an account / log in
2) Drag 'n drop the logs into this screen. Wait while it uploads (could take a minute or two depending on the size).
3) Right click on the log you want to share, press get link and copy paste the link with key url to this forum.

Not presently where I have MLV. There are actually menu functions to do that, and then export. No need to copy headers, they are not lost. I have never done the right click approach.

Play with the menus and you'll find the trim before and trim after items.

Ok thanks. Y'all think I have way more time on my hands than I do!

For now, here are the specs from keegan:


Intake lift .351

Duration 268

Duration @.050 213

Ex lift .360

Duration 247

Duration @ .050 226

The lobe center for the intake is 108 deg and the same for the exhaust.

Nope, this is why I don't do much of this :)

Since my experience with big cams is in muscle cars I will contribute that they must be idled higher then their stock cammed equivalents to generate good vacuum. I would have set the idle that at about 1150 or 1200 RPM was cams of that duration and see if the afr's and the idle doesn't stabilize.

I'll try that, thanks

I'm gonna go ahead and disagree. Last cammed miata I tuned was a 1.6 but had no problem idling sub-1000 with HKS cams (Cam Duration: 256 / Cam Lift: 9 Mm). didn't even have an iacv, and also was running the twin disk that weighs nothing and doesn't help idle at all.

But I guess try it. I just don't think that's a real fix, because even the crappiest setup will idle at 1200.

Smaller cams, OP has 10* more duration and no one knows how much overlap.

I believe that it's the cams. My experience with cammed B series motors says its the cams. Ive been involved with a dozen or more including building tuning and owning one.

Dann

Did disabling the intake cam advance at idle rpms make a difference? Or is VVT not in use?

Ok.
What's your solution?

INJECTOR DYNAMIC EV14 INJECTORS