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Discussion Starter #1 (Edited)
Boosted folks:

There has been a lot of talk on replacing the Electronic Drive-by-Wire throttle system in the IS300 in favor of a manual system which gives you direct control over the throttle valve with the pedal.

We've heard all sorts of reasons... from things we can easily see (No more annoying TRAC control!) to other "observations" that we haven't neccessarily recorded, quantified, or proven (If I get rid of DBW I get better throttle response!)

I am working on recording and analyzing data on the speed of DBW, but I don't have an answer to all the questions yet.



I do, however, want you to take a look at the VIDEO of my 80mm throttle body upgrade in this thread... and tell me:

After watching the video, do you still think DBW is causing poor throttle response?



When I get down to measuring exact reaction latency between pedal input and throttle movement... do you think it's going to be something you can actually feel? Or... have a lot of people been influenced by a pretty large placebo effect? I want to see what evryone thinks... and how that view changes when we've got actual, recorded data to look at.
 

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Mr. Negative
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thanks for posting this here, you read my mind as I was going to do this and link to your posts.
 

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I'm thinking our EXTREMELY long intake path has something to do with it. because the intake manifold wraps completely around the block i'd wonder what kind of diff there would be with it on the other side feeding a straight line to the intake.
 

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Traction control should only be a fuse, just like on the supras, so you pull the fuse and there is no more electronic throttle plate closing on us.
A Drive By Wire setup or DBW, has two potentiometers (or throttle position sensors) on the pedal that sends two different voltage to the ECM - Combined signals allow the ECM to calculate a mean voltage output from the two signals, and therefore open the throttle plate by the amount the pedal has moved.
Better throttle response, could mean finding a better set of potentiometer, that reads more of the pedal motion, and therefore sends more accurate data to the ECM? Instead of going back to the old cable ;)

my .2cents...
 
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Discussion Starter #8
TeckniX said:
Traction control should only be a fuse, just like on the supras, so you pull the fuse and there is no more electronic throttle plate closing on us.
A Drive By Wire setup or DBW, has two potentiometers (or throttle position sensors) on the pedal that sends two different voltage to the ECM - Combined signals allow the ECM to calculate a mean voltage output from the two signals, and therefore open the throttle plate by the amount the pedal has moved.
Better throttle response, could mean finding a better set of potentiometer, that reads more of the pedal motion, and therefore sends more accurate data to the ECM? Instead of going back to the old cable ;)

my .2cents...
Excellent info... did you happen to make it over to Part 1 of that article, where I was explaining how DBW worked?

The Lexus DBW system doesn't quite operate as you've described, since it's a hybrid DBW/cable control system.

Can you provide us with any insight as to why 2 sensors are used on the same input? Or are you talking the difference between the TCPS and TPS?
 

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IceCold4x4 said:
I'm thinking our EXTREMELY long intake path has something to do with it. because the intake manifold wraps completely around the block i'd wonder what kind of diff there would be with it on the other side feeding a straight line to the intake.
Quick input on this comment. Extremely long intake tracts are good for low-end torque. If you look at any car with a variable intake/dual intake/tripple intake etc etc etc... you will notice that the general way of generating low-end torque is by using the longest pathway. As the RPM rises, the shorter path/tract is used to generate more peak torque.

So no I do not think our intake tract length has much to do with low throttle response. Infact I am willing to bet that if the intake tract was reduced in length, the throttle response will be reduced further
 

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dasgalloway said:
Excellent info... did you happen to make it over to Part 1 of that article, where I was explaining how DBW worked?

The Lexus DBW system doesn't quite operate as you've described, since it's a hybrid DBW/cable control system.

