Ecoboost vs. V8 - Can you explain?

Lynnmor wrote:
It would be interesting to know where that blue chart above came from. Is it a Raptor truck? Are they running high octane fuel?

The Raptor at the time the 6.2L was available, only had the 6.2L. The H.O. 3.5L didn't come out until after the 6.2L was dropped. The regular output EcoBoost probably won't show a meaningful difference on a dyno. The 91 octane recommendation helps mostly with fuel consumption when towing, and can reduce throttle lag from timing adjustments, but that doesn't happen unless the engine is already very hot. The high-output 3.5L would benefit, but it makes ~500 ft-lbs. of twist.

It would be interesting to know where that blue chart above came from. Is it a Raptor truck? Are they running high octane fuel?

Most modern diesels with VG turbos have very little lag. I would compare the turbo lag of my stock turbo on and stock tune my Cummins to the turbos on my old Ecoboost. With a tune, the turbo lag on my Cummins wasn't even noticeable. With a diesel, you can tune out turbo lag(to a point) since they are regulated by fuel, and not air like gas engines. Older diesel with fixed geometer turbos had a considerable amount of lag, but would have less lag if the latest turbo technology was applied to them.

With my current S364.5/80/.91 turbo, the lag is about what it was stock without a tune, but the turbo comes on much stronger with more air flow while keeping the EGT's and drive pressure much lower than the stock VGT. My current turbo has a lighter forged wheel, better ball bearings, and a T4 pulse manifold (first three cylinders are split form the last three) which aides in response time.

From what I have seen from various videos about the Ecoboost, Ford programmed the EB to open both the intake and exhaust valves if possible for a brief second when going wide open throttle to get the more air flow to the turbos quicker. I still noticed lag when going wide open throttle on a 30 mph roll. It was not much, but it was still there.

While the size of the turbo plays a large role in spool time, so does things like A/R ratio, bearing type, compressor/turbine wheel weight, blade configuration, type of turbo(i.e. twin scroll, VG, or FG), and so on. Turbos can be configured to increase power levels at various rpms, but it is often a give and take with most singe fixed geometery turbos. If you have turbo that spools quickly and makes good power from low to mid, then it will likely loose its breathe on the top end as it goes out of its efficiency zone. The reverse will be true with a large turbo that makes top end power. It will take more rpms to spool and have a considerable amount of lag, but will have enough air to at high rpms.

As I said before, Ford seem to size the turbos on the 3.5L Ecoboost for low to mid rpm power. This is good for low rpm spool and quick response, but it is still a fixed geometry turbo and will have turbo lag regardless. It may be diminished so that most will not notice it, but it will always be there unless they add twin compound or VGT turbo setup.

"If you push the pedal to the floor there is a little turbo lag, but I would be surprised if it was longer than a second. "

The turbo diesels that I have had experience with have very noticeable lag and may even exceed a second. On the other hand, I have never noticed lag on my Ecoboost gas engine even though I am sure that it has to have some. I assume that it is because the Ecoboost has a small turbo for getting started and then does a seamless transition to the large one as it speeds up while the diesels only have one turbo plus they need a lot more boost to get full power.

danrclem wrote:

APT wrote:


Area under the torque curve is what most drivers notice. The green line shows how much torque is available under about 4500rpm than any other compared engine.

I haven't ever had an engine with a turbo so I'd like to know how they work. First of all that's a very impressive torque curve for the Eco Boost. I wish my 6.2 had one like that. When it's running 2,000 rpms would the amount of torque shown be with the turbo running? Does the turbo start running at a certain rpm or at a certain level of throttle position? If the turbo isn't running at 2,000 rpms would the torque be less?

Just wanting to understand a little more.

Yes the turbo is spinning. Keep in mind when you review charts such as this one the data is taken at wide open throttle. You don’t make that much torque with any of the engines when you’re just loafing along. What the chart depicts is the most torque the engine is capable of producing through its rpm band.

danrclem wrote:

APT wrote:


Area under the torque curve is what most drivers notice. The green line shows how much torque is available under about 4500rpm than any other compared engine.

I haven't ever had an engine with a turbo so I'd like to know how they work. First of all that's a very impressive torque curve for the Eco Boost. I wish my 6.2 had one like that. When it's running 2,000 rpms would the amount of torque shown be with the turbo running? Does the turbo start running at a certain rpm or at a certain level of throttle position? If the turbo isn't running at 2,000 rpms would the torque be less?

