Advanced CIS Turbo Tuning Discussion Thread. Ultimate? - Page 11

911st · 04-29-2009, 06:23 PM

Agreed, I belive I noted that much earlyer in the thread.

cole930 · 04-29-2009, 06:25 PM

Indeed you did !!!!!!

cole930 · 04-29-2009, 06:36 PM

Dave,

Thanks for jumping in. There are only a couple of us that even remember these
D--- things. I bought this from Chris Fisher years ago in a box of stuff that came with my headers and Turbo. He originally saw it on a Mercedes CIS and started reproducing them for the 930's. I know Chris thought pretty highly of it but that's been so long ago I can't remember much. Any input about would be greatly appreciated. I decided to give it a try when I put the engine back end.

THANKS !!!
Cole

911st · 04-29-2009, 09:01 PM

From page one.

Quote:

Originally Posted by 911st

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?

WERK I · WERK I's Garage

Quote:

Originally Posted by cole930

Dave,

Thanks for jumping in. There are only a couple of us that even remember these
D--- things. I bought this from Chris Fisher years ago in a box of stuff that came with my headers and Turbo. He originally saw it on a Mercedes CIS and started reproducing them for the 930's. I know Chris thought pretty highly of it but that's been so long ago I can't remember much. Any input about would be greatly appreciated. I decided to give it a try when I put the engine back end.

THANKS !!!
Cole

Hi Cole,
Hope you're doing well.

I do remember when this cone was sold in one of the Porsche aftermarket parts suppliers (hint: California based) that compete with Pelican several years ago.

You mentioned to Steve about the metering plate mod.....did he happen to mention anything about having to adjust the fuel metering of control pressures?
It seems the cone "may" improve the full travel of the metering plate, but I wonder about cruising speeds where the cone may change the air flow characteristics at partial throttle.

911st · 04-30-2009, 04:11 PM

This may be a valid point.

If we keep the stock MP diameter and add volume to the top, it will advance further at all points.

If we add volume to the top of the MP and reduce its diameter (leave off the stock plate), it will slow back down the rate of advancement but should still continue past the old stall point.

Just a guess.

cole930 · 07:01 PM

Dave & Keith,

In talking with Steve the Air mod will change afr's by it's self, more air more fuel, which will initially make it fat and blubbery at idle. We think the velocity cone will improve throttle response and probably accelerate the fuel curve some. Steve does adjust the system along with his mod but did not mention anything about adjusting for the velocity cone addition. The system pressure and control pressure are going to have to be dialed in but we are sure we will have more than enough fuel to support all the HP my mods can give us.
My intent was to make sure we have all the fuel we need without machining the control cylinder. The velocity cone will either do what we think it will or it won't. and it takes 5 min. to change it back to the stock metering plate if needed.
I think, from what we have seen initially, the DWUR will then provide the added flexability and control to put the right amount of fuel where you want it when you need it.
Dave thanks for asking about my health,. I actually feel the best I've felt in 5 years. It's amazing how much damage 6 months of Chemo will do to you, but I've been clean for 10 months. I'm not exactly pretty as I look like I was autopsyed but I'm as mean as ever and going 100 MPH with my hair on fire again. And it's sure great to be here with you guys.

Cole

fredmeister · fredmeister's Garage

Hey Cole,
Attitude is a big part of the recovery process.....keeping positive is a big plus, not only for yourself but those around you that care for you. It is almost as hard on them as it is on you.
Things like this make you appreciate life so much more.
Good luck to you.

fredmeister · fredmeister's Garage

Quote:

Originally Posted by WERK-I

If I remember correctly, the added cone there to take advantage of the high velocity air passing over it. In theory, the cone adds spoiler effect to the metering plate, increasing downforce exerted on the plate to force it further in its travel. In theory.........

I never saw any scientific proof to support this theory, but it sounds good on paper.

btw, that cone is mounted properly. It only covers part of the metering plate.

The air flow through the opening is dependent on the cross-sectional area of the opening exposed between the metering plate and the machined cone in the housing at its specific height in time. Then as you can see if more air is required to flow thru the device, the metering plate must move down and create more cross-section for the air to flow thru. The angles on the machined cone are very critical as these determine the amount of vertical travel of the plate in relation to the amount of cross section that gets exposed. Basically it controls the rate of travel, a shallow angle will make the plate move more vertically per air flow and vice versa.
When the plate starts traveling to full travel it no longer moves vertically in the cone but as you can see at a great angle. The plate no longer controls the cross sectional area properly because of this and air is spilling out all over. This is the stalling phenomenon we are talking about.

