TPS adjustment, What Voltage is Yours?

[Mike Stewart]

OK,

 

A few years ago, 2001 to be exact, I was fighting the stalling coming to a stop sydrome. TPS adjustment, throttle sync., valve adjustment, larger valve adjustment and the problem went away. I used the FIM Unimap way to adjust my tps as follows:

 

 

 

"We use the following sequence to correctly align all parts of the induction system. This sequence is essentially the same as the factory recommended sequence:

 

Set the Throttle Position Sensor on the throttle shaft. To correctly do this you must:

Completely back off the idle stop screws on both throttle bodies.

Use the Mathesis tester or a Digital MilliVoltMeter to read the throttle sensor voltage. To do this you should tap the butterfly with your finger to ensure that the butterfly is completely closed against the body. Then you turn on the ignition and measure the voltage on the throttle sensor:

P7 or P8 ECU: Pins 11 and 17.

1.6M ECU: Pins 16 and 30.

1.5M ECU: Pins 22 and 11.

If the sensor does not read 150mV Plus or Minus 2mV then you need to adjust it:

Slacken the lock screws on the throttle sensor using a screwdriver or 7mm socket.

Carefully move the sensor whilst reading the voltage.

Retighten the lock screws a little at a time, each time reading the voltage and adjusting the sensor.

Note that you should probaly overshoot the reading by about 5mV on slack screws, because when you tighten them the reading will change by about 5mV.

Repeat until perfect. This takes a lot of practice.

The factory manuals specify +/- 5mV but we feel that this is not accurate enough. many owners will attest to the difference in performance when the sensor is set perfectly.

Re-set the throttle stop screw (or screws) so that the engine idles at around 1200 rpm. This is not a final setting for the stop screws, merely a step in the procedure. Typically this will produce a voltage of around 300mV on the TPS. This value is completely arbitrary and is not important. Many people misunderstand the factory manual in this regard and will try resetting the TPS until they get 1200 rpm idle and exactly 300mV on the sensor. THIS IS WRONG !!!. The actual voltage on the sensor at idle is irrelevant to correct sensor positioning on the throttle shaft. Trust Me !!

Synchronise the Butterflies:

Close the airbleed screws completely by adjusting CLOCKWISE. If you don't do this then the throttle vacuum will still reflect any air passing through the bleed channels and the butterflies will not be perfectly synched.

Attach vacuum guages to the manifold port on each cylinder and run the engine.

Adjust the throttle butterfly link shaft until vacuum is identical.

Rev the engine and confirm that vacuum tracks on both cylinders throughout the throttle and RPM range.

Re-adjust the link shaft until satisfactory results are obtained.

Do Not adjust the throttle link shaft after this point.!!

Set the IDLE Balance by adjusting the airbleed screws counterclockwise and confirming that the vacuum is identical for both cylinders at idle. You can rev the engine and observe vacuum tracking through the rev range, and then observe idle vacuum restabilising. NOTE Since the airbleeds are designed to iron out any irregularities in the throttle's function, by their nature there is no default setting, unlike the idle screws on a carburettor. If anything the default setting is fully closed. Airbleeds can also be balanced using a 2 channel CO meter. In this case, just adjust the bleeds until both cylinders have the same CO.

Adjust the IDLE Mixture. Finally you get to set the CO Trimmer ! This will affect both cylinders by the same amount, so you need to set the airbleeds first. A typical CO figure for idle is 4% to 6%, but automotive regulations usually specify a CO of under 1% to meet emmissions standards. A V-twin will idle very poorly if the CO is set below 1%, so if you are really bothered try a setting of about 3%. Note that you may need to finesse the airbleeds at this stage.

Adjust the IDLE RPM. Set the idle rpm at the manufacturer's figure (usually 1100 - 1200 rpm) by adjusting the throttle butterfly stop screw (or screws). We recommend 1200 rpm for Ducatis and Guzzis, possibly 1500 rpm for Ducati 996SPS models.

