1.5 Engine at highway speeds

[dejones64]

TL;DR: Absent a boost-pressure gauge (or equivalent OBD-II/Ford CANbus data), or a good human ear with the windows down on a quiet road, it's seat-of-the-pants. You'll literally feel a lag between request for acceleration, and the onset of "substantial" acceleration which is •not• related to any transmission gear-downshift(s).


Turbo lag (delay between power demand and point where turbo has spooled-up from exhaust-gas pressure sufficiently to deliver an intake-air pressure boost) manifests as a seeming "sluggishness" that goes away as you lean into the throttle (i.e. press on the "gas pedal"). Larger turbos, and poorly designed throttle-plate sectors in mechanical-throttle vehicles increase the likelihood of substantial turbo lag.

Ford uses drive-by-wire for throttle control, so the "gas pedal" really has only a passing relationship to the throttle-plate angle/aperture itself, with maps (response-curves) for "gas pedal" position to throttle-plate angle changing depending on G.O.A.T. mode (among other factors).

A more aggressive response-curve in Sport mode means an "N% press" of the "gas pedal" will result in a larger throttle-plate angle/aperture than it would in Eco mode, for example. More air in -> more fuel in -> more power and exhaust gas out -> more turbo pressure "sooner".

These response-curves may (NOT A FORD ENGINEER!) also take into account rate-of-change in "gas pedal" motion in order to predict throttle demand, and transiently "spike" the throttle-plate open a bit further/faster than would occur for a slower pedal-press, resulting in reduction of human-perceived turbo-lag because the throttle-plate, engine, and turbo are actually reacting to predicted imminent demand, rather than actual measured demand. I've driven at least one vehicle from another manufacturer where this was done in order to provide non-turbo-like engine characteristics for people coming from larger displacement naturally-aspirated sport engines.

The turbo in both of the Ford Bronco Sport engines itself is likely sized appropriately for the engine, and throttle response-curves tuned to minimize turbo lag. But, in this thread's scenario, you're also talking about a 1.5 litre intercooled-single-scroll-turbo I3 on a ~3900 lb vehicle. There will still be •some• lag.

You'd notice turbo lag most in Eco mode, where the goal is best fuel economy, and not best ("crispest") throttle responsiveness.

You'd notice turbo lag least in Sport mode, where the goal is best ("crispest") throttle responsiveness and maximum output (horsepower and torque) from the engine when requested.


EDIT: One addendum, I checked with FORScan Lite, there is no turbocharger specific sampling data available, but you can look at the difference in measured absolute barometric and manifold pressures to extrapolate when the turbo is pushing air, manifold > barometric == turbo definitely making pressure.

Thanks for that writeup. All greek to me. I've been driving manuals all my life, now in this automatic, every time I push the gas pedal it feels sluggish/laggish. Not the instant response like in a manual. Thanks though for explaining this.

I have less than a 1000 miles on it, mostly in Normal. Tried Sport and Eco (1 tank of gas each), I do feel the quick response in Sport and the sluggishness in Eco.

If it matters, I use 87 octane in my simple Mitsubishi Lancer manual; 88 octane in the BS.

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[Larryjaquins]

Just went on a drive doing 72 mph and average 33 mpg with cruise control set. I don’t have copilot 360. i have had mine up to 80 mph and drove home in sport mode, you can see the gas mileage drop. I averaged 30 mpg for whole trip

 

[Flash]

2,000 rpm at 70 mph, 2150 or so rpm at 80 mph, obviously got a couple of sorta overdrive gears there. They're trying to keep the engine just a bit below the torque peak as much as possible IMO.

 

[AndyMac204]

@VirtualJMills - excellent writeup. legit.

 

[CrashBend]

We have the OB with the 1.5L engine and find it has plenty of power for highway cruising. Most of the time we keep it in eco mode. It will jump right up if you floor it. We like the gas economy. We drive around 60mph. In the right lane out of your way....lol

 

[VirtualJMills]

Thanks for that writeup. All greek to me. I've been driving manuals all my life, now in this automatic, every time I push the gas pedal it feels sluggish/laggish. Not the instant response like in a manual. Thanks though for explaining this.

