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Advanced CIS Turbo Tuning Discussion Thread. Ultimate?

I though I would start a new thread on this as some of us have hijacked the “Digital WUR” thread ( Digital WUR ) and have been disscusing some great ideas that should have some huge potental.

I am hoping others will be interested in discussing advanced tuning concepts and existing best practiced as it relates to getting the most out of a CIS 930.

Issues:

Porsche seems to have designed the 930 fuel systems to work very well to just over 300hp. Past this the fuel metering system starts to stall with further increases in air flow that come with higher boost, bigger displacement, and increase in VE found with bigger cams, ports, inter-cooler, headers, mufflers…

With our demand to flow more air the AFR’s can become exaggerated and go lean before the end of the WOT operating range when the metering plate.

Current Fueling Strategies:

Fueling strategies have been developed so more fuel can be derived to support higher air flows and HP. An added fuel injector is one. This is not seen as a good solution by most experts that belive that it can creat uneven fueling to different cylinders.

Lowering the control pressure using an Andial Fueler or with a readjusted WUR that has lower on boost control pressure are valid strategys. However, this tends to over exadurate the enrichment cycle to much at first.

The latest approach is to run a fuel head that is adjusted to deliver more fuel than spec like the IA head. This delivers an increased percentage of fuel at all points of operation from start to stall. As such it requires significant manipulation of boost CP including delay of enrichment with an RPM boost clamp to try to overcome said limitation. Using the new digital WUR is a potentially a very good fit with this but still leaves some fuel delivery on the table by not curing the metering plate stall issue.

Proposal:

I believe that by curing the issue with the metering plate stalling we can get more fuel deliver from our existing heads close to equal to that of the EA head.

If done correctly it can greatly free up the true for a high flow fuel head (IA) and gain even more increased hp potential.

Reconfiguring the WUR can allow us to take advantage of these two concepts to potentially obtain near ideal AFRs at idle through curse. Allow for a near ideal on boost through redline AFR curve. Allow for reduced restriction from the metering plate upon first acceleration so it acts like an acceleration pump to increase AFR’s to a near ideal TQ setting almost immediately.

Summary:

By correcting the metering plate stalling, modifying the delivery rate of the fuel head, and modifying the way the WUR functions and fine tuning it, we can access higher HP levels safely, get increased throttle response, and do so without any external manipulation. This can be accomplished in an near OEM way.

A note:

I feel strongly this is a valid opportunity after spending countless hours studying CIS, trading hundreds of posts on Turbo boards about five years ago with other turbo nutts including some of the current top tuners, and even paying a CIS expert to help me develop my thoughts. Drawing on what I learned, another turbo nut sourced the first fuel head rebuilt to flow more fuel after my conversation with the builder. He was sourcing his parts and coatings throut IA and that was the start of the IA head. We quickly discovered issues with to much fuel. Playing with WUR tamed the to rich boost cycle but wemlost our extra fuel. I suggested dropping the boost CP back down and using an MSD rpm switch to drive a solenoid and delay enrichment. Now many are using this system I see with solid success.

I chose a different direction for my 3.3 C2T and assembled my own electronic programmable WUR using the Andial-Fueler plumping and a spec built controller so I could tune my control pressure at each rpm by load point. I spent hour’s monitoring my car AFR’s, manifold pressure, and RPM with a Motec wide band’s wires taped to the out side of my car and my lap top. I then had the WOT dialed on on a dyno. It ended up transforming my car with ideal AFR's and increased throttle response. The new Digital WUR will accomplish very much the same results.

I am not really an expert nor a professional. I make mistakes but I do love how CIS works and hope my interest will be of value to others that love these wonderful cars.

Discussion is welcomed for the greater good.

More to come.
Old 03-06-2009, 10:50 AM
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As to the Metering Plate stall issue it might be helpful to look at a digram of the Metering assembly.



As you can see the metering plate (MP) rides in a cone. Air pressure pushes down the metering plate for fuel delivery.

When the MP lip approaches the bottom of the cone air starts to spill out and the plate starts to stall before reaching its full potential.

