atihun

For example, I am driving the car in 2nd gear, I take it to redline, no problem. Shift to 3rd and take it to redline no problem. However, if when I take it to 3rd and drive it slower and maybe later get on the gas, the turbo control system stays in Turbo Control Mode. (I believe this is for spooling or using the secondary turbo). The result is slow build of secondary turbo pressure and a loud exhaust note. I also noticed that this eventually goes away if I just stay in the same gear going the same speed after about 10 to 15 seconds.

If when this boggin occours and I push in the clutch and let the rev's drop right below 3000 RPMs, the turbo control system goes into Charge Control Mode and I can immediately resume driving and regain full turbo functionality on both turbos.

Am I missing some setting?

I have always had this issue and I just work around it by either not shifting too high if I am just cruising or when I shift into the next gear I either finish out the gear or shift into the next gear to get right below 3k.

Anything else I can look at?

Thanks,

skotx

The PFC controls transition back to Charge Control mode right around 3000 rpm, as I've seen in my datalogit logs. So if that shift to 3rd doesn't take you below 3k, then yeah, you'll be trying to spool both turbos in a rather low RPM range. The datalogit provides a Low RPM Transition point, and the default for all three TPS %'s (60, 40, 20) is 3000. So it looks like it can be tweaked, but I've never heard the results of anyone trying it.

-Scott

ajmacdon

I've noticed this *exact* behavior with both my stock ECU and my PFC. I was hoping the PFC would magically get rid of this issue but it didn't change at all.

It almost seems like an issue with the whole strategy of turbo control, as if there is no mechanism for switching back to the primary turbo only without building vacuum first.

I think the loud exhaust note is due to running both turbos at an RPM where they are not usually both online (i.e. reduced exhaust restriction at low R's). I wonder if this reduced back pressure anomaly has any affect on AFR's? I'll have to try to duplicate it next time I have a wideband in the car.

I am very interested in any other experiences with this, it is particularly annoying when you blast on to the freeway and then drop to a cruising gear.

Alex

atihun

You would think that since the TPS is at a lower percent when this transition occurs it would quickly switch back to Charge Control Mode (CCN mode) but it seems to take about 10 to 15 seconds for it to go back from TCN mode.

I don't think that the AFR's should be affected because the turbos aren't spooling much nor giving any boost. And once they do, the system sees that and applies the correct fuel map point.

I wonder if we changed the 20% point, which I am assuming is very at the low throttle level to something like 3500-3700 would the system then immediately switch back to CCN mode? How could this have an adverse effect on the entire system? Could this cause problems if once in the higher gear with little throttle you mash the gas?

~Attila~

es

On the Power FC seq turbo control settings be sure to set the low & the high setting close to each other. Try bumping the low setting up to 3500 or so.

atihun

I am assuming that this is only available through the Datalogit as I don't think there is anything else that would correspond to the setting above through the commander.

es

Correct.

CCarlisi

I have had the same problem for a couple years and posted repeatedly on the subject. The system seems to get stuck in secondary mode and won't get out until my revs drop to 2800. If I stay between 2800 and 4000ish I get nothing. This simply may be due to lag. However another possibility is only the CCA and TCA is in secondary mode while the rest of the sequential system is in primary mode.

Normally below the transition point the CRV value is open (on the 2nd turbo side of the Y) and the CCA is closed (isolating the second turbo and that side of the Y) If the CCA is left in 2ndary mode (open) but the CRV is in primary mode boost generated by the primary will flow across the Y and out the CRV. I can see from the commander that the CCA is staying open, but can't monitor the CRV. It would be interesting to see what's it's up to when all this is going on. Either way it sucks. It's one thing in low gears on the street but getting stuck in the dead zone on the highway is especially frustrating.