Finally, note that the last three steps are usually repeated until an acceptable balance of Idle Balance, Idle Mixture, and Idle RPM are obtained. This is normal. Do Not adjust the throttle synchronisation link shaft once it is set in the early stages. If you do this now, you will need to go through the entire sequence again.

So hopefully you will have an engine which now idles, accelerates, and delivers full power faultlessly. Again, if you are not confident about all of these steps, then we suggest you use a dealer who has the skills and equipment. It is not worth adjusting the CO trimmer unless the entire sequence is followed without skipping any steps.

 

OK, my 00 V11 Sport now reads .298 MV. with the throttles closed (runs great) while my other bikes are at .463 MV and .643 MV (also run great). I have not adjusted the TPS on my other bikes or even checked the voltage till now.

 

What I am getting at is to use a powercommander map made by a tuning center, the map adjustment is very critical. Your TPS voltage needs to be as close as possible to the original bike the tuning center made the map for on the dyno. It also seems that most bikes have a stock voltage of .5 MV or more. And as a last note, I read somewhere that the timing is also controled by the TPS . So what voltage does your bike have?

 

Sorry to make you all think,

Mike

[jrt]

At idle, mines about 550 mV. I don't have data for 'fully closed'. No PCIII.

[Mike Stewart]

Just found this on the MPH site:

 

Following is Mike Haven's article from the MGNOC Newsletter on Injection Set-Up for all Guzzis.

Tuning the Guzzi EFI

 

This system is an open loop type. It uses air and cylinder head temperature sensors. These are NTC, negative temperature coefficient. As they heat up the resistance goes down. The electronic control unit (ECU) is the brains of the outfit. I t sends a low current voltage signal to these temp sensors where it is “grounded” to a varying amount based on the temp. The throttle position sensor works in a similar way. More throttle angle, more voltage. The signal from ECU to these sensors is known as reference voltage. About 5 volts open circuit. The camshaft position sensor is an inductive type. It counts the teeth so the ECU knows where the pistons are in their stroke and the engine speed. So the ECU knows speed, load and temperature of air and engine. The big three. But not exactly how much air. So all this info goes into the ECU. It decides in an instant how much fuel to inject on the next cycle. Both injectors get the same signal. The amount of fuel is governed by the time the injector is turned on or open. This is the “pulsewidth”. .It's measured in milliseconds. Around 3 ms is normal idle pulsewidth. It is much more under heavy acceleration.

 

In theory this is all great. These systems have had problems on bikes ,and not just Guzzi’s. Mainly because of cost or space limitations, there have been no provisions for measuring the actual induced air. It’s a calculated model at some elevation .A real air mass meter with oxygen sensor closed loop control would make for a bike that runs perfect.Not likely to happen. So lets make the most of what we have to work with.

 

Any maladjustments can turn a great running bike into a sputtering pig. These are much more sensitive than carbed bikes. To start the setup you will need a very accurate way to balance the throttle butterflies. I have used mercury sticks, but really have been impressed with the convenience and precision of the Twin Max electronic balancer. Access to an exhaust gas analyzer is a boon.

 

There are brass bypass screws on the TB’s. Turn them in counting the turns until closed. Write it down. Connect your balance meter/carb sticks and start bike. Ignore the fact that it runs worse than it did. The TB must be adjusted to a very fine degree of balance .Most models its done with a plastic thumbwheel under the left side TB. The most important part of the synch is to do it at 3000 rpm .This is where the engine moving some air. Hold throttle steady. Don’t worry about what it does at idle right now. After the synch is as good as you can get it, you can see if the base position of the throttle plates is close at idle. Disconnect the linkage from left to right for this step on 4 valves .There are stop screws under the TB if this needs adjustment. Then check the balance at just off idle. Set the bypass screws to the specs first. If out of balance adjust the brass air bypass screws. There are new specs for the air screws and TPS. See chart.

