Porting & Polishing Gen III Blower

no personal experience per say for the m90 here, however, when I ported my LIM I ended up with better air flow and velocity through the engine. The result of this was less boost and more power. To make up for the roughly 1-2 psi drop in boost, I dropped back to my 2.5" pulley to take boost back up and then some(as i had no issues with heat and knock). TO me it makes sense that porting of the LIM, exaust work, and valvetrain work would all do their bit to increase air-flow through the engine and result in more power and less boost.


The resulting lower boost that some people have observed with ported m90 blower housings; I have my own opinions here.
I've spent countless hours looking up info on these eaton blowers and the various opinions of how to (and not to) port them and my opinion falls to the side of those who feel that too aggressive porting in various areas of the blower housing makes it less efficent.(however the lowering in heat buildup leaves the person using it to feel that it increased power) Specific areas that I feel are trouble areas for lowering efficency are the two silencer slits, any cleaning/polishing of the outside circumfrence of the bores where the two rotor lobes turn, and too much deformation to the shape of the V outlet.

my own thoughts are that if boost has gone down from a ported blower, and nothing else on the engine has changed, you have just sacrificed some efficency in exchange for less heat buildup. For some people this is a good thing as it allows through the lowering in heat to run full strength with no KR and the engine preforming better. A smaller pulley could be then be added depending on case, but its really to bring the boost back and the resulting heat that will bring must be taken into effect.

as always, we end up with the same story with these engines where we want to process as much air through it as efficently as possible, but keep temp down.

anyway thats my 2c....

Thanks, Karma. Your cents make sense. I agree that there is a wrong way to port/polish a blower that lowers efficiency, and boost. I want to steer clear of making such a mistake. From the photos on page 1, do you see any that look correct? I'm leaning towards ZZP's approach, but not sure.

the first photo on page one looks the best IMO. It keeps the lines and angles for the V while opening it out a bit more. Maybe could use a little more agressive rounding and smoothing on all edges on the BOTTOM facing side of the housing. I like how the silencer slits are largely unchanged, a slight rounding of the edge can be done there as long as it does not change the original hole size, but making NO changes other than a slight break of the corner from the inside edge where the rotor lobes will pass by. Also a good hard polishing at the inlet end when the air comes from the TB(near where the EGR lets in) will reap the most benifits in regards to heat, as flow testing on these eaton blowers shows that is where the greatest buildup of heat is due to friction.
anyway, thats how I would do it.

If you realy want to increase the efficency and maybe remove a little fricional heat you could look at plugging the scilencer ports themselves, but that is its own bag of worms as to how to properly do it.
here is a link on porting these things with various points of view, also discusses the plugging of scilencer holes..:
http://www.eatoninside.com/showthread.php?t=156

Kemps

Thanks, Codith!

Codith what did u use to fill in the silencing ports

palermocorey90 wrote:

Codith what did u use to fill in the silencing ports

Kemp closes them with a mystery filler....

looks like old fashoned JB, or maybe perma-steel, or magnum steel, or cold-weld or all that good stuff... as long as the sides of the ports are scuffed up to be nice and rough it should hold no problems.

-still best porting of m90 IMO that i've seen ever...

Karma wrote:

looks like old fashoned JB, or maybe perma-steel, or magnum steel, or cold-weld or all that good stuff... as long as the sides of the ports are scuffed up to be nice and rough it should hold no problems.

-still best porting of m90 IMO that i've seen ever...

JB weld NO.... that can come undone and screw junk up!

AA wrote:

RickW wrote:

Decrease resistance = decreased boost / pressure = decreased temps = less KR.

Please substantiate this logic with more info. I don't understand how decreased resistance = decreased boost. Imo, decreased resistance = less friction = less heat = less knock. I've got a stock roots blower moving 90 cu in of air with each revolution. Now, port & polish to make it easier for that air to exit the blower - now I have less heat, but why less boost? Same amount of air entering the manifold, right? I'd think if you make the blower more efficient, you'd have slightly more boost, not less.

I do understand how decreased pressure = decreased temps, but if I wanted decreased boost, I'd just increase SC pulley size. That's not what I'm after here.

