Ford Mustang Forum banner

Status
Not open for further replies.
1 - 19 of 19 Posts

·
Registered
Joined
·
7 Posts
Discussion Starter #1
So here's the setup, I have a 2002 automatic 3.8L and i have a Cold air for it already, and wanted to increase the intake even more, so i purchased a BBK 65mm throttle body and installed it. i did notice more power and better sound and is fine, but now when i press on the gas (all the way down for example) when its above first gear, it DOES NOT downshift to get that extra passing power like normal. it just sits in the same gear and increases in speed slowly. why isnt it downshifting?? did i maybe tweak the TPS, throttle position sensor, in the process? or does the combo of the two intake upgrades mess up the cpu?...
 

·
Registered
Joined
·
313 Posts
I have same problem with my 06 auto, it doesnt do it with stock air box. I havent found a solution yet. Do you have a tune?
 

·
Registered
Joined
·
7 Posts
Discussion Starter #3
I have same problem with my 06 auto, it doesnt do it with stock air box. I havent found a solution yet. Do you have a tune?
air box? you mean the factory intake? no, i dont have a tune. its a pain as well as dangerous cuz i could be on the freeway and switch lanes into a quicker one and not have the power i need to get me up to speed wit everyone behind me... ya know?
 

·
Registered
Joined
·
1,544 Posts
Your auto tranny will shift down depending on torque feedback, not throttle position. So adding a CAI and TB will not affect the shifts.

Also, in order to downshift, your speed must be withing the range of that gear. From my own experience, I found 1st gear is from 0-42ish mph, then 2nd is from (0-10)-75 mph, then 3rd goes from ~50-100 mph. So if you're on the highway, cruising at 65, you should be in 3rd gear: when you step on it, it would downshift briefly to 2nd, and then back to 3rd when you hit about 70-75... But if you're going faster than that, it might not have the rpm range to do that. What kinda speeds are you talking about here?

(Also, you could always manually shift down, but you must be careful so you don't overrev your engine!)
 

·
Registered
Joined
·
268 Posts
lol it doesnt down shift because its an auto tranny lol

think of it this way. your car cant see what is coming at it, it cant make decisions or drive itself. its computer programmed so if you are cruising at 55mph and you wanna pass this slow mini van in front of you, you instantly think slamming on the gas will have the car downshift and go faster, thats not how the tranny works tho.

its programmed to save gas and drive smoothly so in its mind it thinks full throttle, increase speed. it cant tell whether you want it to shift from 4th to 2nd or not. lol thats what manuals are made for=]

but to help you in some sense no there is nothing wrong with your tranny and your mods didnt affect it. i had an audi with an auto tranny and when i wanted to down shift i double stomped the gas so full throttle, let off, full throttle and hold. it downshifted everytime.:bigthumbsup if you want speed response to pass them mini vans i'd deff get a stick for future reference=]
 

·
Registered
Joined
·
268 Posts
Your auto tranny will shift down depending on torque feedback, not throttle position. So adding a CAI and TB will not affect the shifts.

Also, in order to downshift, your speed must be withing the range of that gear. From my own experience, I found 1st gear is from 0-42ish mph, then 2nd is from (0-10)-75 mph, then 3rd goes from ~50-100 mph. So if you're on the highway, cruising at 65, you should be in 3rd gear: when you step on it, it would downshift briefly to 2nd, and then back to 3rd when you hit about 70-75... But if you're going faster than that, it might not have the rpm range to do that. What kinda speeds are you talking about here?

(Also, you could always manually shift down, but you must be careful so you don't overrev your engine!)
50-100? in 3rd? wtf kind of gears do you have?

if its a stock v6 tranny we're talking about here its not going to be in 3rd gear at 65mph, you'd be around 4000rpms while yer "cruising"

in an automatic transmission while cruising the tranny will always go to 4th gear unless its like 45mph and lower then it'll most likely go to 3rd, ect.

i dont think auto tranny v6's can even go over 100mph without tunes and a disabled limiter.
 

