To Turbo or to Supercharge, that is the question.

[wpage]

Too bad GM wont do some of this homework

[stagger_lee]

Maybe they did and didnt share. I cant wait to see the outcome of this whole thing. It just might prove to be a worth while power upgrade for us, if done right and tested significantly.

[b1ownh3]

Most people relate supercharger output to that of a roots style (like a magnuson or a Roush). The supercharger we use is a centrifugal style (similar to a procharger). With a roots style, you tend to make high levels of boost down low, which make for great low-end torque. However, they usually run out of air at higher RPM's and fall off. With the centrifugal style, you don't usually make boost till about 2500 rpm (depends on engine rpm and max boost) so they usually make better power up top. Now if you are concerned about over-loading the driveline at low rpm (15-2200), I don't see any added stress from this perticular supercharger. We have a system on a 2006 H3 development vehicle that we have been driving around. It has pretty much only been driven on the road, so I can't give any feedback to how it does in the crazy situations some of you are looking to put one through . I have a dyno sheet on it, but it didn't print very clear so it doesn't show up when I try to scan it. Here is a summary:

Max Power - 242hp @ 5800 rpm
Max torque - 226 ft-lbs from about 3200-5000 rpm
Max boost - 7.78

These numbers are pretty conservative for a stock engine. Of course you can push the boost for more power, but at some point I would worry about the pistons. I'm going to contact some of my guys at GM, as I know they have pushed this engine with both turbos and superchargers until they broke. I'm curious as to at what level they broke, and where they broke (pretty sure it would be the pistons). As I get info I will pass it along.

[HummBebe]

Okie Dokie.....

all time 4 wheel drive. Lets clarify

It's "full time 4 wheel drive"

In 4 high mode the drive train is split 40% front, 60% rear.

In 4 high lock the drive train is split 50-50

In 4 Low lock, again 50-50

When you are in 4 low, (as I was going up the golden stairs ) trying to crawl an uphill obstacle, brake throttle modulation, I was at about 22-2500 rpms before the truck would even move. Thanks to the 4:1 transfer case and the 4.56's.

You are correct in saying that this is done at slow speeds. It is housing flex that causes the failure. However, prop shafts and diveshafts along with carrier brackets have failed as well.

Now a question for you.....do you or are you in possession of a 4WD dyno??

This could be cool

[HummBebe]

PS, those numbers look like the 3.7 not the 3.5. Yes?

[b1ownh3]

Yeah, I knew it would only be a matter of time before I miss-spoke something. Sorry for using the wrong terminology. You explained it all just like the Hummer dealer. I guess I wasn't paying enough attention. I just wanted to drive it.

Hopefully I'll have better dyno graphs I can post next week so you can see what engine speeds the torque increases, and how much. The graph I have of the 3.5 engine has time across the bottom....not RPM. Hard to read it. Maybe I can get a better graph made up tomorrow and post it.

You are correct, the graph I posted is my '07, which is the 3.7.