Some of us went seriously off topic in a thread about headwork, and starting discussing ported SCs, of which there is almost no data posted, and lots of mis-understandings of what happens in one anyway. So I wrote my second PhD thesis on it.... Here it is for all your reading pleasure, in a thread that's about ported and polished SCs....

I though the sound of ported SCs was real good, and I bought a take off from e-bay (05 with less than 50 miles, for $310 delivered to my door). I sent it off to M7, because I like those guys, even though I'd found Stegmeier (sp?) who does the porting, but I wanted to promote the Mini tuning community. It's still sitting in my garage, ready for action.

So, since I have an 02, the 05 P&P SC won't be a fair comparison, as the 02 doesn't have the same (any?) coating on the rotors....

Also, I bought a used AGS from another NAM member, and didn't like some of the flow featurs, and did something about it. I started a thread called something like "Improving the AGS, one mans journey" about filling in the sources of turbulence (a lot like the gen 2 AGS, just earlier). It too is sitting in my garage, waiting for time. Also note, that while the improved flow path potential from eliminating the turbulence is pretty obvious, my degree does give me a pretty good handle on how much flow improvement potential was there (that's good for about $5 worth of my PhD ). So when I do the work, I'll do them both at the same time. Any results will be conveluted, and hard to ascribe to any one source.

Since then, I've done what I should have done first. Read up on the subject. Now here's a primer on the roots blower.....

1) It's a posative displacement air PUMP, not a compressor. This means that for each revolution, it moves a certain volume of air, without compressing it.

2) So where does the boost come from? It comes from less air being injested by the motor through the intake valves. This means that with each revolution, the pump is putting more air into the intake than the motor can swallow, and this difference "pumps up" and becomes the boost.

3) So why doesn't boost keep climing to the sky? After all, each rotation adds more air than the motor can swallow.... There are several answers to this.
3.1) some leakes back because the clearences aren't 0. There are a few thousanths of an inch clearence, and some intake charge squeeks by.
3.2) there is some volume between the lobes of the rotors that gets pumpted backwards, and this is just due to the shape of the rotors. It's a few % of the pumped volume. And note that this volume is filled with boosted intake charge, so the leakage is about twice what you would expect from just looking at the volume.
3.3) as the boost climbs, more molecules can be digested by the motor (there's a larger pressure gradient between the intake and the cylinder, this is why blowers are used), so as the boost climbes, there is a boost level at which the motor can swallow all the air pumped by the blower.

In reality, all three of these contribute to the steady state, the boost level, leakage due to rotor case clearence, and the reversion of the pumping back to the intake of the rotor/rotor gap.

So now let's think about what porting a SC can do, the exit first....

When the pumped volume opens to the intake, which is at a higher pressure (the boost), some air flows BACK INTO the SC, and then this is swept out into the intake. The flow is very complicated here, but no amount of porting on the back end will change the amount of air is injested by the SC. So why do it? The answer is reduction of turbulence. Think of this as reducing the air friction, and the main effect will be to reduce heating of the air. Remember, the SC is spinning at 15k RPM at redline, so the air motion is pretty violent. To first order, this won't do anything to create power, but it will lower intake charge temp (and with it pressure) which will help prevent detonation. Indirectly, the lower pressures will effect all three things that limit total boost. The hope is that you get less decrease in the cylinder filling than the leakage between the rotor and the case, and the rotor to rotor gap.

Now let's look at the intake... Improving flow here does have the potential to get more air into the SC. This can create more power. When should you expect it to actually contribute? When the path into the SC is a significant limit to flow. An example of this is the testing on the TBs I did with the stock intake path in place. No difference between stock, 60mm and 62mm. That's not because an enlarged TB doesn't help, but it wouldn't do crap with the other bottlenecks on the car. So with a stock intake path, I don't really expect improved flow into the SC either, so I don't expect much at all from the SC directly with the stock air path in place. But to be fair, I haven't mapped all the pressure drops in the intake path, so that's just a guess. A good one, but still just a guess.