For more HP we need the MP to advance further. The Andial fueler lowers control pressure that is pushing back to keep the MP and the metering pin from advancing. By lowering this the MP is advanced.

A modified WUR with lower on boost control pressure (CP) also achives this. To so this the WUR can be modified and re adjusted for a lower CP. For example Porsche set up the 3.6 WUR with lower on boost CP for more fuel on boost.

So how else can we keep the metering plate from stalling, to get more fuel up top, and keep the AFR curve from curving as much and going lean up top?

Old 03-06-2009, 11:03 AM
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We can do this by engineering how the Metering plate and cone works.

The plate and cone design along with CP's determined by the WUR are the "chip" or MFI "space cam" of the CIS system. Change them and you reprogram the fuel deliver curves and quantity up to the fuel quantity limit of the head.

So how can we do this.

One way is to re-configure the cone by extending it or changing the angles. This would be a major effort.

Another way I learned of from the CIS expert I retained is to add a wedge or volume to add windage to the top of the MP. This keeps the profile of the MP higher up in the cone so the air pressure can push it down further for more gross fuel flow.

This is a picture of how it might look.


This would be a very easy way to do this. Would it not be cool if all you had to for more fuel to support your new big turbo is to replace the metering plate?

There is /was such!
Old 03-06-2009, 11:14 AM
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Below is an example of such a past attempt:

Quote:
Originally Posted by cole930 View Post
Keith and Alan,

I knew I had a, "bad", pic. of this da-- thing someplace. I went through deleted
E-Mails and found it. I had sent it to Brial Leaks.

Is this what you are talking about Keith !!!!!





Cole
I looked for one of these about 5 years ago with I was tuning my 91 C2T but could never find one. They used to be marked by Automotion to increase air velocity and throttle response. As dealing with Boost was the best marketing hook ever, I suspect this was miss represented. I believe is more to help with AFR's up top.

I am dieing to see someone do back to back WOT AFR's on a dyno with one of these to see how it may effects fuel delivery.

How else can we keep the metering plate from stalling?
Old 03-06-2009, 11:24 AM
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Steve W at Rennsport Systems ( http://www.rennsportsystems.com/2e.html ) came up with relocating the hinge around which the metering arm rotates.

I heard of him doing this so many years ago and just did not understand it. Yesterday I had one of those moments where the earth shifted.

What this dose is change the lever so the metering pin moves further with the same movement of the MP. If this works like I believe the pin will for the first time be allowed to reach 100% of its travel without stall.

This should restrict the distance the metering plate can move and more keep it up in the cone where is has better fidelity with changes in air flows.

I believe this allowed him to go past building 400hp cars like the other guys to 930's that had the fuel to support up to 450hp with out an add on fueler(3.5 twin plug, 8/1 CR, .7 bar boost?), if I remember right.

I believe that for every K29 or HF turbo sold, he should be doing this mod to there car.

Lets call this the "RS/hinge pin mod"! That man is Brilliant!

But what about the HF/IA fuel head?
Old 03-06-2009, 11:36 AM
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As I noted, years ago we had a fuel head rebuilt so it was out of spec by playing with the adjustment around the internal fuel orfices. I think we settled on a goal of about 10% more fuel flow.

We got it! Unfortunately we got it every where. We could set idle CO correctly, we could set cruse AFR correctly. But one had to give. If we set idle right, we were 10% fat at cruse.

With boost enrichment we were drooping into almost the 9's. We raised the CP's to slow down the MP advancement rate and the cars AFR's started to look like stock. However, we no longer haved the fuel we needed after 5500rpm so we again drooped the enrichment CP and did a work around to delay enrichment.

At the time, we did not even understand we were not getting all the fuel the head could deliver because the MP would still stall. Even with CP's that were reduced over stock.

With the advent of the Digital WUR this head can now be properly tamed to support near ideal ARF curves and a higher leve of HP.

But still, unless we engineer the metering system for full employment, its full potential will be missed. Even with the D-WUR.

However, for us that want to take a more OEM approach combining the IA head with the RS/pivot mod opens up an total new level of fuel delivery potential and the head should become tamable with adjustment of the WUR instead of requiring boost clamps, or a programable WUR.

