• Ciao Guest - You’ve landed at the ultimate Guzzi site. NEW FORUM REGISTRATIONS REQUIRE EMAIL ACTIVATION - CHECK YOUR SPAM FOLDER - Use the CONTACT above if you need help. New to the forum? For all new members, we require ONE post in the Introductions section at the bottom, in order to post in most of the other sections. ALWAYS TRY A SEARCH BEFORE STARTING A NEW TOPIC - Most questions you may have, have likely been already answered. DON'T BE A DRIVE-BY POSTER: As a common courtesy, check back in and reply within 24 hours, or your post will be deleted. Note there's decades of heavily experienced Guzzi professionals on this site, all whom happily give endless amounts of their VALUABLE time for free; BE COURTEOUS AND RESPECTFUL!
  • There is ZERO tolerance on personal attacks and ANY HYPERLINKS to PRODUCT(S) or other competing website(s), including personal pages, social media or other Forums. This ALSO INCLUDES ECU DIAGnostic software, questions and mapping. We work very hard to offer commercially supported products and to keep info relevant here. First offense is a note, second is a warning, third time will get you banned from the site. We don't have the time to chase repeat (and ignorant) offenders. This is NOT a social media platform; It's an ad-free, privately funded website, in small help with user donations. Be sure to see the GTM STORE link above; ALL product purchases help support the site, or you can upgrade your Forum profile or DONATE via the link above.
  • Be sure to see the GTM STORE link also above for our 700+ product inventory, including OEM parts and many of our 100% Made-in-SoCal-USA GTM products and engine kits. In SoCal? Click the SERVICE tab above for the best in service, tires, tuning and installation of our products or custom work, and don't miss our GT MotoCycles® (not) art on the BUILDS tab above. WE'RE HERE ONLINE ONLY - NO PHONE CALLS MADE OR RECEIVED - DO NOT EMAIL AND ASK QUESTIONS OR ASK TO CALL YOU.
  • Like the new V100, GuzziTech is full throttle into the future! We're now running on an all-new server and we've updated our Forum software. The visual differences are obvious, but hopefully you'll notice the super-fast speed. If you notice any glitches or have any issues, please post on the Site Support section at the bottom. If you haven't yet, please upgrade your account which is covered in the Site Support section or via the DONATE tab above, which gives you full site access including the DOWNLOADS section. We really appreciate every $ and your support to keep this site ad-free. Create an account, sign in, upgrade your account, and enjoy. See you on the road in 2024.

15M TPS Voltage versus Degrees, are the two the same? Maybe... Parley!

dugr

Just got it firing!
Joined
Jul 30, 2014
Messages
14
Location
Laguna Niguel, California
To spare you my agony, here's the cutting to the chase question… What is the best method to establish the TPS position without using the 150mv method on a 15M system.

Forewarned... Below is an overview of what I've been going through historically in regards TPS, settings, some theories and just how tormented I am...

I have read and reread everything I could find regarding setting up the 15M Marelli fuel injection for my 2000 Bassa and still, it’s up for debate.

Some subscribe to the idea that with the TB completely closed with the idle/degree stop backed off as to not interfere with the TB, the voltage should read 150mv. This gives you an absolute reference point for setting the TPS. Then, set the voltage for idle/degree stop somewhere between 470-520mv which gives you 3.6 degrees +/-. Measuring with GuzziDiag or, other software, the TB should be around 3.6 degrees. Sync the right TB idle/degree stop using vacuum gauges using the left as the master. With the vacuum gauges still attached, take it up to 4-5K rpms to balance the TB linkage. Recheck the TPS voltage and the vacuum at idle then you’re set.

Makes sense, or does it? Not in my case. I can’t get the idle down below 1350 rpm's unless the air bleeds are closed and I back the idle/degree stop down to 3.03 degrees / 470mv. Currently, at full throttle it reads, 87.86 degrees and 4.939V.

Others take a more “maybe” approach and disregard the 150mv reference point completely and use 3.6 degrees as the Holy Grail as a reference point which, should have your TPS voltage @ 470-520mv.

Maybe I missing something but, I see a flaw in this theory is, since the TPS is what tells the computer what degree the TB is at. How can that be accurate measurement of degrees since the TPS setting is part of the variable too?

The only way I know the degree method would work is to have an absolute reference point with a degree wheel attached to the TB shaft to set the stop at 3.6 degrees, then take measurements to adjust the voltage on the TPS to 470-520mv. That seems to be a difficult task unless you remove the TB from the engine and make those measurements on a bench.

Tell me if I’m going the wrong direction with this “maybe” next thought. Taking readings from GuzziDiag, when I open the throttle to 3.58 degrees the voltage is at 529mv. Using the current TB setting (whatever degree it is at) since the idle is decent, then using a voltmeter, adjusting the TPS to 529mv would give me 3.6 degrees as a new “maybe” baseline.