So what about indirect power adders? Well, if the charge temp is lower (even at identical molecular density) you can run more advance on the ignition and get more power that way. Or more realistically, you won't have the knock sensor back off the timing on hot days. Our Mini's IC doesn't get the air flow it deserves (only running about 70% thermal efficiency) and I don't know how may dyno graphs that have been posted that have the dreaded kink around 6000 RPMs as the ignition retard kicks in. Truth be told, I've had some ping on some of my MTH maps in hot weather, and none in the cold. I'd anticipate that I can run pingless (or knock sensor retard less) to hotter ambient temps, or at lower speeds (redline in first, as opposed to third).

So this could be a situation where no peak power were added at all by the mod, but it still allows for more useable power in more situations, not at all a bad thing. Is it worth a kilo buck? depends on your income, inclination to test, and ambient weather...

Two other things to think about.
A)Water injection. Do it in the atmospheric side of the SC. Why? The water will reduce the rotor case gap, and reduce leakage. This will keep more of the pumped air on the high pressure side (but you better make sure it doesn't leak, otherwise you can hydrolock the SC, not pretty!).
B) Thermal coatings on the IC. These do absoultely nothing to add more air into the cylender, but will increase thermal effeicincy of the IC (stock about 5%), which will help with detonation, and timing retard.

Sorry if this is boring, or stuff you already know. But I've found that understanding the principles of what the system is supposed to do can sure help with knowing what to expect, and where it fits into the whole system operation.

So, what about cars that put one on and don't see benefit. The only one I'm aware of is the guys up north that saw a bit off a loss of HP in a highly modded car. This was (if I remember correctly) a car where a ported SC was swapped with the one on the car, not the same one being ported and put back on. Maybe the tolerences of the new one were a hair sloppier than the one that started on the car... Don't know. Maybe the porting added some flow steps (like from the intake runner into the SC, the M7 one realy opens that up) that weren't obvious, and were counter productive. If the intake valves are the predominant bottle neck, maybe there just wasn't too much SC improvements can do for that car. Honestly, I have no clue, and to my knowledge, no one took the car apart to test the flow of each part separatly, or to compare the clearence of the original SC to the one that was put onto it, or looked at the match between each part in the system.

In the trade, we have an experimental fact that has not yet been explained. Nor will a single test on another car with different build give a defenitive answer.

Now that I know more about SC operation than I did before I bought and got the SC ported and polished, would I still have done it? I don't know. I get a bump just going from the 02 sc to the 05 sc, so there's some drive there for the change, even without the port/polish. In hind sight, I think I'd do the M7 scoop (more air for the IC),, the thermal dispersant on the IC (more thermal efficiency) befor I did a SC port and polish, and have saved $ at the same time. I'm still on the fence about the larger IC. I have a first gen Alta, but I'm not happy at all about the end-cap design, and am on the fence about using it. (See TonyB's thread about thesting the GRS unit against the stock with and without the M7 scoop). I'll get that coated as well, and do some G-Techs to see what there is to be had. But I have the P&P SC now, so what the heck, when I get off my as* to put it and the modified AGS on, I'll let everyone know what I find.

Matt

ps, if anyone has any data on a Roots on a Mini, please post away!

 

Even a second time, this stuff is still sweet ! One word of encouragement: Take a before and an after vid of how your sc sounds, ported and stock... you'll see what I mean post-swap . I can't comment on the value of my M7 ported SC, because it went on with the rest of my Cosworth kit, BUT I love the car and the SC. And, the SC sounds and behaves quite a bit different than my stock piece did. Compared to other stock blowers running ~18% reduction like mine does, the SC actually sounds and spools much cleaner. It's friggin great, and everyone always asks what's happened. I say it's magic . Can't wait to hear your appraisal!

 

Matt, as I shared in that other thread that went OT...

With re to:

"Two other things to think about.
A)Water injection. Do it in the atmospheric side of the SC. Why? The water will reduce the rotor case gap, and reduce leakage. This will keep more of the pumped air on the high pressure side (but you better make sure it doesn't leak, otherwise you can hydrolock the SC, not pretty!)."

