Anyone have RPM Surge when it downshifts? - Acura MDX Forum : Acura MDX SUV Forums
 
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post #1 of 11 (permalink) Old 08-07-2012, 03:09 PM Thread Starter
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Anyone have RPM Surge when it downshifts?

My MDX shifts perfectly and drives great. I noticed that when i'm in traffic and I cruise up to 50mph and then slow down it downshifts, then bounces for a fraction of a second (it will hit 1200 then bounce to like 1400 then back down) , just wanted to see if this was normal? This is NOT the surge I'm talking about where someone cruises and it just bounces, this is for a downshift. Thank you.

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post #2 of 11 (permalink) Old 08-09-2012, 05:58 PM
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nope, never noticed that in my MDX or my other Acura's with the tipronic function.
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post #3 of 11 (permalink) Old 08-10-2012, 09:28 AM
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If you're coasting as you slow down and the car downshifts, you are probably noticing the the engine 'braking'. The car pushes the engine a little faster as the gear ratio drops, then the engine slows the car. If you are using the brakes to slow down instead of coasting the engine speed change would be minimal or non existent.

Look at the tach as you downshift using the paddle shifters, you should see the same thing.
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post #4 of 11 (permalink) Old 08-10-2012, 10:17 AM Thread Starter
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^^^ Thank you so much, that's what it is. Glad it's normal. So to get this straight, when I'm naturally slowing down without brakes, the engine speeds up a little bit as it shifts up from a lower gear? And when I do use the brakes it is non existent.
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post #5 of 11 (permalink) Old 08-10-2012, 01:30 PM
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When you are coasting toward a stop the car automatically downshifts, not upshifts. Once it downshifts the engine would naturally turn at a higher speed for the same vehicle speed. The engine then causes the car to slow down a little more. The same thing happens when you use the brakes, but since the brakes continue to slow the vehicle, the engine doesn't have to work so much to slow it down.

It's not unique to the MDX or to automatic transmissions. It's so natural I never pay attention to it. So this morning as I was costing to a stop sign I watched the tach. When the tranny downshifted the rpm's momentarily jumped about 300 rpm's. It's all good, if that's what you are experiencing.
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post #6 of 11 (permalink) Old 11-08-2012, 04:58 PM
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I think I have the same thing however sometimes when the car is downshifting, I can actually feel the car speed up for a split second. Is that normal??
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post #7 of 11 (permalink) Old 11-08-2012, 08:36 PM
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Originally Posted by reo1fan View Post
I think I have the same thing however sometimes when the car is downshifting, I can actually feel the car speed up for a split second. Is that normal??
I've felt the same and I don't feel it's engine braking. I've felt it literally surge a bit, sometimes even when I'm pulling into my garage very slowly. I may speak with the dealer about it if I can specifically replicate it.

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post #8 of 11 (permalink) Old 11-09-2012, 08:54 AM
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The 2010 and newer Mdx blips the throttle on downshifts.
Just wondering if your misinterpreting that action with the vehicle "accelerating on downshifts".

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post #9 of 11 (permalink) Old 11-09-2012, 07:49 PM
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The 2010 and newer Mdx blips the throttle on downshifts.
Just wondering if your misinterpreting that action with the vehicle "accelerating on downshifts".
That's exactly what it seems like to me, a brief throttle blip. My concern however is that it also seems to happen when I'm driving very slowly, tight spots. Like into or out of a parking space or my garage.

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post #10 of 11 (permalink) Old 11-09-2012, 08:43 PM
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Do you have the climate control on auto or the AC on? I notice that the idle blips when the compressor cycles on and in very light throttle conditions, it translates into a slight increase in speed.
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post #11 of 11 (permalink) Old 11-10-2012, 09:04 AM
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Originally Posted by kokerj View Post
Do you have the climate control on auto or the AC on? I notice that the idle blips when the compressor cycles on and in very light throttle conditions, it translates into a slight increase in speed.
Could be, I'll watch that closer and see if there's a tie in. I have the A/C off now that it's chilly here. I know some folks and car makers recommend leaving it on all the time, but I'm old school and would rather it be off when I'm not actively needing it.

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