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The new Ford F150: a twin turbo straight 6?
By: The Moo News Network
Interviewer: Rumor has it that Ford is working on an all-new straight six engine for the F-150. What do you know about that?
CowboyBenWade: Yes, Ford is designing a next generation engine for the F-150. The current ecoboost engines, specifically the 3.5 has had a good run, but it's a flawed engine in many ways. And it's been in the F150 since 2011, and Ford has never really fixed the issues with cam phasers. It also doesn't get better fuel economy than the v8 in real world driving - say what you want about that. Ford is tired of fixing the issues with the 3.5, and needs a new flagship ecoboost engine. The 2.7 is great, but it's not large enough and doesn't have enough high end power to be their flagship engine.
Interviewer: So Ford needs a new engine, why did they choose to develop the straight 6?
CowboyBenWade: Ford had a straight 6 for many decades but phased them out. It was one of the best engines the company ever designed, and with new technology, the resurrection of the straight 6 could be a game changer for Ford. A lot of people do not like the perceived complexity of the v-6 ecoboost engines.
Interviewer: What makes a straight 6 engine better than a V6 or V8?
CowboyBenWade: Less parts. V6s and v8s have two heads, four camshafts, and turbos and intercoolers on top of that - a straight 6 would simplify a lot of things. You would only have one head, two camshafts - just less stuff to break. That's always been the allure of straight 6 engines - large diesel semi-trucks even use straight 6 engines for this reason. Most all semis use straight 6s. They say, "These truck need to run a million miles, so we need to build it with less parts that can break." The cummins diesel engine is a straight 6, and it's found in Ram trucks and many other applications.
Interviewer: Are there any other benefits to straight 6 as opposed to other engine designs?
CowboyBenWade: One of the biggest benefits is that six cylinders in a line are inherently balanced, so you can make the displacement as big as you want. An inline 4 cylinder engine cannot balance forces completely, and that's why these engines are limited in displacement - they vibrate too much as they get bigger. You never see a 5.0 liter 4 cylinder. At under 3 liters, 4 cylinders can work. The inline 6 can be scaled to any size, and you often see diesel inline 6s that are over 8 liters. For example the CAT’s 3406 engine is 14.6 liters.
Interviewer: So could a straight 6 F150 get better fuel economy and have equal or more power than the current ecoboost v6 engines?
CowboyBenWade: Ford's plan is to use what's called pre-chamber ignition in their new straight 6.
Interviewer: What is pre-chamber ignition?
CowboyBenWade: Here is some background on pre-chamber ignition - engines need a certain amount of fuel in their cylinder for it to ignite with a spark. If it's too lean, it won't ignite. Obviously, it takes more fuel to get enough fuel in there so it will ignite, which lowers fuel economy. In an engine with pre-chamber ignition - there is a separate, small chamber that's connected to the main cylinder with a port. Get this small chamber rich enough with fuel to start ignition and keep the main chamber more lean - that's the idea. The explosion and fire jets coming out of the pre-chamber port are enough to ignite the leaner fuel/air mixture in the main chamber (a spark plug wouldn't be enough). In theory, this would allow an engine to run a leaner fuel/air ratio i.e. use less fuel.
I think this design would be too complicated to use in a v-shaped engine, and that's why ford is opting to use this technology in a straight 6. And Ford is going to use twin turbos on this engine because there wouldn't be enough power without them. It could theoretically produce whatever amount of horsepower Ford decides. Because of the leaner fuel/air mixture, Ford could increase boost even more and still retain acceptable fuel economy.
Interviewer: How much better fuel economy would such an engine achieve?
CowboyBenWade: It's less than you think, probably 2-4 mpg difference versus their 3.5 ecoboost. So that might amount to overall 22mpg for the F150 which would be great. But Ford is not doing this because they care about you spending less money on gas - for them it's about the environment. The F150 is the best selling vehicle in America - and a few mpg improvement in the best selling vehicle will make a huge difference at that scale. And I'm all for efficiency, as long as it's a better engine. I do not want to sacrifice performance or towing capability for a couple miles per gallon. Give me the V8 unless there they can convince me that their six cylinder turbo is superior in every way.