I have less than a 1000 miles on it, mostly in Normal. Tried Sport and Eco (1 tank of gas each), I do feel the quick response in Sport and the sluggishness in Eco.

If it matters, I use 87 octane in my simple Mitsubishi Lancer manual; 88 octane in the BS.

Let me try a different analogy: The garden hose.


When you connect a garden hose with a closed-nozzle on the garden-end to a spigot, you're introducing possible latency (lag) into the behavior of the nozzle on the other end. A turbocharger has similar latency for vaguely related reasons, bear with me.

So you have this garden hose, nozzle still closed, and you open the spigot on the other end of the hose. Consider the existing contents of the garden hose at this point, and your subsequent actions.

You open the nozzle.

If the turbo is already spooled-up (garden hose was "pre-charged" with water at or close-to-at appropriate pressure), your demand-request (opening the nozzle / pressing on the "gas pedal") will be serviced immediately (water exits the nozzle at-pressure immediately).

If the turbo is not already spooled-up (garden hose is full of air still) you'll experience some lag between demand-request (opening the nozzle / pressing on the "gas pedal") and servicing of that request (water exiting the nozzle). Water needs to pressurize that garden hose to somewhere between service pressure (pressure at the spigot) and operating pressure(*) in order to compress and expel the air, replace it with water, and bring the requested water exiting the nozzle up to the flow + pressure you're requesting.

(*) Pressure as measured at the nozzle (throttle-aperture) for the water when flowing as you've requested.

If you only open the nozzle a tiny bit, and/or do it slowly, the way that lag manifests is different.

In the case of the turbo in the Bronco Sport, the only direct measurement data we have available is from inside the throttle body (MAP/MAF manifold absolute pressure) downstream of the throttle-plate headed into the cylinders, and a comparison measurement from the ambient environment (absolute barometric pressure). I haven't found measurements for the upstream (turbo) side of the throttle-body, which would allow for more detailed analysis.

The analogy of treating the throttle-plate as the exact equivalent to a garden hose nozzle breaks-down a bit here, because the turbo charger is actually a pump somewhere upstream in the intake plumbing (like a booster pump on a length of garden hose).

When the manifold pressure is above ambient environment, we can guarantee that the turbo (booster pump) is helping, but for pressures between high-vacuum and equal-to-ambient, we can only infer that it is spinning idly (demand lower than steady-state airflow, turbo RPM is static) or spooling-up (demand greater than steady-state airflow, and turbo RPM is increasing).

Because we don't have the pressure on the upstream (turbo) side of the throttle-body as well, it is more difficult to determine how close to properly spooled-up the turbo is until you introduce substantial demand ("gas pedal" pressed / throttle-plate opening), and then you're still stuck making some inferences, as the three (1.5l I3) or four (2.0l I4) hungry-hungry hippos are eagerly consuming the delivered air further downstream.

FWIW, unleaded gasoline fuel octane rating (RON+MON or whomever's preferred math being used) and percentage of dissolved ethanol (EtOH has a different octane rating, different energy-yield during combustion, etc…) makes things a bit more complicated during full-load (Wide-open-Throttle) acceleration analysis, but does not introduce much added complexity in simply noticing turbocharger lag / spool-up time. -- Your brain and butt is still the best way to notice it.

Any errors in the above are soley my own.

 

[dejones64]

Let me try a different analogy: The garden hose.


When you connect a garden hose with a closed-nozzle on the garden-end to a spigot, you're introducing possible latency (lag) into the behavior of the nozzle on the other end. A turbocharger has similar latency for vaguely related reasons, bear with me.

So you have this garden hose, nozzle still closed, and you open the spigot on the other end of the hose. Consider the existing contents of the garden hose at this point, and your subsequent actions.

You open the nozzle.

If the turbo is already spooled-up (garden hose was "pre-charged" with water at or close-to-at appropriate pressure), your demand-request (opening the nozzle / pressing on the "gas pedal") will be serviced immediately (water exits the nozzle at-pressure immediately).