 

The point here is to insure that both cylinders are getting the exact same amount of air. Because they are going to get the same amount of fuel ,whether its right or wrong. Since there is no provision in the system to measure the actual induced air the system is dependent on this basic fact. At the CO specs MGNA and EPA agree on it is not really set too lean to run right. If there is not air induced that is not part of the original equation. After all this balancing act is done you should have a fairly decent running bike. The next step is to check the idle CO. (Carbon Monoxide)This step requires the gas analyzer. It is adjusted by a screw on or in the control unit up until the 15m system. 99/up.These require a PC and the Marelli software to do the screw turning electronically. Richening up the bike get rid of flat spots or running faults is rarely the answer. The screw or PC only has effect at idle and just above. See specs chart for your model.

 

The above applies to all but the Quota ES. Poor old Quota, it got a bad rap because of the fact that most of them run bad as delivered. This is again due to an air imbalance. Not a lean condition. Fixing it is a little more work but it can transform a bike from insufferable to quite nice in a short time. The unique( to MG ) single throttle is actually another automotive part. It looks like the base plate of a Weber 2 barrel carb. The butterflies are geared to each other by a pair of arc gears. One of these has a screw that holds it in relation to the shaft that it turns. This is the one for the left side. The TPS is on the shaft for the right side. See where the problem lies? The Weber factory claims that these are set on a flow bench and are perfect. NOT. The earlier method of providing a “balance “ was with the bypass screw on the right side of the TB. It should be closed lightly and never be opened again. Ever. Now the fun starts. Gain access to the screw on the front of the left side gear. A 7 mm socket on a flexible handle will get to it. Then connect balance meter and run bike at 3000 rpm. The more precision you can muster ,the better your bike will run. Perfection is acceptable. After this the idle should be in balance on its own. If not , tough. Leave the bypass screw alone closed. Set TPS and CO. A note on TPS. There are many methods floating around. The specs provided are intended to be used on a bike that has all throttle linkage in place,at idle. Live running measurement.

 

 

Bad Gas mileage on cold days

 

I have had complaints of bikes that give very poor gas mileage when its cold 40 F and below. I haven’t tested it yet but I think that because of the limitations on temperature control inherent in air cooled motors that this is something the designers just didn’t deal with. Since there is no thermostat to regulate the temp, the fins are designed to keep the engine temp in control under normal, for motorcycling, air temps. The EFI air temp signal has a very minor effect on the overall pulsewidth. Bosch says 5% of the input control is air temp.So the engine temp sensor is telling the ECU that its still cold and needs the additional fuel. Thus the poor mileage when riding in cold temps and back to normal when it warms up again. I have heard of swings of lows 30's to low 50's on the same bike , same conditions , different days. So I am developing a way to have a false warm engine reading available to switch on when the bike is ridden on cold days. Should be ready for beta tests soon. Volunteers?

 

Mike Haven - mphcycles@sbcglobal.net

http://www.mphcycles.com

16510 Park Row

Houston Texas 77084

(281) 579-8885 - (281) 579-9035 (Fax)

 

 

 

And here are some TPS specs from the MPH cycles site:

 

DEGREES VOLTS 2002 California Stone

3.4 0.501

3.6 0.524 Anything below 4 degrees open ECU considers bike to be at idle (as seen by 'flag' on diagnostic program)

3.9 0.567 Anything above 80.5 degrees open ECU considers bike to be at WOT (as seen by 'flag' on diagnostic program)

4.1 0.579 No diff in voltage noticed when bike was running

4.8 0.657 bike idles at 1175 rpm, 3.6 degrees throttle opening, -5 fuel trim

5.9 0.773 bike runs real damn good

6.5 0.836

8.5 1.055

9.1 1.121

10.4 1.258

11.7 1.392

12.2 1.438

13.7 1.609

15 1.743

15.7 1.812

16.3 1.874

17.2 1.964

18.7 2.12

19.4 2.2

21.8 2.46

22.9 2.57

24.7 2.77

26.2 2.93

27.7 3.08

29.7 3.3

31.7 3.38

33.8 3.45

35.2 3.47

36.6 3.51

38 3.56

39.4 3.6

41.5 3.66

45 3.76

47.1 3.81

49.9 3.9 Centauro Chart

53.4

55.6

57.7

61.2

64

67.5

69.6

72.4

74.5

77.3

79.5

80.9

83.7

84.4

4

4.05

4.11

4.2

4.28

4.37

4.44

4.52

4.58

4.66

4.71

4.75

4.84

4.86

1.7 0.311

2.1 0.365

2.5 0.408

3.6 0.515

5 0.67

10 1.203

20.1 2.296

40.1 3.59

82.3 4.76

 

 

So it looks like the voltage should be aprox. .5 volts or just a little more with the bike running at idle with the fast idle lever off.

