Anyone out there have a source for a forced-induction system for the 4.9L inline 6? I've been thinking this would make many "ooh-ahh" points and be a cheaper, faster alternative over installing a 302 or 351. My 4.9 engine and fuel delivery is in fine enough shape to handle the system, so long as boost does not exceed normal streetable figures. I figure 4-6 lbs. would be plenty. Just an idea I have been kicking around...

 

First off, lets get serious.

Forget the Supercharger, too inefficient.

Go turbo all the way. I'm thinking something like a T3/4, from a 5.0 mustang kit, with boost coming on strong at 2000 rpm. Go intercooled too, try the one from a dodge conquest/starion, its should be cheap. Get an MSD BTM, FMU, BOV, something to fool the computer and all you have to do is play with the welder (downpipe and charge pipe) and you are done.

That would give you ohh-ahhs galore. Besides the tire smoking torque that the straight six already has a ton of.

I'd be impressed.

Randy

 

Hmm. Good ideas there. I was thinking along the same lines, that a 5.0 turbo would be the best way to go (I do a lot of welding and making up some pipes would be easy), no making up trick brackets to hold a supercharger and trying to find a custom belt, plus there's no shortage of underhood room for all the turbo stuff. I know the direction of my next winter project...

 

 

RGAZ: I am interested in learning how the turbo is more efficient than the supercharger. I always felt the supercharger was better, having heard of turbocharger problems with response lag and something bad that happens to them from the high heat (like the bearings get messed up or something?).

 

This is an age-old argument that really depends on what your goal is. Both Superchargers and Turbos have got a bad rap through the eighties for poor design, but the newer models in Supercharging and turbocharging has all but eliminated those problems. So if we take out the older design issues, lets look at pros and cons:

Turbo lag: Yes it does exist. But it is not due to the turbo taking too much time to spin-up. It geneerally is due to the fact that there is usually a large column of air between the compressor and the throttle plate. Now, is this a pro or a con? I think this is actually a pro for the application above. The 4.9L has awesome low-end torque but loses its breath as the rpms increase. So if you can set your turbo up to increase the torque at higher rpms, the truck will pull harder longer. If you put a supercharger on the 4.9, then you will have more torque down low and worse response at high rpm (the supercharger acts like an air heater at high rpm). So the truck would have great tire-smoking abilities, but wouldn't be much faster unless serious suspension changes were made.

Efficiency: A turbo uses wasted heat from the engine and a supercharger steals torque from the crank. A turbo can be as high as 70% efficient. A good supercharger is at best 40% efficient. The efficincy is a measure of how much compression you get compared to how hot the intake charge becomes. in general, superchargers will always add more heat than a turbocharger and a turbo system can allow for an intercooler where a supercharger generally does not.

Ease of repair: With the addition of more and more turbo-diesel trucks, the cost of repairing a turbo has gone way down in recent years. Spuerchargers have actually become more expensive to repair due to sealed bearings that are destroyed if they leak.

Perfomance: Superchargers add ppower in a linear fashion (roots type) while turbos actually are exponential. That means the super will not give you a good "push" feeling when its operating, the turbo will. This is purely butt-dyno stuff, but I really like when my turbo Honda makes everyone grab the "oh-sheet" handle when she gets going!!

Install: OK superchargers are going to win hands-down. So lets not go there.

Reliability: The newer turbos are now more reliable than their supercharger counterparts. This is due to two things: Full floating bearings, and water cooled bearings. The newer turbos use bearing sections that have floating bearings that reduce the harmonic vibrations which destroy turbos and they are also water cooled to reduce the coking of old turbos and you don't need to use turbo timers to let it cool down.

HERE IS THE BIG ONE!!
Gas mileage: Adding a supercharger will definitely cost you alot more at the gas pump. No matter what, the supercharger is pumping and more gas is being used. The turbo will only use more gas when you are into boost. That means at cruising speeds when there is no boost or if you shift before the boost comes on, your gas mileage will remain the same. Even better, the truck will act exactly like stock if you are not boosting. That means you can drive it everyday and not have to smoke the tires at every stop light.

That is just a few of the pros to turbo and superchargers. I have used and driven both on the same car and the faster vehicle has always been turbo-charged. All import drag-racers use turbos, the rally-cup champions are turbo-charged (Lancer and WRX), so why not get the best power for your buck?

Randy

To read more on turbos, consult "Maximum Boost", by Corky Bell.

 

Wow thanks Randy. A very comprehensive answer. Definitely some great advantages. I will save that one in my hard copy file and will see turbocharging in a new light. May even look up your book reference at the library.

Paul

P.S. Great term--"butt-dyno."