2015 Scat Pack Magnuson Supercharged Throttle ocillation

[i tried]

So we have a 2015 scat pack with just under 5psi. During mid throttle acceleration it is ocilllating the throttle blade and we can not figure out why. Attached is the calibration and a log file showing the issue. Any input would be appreciated. Thanks

[Hemituna]

Start by turning off the baro learn and baro fine tune on any boosted tune.
Also be aware that VE table changes won't apply while NN is still turned on.
Good idea to rescale ign tables to include boost also.

These wont fix the surging however, that is another issue.

The surging at part throttle is because the airflow modelling only 'allows' a certain amount of airflow at part throttle.
(unlike at WOT)
So as an example, lets say at 2500rpm the model for 6.4 is say 100 g/s
If you set ETC to open TB to 150g/s at say 50% pedal, it will open TB to 150g/s , then airflow calc will read too high and so will close to 100g/s. Then ETC will see TB has closed and will try open it again, airflow will then be too high, so will be closed again, repeat, repeat.
Add in the blower bypass valve that doesn't appreciate the TB moving all the time, and there is your oscillation....
Couple of ways to fix it.
Usual way tuners go is to add airflow to Desired and TB tables. This has the effect of slowing the opening of the TB per pedal %
so less airflow, so less correction, less surging. Make the numbers big enough to slow the opening of TB to keep airflow model happy and surge is gone.
But, the pedal then feels lazier and lazier the further you increase the airflow no's so now the engine is gutless until the pedal finally reaches WOT threshold and then you get WOT all of a sudden along with the cam advancing 10 degs (that's another story)..... so yay, now you have a S/C 6.4L engine that is gutless at PT yet goes nuts when you step on it hard!....bahhh....that's all bad!
That is why large part of reason people talk about sudden accel on these especially with a blower.
Also is an explanation as to why jazzing up the ETC tables causes surgy and silly behaviour as the tables fight each other.
So better plan is to leave the ETC tables pretty much stock.
Then alter the Airflow numbers.
Strange it may seem, lowering airflow in the desired and TB tables has the required effect.
The idle and LS areas need to stay pretty much same, but above that you can chop a lot out of the tables.(20-50%)
This has the effect of opening the TB way more, BUT tells the PCM you are moving way less air.
Really improves the TB response to pedal and keeps the airflow policeman happy.
See how you go.


If you want, I can post up a maggie 6.4 tune that has these changes and works.

Oh, and if the Maggie bypass vac actuator has a restrictor in it, remove that sucker.

[i tried]

Thanks for the information. So i took this morning and tried moving some values around and nothing seems to be making this car happy. So yes if youre willing to post up a working file that i can overview and try to learn from that would be fantastic. Again Thanks

[Hemituna]

Try this...

6.4L 8sp with Maggie @ 8lb
Mopar SRT4 Inj
Mopar 2 bar map sensor
85mm TB
170f thermostat
headers & exhaust

[06300CSRT8]

Isnt changing the torque Airflow Factor the best way to get rid of this issue? That actually tells the PCM the expected airflow of the engine itself based on commanded torque. Lowering that number tells the PCM to expect a higher airflow to start with (think of that as the "left side of the equation").

[ElecTech]

Chris @ HPTuners also mentioned that adjusting the TB Flow Factor Minimum will help with those transitions.

[Hemituna]

True, perfect world that may supposedly be the 'correct' way to do it.
BUT, it seems like there are some 'limits' in the airflow model that can intrude.
If the PCM 'sees' lots of extra airflow/torque, it or the tcm can slow things down.
I've tried nearly everything on the late model vvt 8sp stuff and lower overall airflow/torque numbers do seem to allow em to perform better.
The PCM only calcs torque based on the numbers we feed it.
It doesn't actually know how much torque is really being made or what the real airflow is.
I'm happy to be told otherwise, but some airflow limit tables have hard limits that seem to be too low or maybe there are some limit tables we don't have yet that maybe are similar to the 'Desired Airmass' table in the Hellcat..
So keeping airflow numbers lower def seems to help.
Using this approach has made the pedal/TB connection finally feel like a cable rather than a rubber cord.

