Linearity Question For Auto Nerds - This is gonna get technical


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Linearity Question For Auto Nerds - This is gonna get technical

Post by waituntilthebeep » Fri Dec 02, 2016 9:35 am



I am a Diesel Nerd. That is my career path and craft. I need some information from some Auto and Electronic Nerds... the peeps that take technical information to a personal and 3 E'd Geeek level... all to get really deep in my Wing.

What I am looking for is a technical description or breakdown of the throttle position sensor in response to throttle action. What I have going on (and I know Mother Honda is going to tell me to screw right off if I even ask because it will never be a warrantable condition) is a pretty ridiculous inconsistency in throttle response. I would expect the throttle response to be like most other automobiles I have driven recently that are 5 years or younger in age and that is when you press the accel pedal, you get a relatively linear throttle response. Slight increases give a slight increase in throttle. On my Wingding, I start to roll on the throttle and I get a start to acceleration. Right about the rotation position where I would normally be cruising down the road, aka. the place where my throttle spends 95% of it's life, I get a flat response with no increase or decrease of power. Add 1 more degree of rotation to the throttle and it either stumbles a tiny bit or just goes like hell. If I simply throttle THROUGH that point, I don't notice the "bump" in performance but I am also rolling on it pretty hard and when the roads are wet, we gets a bit squirrely if you are following my thinkin. Rolling through that glitch while in a corner, in a lower gear and lower road speed is at times truly a gift to be experienced only if you carry spare undies. I love the power that my 1800 has but wheel slip is not a good thing at 40 miles an hour and 20% or better bank angle.

It is not 100% repeatable and there is no way someone that doesn't ride this thing on a daily is going to notice it. So, with all that said, the question is thus: Is the throttle position sensor a basically linear device prone to issues such as an old rheostat where it can have goofy spots? I don't have a scope or I would answer that question on my own by simply mapping my TPS. OR... and a big OR it is... OR, are there other interactions that could cause this micro-glitch such as O2 sensor (no check engine lights BTW), dirty intake butterfly, venture or what not that could be causing it? I am seeking an "When A is opened, B responds by adding fuel at % rate and C reads that output and advances/retards to bladdadeebla whatever" kinda explanation. Textbook nerdgasm kind of stuff, eh?

Anyone out there in Wing world with that kind of time and brain power to spare in the automotive field? We use the same types of components in diesel application now but we lack some of the emission controls used in the auto world. We have emission controls, just applied differently. Warm up your thinking cat (not autocorrect) and help me if you can.



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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by dadztoy » Fri Dec 02, 2016 11:15 am

Well, I'm not an auto mechanic but I do have over 50 years of electronic experience... In the world of electronics, potentiometers (TPS') have 3 basic tapers... Linear, Log, (logarithmic) and reverse log... I would expect the TPS on most machines to be linear, but this would depend on how the software was written for the ECM...

Just a guess on my part, but because you say it's not repeatable, I expect you are running into corrections generated from the ECM, rather than a failure from the TPS... Of course, there is always the possibility of a worn or otherwise defective TPS... I have never noticed that on my bike and I am pretty well attuned to my machines, but you must be even more atuned to yours...

Les

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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by FM-USA » Fri Dec 02, 2016 11:19 am

I'm your basic Shade Tree mechanic guru.
I've only changed a few TPS because they were simply not working.
Does the shaft wiggle by fingers?

Before disassembly, you can try a spray Electrical Cleaner with compressed air a couple times.

IF I remember correctly, they're not a sealed unit tho you'd have to drill out a plastic weld.
The resistance can be tested with an Ohm meter, preferably the VDO type where you'd see a jump in the needle.

Hopefully this post will spark interest.

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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by dingdong » Sat Dec 03, 2016 9:07 am

Waituntilthebeep. I hope you find a solution for this problem. I have a Honda Rune (1800 FI engine) that has the same problem but to the extreme. Even to the point of surging on a rough road, even in 5th gear. Riding through a rough corner in lower gears, oh my! If you come up with anything I would appreciate a heads up. There is a company that has developed a modified throttle that is supposed to help the problem but they don't have one for the Rune. If I remember correctly they may have one for the earlier 1800. Good luck keep us informed.

You might want to read their information regarding the product.
http://www.g2ergo.com/store/g2-street-t ... ttle-tube/
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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by Steve F » Sat Dec 03, 2016 7:35 pm

Perhaps you might want to start with and ECM reset. I don't have the procedure here, but it shouldn't be too hard to find.
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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by waituntilthebeep » Sun Dec 04, 2016 12:04 am

I think I stepped into the 4 E'd geeeek territory with my research. Holy crap. Just goes to show that you can find out pretty much anything on YouTube if you dig long enough. I think I have a direction to start testing now... when I get time to strip the girl to her undies to have access to everything. The baisc answer to my very own question is, Yes, the TPS operates in a linear fashion as it IS a potentiometer in it's simplest form. The things that act in concert with it are varying but involves intake air temperature, engine temperature and O2 sensor readings. The ECM mulls through all that data to maintain and modify the proper fuel ratio every quarter bazillionth of a second and adapts on the fly. I knew this actually, but wasn't sure in detail how it was interconnected - only had a vague idea anyway.