Is it common to drop SC pulley size after only a blower port/polish? Anyone with personal experience?

the decreased boost is proof of increased efficiency. You make more power with less boost. You will notice less power "off the line" but have more power on the top end. The engine is also struggling less to produce the power, which is why my IPW's went down.
You could probably drop pulley size .1" with a full porting job.

I only gained maybe 1lb of boost with my IC install, despite my pulley going from 3.25" to a 2.76". With all the extra restriction due to the IC core, thats what I ended up with. But you thing Im not making tons more power with that boost than I was before? IC increases efficiency, just like a ported blower does.

Quote :

the decreased boost is proof of increased efficiency. You make more power with less boost.

Really? What if all the coating peeled off the lobes of my supercharger rotors? Boost would decrease. Is that proof of increased efficiency? What if my air filter were clogged with dirt? Boost would decrease. Is that proof of increased efficiency?

I understand how you can have more HP when you open up the engine (increase flow), which lowers boost. The part that concerns me is where the MAP sensor measures vac/boost. To my knowledge, the MAP sensor measures vacuum inside the manifold, the area between the blower and the LIM. So in theory, dropping pressure after the manifold is good, while dropping it before the manifold is not so good.

So, when you do a breathing mod, like exhaust, cam, or ported heads, all of these things work to increase air flow, evacuating pressure after the manifold. This makes sense because you are moving more air overall, but with less boost. The boost was there, but flow mods after the manifold allow it to escape. You can add more fuel because mass air flow is increased.

But if you decrease boost before the MAP is measured inside the manifold, how is this more efficient? How is that moving more air? How does that result in more power? Imo, lowering boost before the manifold is another way to define "restriction".

Does anyone else agree that a blower that makes more boost is not less efficient than one that makes less? Also, how can a blower that makes less boost flow more air?!!

I'm with AA on this one. If changes are made to the supercharger and nothing else, and boost goes down, you have lost efficiency. Maybe gained a bit cooler running, but efficiency is down period. Since these are positive displacement superchargers, boost is built up in the LIM ONLY. So it you made a change upstream(the SC itself) so the SC could flow more air, and boost goes down, you have lost efficiency. The idea of a good P&P is to improve how the air flows through the SC so there is less heat, but without sacrificing efficiency; otherwise you have wasted your time and might as well just put a bigger pulley on the SC as it would accomplish the same thing: less boost, less heat.

I could have two blowers: perfectly the same. making say 13psi.
lets say on one engine one gives the 13 psi, but on the other it gives 10psi. This is because the second engine flows better from the LIM on, and hence makes better power. A decreased boost number is only proof of increased efficiency of the ENGINE and how it flows from the LIM on(because these are positive displacement SCs)

I agree with AA on this. The goal is to make less heat, increase potential flow of the unit, and increase the target efficiency range of the blower. At WOT with the motor in its power band, there should be equal or more boost. If its equal, we assume its pushing a cooler charge in and using a little less torque to do so resulting in more power for at least two different reasons.

As I see it, if done right, there is no drawback to porting blowers like this. Most of what is done is correcting factory limitations. The second part is, in a sense, re engineering the unit to work to a higher power demand.

The only way I can think of that you might see less boost and I can't imagine it would even be enough of a difference to see is by opening up the intake manifold and blower housing for an I/C without putting the I/C in, effectively increasing the volume of the intake manifold. Theory: The same amount of matter (boost or not) occupying more available space means less pressure.

I basically did that but since the cam happened at the same time, there is no way to make a judgment on its effect on boost.

My head is going to explode!!!
Can anyone just recommend who does the best porting job?
which company should get our business? ZZP? WBS?

Erik, that would be nice to know, but I want to understand the science behind this so I can do it myself - the right way.

WBS VS3


I got it when wbodystore was running a discount

Aside from the unfilled silencing vents, the porting work seems very similar to Kemps'. For the $199 I paid for it on special, I wouldn't even have tried doing it myself.

Thanks Jason. That helps a lot!

AA wrote:

Thanks Jason. That helps a lot!

Kemp does use a CNC machine to bore out the outlet of the blower to get rid of that wall

but he wont tell me what his mystery filler is

Quiksteel....


Pics of my work in progress.





And the inlet from the old SC I ported on the riv.

AA wrote:

Quote :

the decreased boost is proof of increased efficiency. You make more power with less boost.

