Ported Superchargers

**JustenGT8** · 17-12-2008, 08:07 AM

Anyone have any experience with this or know the why's and wherefore's on the benefits?

I have seen quite a few ported M112's for sale with various port styles and a wide range of hp improvement claims.

The stock V port has always looked pretty retrictive to me but from my limited understanding of how the rotors move the air you need to maintain some type of 'chamber' otherwise you wouldn't have any shrouding on the bottom side at all?

So, porting supposedly increases flow potential but at what trade off? boost potential? boost response? efficiency?

**oldcorollas** · 17-12-2008, 03:59 PM

twisted eatons are halfway between a straightlobed roots, and a twinscrew.

actually, they are basically a twinscrew with no internal compression, or... a curved straight lobe.. whichever way you want to look at it.

original eatons had an outlet like this
http://s115271005.onlinehome.us/K24/MP198.jpg
just the V.
you can see the angle of rotors is same as the V.. that means that when new rotor air pocket opens to the V, air rushes back - heat = inefficiency

then you had next stage, where they have "cheater slots"
the cheater slots, or whatever you call them, allow manifold pressurised air to flow into the rotors cavity before it opens at the V, so that there is more pressure equalisation and higher efficiency
(the one on the left here has ben "ported".. ie the V is 1/4" wider and the ports smoothed)

from here http://www.matmoranmotorsports.com/about_car.html

this is an extreme example of porting and.. may not actualyl be good at all

basically, you want to reduce flow disruptors and have smooth ports.
as the rotora mesh together, they "squeeze" the air out, so increasing the actual size fo the V is not that beneficial..
changing the size of the cheater slots will change the rate of presure equalisation, and my own thoughts are that larger cheaters will be needed for higher rpm, to have higher efficiency, but at lower rpm, stock ones are ok... you wan tto reduce the yo-yoing of the air basically, between the cheater slots and the rotora cavity and the V..

inlet porting on the other hand, can be beneficial as the stock bits are often not great
but, you'd wanna be careful about opening the window, as you don7t want it to overlap with the V on the exhaust side...
if anything, i thin kit is better to allow more time for the intake (bigger window) and less time for exhaust (cos it will be squeezed out anyway)

but, take this with grain of salt

there is a lot of misinformation abotu SC porting, as it is a quick buck industry

**oldcorollas** · 17-12-2008, 04:11 PM

re the motion..
straight lobed rotors can have top and bottom totalyl open, with the only proviso that the top and bottom ports have to be at least the distance between rotor tips apart.. so the rotor cavity is not open to both at same time

same goes for the twisted lobes, but in this case, the cavity progressively opens and progressively closes. that means, the cavity gets bigger and smaller, adn the point of sealing (which is all the way along the rotor for straight) moves with the twisted rotors..(moves away from the inlet, so the inlet progressively "sucks")

you need the V, cos when the rotor first passes the V, that cavity has to be blocked at the inlet. (i think the cheater holes actually overlap.... but you can check that on your SC)

porting the exit won't increase flow potential as such, since the rotrs "screw closed" and squeeze all the air out. but you can make the ports more efficient by treating them like.. any air flowing port, and reducing drag as such...

on the intake, the tube running up to the inlet window is the subject of nromal air porting.. smooth, progressive etc.
the actual window, you can only change the end points really... which is kinda like porting with a rotary.. but you don't want to overlap with the V...

mayeb i am makign less sense now

more random pics

**JustenGT8** · 17-12-2008, 04:57 PM

Thanx Stew,
I've been doing some reading as well and seems the main benefit is reduced temps post rotor so the hp gains com,e from the fact you can turn the thing harder (more rpm) but have the same eff as pre-porting.

I won't need to turn any more rpm for my twin charge setup but reduced inlet temps is def a good thing as heat was a significant contributor to my top end power loss with the M90 i suspect.

Buying a ported one means a rebuild has occurred too which should be a good thing.

The SC i'm looking at is at the more extreme end of the porting scale so still look,ing for potential downsides...other than loss of housing integrity.

**oldcorollas** · 17-12-2008, 05:07 PM

as i understood it, the gain from "porting" the exhaust, was more from the cheater holes than the main outlet, cos it is the pressurised air rushing back into the rotor cavity, and then being pushed out again, that creates the heat, so the cheater holes allow air to leak back slower (instead of just dumping back when the rotor clears the V), and then that is what reduces the temp increase..

not really from more "flow", or from the air being able to get out of the rotors better... cos once the rotor clears the V, there is not much stopping the air from coming out, and the edge of the ports aren7t really any kind of restriction... when ya think abotu it (ie, when rotor is halfway from clearing the V to meshing... there is no need for a bigger V, except fot "timing")

there seems to be a LOT of bullshit when it comes to the claims of ported eatons.. ie, making V area bigger may not actualyl change the SC charecteristics at all! (apart from smoothed edges of the port for smoother BACKWARDS flow when the rotors initially clear the V)

i guess the main downside is the cost.. migth pay a couple of grand for porting which doesn't do squat

however the way the slots adn openings are made is a little agricultural from factory (since they go on cheap cars) so you could probabyl hand finish the holes and get 90% of the gains of "professionally ported" ones

**JustenGT8** · 17-12-2008, 05:10 PM

Cost isn't an issue here...it's done, i'm not paying for it and price is bugger all different to non ported. I just want to be sure the porting hasn't reduced some aspect of performance?

**oldcorollas** · 17-12-2008, 05:12 PM

probably not reduced, unless they have gone way too far, and there is overlap on inlet and exhaust...
and as long as they haven't made the reversion flow worse instead of better (some porters seem to think the air only goes out of the cavity.. not in then out again..., so their porting is not good)

any pics? any idea who ported it?