H2 Performance Comments

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I preferred the easiest to install, least intrusive and of course the most reliable supercharger system. I chose the Kenne Bell System.

With this you do not need an inner cooler, no tapping of the oil pan for fluid and if you choose you can have a custom program written very easily. Inner coolers aren't necessary or even needed as the Blower doesn't produce as much heat as the Radix or Magnuson Roots types.

I have JBA Ceramic headers, bolted right in with hand tools in less than a hour.

I believe you can have a mild 4 - 5 Lbs boost and run 90 - 91 Octane gas pretty safely. Or run 8 - 10 PSI and 91 - 93 and have a kick in the pants you'd have to experience to believe.

I have an Extreme flow muffler but I feel others are better so I wouldn't recommend Xtreme Flow for anything.

We only install the Magnachargers on H2's, about three installations a month. You get better MPG with a blower, average around 2/4 mpg on highways. Don't run excessive amounts of boost, 4-5 lbs is sufficient for a good long life on your engine. The inexperienced usually go with 8-10lbs of boost, and that is where the problems start.

Just an FYI to anyone else planning to install a K&N intake system in their H2. I got the Air Charger kit for the 05 H2, but it was a super tight fit up against the fan. I ended up having to remove about a quarter of an inch from the end that connects to the throttle body to prevent the outside of the intake tube from rubbing against the fan. Now it's in, clears the fan, and sounds great as it sucks in air.

I have a Whipple Superchip programmer If you use it and upgrade to headers, muffler and air intake that will be about all you'll ever need, maybe not all you'll want be more than you'll need and the best MPG you're ever going to see 13.5 - 14.2 Avg.

I've done just about every conceivable performance mod and that's the best bang for the buck of anything to this point.

I'd use either Borla or Basanni exhaust, JBA Ceramic Headers, Nology Wires S1K plugs, gapped to .035 AirAide intake, and the Wildfire/Whipple latest program set to Tow  / Tow and 89 Octane. Play with the Tow button when you need a delayed shift point or want to keep the thing higher in the RPM range and enjoy it. If you think at that point you need more, then add the Kenne Bell Supercharger and Nelson Performance program as I've done. Then you'll be back to less than 10 Mpg but have more power than you'll ever need.

I just installed a Hypertech on a 05 H2 yesterday. 

The ride is awesome compared to when I got it and it has 24' wheels on 37" Toyo Mudders.

We have a stock H2 and a Supercharged SUT in house.  This 05 H2 is definitely not like the supercharged SUT we have, but it is really a nice upgrade.  The 37" tires rubbed like crazy, so we put on the torsion lift. The power was lacking so we added the Programmer and the exhaust.  Both easy installs and definitely worth the price. 

With all that being said....I can say that I have 3 levels of Hummer performance:

1. Stock
2. Power programmer and exhaust
3. Supercharged

If I was buying something...I would get the Programmer and exhaust package. Seems the best gains for the best price. The Hypertech has tuning for regular gas.

I put a Flowmaster exhaust on and a Superchips programmer.

There are more expensive exhausts out there (that are reported to be even higher performance) but I off-road my H2 and like the ground clearance of the Flowmaster, and the fact that it isn't too expensive to replace if I ruin it. Aftermarket exhausts are all about back pressure and sound. The
Flowmaster was a good solution for my needs and I installed it myself in a couple hours, then paid $70 to a muffler repair shop to inspect my work and weld the joints. It's not that I'm cheap with exhausts - on the contrary. I have an aftermarket exhausts on each of my cars, and just had X-Ost
(http://www.x-ost.com/) custom make one for one of my Ferraris. I just don't believe in spending more than is necessary, and I couldn't justify spending more than I did for the Flowmaster, especially since I wasn't convinced that a more expensive exhaust would make a big difference in HP.

Regarding the programmers: from what I've heard from a couple of my friends who work in the BMW chip programming industry, many of the programmers out there are simply copies of the Superchips one. I keep my Superchips programmer in the rear plastic pocket/shelf of my driver's door so I am
always ready to change the program to towing if I need to. Works great, and also functions as an ECU error code reader.

I have been very happy with the results of these mods, and although I haven't dyno'd to see what the actual gains are, there is a "seat of the pants" difference to me. I can certainly hear a difference with the exhaust note, too. The only other performance mod I've done is installed a K&N intake and filter, and I really like the sucking intake sound of that under full throttle.

The only drawback to the programmers is that you have to remove the OnStar fuse during programming (kind of a hassle if you change programs often, which you probably won't, but just an FYI).