fmi

I've always been into root blowers and i'm considering switching to a Rtech intercooler with a vortech charger.
I have had experience with Procharger, can you make an Rtech intercooler work with a procharger?
If so, how much more efficient would it be than a root style blower?

HARDCORE A/O

The best person to answer your questions would be Tomcat, who owns R-Tech. He is a walking encylopedia of centrifugal blower info. Yes, a procharger can work with the R-tech box. you just connect them with the right sized hose.
In my view, a R-Tech box/intercooler with either a Vortech or Procharger blower is much more efficient than any Roots blower setup. If memory serves, I've read on this site that Dean Nickerson has made over 950Hp with a R-Tech setup on an iron-headed 496 (I think) with a single 750 cfm carb. Try that with a Roots. I personally prefer Procharger blowers but I think Tom only sells Vortechs with his complete kits. Either brand of blower will make tons of power with an R-Tech box and intercooler, provided its properly tuned.
Just my 2 cents...

Turbojack

Yep, it will work. This is a picture when we started to see if it would work. I do not have picture on this computer to show finished product.

Turbojack

Here is final product. Looked & works better then the old procharger intercooler. Not sure how much more HP but efi O2 sensor is giving motor 7% more fuel at wot then before. Also air temp went down quite a bit.

RJBBC

A few questions to defend roots style superchargers. Why has Mercruiser never used a centrifugal supercharger on any of it's blown engines? How about the automotive industry, can you think of many production engines with a centrifugal style supercharger? (4 banger super tuners come to mind) Correct me if I am wrong but Mercedes uses a roots style supercharger on it's AMG series of cars. Ford put a roots style supercharger on it's supercar the GT. Efficiency at WOT is important, but what about a broad power band, the way it looks bolted onto your engine, and how does it sound?

tomcat

OEMs use Roots blowers because they are cheap. It is also an advantage to them that the intake, intercooler and blower are basically one assembly. They are much less efficient than centrifugal blowers, and their mounting position restricts intercooler efficiency.

Here is some info on Roots vs centrifugal.

1) Dean Nickerson originally had a B&M 250 blower making 650 HP on a 496 engine. With a bigger Roots blower he might have made 700 HP, but instead he switched to a centrifugal blower and made 850 HP. Then he added an Rtech supercooler and made 950 HP.

2) We recently replaced an dual carb 8-71 system on a 555 CID aluminum head engine with solid roller cam. With the Rtech system, one Nickerson carb and less cam timing the boat picked up 7 mph.

3) The attached graph compares the HP curves of two similar boat engines. The Roots is "state of the art" with intercooler and twin carbs. The centrifugal is "state of the art" with an intercooler that is about 4X the size and EFI.

Yes, the centrifugal can and does use more boost on pump gas. It can usually use less cam for the same HP, and doesn't need to make the same compromises on compression ratio, fuel and timing. As a result they are much more civilized around the dock or idling through no wake zones.

As far as power band, remember that most boats operate between cruise and WOT. Cars are also quickly brought into higher RPM range when racing. Both cars and boats have limitations on how much torque can be applied at low speed before tires spin or props blow out or drivetrains break.

Looks and sound are pretty much in the eyes and ears of the beholder. You might get a dyed in the wool Roots guy to jump to a screw compressor because of the similar mounting position, but the centrifugal is a stretch, and twin turbos are just too far off the beaten path for him to even consider. So I can't help wondering what the Roots guys will think of this...

Turbojack

Tom
In your dyno run did you run it lower then 3600. I am wondering how big a difference the less boost of the centrifical makes below that point. Is there a good reason why they match at 4250 rpm's?

I know once on plane & cruising at any speed over 2400 once I nail the throttle I am at 4400 rpms, & the rpms start going up from there. So where the roots has more bottom end it is a mute point.

RumRunner

Tom,

Have you ever done a comparison test using the same amount of boost (same engine of course) between a Roots & Centrifugal and measured the difference in cylinder pressure, TQ, & HP between them?

tomcat

Hi Jack:

No particular reason for crossing at 4250 RPM, you could cross earlier with a smaller pulley on the centrifugal, if total boost was still within the octane limits of your gas. At lower RPM, the Roots has a bigger advantage and Roots engine builders sometimes trade this away by using more cam duration to help in the upper ranges where the Roots is starting to fall off.


Hi Doug:

If you keep boost pressures the same, cylinder pressure is the same, everything else being equal. But torque and HP measured at the flywheel will be lower on the Roots engine because more power is lost off the front of the crankshaft to drive the blower. As you increase the target boost level on both engines this difference becomes more significant, not just because of differences in drive losses, but because intake air temperatures are higher on the Roots engine.

This is typical of the results of magazine tests,where boost levels are held at a certain level to make the test "fair". But the true test, the one you never hear about, is how much more power the centrifugal can make when boost is only limited by what you can run safely on the gas you intend to use. In this case the higher efficiency and larger intercooler that you get with the centrifugal blower raises the safe boost level and you really start to pull away from the Roots. The smaller pulley that you use in this case also lowers the RPM at which the centrifugal HP exceeds the Roots HP, so the gains occur at both ends of the scale.

RumRunner

Tom,

Since you're going to be running different intakes between the Roots & Centrifugal styles I would expect to see the cylinder to cylinder pressure to be a little different, even with the same boost levels.

I agree with the efficeny factor of the Centrifugal vs. a Roots style, but the increased boost you're capable of running wouldn't have anything to do with the style of supercharger, but with the ability to use a better intercooler with a centrifugal vs. a roots blower. Boost is boost, and when you compress air to increase pressure the increase in temp. should be very close (yes being a remote mount, vs engine mount should help minamally).

An interesting test would be to run a crank driven roots style supercharger vs. a centrifugal both blowing through the same carburetor in one of your intercoolers. Than someone could see the actual parasitic lose of the superchargers themselves. If one wanted to get really trick, you could actually have them driven off of another source to eliminate drag. At that point you would think the numbers should be identical other than how quickly the engine built boost.

Are you going out to the SEMA show?