TPS 0 = 0 which method ?

[SinNH]

Greetings,

I posted a week or so back, saying I tuned up my 2000 with a valve adj, new Bosch plugs, TPS adj, and TB sync.

Runs better, less surge , but backfires on off throttle to roll on, and seems to run rich, still surges at low throttle openings. I normally run at >3500rpm, but sometimes you just can't.

So my question is which method of the TPS adjustment do you fellows get the best results ?

Method one ( the one I used )--

setting the voltage to .370-.4 rotating the TPS

or

 

Method two -------------------

setting the voltage of the TPS as low as it can go

and then using the throttle stop screws to get .370

 

Hope I make sense.

 

Thanks,

Steve

[Tipover_Bob]

Steve:

1. Set throttle stop so low that it doesn't open the butterfly at all.

2. Set TPS as low as it can go and then up a bit. It went to .006 volts and then I raised it to .010 and locked the TPS down.

3. Then I adjusted the throttle stop screw in until the TPS read .370 volts.

4. Then you can start balancing the right throttle stop screw for idle.

5. Then balance the crossover cable for part throttle.

 

Tipover Bob

[SinNH]

Steve:

1. Set throttle stop so low that it doesn't open the butterfly at all.

2. Set TPS as low as it can go and then up a bit. It went to .006 volts and then I raised it to .010 and locked the TPS down.

3. Then I adjusted the throttle stop screw in until the TPS read .370 volts.

4. Then you can start balancing the right throttle stop screw for idle.

5. Then balance the crossover cable for part throttle.

 

Tipover Bob

Hi Bob,

That's the way I did it too the first time, now R.Lentini is saying , if I read it right, to follow the same steps , except get to the lowest voltage you can adjusting the TPS and lock it down there.

I could only get mine down to .006 , so next time I tune-up I'm going to leave the TPS set at .006 not .010 and see what happens.

Thanks

[Tipover_Bob]

Steve:

The problem I see with setting the TPS as low as possible is you may over-run the low spot. For instance, once I reach the low spot (.006 volts), I can continue to turn the TPS and I keep reading the same voltage. That means I may turn the TPS quite a bit further than necessary and thusly when I raise the throttle stop screw I may end up opening the butterfly too far to get to the .370 volts. This may not be a bad thing.

 

Tipover Bob

[T__]

Greetings,

I posted a week or so back, saying I tuned up my 2000 with a valve adj, new Bosch plugs, TPS adj, and TB sync.

Runs better, less surge , but backfires on off throttle to roll on, and seems to run rich, still surges at low throttle openings. I normally run at >3500rpm, but sometimes you just can't.

So my question is which method of the TPS adjustment do you fellows get the best results ?

Method one ( the one I used )--

setting the voltage to .370-.4 rotating the TPS

or

 

Method two -------------------

setting the voltage of the TPS as low as it can go

and then using the throttle stop screws to get .370

 

Hope I make sense.

 

Thanks,

Steve

 

Steve, there are lots of theories on 0=0, base idle screw settings, a few degrees more on initial ign timing, etc.. I haven’t owned an 1100 for a while now but when I had one I tried all kinds of TPS settings, some base idle screw setting changes, different valve adjustment changes, etc & found none to remove the off-idle surging.. Removing the pink CCP helped more than anything as well as unplugging the O2 sensor..

 

Seeing as the Motronic bases it’s basic (OPEN LOOP) fueling & spark control on internal fueling/spark maps & those are mainly modified by TPS voltage vs engine RPM with modulation varied by ambient temp + oil temp + altitude, there is some latitude in some minor adjustments that can improve the open loop operation of the engine slightly.. Problem is: most of the surging doesn’t happen while in open loop fueling control..

 

In closed loop (that is warm engine-- at idle, or at steady throttle condition under about ½ throttle, or at cruising just off closed throttle to just above mid throttle) the entire fueling is based on ONLY the 02 sensor’s feed back to the Motronic.. No matter WHAT you do or change, the 02 (oxygen sensor) is the main control & holds the fuel air mixture to real close to 14.7:1.. Now on changing throttle,, dropped throttle,, wide open throttle,, lots of engine load vs moderate throttle opening,, cold engine,, probably overheating engine,, the Motronic reverts to basic fueling maps modulated by sensor input (such as air temp, oil temp, TPS, etc)..

