i have always wounder what are the pros and cons of using a turboCharger or a supercharger, and why would someone chose one over the other. i know its likly to see more gains from a supercharger but how does it stack up to a twinturbo system. And can any engine be set up one or all of these without t he engine blowing up?

 

Well thats a million dollar question.

If you check out the read first, it answers most of it:
https://www.ford-trucks.com/forums/s...d.php?t=395697

 

I understand everything about turbos and superchargers but what I still can't figure out is how you plumb a single turbo for a V-style engine. Do you put the turbo in the front, back or what and the what do you do with the exhaust?

Gary

 

Well, it depends.
Ideally you want the turbo as close to the exhaust as possible.
The 7.3l PSD has it at the rear of the engine.
The 6.0l PSD has it on top of the engine.

A lot of people converting Lightnings to turbos are mounting the turbos at the front.
It depends on what space you have in the engine bay, whether you plan on running an intercooler etc.

 

How long can the piping be going from the manifolds to the turbo before it becomes inefficient? And why can't you use custom bent headers to flow right to the turbo? I would think shorty headers going to the turbo would help make it more efficient. And what about those catback turbo systems? They say they work and if they do, wouldn't it be easier to mount a turbo right after a y-pipe?

I'm not trying to highjack devilsword thread since I figured this would help give him some more insight on turbo systems.

Gary

 

Unless you're really carving up the vehicle and have the flexibility to relocate anything that's in the way, generally whatever space you have that's not against the wiring or EFI computer, is where the turbo goes. You will have noticiably less lag with a turbo mounted as close to the exhaust ports as possible, however the way vehicles are packaged under the hood these days that's really not all that doable.

If you're not crossing streams and rivers, there is plenty of space on most F-series next to the oil pan in front of the suspension, and that's not too difficult to bend tubing from the exhaust ports to that area. Actually, for my twin-turbo crewcab, I was thinking of mounting them behind my homemade "superbumper", as there's enough space there to fit at least one dead body

But then I decided to make things shorter, and put them next to the valve covers, over the wheel wells, and bake the paint off the hood instead.

 

Turbos and superchargers are essentially the same device, except in how they are powered.

There is a compressor housing that (heh-heh) compresses the air going into the engine above atmospheric pressure.

A supercharger drives that compressor by attaching itself to the crankshaft, whereas a turbo drives that compressor from a turbine that sits in the exhaust system.

If properly sized, a supercharger or a turbo system will give you excellent results. They key is sizing the thing correctly, then tuning the EFI afterwards to work appropriately.

It is typically said that a supercharger system provides more "snap" off the line because it's always spinning because it's crank driven.

That is usually followed by "turbos have lag" and "turbo systems can handle higher RPMs much better".

Those are vague statements generally made by the uninformed. Either system can perform extremely well "off idle" and not so good at higher RPMs, or, have "lag" off idle and perform well at higher RPMs. It's about size and scale just like choosing an intake manifold.

Obviously, a top fuel "rail" would want it's supercharger to be fairly useless at idle, and at peak efficiency at 8000 RPM, because that's the maximum RPM allowed to haul butt down the 1/4 mile.

OEM turbo systems were notorious for lag, because they were often designed as a "this fits on the 20 cars that we make" type solution, therefore a system of many compromises.

It's like choosing an intake... some work better at lower RPMs, some better at higher RPMs, usually not that good across the entire RPM band.

Having built both systems over the years on several different vehicles, I let my application and purpose of the vehicle dictate which I chose, but most importantly I allow heavy influence by packaging. Sometimes it's easier to shove a supercharger into an engine bay, other times turbocharging will fit better. I'm building a twin-turbo 500cid stroker for my crewcab, and my 93 Continental has a paxton wedged in there.

Either vehicle is (or will be) fun to drive

 

can you get more power from a super charged then a twin turbo? and why can you use both?

 

hmm... another question that really comes down to the application.

A turbo set up can provide HUGE amounts of power - but it has to be sized correctly etc.
A supercharger is probably not going to provide as much power eventually, but it can be tuned a whole lot easier.

 

Any properly designed system will outperform an improperly designed system. Turbo, or supercharger.

It's a matter of understanding what your realistic requirements are, available funds, fabrication ability, time and effort, and what you want the final result to be.

And you can stage turbos after a supercharger, or vice versa. It's been done before. The question is... why not design one system correctly from the get-go, and make installation simpler.

 

So which is better? Staging turbos before or after a supercharger? I would think the best set-up system would be to utilize the supercharger for low RPM power and then let the turbos kick in in the upper RPMs and let the supercharger supply less boost. Is there even a way to have a supercharger no longer supply boost one an engine hits a certain RPM?

Gary

 

Well it depends again on the sizing.

