Compression stroke until the cylinder pressure exceeds equilibrium with the pressure behind the intake valve and exhaust-intake after the pressure in the cylinder drops below equlibrium behind the intake valve.

 

I have been following this thread with interest due to being on the cusp of either having my eaton ported or going with the MP. I am running a 4# lower and stock upper with SCT tune. Only other mods are catback and CAI. I am not looking to go over 450 hp and want to remain "safe" because this is my only transportation. I would like to keep boost at no higher than 16. If I swap the eaton for the MP, what kind of boost level will I be looking at? I'm trying to determine if the MP would be worth it to me for my conservative setup. If I keep boost at or below 16 I should have no valve float issues, but will performance be worth the increase in cost of the MP over porting.

 

SORRY BUT I OWE IT TO THE COMMUNITY TO TELL THE TRUTH!![/QUOTE]Damn straight Rob

 

Ok, let me jump back into this thread with a few comments and replies....

Mark said:

This is very true, and this is something I have not agreed with since day one. I told Charles right off the bat, that I felt it was a bad idea to pitch this blower to people running stock motors. Since it was his product, and that's how he wanted it marketed, I made my sales pitch for them a little different. I told people that if they still had the stock blower, that the MP was a good choice for those looking to upgrade, and that as they did more mods to their truck and eventually built the motor, that the MP could grow with the changes. I still feel this to be true. However, the blower was being promoted as making more power than a ported Eaton, and the proof I was seeing on stock trucks, just didn't back that up.

As time went on, the sales pitch changed to "you need to spin it hard to make power", which then sent people into the land of needing injectors, pumps, and MAFs. It also pushed "stock" trucks into the hp range of needing a built motor. The MP was now going away from it's original promoted market.

tallimeca wrote:

This is now the topic at hand for some. While Charles' valve spring test is interesting, we can't say for sure it's the "problem" until it's tested on a problem truck. Now as mentioned, until now, people really didn't run 20+ psi on stock heads. I will admit, that I have tuned some stock headed KB trucks making about 20 psi, and they have had similar issues as Robs. But again, it's all speculation until it's tried.

Mark again wrote:

This is a much bigger issue than Rob's truck. MANY people have purchased the MP with stock motored trucks. They had ported Eatons, and made good power, averaging in the 415-435 range. Just looking for about 20 more HP, these people bought the MPs. And almost every one of these people were left $1700 poorer and with either the same, or LESS hp than they had before. THIS is the big problem, much more so than Rob's issues. These trucks are not near 20 psi.

This is another issue. While I have had built motor/heads/cams trucks that HAVE gained good power with an MP over the ported Eaton, I have had many more trucks of the same setup NOT gain power. The one truck in particular that Mark is referring to above, actually made more HP with is built truck with his ported Eaton at less boost, than with the MP at more boost. Can't blame these built trucks on valve springs.

 

(split into two posts because of text limit)

Denny wrote:

That's a great post. The problem is that so many people are brainwashed into thinking that every post by someone not using "thier" vendor of choice must have some alterior negative motive to it. Many people just can't see that there are those of us out there just doing good old real world testing and sharing honest, legit info.

Casey02L wrote:

That's dead on. Almost all the MP trucks I've done where the dyno graphs were like Rob's (less power down low, more power up top), actually ran either the same ET or SLOWER with the MP, and it's better hp over 5k.

That's it for now. I wanted to reply to some of these posts because I felt this thread was kind of going off on a wild tanget of speculation and misinformation.

 

READY FOR NITROUS TESTING SIR : o )

 

Rob, Several weeks ago when I first discovered how weak the valve spring were I told you and Sal I would design some tools to make the job of upgrading the valve springs easy and provide them to Sal, well I still plan on doing that. Hopefully that can happen within the next couple of weeks.

Charles

 

has anyone had the cajones to port the MP case yet? just curious to see if there would be any benefit to doing that.

 

1. NO
2. NO
3. NO
4. NO
5. NO
6. NO AGAIN
7. IF IT NEEDED TO BE PORTED ANY FURTHER IT WOULD HAVE BEEN MADE THAT WAY
8. NO
9. NO
10. NO
11. NO
12. LAST TIME NO

 

I-Menace,

I have a theory regarding this and it goes this way. There are two possible times within the 4 cycles where there is a possibility of boost pressure interfering with proper valve action.

1.) At the end of the intake stroke when the valve spring is returning the intake valve to the seat boost pressure imposes a force against the valve head such that it counteracts the spring’s tension and in extreme cases can delay valve closure. If the valve is closing late, then as the piston is coming up on the compression stroke, the incoming charge air could be forced back out the intake valve into the intake manifold before the valve finely closes lowering the engine’s volumetric efficiency causing boost pressure to increase and since the engine did not inhale a full charge of air it will produce less power. The intake valve closing late in this case increases as boost pressure increases and it could be happening even with stock supercharger being overdriven, no one really knows for sure at this point. The effect of this will also be more noticeable the faster the engine is turning as it takes more spring pressure to close the valve at 5,000 rpm then at 2,000 rpm for instance. It should also be noted that Hydrodynamic Finite Element Analysis computer modeling shows the Mag’s volumetric efficiency increases with RPM and peaks around 20,000 rpm or a little above.
2.) During the exhaust cycle cylinder pressure is reduced to zero and in some cases can even become negative. During this cycle boost pressure greater then about 20 psi can open the intake valve and route the incoming air directly to the exhaust port thereby effectively bypassing the engine. This effect will not occur until boost pressure exceeds “valve opening pressure” that has been documented and validated to be 18-20 psi per the extended lab work “Master of Pain” reported on in an earlier post, the testing done by MOP surpasses my own testing at this point, thanks MOP!

Charles

 

Yes you did, and I would love nothing more but to put those springs in, mount that bad boy back on, and see if our prayers are answered

Happy 4th Charles and Everyone
WOO HOO it's like a frigging war ship over here
OR SOMETHING
in my neighborhood right about now

 

Hey Rob, any chance you can share the best ported Eaton dyno graph with us? I would be very interested in the shape of the curves.
Also is it normal for the hp curve to bounce around like your MP graph previously posted? Mine does not do this, but I have not seen enough dyno charts to know if that is normal or can be explained.
Jim

 

I have no idea on why the MP blower did not perform well, but I am calling BS on the spring theory.

I ran 23 pounds of boost(KB)...multiple fricking times, on my built lower...STOCK HEAD/CAM/Spring combo. The truck would do 11.3x's all day long at that boost. I am not much for dyno numbers, but the truck was making over 500 HP with that combo.

23 pounds from a MP would seem to be the same as 23lbs from a KB. My ported Eaton did north of 465 HP at 19lbs of boost.

Maybe it is in the tuning somehow? Say what you want fellers...but JDM has gotten some darned good numbers out of these MP blowers. Maybe instead of chucking rocks over his fricking bow, folks should consult with him on how he does it.


Rocks

 

It takes less horsepower to turn the KB then the MP or eaton at that boost level, + the efficiancy of the screw keeps the discharge temps lower.

 

Makes sense to me............makes less heat and uses a few ponies less....but this still does not back up the weak spring theory.

The extra heat would possibly affect the tune though.

Way back in the day...before I changed my maf. I would run out of voltage at around 19lbs of boost. It makes me wonder if the tuning has to be adjusted for the extra boost from the 19lbs the ported eaton made to the 21lbs the MP made in that test. That adjustment would entail more than just changing the timing or AF...the whole darned fuel curve would have to be adjusted.

Out of curiousity.....what MAF is Rob using and what tuning software is being used here.

Rocks