 

As long as the Motronic is in closed loop there is NOTHING the TPS or other sensors can do to change the basic 14.7:1 fuel air ratio (NOTHING).. The TPS or engine sensors can modulate the spark curve slightly but NOT the fuel air ratio.. Once the engine comes out of closed loop operation,, either due to changing (moving) throttle, engine load, wide open throttle, high RPM, or failed sensors then the TPS, or air temp, or oil temp, or altitude can moderate the fuel air mixture to meet engine needs..

 

Here is the problem__ On most 1100 oil head engines the surge is IN CLOSED LOOP at part throttle just off-idle.. SO, to cure the surge at that throttle condition you only have a couple of choices.. – (first)-work with the engine itself to allow it to function without surge at the rather lean 14.7:1 fuel air ratio (possibly work with valve adjustment,, possibly change the spark curve,, add better cylinder ignition like dual spark plugs,, somehow get better ignition of the 14.7:1 lean fuel/air mixture.. Or –(second)- don’t allow the engine to go into closed loop at that light off-idle steady throttle condition.. That can be accomplished by pulling the pink CCP or disconnecting the 02 sensor, or REALLY skewing the TPS settings (that bring on other issues though) ..

 

Basically what I’m saying above is: if the fueling computer is allowed to stay in closed loop at the surging operational load & RPM it will surge, period.. The 1100 oil head is an old engine design with large pistons & slow cylinder flame propagation so is prone to lean burn surging..

 

Now once you pull the CCP the Motronic will revert to basic open loop maps under some operational conditions & you do have SOME control over the fuel air ratio at specific TPS & load conditions.. (what & where exactly I can’t tell you as I don’t have a Bosch tuning chart that covers the 2.1).. Disabling the CCP or disconnecting the 02 sensor & forcing base (open loop) fuel & spark mapping is only as good as the base map programming will allow.. On the R1100 I had the base open loop map was fairly decent & allowed fair engine operation.. There were some other BMW CCP’s available & I tried all the combinations but personally found the best (on the 1100 only) was no CCP.. Some of the oddball CCP’s did nothing for closed loop fuel control (how could they) but did alter the spark mapping slightly.. Others (the ones that also required a Co pot & no 02 sensor ) did disable closed loop (no 02 sensor = no closed loop)..

 

The main idea behind the 0=0 setting is to allow the highest TPS voltage for the minimal amount of air flowing through the TBI’s.. But it still has to allow the TPS voltage to be under .4 volts at closed throttle idle.. One of the problems is the brass idle by-pass screws will add (unmetered air) air without forcing the TPS voltage to go higher to add fuel to the air.. Not a big problem at base idle but can effect the just off-idle fuel air ratio slightly (but again ONLY in open loop operation as the 02 controls closed loop fueling)..

 

The bottom line here is: (assuming a good conscientious TBI sync) if you allow the 1100 to remain in closed loop in the surging operation range all the 0=0 or fuel delivery tweaking in the world will NOT cure the surge.. If you do something to force the Motronic to stay in open loop in the surging operational range you can effect the surge slightly with 0=0 or other fueling tweaks..

 

On the 1100 I had, just pulling the CCP (then re-setting the Motronic) helped the surging in the off-idle (not completely but removed most).. I did the 0=0 & that showed no improvement above just a simple CCP removal.. Just setting the TPS voltage to .385v after the CCP was removed did seem to help the light throttle surging but it wasn’t a single operation as the valves were adjusted & the TBI balance was also done at that time..

 

One thing to keep in mind here; most people that post that a 0=0, or this TBI setting, or that tweak removed the surging or made it run smoother also did other settings/adjustments at the same time so when they say they did the 0=0 there is no way to know for sure if that was the improvement or the valve adjustment was or the TBI balance, or maybe just new spark plugs did it..

 

There is also the possibility that if your problem is ONLY in the steady state light throttle warm engine operating range you could possibly have a lazy or malfunctioning 02 sensor.. If the 02 totally fails the Motronic will disable that input & go open loop.. If the 02 stays operational but is just lazy or slow the Motronic will over-correct the fueling as it responds to the slow updating 02 cross counts..

