Review on the new 7.3 Ford V*

[wallaceb]

Interested in the latest comments/reviews from owners of the new Ford 7.3 V8 gas engine.

[Gjac]

ron.dittmer wrote:

mleekamp wrote:
I'd say it's more about the wind resistance than the weight of your RV that affects mileage....

I agree that the aerodynamics of the rig will influence the fuel economy. I am no expert, but I feel it could be nearly as influential as the over-all weight.

Some motor homes are flat-faced compared to others built on the same chassis. Then there is the size of the face. Some rigs are taller and wider than others. Given equal weight and identical chassis, a worse-case versus best-case scenario, you would see a change in fuel economy. How much? Who knows. But based on numbers shared over the years, I estimate a 10% difference.

A class C (B+) a best case scenario with aerodynamic cap, angled transition walls, narrow body, and lower roof.


I wish I could find a better worst case scenario, but here is something.

How much difference in mpgs or handling between a B+ aero front end and a C with the overhead bed? Does anyone have any data on this? I think it is logical to believe a B+ is better but how much better. The trade off is more room vs better mpg. If only 1 mpg I would choose more space. If the difference was 4mpgs 10 vs 14 mpg I might choose the B+.

[DrewE]

ron.dittmer wrote:

mleekamp wrote:
I'd say it's more about the wind resistance than the weight of your RV that affects mileage....

I agree that the aerodynamics of the rig will influence the fuel economy. I am no expert, but I feel it could be nearly as influential as the over-all weight.

Aerodynamics have a much greater effect on fuel mileage than weight for highway driving. On level ground and at a steady speed, the only effect weight has is to (slightly) increase the rolling resistance of the tires. Air resistance, on the other hand, make up the greatest part of the friction that must be overcome, and further it goes up tremendously with speed increases--it's proportional to somewhere around the cube of the vehicle speed, if memory serves.

For climbing hills, and for stop and go driving, the weight is relatively more of a factor than for highway cruising.

The aerodynamics of the rear of the vehicle are at least as important as those of the front. RVs generally are pretty terrible at both ends; a squared off back generates lots of turbulence and drag, which is why airplanes and Priuses tend to have pretty pointy backs.

[ron_dittmer]

mleekamp wrote:
I'd say it's more about the wind resistance than the weight of your RV that affects mileage....

I agree that the aerodynamics of the rig will influence the fuel economy. I am no expert, but I feel it could be nearly as influential as the over-all weight.

Some motor homes are flat-faced compared to others built on the same chassis. Then there is the size of the face. Some rigs are taller and wider than others. Given equal weight and identical chassis, a worse-case versus best-case scenario, you would see a change in fuel economy. How much? Who knows. But based on numbers shared over the years, I estimate a 10% difference.

A class C (B+) a best case scenario with aerodynamic cap, angled transition walls, narrow body, and lower roof.


I wish I could find a better worst case scenario, but here is something.

[Gjac]

alvinator wrote:
CaptJD wrote: Well, last Wednesday I've purchased a Thor Coleman 19CM and it came with that 7.3 engine.

The smallest Coleman Class C motorhome on their website is a 22CM. Where were you able to find a 19CM?

That model and size sounds like a rental unit that Thor makes.

[alvinator]

CaptJD wrote: Well, last Wednesday I've purchased a Thor Coleman 19CM and it came with that 7.3 engine.

The smallest Coleman Class C motorhome on their website is a 22CM. Where were you able to find a 19CM?

[Grit_dog]

btim wrote:

My E-450 I has the 4:10 rear end and 6 speed trans. At 65mph the engine is turning about 2300 rpm. The engine stays in the powerband in 6th gear at highway speeds so there is no downshifting for overpasses and bridges unless they have very steep inclines.

I forgot the de-tuned 7.3s still get the old 6 speed trans (5th and 6th basically like 8th and 9th in the 10 speed).

It's a decent pairing since the 7.3 has power for days.

If the OP's little van has 4.10s as well, I can see how he thinks it's getting high rpms at highway speeds though. But it should pull like a train!

[btim]

What rpms in 10th gear at 70-80-90mph?

My E-450 I has the 4:10 rear end and 6 speed trans. At 65mph the engine is turning about 2300 rpm. The engine stays in the powerband in 6th gear at highway speeds so there is no downshifting for overpasses and bridges unless they have very steep inclines.

[bobndot]

Curious what you mean by not much top end

What rpms in 10th gear at 70-80-90mph?

75-80mph 10 sounds about right.

Try to keep it under 115 mph ok ? :B

[Grit_dog]

CaptJD wrote:


It has so much torque but not much top speed IMHO. ... When I started for the first time and heard the engine I thought exhaust muffler was off. .

I feel I am not going to RVing but rather joining to a drag race every time I hit the ignition switch!
On a 19ft (20' overall) C class it gives me only 10mpg if I am lucky.

Sounds awesome!
It should have ALOT of torque in a lightweight vehicle such as yours.
Curious what you mean by not much top end. What gears do you have?
Even deep gears should still cruise very comfortably at WELL OVER freeway speed limits. What rpms in 10th gear at 70-80-90mph?

10mpg doesn't sound "bad" what kind of speeds? Cruising at 60-65, I'd expect more. 75-80mph 10 sounds about right.

[btim]

We bought a new Entegra Class C in December. Has the 7.3 motor. Only have 1,500 miles on it thus far but I am impressed with its power. The RV is almost 27 feet long and is 11'8" tall. Weighs almost 11,600lbs, with a GVWR of 14,400lbs. As a result there is considerable weight and wind resistance on the highway. I do not exceed the speed limit, and generally cruise at 65mph on the highway. Mileage has been about 9.5mpg. Towed a 4,ooolb car about 180 miles and still got just under 9mpg (all flat land thus far). Taking it out west this summer and will be towing a small car. Hoping to see 9mpg, but I know the mileage will drop in the mountains.
Overall the 7.3 motor has plenty of power for this size rig. I imagine it will be more than adequate in a smaller rig.

[mleekamp]

I'd say it's more about the wind resistance than the weight of your RV that affects mileage. 10 is very good. Pulling our toad or not, we get 7.5 mpg, and yes, that is the V10, not the 7.3 V8.

So 10 mpg is good to me!

[CaptJD]

Well, last Wednesday I've purchased a Thor Coleman 19CM and it came with that 7.3 engine...

I think it's a little overkill for that tiny motorhome but in any case so far I drove her from AR to CA via Southern route by El Paso due to bad weather along the N route.

It has so much torque but not much top speed IMHO. But again I am no expert. When I started for the first time and heard the engine I thought exhaust muffler was off. At home I drive a 3.5L EcoBoost engine Ford Transit 350 XLT. My poor XLT feels like Mercedes SL550 in noise comparison to the 7.3L V8...

I feel I am not going to RVing but rather joining to a drag race every time I hit the ignition switch!
Gas guzzler for sure. On a 19ft (20' overall) C class it gives me only 10mpg if I am lucky. A little bit of wind or uphill climb I am down to 8-8.5mpg.

I was expecting to get at least 12mpg or so on such a tiny C class but I guess it was wishful thinking on my part!
So far after 2200 miles not much to brag about. But today I've found Ford already issuing a recall on this engine and E350 bodies for some sort of heat shield issue I assume.
So waiting for the postman!