Anyone ever supercharged a diesel? Whay are the pros and cons?

 

Really the only thing you will get on this is educated guesses and strong opinions because there is no conclusive evidence that the SC does much.

The pros..... well, its better than N/A.

The cons... its not as good as a turbo.

Turbo = free power... supercharger is not free power, and I personally think its almost a wash. A blower is going to take almost as much to turn as its going to add.

 

The problem with a supercharger is it will be building boost whenever it is running. On a gasser the throttle blades keep from boost until you open the throttle up. No air throttle on a diesel, air is wide open and the throttle is actually metering the amount of fuel. With boost all the time, you will be bleeding off or compressing air for no benefit when less than full power needed.

The beauty of a turbo is that it makes boost when you want and not boost when low power. The turbo also uses heat and exhaust volume energy in the exhaust that is otherwise lost, whereas the supercharger needs crankshaft power to turn it. So a turbo is more efficient.

The old Detroit Diesel engines are a 2 cycle and need the positive air pressure to force clean air into the cylinder. So they have superchargers. But our IDI are 4 cycle and boost is only needed to increase power, not to make the engine run.

 

Most superchargers actually have bypass valves built into them that prevent uneeded boost at lower rpm and also prevents parasitic loss. Also while there is a bit of power lost from an SC, one of the advantages is that boost comes on quicker with a supercharger than a turbo. Due to how low revving our engines are (or an diesel for that matter) the supercharger will produce boost at or right after idle when they have the proper pulley on them. They just have to be set up to have max rpm and max engine rpm happen at the same time. That is how you can get the most boost down low and max boost up top. There is also a guy over at OB who put an M90 on his but he hasn't quite finished it yet iirc. Also Empire Diesel sells Procharger kits for Powertrokes, Duramax, and Cummins. They seem to make decent power and spool really well. Here is a video of their setup on a 7.3 and 6.0.

Empire Diesel procharger Ford 7.3 - YouTube
Empire Diesel Procharged 6.0 - YouTube

Here are some threads over at PSN for the 7.3 kit and 6.0 kit. The guys love them.

Procharging a 7.3 - PowerStrokeNation : Ford Powerstroke Diesel Forum
Little more 6.0 Procharger info - PowerStrokeNation : Ford Powerstroke Diesel Forum

Also I am putting an Eaton M112 on my 7.3 idi. Eventually I will be able to show how they perform on one of our diesels.

 

Those rigs are pretty dirty. I wouldnt mind seeing someones idi supercharged, might not be as efficient as a turbo but meh, idk.

 

Exactly. And if you add a big enough turbo you will have the power up top and plus really good spool up down low...

 

I want to run a couple Shelby GT500 H122 eatons on my IDI. But I've got way too many projects to get done before I even think about doing that..

 

I heard the H122 is a decent unit. I'd be really curious to see what it did on an idi. Would you run it by itself or with a turbo blowing into it?

 

I want to run two H122's with an intercooler, no turbo.

 

There is a guy named Mick over at the Diesel Place who used to run two centrifugal superchargers on his Duramax and one time said that from 0-3000rpm that he had never felt so much power down low but then he went on to say that there was a lot to be desired up top. That is why he liked running a turbo with his supercharger setups. He said his Duramax ran best with the turbo blowing into the SC and that is how he made the most power with a supercharger too. He made 800+hp with his setup like that. Not bad at all. Also check out some of the stuff Banks has done. They have a supercharged Duramax making 1500hp/1500tq and it revs to 6.5k. That is a pretty high revving diesel...

 

The Eatons operating range match up quite well with the IDI. Running two should move enough air to build a decent amount of boost. But It's still going to be an IDI. It's not going to make 800hp.

As for running the centrifugals and lacking top end. That should be just opposite. They have to build boost like a turbo. It should lack bottom end and have a strong top end.

 

It is a bit different on a gasser than on a diesel. They are geared to provide boost earlier than they do on a gas engine due to the limited rpm thus run out of air in the top end of the rpm range. That's not to say they won't make decent power though. And I know you aren't talking big power. I was just making generalizations from Mick's experiences with his setups. Two superchargers would be cool as heck though.