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Throttle response

Swerd

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Swerd Enthusiast

Swerd

Posted
Posted

Hi, I recently got my first Silverado. It’s a 2015 5.3 CC Z71. I really like it but the throttle response is awful. Seems to have plenty of power once you get on it, but from a stop when I hit the gas it is so slow to respond. Is this normal? The engine dose not stumbles or misfire, just slow to respond. Also at lower speeds it seems like the transmission has a hard time deciding what gear to be in. Between the slow throttle response, V4 mode, and confused transmission bumper to bumper traffic is painful. I am coming from a car. Do I need a trip to the service department or is it something I just need to get used too! 

 

Thanks

 

 

dmorrisL86 Enthusiast

dmorrisL86

Posted
Posted

That’s probably just the truck trying to keep rpm’s low/stay in V4 to achieve fuel efficiency. Thank the EPA for that. My ‘17 6.2 does the same thing. But once you get into it...hold on! I love the truck and the 6.2, but the way GM has it tuned is frustrating. Your best bet is to get it tuned and/or disable AFM. There’s a local tuner near me that will tune out AFM for $150. I plan on doing this in the near future. 

muddkatt Senior Enthusiast

muddkatt

Posted
Posted

It is "normal" due to the tuning that GM put in the truck. It actually takes a full 3 seconds from the time you stomp the gas pedal until the butterfly valve opens to WOT.

 

 

SirenRed16 Senior Enthusiast

SirenRed16

Posted
Posted
Hi, I recently got my first Silverado. It’s a 2015 5.3 CC Z71. I really like it but the throttle response is awful. Seems to have plenty of power once you get on it, but from a stop when I hit the gas it is so slow to respond. Is this normal? The engine dose not stumbles or misfire, just slow to respond. Also at lower speeds it seems like the transmission has a hard time deciding what gear to be in. Between the slow throttle response, V4 mode, and confused transmission bumper to bumper traffic is painful. I am coming from a car. Do I need a trip to the service department or is it something I just need to get used too! 
 
Thanks
 
 
Next time you're in bumper to bumper traffic at low speeds go into M5 and see if the drive is any better.

Sent from my SAMSUNG-SM-N920A using Tapatalk

wforrest08 Senior Enthusiast

wforrest08

Posted
Posted

What rear end gear you got? If it’s a 308 truck your out of luck. I bought my 15 brand new 5.3L 343 gear drove it 3 thousand miles and I couldn’t take it any more I had a Range to eliminate the AFM but the trannys never ending can’t make up it’s mind drove me to a eng/trans tune with AFM delete and torque management reduction. Tranny shifts 100% better 90% of the time shifts normal. As far as when you hit the pedal it’s just the way they are now they really lack off the line it will take some getting use to.

 

These trucks are for sure highway cruisers like the rpms I catch myself 20 over the speed limit all the time...

Donstar Senior Enthusiast

Donstar

Posted
Posted
2 hours ago, Swerd said:

Hi, I recently got my first Silverado. It’s a 2015 5.3 CC Z71. I really like it but the throttle response is awful. Seems to have plenty of power once you get on it, but from a stop when I hit the gas it is so slow to respond. Is this normal? The engine dose not stumbles or misfire, just slow to respond. Also at lower speeds it seems like the transmission has a hard time deciding what gear to be in. Between the slow throttle response, V4 mode, and confused transmission bumper to bumper traffic is painful. I am coming from a car. Do I need a trip to the service department or is it something I just need to get used too! 

 

Thanks

 

 

Congratulations on your new truck.  The throttle response may be different than what you've experienced but it is not awful.  Other members have found ways to alter the stock throttle response but this is not necessary.   I recommend you enjoy your truck for awhile before making any changes.  You may find that you become very comfortable with how your truck responds.   I look forward to driving my truck following driving other vehicles!

oak1971 Enthusiast

oak1971

Posted
Posted

Coming from an '07 5.3 crew cab short box to a '15 5.3 ecotec double-cab short box, I can't say I'm down on power (cause I'm not). The 2007 did not have a v4 mode, but I really don't notice the transition much. I do not indulge my inner speed demon like I once did, but I have no doubt it's a toe tap away.

oak1971 Enthusiast

oak1971

Posted
Posted
3 hours ago, muddkatt said:

It is "normal" due to the tuning that GM put in the truck. It actually takes a full 3 seconds from the time you stomp the gas pedal until the butterfly valve opens to WOT.

