are you sure it's not a compressor? if it isn't a compressor, why install a boost gauge to monitor pressure? if it isn't a compressor, why does automotive.eaton.com say this: A supercharger is a positive displacement pump. Its purpose is to increase air pressure and density in the intake manifold. ? that sure sounds like a compressor to me. ALL positive displacement pumps are compressors. i repeat, ALL positive displacement pumps are compressors.

i work for a company that makes dynamic / rotary pumps for industrial use. these pumps are very closely related to turbochargers. we offer no positive displacement pumps in our line-up. all of our products are flow oriented, as opposed to pressure oriented with a positive displacement pump. if anyone here should know the difference between the two, it's me. (and i don't throw this out there to sound egotistical, either)

 

Having experience with both small and large superchargers and turbo's on mazda and honda engines I can speak from the drivers seat.

I'm not going to quote either of you, but I'm going to tell you both that Jesse is correct on almost all of his counter-points.

On my 97 SOHC 1.6 Civic I put on the JRSC supercharger kit, this is a roots type blower (twin-screw). This incorporated the bypass valve as well. At idle the boost gauge reads normal 18-20 vac. The moment I step on the pedal it will hit 0vac if I accelerate and if I mash it from Idle it hits 7-8psi instantly and holds it to near redline. Seeing as the engine is moving faster in RPM while I'm accelerating the boost remains constant. Which throws the RPM vs Boost rising out the window. Although only adding 30-40hp it added much needed torque in useable areas. This is not a kit for people who want big power, just a more driveable car.

On my protege I ran a small VJ20 turbo... at idle I'd have regular 20vac.... hit the gas and you get 0vac. Wait till 2500 and you have some boost (8psi) 3500 and its fully spooled (16psi) and 5500 its down to 10 psi and the flow is gone. Lots more power than the twin-screw but not linear. Not really useable for much.

On Adams escort we ran the larger VJ-23.. same at idle... but boost comes on around 3500 and is fully spooled by 6000. In this case it requires more exhaust flow to reach the efficiency level of the turbo. Once that is reached it holds it till redline. The larger turbo had a more linear torque curve which was useable for high rpm activity.

On a friends miata he installed a twin screw autorotor, limited to 11psi. Off-idle boost was instant and the car had a flat 200lb-ft torque curve from 1500-6500 and slowly died off at 7500. Not to mention the non-stop HP increase up to 7500 for 251whp. This was a much larger SC compared to the wimpy JRSC one on the civic.

The B16 vortech kit using the s-trim centrifugal blower is run by a long shaft turning at X rpm from the engine and pulleys. This kit has the same idle qualities that the JRSC kit had and when gassed it acts like a turbo in spoolup. Not taking as long as a turbo but limited in top end due to frictional loss. Using such a large supercharger for this motor is a good idea because of the redline and theoretical supercharger efficiency. Being able to add 100+hp to a civic is a good thing, if you want to drag race. But being able to use the torque is where its at.

I've found that optimum torque on a FWD car should start to peak around 5000-6000rpm. This keeps your tires from spinning off of launches and keeps you pulling hard to redline. For road racing this is where you want your power, for auto-x a smaller SC or turbo would work out better keeping your torque around 3500-4500rpm.

Most kits nowadays are for show and not performance. When picking your setup always follow the newbie guides: What do I want from the car? What do I have to spend? What do I expect? You don't need to wave your ***** in the air like jedi warriors to know what works best or how X is greater than Y. Pick your applications and apply them. It's all in the tuning after that.

 

well, when you put it THAT way....

 

Ok, I, as my colleague Braden, am not gonna take all day quoting this to death and breaking it down. Basically, an eaton blower is a device designed to move air from point a to point b mechanically and faster than said air normally could migrate between these points. On most sizable eaton blowers boost is produced because they move the air faster than its evacuated from the manifold. They are not a true compressor, its a byproduct of the way they work, not the intent of the design. Personally I think they're virtually junk aside from their packaging advantage and they're predictible, they make the motor act like its a bigger motor, without any wierd power spiking.

