I frequently see my MIVEC functioning with what I believe to look like Hysteresis error. Especially my Intake, exhaust not as much... it seems on the exhaust side it simply disobeys my map sometimes. The Intake seems to bounce around the target. See pics. Is this normal?

 

That intake "ringing" does look strange. I haven't seen that in my logs, or others to date.

The exhaust MIVEC disobedience, sure. It often struggles to meet the target. Pretty normal, that one.

I am intrigued by the intake behaviour. Mechanical issue?

Edit: An additional thought: The apparent InVVT inaccuracy is +/- 3 degrees or so. The InVVT target itself is only 15 degrees, which is not typical tuning. At that level, +/-3 degrees is 20% variance. I wonder what it would look like if InVVT were up in the 30-degree area... whether it would act like this, or look as pronounced on the logs.

 

Thank you! My mivec tables are an even more conservative form of stock because even with stock and my S1 cams I would get too much overlap and the car would buck and backfire in high gear and low load. Very good point though, I'll try increasing it and see how it behaves relative to target. Maybe my solenoid got overheated.

 

that can be tuned out and still use aggressive cam angles

 

Thanks, can you please elaborate? I'm quite proficient in tuning but not sure how to do what you suggest. I've smoothed all transitions but I still see this error.

 

Just caught it on a log while my car backfired. The max I have on my map is 25 degrees of intake advance but you can see here it overshot to 35 and caused a loss in power and backfire during spoolup.

 

How long have you had the cams?
Who tuned the car?
MIVEC being that low doesn't look right, it could be more aggressive that that.

Do you have any CELs?
Are you sure your cams were installed correctly and the chain was put back on properly?

 

I purchased the car a couple months ago and it had the cams in it. The car was tuned by Topspeed in Georgia but I've since tuned it because driveability wasn't good.
Edit: I've been tuning 8s and a few 9s for many years now but now that I've purchased a X to add to the stable the fully adjustable Mivec bit is interesting.

No I can't be sure the cams were installed correctly... all of the work was done by the shop, not myself. I'd think that if the cam was off by a tooth then I'd see an offset type error where my cam is consistently skewed from the intended angle by, say, 5 degrees. What I'm seeing is more like what you see on a poorly setup boost table where I get overshoot and then increasing correction. Almost like ther's a "base cam angle position" table and an "angle error correction" table.

With regard to your comment that "Mivec that low doesn't look right" :

• In my first post I was using a version of the stock Mivec map where I actually decreased the maximum intake advance to be less than stock to help the backfiring. It did help. I've since edged the intake advance back up towards where it should be (25 at max) and I'm experiencing backfiring again.
• In my most recent post I show where the map said for my intake to go to 25 degrees advance but it instead jumped to 35 degrees and the car backfired. You can see that it over corrected and dropped below target and then at the end it starts coming back up. Sporadically my car will hesitate and backfire during spool and I have suspected it's because of this event. The intake advance overshoots and causes too much overlap thereby killing the cycle and causing the hiccup and backfiring.

I have a CEL that comes on now and again but I don't think it's related. It keeps saying my O2 sensor has slow response (even though I've replaced it).

Can someone post logs showing target and actual cam timing for intake and exhaust? I'd like to see the behavior of others'.

 

I'll log mine today and post it up here for you.

 

Thank you, please do. I just pulled the plug on what I think is the intake mivec solenoid and did some logging g. Anyone know where in the manual it talks about how to test it? I can't find it!

 

Sorry, I've been very busy lately.
I'll try to get a log either tonight or tomorrow.

The intake MIVEC solenoid is on the front corner of the engine underneath the UICP.

The service manual tells you how to test the sensor starting in section 13A on page 377.
Service Manual Here

 

Yesterday I took this log and was very troubled by the intake mivec behavior. I pulled the plug on the solenoid and you can see that at the end the intake side flatlined, as expected (though not at the value I'd have expected).



Today I took this log and it's less troublesome but zoomed in you can see that the exhaust side looks semi-normal... I think - but the intake looks wrong. Thoughts?

 

There have to be a lot of logs out there that show Mivec but I can't find them. Here's another log from today. See the intake mivec missing and overshooting. Then I put it in 3rd gear at low speed low rpm and pushed the pedal down and it backfired like crazy as you can see by knock. I think i'm getting crazy overlap.

 

Just did some experimenting and added a lot more timing in my trouble area... And voila! Its not perfect yet but no backfiring. Looks like with all the overlap it needs to ignite early.

 

Okay so timing helped a bunch in that I no longer backfire but still this seems very odd with my intake mivec... It seems to be having a very hard time tracking with my target. You can see it in both my pulls and in cruising. It seems to saw up and down with error as high as 10+ degrees... How am I supposed to nail down my tune with the intake timing swinging by as much as 50%? Any thoughts? Below is a shot of a log from earlier today as well as the log itself.

Bryan, Hollywood, BakaUnchi, JohnBradley, someone? Help?