5.4 fuel efficiency

[chevypower]

Yeah the 5.4 is not efficient even by V8 standards. My 2005 F150 5.4 (3 valve) averaged 13.5 mpg combined. True average. 15-16 highway. Best ever 19mpg in certain conditions. The Chevy 5.3 Silverado is much more efficient but doesn't have the low end pulling power of the 5.4. I think what makes the Ford Modular V8s so inefficient is the really long stroke (high piston speed and friction) and the SOHC design (more moving parts).

[kypez]

Originally Posted by chevypower

Yeah the 5.4 is not efficient even by V8 standards. My 2005 F150 5.4 (3 valve) averaged 13.5 mpg combined. True average. 15-16 highway. Best ever 19mpg in certain conditions. The Chevy 5.3 Silverado is much more efficient but doesn't have the low end pulling power of the 5.4. I think what makes the Ford Modular V8s so inefficient is the really long stroke (high piston speed and friction) and the SOHC design (more moving parts).

The XR8 is quad cam though

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[FPV8U]

My XR8 pre tuning was also better on 95 than 98 to back up what M&M's posted, now it gets 98 all the time as that's what it's been remapped for.

I average 10.1-10.2L/100km on Hwy and 16ishL/100 around town.

[chevypower]

Originally Posted by kypez

The XR8 is quad cam though

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Which is even worse, because that has a lot more moving parts. BTW, on a V-shaped engine, "quad cam" is the same as saying DOHC. That is why I think the Lincoln Navigator got rid of that engine for the SOHC version. Too inefficient and no real benefit.

[smoo]

Originally Posted by chevypower

Yeah the 5.4 is not efficient even by V8 standards. My 2005 F150 5.4 (3 valve) averaged 13.5 mpg combined. True average. 15-16 highway. Best ever 19mpg in certain conditions. The Chevy 5.3 Silverado is much more efficient but doesn't have the low end pulling power of the 5.4. I think what makes the Ford Modular V8s so inefficient is the really long stroke (high piston speed and friction) and the SOHC design (more moving parts).

I think for the sohc to come into their own they need weight behind them, similar to a decent turbo diesel. How does the 3V go against the Chev 5.3 loaded?
My old 3v Fairlane used less gas and towed much more effortlessly than my old BA Fairmont 4.0.
It never saw better than 9l/100km and I'm sure an LS1 in a commodore onnthe highway will beat that, my old BMW 540i could return mid 8s in a trip.
It was a while ago but my first impression when towing with my FG XR8 ute was that the 3v Fairlane could do it a lot easier.

As far as the boss and in effiencies go, I have a V12 S Class Mercedes that weighs 2.3 tonne with one less gear and same power out put as the 290 boss and it will return the same fuel figures as my XR8 ute 10.5-11 per 100km highway.

[kypez]

Originally Posted by chevypower

Which is even worse, because that has a lot more moving parts. BTW, on a V-shaped engine, "quad cam" is the same as saying DOHC. That is why I think the Lincoln Navigator got rid of that engine for the SOHC version. Too inefficient and no real benefit.

Yes... I'm well aware of that...

And I don't think it's reduction of cams was the issue. Look at the coyote/miami engine and how much over it's weight it punches... Sadly we missed out on VCT on the exhaust but the U.S. Spec ones get it...

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[Whitey-AMG]

Originally Posted by chevypower

Which is even worse, because that has a lot more moving parts. BTW, on a V-shaped engine, "quad cam" is the same as saying DOHC. That is why I think the Lincoln Navigator got rid of that engine for the SOHC version. Too inefficient and no real benefit.

SOHC will better suit low end HP torque / lower RPM
DOHC will better suit mid/high end HP torque / higher RPM

As others have said , the missed opportunity was for VVT on the DOHC Boss engines for exhaust ..... maybe it was planned for here in Australia by FPV over time but decided against . Not worth the investment.

I'm kinda guessing but I reckon there is no use for revving a Lincoln Navigator to 6500 - 7000 RPM hence the SOHC preference - right ?

Plenty of owners tuning their DOHC Boss powered cars and raising limiters to 6500 + RPM and making good power. 270 - 300 rwkw not uncommon with just bolt ons which shows what they are capable of.

