Supercharger Questions

cdhd2001 · October 23, 2002

Okay, I have a few more supercharger questions. I am still trying to decide on whether to go with a centrifugal or twin screw (whipple) supercharger.

Everyone says that a roots or whipple start making boost off idle. I also know that the supercharger is connected to the crank, so that means the supercharger spins faster as the rpms go up. Here is my question. At what rpms are the advertised boost levels (6psi) attained? Also, how many psi of boost does it make at 2,000 rpms? At 3,000 rpms? And at 4,000 rpms?

Now with the centrifugal supercharger there is a step-up gearing happening. This means that most do not attain full boost until redline. I have also read that some centrifugal blowers create more boost at lower rpms than others (Powerdyne comes to mind). At what rpms do you start seeing boost? How much boost would there be at 2,000 rpms? At 3,000 rpms? And at 4,000 rpms?

Here is another question. Most people conclude that continually running an engine at boost will decrease engine life. So if that is the case, then would a whipple or roots style wear an engine out quicker due to the boost available off idle? Would an engine (daily driver/ 10% tow vehicle) survive longer with a centrifugal blower?

The main reason I am interested in a supercharger is for more power towing. However, my take off and acceleration is more than adequate (the 6.0L is better than my old TBI 454!). I only run into a need for more power between 55-70 mph when moderate to heavy winds are present or when climbing moderate to steep hills with winds. I tow in 3rd gear (auto) at 3,000 rpms at 65 mph.

BTW, trading in for a new truck is out of the question.

2001 Chevy 2500hd 6.0L/auto/4.10

1996 Alfa Ideal 30ft. 5th wheel

dcairns · October 24, 2002

You might want to try poking around at the forums at Superchargers online.

http://www.superchargersonline.com/forum/

They sell superchargers there, but the fourms have some good info. It is not a real active forum but if you look back on all the past questions in the "General Supercharger Tech" section, you will find the advice you seek.

In a nutshell, a centrifugal compressor produces boost at the square of RPM, so as RPM increases in a linear way, the boost increases in a logarithmic way, or simply put, it reaches it's peak at your engines peak RPM. This is great for drag racing at full throttle but bad for towing.

A Whipple screw type is a great setup for towing.

If you can excuse the oversimplification, and marketing slant, this chart from Whipple's site shows how the two technologies differ in boost characteristics.

Kenne Bell is also making screw type compressors for GM now www.kennebell.net and has some good info to read on their site. They are supposed to be CARB approved soon, if you are in California. Otherwise they are available now.

tbyrne · October 25, 2002

As noted above a screw type supercharger like the Whipple will be better for towing. It produces more power in the low RPMs so it helps to get heavy vehicles/loads moving. A centrifugal supercharger builds boost as the RPMs climb. These are better for performance applications where the vehicle will spend more time in the mid to upper RPM range. You can use both versions for both applications. For example I run an intercooled Whipple on my 8.1 Suburban. The truck pulls 10,000lbs like it's not even there and is great to drive on the street (very responsive). We have customers using centrifugal superchargers in dual purpose trucks (towing and a little time at the drags). They have also been happy with the results and say that there is no problems towing a heavy load.

You will generally see about 6# of boost from the Whipple while the Vortech makes 7# and the ATI makes 8-9#. All of the kits are designed to be bolted onto a stock motor with no other mods required. You can usually get the normal life out of a supercharged motor with normal driving. If the gas pedal is attached to the floor from every stoplight that may shorten engine life a little.

Hope this helps,

Tom

cdhd2001 · October 26, 2002

thanks for the info guys! I can't tell you how bad I have been struggling with the decision. My wife (accountant) is very concerned with the money issues, hence tilting the decision toward the centrifugal. I was concerned with towing and its (sc) ability to help in that department. It looks like the compromise may be a Magna Charger (long term reliability) if I can find one that is in the inbetween price range.

Thanks again for the help!

tbyrne · October 27, 2002

One thing about the Magna Charger, it tends to be louder than the Whipple (especially while towing). I ran one on a 6.0 Suburban last year. It pulled ok but dreading listing to the whine.

Tom

sykboy · November 23, 2002

####, I wish I had this problem; must be nice. I have been reading about Kenne Bell a little lately and IMHO the installations look very clean and well engineered. Maybe it is just the polished compressor, but, I like it. Anyway, towing = torque, enough said. Why buy a centrifugal if it doesn't give you power where you need it?(Twins & Roots = inta'spool) Your engine will last longer(?) with a cent? That is misleading. You are buying a 'charger for boost. If a cent is less of a burden on your engine, it is simply because you aren't using it. I have seen a lot more complaints about the quality of cent's as well. Superchargersonline is a pretty good place to check some of this stuff out, but, when it comes time to buy you need to consider installation, reputation, customer service and lastly, price. Price is the last thing I would research and the easiest to get info on. "My blower is jacked, I am stuck out in BFE, and my girl is pissed 'cause I had to have the performance"......O u c h.. At least you saved a buck or two!

Hope this helps or as least has some pertinent info. If you are in the midwest/Ohio Valley, may I suggest Olson Race Cars. They make drag chassis, but, they do a lot of custom stuff too. They are a KB dealer, but, they work on anything.

Good luck and smoke a Lightening while you are at it!

ForceInjection · December 16, 2002

Yes, I agree with Sykboy on the fact that, “why buy a centrifugal if it doesn’t give you power where you need it?” The centrifugal will be a good s/c if your looking for more power, but your truck will act like it is stock at the bottom end, which is pointless if you are looking for more towing power. Stick with the Roots or even the Twin-screw type compressors they will be idea for your goal. It’s great to have a supercharger, but what is the point of having one if you will not benefit from it. Go with the Whipple I’m sure you will be happy.

Listen to what Tbyrne has to say, he offers great advice that is defiantly noteworthy. If you give SuperchargersOnline a call and you tell them that your on this Forum and tell them about the accounting issue, I’m very positive that their great customer service will do something for you.

gandolphxx · December 17, 2002

Thhe question of "boost at idle" was raised with the Whipple, not a problem really since it dumps until needed, so you are not running under boost most of the time.

I have a digital vacuum/boost gauge - amazing how little the whipple kicks in, mostly on ramps [lead foot], passing at 75 [quickly] and of course at the track