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The New 6.8L V8 Thread


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16 minutes ago, jpd80 said:

I think that the truth is that 7.3 was painted as one size fits all applications from F250 to F750.

I can imagine a suit saying, “build one engine that does everything”.

Sounds about right !  I still think it is odd that the E-Series has a de-tuned version.

6.8L would be a great base engine for a F250 and a low cost replacement for the Coyote in the F150.

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15 minutes ago, theoldwizard1 said:

Sounds about right !  I still think it is odd that the E-Series has a de-tuned version.

6.8L would be a great base engine for a F250 and a low cost replacement for the Coyote in the F150.

But would they make a 6.8L with iron and aluminum block. Not likely. And unlike the 6.2L which lived in F150 and SD for 4 year overlap I don't think they will put an iron block in a F150 today. Too heavy. And aluminum block in a SD would melt like butter in Az summer.  Would never handle the tougher SD durability testing. Same reason no EB in a SD or a 6.2L gm in a gm HD.

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1 hour ago, theoldwizard1 said:

Sounds about right !  I still think it is odd that the E-Series has a de-tuned version.

6.8L would be a great base engine for a F250 and a low cost replacement for the Coyote in the F150.

The two tunes is probably cheaper to do than offering two engine capacities.

 

I still think that the 6.8 is a HP designator like 429 vs 460 and will be reserved for limited high end use.

I don’t see it replacing the 5.0 coyote which now has cylinder deactivation……

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1 hour ago, Power Kid said:

But would they make a 6.8L with iron and aluminum block. Not likely. And unlike the 6.2L which lived in F150 and SD for 4 year overlap I don't think they will put an iron block in a F150 today. Too heavy. And aluminum block in a SD would melt like butter in Az summer.  Would never handle the tougher SD durability testing. Same reason no EB in a SD or a 6.2L gm in a gm HD.

The iron block 7.3 is about a hundred pounds heavier than an all aluminium Coyote.

 

EB in a SD doesn’t  work in a heavy duty truck or Van because it would be under constant boost and richer mixtures, that’s an area where a big capacity engine makes more fuel efficient mid range power and torque.
Even towing like 9,000 lbs, a 5.0 F150 is more fuel efficient than the EB35, V8s are still needed.

Edited by jpd80
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Agree, you are right re mpg and running rich. And I am right cause as stated it would never survive SD durability standards. Same reason gm didn't drop the 6.2L into the hd when it made more # than the old 6.0L. Wouldn't have survived the stress. (Plus rated on premium)  instead they designed new 6.6L.

 

20210820_200354.jpg.1cc160070ac9245cbbec687bf1f5f852.jpg

 

7.3L 538 lbs

Coyote 404 lbs

Diff 134 lbs. 

 

Now the good news is the 7.3L is much more compact vs the 5.0L. 

 

Ford didn't spend all that money going aluminum to save 750 lbs on a F150 crew just to throw in a iron block. But who knows... all speculation. The last iron block in a half ton? MY2014 F150 w 6.2L which outside Raptor was max 5% of sales?  

 

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14 hours ago, Power Kid said:

But would they make a 6.8L with iron and aluminum block. Not likely. And unlike the 6.2L which lived in F150 and SD for 4 year overlap I don't think they will put an iron block in a F150 today. Too heavy. And aluminum block in a SD would melt like butter in Az summer.  Would never handle the tougher SD durability testing. Same reason no EB in a SD or a 6.2L gm in a gm HD.

Sure, because All other aluminum engines melt in AZ.

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4 hours ago, Power Kid said:

In that case I guess aluminum blocks would work great in HD trucks. You win. Have a great day. ?

The robustness of cast iron and CGI blocks is undeniable in HD and MD applications,

no manufacturer would ever dream of using an alloy block in that application but not

for the reason that you’d imagine, they’re just not needed for light weighting or the heat

transfer. Point is that an alloy block is superior to cast iron in drawing heat away from

cylinders, you dont want that for efficiency. Keeping some heat in the bores but drawing

it away by using alloy cylinder heads is the key.