As far as turbo vs sc for full time steady power, it can be done, but its rather a waste of the turbo's potential <see Audi/VW 1.8t for best example to date>. The inherent and intentional down-tuning of the turbo's response and use of electronic wastegate control is aparent when the car is chipped as you can get alot of power by sacrificing the perfect torque curve.

At any rate, if you want a mundane car with a power boost s/cs are the way to go or complex turbocharging systems that undershoot the peak power ability of the turbo. If you want a car to make a frenzied dash for max power, get a turbo, unless your all out drag racing and money means nothing...

 

Turbo systems can be made to have full boost at low RPM, just like positive displacement blowers [Braden mentioned a D16 JRSC unit...]. Just put a T25 on a KLZE, and you'll have 8psi by 2000RPM, no doubt [T3 60 trim w/.48 turbine AR spools by 2500 already...]. Granted, you'll be pumping heat by 4000RPM, but that's no different from an Eaton blower [freakin heat pumps :rolleyes]. With the continued development of VTN and BB CHRA's, supercharger's sole claim to superiority [less lag] will be all but eliminated. But as braden has already mentioned, instant boost sounds good and all, but do you really want 200ft/lbs of torque at 1500RPM when you don't have enough traction? Let it get rolling a bit, then have your power come on around 5k, when you won't waste it all in a smouldering puddle of tire [cause we don't have LSD's ]. Hence the reason I believe a T04E 60 trim with a .69 AR O or P trim turbine would be perfect for a KLZE; won't reach full boost [~7psi on stock injectors] till 4500 or so, and 2.5L of high compression fun is plenty of low end/off boost power while I wait for the deluge of boosted power

 

Well, I hate to say this, but 200 lb/ft of torque at 1500 RPM works for me. It all comes down to launching technique. Instead of dropping the clutch and just nailing it, modulate the throttle a bit. If you get a lot of wheelspin, back out of it until you get traction! That way you learn to get the maximum acceleration with the traction available. We may not have LSD's (although we can get them) or traction control. Learn to drive the car to the best of your (and it's) ability and have some fun!

Damn kids...when I was your age we didn't HAVE traction control or fancy electronic gizmos to help US drive.... heh, heh, heh!

 

My factory 93 rx7 did the samething. 18 vac, and 0vac as soon as you touch the throttle and 10psi of boost right away. And a good aftermarket turbocharged car can do the same. Just look at the number of cars that use or have used turbochargers from the factory; Porsche, Ferrari, Rolls Royce, Bently, Lotus, Nissan, Toyota, Mitsubishi, and Audi. Unless you bow to pontiac, ford, or buick (they all use roots chargers). Do you think that a porsche twin turbo is any less drivable then a pontiac?

Look I'm not trying to attack anyone or start any wars, but I just see a lot of information that is not accurate. Maybe I should just start another topic instead of hijacking keiths question about supercharger kits.

T.

 

Big Mike is dead right.

All this talk of compressors and pumps is making me think of hydraulics and the fundamental thing most people get wrong with that and blowers.

No pump (including Roots-type superchargers) generates pressure. It generates volumetric flow. Piston, vane, screw...they all just pull fluid (hydraulic, air) in and push it out the other side. Now if something were in the way of that fluid (hydraulic ram, engine manifold) then the incompressible (hyd) or compressible fluid (air) would generate a pressure on the walls of its enclosure.

It is hard for someone (including myself) to remember that notion, a pump/blower generates flow and that flow is converted into pressure by being restricted.

What the hell, I am just repeating other people's words in a different form. Go blow and be merry!

 

When did Ferrari start making turbo's?

 

the F40 had two

 

Not turbo's, turbocharged cars. The Ferrari F40 was a twin turbo 2.9L V8 475hp/424trq.