Can you provide us with any insight as to why 2 sensors are used on the same input? Or are you talking the difference between the TCPS and TPS?
I actually thought the part I was just a video so I'm sorry for the 'false' repost :(
The 2 different voltages are a conventional increasing voltage, as the pedal is being depressed, and the other one is a lower voltage, with less of an amplitude difference between a depressed and non-depressed pedal - This allows the pedal position to be calculated with greater accuracy than when only a single voltage output is taken into consideration. But as you mentioned this is more of a general how DBW works, and I have no insights as to how the Lexus one is opperated. I shall read on ;)
 

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Discussion Starter #12
TeckniX said:
I actually thought the part I was just a video so I'm sorry for the 'false' repost :(
The 2 different voltages are a conventional increasing voltage, as the pedal is being depressed, and the other one is a lower voltage, with less of an amplitude difference between a depressed and non-depressed pedal - This allows the pedal position to be calculated with greater accuracy than when only a single voltage output is taken into consideration. But as you mentioned this is more of a general how DBW works, and I have no insights as to how the Lexus one is opperated. I shall read on ;)

I do know that both TCPS and TPS output two voltages, I will record tonight and post up so we can try to figure out whats going on.
 

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kponti said:
Quick input on this comment. Extremely long intake tracts are good for low-end torque. If you look at any car with a variable intake/dual intake/tripple intake etc etc etc... you will notice that the general way of generating low-end torque is by using the longest pathway. As the RPM rises, the shorter path/tract is used to generate more peak torque.

So no I do not think our intake tract length has much to do with low throttle response. Infact I am willing to bet that if the intake tract was reduced in length, the throttle response will be reduced further
Eh not sure on this Kponti, Think of what a single plane high rise intake does on a good old v-8 decreases low end response for upper end power while a lowrise dual plane is used for lower end torque. Same goes with throttle body spacers.
 

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I hope this can contribute a little to this post. But have you guys done the throttle cable "damper" modification? This seems like a low-tech type of thing, but part of our throttle response issue is definatley falling on the actual pedal/cable design. I removed some of the slack in my throttle cable, as well and it feels very direct.

I don't know how bad the reaction time between the pedal, sensor-network, and stepper motor is, but would it be perceptable to a human?
 

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Discussion Starter #15
TeckniX said:
A quick reading pdf that I need to save on here for me to read later ;)
http://www.autoshop101.com/forms/h33.pdf
Very good PDF for understanding how the sensors themselves work, explaining the details (in technical terms) of what I was doing a layman's description of in the other thread.

It does say that it outputs two voltages, and one of the things it does is compare them to detect problems.

Reading that almost felt like cheating... :blush: it told me what I was going to see tonigh when I recorded voltages. Bah! lol
Good link though... whats that from? Some sort of training manual I'd guess, it has a quiz at the end.
 

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Discussion Starter #16
Hyper-z said:
I hope this can contribute a little to this post. But have you guys done the throttle cable "damper" modification? This seems like a low-tech type of thing, but part of our throttle response issue is definatley falling on the actual pedal/cable design. I removed some of the slack in my throttle cable, as well and it feels very direct.

I don't know how bad the reaction time between the pedal, sensor-network, and stepper motor is, but would it be perceptable to a human?

No, we'll get to the in the future. Limiting variables as we test. Once we've identified all the independant parts and understand whats going on and exactly what is affecting throttle response, we'll zero in and look for ways to make each function better.
 

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Mr. Negative
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you guys understand what this post is about right? he's saying this "poor" throttle response is Bunk as far as the TB/DBW is concerned.. showing that the plate swings as fast as you can move your foot and has no delay.
 

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Discussion Starter #18
IS_Dude said:
you guys understand what this post is about right? he's saying this "poor" throttle response is Bunk as far as the TB/DBW is concerned.. showing that the plate swings as fast as you can move your foot and has no delay.

Maybe not completely bunk... but I am contemplating that it seems DBW plays a very small part in any poor throttle response... and therefore going to a straight cable system doesn't get you much other than placebo effect and lost functionality.
 

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i dont feel any problems with throttle response when flooring it or letting off the throttle. My problem with it is Blipping, revmatching is more difficult to do because it seems u have to push the pedal in slightly before the engine reacts. Like just stitting there at idle and revving the car. you've already pushed the pedal and inch or so and the engine is still not revving....same problem with blipping the throttle to do down shift.
Even in your video Das with the ignition on you can see, if you watch closely, throughout the initial response the plate is just a hair behind the throttle.
 

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Mad props 2 Das with all his efforts to make life easier 4 us through his R & D. Last we met was at the Morikami meet when u installed the Team Lexus exhaust n that sh_t screamed like no tomorrow. Keep up the good work
 
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