I had a unique opportunity last week: I took my 7.3 pulling my work trailer (36.5 feet, 24k trailer at about 34k gross), very aerodynamic) and my FL120D Freightliner flat-top w/DDEC IV on 435 setting pulling a 42' empty tanker (about as aero-INefficient as you can get) from the same place, to the same place, running exactly the same route and speed (65, always within a few vehicle lengths of each other). It was about 700 miles, so there was a pretty good chance to make a valid comparo of fuel use. Would you believe the Freighty took just $20 more to fill than the 450?? I have long suspected that they were pretty close under these circumstances, but this pretty well settles the issue. I usually come in around 8.0 towing (started in the 6s before mods) with the Ford - which does not impress me at all, but I am more than a little pleased that I can get the same mileage with a (light) class 8!!
7.3 fuel consumption:
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pat i have spoken with a few folks in rv parks that onece pulled with lightduty trucks,and now bumped up to the big trucks,not mediums,but full deal big trucks.all say that when towing of course the fuel mileage on the bigger trucks is better than that of the smaller ford or dodge trucks they replaced.
The 7.3 is a short stroke high RPM engine, especially with the gears that are in your F550. Probably about the worst setup you could put together for fuel efficiency. Shame on Ford.
The FLD has a long stroke low RPM engine. Very fuel efficient. The S60 is very good on fuel.
What you need is a better gearing and a real diesel engine in your F550. A Cummins 8.3 with a 3.42 rear axle would be about right.
The FLD has a long stroke low RPM engine. Very fuel efficient. The S60 is very good on fuel.
What you need is a better gearing and a real diesel engine in your F550. A Cummins 8.3 with a 3.42 rear axle would be about right.
Actually, I have a 450, changed over to 4.30 axles and with a 0.8555 aux OD (for an effective 3.68 final drive ratio). That is a bit over 1900 RPM @ 65 mph - hardly short gearing (the DDEC is turning just under 1800 at the same speed). I saw no measureable change in fuel economy by re-gearing from 4.88, all improvements have come by managing airflow and fuel control. I SHOULD have given it more advance a long time ago (4k or so mod), but keep leaving things alone as I test other mods one at a time.
Just to put the economy (or lack of same) into perspective: I get about the same fuel mileage with my D220 Iveco with a little 5.4 litre screaming its guts out (and no charge air cooler) pulling the same trailer, down the same road at the same speed as I can from the Ford running dead empty (as in bobtailing)!
But, the Series 60 IS remarkably fuel efficient. It also has run 1.4++ MILLION kms without any work on the drivetrain of any kind. Can't say that for the 450 - not even close. I am hesitant to call the 450 or 550 a light truck, because they are really on the small end of medium duty. However, to consider them anything even vaguely related to commercial quality is definitely wrong. Other than the fuel mileage, though, I have at least moved the overall truck from completely unreliable to something that will complete most trips, but at pretty high maintenance and operating costs.
Pat
Just to put the economy (or lack of same) into perspective: I get about the same fuel mileage with my D220 Iveco with a little 5.4 litre screaming its guts out (and no charge air cooler) pulling the same trailer, down the same road at the same speed as I can from the Ford running dead empty (as in bobtailing)!
But, the Series 60 IS remarkably fuel efficient. It also has run 1.4++ MILLION kms without any work on the drivetrain of any kind. Can't say that for the 450 - not even close. I am hesitant to call the 450 or 550 a light truck, because they are really on the small end of medium duty. However, to consider them anything even vaguely related to commercial quality is definitely wrong. Other than the fuel mileage, though, I have at least moved the overall truck from completely unreliable to something that will complete most trips, but at pretty high maintenance and operating costs.
Pat
Sorry about calling your 450 a 550.
So tell me this. Your 450 is more aerodynamic and lighter than the FLD. What sort of mileage would you get with a S60 (or S50) in the 450 ? Not that you could put one in, but if you could.
I assume the 450 is the correct size for the work you do ? I'm curious. What makes you say that the 450 has high maintenace and operating costs ?
So tell me this. Your 450 is more aerodynamic and lighter than the FLD. What sort of mileage would you get with a S60 (or S50) in the 450 ? Not that you could put one in, but if you could.
I assume the 450 is the correct size for the work you do ? I'm curious. What makes you say that the 450 has high maintenace and operating costs ?
