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I can't recommend any aftermarket turbo kits as they are very expensive and require a lot of replumbing of the exhaust up around the doghouse, which adds significant heat, plus I'm not salient about the adviseability of driving a red-hot turbocharger into an ice cold stream....sounds like a recipe for disaster to me.
What I do recommend, most heartily, is a supercharger! Specifically a Whipple supercharger, which is what I have on my truck. The benefits are that you get "instant" boost with no turbo lag, which is better for "crawling" because you don't have to "goose" it to get the turbo to spin, and you don't get a burst of power when it does....just smooth boost from zero to max...insignificant amount of added heat, only the heat of compression, not the hot exhaust, so you get better performance...much, much easier installation, you can do it yourself in about 8 hours with no welding required, and, if you trade your truck in, you just slap on the old stock manifold and take your supercharger with you to put on your new truck, something you can't do with a turbo...so you save money.
And....it's about half the cost of a turbocharger...don't quote me, but about $4500 as opposed to over 7K.
Call Dave Darge at Whipple at 805-466-5252 or 209-442-1261, and tell him I referred you.
I've had a Whipple Supercharger for just about a year and I concur with Scott's assessment most heartily. It turned my 94 wagon from a dog to a sportster. Here in Colorado, the freeways in the mountains get a bit steep. The original 6.5L just wasn't cutting it. I would slow down to 45 mph with it floored going up any significant hill. With the Whipple, it just doesn't happen.
The parts were top quality - a great kit. Unless you are very accomplished mechanically, I would be a bit leery of a self-install on this. High Country 4X4 did a superb job on mine. But it was nearly $2000 on top of $4500 or so for the kit. Well worth it from my perspective.
I'm pleased to see AMG add the Turbo option, because I just didn't think there is enough power in the normally aspirated engine for this beastie. But I agree with Scott that from what I've seen of the factory turbo's, I'm still out a little ahead with the Whipple.
As I recall, the Whipple was about $4200. No, I didn't install it. High Country 4X4 did here in Denver and I think that added about another $2000 to it.
There is an adjustment on the fuel pump regulating the amount of fuel that goes to the engine. Because of the addition of the Supercharger, you can increase the amount of fuel which does rather dramatically increase the power in this case. No problems passing emissions either as it turned out. So we got a pretty big hop from adding the Supercharger, and then another one from adjusting this fuel pump adjustment.
A Whipple Supercharger as installed in a Yukon
My experience with Whipplechargers has been generally good with 100K+ on mine previous to the engine expiring. However Whipple recommended that the EGT sensor be placed at the "Y" in the connector exhaust pipe. I have since learned that this position will give readings that are actually 2-300 degrees lower than actual temps. The best place to mount the sensor(s) is in the exhaust header itself, as close to the rear cylinders as practical and keep an eye on the gauge. It doesn't take long for the temps to approach and exceed the 1200 degree mark, depending on how much fuel your pump is delivering. Be conservative. Mine are now located about 2 inches in from the end of the headers. I say "are" because I use 2 sensors and a Westtach 2 cylinder gage commonly used for snowmobiles. With the alleged heating problems in the 6.5 it might pay to monitor both exhaust manifolds. Also I recommend installing an engine oil temp gauge and switching the position of the water temp sender with the HPCA switch. That puts the water temp info where it appears to be most useful - in the #8 cylinder area. As for the Whipple itself it has been very low maintenance. It seems to use up a drive belt every 20-30K and I have replaced the oil seal in the snout.
Thats it! Enjoy the power and sound.
- Mark Lane
Interested in supercharging your Hummer? You can buy new supercharger kits from Whipple Ind. for your 1992-1993 6.2l, 1994-1995 6.5l (non turbo motor) and 1995-1996 5.7l gas hummer for $4300.00. They used to be $4995.00. Call Whipple at (559)442-1261.
Let me give you my findings as to the Whipple supercharger. For a GAS engine I recommend it highly. The 4 bolt main, Chevy 350 is a stout engine that can easily handle the 6-8 psi of boost provided by the Whipple. Due to its design (essentially a lysom screw compressor) the Whipple provides full boost right off idle. Full boost at low RMP equates to an instant increase in HP and torque. Perfect for a Hummer application. I ran a Whipple on a Crate marine 350 (in a old boat mind you) for over 1000 hours without any engine problems. (NOTE: 1000 hours equates to 60,000 statute miles if you always drove at exactly 60). This engine spent hours upon hours running at 4-4500 RPM. U pon removing the engine, compression across all 8 was still within 10%, bottom end wear was marginal. For the marginally stressed 350 in the Hummer I recommend it without hesitation.
In regrads to the DIESEL Whipple my findings are slightly different. The first problem lies in the nature of the engine itself. The Whipple supercharger is simply an engine driven compressor. (OK an oversimplification, but hey...) As it compresses the intake air, it adds heat. Depending upon boost level and ambient temp expect to see 40-125 degrees of intake charge "preheating". Early 6.5's (prior to 1997?) have some inherent cooling problems. The rear most cylinders are especially problematic. In an normal NA application, this isn't that big a problem, but adding the stress of a hotter intake air temperature and you can get into trouble with cracked heads, blocks and blown head gaskets. GM (and in turn Hummer) went to sprayed pistons, a higher flow water pump, and a redesigned coolant crossover to help eliminate this problem. (This was discussed a few months back, so I wont go into detail. Check the archives for additional info.) If you're adding a supercharger to your truck, I suggest you move up to the high flow water pump and crossover. The crossover will require a bit of modifying to first mate with the early style accessories and then to get around the blower. Nothing too problamatic, however. Also, swap the locations of the temp sender and the cold start switch. This will put the temp sender at the back of the passenger head, exactly where overheating problems tend to occur, and will give you a better idea of what your coolant temp really is. This info comes via some testing I recently did while working on a Whipple-related project. The truck in question only has 2000 blown miles on its 3000 mile old engine. I therefore can't make any long term predictions.
The only additional problem I have encountered with belt driven superchargers in general lies in increased wear of the front main bearing. The addition of the supercharger crank pulley (located one belt width forward of the factory serp belt) causes a slightly longer lever arm for force to act on. Add the tension you put in the supercharger belt and the load on the front main goes up pretty quickly. It is not going to instantly destroy things, but the increased wear is definitely there. For example, on my 21 psi, cog-belt driven supercharged Ford 302, I wipe out main bearing every 7,000 miles. In a Hummer application (at a much lower belt tension) things will definitly not be as severe.
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