What is really needed is a way to keep the plate perpendicular to the vertical axis so that the cross sectional area is kept directly proportional to the vertical travel of the metering plate and the pin inside the fuel distributor that meters the fuel. Kind of a 4 bar link.
The additional cone helps eliminate the spillage effect and also acts like a bell mouth to smooth air flow thru the cone at high velocity. Kind of like the air stacks on the Weber carbs which smooth flow of air thru the opening into the carbs.
In theory it looks like it should work, though the proper way to tell is to make no other changes but run it once with and without it installed and see what happens at full load and high rpm.

cole930 · 05-01-2009, 01:02 PM

Mr. fred,

I agree. This is such a hoot to do, I feel like a cave man discovering the wheel. it's totally trial and error. Steve has the opinion that the factory air cleaner has a lot to do with optimal air distribution and flow pattern which is reflected in the metering plate operating correctly. He has suggested using the stock air cleaner
with extra holes cut into the bottom side of the element cover. May be something to that.
I've been wanting to ask you about how you like your K27S I've been considering going that route.

Cole

fredmeister · fredmeister's Garage

Quote:

Originally Posted by cole930

Mr. fred,

I agree. This is such a hoot to do, I feel like a cave man discovering the wheel. it's totally trial and error. Steve has the opinion that the factory air cleaner has a lot to do with optimal air distribution and flow pattern which is reflected in the metering plate operating correctly. He has suggested using the stock air cleaner
with extra holes cut into the bottom side of the element cover. May be something to that.
I've been wanting to ask you about how you like your K27S I've been considering going that route.

Cole

Cole,
Gotta love the k27S, nite and day from the k26 turbo. Boost comes in very early, like 2200rpm it starts coming in. All in by 2800 or 3000rpm I have to say. Plus it is very linear now in delivery. I also replaced the US heat exchangers with GSF/OBX headers and that probably has alot to do with the response as well. If your turbo is on the way out, mine had blown the seals on the intake side, then I say it is a no brainer.
Makes the car much easier to drive on track days without all the lag. Makes driving thru corners alot easier to modulate throttle, but still has the big punch once boost really kicks in at anything over 3400rpm to 6000rpm. I never really rev beyond 5800rpm or so because I don;t see the need to or risk throwing a rod. The rod bolts are the weak link on the 3.3liter 930 turbo they don;t like high revs.
I would also suggest a bigger intercooler, love my B&B set up.

cole930 · 05-01-2009, 05:40 PM

Mr. Fred
Thanks for the reply that's exactly what I thought I would hear. I've been reading about the newer turbos and the K27S sounded like what I was looking for. I started with a K26 and went to a K27 7200, which was very nice. Now I have 934 short track headers and a K 28 11/11 from an old Brumos short track car. I'm like you as far as RPM is concerned when you run out of torque it's time to shift. I street drive only and have a short track 4 spd with 8:37 R&P and FA,HQ,QQ,WL gear set. I am looking for as little lag as possible and I'm not sure of what I'm going to get with the K28. Thanks for the help.

Cole

911st · 05-02-2009, 07:50 AM

Thought of one more way to cheaply add some more fuel up top.

By setting the normal CO adjustment to its max point or full rich, we allow the metering pin to advance further at the same point the metering plate stalls. Such an adjustment would thus give us more fuel up top.

This of course would make the motor run way to fat. Thus, by clipping the metering plate, we can get more air to flow around the MP at lower rpms to get the AFR/CO back in balance.

Quote:

Originally Posted by 911st

How may ways can we deliver more fuel on a CIS system, let us count the ways:

Readjust the fuel head (IA or shim the head system pressure).

Increase flow of stock fuel head by adding windage to the top of the metering plate.

Increase flow of stock head by reprofiling and extending the cone that the metering plate rides in.

Increase flow of stock head by relocating the metering arm pivot (Steve W. Renn Sport mod).

Lower on boost control pressure using the Andial fueler or Digital WUR.

Lower on boost control pressure by using a 3.6 WUR or readjusting the stock WUR.

Us a fuel head from a V8 and plumb on or two of the extra injectors in as an additional injector (s).

Add an additional EFI fuel injector. (Not recommended unless driven at 100% duty cycle or uneven fuel distribution per cylinder.

911st · 05-02-2009, 07:57 AM

One more.

Add a boost modified fuel pressure regulator on the fuel head return line to bump system pressure under boost.

fredmeister · fredmeister's Garage

Quote:

Originally Posted by cole930

Mr. Fred
Thanks for the reply that's exactly what I thought I would hear. I've been reading about the newer turbos and the K27S sounded like what I was looking for. I started with a K26 and went to a K27 7200, which was very nice. Now I have 934 short track headers and a K 28 11/11 from an old Brumos short track car. I'm like you as far as RPM is concerned when you run out of torque it's time to shift. I street drive only and have a short track 4 spd with 8:37 R&P and FA,HQ,QQ,WL gear set. I am looking for as little lag as possible and I'm not sure of what I'm going to get with the K28. Thanks for the help.