 

Basically that (narrow band) 02 sensor is misnamed as it is more of a switch than a sensor.. For all practical purposes it is just a monkey in a box with a good nose.. That monkey can move a stick that’s sticking out of the box to basically 3 positions (left, right or straight up) .. The Motronic looks at that stick (only in closed loop mode) & when it sees it sticking straight up it knows the amount of fuel it is sending via the fuel injectors is just right.. If the stick moves left of center the Motronic sees that & knows to add fuel via the injectors, it keeps adding fuel until the stick moves to the right as which time it sees it is adding too much fuel so removes fuel until the stick moves back to the left.. The number of times that stick passes the center position is called cross counts.. If the Motronic & monkey (02 sensor) are working properly that stick will keep cycling from left to right as the monkey signals with the stick & the Motronic (fueling computer) responds by adding or subtracting fuel to keep the stick moving across the center..

 

Twisty

[smiller]

That is an excellent summation of the state of affairs when dealing with oilhead surging.

 

On most 1100 oil head engines the surge is IN CLOSED LOOP at part throttle just off-idle.. SO, to cure the surge at that throttle condition you only have a couple of choices.. – (first)-work with the engine itself to allow it to function without surge at the rather lean 14.7:1 fuel air ratio (possibly work with valve adjustment,, possibly change the spark curve,, add better cylinder ignition like dual spark plugs,, somehow get better ignition of the 14.7:1 lean fuel/air mixture.. Or –(second)- don’t allow the engine to go into closed loop at that light off-idle steady throttle condition.

To this point I would add a third choice, that is installing a Power Commander so that you can adjust the closed-loop mixture to a more suitable value. This is a very effective (if not the cheapest) fix.

[Tipover_Bob]

Twisty:

Very nice explanation. It would appear that idle balance achieved at idle should be done using the right hand throttle stop screw only. In other words, always balance at idle using the right hand throttle stop screw, making sure the cables are free, then speed up a bit and balance using the cross over cable. Always preset the bypass screws so that they are turned out equally.

 

Tipover Bob

[T__]

Twisty:

Very nice explanation. It would appear that idle balance achieved at idle should be done using the right hand throttle stop screw only. In other words, always balance at idle using the right hand throttle stop screw, making sure the cables are free, then speed up a bit and balance using the cross over cable. Always preset the bypass screws so that they are turned out equally.

 

Tipover Bob

 

Bob, yes I should think the brass screws should be set to the same number of turns out then the balance be set from there.. That only works IF the brass screws, their seats, & internal TBI passages are clean & totally free flowing (those things seem to carbon up pretty quickly) .. You do pick up a little cross side base IDLE balance equalization when the vacuum hoses for the carbon canister are hooked back up.. Even when the canister itself is removed the crossover hose should be left in place & the rear outlet plugged at the tee.. That hose doesn’t flow much but it can help keep the vacuum a little more equal than without..

 

Twisty

[SinNH]

Great forum, real answers !

Thanks for the detailed information Twisty and for your input Bob and Smiller.

Well I got my bike running about 30% better than when I bought it, and listening to you guys, it's probably "as good as it gets". ( great movie )

Today before a 230 mile ride I changed plugs to Autolite, I feel it made a difference, not much but some.

My idle is high about 1400 since I tuned up, so I think I'll hook up the Carb Stix and get idle down using the air bypass screws and live with it.

Thanks,

Steve

 

BTW, do we really have to remove the rotors to change the front tyre

When I put on a Avon Storm , I could not see anyway to get the calipers off without really dragging/scuffing/dinging up the wheel. Could have done it but , it needed way too much pressure/yanking to get the caliper off, maybe 1/4" still needed to come off the rotor to angle the caliper out.

[smiller]

BTW, do we really have to remove the rotors to change the front tyre

No, not at all. If you remove the two bolts that retain the caliper and rock it back and forth a bit you will move the brake pads back in enough to allow removal of the caliper. Just place a piece of stiff paper between the caliper and the wheel to avoid scratching the paint on the wheel.

[T__]

Steve, use masking tape on the wheel painted surface at the caliper contact area (that will protect the paint).. Then with caliper bolts removed twist & tug on the calipers to push the pads & pistons back in to the calipers.. They will then tilt & come off the rotors at a tilted angle. Simple once you have done it a few times (no need to pull the rotors)

 

Twisty

[SinNH]

Oh yea , wiggle the pads further into the caliper, while keeping an eye on the reservoir .

 

Thanks again

 

Steve