Keith
Old 03-06-2009, 11:55 AM
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Combining the RS/hinge mod with the IA head should have very solid potential.

As such, it should be possible to unlock that next 50hp with just the RS/hing mod gaining full movement of the metering pin. Then with the IA head there could be enough fuel for another 50hp due to the increased delivery rate of the IA head is capable.

If this is true, I would do the RS/pm first and the IA if higher Hp levels are desired.

However, these changed shuld require retuning the WUR.

The IA mod makes for an increased % in fuel delivery at all point of the metering pins travel. Changing the hinge point of the metering arm should slow down the metering plates travel a bit due to the change in leverage. To what degree each will effect or balance act each other I do not know. I guess if the IA head flow was 10% more and the pin leverage point changed the effective leverage by 10%, they could balance each out and standard WUR CP's settings may not need much change. However, I doubt that and the WUR will need to be tuned to the new expectition.

Old 03-06-2009, 12:19 PM
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With CIS we basically have two AFR curves.

One is pre-boost and this determines AFR at idle and all points under about .5 bar boost.

The second is with the boost circuit triggered.

CP determines the rate the metering plate advances with increased air pressure.

Increase CP and the plate moves slower with changes in air flow and the AFR angle drops for leaner running relative to rpm.

Decrease CP and the MP moves faster with changes in aif flow and the AFR curve steepens relive to rpm and the motor should get richer relative to air flow.

Thus, CP effects the slope of the curves.

Now we need a strategy for how to do this.

Luch time, more latter.

Old 03-06-2009, 12:22 PM
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Keith, right-on with starting this new thread! I'm listening and learning. You've got my mental wheels turning.
I haven't been following the 500+ postings on the digital WUR since I have no intention of buying one, but have always felt that we should be able to make other subtle (or maybe not so subtle) changes to our basic CIS system to get what the DWUR is promising.

Here's a thought that's been percolating in my head. I currently use the old Andial fuel enrichment, and it does indeed enrich but probably sooner than really needed. As soon as Mr. Leask gets down to the post office and ships my adjustable WUR to me, I will be exploring just exactly where and when that Andial should kick in...or if I even want/need to keep it connected. Also, I'm installing an MSD RPM switch and solenoid to delay the onboost WUR enrichment. So, I'll end up with an adjustable WUR, delayed enrichment based on the rpms chosen....and have this Andial thing wanting to enrich based on boost pressure.

I see a possible two (or three?) phased approach to AFR management with my current bits and pieces: (1) Let the Andial drop the CP at some point mid-power band to initiate the enrichment (say around .5bar), then let the RPM switch/WUR take over as the engine builds speed and is on full boost; (2) or maybe flip this all around and set the Andial to kick in only at the top end of boost (.8+bar), and have the RPM switch/WUR moderate the CP at midrange rpms when boost is not at it's peak; (3) or...here's another thought...drop the boost sensor for the Andial and have it energized with it's own MSD RPM switch instead.

In my case, it's all about gizzmos and how best to synchronize them together. The metering plate stalling that you've described and proposed solutions to seems very simple. Give me a couple hours in the shop and I'll fabricate a bolt-on plate extender (or whatever you call it). Then, set everything to dump fuel all over the place and I'll surely be so damn pig-rich and confused that I'll have to strip the car of all the add-ons, put the K26 and CAT back on and lamely return to stock!
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Last edited by mark houghton; 03-06-2009 at 12:32 PM..
Old 03-06-2009, 12:30 PM
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Quote:
Originally Posted by mark houghton View Post

(3) or...here's another thought...drop the boost sensor for the Andial and have it energized with it's own MSD RPM switch instead.

Bingo! Through the solenoid away and use the RPM switch in series with the Andial Hobs switch.

If you have a stock head, keep your WUR settings stock. If you have an IA, reset you CP's so your non boost AFR's at cruse and idle are where they should be (increase CP's). Then increase you on boost CP so you do not go pig rich with boost. Then set the Andial to further decrease CP above say 5500rpm and .8 bar boost or when you need it.