When I got this Bassa it had a sensitive off-idle throttle response, a lean stumble cruising and a random cough. I cleaned the TB’s recalibrated the TPS to 150mv, replaced the spark plugs, plug caps (one was bad), and plug wires. It was an improvement but, still not right. I ran GuzziDiag and changed the CO trim from -43 to -10 (I just grabbed a random number as a starting point), it cleared up the cough, throttle sensitivity is now gone and it cruises with less vibration. It’s not bad now but, in the process of the changes, there has been loss in power as though the timing is retarded which leads me back to the TPS settings. It's a vicious circle.

“Maybe”, may just be the Italian way… Maybe...
 
To spare you my agony, here's the cutting to the chase question… What is the best method to establish the TPS position without using the 150mv method on a 15M system.

Forewarned... Below is an overview of what I've been going through historically in regards TPS, settings, some theories and just how tormented I am...

I have read and reread everything I could find regarding setting up the 15M Marelli fuel injection for my 2000 Bassa and still, it’s up for debate.

Some subscribe to the idea that with the TB completely closed with the idle/degree stop backed off as to not interfere with the TB, the voltage should read 150mv. This gives you an absolute reference point for setting the TPS. Then, set the voltage for idle/degree stop somewhere between 470-520mv which gives you 3.6 degrees +/-. Measuring with GuzziDiag or, other software, the TB should be around 3.6 degrees. Sync the right TB idle/degree stop using vacuum gauges using the left as the master. With the vacuum gauges still attached, take it up to 4-5K rpms to balance the TB linkage. Recheck the TPS voltage and the vacuum at idle then you’re set.

Makes sense, or does it? Not in my case. I can’t get the idle down below 1350 rpm's unless the air bleeds are closed and I back the idle/degree stop down to 3.03 degrees / 470mv. Currently, at full throttle it reads, 87.86 degrees and 4.939V.

Others take a more “maybe” approach and disregard the 150mv reference point completely and use 3.6 degrees as the Holy Grail as a reference point which, should have your TPS voltage @ 470-520mv.

Maybe I missing something but, I see a flaw in this theory is, since the TPS is what tells the computer what degree the TB is at. How can that be accurate measurement of degrees since the TPS setting is part of the variable too?

The only way I know the degree method would work is to have an absolute reference point with a degree wheel attached to the TB shaft to set the stop at 3.6 degrees, then take measurements to adjust the voltage on the TPS to 470-520mv. That seems to be a difficult task unless you remove the TB from the engine and make those measurements on a bench.

Tell me if I’m going the wrong direction with this “maybe” next thought. Taking readings from GuzziDiag, when I open the throttle to 3.58 degrees the voltage is at 529mv. Using the current TB setting (whatever degree it is at) since the idle is decent, then using a voltmeter, adjusting the TPS to 529mv would give me 3.6 degrees as a new “maybe” baseline.

When I got this Bassa it had a sensitive off-idle throttle response, a lean stumble cruising and a random cough. I cleaned the TB’s recalibrated the TPS to 150mv, replaced the spark plugs, plug caps (one was bad), and plug wires. It was an improvement but, still not right. I ran GuzziDiag and changed the CO trim from -43 to -10 (I just grabbed a random number as a starting point), it cleared up the cough, throttle sensitivity is now gone and it cruises with less vibration. It’s not bad now but, in the process of the changes, there has been loss in power as though the timing is retarded which leads me back to the TPS settings. It's a vicious circle.

“Maybe”, may just be the Italian way… Maybe...

Yes you are wrong. The procedure in the maintenance manual is correct. I believe Kiwi Dave nailed your problem of a vacuum leak raising your idle. Go back, find your vacuum leak then set up the TPS per the manual. The ECU correlates voltage to degrees open. That is why it is important to have the 150 mV at fully closed as a reference point. Considering the Bassa has been out of production for may years, your vacuum leak may very well be the rubber parts that connect the throttle bodies to the intake manifold.
 
Vargant, Thanks for the info. I agree... too lean. I just set the TPS @ 529mv from where it was at 470mv and I was able to adjust the idle with the air bleeds. I took it for a run. What a difference. Haven't touch the CO yet but, I will now that I have a good TPS reference point. A few little tweeks to the CO and I should be good.
 
Yes you are wrong. The procedure in the maintenance manual is correct. I believe Kiwi Dave nailed your problem of a vacuum leak raising your idle. Go back, find your vacuum leak then set up the TPS per the manual. The ECU correlates voltage to degrees open. That is why it is important to have the 150 mV at fully closed as a reference point. Considering the Bassa has been out of production for may years, your vacuum leak may very well be the rubber parts that connect the throttle bodies to the intake manifold.
That was my first suspicion. No canister or vacuum lines. I may take some throttle body cleaner to the rubber and see if sucks it in and changes the idle, just to take it one step further. But, the intake manifolds rubber looked good when I had the throttle bodies off to clean. Increasing the voltage really did the trick. Looks like I'm moving to the "maybe" camp with Todd, vagrant and co, and disregarding the 150mv reference point completely on the 15m. I appreciate everyone's help and input.
 
Back
Top