New 07 Silverado w/AFM & VVT or Classic 07
05-15-2007, 09:21 PM
#31
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Ideally, if this new cam were available you would leave AFM and VVT operational. They don't effect WOT operation, but would benefit fuel economy in low load situations. 23 mph on the highway at 70mph is excellent especially with a 3.73 ring and pinion. A coworker of mine has one of the new Nissan V8 trucks and he get 13 city and 15 highway and that's with a gear higher than a 3.42 because at 70 mph he's only turning 1.5K rpm. His mileage makes 23 mpg with AFM and VVT look real good.
05-16-2007, 06:53 AM
#32
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Originally Posted by eallanboggs
His mileage makes 23 mpg with AFM and VVT look real good.
I was re-reading the article on AFM and saw this which is good info:
For hot rodders wanting to modify their DOD-equipped LH6s, it's important to know that the switching lifter has a lift limitation of 15mm (at the valve). The factory cam uses 12.2mm of that (about .480 inch), giving the LH6 a theoretical valve lift limit of .590 inch. It's worth noting that this limit is for the lifter; a different valve spring would almost surely have to be used at this valve lift. Interestingly, it seems possible to grind a custom camshaft, which would only provide increased lift and duration to the non-DOD cylinders (2, 3, 5 and 8), thus allowing higher lift with standard non-switching lifters in those cylinders.
Last edited by nighthawk08; 05-16-2007 at 07:30 AM.
05-16-2007, 08:36 AM
#33
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Originally Posted by eallanboggs
Ideally, if this new cam were available you would leave AFM and VVT operational. They don't effect WOT operation, but would benefit fuel economy in low load situations. 23 mph on the highway at 70mph is excellent especially with a 3.73 ring and pinion. A coworker of mine has one of the new Nissan V8 trucks and he get 13 city and 15 highway and that's with a gear higher than a 3.42 because at 70 mph he's only turning 1.5K rpm. His mileage makes 23 mpg with AFM and VVT look real good.
Once GM gets the 6 speed out with its low first gear (top gear in applications right now is the same as the 4 speed), could run taller gears and have even better accel yet so that would be a bonus. Be 2009 I'm hearing though...
Give it some time, there will be cams for this stuff. And there is always the hardcore guys who go crazy and get custom ones done, but almost seems best way to make power now is forced induction anyway.
05-22-2007, 09:44 PM
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Horace Mast from Mast Motorsports just emailed me about the VVT/AFM LS engines. He said you can disable AFM by simple unplugging the electrical connector at the back of the motor. Once AFM is disable you can install a non-AFM cam(pre AFM cam). This also requires replacing the special AFM lifters with the old style(non-collapsing type) and installing a valley plate which would replace the LOMA assembly. He went on to say that the AFM cams have 4 different cam profiles instead of the normal 2. You have the 2 normal profiles on the AFM cams as well as 2 additional profiles for the AFM cylinders(one profile for intake AFM cylinders and one for exhaust AFM cylinders) for a total of 4 different profiles. I guess this means the swap is possible.
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