·
Registered
Joined
·
1,544 Posts
50-100? in 3rd? wtf kind of gears do you have?

if its a stock v6 tranny we're talking about here its not going to be in 3rd gear at 65mph, you'd be around 4000rpms while yer "cruising"
Ok, so I don't know exactly what speed it kicks in - but I do know that if I stomp on it and keep holding I shift at ~45 mph, ~70 mph, and then a little over ~100 mph. The ratios on my tranny (4R70W) are 2.84, 1.55, 1.00, 0.7 for each gear. With a stock drive gear of 2.73, that yields 69.5mph at 2500 rpm in 3rd gear: decent cruising speed. Check it out: http://www.angelfire.com/fl/procrastination/rear.html Also, a picture is attached showing the calculation.

jakksincorpse said:
in an automatic transmission while cruising the tranny will always go to 4th gear unless its like 45mph and lower then it'll most likely go to 3rd, ect.

i dont think auto tranny v6's can even go over 100mph without tunes and a disabled limiter.
They will not always go to fourth: only if the OD is on. I drive with it turned off, so that I don't have to drop two gears (4th-2nd) when I try to pass. Also, I've been up to 110mph - and that's when the speed limiter kicked in. But they can go higher...
 

Attachments

·
Registered
Joined
·
1,544 Posts
lol it doesnt down shift because its an auto tranny lol

think of it this way. your car cant see what is coming at it, it cant make decisions or drive itself. its computer programmed so if you are cruising at 55mph and you wanna pass this slow mini van in front of you, you instantly think slamming on the gas will have the car downshift and go faster, thats not how the tranny works tho.

its programmed to save gas and drive smoothly so in its mind it thinks full throttle, increase speed. it cant tell whether you want it to shift from 4th to 2nd or not. lol thats what manuals are made for=]

but to help you in some sense no there is nothing wrong with your tranny and your mods didnt affect it. i had an audi with an auto tranny and when i wanted to down shift i double stomped the gas so full throttle, let off, full throttle and hold. it downshifted everytime.:bigthumbsup if you want speed response to pass them mini vans i'd deff get a stick for future reference=]
Have you ever driven an auto - or even studied them? :headscratch: There's a bit of misinformation in your post...

Autos downshift based on torque feedback - and yes, they will do it all on there own if the speed and acceleration require it. So if you want to pass someone, you step on it - more torque/power comes from the motor (due to increased air flow) and tries to turn the wheels. But the wheels "fight back" since you are trying rapidly accelerate the wheels. This creates a higher torque demand relayed back through the driveline, "telling" the auto it needs to go down a gear to where there is more torque. Read here for more info: TCCoA Transmission Article - Page 3

Autos are not computer-controlled in the sense you are thinking: it's all by pressure and tranny fluid flowing that shifts gears. The ECU only controls the line pressure, which affects how fast the tranny shifts.

And you don't need to double-stomp or whatever :nono:: just press the pedal to the floor. The auto will take over from there...
 

·
Registered
Joined
·
2,747 Posts
You'll have to forgive jakksincorpse, he has no idea at all what he is talking about when it comes to cars, especially Mustangs. Double stomping to make it downshift is possible the dumbest thing I have ever heard in my life.

Anyhow, Silver J has about the best response so far. Something is definitely not right if it refuses to downshift. Anytime you drastically increase the throttle it should first unlock the torque converter and then start dropping gears if possible.
 

·
Registered
Joined
·
1,544 Posts
You'll have to forgive jakksincorpse, he has no idea at all what he is talking about when it comes to cars, especially Mustangs. Double stomping to make it downshift is possible the dumbest thing I have ever heard in my life.

Anyhow, Silver J has about the best response so far. Something is definitely not right if it refuses to downshift. Anytime you drastically increase the throttle it should first unlock the torque converter and then start dropping gears if possible.
Ahhh yes - I see this now... I just looked through some of his old posts/threads (cuz I was thinking "this guy can't be real!") - I see what a misinformed person he is... :so Anyways, thanks for the heads up (and back-up :shigrin).
 

·
Registered
Joined
·
2,867 Posts
Your auto tranny will shift down depending on torque feedback, not throttle position. So adding a CAI and TB will not affect the shifts.
the pcm uses rpm's, vehicle speed, and throttle position to decide how and when to downshift.

when you slam on the gas you are telling your car that you want to go faster. the pcm responds by downshifting.

when the pcm triggers a downshift, it will either go to as low of a gear as possible, or as low of a gear as it thinks you want to go to. how does the pcm decide which gear? by combining the signals from the CKP, the VSS, and the TPS.

