Technique needed for one person high speed split linkage test.

[Tomnistuff]

I am addressing this question to the entire group for two reasons.  Although Joe Alexander has probably done more than anyone, or at least as many high speed split linkage tests as anyone, I suspect that several others may also have developed their own tricks for manipulating the split linkages at high engine speeds.  I also suspect that many members can benefit from having a list of tips and tricks from which to choose.  Some of the answers may be worthy of insertion in the Technical Manual.

I am not completely "maladroit" but at 75, I'm not as slick or confident as I once was.

I find it easy to enrichen the IP while the linkage is split and at closed throttle  I also find it easy to lean out the the mixture while the linkage is split and the IP fuel lever is closed.  Where I have problems is splitting the linkage at a higher engine speed than idle and holding the throttle linkage fixed while enriching the fuel or holding the fuel fixed while leaning out the mixture with the throttle.  I just don't seem to have enough hands while handling hot vibrating metal and while watching and listening for subtle changes in the engine.

I am desperate enough to start thinking of making fixtures to help hold linkages and levers securely in place to help with the the difficulty of splitting the linkage at high speeds without things changing unintentionally.

Does anyone have suggestions?

Tom Kizer

[wwheeler]

My concern with relying solely on a split linkage test for RPMs higher than idle, is that the pump starts changing with inputs that would be hard to duplicate with the linkages alone. When the engine is under a load, the throttle lever is open but the pump is not spinning as fast as it would be without a load. That difference in RPM affects the speed of the IP governor which of course will affect the mixture. The magical 3D ball "computes" what to do based on these inputs.

I think the split linkage does well at idle because there is no load. At higher RPMs it might get close enough. But to really fine tune it, a meter is your best bet. You can also inspect your spark plugs and do a "seat of your pants" evaluation. My $.02.   

   

[Tomnistuff]

Thanks, Wallace, for the input.  I agree that a 2K rpm and 3K rpm split linkage tests are probably not the be-all and end-all of data desired, because of the missing load "dimension" at each of the two speeds.  In fact, more than those two "higher" speeds would be desireable as well.  However, precisely because of the shape of the magicical 3D ball and the linkage that manipulates it is likely to be close enough as you suggest.  In fact this is the principal on which decades of carburetor operation is based.  I spent half a career depending on that principal developing carburetors, and the other half a career using "meters" of various types, including engine and vehicle dynamometers, finding all the values to program into the 3D data tables so the computer could double-interpolate to arrive at the injector pulse width.  I'm way too old for any of that stuff now. 

I'm just trying to find a way to avoid dropping an IP fuel lever with the throttle open at 3,000+ rpm and burning a hole in a piston.  That's an exageration, of course, but when things get exciting with the engine screaming and too many things to pay attention to, even the time it takes me to decide what to do next can be very expensive.  I shouldn't even still be doing these things but I refuse to surrender to my age.

I'm thinking that the difference between idle SLT and high speed SLT is that at idle SLT, both levers are at an idle "stop" and your hands are for manipulating only one of the levers while you pay attention to the changes in rpm.  During the high speed SLT, both levers are somewhere in the operating range but not at idle, and they have to be separated one from the other and both held frozen in place until you decide to move one slightly without moving the other while observing the rpm changes.

I'm thinking of clamping one linkage rigidly in place at high rpm with both linkages connected together, then disconnecting them so the one not clamped can be manipulated for the SLT.

I have convinced myself that it will work.  Any opinions?

Tom Kizer

[ja17]

Some good points mentioned about SLT. However in the same sense an exhaust analyzer suffers from the same load error information unless the car is on a dyno or is being driven during the test.

[wwheeler]

Joe is correct in that an analyzer is only going to improve the results over the SLT if it is driven. I guess it all depends on how "perfect" you want the results to be. At the rebuild shop, they should do adjustments on the IP that account for engine load. Hopefully that should be good enough for most. I sent my IP in for rebuild a few years ago and have only done minor adjustments since then.  So my mixture may not be optimal across the board, but drives well enough for me. 

