Anyone know of any available kits for supercharging (belt driven or otherwise, but not exhaust-driven) a Suby motor?
- posted
18 years ago
Anyone know of any available kits for supercharging (belt driven or otherwise, but not exhaust-driven) a Suby motor?
Someone mentioned this a while ago...
I'm just curious; Why supercharge instead of the turbocharger? I mean I could see it for a dragster. And the Subie has been reliably turbocharged for years with predictable results. Chip '05 FXT
In a word: lag. Still get the intercooler lag of course, but even that can be less than with turbo due to shorter ducting. I don't know why real superchargers don't get more play...
Efficiency. They are a constant drain on the engine, like an enormous A/C compressor. Large ones can consume up to 100 hp, according to an article I read about them back in the muscle car days. Turbochargers don't load the engine (they use the velocity of the exhaust gases to operate, rather than the pressure) so they don't increase the fuel consumption when not being used the way a supercharger does. In addition, they can't boost at low rpms the way a supercharger can so the engine suffers a lot less under a turbo. Superchargers have a nasty reputation for putting holes in pistons if not carefully set up.
Mike
Exhaust back-pressure reduces engine efficiency too. Turbochargers don't load the engine *as much* at low RPMs, which is why they suffer lag.
There's no such thing as a free lunch. I'd rather have the torque on tap whan I ask for it.
The choice is yours. Most people don't want the serious hit on the fuel economy when not using the supercharger, and that is probably the main reason they are more popular at drag strips than on city streets. I know I'd never want that. Add in the high potential for engine destruction and it just isn't foremost in everybody's wish list.
Turbos don't raise back pressure enough to worry about so few people worry about it. The back pressure increase really only occurs while the turbo is spooling up - a second or two with every use.
Have you looked into nitrous? It is an "all or nothing" increase, unlike the continuum of power with a blower, and can't be used too long at a time, but it has a number of other advantages (like inherent detonation resistance) that make it attractive if you want a large, lagless power increase.
Mike
I must admit I'm not a auto techie, but I do remember from the Mad Max movie that the character had a switch that would disconnect the supercharger to save fuel. Is there such a thing? Or was this just done for the movie?
It wasn't to save fuel. It was there to add dramatic amounts of power.
No, just for the movie. Although it would be cool if you could do it.
I imagine the barrier is that the intake on a supercharged engine always goes through the supercharger. Since all the automotive superchargers I've heard about are positive displacement, shutting one down would block the intake. Maybe if there were a bypass with damper doors....
Mike
I can attest to efficiency of a turbo. I had a 1986 Saab 900 turbo. My mileage varied very widely, depending on how hard I drove. Using a light right foot increased my efficiency greatly. When I wanted power, I just pressed down and paid the price for the fuel.
Yes - I drive a 1985 Volvo turbo wagon. I can appreciate Clifford's concern about lag - coming off the line here at 7000 ft I wish I could do the Fred Flintstone thing, but once the turbo gets its mojo working it has plenty of power. Around town it gets about 20 mpg, same as the non-turbo version usually does.
Mike
Aren't most modern superchargers controlled (electronically or from intake vacuum) by a clutch? Which presents its own set of potential problems of course.
My '04 STi had very little to no turbo lag. So the issue is pretty much moot with the newer Subaru's. I notice very little turbo lag with my FXT. But, my older '96 Eagle Talon Turbo was wait, wait, wait,then wheee! The boost would come on like a freight train.
My '04 FXT AT has a lot of turbo lag, the one I test drove was exactly the same, but then at that point the UK was only getting the 2 litre turbo, and I couldn't wait for a new car. now you can get the 2.5 turbo here. Mine is very much a case of "wait, wait, wait, then wheee! The boost comes on like a freight train."
Ian.
Nope, it is there for some superchargers. Basiclly the same type of electric clutch as is used for air conditioning. There is more than one way to supercharge and engine. The roots type used on dragsters is taken from heavy diesel engines that are always on. There were other versions that worked through the carb or has bypass gates. I don't know what is available now but Google does. ;-)
We get the 2.5L here. And there is no turbo lag issue. You would be hard pressed to even know it was turbocharged. Other than it has lots of power to spare. Great sleeper. No one expects that kind of speed out of the Forrester.
Is that a two stage turbo or a light pressure type? I hear either of those have a lot less lag than the older single stage full pressure type (mine).
Mike
My '04 STi (Canadian Ed.) also has no turbo lag, but the turbo itself has a much broader, more gradual power delivery band; i.e. it's capable of supplying boost at much lower RPMs than the normal WRX. At what cost? Endless supplies of gas and large volumes of air. You know our STis get worse gas mileage than a 2001 Corvette, right? =]
There is a guy on the N. Amer. Subaru Impreza Owners' Club with the screenname of reddevil who has supercharged his legacy. Maybe you could shoot him a message with your questions.
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