Quote:
Originally Posted by RH77
I've driven both. The HHR, of course, has some potential with the 2.2L - I4. I'd apply some aero, feedback, underhood, and tire techniques to that one.
The Silverado. Depending on your uses, a tapered bed cap like Big_Dave's design can help Cd. The rest is going to have to be technique or serious swaps: engine and/or transmission. Maybe tire choice and ride-height as well. There's no magic bullet here. It may come down to technique only. The best advice is to limit driving it, when you can.
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Does anyone have a link to anything for Big_Dave? Can't find anything...
Yeah, the Silverado is my daily drive, and no, I can't walk to work or ride my bike (for now)... it's about 18 miles one way. The engine is a Duramax diesel w/Allison tranny, and I wouldn't trade it for anything. I'm getting ~22 mpg on the highway, which is where I'm trying to gain an aero advantage, hence the questions about lowering the truck. I like the idea of a tapered bed cap, but I'm not gonna shell out $1800 for one (Bondo's target price), which means I'll probably try to fab one myself. Haven't seen Big Dave's yet.
As for tires, the stock tires I have are about as optimal as one can have for this big truck. They're not even close to an aggressive design. After 1700 miles on the highway on cruise control (Fla and back), I'm convinced that I require an aero mod to improve things.
The HHR is a 2.4 Ecotec w/auto transmission - currently doesn't have running boards. I'm thinking about adding them though, as these would clean up the airflow (I think) around the lower edges of the car as it transitions from the front wheel wells to the rear wheel wells. It does have a clean underbelly, and the ride height is 3-5", IIRC. But there's no chance to alter the body design here without significant, unrealistic fabrication (IMHO). Other than possibly the running boards, I suspect my best gains are under the hood. If anyone has any suggestions on how to clean up the aero profile of an HHR, I'm all ears...