Dr Wolfgang

I was wondering about the intake flow figures vs the stock 928S4 cylinder flow figures.
It appears that the flow capabilities of the stock 928 head will far exceed the flow capabilities of the Eaton Blower/Huntley Intake. Flow characteristics strongly resemble the early Briggs & Stratton 90 degree intake. See below the comparison photos of the Huntley intake and the early B&S Intake:






In reference to Eaton's Webpage, the maximum CFM for their largest supercharger with non restricted airflow is 700CFM. See below:


I would estimate the Eaton/Briggs & Stratton/Huntley combination will run out of boost at 4000 RPM. Well before the superior Porsche 928S4 intake ports start sucking air through the Eaton-Huntley blower attempt...choking the high rpm capabilities of the STOCK 928S4 motor. Why didn't Dr.Porsche think of this?

This setup closely resembles the performance of a 1969 Oldsmobile Delta 88 (455 2-barrel version) with 500ft-lbs of torque at 1850 RPM. Great for pulling out stumps.

This setup would be almost as effective as using a Stroker Crank, again, great for stump pulling. Notice in the link below, the torque drops past the 3k rpm range and appears to barely make stock torque as it finishes the run.

Don't get me started with the $7,500 for a stroker kit, parts only?

Help me here guys, what about the cow farmer from wisconsin who took a supposedly stock 928S4, bolted on a vortec supercharger with basically off the shelf components and spanked the big boys (chest pounders) at their dyno game, see below:

of course their response was "He must be using NOS". I wonder if he was using a special mixture of bovine produced NOS?

Impressive results to say the least.

Taking a lesson from Dr.Porsche, every high hp Porsche ever produced had pressure in the intake in the proper form.

Z

Hello Dr Wolfgang. Good to have you here.
You guys run out of stuff to do up there, since you've found time to post? <img border="0" title="" alt="[Wink]" src="wink.gif" />

You make some of the same general points that I've made to a few people privately. Should be interesting to see how some of the various projects currently in the works turn out when completed.

GoRideSno

Dear Dr. Wolfgang or whoever you are.
Somehow I suspect you are you are a cyclist from Wisconsin.

Anyway your research on the Eaton is incorrect. The <a href="http://www.magnusonproducts.com/mp112_4th_generation.htm" target="_blank">MP112</a> flows well over 800CFM at 14000 blower RPM pushing 5 PSI of boost. And it flows over 800CFM at 10psi as well. Your link is in reference to the old 3rd generation blowers.
I have an S4 intake sitting here and I see no less than 10 (yes count them 10) 90 degree bends in the intake. Each intake runner dead ends into the plenums and the flappy crossover intersects the inlets from the split throttle body at 90 degrees. So, the Huntley will have 2 less 90 degree bends right?

Even if the S4 motor could suck up all of the 800 plus CFM that the MP112 puts out it could get a few more CF from in front of the blower when the built in vaccum accuated blow by valve opens. Plenty of power would have been made down low where our over geared cars need it. And by the way this kit will only cost twice what an after market set of 3.? gearing for our cars costs.

What is the point of being so cricital of something you clearly know so little about?

What is your motive? What do you have to gain? What do we as 928 owners have to gain other than realize your ignorance?

I am not here to defend Huntley's design. I just don't like to see a blatant display of ignorance that may influence other's decisions. This type of ignorance holds us all down.

Andy K

BrianG

Doc W:
Shouldn't it be about 5 liters /2 revolutions per intake cycle X RPM for normal aspiration ??

Ford's 5 l. was their 302 ci. .... so the cube root of 300 = .17361 Ft3

0.17361 / 2 = 0.08681 Ft3 / power cycle

0.08681 X 6300 = 546.875 CFM @ 6300 RPM <img border="0" alt="[blabla]" title="" src="graemlins/a_smil17.gif" />

So, what's wrong with the attempt to utilize an extra 150 CFM even if 700 CFM is all it does? <img border="0" alt="[burnout]" title="" src="graemlins/burnout.gif" />

Your facts seem OK, but your reasoning is absent.

Now, the $$$ for results equasion is possibly quite another matter, and I'm with you on the STROKER deal from that perspective. The $5k deal for a huffer seems a tad steep too, if you look at the same project taylored to the ubiquitous Camaro. <img border="0" alt="[crying]" title="" src="graemlins/crying.gif" />

slate blue

The design I would like to see implemented is the IHI Mercedes AMG screw supercharger design, now that is terrific, if I'm right it also has a intercooler, sorry for the loose terminology.