 

Mike

[Guest ratchethack]

Mike, for PC III equipped Guzzi's, Todd Eagan recommends 500-525 mV after valve adjustment, TBs balanced, linkage connected and idle ~1100 RPM. Timing control is not yet available to my knowledge, but "soon" has been bandied about since late last year.

[al_roethlisberger]

I have yet to ever be able to get a good reading on my TPS. Fortunately it has always seemed to be close enough apparently

 

I've tried putting the needles/probes in the connectors, etc... to no avail.

 

I've thought about making an inline connector with leads, but it hasn't been a priority.

 

al

[O2 V11]

Mike try this, this is the response I got when I posted a query regarding TPS setting for a PC with a stock map. I followed Mr Bean's posting and it worked for me. Hope it helps.

Rob

[Guest ratchethack]

I've been setting & re-setting my TPS voltage, chasing an optimal idle setting - the one likely to give 1100 RPM under most conditions after full warmup. My bike's idle varies slightly +/- 100 RPM, and of course the TPS setting varies with idle RPM. In the iterative, back & forth process, I found that an easy way to monitor TPS voltage was to insert stripped-back lengths of bell wire into the back of the TPS connector (top and bottom pins), running the wires right through the protective rubber boot covering the connector. With soldered-on, shrouded spade connectors at the ends of these bell wires zip-tied back against the connector, I've got a very convenient way to monitor my TPS at any time. Works like a champ. I find that it's relatively easy to set at 515 mV, for example, but a week later, without disturbing anything, the reading may be +/- 15 mV... Temp certainly affects it, but temp dosen't seem to be the only factor. The engine seems to run the same in this range, but it's kinda curious to track it...

 

NOTE for Al: Strangely enough, my riding pal LeMans Dan thought my setup was pretty nifty, so we tried to do it on his '04 LeMans (also with PC III). But inexplicably, after lots of fiddling around (same routine - key in on position, engine not running), we couldn't get any voltage reading whatsoever at his TPS using different techniques to probe the pins...

[droydx]

Hmm, the pins in the connectors always has worked for me. The TPS itself is very sensitive to movement and is vexing to try to dial in. I think I started at .125mv with everything closed down.....maybe a little more than 525mv..more like 575 at 1100....is where I think I left it at after balancing, etc. Bike runs strong through all ranges, and I have a stuchi x over FBF airbox lid elimiantor filter and Mistral Ti Oval silencers with a PC commander....self tuned to gud enuf standards.

Andy

[Guest Bruce]

Mike,

I have mine set at .65V at idle. Stock 2000 V1100. The bike starts right up and runs clean top to bottom w/ strong mid-range and this is good enough for me. As purchased it was at .525V. The mid-range was gutless and it pinged something fierce at this setting. Visions of holed pistons danced in my head.

 

Al,

I taped into the approriate wires under the seat near the cpu by carefully removing a little insulation. When trying to measure something as small as 1/100 of a volt good contact is essential. Apparently there are splices w/ test ports built in for just the purpose but I haven't felt the need to go there ( too much other stuff in need of tinkering ).

 

Bruce

[John A]

I find it useful to set the TPS at wide open throttle and disregard what it is at idle or with blades fully closed.The reading at closed fluctuates depending on how hard you push on the thing but at WOT it's always the same.Theorectically it should be at least 80% of the reference voltage at WOT.On my hotrod Bassa I set it at 4.86.On Mikes Centauro I set it at 4.83 as it has an unknown chip in it and seemed to be running a shade rich. a change of .01 volt makes a noticeable difference but you cant adjust that with any repeatability at idle or closed throttle blades.

[stormsedge]

Mine is at about 425mV. k