FIP adjust with air/fuel meter

[garymand]

Does anyone have some experience with optimizing the FIP regulator and rod?  Please skip all the basics.  This is a many year, on-going project.  I'm trying to optimize the cruising AND the acceleration.  Can't seem to do both.  Can get the acceleration to awesome, but then its running rich cruising with light load.  The difference between the two is unacceptable lean acceleration.  I think the problem is where I am on the 3-D cam.  Gave up on using a tail sniffer and now have a narrow-band O2 sensor in one of the down pipes.  It repeats well and seems close to accurate. 

In light load cruise, it runs rich, but hits the other 'Manual" specs very well. 

My black screws are nearly all the way out, the top of heads are even with the top edge of the spring bands. 
The white screws are only 2 turns in from there (12 clicks).  This should give me the leanest cruise, but I'm experiencing that not to be the case.  I'm thinking the cam is not pulling to far in resulting in passing the sweet spot.

This is a 250SL 4 speed, with a 100K miles (other than the FIP adjustment, all else in perfect condition and adjustment) 280SEL motor that I put in back in 1980.  More details if needed.

[w113dude]

Did you check the linkage?

[garymand]

first thing.  And the write up here is the best I've seen.  Thanks.

[stickandrudderman]

Did you check the linkage?

I hope that's irony!

Please skip all the basics.

[ja17]

Yes, those 3-D cams in the injection pump get some serous wear grooves in them over the years.  Wear corrections can be made with the numerous adjustments in most cases. However, things become somewhat of a compromise after many years and miles.

If your range adjustments screws are running out of "adjustment range" an adjustment at the rack load screw or the BC will move the entire range of adjustments so you can have more room to work those screws which are running out of adjustment.

[mbzse]

Yes, those 3-D cams in the injection pump get some serous wear grooves in them over the years

Further, there is a little steel ball attached to the tip of the follower onto 3-D cam (see pic attached). This ball may become worn and develop a flat spot... Result: Spherical surface touching cam - car runs well. Flat spot touching cam - fuel/air ratio gets out of kilter, engine will cough and sputter....

A reason behind the wear is not exchanging the oil in the FI pump rear regulator part (dirty oil) or level too low (230 and 250SL:s). Another reason if seals inside pump are bad, oil in FI pump regulator may be diluted with petrol and thus not lubricate well any more. M130 engines (280SL) are of course lubricated via the engine oil flow.
/Hans in Sweden

[garymand]

Thanks ja17 and mbzse,  Good food for thought.  The pump is pretty young at 100k miles, but the steel ball roller is a good consideration.. I have notice that after a change of the screws or the rod, the adjustments are not stabalized until the car is driven a few miles.  Maybe friction in the regulator movements or the roundness of the ball roller / follower. 

And the rod movement..I am concerned about the rod.  There has never been a rubber plug at the distributor end of the pump, the hole has a flange and the end of the rod is visible with a mirror.  And the rod doesn't move like on the 250, it doesn't push in freely all the way (pushing on the screw end) It has some interplay with where the fuel link/lever is.  I'll check and report back exactly what it does, but the 250 IPr od would push in with slight resistance all the way to a stop, maybe 25mm.  This late 280SEL IP sometimes has resistance right away until the lever is rotated.

I am pretty close with the 3D cam now.  my black scews are in about 6 full turns while the white screws are about 12.  I'm getting a nice 14.5 +- .5 cruising at 3500 rpm, 70 mph.  WOT is maybe 2 clicks lean at 13.0.  I'll add 2 clicks gas and head home from work and see what happens.  I have a 50 mile freeway 50 feet to 1700 feet (570 M) climb going home.  Sure is fun driving this car with the fuel set well.

FYI, Someone in a 5 speed comment said they were tired of shifting half way through an intersection from a stop.   -I'm finding that is a symptum of a lean top end.  When it is rich enough, my motor pulls eagerly all the way through a large intersection.  When it is lean, the motor looses enthusiam and feels like its not going to go faster unless you shift.  Just an FYI. 

Oh yes, Stickandrudderman,  I was trying not to waste anyone's time.  I first adjusted the linkage the first night I had the car home in 1971, just after I adjusted the valves, dwell, timing, spark plugs, oil change....   

[star63]

I also bought a O2-sensor (wide band). It really makes the adjustment easier. I'm keeping it installed for now. Going through different rpm & load combinations helps me to fine tune the FIP little by little.

