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Old 02-05-2001, 09:54 PM   #1
Jonnathan
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Cool Turbo Vs. SuperCharger

I'm thinking of getting a bit of forced induction going on my RS.
I've found a couple of Turbo kits and a SC kit. I've got a 2000 impreza, which can take upto around 240hp and stay fairly reliable with only an uprated clutch change.
Both the turbo and SC kits give about the same HP, I'm guessing the SC will have more power and torque at lower revs, and be more reliable ? Can anyone else offer some more advice on which choice I should make, and what the trade-offs are,
thanks : )
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Old 02-05-2001, 10:00 PM   #2
spt_impreza
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let the feuding begin

spt
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Old 02-05-2001, 10:00 PM   #3
Eric SS
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If you do a search you will come up with tons of information on this subject. More than I could possibly post

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Old 02-05-2001, 10:02 PM   #4
Midwayman
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Jonathan,
Its not a question of which you *should* buy. Right now its a question of what you *can* buy. The only supercharger is made by Rimmer, which is questionable at best. OTOH there are several turbo kit suppliers.

If you're really interested in the differences between turbos and superchargers, do a search and you find long long lon drawn out threads. Super vs turbo is kind of a holy war.
-B
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Old 02-05-2001, 10:43 PM   #5
Greg Sharpe
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I'm definitely a turbo monk. I'll add just this one factoid; Superchargers build boost proportionately to RPM, only reaching peak boost at redline; Turbochargers reach peak boost at their boost threshhold, in a properly designed street turbo kit that point is usually around 3,000rpm. And we all wonder why holy wars last so long? It's cause there are always new converts to fight over!
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Old 02-05-2001, 10:51 PM   #6
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Greg-- That applies only to centrifugal superchargers (Paxton, Vortech, etc,.) Positive displacement blowers (Eaton, Autorotor, etc,.) make peak boost down low and maintain it all the way to redline. This is why these types of blowers are unanamously favored by the small displacement import crowd.

Cheers,
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Old 02-05-2001, 11:25 PM   #7
Kevin Thomas
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Shiv,

I guess that's why you see the Honda Si in the latest SCC, even with it's high rpm range, still wasn't able to utilize the power potential of the Vortech supercharger since it builds peak power so high. It seemed like that Vortech kit wasn't running out of steam anytime soon.

I guess the good thing about the Vortech kit is that just like a bigger turbo, since it's not running at it's peak efficiency, it doesn't generate as much heat. This would be ideal for a non-intercooled Vortech running at low psi, right? I thought the power delivery of the Vortech on that Si was awesome, even though you could say it wasn't all being used very well.
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Old 02-06-2001, 04:47 AM   #8
brandon
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Shiv - Thanks for stepping up to the plate. It seems you're more of a turbocharger fan, but I really appreciate that you will defend the attributes of all types of tuning. The sooner we can clear mis-information from the boards, the easier it will be for everyone to make thier own educated decisions for thier own particular needs.
Having said that, and also that my car will eventually sit on the supercharger side of the fence; I don't think there are any good, reliable supercharger kits available in North America...for our Imprezas. If you want a SC, you're going to have to build it yourself. If you want fast, and you need a kit, then the turbo seems to be the only game in town.
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Old 02-06-2001, 05:48 AM   #9
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Rimmer is not the only Supercharger desinged for Subaru's.. There is Force One. I don't have the link with me at work, but I will provide it later tonight. They have a kit developed for the MY00-> 2.5L legacy engine (same as ours basically). It is a side winder kit and looks very nice. I found the info here on the I-club so do a search on "Force One superchargers" and you should find info if you can't wait for my post tonight.

Thanks - Jon
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Old 02-06-2001, 06:47 AM   #10
mhj
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I have a question about SC's. Are they 'fixed' to the belt so that SC speed is always proportional to engine speed or is there some type of one-way clutch system that allows the SC to continue to spin even though the engine speed has dropped? (kinda like a bicycle tire - continues to spin even after you stop pedaling)
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Old 02-06-2001, 07:28 AM   #11
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One of the great things about a proper SC setup, is that it's always at the pedal. You feel as if your car is N/A, throttle response is always there, there is no jerk when your accelerating. Its there throughout the powerband. If someone made a decent kit for our car, or if I had the means, a supercharger would serve our cars great. Especially if your into AUTO-X. If you have the means, a kit wouldnt' be that hard to make. Intake sucks in the air, SC forcefeeds it into the throttle body, no rerouting anything.