 

Ford’s 7.3 is a no nonsense practical approach to what is needed and what buyers want,

big capacity V8s that works well under constant heavy load and  more fuel efficient than

a smaller turbocharged gasoline engine. 

Edited by jpd80
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On 8/20/2021 at 7:35 PM, Power Kid said:

But would they make a 6.8L with iron and aluminum block. Not likely. And unlike the 6.2L which lived in F150 and SD for 4 year overlap I don't think they will put an iron block in a F150 today. Too heavy.

Properly engineered iron blocks today are much lighter than they were 30+ years ago.

 

Some of the cast iron exhaust manifolds look like "shorty" tube headers !

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I would not worry too much about aluminum block melting in medium duty. I think the real issue is fatigue life! Cast iron or CGI is vastly superior for  fatigue life!

There must be more with Ford choosing 6.8 over 7 liter like 429 cid for such small volumes in F150 and Mustang? 429 versus 414 cid is almost insignificant except from a marketing perspective, 429 would of worked better!

I just wonder if CO2 footprint of the 6.8 with dynamic skip cylinder deactivation is equal to the CO2 footprint of the high output 3.5 Ecoboost????

Also the rod to stroke ratio is about 1.57 to 1 on the 7.3

It is unlikely the 6.8 deck height will be any different than the 7.3.

edselford

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On 8/20/2021 at 7:35 PM, Power Kid said:

But would they make a 6.8L with iron and aluminum block. Not likely. And unlike the 6.2L which lived in F150 and SD for 4 year overlap I don't think they will put an iron block in a F150 today. Too heavy. And aluminum block in a SD would melt like butter in Az summer.  Would never handle the tougher SD durability testing. Same reason no EB in a SD or a 6.2L gm in a gm HD.

 

The 2.7L EB uses an iron block with an aluminum skirt. Just sayin'.

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20 minutes ago, Power Kid said:

Well the word iron is used.... but the 2.7L uses a CGI block. Different animal. Strong and light but costly vs old fashioned iron.

 

Shh..don't even say it... like Beetlejuice...if you say it three times... someone will appear...and you don't want that...lol.

 

image.png.ece718bd7188cbe52b86ce98e6114125.png

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10 hours ago, edselford said:

I would not worry too much about aluminum block melting in medium duty. I think the real issue is fatigue life! Cast iron or CGI is vastly superior for  fatigue life!

There must be more with Ford choosing 6.8 over 7 liter like 429 cid for such small volumes in F150 and Mustang? 429 versus 414 cid is almost insignificant except from a marketing perspective, 429 would of worked better!

I just wonder if CO2 footprint of the 6.8 with dynamic skip cylinder deactivation is equal to the CO2 footprint of the high output 3.5 Ecoboost????

Also the rod to stroke ratio is about 1.57 to 1 on the 7.3

It is unlikely the 6.8 deck height will be any different than the 7.3.

edselford

They could just call it a 429 and give Car and Driver something to write about.  How many people do you think would actually do the math and figure it out?  And if they did, even care?
 

I thought the same thing on the 3.5 EB running no boost vs 6.8L running on 4 cyl.  The fuel efficiency numbers are probably pretty close.

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4 hours ago, slemke said:

They could just call it a 429 and give Car and Driver something to write about.  How many people do you think would actually do the math and figure it out?  And if they did, even care?
 

I thought the same thing on the 3.5 EB running no boost vs 6.8L running on 4 cyl.  The fuel efficiency numbers are probably pretty close.

It’s not, the 3.5 EB will give better highway gas mileage.

Without cylinder deactivation, you’re looking around 16 mpg,

you’d be hard pressed to get 5 mpg improvement with cylinder deactivation.

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10 hours ago, jpd80 said:

It’s not, the 3.5 EB will give better highway gas mileage.

Without cylinder deactivation, you’re looking around 16 mpg,

you’d be hard pressed to get 5 mpg improvement with cylinder deactivation.

Maybe empty, 6.8 should get better MPG towing as the 5.0 does.

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