Supercharging a diesel

[alteredspeed]

This may or may not be a dumb question. Why doesnt anyone super charge diesels? They used to due it wit 6-71 and 8-71' s didnt they. Why cant I put a centrifical supercharger on my 6.2. Price is not much diffrent than a full turbo setup. Just Wondered.

[bigeasy]

A super charger takes engine horsepower to operate.
A turbo uses waste energy so it is a free power gain.
Also the turbo takes no drive belts.
The super charger will have to be accommodated at the front of the motor which is already loaded with accessories.
There is usually extra space around (or found for) the exhaust, to power the turbo.


Then there is the matter of compressing air makes heat.
So it is easier to add an intercooler to a turbo / more free power.
A blower nearly impossible and a supercharger got ruled out in the first equation.

[Shikaroka]

Power from a turbo is not all free, although not as much parasitic loss as a supercharger.
A centrifugal supercharger would be just as easy to intercool as a turbo, if not easier is some cases.
Turbos are usually less maintenance and last longer, and they are generally cheaper. I am sure there are other reasons, but I don't see why a supercharger wouldn't work on a diesel.

[DmaxMaverick]

The supercharged Detroits are supercharged for a different reason. They are 2 strokes, and need the air pushed into them. The superchargers weren't there for power, but for function. The HP Detroits had/have both, a charger and turbo. The charger for low RPM's, and the turbo for high.

There are a few supercharged 6.5's around. But, the result has been less than stellar. The ROI (power-wise, generally less than 20%) is not impressive. The supercharger requires crank power, and the 6.5 crank accessory drive system is taxed to the hilt as it is. Not to mention the potential for crack issues even in stock trim. While supercharging would be a fun project, it would not be at all practical for all but the most adventurous. Certainly not for a daily driver with any sense of economics in mind.

A turbocharger is about as close to "free" power you can get. It isn't really "free", but has the lowest overhead of all enhancements. A properly installed and setup turbo will be maintenance free for the life of the engine in most cases. Superchargers are generally short-lived and require relatively frequent maintenance.

[More Power]

Sure, the 6.5 has been supercharged! www.marinediesel.nu offers both marine and on-road packages.





http://www.whipplesuperchargers.com/ also offers supercharger kits for the 6.2/6.5. They are popular with 6.2/6.5 Hummer owners. The above pic was taken during The Diesel Page's 2001 Rendezvous in Ohio.

What I've read: A super is about 50-60% as efficient at boosting power as a turbo. A super is better for an off-road diesel, cuz it builds boost sooner.

Jim

[Craig M]

Jim has it right. If pure power rather than power and economy are your goal, than the supercahrger is ok for you. H1 Hummer owners add the supercharger to the 6.2's because they do not care about fuel economy and want more power from their expensive toy (and usually have more money to burn than the rest of us).

[Robyn]

Just a little tech stuff here.

The 71 series detroits ( inline as well as v type) as well as the 53 series and the later 92 series engines being of a two stroke design have 2 or 4 valves in the head and a series of ports around the middle of the cylinder.
When the piston drops below the ports the exhaust valves open at the same type and the pressure from the blower thats in the "air box"
( The valley on the V engines) pours into the cylinder ports and blows the exhaust out the valves scavenging the exhaust gases and replenishing the cylinder with fresh air for the next firing cycle.
The detroit 2 stokes have a distinct exhaust note due to the roots type blower plus the fact that each cylinder fires every time.

The detroit 2 strokes have/had the advantage of offering very high power to weight ratio.

The down side to the two stokes is that they do not lug well. I detroit 2 stroke functions best when the engine is running at or near governed speed of 2100rpm.

Lugging a 2 stroke results in poor scavenging and very high EGT.
Another down side of these engine was the emissions.

The 60 series 4 strokes came out to get the companies truck engines into sinc with emissions standards.

The 92 series engines in the upper HP sizes were a real force to be dealt with for sure.
The 8V92 truck engines would produce 400 Horse power easily.

The 12V-71 T engines were a real monster.
These engines were two 6V blocks bolted together and 4 seperate heads.
The mechanical monkey motion to run all the injectors was massive.
Each injector has a fuel rack and all these have to be synchronized to work together. This stuff is all run off of linkage and is subject to binding if not done properly.

The governor that runs the whole mess is fastened to the front of the blower and the linkage from the fuel racks runs up some little tubes from the front of the head/heads.

