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Author Topic: 1.6L throttle sensor for data acquisition
Jeremy Lucas
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I've heard you can only tap into ECU TPS on the 1.8L cars. What inexpensive sensors have you guys found to use on the 1.6L for throttle position?

Does a rotary one fit on the throttle body shaft?
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Any other options?
Thanks

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Jeremy Lucas
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backusm Verified Driver Made Donation to Website Series Champ
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Wheeler put a nice one in my car. Uses a string pot on the cable, he just fabbed a bracket

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Mike Backus
90 SM white #94

Jeremy Lucas
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How much was the string pot?

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Jeremy Lucas
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I don't know. he put it in as part of a bunch of other work. I'm sure he or caddell can get you one.

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Mike Backus
90 SM white #94

David Luney Verified Driver
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<a href="http://www.victorylanedata.com/images/ThrottlePosition.jpg" target="_blank" style="text-decoration: underline">http://www.victorylanedata.com/images/ThrottlePosition.jpg</a>

$117.30

I have seen this used with string and a bracket on the throttle cable mount boss. I made a "L" bracket and mounted it in line with the throttle shaft and put a hex head bolt on the cable pulley to engage the sensor arm. The soft arm didn't like the hex head driving it so I covered it with plastic tube.

Phokaioglaukos Verified Driver
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Can you confirm that the 1.6Ls cannot feed throttle position to a data logger from the ECU?

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Chris

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The Victory Lane Data string pot unit works fantastically and is worth the cost for it's ease of use, durability and accuracy (although I recommend mounting the string end so it follows the top side of the throttle cable spool):


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I couldn't figure out how to use a rotary pot on the throttle shaft though I'm sure it could be done with enough effort.

The manual transmission 1.6L does not output analog throttle position although I believe it does output WOT and closed (don't quote me on that).

JD

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quote:
Originally posted by Phokaioglaukos:
Can you confirm that the 1.6Ls cannot feed throttle position to a data logger from the ECU?

Correct, the signal is binary.

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Jason Holland
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quote:
Originally posted by David Luney:
<a href="http://www.victorylanedata.com/images/ThrottlePosition.jpg" target="_blank" style="text-decoration: underline">http://www.victorylanedata.com/images/ThrottlePosition.jpg</a>

$117.30

Where did you see this price? Because that's an awesome price for that sensor. The page it comes from says 229.

J

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Jason Holland
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There are other ways to determine how much throttle your engine is seeting.... not as direct as a TPS, but perhaps as meaningful. Things your ECU is already looking at....

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Do I turn my 99 Hard S into a killerfast SM or seek a donor?

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I put a rotary pot on the throttle shaft by replacing the throttle spool nut with a custom piece made from hex stock. I turned it down and milled a flat on it to engage the pot. Then I fabricated a ridiculously complicated bracket to mount the thing to the throttle body.

Biggest problem I see with this (other than the required time, effort, and equipment) is that the sensor ends up sort of close to the charcoal canister. I can imagine scenarios in which the pot jams the throttle. Fortunately, all of these scenarios are post-impact so it probably isn't a real safety issue.

If I were to do it over, I'd use a string pot.

Scott

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Didn't know it wouldn't work on a 1.6.
Nice job with the stingpot!
You can pick up string pots cheap on EBay if you look around.

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Muda Motorsports
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Greg Bush Verified Driver
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You can get them cheap, but it takes some work to get the right connectors and get it right. Doable if you have the skill and patience, but even then I chose to save time and buy them ready to go.

The string pot is preferred because it is less likely to hang up the throttle, either open or shut.

Data is no good if you are in the pits or the tires.

Every time I see a pro racer go off with a stuck throttle I wonder if it was the TPS or a linkage problem... (Once in Trans-Am and once in SWC-GT last year)

Nigel Stu Verified Driver
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not directly throttle, but you can tap into the MAF door pretty easy.

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Ben Schaut
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quote:
Originally posted by Nigel Stu:
not directly throttle, but you can tap into the MAF door pretty easy.

bingo

--------------------
Do I turn my 99 Hard S into a killerfast SM or seek a donor?

JD Morris Verified Driver Made Donation to Website
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quote:
Originally posted by Kent Carter:
quote:
Originally posted by Nigel Stu:
not directly throttle, but you can tap into the MAF door pretty easy.

bingo
Really? I'd like to data log my IAT at the AFM but I am hesitant to have a spliced wire running to the loom on the most important sensor for performance in the entire car (AFM, not IAT). Worse yet, having a wire spliced into the loom in a low visibility location that became unhidden. Is there a way to make it explicit that you're not cheating when a wire runs from your AFM to a black box called your data logger? (I should add that I'm planning on using an external sensor, instead, primarily to avoid this issue)

JD

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quote:
Originally posted by JD Morris:
quote:
Originally posted by Kent Carter:
quote:
Originally posted by Nigel Stu:
not directly throttle, but you can tap into the MAF door pretty easy.

bingo
Really? I'd like to data log my IAT at the AFM but I am hesitant to have a spliced wire running to the loom on the most important sensor for performance in the entire car (AFM, not IAT). Worse yet, having a wire spliced into the loom in a low visibility location that became unhidden. Is there a way to make it explicit that you're not cheating when a wire runs from your AFM to a black box called your data logger? (I should add that I'm planning on using an external sensor, instead, primarily to avoid this issue)

JD

People trust me [Smile]

The sensor is labeled from the factory as a "0 - 12V Sensor", the wiring is obvious and it's out in the open were all can see. Instrumentation is not restricted, they have to prove it's a cheat.