The guy who was about to do my UNIChip dyno tune (had to reschedule) really wanted to try an Aquamist... just prior to the SC. He really felt that our little guy could really benefit from this approach. Experimentation on the IC inlet side yielded virtually nothing, but on the IC outlet was a bit more... so maybe big gains can be had with injection on the atmospheric side... I however had/have the hydrolock scenario in my mind, and sort of balked on the idea, at least for me as the guinea pig .

 

Endyn speaks about adjusting exit port shape to optimize the 120deg lobe timing. I take that to mean he is reducing the back-pumping...what do tyou think that is about?

I also tried water Aquamist injection, atmospheric and pre TB, no effect on the dyno. My reasoning about tightening the lobe gaps was the same. Afterwards, my thinking is you need to hit the hot air post SC with the water for the most benefit.

I probably had the first modded SC; it came from Endyn and went on a month or two before his head. It howls, mostly because he closes the beeder ports. (I see the bleeders as taking the sharp edge off the sound pulse, at the expense of pumping efficiency?).

after all the work was done to my rig, (head, valves, p&p SC, header(coated), Pro-mini cam, exhaust, full flow cat, 62mm TB, intake, 440 inkectors, 19%, One -click, Apexi dyno tune), I don't think I've gotten any more hp (213) or torque than similarly modded cars w/o the P&P SC.

When I get the time, I'm going to put the stock SC back in and analyse the Endyn unit. I have been getting unusually high IAT on the last dyno runs and I suspect the SC is producing too much heat.

as an addenda to 3.2: at some point, the already compressed charge post SC will contain enough pressure to overcome the incoming air and that will determine equilibrium. this is easier to understand kinetically, since the main relevant property of the incoming air is velocity. Comparing incoming velocity to chamber pressure is not so intuitive.

a final thought: Endyn closes the bleeder ports and shapes the output port to match the area created by the lips o'the lobes and then streamlines them. M7 adds a rectangular extension to the shape. When asked about the M7 mod, Larry felt it could never work. Right or wrong, what theory is driving these approaches? my guess is M7 is going for the most exit port area they can get, at the expense of lobe lip matching but Endyn feels the 120deg timing shoul define the shape. Comments?

 

Here's a little blurp from a Motoringfile I found where Eaton answers some questions about the differences in the 02-04 vs. 05. After taking in all the expense associated with porting and polishing, it seems the only guaranteed gains would be "increased efficiency" and some lower temps, which from what jlm is experiencing may indicate that's not the case. Maybe for the lower temps you need port and polish and the rotors coated as well. Gearge at Mini Madness had an Endyne job that had a coating and he reported lower IAT's. But in all of this, Cosmic opted for simply switching to an 05.

Anyway, here is the burp:

With the new 2005 MINI Cooper S comes a new supercharger. Since that announcement a great number of MINI owners have been wondering what that will mean in terms of real world driving as well as long term ownership. So instead of trying ask MINI about these questions we thought it would be better to go to the source and contact Eaton directly. Bob Walling, Customer Manager of the Supercharger Business Development in Europe for Eaton, was kind enough to talk with us about these changes to the new supercharger. Mr. Walling has specifically been responsible for the liaison between the Eaton and Customer engineering teams developing the updated Mini Cooper S engine. So if there are answers to be had this is the man to get them from! Q: It's my understanding that it will include a newly redesigned Eaton supercharger. How does this new unit alter power in the engine?
A:The Supercharger fitted to the revised Cooper S engine is the 5th Generation Eaton Roots Type Supercharger which utilises a unique abraidable rotor coating developed by Eaton and used currently in Superchargers supplied to Mercedes and Jaguar.