<img border="0" alt="[cherrsagai]" title="" src="graemlins/drink.gif" />

Jim bailey - 928 International

Wolfy ..... if you have access to the Parts fische or P E T program check out the 911T fig 1 07 05 , the intake manifold it appears that Porsche also used the BS 90 degree pancake intake manifold complete with lovely 90 degree turns for the 911 Turbo , with positive pressure in the intake all the "rules" change . Including running very small intake ports on the 930 heads . When running boost it is much better to have a smaller volume to compress than a larger one , helps reduce turbo lag . A positive displacement "blower" roots Eaton is capable of making boost quicker at low RPM which is what street cars need ; high power from 5,000 to 6,500 rarely matters much 0-40 mph you never see 5,000 rpm in most 928s .

BC

Its been a while Jim, but I DO remember going past 5k PRETTY DAMN OFTEN on both my 81 and 89!

Thats where all the fun is!

GoRideSno

Some may cringe but I hit redline almost every time I drive my car.

Now, back to Dr. Wolfgangs post.

I am no expert but....

The MP112 will flow around 850CFM @ 5psi.
From the pictures I believe this is the blower Huntley is using.
Assuming 100% volumetric efficiency at 6300rpm the 5 liter will flow only 553cfm. While Marc of Devek has a seen a maximum of 127% volumetric efficiency for an engine(probably not stock). This was at mid range rpms. An accepted volumetric efficency value for 4 valve engines is 88%. From what I gather VE is variable throughout the rpm range. From the 928 developments website I gather VE of the S4 decreases at high rpms. With 88% volumetric efficiency at 6300 rpms the 5 liter will flow only 470 cfm.
That leaves 380 extra cfm provided by the EATON MP112. 80% more air than the car needs. More air mixed with the right ratio = more power. The MP112 should be able to provide around 200 more HP for the 5 liter even accounting for HP needed to drive the blower.

Andy K

Old & New

It's good to know that the humorous smooth-talkin' stranger (with one post) can't muscle in & skew the objectivity of the board. Nice try, guy.

He's obviously someone who is not looking forward to the Huntley project!

<img border="0" title="" alt="[Wink]" src="wink.gif" />

Tim Murphy

I spin my S-Trim Vortech a tad over the recommended max speed which should be giving me aprox 1100 cfm and I can make 8-9 lbs boost. I share the same concerns with Wolfy that the Eaton might run out of flow on the top end. I don't know much about roots type blowers so it will be very interesting to see how this works out. I know that Mark R. from FAST put one on his car and ended up taking it off and going the cetrifigal route, not sure why. That roots blower was sold on ebay, wonder who bought it?

GoRideSno

Tim,
Again I am no expert but......
Consider this. A centrifugal blower will actually allow air to flow back out of the system through it while it is working. IF pressure is too high. So that tells us that as the boost level rises the centrifugal blower moves less less air per revolution. That means that maybe you are actually moving less air than you think. On the Vortech site they say the max cfm for the S trim is 1000 and it can make 680 hp. So if 1000cfm = 680hp then to make 500 rwhp you will need to move around 865cfm. Given that the A/F ratio is correct.
The Eatons are positive displacement blowers and have a high voulmetric efficency. This means if the rotors turn they move a set ammount of air. If the boost doubles, say from 5 to 10 there is not much flow loss as demonstrated by the figures of ~850cfm @ 5psi and ~ 815cfm @ 10psi for the MP112.

With the MAP system, and larger throttle body the Huntley system should be able to see right around 500rwhp without over reving the blower.

I am not favoring any system here but am helping keep this objective.
Andy K

Tim Murphy

andy,
You make a good point that the air flow will be lower the higher the pressure. It would be nice to know what the flow is at various pressures for a given supercharger. Vortech must have done some tests on this. I'll dig around and see what i can find, there has to be some documetation on this.

Z

All of the CFM stuff can be pretty misleading when it comes to making power with a supercharger. The engine doesn't care about CFM. The air mass is what matters. The Eatons have a high volumetric efficiency, but also allow some air flow back out of the system. The high volumetric efficiency occurs at the higher RPMs. The chart on the Eaton web site shows the volumetric efficiency ranging from about 55% to 95%, depending on boost pressure and RPM. The difference from 100% is what's flowing back out of the system, in ways like air flowing by the rotors, or around with them in the clearance space between them. One reason that the CFM stuff can be misleading in this discussion is due to thermal efficiency. The centrifugal superchargers are more efficient in that respect than the Eatons. In other words, even if the boost pressures and the CFM of airflow into the intake manifold are exactly the same for the Eaton as for the centrifugal, the mass of air entering the engine will be higher with the centrifugal, due to the higher thermal efficiency making it a denser air charge with the centrifugal. That air mass is what matters as far as power produced, not boost pressure, and not the CFM of the air flow. If you had the same pressure and the same thermal efficiency, you could use CFM of airflow as a more meaningful basis for comparison, but you don't. Using the CFM might be more useful in normally aspirated situations for that reason. The air temperature and pressure is likely to be close to even, or adjusted to some standard values when using CFM for any normally aspirated comparisons. Of course that doesn't necessarily mean that a normally aspirated engine will actually be able to use any additional CFM that something like an intake manifold showed on a flowbench compared to a different intake either though.

