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10-28-2007, 03:12 PM
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Hummer Veteran
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Join Date: Aug 2007
Location: Clearwater, FL
Posts: 31
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Re: This Just In... All 2008's must run PREMIUM!
Quote:
Originally Posted by mikejr
I remember when they bumped up the HP in the avalanch from 2003 to 2004 it idled rougher too.
I agree with you, that exhaust sounds AWESOME....thats probably why I am only getting 10.7 MPG, I keep putting my foot into it to hear that rumble. It is sweet sounding.
Mike
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Yeah, that new rumble is definately worth the extra .20 a gallon.
__________________
2008 H2 SUT Adventure series "Tactical Edition" ordered 8/8/2007. Delivered 10/11/2007, GM Bought back on 11/28/2007 and took delivery of replacement 4/3/2008... GM made everything right.
Black/Black/Black 24" Mazzi Hulk Wheels, Custom Powdercoated Tire Carrier Eliminator and Fuel Door, AVIC-f90BT and every add-on available, SWI and Onstar interface. SR7/ZR3 Radar Defense System. Amp Research/Bestop Powersteps. Llumar 5% Tint. Heads-Up display.
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10-28-2007, 03:58 PM
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Hummer Guru
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Join Date: Sep 2006
Location: Europe, Belgium, Waregem
Posts: 5,280
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Re: This Just In... All 2008's must run PREMIUM!
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10-28-2007, 05:35 PM
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Hummer Guru
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Join Date: May 2005
Location: Virginia Beach
Posts: 5,081
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Re: This Just In... All 2008's must run PREMIUM!
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10-29-2007, 11:48 PM
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Hummer Veteran
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Join Date: Jul 2003
Location: Illinois
Posts: 75
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Re: This Just In... All 2008's must run PREMIUM!
Have the same slight rough idle at times as others have mentioned. Have been using Shell 87 since day one. Just filled up today and got 13.6 MPG, city driving, with 1050 miles on it.
On the highway, if I set the cruise to 65MPH, I can get a solid 16 - 17 MPG. Driving around rural roads at 40-45MPH and I have seen 18+ MPG.
Of course this is all with very conservative driving.
No knocks, pings or anything else for that matter.
Overall, I think this new engine / trans / gearing is great.
__________________
 2008 H2 Graystone Metallic
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10-30-2007, 03:34 AM
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Hummer Authority
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Join Date: Nov 2004
Location: Little Rock, Arkansas
Posts: 1,784
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Re: This Just In... All 2008's must run PREMIUM!
Bumping HP is just adding fuel/air then adjusting timing. If you are running what factory calls for then take it to dealer and have it checked something is wrong. It could even be the knock sensor. You may need a spark plug colder or hotter. There are so many variables to a knock it takes someone with software etc. to check it out. You could play with a handheld, experiment taking notes save allot of money and figure it out.
Tuning is note hard just requires some study up front on how the new stuff works. I use to just ear tune back in the muscle car days. I miss it. Run Accel distributor stuff etc. Figure fuel/air ratio on a printed table based on carb, heads, cam, and just figure your way. Once it was all done the final timing was done by ear at about 2000/2500 rpm by ear no timing light. I could put my 68 Mustang 289HP 3/4 race cam, roller rocker/lifters, and tunnel ram then time it perfectly on the money. Next it was pink slip time.
TAZ
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05 H2 SUV cus. paint, Magnuson SC 6/12lb boost, cowl hood scoop, 12" dash touchscreen, GM elec. fans, HPTuners.com tuning soft., Dynatech headers dual catback exhaust Jet Hot chrome front to back Flowmaster Super 40's, Diamo 8 Karat rims & 325X60-20" Toyo, 4 OEM Captain seats Katzkins leather, rear console computer inside running all AV/NAV etc., Infinity component system 3 amps Tsunami Caps, rear flip down 12" monitor, headrest monitors, overhead console boost, fuel pressure, & A/F ratio gauges
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10-30-2007, 03:48 AM
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Hummer Veteran
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Join Date: Sep 2007
Location: Illinois
Posts: 38
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Re: This Just In... All 2008's must run PREMIUM!
Quote:
Originally Posted by H2 007
Have the same slight rough idle at times as others have mentioned. Have been using Shell 87 since day one. Just filled up today and got 13.6 MPG, city driving, with 1050 miles on it.
On the highway, if I set the cruise to 65MPH, I can get a solid 16 - 17 MPG. Driving around rural roads at 40-45MPH and I have seen 18+ MPG.
Of course this is all with very conservative driving.
No knocks, pings or anything else for that matter.
Overall, I think this new engine / trans / gearing is great.
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for what it matters my 08' f-450 twin turbo idles smoother than my 08 H2. Sounds like most 08's have a rough idle. at a stop light the other day, the engine idled up by itself kinda lurched forward, if i did not have the brakes firmly on it would have ended up in the back of someones car. i think gm has something messed up with the ECM fuel mapping and they need to issue a reflash update. My idle is so rough that it almost feels like its going to stall out, i can watch a bottle of water jump all over the place in my cupholder. I can also feel it through the brake pedal. I'm all for the exhaust note and hot cam, but can't we have that with a vehicle that idles properly?
__________________
2008 H2
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01-10-2008, 08:52 AM
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Hummer Veteran
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Join Date: Dec 2005
Location: CA
Posts: 85
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Re: This Just In... All 2008's must run PREMIUM!
I've got almost 7,000 miles and still running great...
I do agree the engine has a bit of a rough idle.
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01-12-2008, 03:54 AM
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Hummer Expert
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Join Date: Aug 2006
Posts: 925
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Re: This Just In... All 2008's must run PREMIUM!
Quote:
Originally Posted by blackhawk29
for what it matters my 08' f-450 twin turbo idles smoother than my 08 H2. Sounds like most 08's have a rough idle. at a stop light the other day, the engine idled up by itself kinda lurched forward, if i did not have the brakes firmly on it would have ended up in the back of someones car. i think gm has something messed up with the ECM fuel mapping and they need to issue a reflash update. My idle is so rough that it almost feels like its going to stall out, i can watch a bottle of water jump all over the place in my cupholder. I can also feel it through the brake pedal. I'm all for the exhaust note and hot cam, but can't we have that with a vehicle that idles properly?
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That sucks......I have to say my 04 pur's like a kitten
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01-12-2008, 05:55 PM
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Hummer Novice
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Join Date: Jul 2007
Location: NJ
Posts: 23
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Re: This Just In... All 2008's must run PREMIUM!
im close to 10,000 miles on my 08 H2 and still running strong with 87 octane 
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