The coating allows the unit to be built with lower internal clearances which results in higher efficiency. This can be translated into: Lower power consumption for the same airflow or Increased air flow for the same power consumed. It also enables the roots blower to operate efficiently at higher pressure ratio's.
In the revised Cooper S engine it is used to deliver a higher air mass flow rate which allows a revised fueling regime to modify the engine power curve primarily to offer improved drivability.
Q: Does the coating effect the life of the supercharger in any way?
A:The coating does not affect the units durability in any way having been proved in production by both Mercedes and Jaguar since 2002.
Q: Is the new unit the same one on the MINI Cooper S JCW kit?
A:The unit supplied to John Cooper Works continues to be different to the unit fitted in production and the John Cooper Works package will continue to offer your readers enhanced performance without detriment to the engine durability.
If you have any further questions please do not hesitate to contact me.
We'd like to thanks Mr. Walling for taking the time to answer these questions directly.

Written By: MF Staff

 

Q: Is the new unit the same one on the MINI Cooper S JCW kit?
A:The unit supplied to John Cooper Works continues to be different to the unit fitted in production and the John Cooper Works package will continue to offer your readers enhanced performance without detriment to the engine durability.

First off, I apologize for my role in taking the other thread OT

Second, what is this about?.... I thought the only diff in the JCW was the pulley,......anyone know?

Third, Thanks to the DR. for supplying so much info...... in the words of Will Smith, "now that's what I am talking about." I am very interested in how this turns out.......thanks again.......

 

Spider, I think the general consensus is that the pulley is indeed the only difference between the two, and the rest of their statement is just marketingspeak. If you read the statement closely, there's nothing there to contradict the 'pulley only' idea.

 

Peace SpiderX, I think the only difference alluded to here is the pulley.

By the way, perhaps Dr. O can be the before and after tester here, since he has the ported and polished supercharger sitting around. The only variable in this case would be that it's an '05.
I can say that moving from the '03 to '05 was a noticable change of almost 2 pounds of boost, but the variable in this case is that we changed from 15% to a 16% pulley at the same time.
Given all these factors, this Dr. already made the decision, there are other things that can be done to enhance the vehicle for the same price that may make it better overall than this for the money. Like, I have 3 extra superchargers as a result of all this supercharger modding hype, and would really like a BBK after my experience riding in SpiderX's car. That in my opinion would be well worth it. SpiderX, if you want a noticable bang for the buck, go and find yourself an 05 transmission.

 

Seriously, think twice before getting a bbk unless you're tracking hard and often. A completely sweet and moderate-duty option is to replace the rotors, pads, lines, fluid, and perhaps pad mounts on your existing brakes [all for a third the price of a bbk!]. You'll get much better feel and better performance. The BBKs are only useful when _repeatedly_ stopping from above 60-80.... testing here and elsewhere has shown no benefit over stock on single passes. Sorry, I won't take this any further off topic... look around for posts which address what I'm referring to.

 

Peace as well, After I recover from Xmas and count my change I may take one of the 05s off your hands.....we should probably PM.

 

Thanks.

 

No problem, man! Saves some money for go fast parts and new tires . I still can't wait to see your car in action !

edit: I spoke with Spider, and I have to qualify my statement: if you're canyon carving or driving through the mountains, you can absolutely benefit from a bbk because of the repeated stops, which I was trying to suggest but didn't properly say... Around here, we don't have mountains to go crazy on, so I usually associate repeated stopping with track ventures. I completely forgot about you lucky mountain guys! Anyways, to me, if you're just driving aggressively around town, not carving the twisties, it probably won't do you good. Hope that makes my impressions a bit more transparent.

 

I don't want to go OT here so I sent "Ing" a PM....... re BBKs and my experience with power slots/2500s/SS lines etc.

 

It's an amazing thrill.

Back to superchargers. I can say this. With the 03, after installing the worked head with larger exhaust valves, the boost decreased about 1.5 points. It appears allowing the motor to breathe better decreased boost. After the '05, it gained something over 2 pounds of boost. I rarely watch the boost gauge when my foot is in it. But let's say 2 to 3 pounds, so it appears that the 05 coating does increase efficiency. The other variable here is we added ported, polished and coated runners from pilo. They are coated with a black teflon on the inside and kool krome on the outside. And the car is running water to air intercooler. It would have been nice to have monitered IAT's before and after. But if nothing else it looks really nice.

