All kinda new to me:) 02' F250 PS7.3L
 

HI All,
Just discovered this site and all I can say is "WOW" Thumbs up to all of you and your incredible MPGs. I've always loved cars that had high performance and low fuel consumption. My classic example was back in the early 80's comparing the 911 to the Corvette. I went for the 911! Race car when I wanted and still hit 30+ cruising down I-95 to Florida!

But my current ride, 02' F250 crewcab long bed (22ft stem to stern) 4x4 7.3l diesel isn't in anyway a sports car but it is an incredible towing machine. I routinely get 16 when towing my 26ft MacGregor sailboat, about 2200lb total trailer weight and the truck bed loaded. 16 is on I-95 south of WDC, north through PA, NY and up to Maine I get about 15. Not towing about 17-19. Oh and I never exceed 65mph, the momentum of this rig just scares the hell out of me should anything go wrong:eek:

Question: I have a tall ARE cap, which is nice but not absolutely needed. I'm sure there is a huge suction back there since the rear of the truck looks like a 7ft high, 6 ft wide vertical wall.
Any thoughts on switching to a simple bed cover? Up to this point I've kinda thought the cap gets the air over the front of the boat and helps the mpg while towing.

The bow of the boat is about 2 ft higher then the tailgate. I wouldn't mind optimizing the aero for towing since better than 50% of the time it is towing.
Thanks
Ed

Welcome! That's not too bad of a towing mileage figure.

There have been several posts on cleaning up full sized PU's

Dig beyond the 1st page of the Aerodynamic section, and I'm sure you'll find
gold nuggets in there!

Can't imagine a two foot F250 towing much of anything? :confused: ;P

If the boat is above the tailgate I'd say it's a safe bet the topper helps more than hurts, and also helps more than a tonneau. But then the question is, is that boat back there all the time or just once in a while? Then the tonneau MIGHT be better than the cap, but that may be a YMMV thing.

Larrybuck- Yes I have been digging but I haven't seen my situation, although somewhere I saw a kind of pop-up aerocap that might work nice.

FrankLee- haha maybe at two feet it would handle more like a sports car than a bus:) I am thinking the same thing about the cap. I'm towing a good 40-50% of the time.

Big Dave is your new friend.

The tall cap would come off of my truck. Mine is cab-height and follows body contours but a 3/4's or full headwind makes it a problem. In a tailwind, though, it may actually help a bit.

A hard tonneau would be better, but an AEROLID would be best.

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It is pretty tough to project a good effect from the truck with conventional trailers, and much worse with something like a sailboat.
The distance between the two rigs makes them behave largely like two separate rigs.
If you only lose 3 MPG towing I'd say it is not a good pursuit in my opinion. Better to reduce the truck as slowmover says, and see what that nets you. I would go with a full aeroshell.
Nice toy by the way, I love sailing.:thumbup:

Hi skyking,
I just checked out your diesel truck mpg. How are you driving that you get up to 26mpg? Or is your truck just that much more efficient than my F250? I drive pretty conservatively e.g. rarely exceed 62 mph(GPS not speedo), and my best cruise down I-95 in pretty flat country is 19mpg.

skyking, slowmover An aerolid would be sweet but it's not in the near term. If I had time to do one thing would a deep air dam or a duck tail have better FE effects? Or something else?
Thanks
Ed

How are you driving that you get up to 26mpg? Or is your truck just that much more efficient than my F250?

Some of us have genuine diesels, the rest wish they had a Cummins. (Click on the Fuel Log link below my signature). And we have another member who walks on water . . little boys like Skyking and me are barely able to stay within 70% of what he & his Cummins can do.

Ed-in-Maine, kidding aside, I recommend you do a search of all threads started by Big Dave as his 7.3L Ferd is a great template of ideas for your truck. I'd PM him after a thorough read of those threads, and then of his other posts here (he also posts extensively on Ford forums). For dollars and cents experience, he's your man (to get things started). Until quite recently no one else had numbers even close to his.

The real money is in driver training. Costs nothing & pays the biggest returns. Plus, no matter age or vehicle there is always more to learn: I hit a nice marker this past week as shown in this thread where the modified driving I was doing was again modified in light of newer (better) information.

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Welcome! As a Cummins guy, I probably should take a shot at the new Ford guy, but I'll be nice. ;)

If you've got a detailed aero question Phil Knox, a.k.a aerohead, is the guy to ask. I'm not an aero expert, but I'b be inclined to get rid of the tall cap if you don't need it. A lower cap would definitely be better than the tall one. Lower vs. tonneau is debatable, depending on the dimensions of the boat (consider putting some pics up for us). My first inclination would be to go for the tonneau, or an aerocap (in the ideal world).

My opinion is that a belly pan is preferrable to an air dam, however, it's much more work. I have yet to do mine.

Overall, driving modifications are almost always where the biggest gains are. That being said, you won't have as many options with an automatic tranny.

Thanks Diesel_Dave et. al.
I have weeks of information to dig through. Already some of my long set beliefs are being chipped away. Just for reference, my last real interest in cars as more than a toaster was 20 years ago when I raced SCCA IT RX7. So I'm shocked when I read "Over inflate tires". I suppose tire tech has changed radically. I still have the pyrometers for checking tire surface temps and over inflation as well as under lead to all kinds of nasty results. IIRC we were running radials but they still would bulge wear out the middle and get skittish as hell.
Ed

Ed, your truck is a 4x4, at least 5" taller than all of our trucks. Note that we all have 2wd.
Now add your taller-than-cab topper, and you have a bigger, square wake to contend with. I think you are doing well with the equipment you are working with. Big Dave has 2wd and has lowered his truck, added an aeroshell, front skirt, etc. to get where he is at.
I've never seen a V-8 diesel truck get as good on average as an I-6 either.
I think you could reduce by 10% with a 4' long folding boattail on the current setup. Hang some cheesy tail lights on it and fold it back up when you get where you are going, or put it inside the topper.