The 450 is a LOT cleaner than the FLD120 aerodynamically. I use the 450 (or could do 550, but the reason I didn't was that the only difference is the rear axle and springs - and I wanted to be able to change ratios and it is on air anyhow) is because at the time the SD was the ONLY 4x4 in it's weight range on 19.5s, and that is the largest wheel that would fit under my trailer. Even now, the frame on the GM 4500/5500 is too high (in either 4x2 OR 4x4 configuration). The Iveco is probably the benchmark: it gets about 13 mpg towing the same trailer, so I doubt I could do any better with any engine in the Ford. I have had about those results with my Mitsu 6D14T conversions of F350s as well. If I were to do anything at all with this thing, I would probably go with a Mitsu 6D16T and a 9 speed Fuller and divorced xfr case - but the weight would be quite an issue. Might as well just build a real truck instead of trying to turn a sow's ear into a silk purse.
The Ford has used brakes (pads & seized caliper - even WITH the S-B installed rock guard), ball joints (there is NO added load on the front axle, 5th wheel right over rear), various engine parts, injectors, several clutches (hub failures), two gearboxes (pilot brg failures - that cost the whole gearbox) three rear gearsets (location of vent - putting water in the diff), one rear diff and both rear axles (FoMoCo incorrect torque bias on TrueTrac) - all in a measly 140k miles. The HVAC and parking brake have NEVER worked. The gearbox ratio selection is useless (requiring development of Aux OD splitter with the right ratio). On top of that, add thousands of dollars and hundreds of hours to develop and test fuel system mods to make it actually run at all. What can I say? It is not reliable. In fact, it is the least reliable vehicle I have encountered in 40 years as a mechanic, service manager, dealer, operator, etc.
The Ford has used brakes (pads & seized caliper - even WITH the S-B installed rock guard), ball joints (there is NO added load on the front axle, 5th wheel right over rear), various engine parts, injectors, several clutches (hub failures), two gearboxes (pilot brg failures - that cost the whole gearbox) three rear gearsets (location of vent - putting water in the diff), one rear diff and both rear axles (FoMoCo incorrect torque bias on TrueTrac) - all in a measly 140k miles. The HVAC and parking brake have NEVER worked. The gearbox ratio selection is useless (requiring development of Aux OD splitter with the right ratio). On top of that, add thousands of dollars and hundreds of hours to develop and test fuel system mods to make it actually run at all. What can I say? It is not reliable. In fact, it is the least reliable vehicle I have encountered in 40 years as a mechanic, service manager, dealer, operator, etc.
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Technically, long-stroke vs. short-stroke has to do with stroke to bore ratio. If the stroke is greater than the bore, It's a long-stroke engine. If the stroke is less than the bore, short-stroke. If bore and stroke are equal, some refer to it as "square".
Technically speaking, the 7.3 with its 4.11" bore and 4.18" stroke is a long-stroke engine.
A friend of mine once told me about The compressor engines at the natural gas compressor station where he worked. They have a 17.5" stroke. Long-stroke? Nope. 18" bore.
Re: high speed.... Generally speaking, Diesel engines that have operating speeds over 1200 RPM are considered high speed Diesels. Those that operate between 300 and 1200 RPM are considered medium speed. Those that operate under 300 RPM are considered low speed.
Truck engines are high speed Diesels.
Technically speaking, the 7.3 with its 4.11" bore and 4.18" stroke is a long-stroke engine.
A friend of mine once told me about The compressor engines at the natural gas compressor station where he worked. They have a 17.5" stroke. Long-stroke? Nope. 18" bore.
Re: high speed.... Generally speaking, Diesel engines that have operating speeds over 1200 RPM are considered high speed Diesels. Those that operate between 300 and 1200 RPM are considered medium speed. Those that operate under 300 RPM are considered low speed.
Truck engines are high speed Diesels.
Dave:
I would use the terms "oversquare" and "undersquare" for the bore/stroke relationship. I have always considered stroke by it's absolute length. That being said, I am not really sure WHERE I would make the division between "long" and "short". Maybe it should be above and below square.
Pat
I would use the terms "oversquare" and "undersquare" for the bore/stroke relationship. I have always considered stroke by it's absolute length. That being said, I am not really sure WHERE I would make the division between "long" and "short". Maybe it should be above and below square.
Pat
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