The turbos are cool but they just don't look like this!

https://www.s2ki.com/forums/showthread.php?...&threadid=33568

 

Also NOTE: MG RAcing roots style S/C soon revealed!!!

 

Yeah! Vortech are cool! I was looking at their Supercharger for my CRX to install to my future B16 motor. They clam to boost the 160 Hp B16 to 277Hp! Over 100 Hp gain!

 

Can't wait to see what a roots blower will do for an S2000.

 

Can you point out the difference between the Roots type and centrifugal S/C? Is the Roots type those great big honkin' blowers that sit on top of dragster engines?

 

xviper, with your background I'd think you'd know this...

Okay, Forced Induction 101:

Exhaust Driven Supercharger (turbo)(Garrett and others)
Advantages: can spin up separately from engine speed, wasted exhaust energy can be used for more power. No parasitic drag on engine crank, very little loss of HP driving the turbo unit (more efficient). New systems will allow variable pressure release (ie, you can dial in your boost).

Disadvantages: complicated plumbing, high underhood temps, higher backpressure, if you try to reduce backpressure with bigger turbo, you get more lag.

Centrifugal Supercharger (Vortech, Paxton)(Comptech)
Advantages: simple installation, less underhood plumbing, no lag

Disadvantages: linear increase in boost, so it can only produce max boost at one rpm setting. Engine power increases as rpm climbs. Heat production. Parasitic drag on engine crank, it takes HP to make HP.

Positive Displacement (Usually Eaton Roots)(Jackson Racing, Ford Lightning Pickup, Drag Cars)
Advantages: same as centifugal, plus boost pressure remains constant from idle to redline. This gives tons of low end torque as well as substantial HP increase.

Disadvantages: Heat production, parasitic drag is larger than on the Centrifugal units.
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For the S2000 it seems that a turbo would be ideal although most costly. It takes away very little engine HP and gives back big gains. Also, turbos typically give higher gains with less boost since your not driving an impeller off of the crank. Unfortunately it's probably the most costly and hardest to install since there is so much additional plumbing.

The centrifugal supercharger is not a bad choice since it has many of the same aspects of the turbo and is easier to install. If an intercooler is added you basically double the amount of plumbing.

The roots style supercharger is good for low end torque which is lacking in the S but you risk breaking other things when you have more torque off idle. You may see lower Peak HP gains with the roots but higher torque gains at lower RPM.

 

Sorry, I should have been more explicit. Thanks for the explanation just the same. I'm sure this is quite educational for many readers. I was interested in the actual construction of the S/C - cent. vs Roots. One uses an impeller (sort of like a fan). The other ............ ????

 

The centrifugals use a single impeller while the roots typically are a dual rotor design almost like two long gears coming together.

One set of Eaton rotors that I've seen had a spline "twist" to them like a helical gear in your transmission. This probably reduces noise since there is gradual engagement of the lobes.

Not 100% sure if what people call the "screw" type is the same thing when refering to a roots blower. There may be other ways to do positive displacement.

Also, I forgot to mention that Turbos typically spin at the highest speeds, then comes centrifugal superchargers, then the slowest is the roots.

I heard that Vortech is coming out with a dual supercharger design for the Ford SVT Lightning. The truck already has a roots supercharger for great low end torque (450 lbf. stock) and Vortech wants to add a centrifugal for high end power. The problems are getting both systems to work in concert together.

Thanks for the compliments on my teachings. Glad to help.

 

more power equals good

 

Nitpick: the boost does not increase linearly with rpms. It increases at the cube of the increase in rpms (i.e., doubling the rpms and you get 8X the boost). Given a maximum boost value for an engine, this means that you have relatively little boost at low rpms.

Using the Comptech SC as an example: if it had a linear increase, you expect to have 3 psi at 4500rpms (half the rpms, so half the boost). Since it is actually a cube function, you have close to 0 psi, as shown on the dyno charts.

Someone pointed out that you could use a BOV to try to correct for this, but you would blow up your engine if the BOV ever failed. For example, if the S2000 can safely handle 6 psi, you could set up the SC to produce 3 psi at 3000 rpms for better acceleration from a stop. Without a BOV, you would get 81 psi (81 = (9000/3000)^3 * 3psi) at 9000 rpms; you could have the BOV limit the boost to 6 psi and waste the additional charge. Doesn't sound safe to me...

Tanq