Boost engagement delay after startup

[Dresdie]

On the 3.5 ecoboost/PB, I've noticed the turbos typically do not engage, immediately after startup, when they normally do until after driving a quarter mile or so. Anyone know if this is a standard ECU thing?

Related - Since installing a Roush CAI, I can hear more of the turbos and they are audibly not pushing much boost in this scenario. There are also differences in sound of the throttle body (maybe?). It almost sounds like the throttle opens up more than normal (deeper sound) when accelerating the first time after startup. Then after a while, it doesn't sound as "deep" when accelerating and turbos engage at usual RPMs.

No problems here, just mainly interested in how the ecoboost motor works. Thoughts?

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[TheGoatman]

The go peddle is a torque request. Based on conditions, the ecm will determine the way to deliver it.
in our case, the electric motor provides another powerful option it can consider.

 

[hotrodmex]

Given electrical control of wastegates, I wouldn't be surprised if the motor restricts boost level until the engine warms a bit. Many cars (mostly high performance) are restricted performance until the engine warms.

 

[DT444T]

I've seen what OP is talking about. I was at WOT and the truck would NOT build boost. I have the boost gauge in my cluster. I let all the way off the throttle and hit it again and this time there was boost.

Can't remember the conditions, but it was weird.

 

[TheGoatman]

I've seen what OP is talking about. I was at WOT and the truck would NOT build boost. I have the boost gauge in my cluster. I let all the way off the throttle and hit it again and this time there was boost.

Can't remember the conditions, but it was weird.

Try with traction control off or in awd

 

[Dresdie]

Given electrical control of wastegates, I wouldn't be surprised if the motor restricts boost level until the engine warms a bit. Many cars (mostly high performance) are restricted performance until the engine warms.

This is my current assumption too.

But, this leaves one questioning how the ECU determines its warmed up enough for boost. In my experience, boost is enabled only after the 2nd major pedal depression (after cold start, and even sometimes after motor has been on/idling after cold start).

Hard to imagine a single pedal depression cycle, going <1/4mi down the road is enough to warm the engine beyond the lower temp limit threshold - but, maybe it is.

 

[DT444T]

Try with traction control off or in awd

I was not spinning. And even when I do, there's still boost.

 

[Oxford_Powerboost]

I’ve got an all but confirmed theory for you. The engine doesn’t drive the truck assuming there is enough battery charge until the engine has run for a bit. While it is on, it’s in a cold start warm up cycle. This messes with timing and fueling to dump heat into the catalytic converter to light it off on initial start (this is why you hear it “deeper” sounding for the first 45 seconds or so.) during this time you’ll also note the pedal doesn’t feel like it’s doing much, as the electric motor is the only/primary power source at this time and the ECU tries to protect the engine from a user requesting a cold engine to be under load. During this time you’ll also hear a slightly different tick than normal (if you get the engine to cold start at idle, you can hear the difference when the revs drop from high idle).

Also for what it’s worth, my car before was also a twin turbo V6, not hybrid though. And it limited boost unless you went full throttle when cold to protect itself. Try to avoid boost like the plague until the engine has run for 10+ minutes!

 

[TheGoatman]

I was not spinning. And even when I do, there's still boost.

I figured if you were spinning you would’ve mentioned it. Maybe if the batt is charged it will use the motor and keep the turbos off to proactively not spin the tire. This would all depend on gear too.

I had this happen on a 21 too, did you ever take it in for all the updates, pcm etc?

OP what year is yours?

I can’t tell if the 22 does this because Livernois

 

[Dresdie]

I figured if you were spinning you would’ve mentioned it. Maybe if the batt is charged it will use the motor and keep the turbos off to proactively not spin the tire. This would all depend on gear too.

I had this happen on a 21 too, did you ever take it in for all the updates, pcm etc?

OP what year is yours?

I can’t tell if the 22 does this because Livernois

I havent tried with TC off or confirmed if AWD matters yet but will toy with it.

Buying into Oxford's theory. Thanks, Ox- think you're onto it. BTW, the deeper "growl" I hear is from the intake, not the exhaust - hence why it sounds like the throttle is more open then usual when accelerating after cold start. I have heard what you're saying from the exhaust side.

For reference, I have a build #2, 2021 PB. Don't believe I've received any OTA or dealer-applied ECU updates beyond build date.

 

[Oxford_Powerboost]

I havent tried with TC off or confirmed if AWD matters yet but will toy with it.

Buying into Oxford's theory. Thanks, Ox- think you're onto it. BTW, the deeper "growl" I hear is from the intake, not the exhaust - hence why it sounds like the throttle is more open then usual when accelerating after cold start. I have heard what you're saying from the exhaust side.

For reference, I have a build #2, 2021 PB. Don't believe I've received any OTA or dealer-applied ECU updates beyond build date.

Yeah, as far as I can tell on mine with stock intakes, the noise is a basey intake noise coming from the front. Honestly, sounds a lot better in that first 45 second warm up period to me lol

 

[Dresdie]

Yeah, as far as I can tell on mine with stock intakes, the noise is a basey intake noise coming from the front. Honestly, sounds a lot better in that first 45 second warm up period to me lol

Okay yeah, thats the sound. Haha, I agree.

 

[DT444T]

I figured if you were spinning you would’ve mentioned it. Maybe if the batt is charged it will use the motor and keep the turbos off to proactively not spin the tire. This would all depend on gear too.

I had this happen on a 21 too, did you ever take it in for all the updates, pcm etc?

OP what year is yours?

I can’t tell if the 22 does this because Livernois

So the other day I punched it and it did it AGAIN. Truck was completely warmed up and everything. So I stayed in it and at 50mph or so the boost just came ON. All at once from zero to max boost.

I was in ECO mode. Seems to be the reason.

 

[DBL R]

I’ve had the no boost phenomenon before. For me it’s always happened after starting the vehicle in a parking lot, driving under electric only, then when accelerating from the parking lot into traffic using ICE there is a lag in boost for approximately 5 or so seconds (even with foot to floor) then boost eventually kicks in. This phenomenon does not occur if the ICE kicks on while driving through the parking lot.

this leads me to believe that the system is measuring turbo oil pressure and/or temperature and opens the electronically controlled wastegates to stop boost from building until the turbo is adequately lubricated. This practice is fairly common on performance engines/vehicles.

One recommendation is to flip into tow/haul mode for at least 5-10 seconds before requiring rapid acceleration if starting the vehicle in electric only mode. This will force the vehicle into using the ICE at low speeds and idle.

 

[TheGoatman]

There’s a good chance of that not happening by getting on the latest cal/update for the ecm via dealer or mongoose.

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