In my case, the issue that I have... a flat spot or inconsistent throttle curve at one very specific spot in the throttle rotation... is indicative of a bad spot in the TPS. Testing this is relatively simple with a DVOM but better tested in detail with a scope. However, if there is a dead spot in the TPS, it is a simple process to resolve. I need to do some more data collection and narrow down details like if it happens differently st different ambient or engine temperatures. My guess is that it is not temperature sensitive. We shall see. I will update when I get to detailed testing.

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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by waituntilthebeep » Sun Dec 04, 2016 12:20 am

dingdong wrote:Waituntilthebeep. I hope you find a solution for this problem. I have a Honda Rune (1800 FI engine) that has the same problem but to the extreme. Even to the point of surging on a rough road, even in 5th gear. Riding through a rough corner in lower gears, oh my! If you come up with anything I would appreciate a heads up.
That sounds a lot to me like your issue is not with fuel mapping but with throttle response. Have you confirmed that your throttle cables are tight in both directions with the throttle butterfly? Being as our bikes have pull up AND down cables so that we have positive movement in either direction, it is very possible to have a tiny bit of slop between the cables and the cam on the throttle valve shaft. Slop means that the grip doesn't have to move but the butterfly position (and TPS) can jump around within the confines of the cables. ALSO, I don't know if the Rune has a spring on the throttle valve shaft or cam. I would assume so. If the throttle butterfly can bounce at all, like on bumpy roads, then your TPS will show the ECM that and you will get wild fuel mapping and response. These 1800 engines are beasts when it comes to power and it doesn't take much of that power to make things miserable. It is also possible that your TPS sensor is not properly calibrated/clocked.

I say this for one reason: If the TPS says the throttle is at 5% open when it is not, the bike will run lean and the o2 sensor will enrich it out to compensate. An increase in the throttle will produce a much higher o2 rate and the ecm will compensate but because it happens so fast and repeatedly there can be an oscillating effect in fuel response and that would also cause jitter or coughing. I used to screw with carb'd engines years ago and the same thing could happen with dirty carbs but EFI is not the same because of the computer being so fast. I am learning that system in detail now.

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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by FM-USA » Sun Dec 04, 2016 7:36 am

Is the lag at the point where the throttle would kick in the secondaries? (as in a 4 bbl carb)

I have not dug DEEP into the 1500's 'how's and whats' they work.
Maybe the problem is mechanical at the carburetor.
Possibly a crack at the end of a vac line.
Mouse chew hole in a vac line.
Cucaracha's? :shock: (joke'n)
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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by Steve F » Sun Dec 04, 2016 2:47 pm

FM-USA wrote:Is the lag at the point where the throttle would kick in the secondaries? (as in a 4 bbl carb)

I have not dug DEEP into the 1500's 'how's and whats' they work.
Maybe the problem is mechanical at the carburetor.
Possibly a crack at the end of a vac line.
Mouse chew hole in a vac line.
Cucaracha's? :shock: (joke'n)
Secondaries? Haven't heard that term used when talking about fuel injection........not a carburetor in the 1800 :roll:
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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by FM-USA » Sun Dec 04, 2016 4:20 pm

1800?.. .. woops.

Still there's a system that produces power like secondaries.
I COULD BE WRONG, never toyed with FI, so EZ on the whip.

What about the other ideas?
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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by waituntilthebeep » Sun Dec 04, 2016 7:18 pm

FM -
This is an 1800 EFI thing. I know about the 1500 issues. I had an 89 that I got rid of because I could never fix the lag. This is just a weak sot in the throttle curve. Weak enough to give an unsettling throttle bump when you pass through it.

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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by FM-USA » Sun Dec 04, 2016 7:35 pm

Is that weak spot the same place as in RPM (any gear) for say at 2800 RPMs.
Or is it different places in the RPMs for each gear.

Pardon me for the odd questions, but I'm learning and diagnosing at the same time. :shock:
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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by waituntilthebeep » Sun Dec 04, 2016 8:10 pm

FM-USA wrote:Is that weak spot the same place as in RPM (any gear) for say at 2800 RPMs.
Or is it different places in the RPMs for each gear.

Pardon me for the odd questions, but I'm learning and diagnosing at the same time. :shock:
That is what points me towards the TPS... It is basically in the same place all the time. It is right around 2500-3000 rpm. That is where I normally cruise down the freeway at - relates to about 65-70mph - and I spend most of my time like that so it would be easy to have a worn spot in the TPS coil.

