sluggo1

Just some info I found online. Has probably been discussed before. But for those complaining or concerned about hesitation when accelerating with Ecoboost maybe this will make you realize it is normal with turbos. Sorry should have posted in engine section. Mods move at your discretion.

What Are the Causes of Turbo Lag?
By Patrick Gleeson, eHow Contributor
Turbo lag is the hesitation, before acceleration, when you step on the accelerator of a car with a turbocharged engine. To some extent, turbo lag has physical causes inherent in turbocharger technology. However, different turbocharger designs and different conditions will affect the degree of lag.


Turbocharger Basics
A turbocharger uses engine exhaust to power a spinning rotor in a chamber above the engine intake. The air-fuel mixture flows through this chamber; the rotor compresses it and delivers a denser air-fuel mixture with higher potential energy to the cylinders.
The Key to Turbo Lag
How quickly the rotor in the turbocharge accelerates--how quickly it can increase pressure in the intake manifold--depends on the pressure in the exhaust manifold. An idling engine generates relatively small amounts of exhaust gas; the engine first has to accelerate in order to increase the amount of exhaust gas, which increases exhaust gas pressure. The exhaust gas pressure has to increase before the exhaust gas can power the turbocharger, and the turbocharger has to rev up before it can increase pressure in the intake system. From the beginning of this process to the end takes time. The time it takes is "turbo lag."
Inertia
It takes more energy to push an object from rest to walking speed than it does to continue pushing an object that's already at walking speed. This force is called "inertia." It takes more inertial force to push a 200 lb. object from rest to walking speed than it takes to push a 100 lb. object.
Inertia and Turbo Lag
The weight of the moving parts in a turbocharger affects the force needed to accelerate the turbo. A turbo rotor (sometimes called "vein" or "wheel") made of very lightweight alloys will produce less turbo lag than a heavier rotor because it takes less inertial force to accelerate it--there's less mass. Also, a compact rotor design generally requires less centrifugal force and will therefore accelerate faster and with less lag than a larger diameter rotor.
Driving Conditions
Driving conditions and different transmission designs will also affect turbo lag. An engine already revving above 3,000 RPM has more energy in the system than an idling engine; systems with greater internal energy will always overcome turbo lag faster than lower energy systems. Similarly, transmission designs that keep engine revs high will produce less turbo lag than designs that require sudden engine accelerations and decelerations at shift points.

E-Town F150

Coles notes version: turbochargers are exhaust driven and it taken a short, but in some cases noticeable, amount of time to build up exhaust pressure to spin the impeller that is attached to the turbocharger via a shaft, which forces more air into the engine.

Modern turbos are made with lightweight materials, which means they spin more easily than the turbos of yesterday. The nice part...free power.

ninjatalon

iTrader: (1)

But the hesitation is not turbo lag. Cool article though.

Viking1204

Great article and it definitely explains something I've discovered on my own. I figured out if you take off with moderate acceleration and then punch it the turbos respond much quicker and the truck really takes off. I have to pull out onto 4 lane highway with a 55 mph speed limit everyday 3 miles from a military base entrance where I work. Traffic is heavy but moving at 60+ mph so I've learned how to get the truck moving as quick as I can. I think I surprise a lot of people at how fast a big truck can get up and go, I see a lot of people change out of my lane when I pull out but they never come close to catching up to me and usually change back into my lane when they realize that. So far loving my Ecoboost with the twin turbos!

sluggo1

Exactly. With turbo have to feather the throttle a bit. Can't just mash pedal to the floor. Previous poster said hesitation issue people are having is not turbo lag but seems like that is exactly what it is. So the guys saying they go to punch it to pass a semi on the expressway and it falls flat is because of the turbo lag is it not?

goodburbon

The hesitation I feel is not turbo lag, it's the transmission thinking about which gear, picking the wrong one, revving to the sky, then shifting to the correct gear and accelerating like a bat out of hell.

Turbo lag I would expect and accept.

1_T_Scot

Just to help expand the disscussion this portion of the article does not apply to EcoBoost or to Diesels that are Direct injected.

The Air is pulled in through the Air filter compressed in the Turbo chargers then cooled in the Charge Air cooler (Or intercooler take your pick) Somewhere in there is a Mass Airflow sensor (Still no fuel) then it goes into the Intake (or Chamber above the Intake) the air (still no fuel) enters the Cylinder head through the intake valve(s) after the Intake closes and the Piston gets close to TDC then Fuel gets added at Way higher pressure than Port injected engines. Injection pressure for Current Diesel is 35,000-40,000PSI I'm not sure what Ecoboost is but its a lot higher that port.

Why is this important???

Compression the Ecoboost is high (for a Turbo engine) 10:1 If you where too have a port injection that had this high of compression and a turbo Detonation would be really bad on 87 octane fuel. With the Ecoboost the Fuel is not there to explode (detonate early).

The 10:1 compression makes the engergy created before Turbo boost pretty healthy which helps limit the lag.

JMHO.

jacoviii

coppercarbide

Just a quick note here. There are two distinct hesitations in these trucks, both turbo lag and poor transmission programming play a factor here.

I come from the world of modified Honda's, so I'm very very familiar with turbo lag. One thing we do to minimize that is change the transmission gearing a bit so the gears are longer.

Turbocharged engines have a much, MUCH flatter torque curve than NA engine, which means that more of a gear is usable, and you get much less utility from downshifting.

Ford has taken a turbocharged engine, and matched it with a transmission program for an NA engine. When you stomp the throttle, the transmissions first reflex is to downshift a lot, which would be correct in an NA application to get in the powerband (especially on the 5.0 or the 3.7). The reason it is SO pronounced is that the truck is optimized for hauling and towing stuff, not accelerating. When it revs high, it expects there to be a large load (ie: going up a hill with a box full of dirt). In the 5.0 and 3.7, the revs are needed to hold speed. The 3.5 doesn't need the revs.

However, for the EcoBoost, the correct shift would be a gear higher than it is doing, to allow the turbo's time to build as the engine has more than sufficient power in the mid-range to make the extra time of shifting completely useless, especially because the turbos have to spool twice.

So yeah, both hesitation issues could actually be greatly mitigated by programming the transmission properly for a turbocharged engine.

jcain

Or just put it in M and just bump down one gear if needed. That's what I do