2GR Camry sensitive accel pedal - Page 2 - MR2 Owners Club Message Board
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post #21 of 81 (permalink) Old December 12th, 2018, 13:21
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Originally Posted by ddimensia View Post
I'm hoping to setup a circuit to support auto-blip and throttle cut for a paddle shifter, maybe I'll adjust the throttle output under normal operation at the same time.
I have this contraption that I will be installing when I get a chance.
https://www.auto-blip.com/
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post #22 of 81 (permalink) Old March 22nd, 2019, 07:09 Thread Starter
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I picked up a used Pedal Commander (PC27) on Ebay. I set it on economy mode and it works great. I tried comparing the two with my scanner using the graph and it looks like it only effects below 60% opening.
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post #23 of 81 (permalink) Old March 22nd, 2019, 12:56
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This has got me thinking again about a simple circuit to reduce the dead zone at the top of the pedal. Please double check my thinking here:

1. I have data logged pedal vs throttle position, and found that the top ~23% of the pedal doesn't do anything. This is true both with the engine off AND under load in my experience.
1a. If we can reduce the voltage output of the pedal by ~20%, then the entire pedal range would more closely map to the throttle range.

2. The pedal has two separate circuits, each consisting being a supply (5v), a ground, and an output voltage that varies with throttle position. I have tapped into one of these to record pedal position with my data logger.
2b. If I built a pair of simple voltage dividers between the output and the ground using a 2k ohm resistor and a 10k ohm resistor, this should provide a ~17% reduction in pedal output voltage.
2c. Since it's a percentage reduction, zero will still be zero, 20% > 16.6%, 50% > 41.5% > 100% > 83%. IE, a nice linear reduction in sensitivity. Since previously I saw that 77% pedal > 100% throttle, it should now be closer to 90% pedal > 100% throttle (77 x 1.17 = 90)

I know there isn't any way to know for sure if this works but to try it, but does the theory seem sound? Should I use relatively high resistance values like 2k and 10k, or would lower values be better (for example 200 / 1000). My gut feeling is that higher resistances will result in less current flow, which will be better for all parts involved. Don't want to damage the pedal, or worse the ECU.

I suppose if I'm going to do this I may as well use a dual potentiometer so I can dial in exactly the reduction I want, rather than making a fixed voltage divider...


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Last edited by Alex W; March 22nd, 2019 at 13:17.
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post #24 of 81 (permalink) Old March 22nd, 2019, 13:22
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The voltage divider plan isn't invalid. but before you do any of that i suggest you do logging at 4700-4800 RPM. I think the throttle pedal travel is almost fully used at that point. I don't know the full ECU workings on this but i don't think load has anything to do with it. just pedal position and RPM and possibly speed but i only think there's a small chance speed works into it.
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post #25 of 81 (permalink) Old March 22nd, 2019, 13:42
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I did some testing of that last summer. I will have to double check my data, but from what I remember that top ~20% didn't appear to be used under any conditions. But it might be tough to know that for certain with the data I have. What I remember was logging a 2nd gear pull, and then comparing pedal position (from Torque) to throttle position (logged directly from the throttle body via my data logger). But the tricky thing is, just because I saw the throttle fully open at 80% pedal at the start of the pull doesn't mean that 100% pedal isn't required to keep it open at the end of the pull. I suppose to test that I need to start at 0 throttle at 5k rpm and then roll on to full throttle and see if the relationship holds.


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post #26 of 81 (permalink) Old March 22nd, 2019, 13:58
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I just looked up the table again and i should have said 4400RPM. the reason i ask is because i really think this is the throttle table. note that there's no horizontal axis values because i don't know how exactly to interpret the values there but i think it's relatively close to 0% throttle on the left and 100% throttle on the right. This table i think is in throttle blade angle degrees and 86degrees is the max for this motor.



so if you clip off the top of the pedal travel you may have an issue at 4400RPM where the throttle closes a bit.
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post #27 of 81 (permalink) Old March 22nd, 2019, 14:06
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Interesting. I see what you mean, that area right at 4000-4400 is where it might be effected.

But this still doesn't make sense... Looking at the 0 RPM row, one would expect the blade to open very slowly over the first 60% of the pedal travel, and then suddenly snap open. But it doesn't do that, it's actually a pretty linear relationship. Now, there may be other factors going on in terms of load or torque demand or whatever factoring into the horizontal value on that table, but I don't think it's possible for it to be straight pedal position, or even anything close to that.

