Advice on aero mods for truck (2001 Dodge Ram 2500)

[MechEngVT]

Could you shift your toolboxes forward? Minimizing the gap between the boxes and the rear of the cab will reduce some air drag. If you can push the boxes as far forward as the front of the bed (or near to it) and put some bulb seal or foam insulation between the front of the toolbox and the rear of the cab it will prevent the air diverting toward the center of the truck when it strikes the leading face of the toolbox as you are having in your present configuration.

Doing this will also open up some room at the rear of the toolboxes that you could use to install some mini-boat tails like the ones used on full-size trailers:
http://www.transtexcomposite.com/pro...ml?ProduitID=3

Some light-gauge metal (aluminum flashing maybe?) or even wood could help reduce the wake area of your tool boxes and bring the effective drag width down to the actual width of the bed at the rear. Installing a sheet of plastic between the boxes from the cab-height ladder bar you plan to install down to a point at (for a long bed) or slightly above (for a short bed) the top of the closed tailgate would be a sort of an aero cap that could easily accommodate the occasional ladder.

I can't recall where I saw it, but I saw pictures of an aero-modded 2nd gen CTD Ram that was lowered and had a pre-COT NASCAR-style custom sheet metal front air dam installed over top of the factory bumper cover. The guy had also installed a GV overdrive and had some pretty high mileage claims, 30mpg IIRC, but it's been years since I've been able to find this. Might have been on TDR (which I don't subscribe to) that someone reposted elsewhere.

[htvfd460]

Dodge is torque happy with their converters. High stall rates makes a dodge seem like it's in a lower gear or slipping. Make sure that trans is cool. They don't last in this area unless the fluids changed every 15-30,000 miles. The torque converter stays free till a high rpm while plowing and severe use with a lead foot. Light acceleration does help alot though, It locks up at slower rpm.

[htvfd460]

Oh and the fluid doesn't flow to the cooler unless in gear, idling doesn't pump the fluid to the cooler at all. Only in reverse, drive and chosen gear does the ATF flow.

[Joenavy85]

Originally Posted by htvfd460

Oh and the fluid doesn't flow to the cooler unless in gear, idling doesn't pump the fluid to the cooler at all. Only in reverse, drive and chosen gear does the ATF flow.

wrong, if that was the case you would have to be in gear when you start the truck, to get fluid into your TC. fluid flows any time the engine is running, hence why you don't want to EOC in most AT cars, but won't have any issues if you just put it in neutral

[Joenavy85]

Originally Posted by htvfd460

Light acceleration does help alot though, It locks up at slower rpm.

light acceleration should be a given on this website (engine load should be kept as low as practical). RPM has little to do with when the TC locks, it's typically based on speed and engine load

[t vago]

Originally Posted by Joenavy85

light acceleration should be a given on this website (engine load should be kept as low as practical). RPM has little to do with when the TC locks, it's typically based on speed and engine load

Not entirely true.

Moderate or brisk acceleration actually saves more gas, compared to light acceleration. It is true that you might see higher instantaneous fuel consumption, but the engine isn't forced to both propel the vehicle forward and generate a decently high vacuum. In other words, brisk acceleration puts the engine closer to the ideal area on its BFSC map, than would light acceleration.

In engines that use throttles, high pumping losses occur in part-throttle conditions. That is, the engine needs to do work in order to draw air past the partly closed throttle. One result of this is that as load decreases and the throttle is closed to a greater extent, Specific Fuel Consumption (ie the fuel consumed per power produced) becomes increasingly worse.

This graph shows the phenomenon. At 100 percent load (ie wide open throttle) this engine has a minimum Specific Fuel Consumption (SPC) of 0.43 – see the bottom curve. With the throttle open only 25 per cent, the minimum SPC has risen by 63 per cent, while at 2000 rpm, it has risen by a massive 117 per cent!

(link)

Just don't floor it to the point where the engine computer goes into open loop.

[htvfd460]

Warning for all Dodge Rear Wheel Drive Overdrive Transmissions Except 45RFE

"#5. The fluid level is checked in neutral with the parking brake on. All Dodge rear wheel drive transmission have no fluid feed to the torque converter in park position unless you have a special valve installed in your transmission. The level will read higher in park than it actually is. All of the above information doesn't apply to the Dodge 45RFE. Read the stick on both sides and go by the side that reads the lowest. Always check the fluid level three times"

[darcane]

Originally Posted by t vago

Not entirely true.

Moderate or brisk acceleration actually saves more gas, compared to light acceleration. It is true that you might see higher instantaneous fuel consumption, but the engine isn't forced to both propel the vehicle forward and generate a decently high vacuum. In other words, brisk acceleration puts the engine closer to the ideal area on its BFSC map, than would light acceleration.

<Snip links to spiffy graphs>

Just don't floor it to the point where the engine computer goes into open loop.

Useful info about gas engines...

But keep in mind this thread is all about a Dodge truck with a Cummins Diesel... No throttle, no high manifold vacuum...

Mike

[htvfd460]

That is right. On a turbo diesel manifold vacuum is bad. Diesels require high compression to get fuel to it's flash point, running at 18:1 like a Powerstroke isn't enough so the turbo needs to feed more air to reach over 21:1 for proper combustion. Even at idle there is no vacuum.

[roflwaffle]

Originally Posted by darcane

Useful info about gas engines...

But keep in mind this thread is all about a Dodge truck with a Cummins Diesel... No throttle, no high manifold vacuum...

Mike

All engines, at least as far as I know, experience a drop in efficiency versus load. A 5.9L Dodge diesel for instance is at ~400+g/kWh at 25% load and drops to ~200+ g/kWh at 75% load.

http://www.eere.energy.gov/vehiclesa...er_boehman.pdf