You do not want the Andial to trigger just with boost or it will just off set the boost clamp you were going to use.

Now you have two stage boost enrichment using a proven system.

Or, do what I did five years ago. Through the Andial controller away and replace it with a Additional Injector Controller (AIC) modified with an internal oscillator.

The AIC now makes the CP's at all load and rpm points adjustable for near ideal AFR's everywhere. I even disabled the boost hose from my WUR.

A custom AIC-1 also comes with a second map and lead to drive one other component.

If you have a later USA fuel head, you can take over the O2 Lambda function. This will let you get even more fuel near red line in the same manner as the IA head w/o the expense or issues.

Or, you can get a "boost control solenoid" from a 944 turbo or other source and program your boost level by rpm level. Now you can keep you WG from leaking on first boot. Run higher boost in mid range, and pull boost back approaching redline.
Old 03-06-2009, 12:54 PM
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Keith,

I am excited to see the progress and adjust-ability the DWUR affords us. I feel
it is not necessarily the total answer for making a CIS well work on a Moded 930
but is defiantly a usefully tool that gets us closer.
I have an 80 930 that I've owned for 20 years or so. I disassembled it for
paint and am now putting her back together. I'm updating the bodywork to
replicate the 964 Turbo S LeMans GT, old school Group 5 Tail and all.
Engine wise I've done most of the popular mods and I am concentrating on
optimizing what's there to create a good reliable street car that is as fast as
it can be with the mods it has without being a hand grenade. I've tried to add
the correct mods and equipment to avoid detonation. I have the 3.3 euro motor
with SC cams, a little head work around the valves, Koklen IC, 934 short track
headers, Factory K28 11/11, 964 BOV setup, moded CIS, greedy boost controller,
MSD 6Al, MSD Boost Timer, onboard LM1 wideband logging a/fr, rpm, map, and
a short track 4 speed. DWUR is coming.
I wanted to pick your brain on the BOV set up. When I changed to the
964 BOV is saw a significant difference in throttle response and am planning to
try to improve on it even more. The 934 K28 11/11 has a left side hot housing
and I will be relocating the CIS to the right rear of the engine compartment
like the 934's were. My thought is there is advantage to the shorter intake
plumbing to the turbo on the 934 set up. I plan on putting a Synchronic BOV
on the 964 elbo and dump it back into the intake. The Bov will be within 2 ft.
of the Turbo inlet. You mentioned gaining some low end throttle response
by manipulating he BOV. Im interested in you ideas and opinions on this.

Cole
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Mods: TurboKraft Custom IC, 934 Headers, GSX 61, Zork, Port Work, SC Cams, Air Mod Fuel Dist Relocated, Water Meth Injection, BL WUR, MSD 6530, Greddy EBC, Synapse Bov, Short 2nd & 3rd with 8:37 R&P, Wevo Shifter, Coupling, and Mounts, MTX-L SSI-4, Big Brakes, Rebel Coilovers, Bilstein Sports.
Old 03-06-2009, 01:07 PM
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Mark,

PS the Andial plumbing with the AIC works exceptional well. There is another board member here that has just acquired the parts to do it on his car. If you go that way you should hook up.

Would be cool of you could start a thread to document the Andial fueler with pictures of each fitting, the Frequency Valve, any part numbers, and instructions. I do not think Andial is building these anymore. We do not need there driver (from AMG) but it might be a good resource if someone wanted to source the plumbing and use the AIC or other driver to run it.

If you do this, please link it to this thread.

Old 03-06-2009, 01:14 PM
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The MP is basically a lever operating a plunger, correct? What if the MP were exchanged for a stepper motor controlled by duty cycle? This same principle is used by GM stepper motors for idle air control. I've seen this type of servo control on some mechanical injection systems on race cars. A sort of "EFI/CIS" but without the drastic conversion. Eliminate the MP altogether and control the plunger servo/digitally. Just some wild thoughts.
Old 03-06-2009, 01:22 PM
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Jeeze....my head is spinning! I'm nearly out of my element here. For the money and taking advantage of the pieces I aleady have, all I need to convert the Andial over to rpm activated is another MSD rpm switch. Put them all together and I should be able to tune this thing across the entire curve (SHOULD would be the operative word here). Unfortunately without access to a dyno within 125 miles of here, all the tuning has to be done in the cockpit - keeping my third eye on the AFR's, my forth eye on the rpms, and my fifth eye looking for Smokey The Bear.
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Old 03-06-2009, 01:28 PM
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Quote:
Originally Posted by cole930 View Post
Keith,