 

 

Why would they do that?

Swerd Enthusiast

Swerd

Posted
  • Author
Posted
7 hours ago, wforrest08 said:

What rear end gear you got? If it’s a 308 truck your out of luck. I bought my 15 brand new 5.3L 343 gear drove it 3 thousand miles and I couldn’t take it any more I had a Range to eliminate the AFM but the trannys never ending can’t make up it’s mind drove me to a eng/trans tune with AFM delete and torque management reduction. Tranny shifts 100% better 90% of the time shifts normal. As far as when you hit the pedal it’s just the way they are now they really lack off the line it will take some getting use to.

 

These trucks are for sure highway cruisers like the rpms I catch myself 20 over the speed limit all the time...

 I do have a 3.08 gear. I wish I would have known a little bit more before I bought the truck but so be it.  Sounds like I’m going to need to get a tune with AFM disabled.  Any recommendations? 

 

 Thanks for all the responses!

muddkatt Senior Enthusiast

muddkatt

Posted
Posted
6 hours ago, oak1971 said:

Why would they do that?

They do it so that the drive train  is not subjected to instant full load conditions. Keeps the amount of parts failures down for warranty jobs, and the truck will get 0.01 MPG better fuel mileage to meet CAFE requirements.

amxguy1970 Senior Enthusiast

amxguy1970

Posted
Posted
3 hours ago, Swerd said:

 I do have a 3.08 gear. I wish I would have known a little bit more before I bought the truck but so be it.  Sounds like I’m going to need to get a tune with AFM disabled.  Any recommendations? 

 

 Thanks for all the responses!

 

11 hours ago, wforrest08 said:

What rear end gear you got? If it’s a 308 truck your out of luck. I bought my 15 brand new 5.3L 343 gear drove it 3 thousand miles and I couldn’t take it any more I had a Range to eliminate the AFM but the trannys never ending can’t make up it’s mind drove me to a eng/trans tune with AFM delete and torque management reduction. Tranny shifts 100% better 90% of the time shifts normal. As far as when you hit the pedal it’s just the way they are now they really lack off the line it will take some getting use to.

 

These trucks are for sure highway cruisers like the rpms I catch myself 20 over the speed limit all the time...

The gear has nothing to do with throttle response, it is a touch slower with a touch better mpg and no one could tell which is which if they drove them back to back.

 

Throttle response is slower, could be because of the flexible pedal but also how it is tuned for mpg. It opens much faster than the video shows at WOT btw. At idle in park blip the throttle, it will slowly climb rpms as if it barely opened. If you stomp the gas pedal they shoot up very quick, it opens all the way much faster.

 

Tyler

Donstar Senior Enthusiast

Donstar

Posted
Posted
3 hours ago, Swerd said:

 I do have a 3.08 gear. I wish I would have known a little bit more before I bought the truck but so be it.  Sounds like I’m going to need to get a tune with AFM disabled.  Any recommendations? 

 

 Thanks for all the responses!

This is a conclusion that is easy to come to based solely on this forum.  You will find lots of comments about the noticeable transition between V4 and V8.  I suspect many of these claims depend on the green indicator light.  If I could feel my truck switch, I'd have it in for service.  The new trucks that are coming will have DFM which will be even a greater challenge for those that want all cylinders active at all times!  Personally, I welcome changes that improve the efficiency yet maintain the functionality of my truck. 

Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
12 hours ago, oak1971 said:

Why would they do that?

Did you know that a 'butterfly' valves flow rate is not proportional to blade angle?  This delay gives a more linear throttle response. It also does something else. It makes throttle angle more speed appropriate. In the graph note that about 80% of the valves flow rate is obtained at 50% blade angle. If the throttle body is sized for X CID @ WOT then 50% angle @ 25% rpm results in  weak manifold vacuum. The fuel tables are constructed on volumetric efficiency based on the manifold absolute pressure, not the barometric pressure vs CID. If you look at these tables you might be surprised to find that VE's of 98% are possible at 1,000 rpm and 20% TPS. In simpler terms the VE tables are the ratio of cylinder density to manifold density and not theoretical swept volume standard atmospheric density vs barometric density. 

 

Throttle response isn't how fast the throttle blade reaches WOT. It's a mechanical time constant that is often limited by things like rotating mass than air supply. 

 

 

Butterfly-Valve-Characteristic.png

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