VVT goes off for 1 second accelerating in 6th

[tomm.brz]

Guy I know had a problem during the remap with a british remote master tuner, that couldn t fix the problem
he was also using racerom 9.1 and didnt have the "vvt enabled" voice to log
With racerom 10 I put in the problem is still there (tune in the log is just started from scratch, MAF still not scaled well, but fixed by racerom v10 closed loop fuel control)
Can't say if it happens with a stock rom, we didn t tray and would also be annoying cause he has catless header and a strange AEM air intake

https://datazap.me/u/tommbrz/vvt-dis...&mark=783-1113

So he is in 6th gear and accelerates, and for 1 second VVT goes off
intake and exhaust cams flat to 0 and seems to go in the ignition timing VVt off map (what would be Base timing A in romraider)
injections seems to be good as they still inject without esitations
also throttle seems ok from the log, no change in throttle angle during the "defect"

then VVT just restarts and cams go quickly to where they should be
It seems to happen always only in 6th gear and between 4500 and 5000 rpm

no DTCs

car is my13 NA ,has oil cooler and 10w50 oil (his choice)
but he has 10w50 since always and only got the problem lately

calId is ZA1JA02G, i sent him an identical tune but A01G, hoping in some ecutek bug, but hasn t tried yet


What could be the problem?

[steve99]

First thing i would try is using stock intake ibstead of the AEM intake, those intakes are terrible.


Also dont use the extansion cable box for the maf its got some electronics in it that tries to fool ecu by altering maf sensor input signals, it just causes more issues.

[tomm.brz]

ETI module of aem intake is already out.

i doesn t look a problem with the maf to me.. also with the maf scaled by the master tuner, the car did run good for many releases
then suddenly got this problem, only in 6th
CL fuel control is enabled and maf in that log is off of about 11% in that open loop zone, but the cl fuel control corrects it well

could be the oil too thick causing problems?

[steve99]

Its possible the vvt turning off is the ecu going into limp mode.
Its possible tge ecu is not getting a signal it exoects from a sensor, possibly cam sensor or even maf, or another sensor that would cause limp mode.


Strange its not setting any cel codes.




Id try loading stock tune just with P0420 disabled for header


You need to go through a process of elimination


Check any connections that may have been disturbed


Look for strange sensor inputs like weird afr or cam positions , or map sensor.


Check knock if iam gets below certian value it could trigger limp mode



Check DI computer box is mounted via all bolts


If you have spare ecu try replacing that


If you have access to techstream use that for looking at cel codes, it reads storred or transient codes, not just current codes like a lit of code scanbers


Remove as many mods as you can easily and revert to stock tune with no racerom features or changes

[Kodename47]

Are you logging both banks and both commanded and output values?

Oil pressure could be a cause but then I would expect the same in other gears.

Testing an A01G would be a good shout, as I've said previously I stopped using A02G as I found issues that reverting back cleared.

[tomm.brz]

a01g did same thing, only in 6th and more than 140 km/h
with stock map, it doesnt do it

if i use my tune, or tune from the master tuner but change cam timing more similar to UEL it does just very briefly, at higher rpm and speed, sometimes doesnt even do it
ETI module never used in these test

i logged all i could for VVT, bank 1 goes exactly like the target, bank 2 is a bit slower responding after 4800 rpm

no CEL

he also has greddy big snorkel, i m trying to let him do a test without the cover of the AEM airbox, to exclude maybe pression of the air that enters?

[Tor]

Do both cams otherwise reach the values in the AVCS low detonation tables (except where it VVT if off)? E.g. are you asking the intake cam for 40 deg but it only reaches 38.xx?

[tomm.brz]

1 bank reaches 39 and the other 40, with 40 of target
but that i often see specially with EL header and standard ots v2 EL stage2 cam timings
the cams seem to follow target pretty well (bank2 just a bit slower in lowering timings at high rpm)
i ll post some new logs later

next try are again lower cam both intake and exhaust around 4500-5000rpm, and open the AEM box in the top

i dont think it s a limp mode, i thought limp mode would throw CEL and some lights in the dash, it only seems like VVT goes dead for a second

[steve99]

If you say it ok on stock tune


Try just inserting the intake and exhaust cam tavles in the stock tune and then see if that causes issue

[Tor]

Originally Posted by tomm.brz

1 bank reaches 39 and the other 40, with 40 of target
but that i often see specially with EL header and standard ots v2 EL stage2 cam timings
the cams seem to follow target pretty well (bank2 just a bit slower in lowering timings at high rpm)
i ll post some new logs later

Try lowering the intake cam to 38 deg as a max all over. It's speculation, but maybe it tries to drive the cam to 40, but as it can't, it reaches some kind of physical stop and "give up". I don't think these sensors are really accurate. Some cars will reach 40 others won't.

[tomm.brz]

tests were a bit problematic
first he tried my latest working map but without AEM top cover, car pulled strong but maf scaling was pretty of specially around idle and low load, then again in 6th around 4500rpm accelerating vvt went off to 0 briefly

aem top cover put on again so maf scaling was again ok
sent him an identical tune but with stock cam timings

he said vvt was staying off all the time, "vvt enabled" went never to 1
he flashed back the tune with EL cam timings that worked untill 10 minutes before, but
vvt again never went on

seems strange to me, almost as he didnt wait enough but it was actually taking longer than usual as I was checking proecu all the time through him

he flashed back the master tuner's tune (that has racerom v9.1 , mine has racerom v10)
after a while cams started to move so vvt went on

so plan is: he will flash again my tune with stock cam timings hoping vvt will go on and try if the problem in 6th gear is gone with stock cam timings

The mishimoto oil cooler is keeping his 5w50 Mobil1 oil at less than 88 Celsius all the time so he also wants to try chsnge oil to a 5w30 soon

[Tor]

I don't think there is a reason to use the stock tables. I will almost guarantee that all you have to do is lower the cam to 38 or 39. But not just where the problem is. Use it as a max in the whole table.

The cam is controlled by a PID controller. I think this is integral windup and the controller giving up after a set time, which may be why you see it only in 6th gear as the pull last a long time.

https://en.wikipedia.org/wiki/Integral_windup

[tomm.brz]

Tor, thank you, that fixed the problem immediatly
i putna max of 38 and car is still pulling strong, and the vvt dip in 6th gear is gone

[steve99]

Yes the suggestion to ise srock cam mapping was just to test if that was problem, looks like you foumd the issue


Good work