I am excited to see the progress and adjust-ability the DWUR affords us. I feel
it is not necessarily the total answer for making a CIS well work on a Moded 930
but is defiantly a usefully tool that gets us closer.
I have an 80 930 that I've owned for 20 years or so. I disassembled it for
paint and am now putting her back together. I'm updating the bodywork to
replicate the 964 Turbo S LeMans GT, old school Group 5 Tail and all.
Engine wise I've done most of the popular mods and I am concentrating on
optimizing what's there to create a good reliable street car that is as fast as
it can be with the mods it has without being a hand grenade. I've tried to add
the correct mods and equipment to avoid detonation. I have the 3.3 euro motor
with SC cams, a little head work around the valves, Koklen IC, 934 short track
headers, Factory K28 11/11, 964 BOV setup, moded CIS, greedy boost controller,
MSD 6Al, MSD Boost Timer, onboard LM1 wideband logging a/fr, rpm, map, and
a short track 4 speed. DWUR is coming.
I wanted to pick your brain on the BOV set up. When I changed to the
964 BOV is saw a significant difference in throttle response and am planning to
try to improve on it even more. The 934 K28 11/11 has a left side hot housing
and I will be relocating the CIS to the right rear of the engine compartment
like the 934's were. My thought is there is advantage to the shorter intake
plumbing to the turbo on the 934 set up. I plan on putting a Synchronic BOV
on the 964 elbo and dump it back into the intake. The Bov will be within 2 ft.
of the Turbo inlet. You mentioned gaining some low end throttle response
by manipulating he BOV. Im interested in you ideas and opinions on this.

Cole
Wow, what a car.

I do not know the BOV you note. Dose it have a sliding piston design with a larger piston on the top faceing the vac line? If so and the upper piston has several times the surface area as the botom piston you could copy what I did.

I sent my Compresor Bypass Valve (CBV) up so it would stay open most of the time keeping the turbo spinning faster than it normaly would. When I say most of the time I mean with at idle and cruse. Then it would close when I wanted to accelerate.

I fliped the orintation so the pressure from the turbo was trying to push the small piston of the valve open and the vacunum from the intake maniflod after the throtle body and before the intake valve would pull the big piston with manfold vacunm at idle/cruse.

It has to have a larger piston in the upper chamber so when you open the throtle to accelerabe the vacunm goes away and boost pressure will start to replace it. It is the boost pressure and the adjustable spring above the large piston that closes the CBV.

I used a hand vac pump to set the adjusable spring in the CBV at different levels to efect how fast it operated. I liked my turbo to get just a little sping befor my valve closed.

As cruse I woud get instant .5 bar boost With sport shifts I did not lose any boost on my .7bar max factory gage.

This with a stragegy I came up with to quickly lower my CP upon acceleration to motivage the metering plate to get moving totaly woke up my car off the line and from cruse.

Hope this make sense.
Old 03-06-2009, 01:33 PM
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Quote:
Originally Posted by mark houghton View Post
Jeeze....my head is spinning! I'm nearly out of my element here. For the money and taking advantage of the pieces I aleady have, all I need to convert the Andial over to rpm activated is another MSD rpm switch. Put them all together and I should be able to tune this thing across the entire curve (SHOULD would be the operative word here). Unfortunately without access to a dyno within 125 miles of here, all the tuning has to be done in the cockpit - keeping my third eye on the AFR's, my forth eye on the rpms, and my fifth eye looking for Smokey The Bear.
It dose not look like you have the IA head.

If you leave your WUR settings alone your AFR's should be good including on boost up to about 5500rpm.

Then this is what the Andial fueler was made for. It will lower your control pressure further and let you access more fuel.

