blow through roots charger...why not?
blow through roots charger...why not?
(OP)
I have a 1991 BMW 325i with a 2.7lt "stroker" engine (885 casting cyl head, 292 degree cam, long tube headers, 10.2:1 comp,82mm stroke, lightened stock rods, cleaned up intake and exhaust ports/chambers, balanced rotating assembly).
The engine is currently running Dbilas 45mm ITB's (individual throttle bodies) and i am building a mega squirt EMS for it.
Once the engine has had enough break in time, I would like to add a M-90 gen 5 Eaton supercharger.
the superchrger is from a 2002 (?) Buick Regal and has a built in by pass valve. I am planning on running a max of 12 lbs boost. I am also going to be running an air to water intercooler.
In re reading Corky Bell's supercharger book, I noticed that he states that roots superchargers should be used in a draw through configuration. I how ever would like to use it in a blow through application though. I can not find a reason stated anywhere to explain why he makes this statement. Can anyone give me a reason why this will not work or is less than ideal?
thank you for your help.
The engine is currently running Dbilas 45mm ITB's (individual throttle bodies) and i am building a mega squirt EMS for it.
Once the engine has had enough break in time, I would like to add a M-90 gen 5 Eaton supercharger.
the superchrger is from a 2002 (?) Buick Regal and has a built in by pass valve. I am planning on running a max of 12 lbs boost. I am also going to be running an air to water intercooler.
In re reading Corky Bell's supercharger book, I noticed that he states that roots superchargers should be used in a draw through configuration. I how ever would like to use it in a blow through application though. I can not find a reason stated anywhere to explain why he makes this statement. Can anyone give me a reason why this will not work or is less than ideal?
thank you for your help.





RE: blow through roots charger...why not?
the charger, so the charge comes out a little cooler.
Mike Halloran
Pembroke Pines, FL, USA
RE: blow through roots charger...why not?
The Dbilas have sealed throttle shafts and can handle 2 bar according to the manufacture.
I also have a vacuume activated blow off valve, will that be needed (or a good idea to add) to prevent throttle plate damage? Will it just be redundant as I already have a built in by pass valve on the supercharger. I realize the by pass valve is meant for "crusing" or low vacuume situations, but does it not also preform a similar function?
RE: blow through roots charger...why not?
You need a _big_ blowoff valve, usually a plate secured with springs, between the Roots and the engine, to prevent damaging the Roots when the engine backfires.
Some systems use a bypass valve around the Roots, that allows the engine to draw air even if the Roots stops. It may not make a difference in normal operation. It is _not_ the same thing as a blowoff valve.
Mike Halloran
Pembroke Pines, FL, USA
RE: blow through roots charger...why not?
Do a google search of the site. This has been done to death already, as twincharging I think.
Regards
Pat
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RE: blow through roots charger...why not?
i am familiar with turbo charging, but this my first venture into supercharging, so i just wanted to clairify some points.
thank you again.
RE: blow through roots charger...why not?
RE: blow through roots charger...why not?
Did I make things more complicated for myself with this choice?
RE: blow through roots charger...why not?
A vacuum operated bypass might not act in a fail-safe manner if you have a leak in the hose leading to the bypass actuator.
RE: blow through roots charger...why not?
I am no so concerned with the by-pass being a fail safe as much as it helping with fuel economy at low vacuume or cruise. I am treating the blow off valve as more of the "fail safe" to keep from damaging the ITB's (individual throttle bodies) that I can only get from Germany at great expense and to keep back flow to a minium when the throttles are closed. I assume that it will act in a similar fashion to the way it works with a turbo charged system to reduce lag and back flow also.