[mrfatboy]

I’m with Joe and Wallace. I would not attempt any high rpm fip adjustments without a gas analyzer such as the Innovate. Frankly, I would not attempt unless I was totally desperate. You really need to test with a load on the engine. Just getting the idle mixture correct  is difficult enough 🤣🤣🤣🤣

[Tomnistuff]

A little background.  When I restored the car, I sent the engine to Metric Motors for a long block rebuild and the Injection Pump to Jerry Fairchild Industries for a rebuild.  He (I think Robert Fairchild) had a little trouble with the lever hanging up, but another disassembly and reassembly resolved the problem.  When I got it back, things were very, very rich.  Eventually I discovered 6 mm (1/4 inch) of shims under the barometric cell.  Then I started checking things very carefully.  I'm still doing that.  So far, the only adjustments I've made are spark advance, IP idle fuel and Idle Air Valve together and the barometric cell shims (to get it to run).  Next I want to check for "slightly richer than leanest fuel for best torque" at 2,000 rpm and 3,000 rpm with the SLT.  My first attempts made me realize that I needed another hand or a helper.  I don't have either.  So I created this thread.

If it's too rich or too lean at those speeds, I'll make appropriate changes to the barometric cell shims, then go back and readjust the IP idle fuel and Idle Air Valve by rerunning the idle SLT.

At this point I need to say that if the 2,000 rpm and 3,000 rpm results are not identical or really close to one another with the same BC shims, then there is some other internal adjustment that needs to be made of which I am incapable and smart enough to know it.

The magical 3D ball is just a 3D surface wrapped around a movable ball.  The height of the surface from the center of the ball at any given point on that surface, and followed by a stylus, represents a fuel flow value for a given engine speed and throttle linkage position, without the fuel or air flow modifications by other devices such as the barometric cell or WRD.  Since the ball shape is fixed, and was shaped to meet the requirements of the fully warm engine based on engine speed and linkage position, there are not many adjustments to make, and they are mostly temperature related.  In my opinion, The magic of the ball does not occur in the IP.  It occurred at Bosch when the dyno data was designed into the ball and internal IP lever systems.
I don't want to adjust anything not meant to be adjusted by a mechanic.  I just want to run the high speed SLT without screwing something up due to not being able to control the test procedure variables.  I think the answer is creating artificial linkage "stops" while I'm running the test.  I'll know in a day or two when I get a chance to tast my theory.
Tom Kizer

[Tomnistuff]

Another update.  I decided that I needed to create an adjustible linkage "stop" for either the air flow linkage or for the IP fuel lever at 2,000 rpm and 3,000 rpm, so that the other without the "stop" can be slightly moved to perform the split linkage test.  I chose to design and fabricate a device that can be adjusted to provide an air flow linkage stop to set the minimum air flow any engine speed.  Then I can snap off the IP lever rod upper ball and increase or decrease the fuel flow with the IP lever to get the split linkage test results with the air flow linkage frozen in place.
The first photo shows the device with its left end having a hook to be hooked over the rear throttle rod ball that is operated by the cross-shaft, and with its right end having a larger hook to hook over the rigid tube of the valve cover ventilation system.  A relatively long screw and nut connecting the two end pieces with the hooks provides the adjustibility to set the linkage to any air flow position from idle to full throttle, well beyond the needed engine speed range.
The second photo shows the device installed and ready to be set at the desired engine speed using the small nut.  Once the speed is set, the remainder of the SLT is the same as the idle SLT.
I have not run the test yet but am ready to run it when I can get the car out of the garage when it's not raining.

Tom Kizer

[stickandrudderman]

A rough and ready test is to deliberately maladjust the BC to see if you get improvement in driveability under load. This gives you something to aim at by knowing whether you need to lean or richen by proper adjustment.

[Benz Dr.]

I do the split linkage test by undoing the rod nearest to the brake booster. Not difficult to move both pieces from that position.

[ja17]

Interesting tool Tom!

[Tomnistuff]

Thanks, Joe.  I used it yesterday afternoon and it worked beautifully.  Once the engine was warmed up (made easier by shortening the tool to keep the engine running just above normal idle speed during warmup), I shortened it more to get 2,000 rpm.

I then disconnected the ball and socket by the brake booster mentioned by Benz Dr. and then "held" the rod socket against the "rigidly held ball on the linkage" without snapping them together.  The speed was the same as when they were snapped together, so it was behaving just like an idle SLT.  The cross shaft lever was held in position as if it were against a 2,000 rpm "idle stop".

Moving the IP fuel lever more open and more closed by a couple of millimeters resulted in rpm drops with no rpm increases at any position.  Holding the IP fuel lever in place with one hand, while opening the throttle linkage slightly, also caused only an rpm decrease.  The other direction is prohibited by the tool.