From a purely efficiency point of view, a twin screw supercharger at low rpms, and then having a clutch which deactivated it (Mad Max style), and your turbo coming in at higher rpms, as you are not going to have the rotational losses at high rpms that positive displacement blowers have, and at higher rpms (with a correctly sized turbo) you are going to have greater thermodynamic efficiency.

 

As a side comment to BigF350's comments regarding mad max... most twin screws have such tight clearance you can't flow sigificant air through them if they arent' spinning... so this makes for an interesting complexity.

Glube - if you're going to partake in the hassle of fabricating a turbo system, why not stage turbos. A smaller unit for lower-end RPM, and a huge one for higher RPM.

Even the OEM's play with staged turbos:
http://autoweb.drive.com.au/cms/A_54...wsarticle.html

It's certainly been done in the diesel arena.... by guys like us and OEMs...

And there are other ways to have reasonably smooth torque throughout the RPM band. My method is to use cubic inches for low-RPM torque while the turbos spool up, then have them carry things to redline (which will be about 4500, maybe a little less) on my 500cid stroker.

With 500 cubes... I don't need 30lbs of boost right off idle ;-)

I have a friend who is turbocharging an meticulously built 351W stroker (close to 400cid), and while that's built and done and so forth, his single turbo is sized where it's not overly useful until he approaches the 2000 rpm. He's thinking of nitrious for "off the line" power. Having driven his truck a few times while helping him tune it I personally don't think it's necessary. I could smoke the tires in 1st through 3rd, squeal them at highway speeds in 4th, and of course 5th is overdrive. His truck is already traction impaired as it is now... nitrious is only going to make that worse, considering he wants to push the "red" button during initial acceleration.

I mention it because maybe it's another solution for you. Nitrious is easier to cobble together than a second turbo.

 

Frederic, trust me I am in no financial position to try to make my own turbo system. I just find them very interesting and an easy solution to make more power out of vehicles when tuned properly. I just don't understand why manufacturers do not utilize forced induction more often instead of making a larger engine. Somewhere down the line, after I get out of college, I will want to try to fabricate my own turbo system.

Gary

 

Some manufactures like Subaru embrace turbocharging, others have had nightmares with it. Chrysler for example was really into turbos in the 80's and 90's - as we all know that's a good way to make a puny engine seem less puny. But remember the vast majority of the people in this world don't change their oil regularly and drive until the springs fall off, then are suprised something is broken and whine about the inconvienence. If the vehicle is under warranty, the manufacture/dealer get to eat it.

That is why I think turbocharging is not as common in the OEMs as I think it could be. Turbo diesels are different because it's hard to break a diesel, except for the diesel v8 station wagons GM made during the mid/late 70's gas crunch, though that was mostly due to stupidity in the engineering department (or bean counters telling the engineers "who cares, do it").

Having made several fabricated supercharged and turbo systems in the past, and embarking on yet another project, I have to say it's not unbearably expensive if you look for junkyard parts, rebuild them as necessary, and make your own exhaust and bracketry. What you're trading here is your time for dollars. It's still not cheap mind you, it's just less costly. I bought my pair of T4 turbos on ebay for $250 each, new sealed in the boxes, from some guy who didn't set a reserve price. You may call me "sniperman"

I'm making the exhaust manifolds out of "black pipe" which a 20' section costs me about $40 at home depot. 20' is more than enough to make two manifolds, including rejects due to mistakes. My 500cid is mostly junkyard parts, which will total about $2500 by the time I'm done plus incidentals (gaskets, paint, bolts I've broken and so forth).

Though, I've probably spent about $200 on electricity, spools of flux-core mig wire, replacing wire brushes and so on.

The tranny cost me $350 plus a 6 hour round trip of gas to go get it (also ebay). The rebuild kit cost me $179 plus shipping, and I spent a saturday rebuilding it. The clutch kit is a generic OEM replacement kit which was about $300, though I know that's going to fall apart with a twin-turbo 500cid stroker in front of it. I'll put it in as a "fuse" and once things are tuned I'll replace it with a centerforce or something along those lines.

All the EFI bits, computer, wiring harness scraps, injectors, MAF's and throttle bodies cost me about $300 by the time I was done, plus spools of white automotive wire to make my own harness. And about $15 in photocopies of wiring diagrams from a bunch of different vehicles at my local library. I also changed my mind on the EFI twice, originally from GM EFI to mustang mass-air EFI, and now to 96 F-series truck mass air. So $300 didn't need to be spent except I kept making engineering decisions on the fly because I wanted to work with "new stuff" and learn something in the process.

Add all that up... while it's not $20, you have to admit it's significantly less than what I bet you were guessing

But, I'll have probably 1500 manhours into the powertrain by the time it's installed, and running well enough where I can use the truck to haul stuff from Home Depot, and start the EFI tuning process.