The problem with the Andial it is only rpm triggered. If you set it up wrong, you will go pig fat to soon. Our cars boost pretty fast now so to really make it work we want it to trigger only on boost (there boost switch) and only after the rpm point where we need it (RPM switch.)

Thus, just hook up the rpm switch and wire in line with the Andial boost switch. Now, the fueler will only trigger when both switch's are a enabled.

This will give you the factory WUR enrichment first. Then later you will get another kick from the Andial. This is a good system.

If you screw with your WUR settings so you get more fuel with boost and then use the boost clamp to delay it that would in my opinion would be silly. You will go from to little to way to much. IWith the IA head this works because it is actually enriching its self, stock not good.

am saying go from just right, to a bit more for just right, and a bit more again for just right.

Your Andial makes the adjustment of the WUR and dealing of enrichment not needed.

Lets work this untill it make sense.

Old 03-06-2009, 01:46 PM
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Quote:
Originally Posted by 911st View Post
We can do this by engineering how the Metering plate and cone works
OK, one more comment before I stop and just listed for awhile.
The stalling MP, when it's near the bottom of it's range, probably has to do with increased air velocities flowing over the edges of the plate....because the "cone" gets progressively wider, opening up more air space between it and the plate. Thus, greater air velocity across the top of the plate creates a low pressure zone above the plate and higher pressures below...causing lift and "stall". It's basic aerodynamics, such as the curvature of a wing and the pressure differential top-to-bottom that causes lift.

So, attaching some sort of "airfoil" on top of the MP may not have much value unless it were able to follow the tapered contour of the cone as the MP moves downward. It may be worth a try, but we need an engineer type dude to do the math. The bottom line: It sounds like changing the pin location (and thus the fulcrum point of the arm) is probably the better option. But then that arm will move easier, and you would have to retune all control pressures accordingly.

For what it's worth....I've got to visualize the physics of how things work, before I can strategize how to modify.
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Old 03-06-2009, 01:47 PM
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Sorry, Andial is only boost trigered.
Old 03-06-2009, 01:47 PM
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How about making a metering plate with a "gurney flap" around the perimeter? In other words a lip around the circumference. This might increase the force acting on the plate.
I thought I've heard about a "cone" used on the back side of the metering plate by the factory on racing set-ups to smooth the airflow into the intake. Not sure if that would accomplish the early movement of the arm though.
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Old 03-06-2009, 01:58 PM
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Quote:
Originally Posted by mark houghton View Post
OK, one more comment before I stop and just listed for awhile.
The stalling MP, when it's near the bottom of it's range, probably has to do with increased air velocities flowing over the edges of the plate....because the "cone" gets progressively wider, opening up more air space between it and the plate. Thus, greater air velocity across the top of the plate creates a low pressure zone above the plate and higher pressures below...causing lift and "stall". It's basic aerodynamics, such as the curvature of a wing and the pressure differential top-to-bottom that causes lift.

So, attaching some sort of "airfoil" on top of the MP may not have much value unless it were able to follow the tapered contour of the cone as the MP moves downward. It may be worth a try, but we need an engineer type dude to do the math. The bottom line: It sounds like changing the pin location (and thus the fulcrum point of the arm) is probably the better option. But then that arm will move easier, and you would have to retune all control pressures accordingly.

For what it's worth....I've got to visualize the physics of how things work, before I can strategize how to modify.
Look back at the forces in the factory digram above. The metering plate in the cone is basically a big valve. The more air flow or pressure through it the more it opens the vavle. At some point the valve goes past its intened range and spills over. That is when we stall.

All we are doing it keeping the mass up in the cone area so the air pressure will keep pushing it open.

It is more a trial and error. What would be interesting is to develop a way to make the windage adjustable.

With the increased windage may come quicker advancement of the MP at first, this would be countered by makeing the MP smaller in diamiter. That is what they did with the aftermarket above. It is taller and smaller in dianiter.

How about a wedge like this. It could even then be turned to effect the rate of advancment some with out having to redo the control pressures?







Old 03-06-2009, 02:01 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #20 (permalink)
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