once and for all which is best



I'm going to turbocharge /supercharge a 300 going into an F150 with aod and 3.50-1 axle running 235/75-15 most of the time and for offroad 33's . I will pull a trailer (24ftholiday trlr) rarely . I want low end power as I don't ever expect to see 4000 rpm most often 1800-2600 . Which is the best unit(Irealize there are always compromises and mntg problems) but in a perfect world ? thanks in advance for the input
What is the best "What?" You forgot to mention the part you are looking to install... :cry:
He wants to know the best turbo or supercharger for his application,

Well, you ready for a lot of unsubstantiated "expert" opinion like mine? You can rule out all centrifugal belt driven blowers (Vortech, Paxton, Powerdyne, etc.) They make boost in proportion to RPM, not to load so they provide little or nothing at 2000 and probably require more revs than you want to run to build full boost.

Positive displacement blowers (Eaton, GMC, Whipple) provide a constant boost throughout your RPM range, whether you need it or not. Your 300 would act a lot like a 390, and drink like one. They can be highly entertaining. :LOL: Other than the fuel consumption issue, the only downside is the work necessary to mount one. You're going to need the services of a pretty good fabricator and a machine shop to get everything built.

Turbos basically work in response to demand. Mash the stupid pedal, the increased gas flow spools the turbo up and you have boost. Come to a hill trailering with the cruise set and the turbo will spool up and pull you up the hill then spool down at the crest, almost transparent. They have to be properly sized or turbo-lag will kill their performance. Turbos require some fairly simple fab work to install, but the controls involved are a bit more complex than a supercharger.

My personal pick (cost no object)? For a hot-rod I'd go with the Lysholm type of positive displacement blower (Whipple, Kenne Bell) they are by far the most efficient of the breed. Second choice would be an Eaton. For building a tow rig I'd go with a turbo, either a T03 with Super 60 trim, a T04B with S-3 trim for a bit more RPM or possibly a T04E with 40 trim if I was going to crank up the boost. If dollars come into play then the turbo wins hands down.
I'm not a tubo expert but the only turbo I'd look at would be a waste gate turbo. You will get more boost at the lower RPM's and more Horse there also. It's neet to run a diesel with a waste gate turbo. In many cases they don't lose horse power as they lose RPM's but the fuel effencey increases at the lower RPM's some accually will develope more horse as they lose RPM's. Nothing is better than turning less RPM's, haveing more HP and higher fuel effencey.

Here's a hint: EVERY SINGLE 18-wheel truck on the road, towing up to 80,000 lbs, is equipped with a turbocharger. Virtually no new ones have a supercharger. :idea:
8) using a small turbo builds boost quickly but you need either a wategate or popoff valve to limit the boost pressure. i like the popoff valve, but if you choose to use a wastegate, use a pto(part throttle open) design for maximum efficiency. a pto gate is open when you are running under light load thus minimizing backpressure, and closes when you need it to to maximize boost.
From what I know, a properly matched turbo wins over every other combo.This is because most people want to use there ride for dual purposes, a turbo makes cents and $$$...your not pumping heat and using fuel at part throttle, but when the hammer goes down, it's all fire and brimstone, just like a good V8.

If your lazy but have a great fabricator (like me), a super-charger is a simple modification. Make sure you get something that suits you.

This Bob Fischer built GMC 471 Supercharger has been modified with a custom designed and manufactured snout by owner. It is fitted with an Airconditioning clutch to be able to engage and disengage the blower rotors dependent on requirements. Just like Mad Max


See this site for an example of what an Aussie does with 390 and a supercharger! http://www.turboclub.com/RTO/06100005/amc_javelin__rto_06100005_.htm

I'm bolting a Rootes-type Supercharger to my 250 cross flow Hybrid, but its only because I got the 'charger cheap and have colleges at work with years of supercharger experience to help me out with them. Truck mechanics love turbos, but old dieselGMC/Rootes mechanics who've worked on fishing boats and Pommy 2-stoke trucks know how to make a supercharger survive!
Wastegate vs. popoff depends on a couple of things:

On carbed applications, draw-thrus need a waste-gate, blow-thrus can use either as can dry manifold EFI setups. Wet manifolds and popoffs can create some spectacular pyrotechnics, not good.

When a waste gate opens, it dumps the exhaust gas and causes the turbo to spool down, a popoff merely dumps boost and leaves the turbo spooled up. If you autocross or roadrace, the popoff has some real advantages.