At first, I had to add shims under the BC (now 4 mm) because the white adjustment screws went out of range. I also realized that there is quite a bit overlapping between the black and white screw "zones" i.e. when you adjust white screws you may have to compensate by turning also black ones.

I'm now quite satisfied with the adjustment. When cruising at 80-90 km/h (my normal cruising speed) the AFR is about 15. This is on a lean side but the engine seems to tolerate it well and the gas mileage is good. As soon as I press the pedal to accelerate the AFR goes down to 12.8 and the car feels powerful.

I found it difficult to adjust the WRD. The engine was running very rich when cold. I removed all the oval shims but this didn't help enough. I ended up putting a 0.8 mm shim washer between the plunger and the spring, which helped me to get the AFR to acceptable level.

- Petri

[garymand]

Great, thanks for the pics.  What readings do you get at 1500 and 2000 both with 200mm HG vacuum? Those are th adjustment points in the BBB. I'm guessing it just going rich at may be 13.5 - 14.0?

I found that setting the low end at 1500/200mm is the starting point.  Then set the 2000/200 with the white , then last at full throttle your 12.8 sounds good.  I haven't been able to get mine that lean at cruise, but my motor is from a 280SEL that weighs what, 1000 lbs more?  So at cruise, the FIP cam is pumping more fuel that this Light Sport needs. 

From cruise to accelerate, my meter says the engine goes lean first then rich to the ~13.0  But with the narrow meter I can't tell what the real numbers are.  Wify hasn't given me the budet for the wide band, on top of the radiator and clutch.

[Benz Dr.]

These engines normally run rich at idle and lean out at crusing speeds. WOT should be rich - you need more fuel to pick up speed. A lot of this is in the throttle linkage where the air control valve is opening faster than the IP through mid range and then becomes more linear as it approches full throttle. The one thing you don't ever want is a lean condition a WOT.

[star63]

I don't have the Blue Book and I'm not familiar with the prosedure you described.
I hooked up a vacuum gauge today and measured the AFR. I had to use brakes to keep the rpm constant at 0.27 bar vacuum in the manifold.

1500/200mmHg gave AFR 14.5
2000/200mmHg gave AFR 16

I don't know what those numbers should be but the engine works great.

- Petri

[garymand]

They low, leean.  They both should be just rich, like 13.5 and 14 aprox.    My guage doesnt have #.s, just led segments for lean, ideal, rich.  I just ordered a numbered gauge.   The low end and top end are under partial load. So they need to be a little rich.  I think stoic is 14.7, lean is lower numbers.  Yours are higher and the top partial is really lean, which tells me you have a good margin of untapped power!  As Dr. Benz says, these cars perform best on the rich side of the gauge: 13 to 12 AFR.  I was loosing maybe 20 horse out of 170. 

Now you can have some fun: turn the white screws 4 clicks rich, CW.  Take care to turn each 4 turns.  It is easy to loose count.  draw picture of the slots relative to the springs, mine are insynch: slots perpendicular to the spring at the same time, so when I turn 2 clicks, I can see which screw has not been turned.  Then I turn the other 3 clicks and go back to increment the first one and now they are both back to perpendicular.  I have screwed it up more often than I know.

Also, I much rather drive up a hill than using breaks.  You can't feel how well the car is pulling with your breaks on.  If it feels just as good or better, Great.  Be sure to drive 5 or 10 miles to let everything stabalize for repeatable numbers.  Then repeat.  keep repeating util you find BEST, which you will have to go back to find again.

Question: When you first press the pedel to accelerate, does you AFR dip lean prior to going rich? How much?

[star63]

Question: When you first press the pedel to accelerate, does you AFR dip lean prior to going rich? How much?

If I press the pedal only a little the AFR will momentarily go to 15.5 - 16 but the engine will not hesitate. Immediately after pressing a bit further the AFR drops down to 12.5 - 13 and the car really pulls well. If I floor it the AFR will go to as low as 11.5.

For the most of the time in normal traffic the AFR stays between 13.5 - 15 and the engine runs extremely well.

I may try turning the white screws richer later but at the moment I'm happy with it. (Believe me, I have turned those screws dozens of times to find the current setting. It's quite messy to collect the oil that comes out every time you open the cover...)

- Petri 

[garymand]

Now I know why your numbers are so good.  I was a little concerned about the quick dip, but suspected it is normal for this injection.  thanks for verifying it.  I certainly know about the oil.  I should have the gauge and mthe car back on the road next week  I'll let you know what my #'s are.