[2therock]

Oh, and if the Maggie bypass vac actuator has a restrictor in it, remove that sucker.

Please explain about this. Where is the restricter. What are the before and after effects? Thanks

[i tried]

Ok so i have tried moving all of these values and the only thing that seems to change is the rate the throttle opens the surging is not going away at all. Refueling the car and will continue running this thing on dyno in the morning.

[06300CSRT8]

Please explain about this. Where is the restricter. What are the before and after effects? Thanks

Whipple and Magnuson insert what looks sort of like a nitrous pill in the inlet of the bypass valve, where the vacuum line connects. This acts to reduce the "signal" reaching the diaphragm, i.e. less vacuum and less boost, thereby slowing down the close and open rates. All this is intended to help ease the light switch effect of the bypass closing and the car running away in WOT mode. Now that we can tune around this, there is no reason to mechanically limit yourself with a restrictor.

my Whipple would spool like a turbo for 1-2 seconds while the bypass SLOWLY closed, was awful lol

[2therock]

Whipple and Magnuson insert what looks sort of like a nitrous pill in the inlet of the bypass valve, where the vacuum line connects. This acts to reduce the "signal" reaching the diaphragm, i.e. less vacuum and less boost, thereby slowing down the close and open rates. All this is intended to help ease the light switch effect of the bypass closing and the car running away in WOT mode. Now that we can tune around this, there is no reason to mechanically limit yourself with a restrictor.

my Whipple would spool like a turbo for 1-2 seconds while the bypass SLOWLY closed, was awful lol

Thanks, I have a Maggie on a 2005 Silverado is why I asked. I get in to small amounts of boost too soon sometimes but not intolerable.

[Hemituna]

Did you copy the entire tune? or just the airflow table changes??
Unless you have a mech issue which with a good install and if hosed up correctly is unlikely, something in the tune must be upsetting it, u just have to figure what.
All tables are important, try changing them all especially the ETC tables as I noticed your Pedal request flywheel power settings are rather aggressive for a blower.
Use that tune file as a reference as it has rescued plenty of guys having similar issues.
If after changing everything around in the tune its still no good, I have something else you can look for.

Ok so i have tried moving all of these values and the only thing that seems to change is the rate the throttle opens the surging is not going away at all. Refueling the car and will continue running this thing on dyno in the morning.

[2therock]

Have you tried contacting Magnuson support? They run these things in testing before releasing for specific vehicles and perhaps they have seen this. they have been known to go over tunes if you send it to them.

[Hemituna]

Whipple and Magnuson insert what looks sort of like a nitrous pill in the inlet of the bypass valve, where the vacuum line connects. This acts to reduce the "signal" reaching the diaphragm, i.e. less vacuum and less boost, thereby slowing down the close and open rates. All this is intended to help ease the light switch effect of the bypass closing and the car running away in WOT mode. Now that we can tune around this, there is no reason to mechanically limit yourself with a restrictor.

my Whipple would spool like a turbo for 1-2 seconds while the bypass SLOWLY closed, was awful lol

It is awful and the restrictors are only fitted because most tunes are not that good.
Most tunes can't handle the big increase in airflow so the fix is to just delay the boost...
Why would you want to delay boost???, just get a turbo if that is the case.
I want my blower on at 1000rpm and instantly when I squeeze the gas!!

Tuning it to be smooth and progressive is where the skill is

[i tried]

I only copied the airflow and throttle tables. But i wonder if everything would match up since our injector and ve tables are different.

So here is an update. Made some tune changes and it seems to be much better but not quite there yet. Made a log on the street and can barely feel it in the car but yet still there. Maybe take a look and hope we can get a new direction. How frustrating.. What i also find very interesting is the frequency of the occillation of the map sensor reading is much higher than what the throttle shows. pretty weird. Seems to only do this from 105-125kpa mid throttle.