But the aura for the imports are turbo's. Only a few have SC's.
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Old 02-06-2001, 08:13 AM   #12
edekker
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mhj,

Yes, blowers such as the Eaton and Autorotor do spin proportionally to the engine speed. These blowers incorporate a bypass valve, which unloads the blower (reroutes the output back to the intake) whenever the power is let up.

Ed.
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Old 02-06-2001, 08:51 AM   #13
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I gotta chime in for the N/A camp here. You can get 240 horse in N/A form...or more. Not just with intake and exhaust either, but rather with a header, high flow cat(s), and new cams. 11.5:1 compression might not be a bad idea, either. Fuel enrichment can be had through a few different ways. http://www.jcportsinc.net sells a torque chip II that is better than my current torque chip I. I haven't tried it yet, but it's on my list. The advantage of an N/A car isn't in the total HP output, but rather the shape of the powerband. You're limited to the flow of the engine, not the boost of the turbo. Compare the slopes of each on a dyno chart. A big turbo has a "spike" of boost that comes on all at once. An N/A car has a longer, smoother powerband. That's excellent for throttle response, but you don't get the sheer jolt that a turbo gets. Your tranny won't get the jolt either .

Gary
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Old 02-06-2001, 09:58 AM   #14
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Then how come we can stay N/A and equal the same amount of hp as a turbo for the same price... If only we could get free labor on N/A parts (yeah right) for our cars. Then we'd be set! 'cause labor is the hard part for N/A parts.

I personally want to stay N/A, but don't know if that will happen. I've got plenty of other things to do to my car before I got for some hardcore power increases though.
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Old 02-06-2001, 10:41 AM   #15
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Burning rubber if a turbo has a power "spike" something isn't right. While most have a steep rise in power just after it starts making boost, it should not be like flipping a switch.

Oh and turbo system properly built for the street will NOT have any real Lag. just plant your foot and go.
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Old 02-06-2001, 01:42 PM   #16
HamFist
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I agree that a good street trubo won't have lag. I was referring to a LARGE turbo. Look at the dyno charts at jcsports' website. There's one for a big turbo on there that has a very defined rise to it. The N/A one has a nice, smooth rise. Even with a smaller turbo, it's still only good for a specific RPM range to your displacement. My plan is to just open up the stock engine and see what it does. I mean open it up, not gouge the piss out of it and spin it above 10K . I expect to be able to give a 5psi kit a VERY good run for it's money...and do it for about the cost of a bolt on turbo, too. Part of my goal is more usable power for the same price as a turbo kit. At the last autoX, I was 2 seconds slower than Larry in his turboed and suspensioned RS. So far, I just has intake, exhaust, fuel enrichment, and a rear bar, all on good tires. With a slipping clutch, I still ran dead even with another guy with a turboed imp. That was really only because the guy hadn't had much practice. Drag racing, I'd prolly lose. But, at the autoX, N/A is VERY good, and it'll actually let the tranny live longer. I wanna see if i can make power somewhat comparable to a turbo, and make the tranny live.

Gary
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Old 02-06-2001, 02:27 PM   #17
Jonnathan
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Hmmm, I kinda like the sound of your N/A thinking, but what about all the labour costs ? of installing lots of parts rather than one Turbo/SC installation, do you think you can still do it for about the same price ?
What kind of mods do you think you'd have to do to make an N/A engine reach 230HP+ ?
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Old 02-06-2001, 02:37 PM   #18
Jon Bogert
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Lightbulb

Remember that a 230HP NA Impreza needs most of the same stuff as a 230HP turbo Impreza. For example, both will need:

- Freer flowing exhaust. The NA car must also make sure the exhaust is "tuned" properly.

- Performance clutch.

- Additional fueling. This is more complicated for an NA car, since you can't just peg higher fuel pressure to boost.

