GM's 3.5L vs. 3.9L - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 10-06-2006, 01:50 PM   #1
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Default GM'* 3.5L vs. 3.9L

OK, so I was scoping out the 2007 G6 convertible with retractable hardtop, just for kicks and reading the specs. Here are the basic specs:

Quote:
Engine & Power 3.5L V6 with 217 hp and 217 lb-ft of torque
OR
3.9L V6 SFI with 227 hp and 235 lb-ft of torque

Transmission 4-speed automatic, electronically controlled with overdrive (manual shift mode standard)

MPG mileage estimates**
3.5L engine:
20/28 (city/highway mpg)

3.9L engine:
17/24 (city/highway mpg)

Standard Capacities Fuel tank: 16 gallons (approx.)
Seating: 4
So, for those of you who really know these things, why does the 3.9L only put out 10HP more than the 3.5L?

Sure it also puts out 19 more lb-ft torque, but it still makes me wonder.

What other reasons would someone pay that much extra for the 3.9L with those numbers? What am I missing?

Note that the 3.9 also gets much poorer gas mileage (which BTW, varies by 2 mpg, depending on where in the G6 site you are).
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Old 10-06-2006, 01:55 PM   #2
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I know the 3.9L use to be rated at 240hp, but I BELIVE, not positive though, they went DOD (Displacment on Demand) for 2007 for better mpg.

all i know....
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Old 10-06-2006, 02:00 PM   #3
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If that'* really the case, then they did something wrong. 17/24 mpg is not very good in this day and age. Heck, my Bonnie routinely gets better than that.
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Old 10-06-2006, 02:01 PM   #4
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SAE reduction
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Old 10-06-2006, 02:02 PM   #5
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Quote:
Originally Posted by Shadow
SAE reduction
In MPG calculation method?
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Old 10-06-2006, 02:02 PM   #6
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Quote:
Originally Posted by lash
Quote:
Originally Posted by Shadow
SAE reduction
In MPG calculation method?
In horsepower calculation method.
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Old 10-06-2006, 02:03 PM   #7
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Quote:
Originally Posted by Shadow
Quote:
Originally Posted by lash
Quote:
Originally Posted by Shadow
SAE reduction
In MPG calculation method?
In horsepower calculation method.
Please explain.
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Old 10-06-2006, 02:05 PM   #8
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240 hp before the new SAE Horsepower Certification thing started.
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Old 10-06-2006, 02:06 PM   #9
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The society of Automotive Engineers (SAE) have developed stricter tests on horsepower ratings which is why ann new 2006 hp numbers have dropped.
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Old 10-06-2006, 02:27 PM   #10
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Lol! I am well aware of what SAE means, as I was a member for 10 years and used to attend the SAE dinners at the Detroit Auto Show every year. I just wasn't aware of a new test method for HP ratings.

I have heard of a new MPG test and reporting method, intended to rid advertising of some inflated claims.

Anyway, back to my original questions:
Quote:
So, for those of you who really know these things, why does the 3.9L only put out 10HP more than the 3.5L?

Sure it also puts out 19 more lb-ft torque, but it still makes me wonder.

What other reasons would someone pay that much extra for the 3.9L with those numbers? What am I missing?

Note that the 3.9 also gets much poorer gas mileage (which BTW, varies by 2 mpg, depending on where in the G6 site you are).
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