Really? What if all the coating peeled off the lobes of my supercharger rotors? Boost would decrease. Is that proof of increased efficiency? What if my air filter were clogged with dirt? Boost would decrease. Is that proof of increased efficiency?

I understand how you can have more HP when you open up the engine (increase flow), which lowers boost. The part that concerns me is where the MAP sensor measures vac/boost. To my knowledge, the MAP sensor measures vacuum inside the manifold, the area between the blower and the LIM. So in theory, dropping pressure after the manifold is good, while dropping it before the manifold is not so good.

So, when you do a breathing mod, like exhaust, cam, or ported heads, all of these things work to increase air flow, evacuating pressure after the manifold. This makes sense because you are moving more air overall, but with less boost. The boost was there, but flow mods after the manifold allow it to escape. You can add more fuel because mass air flow is increased.

But if you decrease boost before the MAP is measured inside the manifold, how is this more efficient? How is that moving more air? How does that result in more power? Imo, lowering boost before the manifold is another way to define "restriction".

Does anyone else agree that a blower that makes more boost is not less efficient than one that makes less? Also, how can a blower that makes less boost flow more air?!!

I think you're reading too much into my statement. Or perhaps my statement was too vague. Yes, decreased boost can mean alot of things. I wasn't saying that decreased boost ONLY means increased efficiency. Its just a sign of it. Its also a sign of many other things. Perhaps I should have said decreased boost with increased HP is a sign of efficiency.

Also, when I did my porting, I already have the engine opened up after the MAP.Headers, rockers, etc were already installed.

Also, a "blower that makes less boost but flows more air" is possible, because of the removal of restrictions. Which is what porting is really all about. The smoothing of the porting process reduces turbulence allowing air to flow more easily. Perhaps the reduction of turbulence is what causes the reduced boost. It surely causes reduced knocked. And were not talking about losing half your boost in a porting job. Maybe 2psi.

I still disagree that the ported supercharger's drop in boost means that the engine is processing more air better. Yes you can end up with more power because of less turbulence and less heat buildup and it might seem that the drop in boost is a symptom of better flow.

BUT, I don't believe that the engine is flowing any more air better that would make a difference to drop the boost by a couple of psi for this sole reason: The boost is built up IN THE LIM. Any changes to air flow from the LIM forward CAN drop boost because of better air flow efficiency.

however, if a change is made to the SC ITSELF, IE BEFORE where boost is made, and the boost drops, then you have lost some of the efficiency of how much air the supercharger can move. In a few cases this is good and can be seen as a HP increase from the smoothing of the air-stream and the resulting lower heat. But what is happening is still a trade-off of a bit of boost for lower temps.

Another example would be to take two SC's. One stock, and one ported. Lets say you made a testing manifold where you could bolt each up and measure its PSI and air charge temp with no engine in the equation at all. I will bet any money that the stock one will build a higher PSI, but also higher heat. The ported one will blow a cooler charge with the sacrifice of a few PSI. The ported one will make more horsepower because of a cooler charge and less turbulence, but has lost a bit of "air movement" efficiency.

My point is that this drop in PSI should not be confused with the drop that can be seen when changes are made in areas of the LIM on through to the exhaust manifolds. From the LIM on, changes are made so the engine can process more air and use it faster, hence the resulting HP and slight drop in boost.

From an article Karma posted in another thread,

" In essence, adiabatic losses within the supercharger appear as raised delivery air temperature, thus causing a higher boost pressure, without increasing charge density, and also predisposing the engine to the evils of detonation."

So , in theory lower temps of the ported blower just create a denser charge , so because there is less boost , it doesn't mean there is less air , or power.

TonySmooth89 wrote:

From an article Karma posted in another thread,

" In essence, adiabatic losses within the supercharger appear as raised delivery air temperature, thus causing a higher boost pressure, without increasing charge density, and also predisposing the engine to the evils of detonation."

So , in theory lower temps of the ported blower just create a denser charge , so because there is less boost , it doesn't mean there is less air , or power.

exactly, what I was trying to say in this thread, as far as what is really changing with a supercharger port job. Although all aside, the end result is still more HP.

I think the quote Anthony posted actually seems to defend dreww's point. I still don't understand the "how" & "why" behind it, but it might explain how a port & polish could lower boost and still move the same (or more) amount of air.