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Old 10-21-2017, 10:29 AM   #44 (permalink)
slowmover
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Join Date: Oct 2009
Location: Fort Worth, Texas
Posts: 2,442

2004 CTD - '04 DODGE RAM 2500 SLT
Team Cummins
90 day: 19.36 mpg (US)
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Quote:
Originally Posted by Grant-53 View Post
All the radiator is affected by is temperature and mass rate of flow. The fan determines the rate of flow by blade configuration and RPM.
Again, have you tested?

Here's a clue: No one running HD trucks uses electric fans. The FE incentive is there, but the tech isn't.

OP, the fan shroud is huge. Blades should be halfway in/out or more (less to outside) and fan blade tip should be within 1/2-inch of shroud. All air thru shroud, no exception. (Some vehicles used spring-loaded flaps on shroud to relieve highway air pressure).

Same for the front of the various heat exchangers: directed airflow. Close off the top gaps between exchangers, leave bottom open.

Also need an air dam below vehicle ahead of the shroud rear opening. Negative air pressure is idea.

This was all SOP on carb'd HD/Police engines.

A heavy duty thermal fan clutch also. The penalty for using a fan should be of shortest duration.

FE is a lot of hot oil temp (220F nowadays) and "cool" coolant (185-195F). It takes a powerful fan to step in and keep things in check. I have both coolant and oil temp gauges in the KW and it's the latter I rely upon to keep temps reasonable. (I may know to remove winter cover at 41F, but the gauges are quick to hit me if I don't).

So I also recommend an oil temp gauge.

And you're rationalizing your travel speed. The "discrepancy" problem has as much to do with WHAT traffic is slower. I run 10-12,000 miles/month and all over country. It's the traffic volume that's always the problem. Those studies were ATA trying to get split limits changed.

You try my analysis and you'll see. Acceleration and braking events. Lane changes. (Constant rigid rule about spacing as control) Any of these occur, and you're not in the flow. The flow is always below the upper posted limit. That flow is about maximizing steady state travel.

I spoke of the graph where average mph and average mpg can meet; the desire to be timely AND fuel efficient. This is expressed as cents-per-mile fuel cost. On an annual basis (X-miles). One can easily see that overall truck spec is king. Second is climate, then terrain. Driver Motivation is last. Aero mods wont give you a better cpm without understanding speed. Analyze your records.

If one is only passing governed truck traffic (and similar; at about 63-65/mph), one is close. (I'm going to leave out the stupidity of drafting; a single serious accident at those speeds is life-changing).

You should also test emergency stopping distance from 75 and from 62-mph. One can play around with 200' vehicle spacing distance down closer to 100', but it seems you believe "skill" overcomes statistical verities. Nevertheless, what's the difference in those two? As even today's more sophisticated pickups can't handle a slalom course faster than 57-mph while empty, I urge you to know the time/distance to get down to 55-mph or less.

(You want to disagree with me, fine, then post those stopping distances first, please. A deserted commercial district with wide lanes on a Sunday morning is the perfect place for that).

Slowing is easy. Stopping is hard.

Let tested numbers work for you. Quantify the risk.

Again, I'm really impressed with all the hard work, and consider myself part of your cheering section.

.

Last edited by slowmover; 10-21-2017 at 10:39 AM..
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