A real treat is being around a 2 stoke that some clown misadjusted the racks and the thing runs away.

There is only one way to shut off a runaway detroit 2 stroke and that is by activating the emergency shutter on the blower.

Never ever ever run a 2 stoke detroit without the air intake screen and the shut down air hat on the blower.
These little monsters will suck all sorts of things in that you dont want them to.

I have seen an 8V92 run wild and if not for the quick thinking of another mechanic standing close would have scattered.
He grabbed a phone book and slapped it across the blower.

I was about 10 feet away and saw what was going on but was not in a position to do anything.

The detroits will make some Gawd Aweful RPMs very quick and at about 3500-4000 they come apart in large chunks depending on the particular engine.

Most detroit 71 and 92 series are set to run at 2100 RPM max.
Some firetruck applications will run a bit higher (2400)

One of these suckers running at these sort of RPM is sounding to the ears like 4800
It is a very impressive howl indeed.

Just a littlle history and info on the Detroit 71 and 92

Robyn

[Robyn]

Just a little tech stuff here.

The 71 series detroits ( inline as well as v type) as well as the 53 series and the later 92 series engines being of a two stroke design have 2 or 4 valves in the head and a series of ports around the middle of the cylinder.
When the piston drops below the ports the exhaust valves open at the same type and the pressure from the blower thats in the "air box"
( The valley on the V engines) pours into the cylinder ports and blows the exhaust out the valves scavenging the exhaust gases and replenishing the cylinder with fresh air for the next firing cycle.
The detroit 2 stokes have a distinct exhaust note due to the roots type blower plus the fact that each cylinder fires every time.

The detroit 2 strokes have/had the advantage of offering very high power to weight ratio.

The down side to the two stokes is that they do not lug well. I detroit 2 stroke functions best when the engine is running at or near governed speed of 2100rpm.

Lugging a 2 stroke results in poor scavenging and very high EGT.
Another down side of these engine was the emissions.

The 60 series 4 strokes came out to get the companies truck engines into sinc with emissions standards.

The 92 series engines in the upper HP sizes were a real force to be dealt with for sure.
The 8V92 truck engines would produce 400 Horse power easily.

The 12V-71 T engines were a real monster.
These engines were two 6V blocks bolted together and 4 seperate heads.
The mechanical monkey motion to run all the injectors was massive.
Each injector has a fuel rack and all these have to be synchronized to work together. This stuff is all run off of linkage and is subject to binding if not done properly.

The governor that runs the whole mess is fastened to the front of the blower and the linkage from the fuel racks runs up some little tubes from the front of the head/heads.

A real treat is being around a 2 stoke that some clown misadjusted the racks and the thing runs away.

There is only one way to shut off a runaway detroit 2 stroke and that is by activating the emergency shutter on the blower.

Never ever ever run a 2 stoke detroit without the air intake screen and the shut down air hat on the blower.
These little monsters will suck all sorts of things in that you dont want them to.

I have seen an 8V92 run wild and if not for the quick thinking of another mechanic standing close would have scattered.
He grabbed a phone book and slapped it across the blower.

I was about 10 feet away and saw what was going on but was not in a position to do anything.

The detroits will make some Gawd Aweful RPMs very quick and at about 3500-4000 they come apart in large chunks depending on the particular engine.

Most detroit 71 and 92 series are set to run at 2100 RPM max.
Some firetruck applications will run a bit higher (2400)

One of these suckers running at these sort of RPM is sounding to the ears like 4800
It is a very impressive howl indeed.

Just a littlle history and info on the Detroit 71 and 92

Robyn

[Yukon6.2]

Yes runaway detroits
I got a mechanic to change injectors in my fuel delivery truck one year.
Ever change injectors in a detroit i asked him?
Yea sure no problem.
Anyhow those words didn't ring true after i fired it up.....
he had one hand holding the rack back as hard as he could,the other holding a piece of plywood over the air filter intake and a scared look on his face
needless to say this was the biggest adrenalin rush i ever had,heres my bread and butter earner reving like no tomorow,about 3000 gals of stove oil in the tank,i grabed a filter wrench and spun the fuel filter off,seamed like it took forever to get it off,here i was about two feet from the screaming jimmy waiting for a piston to fly out any second.....
The engin lived for about year after then cracked a valve.
Needless to say,i'm allways a bit aprehensive about firing up a jimmy after it's been worked on.