Engine RPM lock?

Justin_R · January 4, 2020

Hope everyone is doing well.

I used to drive a Toyota FJ Cruiser before getting my Silverado 1500 Z71 5.3L, and I do go off-roading time to time.

when revving so hard the the RPM reaches a limit then come down and goes up again rather slowly than what I used to get driving my FJ Cruiser. (Gear 1)

Is it some what a safety thing so the engine wont get damaged?

Here's a clip on how it usually happens when I rev on gear 1 climbing a sand dune

is there a way to get the RPM so be steady and some what more responsive, rather than cut the RPM down and slightly goes up.. like 1-2 seconds gap rather than split seconds gap.

I am sorry because I don't know what people call this sound.

Hope to find answers thank you!

Mike GMC · January 4, 2020

Sounds to me like your at redline, maybe try letting it shift so it doesn't hit the Rev limited.

CamGTP · January 4, 2020

That is how the factory calibration sets up the limiter with drive by wire throttle bodies. It's a fuel cut and a torque cut to prevent over rev aka hitting the limiter.

It's possible that someone with good knowledge of tuning software could help you fix it but that could still be hit and miss.

Justin_R · January 4, 2020

18 minutes ago, Mike GMC said:

Sounds to me like your at redline, maybe try letting it shift so it doesn't hit the Rev limited.

Thanks for your reply!

Thing is when climbing a sand dune, I need the maximum RPM and Torque, shifting will only kill the built up torque and lose momentum.. aka fail to reach.

By having it rev on high RPM constantly I have better momentum to keep climbing without losing torque much rather than losing RPM and build up again.

Justin_R · January 4, 2020

5 minutes ago, CamGTP said:

That is how the factory calibration sets up the limiter with drive by wire throttle bodies. It's a fuel cut and a torque cut to prevent over rev aka hitting the limiter.

It's possible that someone with good knowledge of tuning software could help you fix it but that could still be hit and miss.

CamGTP thanks for your input!

I see... yeah I some what felt its a factory thing but never knew what actually happens.. thank you very much it sheds light into what actually happens to have this result.

I don't want to go beyond the limiter.. but stay close to it and keep it more stable than whats happening now (RPM drop)

Yeah I guess its more likely a tuning thing... lets hope someone have already by-passed this and shares his experience to us!

Edited January 4, 2020 by Justin_R

CamGTP · January 4, 2020

Often times there is a 50 or 100rpm drop that must happen before it will go back to normal, so that is why you see and feel the delay.

I've never had a need to hold 1st gear or any gear so I've never messed with that function in the computer. But I've hit my 6,050rpm limiter once in 1st because of wheel spin before, pretty much just shuts the truck down and goes right back to full power lol.

Justin_R · January 4, 2020

1 minute ago, CamGTP said:

Often times there is a 50 or 100rpm drop that must happen before it will go back to normal, so that is why you see and feel the delay.

I've never had a need to hold 1st gear or any gear so I've never messed with that function in the computer. But I've hit my 6,050rpm limiter once in 1st because of wheel spin before, pretty much just shuts the truck down and goes right back to full power lol.

Yeah! I hate it when that happens.. I also need to maintain a high RPM to make sure when turning right to come down off the hill.. Constant high RPM helps to avoid being flipped over.. its a matter of calucating and building enough speed and tourqe or gravity will just pull you down ahaha.. so it was scary and surprising when it happened, hopefully I managed to come down safely.

swathdiver · January 4, 2020

37 minutes ago, Justin_R said:

Yeah! I hate it when that happens.. I also need to maintain a high RPM to make sure when turning right to come down off the hill.. Constant high RPM helps to avoid being flipped over.. its a matter of calucating and building enough speed and tourqe or gravity will just pull you down ahaha.. so it was scary and surprising when it happened, hopefully I managed to come down safely.

What gear do you climb in? What year truck?

Front driveshaft is limited to 5,000 rpms so max speed is about 44-45 mph in 4th, 5th and 6th with TC in 4LO. In 3rd you might get her up to 35-36 mph, you just don't want to bump the rev limiter and have the computer cut power on you. Of course, you could always get a custom tune and raise the rpm limit.

Edited January 4, 2020 by swathdiver

14BFF · January 4, 2020

DBW rev limiter can be tuned to be like LS rev limiter. You just need to find the correct tuner.

And yes the stock limiter is very bad in dune climbing and drifting as well.

Sent from my ONEPLUS A6013 using Tapatalk

Justin_R · January 5, 2020

23 hours ago, swathdiver said:

What gear do you climb in? What year truck?

Front driveshaft is limited to 5,000 rpms so max speed is about 44-45 mph in 4th, 5th and 6th with TC in 4LO. In 3rd you might get her up to 35-36 mph, you just don't want to bump the rev limiter and have the computer cut power on you. Of course, you could always get a custom tune and raise the rpm limit.

Thanks for the comment!
2016 Z71 LT Silverado, 5.3L crew cab.

I usually climb sand dune hills with first great + high 4x4

Thanks! I will look more into the tuning option

Edited January 5, 2020 by Justin_R

Justin_R · January 5, 2020

9 hours ago, 14BFF said:

DBW rev limiter can be tuned to be like LS rev limiter. You just need to find the correct tuner.

And yes the stock limiter is very bad in dune climbing and drifting as well.

Sent from my ONEPLUS A6013 using Tapatalk

Thanks for the reply!
Yeah it is bad and thought there would be an easy way around it. Thanks for the feedback I will look into the tuning option and see how far I can go with it, I really want to get it sorted out!