If the turbo is not already spooled-up (garden hose is full of air still) you'll experience some lag between demand-request (opening the nozzle / pressing on the "gas pedal") and servicing of that request (water exiting the nozzle). Water needs to pressurize that garden hose to somewhere between service pressure (pressure at the spigot) and operating pressure(*) in order to compress and expel the air, replace it with water, and bring the requested water exiting the nozzle up to the flow + pressure you're requesting.

(*) Pressure as measured at the nozzle (throttle-aperture) for the water when flowing as you've requested.

If you only open the nozzle a tiny bit, and/or do it slowly, the way that lag manifests is different.

In the case of the turbo in the Bronco Sport, the only direct measurement data we have available is from inside the throttle body (MAP/MAF manifold absolute pressure) downstream of the throttle-plate headed into the cylinders, and a comparison measurement from the ambient environment (absolute barometric pressure). I haven't found measurements for the upstream (turbo) side of the throttle-body, which would allow for more detailed analysis.

The analogy of treating the throttle-plate as the exact equivalent to a garden hose nozzle breaks-down a bit here, because the turbo charger is actually a pump somewhere upstream in the intake plumbing (like a booster pump on a length of garden hose).

When the manifold pressure is above ambient environment, we can guarantee that the turbo (booster pump) is helping, but for pressures between high-vacuum and equal-to-ambient, we can only infer that it is spinning idly (demand lower than steady-state airflow, turbo RPM is static) or spooling-up (demand greater than steady-state airflow, and turbo RPM is increasing).

Because we don't have the pressure on the upstream (turbo) side of the throttle-body as well, it is more difficult to determine how close to properly spooled-up the turbo is until you introduce substantial demand ("gas pedal" pressed / throttle-plate opening), and then you're still stuck making some inferences, as the three (1.5l I3) or four (2.0l I4) hungry-hungry hippos are eagerly consuming the delivered air further downstream.

FWIW, unleaded gasoline fuel octane rating (RON+MON or whomever's preferred math being used) and percentage of dissolved ethanol (EtOH has a different octane rating, different energy-yield during combustion, etc…) makes things a bit more complicated during full-load (Wide-open-Throttle) acceleration analysis, but does not introduce much added complexity in simply noticing turbocharger lag / spool-up time. -- Your brain and butt is still the best way to notice it.

Any errors in the above are soley my own.

Thanks for the analogy, I understand it a bit better. Yea wish there was a gauge or some visual indicator.

 

[BigD]

Hey all, I have an order in for a Big Bend and I plan to do some highway driving and some road trips once or twice a year (think 1000-1500 miles). I'm just curious how the 3 cyl performs on the highway. I'm not planning to do more than 75mph usually and don't need huge performance, just cruising for long periods (I got the CoPilot+ just for the Adaptive cruise for long trips lol).

Also, what are the rpms usually at around 70-75 mph?

Thanks! Very excited for this as it's my first brand new vehicle. Just debating if I should wait another year to save a bit more to get the 2.0 Badlands. I know the 3 cyl will be fine for my daily drive, just concerned about the highway.I have driven 17,000 miles in 3 months. Most of it Highway. Trust me. You will love it. RPMs 1500-1700. A@ 7ph. Smooth ride. Mine is BadLands BS. I Ann very oleased

 

[BigD]

Sorry. Big Bend. Mot Bad Lands.

 

[SilentBanshee424]

Sorry. Big Bend. Mot Bad Lands.

The big bend is what I have on order so I'm very happy to see you love yours.

 

[Osco]

First time turbo for me. How does one know it’s spooled up to speed? Thanks.

Simply put. The turbo starts spinning up @ 1700 RPM.
Boost crosses 4psi at about 1900 rpm IF your accelerating. Boost climbs to I think 8 or 10 by 2600 rpm again IF your still on the throttle.
Around 3400 Rpm boost is near 12.
After that your Horse power starts to fill in.
Zoom Zoom,,,,
Oh crap wait, That’s Mazda,,

 

[Osco]

Let me try a different analogy: The garden hose.


When you connect a garden hose with a closed-nozzle on the garden-end to a spigot, you're introducing possible latency (lag) into the behavior of the nozzle on the other end. A turbocharger has similar latency for vaguely related reasons, bear with me.

So you have this garden hose, nozzle still closed, and you open the spigot on the other end of the hose. Consider the existing contents of the garden hose at this point, and your subsequent actions.