I do think it's important to recognize that Mazda wired that particular sensor (the AFM) with shielded wire. That tells me a lot about it right there. I used a very short length of wire, very near the ECU to connect to the ADC.

By the way, there are those who have looked at 1.6L data extensively who are convinced that the ECU ignores the barn door when the throttle is wide open, perhaps only looking at the WOT switch and the RPM.

--------------------
Do I turn my 99 Hard S into a killerfast SM or seek a donor?

JD Morris Verified Driver Made Donation to Website
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quote:
Originally posted by Kent Carter:
By the way, there are those who have looked at 1.6L data extensively who are convinced that the ECU ignores the barn door when the throttle is wide open, perhaps only looking at the WOT switch and the RPM.

My non-extensive data indicates that changing the AFM clockspring position shows the same change in AFR on the dyno and on the track at WOT. That'd be hard to believe if the flapper door wasn't in the equation. However, I could be convinced that the ECU doesn't monitor the flapper door in closed loop at less than WOT since the feedback loop uses the O2 sensor.

quote:
Originally posted by Kent Carter:
People trust me.

Nice. Maybe you're right and I needn't worry about it. Do Miatas use an IAT multiplier on the fuel curves within the typical range?

JD

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quote:
Originally posted by JD Morris:
quote:
Originally posted by Kent Carter:
By the way, there are those who have looked at 1.6L data extensively who are convinced that the ECU ignores the barn door when the throttle is wide open, perhaps only looking at the WOT switch and the RPM.

My non-extensive data indicates that changing the AFM clockspring position shows the same change in AFR on the dyno and on the track at WOT. That'd be hard to believe if the flapper door wasn't in the equation. However, I could be convinced that the ECU doesn't monitor the flapper door in closed loop at less than WOT since the feedback loop uses the O2 sensor.

quote:
Originally posted by Kent Carter:
People trust me.

Nice. Maybe you're right and I needn't worry about it. Do Miatas use an IAT multiplier on the fuel curves within the typical range?

JD

Yes, I agree. I also think I see a change in overall WOT AFR's when I tinker with the clock spring. So the 'experts' may be wrong. Or it could be that there is enough noise in that to fool us.

Again, the guys who have played with the IAT signal say it has little effect except at the extremes. I haven't personally played with this.

--------------------
Do I turn my 99 Hard S into a killerfast SM or seek a donor?

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quote:
Originally posted by JD Morris:
quote:
Originally posted by Kent Carter:
quote:
Originally posted by Nigel Stu:
not directly throttle, but you can tap into the MAF door pretty easy.

bingo
Really? I'd like to data log my IAT at the AFM but I am hesitant to have a spliced wire running to the loom on the most important sensor for performance in the entire car (AFM, not IAT). Worse yet, having a wire spliced into the loom in a low visibility location that became unhidden. Is there a way to make it explicit that you're not cheating when a wire runs from your AFM to a black box called your data logger? (I should add that I'm planning on using an external sensor, instead, primarily to avoid this issue)

JD

Well, I tapped into the AFM signal at the AFM... not sure if that is good/bad but it was easy... (didn't know about the shielded cable for that, what are the potential side effects?)

then I ran the nice bright white single wire back into the cabin where I hooked up to my data. Actually tie-wrapped it to my wide-band O2 sensor wire. pretty simple and easy to see what the purpose of that wire is. nothing fancy, with everything hiding in plain sight.

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Ben Schaut
Schaut Speed Motorsports
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Ben,

THEORETICALLY, all kinds of bad things could happen and THEORETICALLY the way you wired it is all kinds of 'wrong'.

By using a single long wire that runs through the engine compartment tied to another long wire that runs through the engine compartment, you have potentially created a very good antenna. In the engine compartment you have a couple of very powerful transmitters of radio frequency noise: the alternator and the secondary side of the ignition system and a bunch of smaller transmitters like relays, fans, etc. Delivering those signals to the ECU imposed upon the signal from the AFM could confuse the ECU (or even damage it, but I think this unlikely). It's very meaningful that Mazda engineers choose to shield that signal wire.

One could write a textbook on how to wire a racecar and anyone who has ever installed high end car audio gear in high end cars can attest to the issues of noise management. Some rules:

1. Keep wires short as possible.
2. Keep signal wires away from power wires as power wires almost always have alternator 'whine' imposed on them.
3. Signal wires should either be shielded or a 'twisted pair' where the ground and signal wire are twisted together.
4. Shield braids should usually be grounded on only ONE end, but it can be hard to guess which end.
5. Noise falls off with the square of the radius so moving a signal wire just a few inches from a noise source can make a huge difference.
6. Whether to be careful about noise reduction depends on the signal you are trying to detect. On/off 12v (like the brake switch) can tolerate a lot of noise whereas the AFM flap or even the signal from an oil pressure sender may need some consideration of noise. Wheel speed sensors can be excruciatingly sensitive to noise.

This could grow into a huge thread, but I think some of our resident engineers could really provide some pearls!!

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Do I turn my 99 Hard S into a killerfast SM or seek a donor?

   

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