I wouldn't over-inflate.

My mpg numbers reflect pressure-vs-load; staying inside the factory numbers (and working off of a MICHELIN Load Range E tire pressure chart). Braking and handling are adversely affected by too much pressure for the load being carried. My wear rate is consistent with 120k life on the tires (or longer).

The mpg "trick" on tires is casing and tread design as you know. Highway rib (closed shoulder) being best. A website by one of the members here is full of good tire info (CapriRacer), and he chases down some of the myths around tires to some depth with our concerns. So, even if knowledgeable about tires, Barry's Tire Tech is full of good reading. There's bound to be a "best mpg" tire for a 4WD truck in Maine that spends 50% of it's miles on the highway.

I work from certified scale numbers: "empty" truck (as is; solo, with driver, full fuel and normal stuff aboard) to "loaded" (trailer hitched and weight distribution both activated and inactivated) to find the range I need to keep in mind. The FF axle tire pressure remains constant, and the RR axle tire pressure is increased 15-psi from solo to towing (at present).

A certified three-pad scale is a great place to start, IMO, for understanding changes to the truck.

Looking forward to what you have to say on tires as 4WD trucks aren't well addressed on any forum when it comes to: tire life, performance and mpg. Seems a racer ought to be the one to nail that down.

The MICHELIN A/T2 and BRIDGESTONE Duravis m700 series have good reports as to very long life and limited offroad from those participating on commercial operator forums (and, locally, oilfield hotshot); what I would use as a starting point.

. . 26ft MacGregor sailboat

Their website indicates 2,550-lbs empty. A trailer adds 600-900-lbs [?], and then add for boat load plus truck bed load. Looks like 4,000-lbs spread from boat/trailer and truck is a fair-estimate starting point (maximum). The upgraded aluminum trailer with torsion-arm suspension, surge-type disc brakes and 200-lb weight savings is all mpg-friendly as road performance, towing, is a matter of concern.

Quite a cool boat from the descriptions offered.

http://www.macgregor26.com/trailerin...inum_large.jpg

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skyking- Yep I'm seeing that all diesel tucks are not the same but heck a big old 4x4 Aero would be pretty cool:D I think my goal will be 25 on highway at 60mph. I did order a Scanguage to get real-time data. I've been doing tank mileage calcs for decades but never had real-time. That gauge will be worth the cost just for the fun factor:D

slowmover- After more searching it seems there is one group who think putting the tire to max sidewall pressure is "over inflating", then a group who seems to actually be exceeding the sidewall pressure and others s let the confusion reign. But I don't think I'll exceed sidewall pressure, I figure the engineer who came up with that number knows a whole lifetimes worth more about tires than I do.

I'll probably slap a set of the LRR tires on next time around but my Kelly's with giant lugs are anything but LRR.

Using a scale is very cool. I used to set static corner weight like that, but for the truck I've only used the IR Pyrometer. When towing, and when not but I really try not to drive the truck unless it's loaded, at every leg stretch or potty break I walk around the truck and check hub temps then tire tread temps -inner-middle-outter on both truck and trailer. Takes just a minute.

My boat is the old 26S which is much more sailboat less motorboat and it weights a bit less.


Since we're visiting for the month in Annapolis MD with limited tools now my first aero mod is going to be a simple airdam.

I tried to upload a pic but it's not letting me. The current factory air dam is about 15" off the ground.
Ed

Ed, the boat tail could stay on with the boat in tow as well. It would be over the tongue and out of jackknife range, I believe.

Just be careful about using the Scangauge with a diesel. Some diesels(including mine as I recently found out), don't report direct fuel flow over the scan port. The only "option" you have is to use mass-air-flow based fuel flow estimates which, in my opinion, are complete trash.

Diesel_Dave: thanks for the heads up. Sure will be bummed if I can't get gph. Oh well it can always go in the Matrix, but it already gets good mpg.
Ed:turtle:

Some do, some don't. I know a guy with an older California Cummins that it works on, however, it doesn't work on mine. It all depends.

I'm not ready to give up yet, however, I still have a few other tricks up my sleeve.

WooHoo!! The scanguage is in and seems to be working! Just a short drive and questions, questions. The MPH seems to read higher than the speedo, which reads slower than GPS:confused: I know car makers generally calibrate speedos to run slow but how is the OBDII getting a faster speed? Must be calulated and my tires are not the stock diameter.
The most important value to me GPH seems spot on. I was suprised at the over 1gph when cold at idle. This gives credance to get the car wamed up quick as possible.
Ed:turtle:

What PID is it using for fuel flow? 015E? Supposedly that's the direct fuel flow (not MAF based).

Diesel_Dave, my ScanGuage has a PID "all" setting and diesela setting for fuel. My cold gph was about 1.75 which dropped to 0.44 gph after about 7miles driving. I haven't done the calibration yet but these number don't seem severely off. Doing a web search it looks like the 7.3L PowerStroke uses about 1/2 gph at warm idle.

Seeing that high cold number already got me to put a radiator block on(not really tested yet) and I've started shifting to neutral at stop lights since now I SEE the savings :D This ScanGuage is seriously one cool toy:thumbup:
Ed:turtle:

Had this thread pop back up on my CP at CF Rail Pressure for the ScanGauge II! - Dodge Cummins Diesel Forum