I posted this in another thread a while back, but here it is again:

https://youtu.be/rs88I8WRSqA?t=8


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post #28 of 81 (permalink) Old March 22nd, 2019, 14:11
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The video is easy to explain. the ECU does seem to have a tech diagnosing mode for the throttle pedal when the engine is not running and the pedal gets connected more or less 1:1 throttle body. This is important to check functionality so it makes sense.

and yes, the input into this table is not something i fully understand. i think it's some kind of internal torque request and that isn't 1:1 with the pedal position but it should be relatively close.

all i suggest you do is check that 4000-4400RPM carefully before you implement your suggestion otherwise you may cause yourself a torque dip.
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post #29 of 81 (permalink) Old March 22nd, 2019, 14:17
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Is it possible that not having the automatic transmission inputs locks it into that 1:1 diagnosis mode?

Because I do remember it looking very much the same (linear up to 80% pedal) in the data logs when I rolled on at 2500 or so in my testing last summer.


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post #30 of 81 (permalink) Old March 22nd, 2019, 14:24
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That's certainly possible. I know i've tried to modify these and other tables to change the throttle behaviour and it does change it but not quite in the ways i would expect which is why i left it alone. I haven't tried it on the 2AR-FE. that's a manual transmission ECU and it could answer some of our questions here.
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post #31 of 81 (permalink) Old March 22nd, 2019, 16:46
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This remains as a very interesting question. In UZ swaps a properly designed A/T emulator allows a dyno-measured gain of about 50HP on a factory ECU. [The pinouts of the ECU are very similar to RAV4 for trans control]. Without the emulator the throttle is limited. I'm doing more research into this and will report any interesting findings or developments.

PS. There's also some very interesting tables in the binary that [seem to] have the structure of Gear (0,1,2,3,4,5) versus RPM [sorry I said load earlier]. I've tentatively labeled them as shift point maps. I believe that OV does something with these to increase torque output in a/t vehicles. THIS IS SPECULATION.

PPS. Interesting question is: does 2AR M/T binary have similar "shift point" tables or not. This would give some idea of their function. I don't know if anyone is willing to post a original 2AR binary for purpose of "study."
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post #32 of 81 (permalink) Old March 23rd, 2019, 18:17
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I just rechecked the pedal position vs throttle position, and I am getting exactly the same results at 4000 RPM as with the engine off. Throttle fully open with the pedal at 75% and the last 25% of the pedal travel not doing anything.

I have a 10k dual channel linear pot on the way, here's hoping it works!


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post #33 of 81 (permalink) Old March 23rd, 2019, 19:01
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Quote:
Originally Posted by Alex W View Post
...Should I use relatively high resistance values like 2k and 10k, or would lower values be better (for example 200 / 1000). My gut feeling is that higher resistances will result in less current flow, which will be better for all parts involved. Don't want to damage the pedal, or worse the ECU...
You need to consider the impedance of both the pedal sensor and the ECU input. If the divider resistance is much higher than the sensor impedance and much lower than the ECU impedance, then it will work exactly as you intend. For example, if the sensor potentiometer is 10k and the ECU input is 1M, then a 100k divider will pretty much do what you want. Otherwise, you would need to account for loading in your design. You don't need to worry about the ECU here, but you could potentially burn out the pedal sensor by overloading it.
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post #34 of 81 (permalink) Old March 23rd, 2019, 20:47
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The 2AR-FE binary has many many differences, the strategy seems to be different even in the stuff that is in common on both ECUs. I think most of it is just an evolution. There are so many maps in here that i have no idea what they do that it's hard to tell what is missing and what isn't.

Alex, on the pedal travel something just occurred to me. has anyone checked what the travel is on the stock application? is it possible it hits the carpet before actually traveling the whole way and the calibration makes up for this?
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post #35 of 81 (permalink) Old March 23rd, 2019, 21:12
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I have a stock 2007 Camry and would be willing to log pedal, TPS, et cetera, but don't know if anything in that ECU/Pedal would be relevant to any other.
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post #36 of 81 (permalink) Old March 24th, 2019, 07:49
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Originally Posted by Gouky View Post
Alex, on the pedal travel something just occurred to me. has anyone checked what the travel is on the stock application? is it possible it hits the carpet before actually traveling the whole way and the calibration makes up for this?
Could be. Also could be that not all pedals are calibrated the same... Maybe using a Camry pedal on a Rav4 ECU causes this behavior? Just speculating.

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Originally Posted by merryfrankster View Post
I have a stock 2007 Camry and would be willing to log pedal, TPS, et cetera, but don't know if anything in that ECU/Pedal would be relevant to any other.
Certainly wouldn't hurt. I am logging "Pedal Position D" (E should work as well), and "Throttle Position (Manifold)". Would be interesting to see if this behavior exists with the automatic transmission.