CowboyBenWade: Yes, Ford is designing a next generation engine for the F-150. The current ecoboost engines, specifically the 3.5 has had a good run, but it's a flawed engine in many ways. And it's been in the F150 since 2011, and Ford has never really fixed the issues with cam phasers. It also doesn't get better fuel economy than the v8 in real world driving - say what you want about that. Ford is tired of fixing the issues with the 3.5, and needs a new flagship ecoboost engine. The 2.7 is great, but it's not large enough and doesn't have enough high end power to be their flagship engine.
Interviewer: So Ford needs a new engine, why did they choose to develop the straight 6?
CowboyBenWade: Ford had a straight 6 for many decades but phased them out. It was one of the best engines the company ever designed, and with new technology, the resurrection of the straight 6 could be a game changer for Ford. A lot of people do not like the perceived complexity of the v-6 ecoboost engines.
Interviewer: What makes a straight 6 engine better than a V6 or V8?
CowboyBenWade: Less parts. V6s and v8s have two heads, four camshafts, and turbos and intercoolers on top of that - a straight 6 would simplify a lot of things. You would only have one head, two camshafts - just less stuff to break. That's always been the allure of straight 6 engines - large diesel semi-trucks even use straight 6 engines for this reason. Most all semis use straight 6s. They say, "These truck need to run a million miles, so we need to build it with less parts that can break." The cummins diesel engine is a straight 6, and it's found in Ram trucks and many other applications.
Interviewer: Are there any other benefits to straight 6 as opposed to other engine designs?
CowboyBenWade: One of the biggest benefits is that six cylinders in a line are inherently balanced, so you can make the displacement as big as you want. An inline 4 cylinder engine cannot balance forces completely, and that's why these engines are limited in displacement - they vibrate too much as they get bigger. You never see a 5.0 liter 4 cylinder. At under 3 liters, 4 cylinders can work. The inline 6 can be scaled to any size, and you often see diesel inline 6s that are over 8 liters. For example the CAT’s 3406 engine is 14.6 liters.
Interviewer: So could a straight 6 F150 get better fuel economy and have equal or more power than the current ecoboost v6 engines?
CowboyBenWade: Ford's plan is to use what's called pre-chamber ignition in their new straight 6.
Interviewer: What is pre-chamber ignition?
CowboyBenWade: Here is some background on pre-chamber ignition - engines need a certain amount of fuel in their cylinder for it to ignite with a spark. If it's too lean, it won't ignite. Obviously, it takes more fuel to get enough fuel in there so it will ignite, which lowers fuel economy. In an engine with pre-chamber ignition - there is a separate, small chamber that's connected to the main cylinder with a port. Get this small chamber rich enough with fuel to start ignition and keep the main chamber more lean - that's the idea. The explosion and fire jets coming out of the pre-chamber port are enough to ignite the leaner fuel/air mixture in the main chamber (a spark plug wouldn't be enough). In theory, this would allow an engine to run a leaner fuel/air ratio i.e. use less fuel.
I think this design would be too complicated to use in a v-shaped engine, and that's why ford is opting to use this technology in a straight 6. And Ford is going to use twin turbos on this engine because there wouldn't be enough power without them. It could theoretically produce whatever amount of horsepower Ford decides. Because of the leaner fuel/air mixture, Ford could increase boost even more and still retain acceptable fuel economy.
Interviewer: How much better fuel economy would such an engine achieve?
CowboyBenWade: It's less than you think, probably 2-4 mpg difference versus their 3.5 ecoboost. So that might amount to overall 22mpg for the F150 which would be great. But Ford is not doing this because they care about you spending less money on gas - for them it's about the environment. The F150 is the best selling vehicle in America - and a few mpg improvement in the best selling vehicle will make a huge difference at that scale. And I'm all for efficiency, as long as it's a better engine. I do not want to sacrifice performance or towing capability for a couple miles per gallon. Give me the V8 unless there they can convince me that their six cylinder turbo is superior in every way.
About the Author
CowboyBenWade does interviews and lectures on a huge variety of topics, and he is an expert in a multitude of fields. His knowledge includes but is not limited to: engineering, chemistry, aviation, cooking, and farming.
Much of the world is clamboring to interview him at any given time. This is a transcript of one such interview.