Ecoboost question for DP

[handirifle]

Or anyone else that seems to know Fords like the back of their hand.

Not looking to switch over or anything drastic like that, but wanting to understand them. I know the 3.5 EB has 2 turbos, or at least I think they do, so how do they work? Are they compound, or parallel? How does Ford get that excellent torque down low and keep it almost to 5K?

Like I said, I am not switching from diesel, now that I'm there, but the EB is impressive for a gasser.

 

[Diamondpilot]

I'm not really sure. Jonesboro is the technical guy.

All I know is mine with 3.73 gears pulls like a freight train.

Chris

 

[tcartwri]

In parallel. And they are tiny.

The small size allows near instant spool up and boost. To give you a rule of thumb, doubling atmospheric pressure with boost, effectively doubles the displacement of the motor. So a 3.5 L feels like a 7 L with just 15 psi of boost.

 

[dodge man]

I asked the same question a few months ago, and yes they are parallel. Two little turbos spool up pretty quick. I know on the 6.4 Powerstroke, they were sequential.

 

[tcartwri]

A visual on what's happening inside a turbo'd engine. You'll notice that peak pressure is delayed by a few degrees because of the different ignition timing curve and that the total area under the curve is much larger.

 

[dodge man]

Another reason not to go sequential is the boost pressure. 15 psi of boost is very high for a gas engine but 30 psi for a diesel engine is very common.

 

[handirifle]

Yea my truck hits 25 pretty easy. Seems I read somewhere, that there is a cam timing design that opens the exhaust valves open longer, or earlier (not sure which) to cause faster spool up. Any truth to that?

I had wondered about a lot of the turbo gassers in the past, and they all seemed designed for high RPM ops and seemed like turbo lag was bad because of it, ie. The 80's Buick 3.8 v6.

It makes a little more sense on a pass car, but a truck is for work, IMHO.

 

[MikePA]

It makes a little more sense on a pass car, but a truck is for work, IMHO.

Don't most big rig trucks have turbocharged engines?

 

[dodge man]

If you are talking about diesels, lots of things affect spool up, the inducer size, housing size, shape of the inducer, cam timing, injection timing, the number of injection events and probably stuff I don't know about.

 

[tcartwri]

It makes a little more sense on a pass car, but a truck is for work, IMHO.

That's where the direct injection comes into play. You would never be able to load a turbo gas motor at low rpm without it. It would detonate itself to death.