The inefficiency however is at the lower RPM where the intake velocity / swirl is less than that of the SOHC 3V , hence it doesn't boogy down low as well.
Ironically it may be better going to a shorter diff ratio ( numerically higher ) to offset this as you can still retain top end with the higher RPM limit on the DOHC which can give you the best of both worlds. FPV may have decided against this as it would not have returned the better highway cycle mileage that they were after. Hence the short 1st gearing on the ZF to get it going but leaving a hole in the other gears until it reached 2500 + RPM. 3.2 - 3.5 rear end in the auto from factory would have been ideal as plenty of owners me included don't care about the economy on highway for the extra 10 bux it would chew.

Either way, neither the 3V nor the 4V naturally aspirated engines can be classed as frugal when they need to haul around 2 ton + bodies without the aid of some boost.

[chevypower]

@Smoo, it's been a few years since I have pulled a trailer with a 5.3. It does the job, but feels like it struggles up hills while pulling. It's all relative though isn't it? The 5.4 feels much better with better torque and throttle response. The 5.3 is smoother and quicker unloaded and likes to rev. The 5.4 is harsh and loud at WOT. The EcoBoost V6 makes them both feel gutless when pulling or empty!

[M&Ms]

The heads on the 5.4 Quad Cam are designed for supercharged applications; they are massive and you just can't get enough air in there for optimum efficiency, hence why they are quite doughy down low. FPV tried to cure it a little with the twin Throttle Bodies in the 315 version, and it made a difference, but still not perfect and still lacked decent grunt below 3500 RPM. Top end though, was a different story (I'm still adamant my old 315 GT wouldn't be much slower than my 335 XR8 at the top end)

[Kieron]

I actually thought the quad cam heads were primarily designed for performance versions of the virtually square 4.6L block which would have been a revvie little sucker able to make use of the 4 valves.

Throwing those heads on a longer stroker 5.4 was a bit of a mismatch and in FG XR8 form, you run out of revs real quick in low gears once she's spinning, the extra 500rpm on GT would be welcome.

Is the twin throttle body progressive? ie at low RPM, only one is operational and the secondary opens up at higher revs like a good ole 4bbl carb?

Out of interest, I have a pic of my trip/odo 107k's after the pic I posted earlier in this thread, the calculating the trip computer difference equalled 119k's making it optimistic by 12k's, that was driving home/work/home in peak hours. Can't complain with that and given what it is and the traffic conditions, i'd say the ole nail is pretty economical.

[Whitey-AMG]

Originally Posted by Kieron

I actually thought the quad cam heads were primarily designed for performance versions of the virtually square 4.6L block which would have been a revvie little sucker able to make use of the 4 valves.

Throwing those heads on a longer stroker 5.4 was a bit of a mismatch and in FG XR8 form, you run out of revs real quick in low gears once she's spinning, the extra 500rpm on GT would be welcome.

Is the twin throttle body progressive? ie at low RPM, only one is operational and the secondary opens up at higher revs like a good ole 4bbl carb?

Out of interest, I have a pic of my trip/odo 107k's after the pic I posted earlier in this thread, the calculating the trip computer difference equalled 119k's making it optimistic by 12k's, that was driving home/work/home in peak hours. Can't complain with that and given what it is and the traffic conditions, i'd say the ole nail is pretty economical.

Twin TB is not progressive. It's why you need a retune if you fit it up otherwise you get very high idle and hunting as it does suck a little more air down low and a lot more up high. 75mm. V twin 60mm.
However , what you notice is that being 2 smaller openings , I reckon it provides a faster velocity for the same given air volume , hence why the car can feel a bit more responsive .

I have the twin 60 and YT dual TB plenum on my Boss 290 and it did provide a worthwhile improvement in deiveability. Not huge but definitely noticeable. Combine that with an Airbox and a tune and headers and Hi flo cats etc etc etc
and you get exponential benefits with each modification that would probably go unnoticed on its own.

Interestingly enough ( to keep the thread on track ) I found no major fuel consumption change with all the stuff I've done over the years. Car has gone from 225 rwkw stock to over 275 now. Would probably be over 280 with hi flo cats as I still have the factory 400cpsi cats installed.

[290v]

my BA GT open road is 10.2L/100 around town it sits around high 13s per 100

[Bonn]

Am averaging around 11.0 combined, exclusively 98 - V-Power and Vortex, occasional Ultimate - never touch the 'discount' brands.