If you've got everything else sized correctly, you shouldn't be using either of them very often
So wouldn't the pop-off be better for off-road? Speaking in terms of mud here; you need the power to get the meats turning. If a wastegate lets the turbo spool down, you lose the gained power, correct? But a pop-off doesn't spool down, which means you keep the gained power. Am I correct, or am I just utterly confused? I think it's the latter......
The purpose of both the opoff valve and the wastegate is to keep the turbo from overboosting...sooo...

When the wastegate opens and lets exhaust gases bypass the turbine, it is merely just keep the exhaust gases from spinning the turbo faster. yoiu dont loose boost, becasue if you lost boost, the wastegate would close and your boost would just rise up to a certain point again. The wastegate actuator is adjusted to a certain boost setting. The actuator is activated by boost pressure...soo...when the boost pressure gets up to say for example 10 psi (where you may possibly want it) overcomes the a diaphragm in the wastegate actuator and therefore opens the wastegate relieving the turbine of exhaust gas pressure. Its a regulator.

The pop off valve is a valve activated by a certain boost pressure as well. But it actually relieves boost pressure in the intake when it gets too high. So the turbo will keep on spooling up if your RPMs are still going up.

This makes the turbo spin faster than it actually needs to (kinda doing useless work)

I think a wastegate is a better regulating device becasue it can keep the turbo from overheating from excessive RPMs. You get constant regulated boost and no excessive RPMs from the turbo.

It also depends on the turbo your using. If its sized correctly, most likely it wont have a problem with overboosting or overspeeding the turbo. In that case, you would not need either the wastegate or the popoff valve.

So you dont "loose" boost, it jusr stops at a certain psi.
Turbos are on big diesels because the high amount of heat in the exhaust naturally lends itself to efficiency (heat drives a turbo, not raw airflow). S/Cs of any form can't match the efficiencies at typical diesel rpm's or loads.

For your 300, the Lysholm or Whipple would be primo- but very $$$. A turbo won't be much cheaper, despite what some say. I love turbos, but I've also learned that they don't come cheap when you factor in all the additional items needed. The cheap way would be to adapt an Eaton modified for wet flow (sorry- I couldn't remeber if you had an EFI 4.9). You could get away with an M90 or a M112, and make plenty of boost down low.

Going from a 29" tire to a 33" will affect what rpm ranges you cruise and tow at; I'd suggest drivetrain changes, too.
I'm running propane with an efi intake, head and exhaust manifolds.I like excutes' idea with the s/c and a/c clutch but would it have enough umph to handle the s/c on startup especially at speed?Would a cooler be necessary for the turbo at relatively low boost (5-8)lbs.?As far as size goes I tried some websites with calculators and get either T25 or T3 and even T4 with various a/r quite a spread - still confused.Thanks for all the input.
When the wastegate opens, it dumps the exhaust flow that causes the turbine to spin, the compressor wheel is still seeing the pressure that caused the gate to open. That pressure acting on the now undriven compressor suddenly and dramatically slows the turbocharger down when the gate opens. In order to regain boost, you have to bring the turbo back up to speed.

With a popoff, the valve simply dumps excess boost maintaining the set pressure of the valve and allowing the turbine to remain spooled up, no need to regain lost RPMs.

Usually i just leave it be as i was thinkin of doing with this topic. But i guess ill give it a try. Your knowlege is prolly much more expanded than mine, considering im only 19 years old. But ive been studying turbos alot lately and learned alot about them. OR.....i just cant get what you just talked about through my young mind! hehe...

The wastegate only opens partially dumping some exhaust gas out. But it makes no sense to slow the turbo down after reaching a desired boost pressure. Thats just like pulling your foot out of the throttle. So the wastegate isnt opened fully at one time. Or else the turbo would decrease in speed, which is not what you want.

The wasteate actually starts to open early in order to smoothly regulate the boost pressure all the way to the desired boost pressure. Once it is at that desired boost pressure, the actuator will regulate the wastegate valve to keep enough exhaust flowing through the turbine and not too much out of the wastegate.

The part about the boost pressure slowing the compressor wheel down makes absolutly perfect sense. And it will to a degree, but the turbine still has exhaust gases spinning the turbo shaft to keep it up to speed and keep boost pressure in the intake side of the system from the regulated wastegate.

This is how i learned how it works from the Cummins instructor that taught a class here at college on the Cummins B and C models.

I dont know if you were confused or i am, but its no big deal. I love to talk and figure stuff out. I dont like telling people whats right or wrong...but people do it to me all the time...im usually too shy but i guess even us young people have to learn somehow....

I love this site...