Rev matching down shifts on an automatic? (How does the ISF do it?)
01-31-17, 01:30 PM
#1
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Rev matching down shifts on an automatic? (How does the ISF do it?)
So this question has been troubling me for a while now and it has to concern how the ISF is able to downshift and revmatch a conventional automatic. I have a theories of how it could possibly be done but I wanted to confirm and to see if anyone else knows.
First off I watched a video (here is said video
) and this is on the AA80E that is in the ISF. After watching many other videos on different transmissions (like the A340E and A650E to be specific) and even some powerglides, all of these transmissions have torque converters, valvebodies, solenoids, plantary gear sets and clutch packs so why is it that this transmission can revmatch?
What I want to know specifically is how the transmission components move, what are the solenoids doing (all of them), how does the lockup function on gears 2 through 8 work with the revmatching?
Here is the theory:
First key component is the fly-by-wire. The throttle valve can move independently from the gas pedal. This could receive an electrical signal to blip the throttle when you want to downshift even though you are on the brake pedal getting ready to turn in. Now the lockup converter can be locked for gears 2 through 8 (this part is confirmed) but does it unlock during the downshifts while rev matching? The second key component I believe is the transmission tune that controls the solenoids and how it controls the solenoids. SO if you have the line pressure solenoid up in pressure but the clutch hydraulic solenoids not sending the fluid to the appropriate clutch packs to engage the gear (assuming no other clutch packs are engaged either) that would render the transmission in neutral. Now the shift solenoids to my understanding just uncover or cover passage ways to the clutch packs that will engage the clutch packs to the proper gear or gear you have selected. Therefore the shift solenoids will have the gear selected, the line pressure can be high and the clutch hydraulic solenoid could be set to not send the fluid to the clutch packs and the transmission is still in neutral. At this point the lockup converter can stay locked no matter what because the transmission can disengaged independently and you will not have the greater drivetrain loss that is associated with torque converters and automatics.
So step by step this is how it goes:
1. You hit the brake slowing down for the turn
2. You hit the downshift button for a lower gear
(inside the transmission)
3. First the clutch hydraulic solenoid starts backing off and relieving the circuit of fluid to disengage the clutch packs.
4. As the fluid is being relieved the shift solenoids are being changed so that it can engage the lower gear.
5. At this point the vehicle is in neutral and the computer can blip the throttle
6. After the throttle blip the clutch hydraulic solenoid starts sending fluid to the proper clutch packs as the rpm is going up (using the rpm signal and the output shaft speed sensor the computer can make the transition smoother and also how the clutch hydraulic solenoid gets applied back to put the vehicle in gear.)
7. The line pressure is able to stay high enough to where is can shoot the fluid through the circuit to reduce lag (or shift time) but will inherently have some lag.
As I stated this way the converter can stay locked. I do not feel that the converter gets unlock at any point because timing the re-engagement I feel would be tricky and could cause jerkyness to the shift. Although releasing the lockup converter will raise the rpm of the vehicle I feel it is not enough and it sounds to me that the throttle valve is blipped when downshifting.
Please tell me what you think about my theory and feel free to post postive or negative comments, as long as they are helpful at the end I dont care.
First off I watched a video (here is said video
What I want to know specifically is how the transmission components move, what are the solenoids doing (all of them), how does the lockup function on gears 2 through 8 work with the revmatching?
Here is the theory:
First key component is the fly-by-wire. The throttle valve can move independently from the gas pedal. This could receive an electrical signal to blip the throttle when you want to downshift even though you are on the brake pedal getting ready to turn in. Now the lockup converter can be locked for gears 2 through 8 (this part is confirmed) but does it unlock during the downshifts while rev matching? The second key component I believe is the transmission tune that controls the solenoids and how it controls the solenoids. SO if you have the line pressure solenoid up in pressure but the clutch hydraulic solenoids not sending the fluid to the appropriate clutch packs to engage the gear (assuming no other clutch packs are engaged either) that would render the transmission in neutral. Now the shift solenoids to my understanding just uncover or cover passage ways to the clutch packs that will engage the clutch packs to the proper gear or gear you have selected. Therefore the shift solenoids will have the gear selected, the line pressure can be high and the clutch hydraulic solenoid could be set to not send the fluid to the clutch packs and the transmission is still in neutral. At this point the lockup converter can stay locked no matter what because the transmission can disengaged independently and you will not have the greater drivetrain loss that is associated with torque converters and automatics.