Just wanting to understand a little more.

The turbine side (wheel with fins like a fan) of the turbo is in the exhaust stream. Anytime your engine is running, your turbo is spinning.
The compressor side (same, like a fan) of the turbo is in the intake tract. This also spins anytime the engine is running.

The turbine wheel and compressor wheel are connected together via a shaft.

At idle the engine is drawing in more air then the turbo is pushing.

At certain throttle and load parameters, the turbo will start to push more air than the engine is pulling in. Thats boost.

The more exhaust your engine makes, the faster the turbo will spin. Up until the wastegate opens. The wastegate is an exhaust "dump" to only allow so much exhaust through the turbo. This therefore is another control of how much boost is being pushed into the engine.

Just a brief explanation of a turbo.
I could literally write for half a day explaining this. So if you want an indepth understanding, its just best to google it or youtube it.

danrclem wrote:


I haven't ever had an engine with a turbo so I'd like to know how they work. First of all that's a very impressive torque curve for the Eco Boost. I wish my 6.2 had one like that. When it's running 2,000 rpms would the amount of torque shown be with the turbo running? Does the turbo start running at a certain rpm or at a certain level of throttle position? If the turbo isn't running at 2,000 rpms would the torque be less?

Just wanting to understand a little more.

Yes, the amount shown is with the turbo running. The turbos start to spool at a very low rpm and I am not sure you could even get the truck to shift into an rpm they can't build boost at. Under normal acceleration, you will start to build boost as low as 1,200 rpm. They are mainly low to mid rpm turbos and loose their breath at higher rpms past 4,500. This is good for quick responsiveness while towing and normal driving, but not so much on the drag strip.

If you push the pedal to the floor there is a little turbo lag, but I would be surprised if it was longer than a second.

APT wrote:


Area under the torque curve is what most drivers notice. The green line shows how much torque is available under about 4500rpm than any other compared engine.

I haven't ever had an engine with a turbo so I'd like to know how they work. First of all that's a very impressive torque curve for the Eco Boost. I wish my 6.2 had one like that. When it's running 2,000 rpms would the amount of torque shown be with the turbo running? Does the turbo start running at a certain rpm or at a certain level of throttle position? If the turbo isn't running at 2,000 rpms would the torque be less?

Just wanting to understand a little more.

srt20 wrote:
Inline maybe a better design, but they just dont fit in vehicles well anymore. Curved down hoods, shorter front ends, etc. The V block engines barely fit now. Look under the hood of a V8 diesel with turbos. Its shoved way under the cowl, and all the way to the radiator support. Then add 2 more cylinders to that length...

BTW I have a 3.5L Ecoboost. And either I have a bad one or there's alot of people that fib about their mpg. I got 7.9mpg towing a 30ft enclosed all aluminum 7.5ft wide trailer that weighed about 5000lbs loaded. And I havent seen 20mpg on the EVIC (which always reads high) in a LONG time.

Turbocharged gas engines need fuel.

Yep you must have got a bad one, had the improper gearing, too high speed...etc
I've towed over 60k now with my 2 ecos and they consistently get 10 or better and that is not per that lie o meter that is hand calculated. The lie o meter always tells me above 11 and that is towing my 7000lb 30 foot travel trailer through the mountains of pa, west virginia, and north carolina. All engines need fuel and my 2 turbo charged ecos require less fuel to do the same as any naturally aspirated gas engine I have owned towing or not...the 5.4 and 5.0 being the absolute worst...

srt20 wrote:
Inline maybe a better design, but they just dont fit in vehicles well anymore. Curved down hoods, shorter front ends, etc. The V block engines barely fit now. Look under the hood of a V8 diesel with turbos. Its shoved way under the cowl, and all the way to the radiator support. Then add 2 more cylinders to that length...

BTW I have a 3.5L Ecoboost. And either I have a bad one or there's alot of people that fib about their mpg. I got 7.9mpg towing a 30ft enclosed all aluminum 7.5ft wide trailer that weighed about 5000lbs loaded. And I havent seen 20mpg on the EVIC (which always reads high) in a LONG time.

Turbocharged gas engines need fuel.

You must have a bad one. I have about 1,000 miles towing with mine and I consistently get about 10 mpg; I stay at or under 70 mph. Worse I ever got was 9.9.