Driveshaft weight reduction - Fuel Economy, Hypermiling, EcoModding News and Forum

steve05ram360 · 07-21-2018, 03:31 PM

Swapped in an aluminum shaft today in my 2005 QC 4x4 2500,

https://www.cumminsforum.com/forum/3...iveshafts.html

Adding this for the next guy...

base tank, only one :-( Will fill up sunday and repeat a weeks worth of commute miles, Mon-Fri nite. Sorry, no ABA test, too many things going on. During my research on throttle response & aluminum DS's I did not find anything with this much detail so... here it is.

513.8 miles, 23.539 gal, 21.827 mpg
100% eco driving, IATs up in the 90's, IAT comp table corrected but timing not dialed back in.

479.3 miles, 21.095 gal, 22.721 mpg 100% eco driving, IATs up into the 100's. No tune changes. Tune needs to be adjusted, smoky after DS install.

DGAS tank 7/30/2018
319.1 miles, 16.172 gal, 19.731 mpg... Tuning tank, lots of downloads, experiments and hard throttle time. Tweeked rail maps slightly, main timing, cut duration by 2% and started working on Post timing. Advanced Post 0.25* in an effort to get the turbo spooled better, reduced the MM3 for Post and expanded its coverage up into the 2000-2200 rpm cells. Worked really well, ultimately I reduced fueling, advanced timing and gained more power out of it by reducing the delay from the Main event to Post event.

8/3/2018
472.8 miles, 21.056 gal, 22.454 mpg...

8/10/2018
454.5 miles, 20.153 gal, 22.552 mpg..

Old Shaft

new shaft

grswat · 07-22-2018, 08:53 AM

Every little bit helps. When I had my Dakota it had a 2 piece driveshaft and carrier bearing that was just stupid heavy. The newer ones had a 1 piece aluminum shaft. I always wanted to change it but never did.

steve05ram360 · 07-22-2018, 10:58 AM

You should have... it is a nice improvement. Have a full day of running around with it in and I like it. It is clearly a good change when driving in stop & go traffic and I think it will help out overall. Driving down to Portland for the day and dont expect to be kind to the pedal. This is a "dont care" tank, will be topping it off tonight and eco driving all week thru friday nite to mimic driving from last week. 21.8 mpg last week.

I actually tried to do a before & after data log of the swap but even early in the morning, traffic was too much to hold even 60 mph over the 10~13 mi drive. FWIW, I jump on the freeway roll up to 60 or 64 mph, set CC and let it do the work. Then grab the data and compare before and after calculated load values. pretty repeatable and shows changes. I do this when tuning. The route has a good balance of hills of various grades and and flats.

slowmover · 07-23-2018, 08:15 AM

Use of cruise control always “best “ for repeat results.

One “thinks” they can beat it only to learn the effort wasn’t worthwhile. Takes away from energy wanted for all other driving tasks.

For others not familiar with CTDs:

On our trucks, just set for 62-mph to get best 64-‘mph results. It’s an assertive, almost aggressive CC as the loads expected for the truck are high. IOW, it’ll do a better job by itself at 62 versus trying to run 64 on the foot.

High cylinder compression (aided by TC) makes Hill-flattening easy. The truck just walks it. The temptation is to cancel cruise to offset this. Easier to back off 2-mph for “best” results.

Baltothewolf · 07-23-2018, 10:17 AM

I mean mpg aside, back when I had my Mustang I felt a noticeable improvement in acceleration in the lower rpm ranges (especially from idle at a stop) when I went from big heavy driveshaft to a Ford racing aluminum one (about 1\3rd the weight).

steve05ram360 · 07-23-2018, 10:20 AM

So having another full day with it on a road trip to Portland, on a DGAS tank (don't give a ****), gave me my best mpg yet for any tank doing 75-85 mph coming in at 19.9 mpg. That tank did have me stuck in stop & go traffic for an hour or so. Behaving myself for the week until Friday's fill up after work, 100% eco driving.

Also, FWIW... have nothing to back it up but I feel like I've lost a tad bit of coasting abilities with the swap. Maybe its time to get back to solving the rear bumper parachute fix.

steve05ram360 · 07-23-2018, 10:23 AM

Quote:

Originally Posted by Baltothewolf

I mean mpg aside, back when I had my Mustang I felt a noticeable improvement in acceleration in the lower rpm ranges (especially from idle at a stop) when I went from big heavy driveshaft to a Ford racing aluminum one (about 1\3rd the weight).

I feel it in 3rd gear and up. While doing 70 and accelerating up to 80... it just plain spins up faster. Did not think the 13# drop would make that much of a difference but I was surprised the more I drove it and the different situations encountered.

steve05ram360 · 07-27-2018, 01:40 AM

driveshaft gave just under 1 mpg... retuned truck to fix a problem that appeared with the DS install.

steve05ram360 · 07-30-2018, 10:44 AM

Updated tune to take advantage of the throttle response (and to fix an issue that came with the swap). I ended up tweeking the rail pressure maps, cut duration by 2%, adjusted main event & post event timing tables. Motor is way stronger than it was before the update, even with cutting the fuel.

The key here was the post event timing. In a nutshell, I advanced the main event another .25*, lost spool on the turbo and brought it back with the post event. This also cleaned up the smoke that comes with timing advanced too far, worked really well. Pretty happy with the change in performance.

FWIW, doing another eco tank this week, 500ish miles & fill it up (Thursday or Friday).

slowmover · 08-03-2018, 02:18 PM

Still need the fuel burn graphed. Available here or on Fuelly or similar. Just add notes per tank.

Around here it’s understood that the trend is what matters for determining FE. First, against a baseline. The starting point. Calendar Year 20XX at Y-miles and Z-gallons. Average MPH fir the year (Engine Hours into miles)

It also means consistent testing. Run the highways at the same speed. Etc.

We know that reduced fuel burn is mainly a matter of a higher average MPH. As a result of fewer engine starts, especially from cold. There’s a corresponding reduction of total miles, though it may not be high.

Most can break out highway versus city miles. Or, miles while towing or heavily laden. There will be one type of use that predominates.

What is the predominant use, and show us how changes have increased the Average MPH (with any changes to total miles) and,

How accomplished.

Frankly, there’s not anything yet you’ve done that can’t be accounted for by driving style changes. We are left hanging in the air with nothing to grasp.