The turbo car needs the turbo and exhaust and intake piping, which can be sourced for less that a set of Trey's ported heads, much less a cam, higher quality valve springs, and the engine control that an 230HP NA car requires.

Which one was the budget choice?
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Old 02-06-2001, 02:55 PM   #19
Greg Sharpe
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Damn! I didn't just get corrected by a Supercharging-monk of this holy war, or even a fellow Turbo-monk; I got corrected by God himself! hehe Well my apologies for spreading misinformation, more exactly, generalising all superchargers into one category. I guess I'm dead now, right? Will my life be renewed at a later time?
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Old 02-06-2001, 03:16 PM   #20
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Until there is a "reasonable" SC kit on the market, then this question is moot. (OT: Anybody remember the Jessie Jackson skit on Saturday Night Live?)

Second of all, I really enjoy sitting back and reading about how laggy the turbo setups are for the RS. I've had quite a few people in my RS and never has anyone talked about my car lagging due to spool up. The car has plenty of power off-boost to get the car moving, and then the boost comes on and you're off. Not a violent-torque-steer-lose-traction boost like is evident on some turbo vehicles, but a nice application of power. And this is on my "huge" Garret T03/04.

Steve
http://www.lagging.com/
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Old 02-06-2001, 03:19 PM   #21
HamFist
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One way to save money, if you're that budget minded, is to do stuff in stages. If you buy one part, then put it on, and keep doing that over and over, you'll go overboard on labor! You put food on the mechanic's plate, though . That's what JCS and I are trying to do. I'm not God, nor do I have his checkbook . I'm not cheap, just frugal. They could tell you I know how to shop. But, billet cams don't really have a loophole on cost, do they? Most of the bolt on mods for a turbo are the same for N/A...it's all for better breathing. If you want to consider a budget for it, saying the turbo route is cheaper, then find a cheaper route on a tranny rebuild for me! Sooner or later, everyone turns up the boost just to see what it does. Larry's deceased-and-resurrected tranny is a perfect example. Heck, if my N/A car breaks the tranny, then I'll have a very good case for the buildup, now won't I ?

Gary

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Old 02-06-2001, 04:34 PM   #22
Jonnathan
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I actually spoke to Rick Rimmer this afternoon and asked him a few questions about problems with the impreza S/C kit.
he says they are still working on the kit, its nearly finished. They have simplified a few things, removed the need to drill into the oil pan, tried to make the kit much easier to fit. he says, it will require no extra parts, and they will be ready to start shipping them in a month or so.
So heres hoping for a good kit....
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Old 02-06-2001, 08:26 PM   #23
Rich L
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Yeah...
and let all hope for SOA to hand out free turbos to all RS owners because they feel bad that the newer and better WRX has force induction.

I though Rimmer went bankrupt (again) so why is he still in business?

As far as the issue at hand, I'd go with the turbo setup, God knows I wanted a S/C really bad...
but then the Big Guy told me to trust Rallispec and get the dam turbo.
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Old 02-06-2001, 08:55 PM   #24
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I actually asked SOA about offering the WRX turbo kit to current RS owners, for a price. That way, our warranties wouldn't be voided, and we would get a turbo. They unfortunately said that they do not usually offer upgrades for older model cars, so they most likely will not offer a turbo. I was dissapointed, it would be a great item for their new SOA perfomance part line that they are selling now.
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Old 02-06-2001, 09:19 PM   #25
MattC
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I'm sorry Gary, but I am going to have to disagree with you. Our trannies are not breaking because of turbos, but because of the torque they produce.

As Steve said there is no way my car has a bit of "lag". 5psi can be reached before 2500rpms, and 10psi around 2600rpms. Above 3000rpms it is instantaneous . In fact the tech boost controller is having a devil of a time controlling it. I am having some real issues because the damn turbo spools way too fast Oh, and btw I am also running the "LARGE" T3/T04

If you want to talk throttle response, picture this. It just stopped raining, my car is running a very nice solid 7psi. I ease through first gear, then 3/4 of the way through 2nd gear I let off then floor it. Every time the tires will break traction! Now thats throttle response

Sorry if I come off a bit mean, but I am just sick of people making unsubstantiated claims. Do it, then share your experience


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