Boost Options

[rammertide07]

I asked this question early when I first started getting into diesels, never really got an educated answer. Maybe someone here can help explain a little better.

For creating boost, it just compressing air into the engine using a turbo. Why not use something like an onboard compressor? Using an electronic pressure regulator to give boost just like a turbo. It's instant boost. Only problem I see with the set-up is turbos probably last longer than brushes in a motor and compressors build up moisture. I don't see why you couldn't add an in-line condenser?? And if the compressor goes out, then you are just without boost....not sucking up oil. Or even using something like a blower Electric Turbo Boost Air Intake Supercharger 240SX Neon - eBay (item 280641275428 end time Mar-11-11 07:06:51 PST)

I'm sure there is a reason why it hasn't been done...just not sure why Probably a far-fetched cray idea

[907DAVE]

The purpose of a turbo is to convert the unused HEAT energy that the motor is generating, to something useful. If you use a belt driven or electric type of force induction you are wasting that energy and eating up more horsepower spinning a supercharger - compressor or alternator.

Make sense?

[dietoremain]

exactly what he said, your exhaust spins that sucker and creates a whole lotta power doin it.

[rammertide07]

Makes sense, but would it be just as beneficial to even up the con of using something like the alternator or direct drive?? Having the benefit of boost off the line, unlike a turbo...having to get rpms up to create the boost.

Plus the benefits of tuning of using something like compressed air. Instead of having to changed out expensive turbos to create higher boost, you could just open up the regulator. I saw in a marine/boating magazine where a coast gaurd boat was powered by a duramax with a supercharger feeding 2 turbos (not sure why they just would use the supercharger...just allowing more room for energy loss).

Has compressed air ever been tested on a diesel? Anythime I search for this I pull up stuff about on board air compressors and air horns.

[rammertide07]

Searched another way and found some stuff. I like the way one guy explained it:

"Basically, the objective of Turbochargers and Superchargers are the same: To force a larger amount of air into the combustion chamber, adding oxygen to the combustion process, increasing the force of the explosion, resulting in a stronger power output.

The basic difference is the way they are themselves driven, more than what they actually do to the engine.

Basic difference: Supers are driven by the engine power - Turbos are driven by the exhaust pressure, but in general, the idea is exactly the same.

Superchargers (blowers) are mechanical, and use a belt from the crankshaft to the blower axle to spin up and compress the air through the intake. A deficit of this way of doing things is that the force it takes to drive the supercharge is taken from the engine, reducing power output slightly compared to a turbo at the same pressure rate. A benefit however, is that the supercharger adds power in a very linear way. The more revs on the engine, the more revs on the blower, hence more power increase. This makes the power very smooth and easy to control.

Turbochargers use the pressure of the exhaust gasses to spin up a turbine. The benefit of this is that you have no mechanical strain on the engine, and get full effect from the added pressure all the way to the driveshaft. Deficit is that it relies on the pressure of the exhaust gasses to build, causing what is know as "turbo-lag", where almost no increase is found at low revs, but once the pressure is built up, the power increase is very sudden and can be hard to control. Another benefit is that the pressure can be a whole lot higher from a turbo than from a supercharger, easily higher than what the engine can handle, which is why turbo systems often include a valve - or "wastegate" - to allow excess pressure to bypass the turbo. This valve is the cause of the little whistling sound that turbos make when taken to the limits. Turbos are also known to "tick" after the engine has been shut off. This is the turbine spinning down.

Want power? Go turbo! Wan't torque and controllability? Go supercharger! Want quick and cheap fun? F*ck air - go nitrous!"

So guess thats why the duramax had the supercharger feeding the turbos. Instant pressure on the "exhaust side" of the turbo to spin them up faster and the turbos are capable of producing more boost...and the supercharger can keep them spun up even after engine rpms drop. Except I dont think boat engine rpms drop. I would see it as a benneficial set-up in something with a transmission though.

[rammertide07]

But there's always the option of getting the GTP38R to get that out-of-the-hole repsonse I'd be looking for. I wish the diesel sales site had a payment plan for some of the stuff. I actually talked to xtremediesel.com and they said they could set up something like that.

[907DAVE]

That's what credit cards are for....as long as you don't mind paying a little interest on your borrowed money.

[TwinTurbo]

Originally Posted by rammertide07

So guess thats why the duramax had the supercharger feeding the turbos. Instant pressure on the "exhaust side" of the turbo to spin them up faster and the turbos are capable of producing more boost...and the supercharger can keep them spun up even after engine rpms drop. Except I dont think boat engine rpms drop. I would see it as a benneficial set-up in something with a transmission though.

Just want to clear up this statement a bit - first I'm not sure what setup you were looking at but I don't think you could set them up this way, the setups I've seen the turbos feed the supercharger - so at low boost from the turbos the supercharger is creating a vacuum on the compressor wheels and basically making them freewheel. As heat and RPM build the exhaust begins to spin the freewheeling turbos faster and provide more air than the supercharger requires so there is pressure now between the turbos and the supercharger which enables the supercharger to compress it even further than just by itself - very similar to a compound turbo effect at peak power. Hope that makes sense - feel free to correct if I'm wrong.

[907DAVE]

They can be set up either way.

Empire Diesel has turned out a few rigs that have a ProCharger feeding a turbo.

I post more on this later.

[rammertide07]

I tried looking for the particular set-up/application I saw. But you can google "supercharger feeding two turbos" and it will pull up some stuff.