My conclusion is that the 2,000 rpm IP adjustment is correct at what Ford called the "Best Torque" A/F ratio.

Redoing the SLT with the tool set to 3,000 rpm told me that the mixture was very slightly rich at this speed.  Opening the throttle linkage alone and closing the IP lever alone both resulted in a slight rpm increase (100-200 rpm) and opening the IP lever alone caused an rpm drop. 

Next, I reran the idle SLT without the tool and had to enriched the IP idle screw 3 notches and adjusted the idle air.  I now have a 900 rpm hot idle and good throttle response.

If I am interpreting the results correctly, 1) the tool works, 2) it's really easy to use and 3) my IP is correct with these shims and settings at 2,000 and 3,000 rpm based on the high speed SLTs.

Am I missing any thing?

Tom Kizer

[ja17]

Sounds like you have it "pegged".

[Benz Dr.]

Keep in mind that the A/F ratio on the throttle linkage isn't one to one as the linkage is opened. At around midpoint ( 3,000 RPM ), the linkage will provide more air than fuel, whereas both idle and WOT provide very rich mixtures.   

[Tomnistuff]

Hi Dan,

I was reminded by your last post of the typical carburetor fuel flow curve from a carb test bench that I was used to seeing fifty years ago at Ford.  I finally found something similar relating to carbureted aircraft.  I have attached the sketch showing the air fuel ratio vs air flow - idle to wide open throttle take-off.  To be honest, fifty years is enough time to forget the details of the curves.  I was a trainee Ford engineer at the time, and I've been retired for 19 years.  Thanks for the memories.

Tom Kizer

[Tomnistuff]

Oops!  I forgot the curve.

[Tomnistuff]

After I became satisfied with the fuel/air ratio at 2,000 rpm, 3,000 rpm and fully warmed up idle, I returned to the "curse" of cold start and warmup tuning.  At least having disconnected the cold start electrical system in favor of a manually wired Cold Start Solenoid, I was able to start it quickly at any temperature, but had to, and still have to play with the throttle to keep it running until it warmed up.

My last effort is in progress.  I was warming up the car in preparation for the final tuning of the warm idle after the 2,000 and 3,000 rpm split linkage test and noticed that the WRD stopped flowing air with the coolant temperature still below 50 degrees C instead of 80 degrees C. It tried very hard to stall. It's no wonder I'm having trouble keeping it running during warmup.

Today, I removed and disassembled the WRD.  I took several photos to study as I disassembled it.  It took a while to understand how it's assembled.  A hex headed dowel on the side of the housing contains an off-center pin on its end that protrudes into the WRD bore to limit upward movement of the air valve sleeve can be used to completely lock out the WRD.  It was improperly installed.  It looked OK, but there is a rolled pin that engages a "land" on the dowel to prevent it coming out of its hole and also to provide a resistance to rotation of the dowel which moves the "off-center stop pin" up or down in the bore.  The rolled pin limiting the dowel rotation and therefore air valve sleeve upper limit was insufficiently engaged in its hole and, in my WRD, the dowel was rotated , the pin was lowered to the middle of its range of adjustment and the sleeve was limited to almost no upper movement and almost no air flow because the off-center pin had lowered the air valve sleeve upper limit. 

In my opinion, based on the off-center pin position at disassembly and its effect on the air flow when I blew through it, the air flow would have been very low, almost like an air leak, when cold, and constant until the thermostat was hot enough to contact the sleeve screw.  At that point, the air vlow would shut off abruptly at a coolant temperature less than my observed 50 degrees C.

When I can get back to the job, I will provide more results of my "mystery".  I certainly am learning a lot.

Tom Kizer

[Tomnistuff]

By the way, regarding last night's post, I cannot find any place to insert round shims, nor are there any in the WRD.  My car is a 1966 Euro (Italian) 230SL manual trans.  The WRD has a long style thermostat.  The screw with the lock nut is in the center of the air valve sleeve and appears to be impossible to remove or loosen without a special tool to grip the sleeve.  It looks like it is installed and adjusted correctly anyway.

Today I will reassemble the WRD with the lockout dowel properly installed to see if the WRD works correctly.

Tom Kizer

[Shvegel]

The round shims on my 280 go under the warm up thermostat.  Since your's is adjustable via the threaded rod I assume you don't have any.  With today's tuner culture there must be a dynomometer near you somewhere?  You could adjust everything with the proper load and with your background I am sure they would enjoy meeting you.