7.3L to 6.7L comparison

[HMS_Beagle]

I replaced my '99 7.3L with a '15 6.7L recently. The two trucks are as identical as you can make from the order book: Supercab F350 dually 2WD Lariat 3.73 gears. For several years I have made the drive from home to Lake Tahoe, making this trip perhaps 40 times with the 7.3L, so I am quite familiar with the grades, fuel mileage expected, etc. The road climbs from sea level to 7200 ft Donner Summit and then drops into the 5900 ft Truckee valley, 165 miles each way. I set the cruise control on 63 when traffic allows. Hauling a 4300 lb Bigfoot 10.4E.

With the 7.3L, there were 13 grades which required a downshift to 4th. Practically this also meant dropping the speed to 55 due to the engine roar from the big gap between 4th and 5th. After crossing the flat Central Valley I would have about 15 mpg on the meter, maybe 16 if there was a tailwind. By the summit, this would have dropped to 12, sometimes 11.9, then picks up a little going down the other side. On the downgrade into Truckee, I had to downshift out of overdrive and ride the brakes a bit to keep the speed under control.

Today was the first opportunity with the 6.7L (also, the first trip with the air suspension - but that is another topic!). The gearing in top gear is pretty much identical to the 7.3L, but with 6 speeds spaced better in the transmission. It managed the whole climb in 6th on cruise control without apparent effort, no downshifting, no noise, no fuss. From the gages, it was working a bit, EGT peaked at 910 deg, oil temp at 242 (oil is designed to run hot in these engines), boost about 30 PSI on the steepest grades. Quite relaxing by comparison to the 7.3L. There was plenty of power to spare to pull back up to speed if I got caught behind a truck.

I had about 16 mpg on the meter when I hit the grade, it was down to 13.2 at the summit. Both trucks are about 1 mpg optimistic when checked by hand. On the downgrade into Truckee, the exhaust brake kept the speed at the cruise control set point though it did have to downshift to 5th to do it. No brakes required.

These new Superdutys are sure complicated and expensive - but they sure are nice!

[jimh406]

If you are out of warranty, you should consider aftermarket for radiators and turbos. You still need a mechanic.

[SoCalDesertRid1]

The aluminum core and plastic tanks of Ford radiators should be outlawed. I've replaced them on every late model Ford I've had. Only 1 lasted beyond 100,000 miles.

[HMS_Beagle]

That makes the $1500 spent on the 7 year bumper to bumper warrantee seem worthwhile.....

[camr]

ClassicB wrote:
There's no doubt the new F350's are nice and powerful but I will hang onto my bullet proof 7.3 as long as I can. Wait until you have to throw a new radiator into your tuck at 40K miles.

My 2011 F-250 split it's rad at 41000 miles. I left the dealership $2000 poorer. When I asked the service writer how common this issue was, his reply was, "A lot more common than Ford would ever admit." His theory was that the frame flexing was contributing to the separation of the core and bottom plastic tank. The leak is almost always at the drivers lower side.

[Area13]

I got to admit, i'm a little jealous! I have heard nothing but good about those 6.7's, sweet trucks! Almost sounds boring to drive they're so capable!

Unfortunately my current income structure only allows a new camper and a new boat, no way I can budget one of those beasts in at this time....

That being said, thank god I have a super reliable, long lasting, almost maintenance free, extremely capable, old, stinky, loud 7.3. It's my baby and I love it anyway!

Congrat on the new truck, sounds like a winner.

[HMS_Beagle]

I just came back from Lake Tahoe on the return trip. The 6.7L pulled the east side of Donner Summit in 6th without breaking a sweat, peak EGT a bit less than 900. Fuel mileage listed on the lie-o-meter as 15.0 for the round trip, about the same as the 7.3L (again, both are optimistic by about 1 mpg). That included a partial regen, I stopped for lunch which stopped the regen about half done.

[Airstreamer67]

I can guarantee they were hotter than 910F on the 7.3, probably more like 1200F if mine is any guide. I'm amazed the 6.7 can perform like that and peak at 910.

[HMS_Beagle]

This is interstate 80, there aren't any "steep" grades. The worst of them are marked 8 percent I believe as you come the other way. On the "steepest" 13 of them, the '99 had to downshift. I did not have it instrumented to know what the EGTs where.

[jimh406]

HMS Beagle, I guess the next question is where are you calling a steep grade? 🙂

[HMS_Beagle]

Old-Biscuit wrote:
You posted:
From the gages, it was working a bit, EGT peaked at 910 deg, oil temp at 242 (oil is designed to run hot in these engines), boost about 30 PSI on the steepest grades.

EGT peaked at 910*F???

DO you know where that was monitored.......PRE or POST Turbo.

Sounds LOW for PRE Turbo given 30# boost

According to the Ford description:

The EGRT11 sensor monitors the exhaust temperature leaving the exhaust manifold prior to entering the turbocharger turbine housing and EGR cooler.

EGRT11 is the one that gets hottest except for during regeneration. That is the one that peaked at 910. The other three are down the exhaust system at various locations and normally run cooler the further on you go.

[Old-Biscuit]

You posted:
From the gages, it was working a bit, EGT peaked at 910 deg, oil temp at 242 (oil is designed to run hot in these engines), boost about 30 PSI on the steepest grades.

EGT peaked at 910*F???

DO you know where that was monitored.......PRE or POST Turbo.

Sounds LOW for PRE Turbo given 30# boost

[Vinsil]

I use an Edge to monitor, but the phone apps work great.

Good rule of thumb on turbo's is to let it idle down 1-2 min before shutdown IF you just got done working it hard...ie, just pulled a large pass, passing other vehicles...etc. But good idea to watch it cool down, some apps and monitors will do a cool down that will idle the truck and when shut down at a temp you set.

[Jimster]

Beagle and Jimh425: Thanks for your fast replies. I've got an iPhone 6S, so will look into ForeScan. Getting our new Arctic Fox 811 loaded onto the truck tomorrow morning, and I'm interested in watching the EGT to determine whether I need to spin down the turbo when I'm starting and stopping frequently for bird watching.

[HMS_Beagle]

Jimster wrote:
Beagle, I just picked up a 2016 F-350 Dually with the 6.7 engine and would like to monitor EGTs. How do you do this? I can't find an EGT display in the truck's display system. Thanks

You can get an Edge or other dedicated device, some of them allow manually starting a regen which might be occasionally convenient. Torque Pro seems highly featured (Android only). I use ForeScan Lite on an iPhone 6+, I believe versions exist for Android as well. These solutions require an OBD scanner, cheap ones are in the $10 - 20 range, good ones cost more like $80. The apps are cheap, like $5.

The advantage ForeScan has for a Ford, is that it is written and maintained as a Ford specific application so it already interprets all of the PIDs etc. from the ODB port. Torque Pro requires configuration, there are some resources on the web to give you a head start. ForeScan is plug and play pretty much. It allows capturing the data being monitored as a CSV file which can then be massaged in Excel, which is what I did to create the graph above.

All of them allow reading out the check engine trouble codes (and resetting them) which can save you $100 at the dealer.

[jimh406]

Jimster, you can either buy a full on metering system like an Edge Insight Monitor or buy a "good" bluetooth connector to plug into your OBD port. Then, you can use an application like Torque Pro to monitor whatever you want with your Android device. This is the part for an Android, for instance.

OBDII Reader for Android

There are also applications for iphone.