I am in the process of completly redoing my truck. it is a 92 dakota with the 3.9 and a 5 speed. this summer im looking to rebuild the engine. right now im torn btwn a built 3.9 or a built 5.2 but i digress. i was wondering about the pros and cons of superchargers and turbos. i know that there is turbo lag, but i dont know a person who doesnt love the sound of a blowoff. also what kind of availibilty is there for those two engines. nothing to crazy like 20 or 30 pounds of boost, but i definatly want to house those annoying hondas running about my city.

Any help would be appreciated.

Joe

 

Perfect time to test out my personal theory on Turbos and Superchargers. See what everyone else thinks about this:

Turbo: Uses exhaust to spin a turbine, puts out lots of boost needs exhaust velocity to really start working (reason for lag). Because it isn't much help at low RPM makes big power gains higher in the rev range.
Supercharger: Engine spins the turbine, always making boost, doesn't make as much boost as Turbo, no lag. Tends to help through entire rev range, makes much more power at low rpm than turbo will.

(for the sake of this argument I'm only going to consider twin screw superchargers, roots is way to inefficient for the street, centrifugal are just belt driven turbos I don't like 'em)

How to apply:
To get the most out of an engine area under the torque curve is key (not HP, this number is calculated and does not factor into vehicle performance).

Small engines (4cyl, 6cyl, small v8s) tend to like high revs, and already make power at high revs. Therefore something that only adds to power at high revs doesn't make much sense. Supercharger is the way to go, boosts up the torque curve at low revs, and gives additional torque at high revs.

Big engines (big V8s, V-10s, etc) don't enjoy revving high, already make loads of power at low RPM, generally move so much air there is great exhaust velocity at low RPM. Turbos are wonderful for this, they don't drain any power from the engine at low RPM, the engine doesn't need anymore there anyway, boosts up the torque curve at higher RPM where is was falling off before.

So, whaddaya ya'll think? Little bit outside of conventional thinking, but if you think aobut it from an engineering standpoint I think it makes a lot of sense.

So, trukn. My answer to you is if you build the V6 go with a supercharger (twin screw, like Kenne Bell is the king). If you build the 5.2, it kinda falls into a grey area, it isn't big enough to be a big engine, but it isn't exactly small I've always like the thought of sticking a twin turbo setup on mine, though.

 

i like the way you think Batphreak. i really like that twin turbo idea. any ideas on a cost for those turbos, along with what i would need to mod the engine with so i dont blow it up?

 

Very true, and thought-out. I totally agree.
I was thinking about a motor swap and supercharging my dakota but stuff happens and money goes other places so im low on the cash right now. I have a 2.5 so instead of trying to afford going all out and spending a great deal, Im looking into turbo-charging my truck with an older turbo off a used chrysler or dodge car. Ive been told that the leBaron turbos need the minimal fabrication to work and that the daytonas may work too. It ought to be a pretty interesting project. Any suggestions? Im not exactly looking to be that fast, i just want to do it for fun and the experience.

 

Depends on what you're using it for... If you were building a car for the drag strip, you're going to spend 90% of your time in the upper end of the rpm band, so a turbo makes infinitely more sense. The only time you'd experience turbo lag is in first gear, a properly sized turbo should be at full boost by 2000-2500 rpm under load. And if you're fwd like me, instant power means instant weight transfer off the front drive wheels. Bad idea... RWD vehicles might like that prospect though, help lower your 60 ft time.

For that extra grunt around town (and the wannabe stoplight street ricing), the typical driver isn't going to rev that high or floor it for very long, so it's nice to have the power instantly on hand, assuming you have the traction to handle it... If you're not looking for absolute max power, just some help around town, the a supercharger might be the right answer.

Autocross is a toss up and fwd/rwd is a big consideration. I rarely leave 2nd gear in my neon and use the whole rpm range, shifting (if needed) at 7200ish on the top end, and try not to let it drop below 3000 through a turn. Being fwd, "powering out" of a turn is no good, just loses traction up front. A rwd might make better use of a supercharger, hard to say. I realize a lot of the newer, sportier cars have switched over to superchargers. The Mini Cooper S just gives us hell in G-Stock and DSP. But maybe light weight, shorter wheelbase, and a factory installed limited slip have something to do with it... The Cobalt SS and Ion Redline are easy pickins... even with my non-turbo '95 Neon...

I've toyed with the idea of forced induction on my car. Turbo makes a lot of sense, and a lot of people have done it with great success. But I have a few specific goals I want to meet instead. Maybe next vehicle...

My 2 cents... Best of luck!

 

krc makes everything you want for your 3.9 dak and can send you... well... low on cash......the vortec supercharger isnt cheap the injectors arent cheap and a new stand alone management isnt cheap but sure as hell cheaper then a superchips programmer!!! The Torque converters arent expensive until you get into HP VIPER brand. I must say tho if you did supercharge it, it is still pretty rare and you can get props for your individuality b/c most ppl drop their 3.9s for the 4.7s or 318s or 360s which I think is the easy way out...


Fabbing a twin turbo outta a 3.9 isnt impossible...the already low compression can get you buy w/ it and the header placement can keep you from your system choking...3.8 stangs benefit from T/Ts and I think daks could benefit too. Here is a s/u if a custom turbo fab job that dynos 400 rwhp... Use 2 junkyard turbos from 1st gen eclipses, Drill your own oil lines, run a collector, intercooler and the whole bit...krc sells your cams, and injectors, and I know a guy that will make you top quality turbo manifolds for it...heres the illustrations...

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yeah....

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Here's a good site: http://www.turbochargedpower.com/Tur...%20Blowers.htm

 

Well I like the way this discussion is going. My big question is what are you going to be using the Dakota for? Turbo lag isn't a big concern anymore with ALS(Anti Lag System). If you're just lookiing for go fast snap your neck back speed go turbo. If you want something that gives a steady gain and or hauling then supercharger is the way to go. either one will work, but in a Dakota I'd probably drop a vortec on it... Unless I planned on spending some time at the strip in which case I'd be looking into a garrett.

 

depending on the moeny you have to spend you could do both, but from the sound of it you don't really want that confusion. anyway just a thought.