Tim:
What you want to see the relationships between airflow, pressure, and efficiencies is the compressor flow map. I'm kind of surprised that Vortech doesn't have them on their web site somewhere, but I'm sure you could get the maps for their different models if you contacted them.

Huntley Racing

I have been sitting back and watching on this one!! So I wonder who that masked man really is!?!? Anyway the question is; 'So why did we choose the EATON vs. a centrifugal from Vortec/Paxton etc...' The fact is that most centrifugal blowers ARE more efficient at higher boost levels than an Eaton. What this means is that if running say 8 PSI with everything else being even, the centrifugal should make more power. The question 'really' was what were WE hoping for? Do we want a nice peak HP/TQ number, or a bigger than stock broad power band?? From a marketing and sales side the bigger the number the more sales. From a driving standpoint the broad powerband is obviously the better solution. As an example if you have two identical cars with one making 500 HP and 500 TQ between 6000 RPM and 7000 RPM and you have the other making 300 HP/TQ from 2000 RPM to 7000 RPM, which car will be faster? The car with the broad power band will spend more time making power than the other car. The longer you spend with HP/TQ propelling you the faster you will be. I'm not sure everyone will agree here but this also holds true on the track where many many cars are 'peaky' and just don't perform like their expensive dyno charts would dictate. The cars with the broader powerband that is perhaps a little underpowered are at the finish line first. Here are two dyno charts from two 944 S2 SC cars one with a centrifugal and the other with the Eaton.

<a href="http://www.huntleyracing.com/superchargerkitpics/images/2/stage_2_dyno.gif" target="_blank">http://www.huntleyracing.com/superchargerkitpics/images/2/stage_2_dyno.gif</a>

<a href="http://www.speedforceracing.com/sc/s2_sc/16v_stage2_dyno.gif" target="_blank">http://www.speedforceracing.com/sc/s2_sc/16v_stage2_dyno.gif</a>

Both cars are running roughly the same boost. The Eaton car made full TQ as soon as the run started (if the run was started at 1000 RPM the TQ would be roughly the same!!), and held it nearly to redline in an almost perfectly flat line. The centrifugal blower car starts with over 100 lb/ft less and slowly builds as the RPMs go up. It never gets the TQ up to the level of the Eaton. Even at the top end the centrifugal car was not efficient enough to make additional power over the Eaton car!?!? In comparing the HP curves the two cars were very similar. In fact the Eaton car made more HP and pulled more RPM! This has nothing to do with the Eaton blower but instead with our manifold design. We knew the Eaton would have tremendous low and mid RPM power. We therefore completely redesigned the intake manifolds which stock, were originally designed for low RPM performance, and made them high RPM power makers. The results speak for themselves. The cars are no longer 4cyl buzz boxes. They feel like a 928 GTS with 1000 lb less weight! They don't feel like a turbo car for instance which has nothing... nothing... nothing.. then everything... then nothing again. The Eaton cars just respond instantly to throttle application and just accelerate like a sled. What I mean is they just pull and pull and pull to redline where you look down and see how fast your really going! There is no 'event' where the power is, because it’s everywhere! I should know, I drove a Huntley SC 944 S2 for over a year as my daily driver

Jim Nowak

</font><blockquote><font size="1" face="Verdana,Tahoma,Arial,Helvetica,Geneva">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva"> Both cars are running roughly the same boost. </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Arial,Helvetica,Geneva">If both cars were running the same boost, the centrifugal blower at some point would equal or exceed the power of the Eaton. The dyno charts do not reflect the same boost levels. Power and torque are both down by 20 with the centrifugal indicating a difference in boost. I do not think this is a good comparison. The Eaton looks to be at 9 psi and the Centrifugal is at 5 psi. This should help: <a href="http://www.superchargersonline.com/hp_calculator.asp?submit=1" target="_blank">http://www.superchargersonline.com/hp_calculator.asp?submit=1</a>

I do think the basic argument for the Eaton is sound. More useable power, for the street, and torque through the rpm range will make the car quicker than one that is very peaky.