For your understanding... I like to keep my nerdliness well oiled... Rolling the throttle to the place where it gets hinky gets the same basic response. I can feel the bike pull or putting torque to the ground, then as I continue to gently twist, I can feel the torque slack off just like you were lifting your foot off the accel pedal slightly in a car. This is all while I am still giving more grip rotation. IF I STOP THERE, the torque doesn't return but stays flatlined and after a second (literally) the bike will either gasp like it misfired on one or 2 cyinders then recovers and puts the torque back to the road OR it will REALLY put the torque to the road kind of like you had continued to roll on it and had passed the bad spot. Either of those two responses could be that the ECM loses a real time signal and then just guesses or assumes throttle position until either the lag or the surge causes the throttle to actually go either direction and clear the bad spot. I don't believe that there are any codes being activated because there are no lights. Just a weird curve that didn't exist when it was new. The curve was actually smooth as glass when I bought it.

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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by FM-USA » Sun Dec 04, 2016 9:45 pm

If those are the TPS, why would there be 2?
One is riveted in the other screwed.
I'm sure the far right is the TPS. Never seen one 90 degree to the shaft. Mass air flow sensor?


I scanned Partzilla for TPS listing, NONE!???

Also, it looks like a run of the mill TPS you find on cars and a few other makes of bikes.

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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by waituntilthebeep » Sun Dec 04, 2016 11:46 pm

Ya got me. I haven't even looked at a parts breakdown or anything on these. Honestly, never even pulled any of the panels off the thing to look closer. I am needing to do so as I am at 40k and haven't done anything but change the oil and check the plugs. My next step is to change them and get after further troubleshooting. Figured to do the research before I travel down that path. Like I was saying, I am basically familiar with the operations of most of the equipment on the Bird but not all of it. Never really paid enough attention to gasoline stuff when I went through school. That was years ago too. No better time than the present, right?

My guess though is that the TPS (regardless of what they call it) is on the end of the throttle shaft. The one in the middle is possibly MAF, but outside of that, I don't know. I will look and see if my manual says anything.

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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by waituntilthebeep » Mon Dec 05, 2016 12:07 am

This is what the manual says... Throttle Position Sensor, Intake Air Control and Manifold Absolute Pressure sensors are on the throttle body... which makes sense.



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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by FM-USA » Mon Dec 05, 2016 12:07 am

I skim read through a Yamaha forum and Kaw, found the TPS wearing out at a certain point is a regular occurrence.
Also reading the contact arms become weak through the heat/cooling cycles.
i never took one apart but I see someone cut one open. WOW a rather YUGE spring in thar.

I'd surmise with you one your running at that constant RPM wore down the carbon pile to the point of no contact.
Or possibly the case wore enough to loose contact with worn carbon race.
Either way, I be speculating.

AHHhhh, PIX'turs. Looks like my assumption of the MAF was correct. ;)
________________________

Looks like there was a run of poorly made TPS. Bikes, cars and some light trucks were having issues similar to your complaint.
It looks like Yamaha had a secret recall bulletin and since been fixed with an updated model.
Most of this round of skim reading the weak contact arms were the cause, while others were gummed up insides.

LIVE AND LEARN. ;)
Internet makes it quite a bit faster.

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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by Steve F » Mon Dec 05, 2016 7:38 am

Interesting to note in the picture, they call it a "M-A-P" sensor, not a "M-A-F" (MAP stands for Manifold Absolute Pressure) which is why it is where it is.
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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by FM-USA » Mon Dec 05, 2016 9:35 am

Looks like I need new glasses.
At times P & F look the same, as does O & Q, as does v & ^.
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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by dadztoy » Mon Dec 05, 2016 12:21 pm

Going on the assumption that it could be fuel mapping, you could always send your ECM to Guhl Motors and have it re-flashed... Suppose to do wonders for the GL1800 performance...

http://www.guhlmotors.com/

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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by ct1500 » Sun Dec 11, 2016 5:45 pm

MAF is mass air flow and IAC is better known as idle air control.
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Re: Linearity Question For Auto Nerds - This is gonna get technical

Post by pixel288 » Tue May 23, 2017 11:23 pm

MAP= manifold absolute pressure; simply 'reads' the vacuum of the intake tract to allow the computer to more accurately assess how much work the engine is doing/turning. Usually a bullet proof sensor only needing replacement at high mileage, or if defective as shown by throwing a code.
MAF=Mass Airflow Sensor; works by heating a platinum wire and sensing the resistance across it. Works really well, similar to the MAP, but MUCH more sensitive to damage from cleaners, moisture, etc. a huge PITA when they act up.

Just a little geekyness. With only 2 e's. Dealt with both types on cars and trucks. I prefer the MAP sensors any day.

Phil



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