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post #37 of 81 (permalink) Old March 24th, 2019, 13:24
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You need to consider the impedance of both the pedal sensor and the ECU input. If the divider resistance is much higher than the sensor impedance and much lower than the ECU impedance, then it will work exactly as you intend. For example, if the sensor potentiometer is 10k and the ECU input is 1M, then a 100k divider will pretty much do what you want. Otherwise, you would need to account for loading in your design. You don't need to worry about the ECU here, but you could potentially burn out the pedal sensor by overloading it.
The pedal measures ~330 ohm from the voltage input to the voltage output, and the ECU measures 38k ohm across the input (input to ground). 10k for the divider seem reasonable?


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post #38 of 81 (permalink) Old March 24th, 2019, 15:09
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I am logging "Pedal Position D" (E should work as well), and "Throttle Position (Manifold)". Would be interesting to see if this behavior exists with the automatic transmission.
Alex, just for consistency, what are you using for your logging? Torque Pro, or Techstream, or... something else? I can try to do the same.

As an aside, there are a few things that the RAV4 and Highlander ECU's do to monitor the behavior of the U151 A/T that could possibly maybe affect the behavior of the throttle, and this could possibly be relevant to this discussion so I'll share some of my ideas and questions on this which I do not have any definitive conclusions yet.

These are a few things we know from reading the repair manual for any of the vehicles equipped with 5-speed U151E or F which includes Rav4, Sienna, Higlander, RX350.

The ECU compares the engine speed NE to the turbine speed NT to determine the status of torque converter lockup and sets an error condition if this is not consistent with the status of the lockup solenoid DSL.

The ECU compares the output shaft/counter speed NC to the turbine speed NT to determine the gear selection status and sets an error condition if this is not consistent with the shift solenoid settings.

The ECU monitors the electrical status of the shift and pressure solenoids SLT SL1 SL2 SL3 S4 SR DSL that it controls directly and sets an error condition if it finds an electrical fault in any solenoid.

The ECU even monitors the transmission oil temperature on THO and can set error conditions based on this signal.

In brief there are a number of error conditions "circuit" conditions and "performance" conditions that can be set by the ECU based on the behavior and status of the trans.

We do know that the MIL for these error conditions is removed in our hacked ECU's - which is a great thing because it gives us a usefully functional CEL. I don't know the mechanism of how this is done because I don't know the underlying logic so I don't know if the error condition checking and setting is deleted entirely or just the MIL setting. Beyond this, we do not know what consequences these error conditions may have for engine control. It's been theorized that without transmission input the engine defaults to a engine-stand dyno test mode that is not affected by transmission status however we also know that in our running cars the presence or absence of a speed signal from the transmission does have an effect on the throttle behavior as can the selection of N versus D for shifter status, so the question is not straightforward to answer.

As a point of comparison, we do know that in the Camry ECU the loss of communication with the external TCU of the U660 has serious consequences for engine control, and these directly affect the throttle behavior. So therefore it is not unreasonable to investigate the possibility that there may be consequences from loss of communication with the transmission for the RAV4 and Highlander U151 that would affect the throttle behavior.

What I'm suggesting is that the study of the behavior of the throttle may benefit from some input from the study of the effect of the transmission behavior if any which I don't think there is yet any conclusive answer on what is going on with that - but it should be possible to find out which I am trying to do by gathering info and ideas on this leading to some tests possibly that will help in figuring it out.
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post #39 of 81 (permalink) Old March 24th, 2019, 16:38
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The pedal measures ~330 ohm from the voltage input to the voltage output, and the ECU measures 38k ohm across the input (input to ground). 10k for the divider seem reasonable?
Sounds good to me, and I see no risk in trying it.
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post #40 of 81 (permalink) Old March 24th, 2019, 16:45
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Alex, just for consistency, what are you using for your logging? Torque Pro, or Techstream, or... something else? I can try to do the same.
Torque Pro, with a OBD Link LX (much faster logging than the cheaper tools): https://www.amazon.com/ScanTool-OBDL...omotive&sr=1-7

In theory the logging equipment shouldn't matter, other than the refresh rate being important for capturing transient behavior. Also, I have found that enabling "synchronous logging" makes the data much more useful.

There are definitely a lot of transmission control things going on (or maybe, not going on, depending on how the ECU reacts to the transmission being AWOL. I *think* that the hacked ECU simply turns off the error code and therefore the CEL but does not modify the underlying programing
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