Eaton M90 on 2.9?

[disciplerocks]

Yeah they do, but not as bad as most decent sized turbos.

 

[cammeddrz]

Yeah they do, but not as bad as most decent sized turbos.

agreed but it is noticeable. i just want to clarify that on a centrifigul the impeller needs to reach a certain rpm before it will make boost, i.e. "spool-up" that needs to happed whether it is belt driven, or exhaust driven.

positive displacement blowers have bost and air inside them so the boost is relative to belt speed. because they do not need to "spool up"

 

[Hahnsb2]

are you kidding? have you even had one? centrifigul blowers have a lag. i had a procharger on my lt-1 camaro. it came with the car, and it still wasn't worth it. and no it didn't have a waste-gate, but it had a blow-off valve and it had a lag.

I know what you're trying to say, I know how they work. There is no "lag" it spools up and down with the engine no matter what, it's a mechanical link. Yes they have to reach a certain RPM before they build boost and boost is directly proportional to RPM.

 

[cammeddrz]

they have to reach a certain RPM before they build boost and boost is directly proportional to RPM.

on a belt-driven turbo boost is only ever "proportional to rpm" after the boost has been built. and that is even a lie because if in fact the boost was "proportional to rpm" it wouldn't need a blowoff valve

it is misunderstood that the downsides to turboes (i.e. needing to spool, needing a blowoff valve to vent excess boost etc.) is exclusively due to the fact it is driven by exhaust. when it's more attributed to the design of the unit, that is exponentially compounded by the fact it is exhaust driven.

centrifigul blowers are a more expensive, more space consuming, with more parasitic loss alternative to a turbo. with little benefits over turboes. that appeal to the guys with cars like lt1 camaroes where more than half of the engine sits underneath the dashboard (the bottom of the winshield sits just behind the front cylinder) so a P.D. blower is not feasible

look sorry to thread jack

 

[Hahnsb2]

on a belt-driven turbo boost is only ever "proportional to rpm" after the boost has been built.

Which I why I said this

they have to reach a certain RPM before they build boost

and that is even a lie because if in fact the boost was "proportional to rpm" it wouldn't need a blowoff valve

If you are at 5000RPMS and 10PSI, where does that boost go when you snap the throttle shut? It doesn't magically disappear.

They need a BOV because the throttle blades(s) is after the blower. On a PD blower the throttle is before the blower...

 

[The_Dealer]

it can only make as much boost as the pullies will allow, changing pulley size will increase or decrease boost. they make power at lower rpms then a turbo of comparable size could ever think of

 

[Davis]

it can only make as much boost as the pullies will allow, changing pulley size will increase or decrease boost. they make power at lower rpms then a turbo of comparable size could ever think of

While that is true with a Positive Displacement Supercharger it's not the case with belt driven Centrifugal Superchargers, which is what is being discussed here. IMHO, Centrifugal Superchargers give you the worst of both worlds when it comes to the super vs. turbo debate.

 

[AllanD]

M90's aren't all that hard to aquire... Hey I have TWO that I have no actual use for.

I've probably passed up a dozen or more M62's in various junkyard cars.

as for turbochargers?

The beauty of a turbo is that you don't need to worry much about setting up the drive
instead you get to routh both "hot side" and "Cold side" plumbing.


IF the turbo is correctly chosen for the application "lag" is largely a myth.
the need for a "Blow off" is equally myth.


What creates the myth of "lag" is that typically engine's have a torque band and you need to rev to get to that torque, and as a turbo is driven by exhaust flow really only starts working when the flow increases sufficiently to drive it...

So you get the normal increase in torque as the motor comes up and the turbo them "amplifies" the torque...

So you get a much steeper rise in torque and people perceive this as "lag"

I agree on centrifugal superchargers to a degree... but the compressor itself is FAR more efficient than a "roots type" blower.

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[disciplerocks]

Hey Allen, you wouldn't want to send one of them my way would you lol. I wish the junkyards around here had some on them. They are always stripped. And I am looking for a M990 or M62.