What's up with this? Is it true?

http://www.edmunds.com/insideline/do.../pageId=118457

A four second delay to get full power to help meet emissions? Who says emission standards don't cost horsepower?

 

A strange PCM calibration, that's for sure, but we self tuners usually care little about emissions and try to exploit the engine's full potential. It's typical for GM to detune their engines. A PCM edit for a 6.0L will nett an additional 50 ponies and torque across the entire rev range, not to mention the improved fuel economy, response and driveability.

 

Oh, it also looks like the Titan's V8 is much underrated.

 

I realize they said emissions, but I would have hoped the power cut would help fuel economy too. That does not appear to be the case. The observed economy in their testing is poorer in the Silverado than either the Titan or Tundra (12.7 Chevy to 13.7 Toyota & Titan). 1mpg isn't huge, but people also quote 1-2mpg difference in gov ratings as justification to buy one vehicle or another, so I think it is somewhat significant. I wonder if the 12.7 was becasue they were consitently flooring it trying to find the missing ponies, or were they oblivious to it at the time and the lower power simply necessitated more throttle/fuel?

So I guess this lean PCM strategy is how they got the nice government fuel economy ratings? But in reality, it isn't any more efficient in real world use? I like GM, but this is a little dissapointing. I wonder how the government rates the tail pipe emissions of each engine, is Silverado cleaner than Titan & Tundra?

 

This is bad. To me at least, this makes GM look terrible (then again I'm not concerned with emissions). I suppose it depends on what propaganda war you want to win HP or MPG/emisions. GM could at least add a "power" or "tow" or "haul" buttom to disable the 4 second delay.

 

Huh? You're saying I can waltz down to my local tuner shop with my LS2, have them tune it on the dyno, and walk out with an extra 50 HP thoughout the useable rpm range of the motor?

 

I bet its tq management messing around... plus the wide ratios in that 4 speed makes it feel even worse.

GM, when will you be equipping these trucks with the beefier 6 speeds?

 

They should've dynoed an F150 too just for laughs.

 

Doesn't Tow/Haul Mode eliminate the power delay? It would have been nice if Edmunds had actually used this feature on the dyno. Then again, it may have changed the overall outcome of the comparison.

Even so, the 5.7 Tundra is mighty impressive.

 

I'm pretty sure it doesn't change anything to do with the power output of the motor other than waiting quite a bit longer to upshift and being very eager to downshift. At least that's the only thing it changed on the 800s.

 

Soon, I expect 6.0L trucks to get a 6 speed for 2008. Cadillacs and Zetas will have priority over trucks though.

 

The lean (stoichiometric, really) versus rich setting only comes in at WOT. I believe full throttle is only done for the EPA "agressive driving" cycle (also called US06, I think). There is an emission test for that, but all manufacturers have to meet that. I wonder if the Nissan and/or Toyota run rich at WOT? Also, it's surprising to me that there is as much HP to gain as Edmunds was seeing....

 

Thats an unusual feature, something that would would lead me to aftermarket PCM tuning shortly after buying such a truck.

 

This is some very disappointing news...If I was buying a Silverado I would be extremely turned off by the bad pcm calibration I can understand that it can't be super aggressive but a 4 second delay is rediculous.

 

No. That's peak hp but with a nice broad spread of tq.

I didn't think I needed to qualify my comments?