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Old 11-30-2013, 05:02 PM   #31
Number 3
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Drives: '19 XT4 2.0T & '22 VW Atlas 2.0T
Join Date: Dec 2008
Location: Illinois
Posts: 12,141
Quote:
Originally Posted by Doc View Post
Oh certainly someone out on the track with track experience could tell the difference in a 200 lb weight reduction, but for all the owners who never go on a track it's about the difference between driving by yourself and having a 200 lbs passenger with you; not very noticeable performance-wise.

The performance difference between a current Camaro, and a current one that has 100 lbs less unsprung and unsprung rotating weight is startling. You feel it the instant you press the gas pedal and start moving.

The fuel savings would come from not having to push the gas pedal as much to get the car moving, which is probably the majority of the type of driving most Camaro owners have to do. Unless you're driving long distances where you're cruising in 6th gear, most driving is around town with stop-and-go traffic. I barely have to push the gas pedal on mine to get moving and before I know it I'm at the speed limit without having to push the pedal any further. (I've done the weight reduction on mine). I've also done headers, cam, etc.... none of which are or were aimed at fuel economy. I'm pulling about 450 hp to the rear wheels. On the freeway at 70 mph in 6th gear I'm getting about 26 mpg. Around town with the way I like to drive I still get 14-15 mpg. If I was driving for economy that number could go up; and that's with all the performance mods I've done. I also have 19x10" wheels all-around which work against me for fuel economy.

Driving a stock SS it feels like I have to push the gas pedal 3 times farther to "try" and get it to go somewhat like mine does; and it's still not the same. It would be interesting to do the weight reductions on a current stock 1SS similar to what I've done and compare that to a stock non-modified car. The performance difference would seem like they aren't even the same type of car, even though nothing under the hood was modified. As for fuel economy, comparing both under the same around-town driving conditions I'm guessing you'd see an increase of maybe 2-3 mpg for the modified car. Not so much on the freeway at a steady speed where the extra weight on the unmodified car isn't that much a penalty once it's in motion.

Imagine though, if the new weight-reduced technology could be used across GM's product line, what adding 2-3 mpg could do for their corporate average. It might even be more than 2-3 mpg improvement on the bigger, heavier vehicles where the owners are pushing the engines harder to get them to move.

Remember, a potential buyer who tests drive a car is basing their decision on their perception of how it feels; how it responds, not a number. If they go for a test drive and the car just sparkles; they just barely touch the pedal and it goes... RIGHT NOW... they will think it has power and performance regardless of the "numbers". The actual hp number doesn't mean much if they have to push the pedal halfway to the floor and it takes several seconds before they feel like it's starting to really move. GM needs to engineer and design for perception rather than just numbers and spreadsheets. And don't forget that 100 lbs of unsprung and unsprung rotating weight is also static weight so the "number" does improve on weight reduction.

You can find about 50 lbs of reduction just in the wheels and tires alone. The other candidates are brake rotors, axles, flywheel, clutch, driveshaft. Shocks, shock towers, suspension arms and components, brake calipers, hardware, etc. Collectively across all 4 corners of the car you can find that other 50 lbs of reduction quicker than you might think.

Another area of improving the driving perception is by improving the efficiency of the drivetrain. Better low-friction fluids in the trans and diff. Spend the extra money on an efficient 1-piece driveshaft. I gained 8 hp and 9 lbs of torque to the rear wheels just by replacing the factory 2-piece shaft with a carbon fiber 1-piece:

http://www.camaro5.com/forums/showth...t=45165&page=5

I imagine an aluminum 1-piece would produce very close to the same results. If I were GM I'd go on a mission to reduce the unsprung and unsprung rotating weights, and then start advertising the rear wheel horsepower as the "real" power you feel. If they dynoed a stock Mustang or other "competitor" cars and started comparing rear wheel horsepower to the rwhp of a new "mission-improved" Camaro and could show there's more power where it counts on a Camaro, that could be a genuine marketing/sales advantage. Imagine being able to free up 8-10 horsepower to the rear wheels without having to do a single thing to the engine, but being able to advertise last year's to this year's improved "power you can feel". (I should trademark that lol).

I'm not saying they should stop improving the engines, I'm just saying that's not the only area they can look at to help meet upcoming cafe standards. Engine improvements are bloody expensive along with the lengthy testing/certification procedures. The knowledge, design and techniques they would gain reducing the right kind of weight would help them across the board on every vehicle they make.

By the way; as for the data you wanted to see, look through my project thread link I posted just above; I documented everything with weights and dyno sheets as I went along. My current vehicle weight with a full tank of gas (no driver) is 3,700 lbs. And that's with the 19x10" wheels. Interior is completely stock; back seat and everything, so I KNOW the reductions can be done; and I did it without gutting the car. Going with the stock wheel sizes which would be even lighter, I know GM could do it too.
Doc, love your passion. But you won't get an EPA certified 2 to 3 mpg simply by reducing unsprung weight.

I absolutely agree that there are a ton of things you can do to simply make a car feel faster and quicker by simply adjusting throttle tip in. It can make a big difference in feel......................just not MPG.

Again, even assuming you are right, and I agree there is an element to how it "feels" in your point, it will be hugely expensive to get 100 pounds out of the car in this area. I can assure you that GM and every other OEM would literally kill for 2 to 3 mpg and if it were as easy as you suggest we'd see 13" tiny wheels and teeny tiny tires one every car. But you don't and there is a reason for that.
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