I have always wondered why turbochargers seem to be the best option on modern diesel engines. Is there a reason that superchargers fell by the wayside? What are the advantages/disadvantages of each?

A turbo is essentially taking a waste product, and turning it into something useful. A supercharger absorbs power to make power. A blower uses power from the crankshaft to turn the rotors. A turbo doesn't rob power, but the lag is a downside. With a belt needed to turn the blower, where are you going to put it?

That makes sense. Is there any advantage to a blower?

surewhynot said:

That makes sense. Is there any advantage to a blower?

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Theres no lag, and the power potential is greater, IMO

Mmmmmm, how about a combo. Ohhhhhh, I'm getting excited just thinking about that idea!!

"To the moon Alice!"

Also the reason why they usually use turbos on diesels and blowers on gassers is because the volume and pressure of exhaust from a diesel is much greater than that of a gasser. More volume & pressure = more boost for a turbo.

Clarification: For those of you who don't know, a turbocharger is driven by the exhaust.

I was just going back to the days of the old Detroits with the blowers.

surewhynot said:

I have always wondered why turbochargers seem to be the best option on modern diesel engines. Is there a reason that superchargers fell by the wayside? What are the advantages/disadvantages of each?

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It is really a question of application, and what you are trying to accomplish. They all accomplish basically the samething and that is to increase the air pressure above 14.7.

Supercharges generally produce less heat overall and do not cause any extra exhaust backpressure. Roots & Twin screw supercharges make most of there power in the lower RPM range while centrifugal supercharges (look like a turbo but are belt driven) make most of there power in the upper RPM range.

Supercharges can increase power output by up to 100% but they do use about 20% of an engines power to propel them with the belt. Supercharges have no lag time which is a plus in certain applications.

Turbocharges use the waste exhaust gas so the power loss is only related to exhaust backpressure & elevated intake air temp.

In a diesel application the only type of supercharger that would make sense would be a centrifugal unit and it will use more power to produce power than a turbocharger. Turbocharges do have a lag time however, but for genereal purpose diesel use this is not a problem.

Basically it gets down to which unit will provide the power band required for the least cost. Fitting a roots or screw supercharger to a diesel would be difficult since most (roots especially) are large and would project out through the hood.

Centrifugal supercharges are expensive in comparison to turbocharges and the benefits of the centrifugal supercharger does not outway the lower priced turbo charger.

If you notice Top Fuel & Funny Cars run roots blowers because they are simple and provide instantaneous power off the line. But Formula 1 cars run turbocharges. Different applications for different goals.

Bottom line it is just a matter of matching the proper air compressor for the task at hand, cost, space availablity etc all play a role in it.

On the old Detroits, the blower was necessary for the engine to run. Without it, the cylinder would not fill with the fresh intake, nor clear of the exhaust. They were a two stroke diesel, the sleeve had a bunch of holes about 1/3 down from the top. The blower served to push air in to fill for the next compression, as well as force the old exhaust gasses out. They even put turbos on with the blowers sometimes.

surewhynot said:

I was just going back to the days of the old Detroits with the blowers.

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Ahhh yes, the scream'n moan of a 71 series Detroit.......a sound I would really like to forget that my, to this day, ringing ears won't let me....

We still have a couple of rollers with 53 series Detroits in them and I now wear ear protection albeit a little too late...

Blue Goose said:

Ahhh yes, the scream'n moan of a 71 series Detroit.......a sound I would really like to forget that my, to this day, ringing ears won't let me....

We still have a couple of rollers with 53 series Detroits in them and I now wear ear protection albeit a little too late...

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I remember servicing those things. Get on a creeper at one end of the truck with a clean uniform, climb out the other side looking like you've been working a week non-stop.

If they stop leaking they aren't running properly...

When I worked in the quarry up north, two of the drilling rigs ran 6v71's. The first time I heard one, I fell in love. For almost 2 minutes. I learned to hate the noise of them screaming constantly.

blackhat620 said:

...Turbochargers do have a lag time however, but for genereal purpose diesel use this is not a problem...

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If the system is setup with the proper CFM turbo lag is almost completely eliminated and it will not have ill effects in the upper RPM range.

1970Custom said:

If the system is setup with the proper CFM turbo lag is almost completely eliminated and it will not have ill effects in the upper RPM range.

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How will that take out lag? Isn't lag due to the time it takes to spool the turbo?

IIRC, the Rolls Royce Merlin aircraft engine, famed for powering the Supermarine Spitfire as well as the P51 Mustang (among others) has a TWO STAGE supercharger that was run directly off the crankshaft at the back side of the engine. If you cast the block so you could run the blower directly off the crankshaft, you'd minize the power loss..............and with a two stange blower, you wouldn't have the variable turbo problem of the 6.0, and the wasted space of the dual turbo setup of the 6.4

Here's a wikipedia link to the Rolls Royce Merlin

http://en.wikipedia.org/wiki/Rolls_Royce_Merlin

Gunner

6L PWR said:

Isn't lag due to the time it takes to spool the turbo?

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yes, the larger the turbo the more CFM it takes to get it to spool but will give mad power up top (ever listened to a turbocharged diesel puller, that chugging as they throttle up is the turbo) a small turbo will spool faster due to needing less CFM to spool thus having less lag but if you go too small the turbo will run out of steam before the engine does.

Fellro said:

On the old Detroits, the blower was necessary for the engine to run. Without it, the cylinder would not fill with the fresh intake, nor clear of the exhaust. They were a two stroke diesel,

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And they were some of the noisiest, most cantankerous to start in the morning, smokinest motors on the face of the earth... but you couldn't kill 'em!

.......and you drove them like you were mad at them...