You open the nozzle.

If the turbo is already spooled-up (garden hose was "pre-charged" with water at or close-to-at appropriate pressure), your demand-request (opening the nozzle / pressing on the "gas pedal") will be serviced immediately (water exits the nozzle at-pressure immediately).

If the turbo is not already spooled-up (garden hose is full of air still) you'll experience some lag between demand-request (opening the nozzle / pressing on the "gas pedal") and servicing of that request (water exiting the nozzle). Water needs to pressurize that garden hose to somewhere between service pressure (pressure at the spigot) and operating pressure(*) in order to compress and expel the air, replace it with water, and bring the requested water exiting the nozzle up to the flow + pressure you're requesting.

(*) Pressure as measured at the nozzle (throttle-aperture) for the water when flowing as you've requested.

If you only open the nozzle a tiny bit, and/or do it slowly, the way that lag manifests is different.

In the case of the turbo in the Bronco Sport, the only direct measurement data we have available is from inside the throttle body (MAP/MAF manifold absolute pressure) downstream of the throttle-plate headed into the cylinders, and a comparison measurement from the ambient environment (absolute barometric pressure). I haven't found measurements for the upstream (turbo) side of the throttle-body, which would allow for more detailed analysis.

The analogy of treating the throttle-plate as the exact equivalent to a garden hose nozzle breaks-down a bit here, because the turbo charger is actually a pump somewhere upstream in the intake plumbing (like a booster pump on a length of garden hose).

When the manifold pressure is above ambient environment, we can guarantee that the turbo (booster pump) is helping, but for pressures between high-vacuum and equal-to-ambient, we can only infer that it is spinning idly (demand lower than steady-state airflow, turbo RPM is static) or spooling-up (demand greater than steady-state airflow, and turbo RPM is increasing).

Because we don't have the pressure on the upstream (turbo) side of the throttle-body as well, it is more difficult to determine how close to properly spooled-up the turbo is until you introduce substantial demand ("gas pedal" pressed / throttle-plate opening), and then you're still stuck making some inferences, as the three (1.5l I3) or four (2.0l I4) hungry-hungry hippos are eagerly consuming the delivered air further downstream.

FWIW, unleaded gasoline fuel octane rating (RON+MON or whomever's preferred math being used) and percentage of dissolved ethanol (EtOH has a different octane rating, different energy-yield during combustion, etc…) makes things a bit more complicated during full-load (Wide-open-Throttle) acceleration analysis, but does not introduce much added complexity in simply noticing turbocharger lag / spool-up time. -- Your brain and butt is still the best way to notice it.

Any errors in the above are soley my own.

Man that’s sum serious BS info.
I mean turbo scuttle but.
I can dig it !
If I may add a tidbit…
My Brothers twin turbo F 150,,,,
The first Turbo is very small, tiny.
That garden hose fills up in a flash,
That turbo gets his truck off the line faster thereby hiding the lag of the second larger main turbo.
I drove it. It works.
Feels like his turbo kicks in at 1,000 RPM,,,
We could not notice any lag under any conditions.
He could light the tires with that V-6 and pull the snot outta his 6,700 pound camping trailer. Climbed long grades like a Mac truck.
FORD did this with a V-6 !!!!!!

 

[VirtualJMills]

EDIT: One addendum, I checked with FORScan Lite, there is no turbocharger specific sampling data available, but you can look at the difference in measured absolute barometric and manifold pressures to extrapolate when the turbo is pushing air, manifold > barometric == turbo definitely making pressure.

Some background on the BOOST pressure vs. MANIFOLD ABSOLUTE pressure vs. ATMOSPHERIC pressure triangle:

 

[VirtualJMills]

Also couldn't resist this one, yet another metaphor on turbo boost / turbo lag:

 

[kvenerable]

Just did 700 miles each way, NV to Denver and back in a 1.5 OB. So, I70 across UT and over the Rockies. Was very surprised at how well it did. No issues. I tend to drive quick and fast, Recent vehicles include new Vette, Ram Hemi, Wrangler, Ranger. I was leery of the 3 cylinder (couldn’t find a Badlands) but it’s been fine so far.

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