So step by step this is how it goes:
1. You hit the brake slowing down for the turn
2. You hit the downshift button for a lower gear
(inside the transmission)
3. First the clutch hydraulic solenoid starts backing off and relieving the circuit of fluid to disengage the clutch packs.
4. As the fluid is being relieved the shift solenoids are being changed so that it can engage the lower gear.
5. At this point the vehicle is in neutral and the computer can blip the throttle
6. After the throttle blip the clutch hydraulic solenoid starts sending fluid to the proper clutch packs as the rpm is going up (using the rpm signal and the output shaft speed sensor the computer can make the transition smoother and also how the clutch hydraulic solenoid gets applied back to put the vehicle in gear.)
7. The line pressure is able to stay high enough to where is can shoot the fluid through the circuit to reduce lag (or shift time) but will inherently have some lag.
As I stated this way the converter can stay locked. I do not feel that the converter gets unlock at any point because timing the re-engagement I feel would be tricky and could cause jerkyness to the shift. Although releasing the lockup converter will raise the rpm of the vehicle I feel it is not enough and it sounds to me that the throttle valve is blipped when downshifting.
Please tell me what you think about my theory and feel free to post postive or negative comments, as long as they are helpful at the end I dont care.
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LRCSALES (02-21-17)
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STLblueF (01-31-17)
01-31-17, 06:41 PM
#3
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Thread Starter
Thank you flow rider. Although this did not answer all but one question it was still a good read. (came form the article) >>> "A high flow-rate linear solenoid is one of the key elements that work together with special computer
programming to provide quick and precise control in concert with engine torque." I knew that the programming is where the the trick is and that the solenoids to the clutch packs is one of the key elements but how does it do it exactly? I know im getting pretty close but im starting to think that the answer Im looking for lexus does not want to share to anyone.
programming to provide quick and precise control in concert with engine torque." I knew that the programming is where the the trick is and that the solenoids to the clutch packs is one of the key elements but how does it do it exactly? I know im getting pretty close but im starting to think that the answer Im looking for lexus does not want to share to anyone.
02-02-17, 10:20 AM
#5
Tech Info Resource
iTrader: (2)
Why is it "troubling" you?
Sure, it's all proprietary technology and was developed between Lexus and Aisin. Why is it important to know precisely how it works? Have you asked bondango? He designed a TCU for this gearbox, and would likely be the best source of information on this outside of Lexus.
Sure, it's all proprietary technology and was developed between Lexus and Aisin. Why is it important to know precisely how it works? Have you asked bondango? He designed a TCU for this gearbox, and would likely be the best source of information on this outside of Lexus.
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Kojak77 (02-22-17)
02-03-17, 05:55 AM
#7
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Thread Starter
Why is it "troubling" you?
Sure, it's all proprietary technology and was developed between Lexus and Aisin. Why is it important to know precisely how it works? Have you asked bondango? He designed a TCU for this gearbox, and would likely be the best source of information on this outside of Lexus.
Sure, it's all proprietary technology and was developed between Lexus and Aisin. Why is it important to know precisely how it works? Have you asked bondango? He designed a TCU for this gearbox, and would likely be the best source of information on this outside of Lexus.
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02-03-17, 02:43 PM
#9
Tech Info Resource
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The reason why I am interested in this is to learn how Lexus controls the transmissiom to take that information and apply it in different automatic transmissions. I know that there are aftermarket fly-by-wire pedals and throttle body sets and maybe I could get this style of control in other vehicles. Who is bondango and how do I contact him?
Click the link to go to his site. No updates in quite awhile though.
02-03-17, 03:50 PM
#11
Tech Info Resource
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Maybe this is what you were looking for?
02-04-17, 08:31 PM
#12
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Thread Starter
Yes I did open the link and it really just didn't answer much. Also lobuxracer I appreciate those links you sent me. I believe the last link that you sent me answers the question and I was right on the money. We are going to know for sure if my theory is correct when I start messing around with my own autobox and start playing around with a tune for the transmission. lobuxracer I also appreciate the link to the supra 2urgse build It gets pretty interesting but not specific enough on the tune I believe. I will be sitting down and reading all of it and we will see what information this guy offers. I appreciate all of your inputs and if there are other people looking for this kind of info let it be known. Dont forget to search for more info.
02-05-17, 10:18 AM
#15
Tech Info Resource
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TIS. techinfo.toyota.com. I have an annual subscription. It's in the New Car Features (NCF) portion for the ISF from 2008. You would be wise to subscribe for at least a short period. All Toyota/Lexus/Scion vehicle technical information is available, and all technical training documentation is also available. If you really want to understand the mind of Toyota, you need to read. A lot. It's all there.