RPM dip in 3/4/5 gear (AT)

[Craig]

Originally Posted by CircuitJerk

I've had a similar experience but it's not consistent. It catches me off gaurd and I generally attribute it to the torque converter and transmission related logic programming. It's like the computer's not sure what to do and it's not in total lockup.
I think it may also have something to do with throttle position. Does that make sense?
What is the approximate throttle position?
Be interesting to get some logs. Now that I've seen this, I'm going to be more conscious of it and will look to see if I can duplicate. If so, I may run some EcuTek logs. That is, if I have time. The car will be garaged once the first snow/salt hits which could be any time now.

I have Torque, I'll start running it dataloging both Throttle position / RPM /engine load throughout the week and see if I can get some concrete examples of it occurring. Let me know when/if you get any ECU logs.

[carbonBLUE]

Originally Posted by Craig

I'll start this off with info:

FRS purchased mid august
Perrin Drop in filter installed 10/8
Zeta intake pipe installed 10/12
Car has approximately 4.2k miles on it today (12/3/12)
Car has 'crickets' and will be brought to dealership to address both that and the rear tap from the trunk

This problem has been occurring prior to both 'mods,' and I have removed them to test to see if the problem persists, and it does.

When driving in paddle mode, I find my car exhibits a strange RPM dip in 3/4/5 gear during acceleration. Example: Pull behind tractor trailer in 6th, slow down momentarily, check other lane, downshift once into fifth, then again into fourth, and proceed to accelerate into the next lane in order to overtake said truck. Whilst pulling through fourth, around 4k rpm, the car loses a noticeable amount of power, (Torque dip I presume) and the RPMs will drop anywhere from 200-500 rpms, then continue to climb as normal afterwards. This is noticed not only through watching the tachometer, but also the engine loses a noticeable amount of sound through this range.

This would also occur if I'm in slower traffic, shifting into 3rd to pass someone or pull into traffic etc.

Happens in 5th if I'm driving at a higher speed in sixth, and drop into fifth to pick up a couple MPH for whatever reason.

I attempted to take a crappy cell video of it today to show here, but traffic was s**t so I was unable to 'open her up'.

Was wondering if anyone had any idea what's going on here, also if I should bring it up when I go to have the TSB on the crickets taken care of.

Thanks ^_^

~Craig

here's a tip

press down the gas pedal before you start shifting, or make sure the car is in gear fully before pressing the gas (give it about a second)


you can also double tap the shifter and it will skip a gear completely (fucking awesome in my book)

if you aren't on the gas the computer thinks you are cruising, then it will try to do the smoothest(slowest) shift it can to keep you happy

if you punch it mid shift, the transmission and engine wont have time to calculate and compensate for that change and lock up quick enough

cruising = slow shift = about 1 second to complete a shift and lock up(or even more time sometimes)
flooring it = very fast shift = around .1-.2 seconds a shift (sounds awesome with an exhaust!)

[Craig]

Originally Posted by carbonBLUE

here's a tip

press down the gas pedal before you start shifting, or make sure the car is in gear fully before pressing the gas (give it about a second)


you can also double tap the shifter and it will skip a gear completely (fucking awesome in my book)

if you aren't on the gas the computer thinks you are cruising, then it will try to do the smoothest(slowest) shift it can to keep you happy

if you punch it mid shift, the transmission and engine wont have time to calculate and compensate for that change and lock up quick enough

cruising = slow shift = about 1 second to complete a shift and lock up(or even more time sometimes)
flooring it = very fast shift = around .1-.2 seconds a shift (sounds awesome with an exhaust!)

I've never tried flooring it whilst shifting, usually either stop pressing the peddle down farther or let off completely if cruising. Didn't know about the double shift either.

I don't think that'll help the mid RPM climb dip I'm seeing though :/

[Craig]

[ame="http://www.youtube.com/watch?v=fmTN7sNDm9g"]Rpm dip - YouTube[/ame]

here's a crappy video of the problem I'm seeing.

I'm sitting in sixth, go to change lanes downshift into fifth, then accelerate with steady throttle position throughout.

It's short but you can catch the drift of what's going on. I'll try to get a better video sometime tomorrow or the next day, driving a different car atm.

[Subie]

It looks like your torque converter unlocked when you downshifted, then locked again. I don't see what the problem is...

[WiKKiD]

Originally Posted by Subie

It looks like your torque converter unlocked when you downshifted, then locked again. I don't see what the problem is...

X2

[carbonBLUE]

Originally Posted by Craig

here's a crappy video of the problem I'm seeing.

I'm sitting in sixth, go to change lanes downshift into fifth, then accelerate with steady throttle position throughout.

It's short but you can catch the drift of what's going on. I'll try to get a better video sometime tomorrow or the next day, driving a different car atm.

yeah you hit the gas right when you shifted, the ECM couldnt compensate because when you shifted you were cruising but a split second after that you floored it

try giving gas before you shift

also i noticed the shift times and harshness greatly depend on current rpm

higher in the rev range the shifts are harder and more precise

like if i take it past 5k in 1st and shift, the tires will break loose from how aggressive the shift was

below its nice and smooth like butter

the more miles i put on the car the smoother the shifts get as well around cruising speeds, i hardly notice any kick anymore

[BoostedWrbBrz]

Torque converter lock-up

[Tannis]

I don't have an FRS... yet... but I do have a 5AT 2010 Acura TSX. I have mainly small bolt-on type mods, CT-E Icebox and ported runners. Both before and after install, I have had the same exact RPM dips, primarily in 3rd and 4th gears right at 4k. It'll dip down to about 3750 and then slowly climb back up. I see a torque dip in my dyno chart, however, is the torque dip there because that is where is naturally drops or does it dip because the RPMs are dropping? So yeah, I think it is an AT thing. Doubt it is anything to worry about because I have 41,000mi on it now and no issues. Al my mods were done at around 16-17k.

Just thought I'd share that with y'all as I don't believe it is a real issue, just a nuance and a fact of life with these newer transmissions. Also read somewhere it has something to do with some emissions crap. How or why I can't say.

[CircuitJerk]

I didn't bother with the logs as I haven't had a chance, but now that I've seen your video, I've been able to reproduce it as well.
I'm going to stick with my initial assessment and I think being a little more aggressive with the throttle mitigates this. I haven't had a whole lot of time to play with this either, but some of the other comments cover things pretty well.
If I'm cruising, or on the highway, I leave it in automatic mode and toggle on the sport mode and increase throttle accordingly to get it to kick down.
That's one of the many reasons I got the auto in the first place really..

I don't think this is a problem per se, but I do think the logic could improve. If that's even possible in software. It may be a mechanical limitation.
So, nothing to be concerned about IMO.

[BlueDubbinTDI]

I know this is an older thread but I also have a Perrin Filter + Auto FR-S. Has this issue been covered more thouroughly than just this thread cuz mine does this in 4th gear right before 4k too

[meadowz06]

Torque converter!