 

[quote=Cosmic Purple]It's an amazing thrill.

I can vouch for that......

back OT.........I wish someone could quantify the diff between the 05 and 03 SC in performance.

 

That's a coating that can wear away under use. So you coat the rotors with this stuff, put it together, and let it wear to the tightest fit possible givent the bearing and the like that mount the rotors.

The 120 degree fit for the exit port is interesting. If there's no overlap between open and closed, that would result in, um, I'm not sure what, more efficent scavenging of the gasses out of the SC? In thinking about the bleeder port, it will allow boosted air into the SC, so that when it hits the big opening, there's less of a pressure delta, and you should get less noise, but you may get a bit more heating as the air has to slam around more for all this stuff to happen.

But here we're leaving pretty simple known theory into the land of pure speculation....

But it is good to see some honest exchange of information without the usual flame wars starting up.... Congrats to all involved!

Matt

 

But, I've often wondered.... noise is a form of waste energy, no? I can say from experience that my M7 blower is actually quieter/more refined sounding than the stock blowers that I hear. It sounds like less turbulence. I always thought that turbulence was bad, because it creates heat. I'll try to get a vid of the sound of my blower to show and tell... I'll tell you now, though, that I only have a nikon coolpix 5700 digicam with mic... I'll do that today.

 

The 05-model rotor coating is harder and coarser than the previous slippery coating. Closer tolerances are built in so when the lobes experience centrifugal growth the rougher lobes will wear-in more exacting mating profiles within the case. The term “abraidable” refers to its ability to remove material rather than its forgiving properties. Remember the lobes push the air around the case; any air left behind is a loss of efficiency. The early model lobe coating sacrifices the lobe surface to a greater extent for the wear-in process and has greater anti-friction properties to reduce the resulting frictional heat. The latest coating may be harder but its bond to the lobes is just as prone to failure as the early models offering no advantage there.

Among many of the modifications done to the SC, ENDYN coats the case interior with an anti-friction material. This material addition reduces tolerances and serves to cut down on frictional heat. An add-on service is a lobe coating with a very high temperature resistant, highly slippery, and more durable lobe-bonding product.

 

When George at Mini Madness was experimenting with the supercharger, he said the Endyne job when it came back with the coat was definitely more difficult to turn the rotors by hand than the non coated sc. So, perhaps the increased efficiency does come from the coating and not the p & p job. I don't know. Ingsoc and others definitely appreciate their ported sc.
After the Car and Driver challenge, they put the sc on another car which they were able to keep and monitor for any sc benefits with the sc as the only variable in previous dynos. I don't think it made any power. He did say it ran cooler, but i noticed Mini Madness doesn't offer a porting service, so...we can only speculate from there without George chiming in with his observations.

 

Yeah, I got the same impression. I get sad when people go quiet... It's a bit disappointing.

 

Question re: this machining process...

What happens with the coating? How much breaks off, and how large are the particles? What of the material removed from the void spaces in which the rotors turn?

I seem to recall the coating was supposed to be ceramic/oxide or something... Sounds a lot like coarse grit sandpaper. Why is it that I get the impression we are curing one problem, but possibly creating another?

 

into the motor? There are lots of coatings out there. Also, have you been hearing about premature engine failure in SC Jags and Mercedes? I haven't....

There's a lot going on in materials science....

Matt

 

Damn it,......all this talk has me looking at my bank account to see how much more I can do.........:impatient I'm a Mini mod junkie who needs a fix and you guys are not helping please keep it up....it helps me feel normal

seriously, I am getting some inspiration to do some more additions. Some one asked me my goals....... to smile a lot...... i really enjoy my car and subtle improvements are apppreciated........ thanks to all for being my "enablers"

 

what happened to the guy that was adapting the M62? that seemed like the way to go, albeit a pia.

 

every now and then the M62 solution comes up but no one seems to follow through........what wouldbe the chaepest way to source an M62 to start the "mod"