Deciphering this rpm change

On my 2014 crew cab if I was on 4th gear cruising at 50mph I would be doing 1500 rpm dead center.Now with the new dynomax super turbo muffler installed along with a drop in AFE pro filter, to cruise at 50 the tach will now read 1650 rpm,why the increase in rpm?? I already pulled the negative cable off for an hour,reinstalled, then drove it for 19miles before taking these results,can someone explain??

 

I don't know… I will sub to see the ensuing posts though.

 

Sounds like your torque converter isn't going into lockup at 50 anymore. Could be as simple as different wind causing a higher load and hence no lockup. Or could be the exhaust made you lose some torque at 1500 and again no lockup.

 

I think wads might have hit upon it. It's possible that your muffler opened up the exhaust and caused the engine to lose enough low end torque to make it need more rpms to move the truck.

 

Or the TC may not be locking up because you disconnected your battery and have only driven 19 miles.
It takes a few start/restart cycles for the ECU to relearn the proper trims.

 

Let me clarify,I was getting the 1500rpm/50mph with the dynomax muffler already installed it was the higher rpms at the same speed that was noticed when the afe dry filter and battery disconnect/reconnect were done,my bad...but Rich may have a point,Im taking her out on a 500mi trip soon with my scangauge E hooked up,we shall see.BTW charcoal filter was removed too. I Luv to experiment on these minor mods.
Over a decade ago I installed a gibson hi flow muffler (drone master), kn air filter which I cleaned and oiled once a year and a diy cold air intake which ran to the inside of the fender to my 2.4l nissan king cab. I lost low end torgue but at 2800 rpm it would be flying and around 3200 rpm+ 90 turn to 95mph easily, wasnt even flooring yet but then I had young ones to think about so I had to ease up ( I was scared too). I think without the proper test equipment such mods are difficult to verify at low rpm/street driving but at high rpm,breaking the law speed they sure do shine.

 

There is no way an air filter, or muffler, can change the rpm in a given gear, at a given speed. As others have said, it must be related to the battery being disconnected, and the ECU having to readjust to the current engine operating parameters, and that's causing the torque converter not to be locked up at that speed. It should correct itself after a few trips.

 

You're likely right. I know nothing about auto transmissions and haven't owned a vehicle with one since the 1970's. They just waste power and create heat pumping fluid and actuating clutches that could be used to move the truck.

 

Automatic transmissions have changed a lot since the 1970s.
A modern transmission with the torque convertor locked is operating at very nearly zero slip.
On the transmission itself, if there is a mismatch between the input and output shaft RPM compared to the table values, it will throw a CEL.

40 years ago, manual transmissions were the way to go for fuel economy. Today, not so much. It takes a very skilled driver with a manual to best an automatic.

 

Thank you. But not really with the I4 stick vs slush.

European models of most everything do better with a stick, mysteriously. Most rentals in Europe are sticks. Rented a VW Touareg Stick 2L diesel in Germany, couldn't get an automatic.

They choose to make automatics that get better MPG than sticks in the US.

 

This is just kind of random, but when I go to Greece I notice that as we see about 90% of the cars here are automatic, its like 90% of the cars their are stick.

 

Yep

 

It is pretty close. The 2012 Tacoma 2.7 factory stats are:

Manual: 21/25 mpg city/highway

Auto: 19/24 mpg city/highway

 

And yet with my 2.7 auto, I consider 24 mixed to be bad.

 

I understand. Good driving practices can always up the average. My latest 1,000 mile average is 23.5 mpg on Winter blend, with less than 5% freeway, and lots of first gear crawling up and down steep rural canyon roads fully loaded with tools and materials.

Greg

 

Just a side note, I checked mine today.
50mph at steady no-load cruise (level ground) and I'm at 1500.
I don't get to 1650-1700 until 55 or so.

 

That's because we 5 lugs gots de road gears.