EXAMPLE. say you're cruising along at 55mph with o/d enabled. you're in 4th gear. press the gas pedal 3/4 of the way down (TPS 75%) and the pcm will only downshift to 3rd. stomp it all the way down(TPS 100% aka WOT), and the pcm will skip 3rd and go right to 2nd.

not only that, but another way the TPS will help out the pcm is preventing what's referred to as "lift-foot slam".

when your at WOT, people are going to want a nice firm upshift;
EXAMPLE. say your in "D", and your at WOT, and you redline 2nd. the pcm is going to know you want to keep going faster so it's going to shift into 3rd aggressively.
now, say you just want to pass a bus. your in "D", at WOT, but just as you redline 2nd, you let off the gas because your in front of the bus and dont want to go any faster. well then the pcm looks at your TPS sensor and realizes you dont want to go any faster, so while redlining 2nd and letting off the gas, it will actually shift into 3rd softly rather than harshly/firmly.
if the pcm didnt monitor the TPS signal, if you redlined 2nd and let off the gas just before the pcm shifted you to 3rd, it would bang into 3rd even though you had your foot off the gas; aka "lift-foot slam".

the TPS is a a vital piece of information to the PCM when deciding when and how to downshift.
 

·
Registered
Joined
·
2,867 Posts
You'll have to forgive jakksincorpse, he has no idea at all what he is talking about when it comes to cars, especially Mustangs. Double stomping to make it downshift is possible the dumbest thing I have ever heard in my life.
lol :laugh:







(15 characters)
 

·
Registered
Joined
·
326 Posts
I have a similar problem every once in a while. I mash the gas at like 25-30 and it stays in like 3rd gear at less than 2000 rpms. It has only happened a few times, but it is quite frustrating.
 

·
Registered
Joined
·
7 Posts
Discussion Starter #17
the pcm uses rpm's, vehicle speed, and throttle position to decide how and when to downshift.

when you slam on the gas you are telling your car that you want to go faster. the pcm responds by downshifting.

when the pcm triggers a downshift, it will either go to as low of a gear as possible, or as low of a gear as it thinks you want to go to. how does the pcm decide which gear? by combining the signals from the CKP, the VSS, and the TPS.

the TPS is a a vital piece of information to the PCM when deciding when and how to downshift.
this is the most helpful piece of information posted so far. so thanks. fyi everyone, i know the general attributes of how an auto transmission works and behaves. its just with this new throttle body its acting up. when i was transferring the TPS from the factory tb to the BBK one, i recall maybe tweaking it cuz i put it on wrong at first and maybe overspun it. should i buy a new one?
 

·
Registered
Joined
·
1,544 Posts
...the TPS is a a vital piece of information to the PCM when deciding when and how to downshift.
Thanks for adding all the info about how electronics interact and affect shifting... I don't know much about all that. :so That's cuz my TPS is usually at 100% ;) :bigthumbsup :gringreen :happyhapp
sorry i dont know anything about auto tranny's in my mind i thought since the car has an ecu and an "automatic" transmission shifted for you i thought thats what the whole computer system was about. i knew there was transmission fluid but i thought that was just lubricant.
Why dont all of you inform me instead of ***** at me. that would make alot more sense.
This is why we don't "inform" you - cuz you blast people and start cursing. And actually, people have tried to help you (I checked your other threads) -- and you just got mad and started spouting off about hating Stangs and "imports rule". So now we all choose to just ignore you. :bigthumbsup BTW - name-calling gets you nowhere when asking for help.
Go back to Iceland.
this is the most helpful piece of information posted so far. so thanks. fyi everyone, i know the general attributes of how an auto transmission works and behaves. its just with this new throttle body its acting up. when i was transferring the TPS from the factory tb to the BBK one, i recall maybe tweaking it cuz i put it on wrong at first and maybe overspun it. should i buy a new one?
Ah... now the truth comes out! :shigrin j/k - but yeah, that could be the cause of the problem. You say you tweaked it: could you explain a little better? Cuz I think you're onto something. :scratchchin
 

·
Registered
Joined
·
2,867 Posts
this is the most helpful piece of information posted so far. so thanks. fyi everyone, i know the general attributes of how an auto transmission works and behaves. its just with this new throttle body its acting up. when i was transferring the TPS from the factory tb to the BBK one, i recall maybe tweaking it cuz i put it on wrong at first and maybe overspun it. should i buy a new one?
sorry for the late reply...

if you actually did damage the TPS when re-installing it, it'd likely set a CEL.

if your CEL is on and has anything to do with the TPS, then it's more than likely you damaged it.
 
1 - 19 of 19 Posts
Status
Not open for further replies.
Top