Cole

Check out the zork tube video. I made this zork and was a huge increase in throttle response and some power gain (seat of the pants) over the stock muffler I had. Not overly loud on highway because of wind noise but around town it is trouble.
http://www.youtube.com/watch?v=HmCQ_chad68
Also, you may be able to see the boost versus rpm on my tach in this video from Watkins Glen last summer. Look closely at the gages if you have good eyes....the video is not that clear.
http://www.youtube.com/watch?v=rPyqoSFcKCc

fred

patkeefe · 05-03-2009, 02:17 PM

Quote:

Originally Posted by 911st

One more.

Add a boost modified fuel pressure regulator on the fuel head return line to bump system pressure under boost.

Doesn't the control pressure regulator simply allow more fuel volume to the injectors via differentail pressure in the head? This is the impression I have been under. I actually found a clever little device at Summit Racing, which is basically a variable speed drive for the fuel pump which drives from engine rpm signal. I figured if one could get the WUR dialed in on lower pressure at lower RPM, there would be plenty of fuel then for high boost/RPM operation, and maybe get the mid range flat spot out.

I may have brough this up before, but that was a long time ago, so forgive any possible redundancy!

Pat

911st · 05-03-2009, 03:27 PM

Control pressure is what the WUR establishes to effect where the metering pin is positioned relative to air flow.

System pressure is the pressure in the head that is allowed to escape out through the injectors.

Differential pressure is the lowering of the pressure behind the diaphragm in the head that presses against the internal orifices that are the pathway to the injectors. As the metering pin advances, it increases this differential so more fuel is delivered.

At least I think that is how it works.

There is a pressure regulator built into the head just before where the excess fuel escapes to flow back to the tank is what determines the system pressure. Some shim this to raise the system pressure so more fuel is delivered. The problem with doing this is this increase comes in at all points including idle and cruse.

By adding another boost modified fuel pressure after the head that is progressive with increases in boost, we can keep our AFR's stock off boost but get more fuel on boost.

911st · 05-05-2009, 09:20 PM

The following is a good example of how AFR's are supposed to look like. The fuel system on a 930 is designed to support about 300hp. After that, things start to get interesting.

Quote:

Originally Posted by RarlyL8

I use the stock rebuilt WUR on my personal car. I dug through my files and found a baseline run for you. As you can see it does not dump fuel at boost onset. This WUR is not adjustable.

Go beyond 300hp and the fuel metering plate moves past the metering cone and air starts to spill quickly around the metering plate and the plate starts to stall and things go lean quickly.

You can see this better in the following pictures.

Quote:

Originally Posted by cole930

If we want to get these cars to work well w/o add ons at higher HP levels, this is the area that has to be improved upon. We need to extend the cone down further. Do this and there will be plenty of fuel for most.

Think of that cone like the map on an EFI system. This is the programming that determins our AFRs.

Manipulating control pressure can only do so much.

911st · 09-21-2009, 10:48 AM

The heart of our problem with getting enough fuel to support increased HP is the stock CIS metering system is designed to stall at an air flow rate equal to the expected maximum HP.

That is, if the motor is designed to make 300hp at 5500rpm the metering arm will advance down the cone until it gets to the targeted max HP air flow. Then the cone configuration is designed to start spilling air so the metering plate stalls at that point.

Otherwise the motor would continue to get more fuel with increased air flow that comes with more rpms past HP peak. The motor would not be able to use that extra air flow as efficiencies are falling off quickly.

When we modify a motor it flows a lot more air, the metering plate stalls at the 300hp mark, and we keep asking for air and go lean.

Understanding this is central to getting a near ideal AFR curve with a motor making more HP.

As a bandage we try lowering control pressure on boost (at the WUR or as the Andial fueler did) which dose move the stall point a bit, however, then lets the metering plate advance further than we need it to in the early stages of boost and we end up with a big fat spot on first boost.

Then we have to add another bandage so we put on an RPM clamp that delays enrichment or have to develop a programable WUR.

For someone that is skilled, it should be possible to put a CIS metering unit on a flow bench and by re-profiling the metering cone or adding volume to the top of the metering plate (see my wedge drawing earlier in this thread) we should be able to move the stall point to equal the expected air flow need to support our peak HP goal before it stalls. We would then also get proper AFR's.

We do not have much issue with getting more fuel to support HP up to 500fwhp, we just do not control it very well.

I trully belive we do not need excessive reduction in on boost control pressure, bost clamps, or D-WUR to achive our goals.

WinRice · 09-21-2009, 11:30 AM

So, your Mission, if you decide to accept it, is to fly to Germany, visit the Bosch headquarters and ask them what they're doing with all that 'old' CIS tooling, research papers, design software, etc, collecting dust in the corner. Then offer to take it off their hands and free up valuble space.

Once moved here to the U.S., use those resources to create a clean sheet CIS design with a target in the 500fwhp-600fwhp range.