Understading VVT

[swathdiver]

VVT is designed to move into the parked position if there's a failure.

VVT makes the motors more fuel efficient, the 5.3s picked up a solid mpg over the non-VVT motors. The 6-speed didn't do much of anything to increase fuel efficiency according to Fuelly.

 

[Foggy]

I might be in the minority here but I can't wait to get rid of the vvt in my truck. I hate how jerky it makes low rpm driving and I find it does nothing to help low end torque. It just seems like a solution in search of a problem to me.

Nope.. Have never felt anything in VVT system in many trucks I've driven.. Have never
noticed it in my 6.2 with either camshaft...
You are probably feeling the DOD/AFM and the torque converter if it's totally stock.
I don't think anyone could "feel" VVT even if you tried

 

[donjetman]

can anyone else feel theirs? I do have a odd by tranny in the yukon that might be hiding it?

No
I have 1 LS powered vehicle with VVT, and 2 LS powered vehicles without.
No

 

[j91z28d1]

No
I have 1 LS powered vehicle with VVT, and 2 LS powered vehicles without.
No

yeah, I think foggy is right and he's feeling afm. is so bypassing that is a good idea

 

[donjetman]

I have 1 vehicle w/an afm engine but its been tuned out.

 

[Charlie207]

I might be in the minority here but I can't wait to get rid of the vvt in my truck. I hate how jerky it makes low rpm driving and I find it does nothing to help low end torque. It just seems like a solution in search of a problem to me.

I don't think there is a huge benefit to VVT with a single cam, when a good tune and headers produce 2-3x more usable power.

Or, gaining displacement.

Once the engine starts utilizing separate intake & exhaust cams do variable timing benefits really become evident, which is tricky on an LS.

I can speak with experience about two different OHC V8s, a 32v 4.4L from three different E39 BMWs, and a lovely 32v 5.6L out of a 1st-gen Nissan Armada.

The BMWs were all 6-speed manuals, so it was easy to always be in the right power and, but they could smoke the tires from a dead-stop, and would truly pull like a flaming cat with gasoline dripping down it's back. The revhlimiter would hit quicker than you'd expect.

The VK56 out of the Nissan always felt like it had max grunt at 1000rpm, and the traction control was always blinking when the roads were wet, even at 23x,*** miles. I wish I had the time & space to swap that VK56 into a Frontier 2wd.

I find my LS to be strong and smooth, and very predictable, but it feels like it needs a split-second to unleash its power, whereas the DOHC engines had hair-triggers. I attribute this to all those intake and exhaust cams able to adjust the breathing to the max.

There's only so much phasing available with a single cam, and we've seen how you even lose some of that range when upgrading VVT cams.

 

[j91z28d1]

my experience with ls engines is they are always laggy and I don't really know why. I don't believe it's the single cam.

I don't count anything auto cause they kinda have to be mushy, Lotta things going on in there but I've owned a few ls in manual cars, both cable throttle and fly by wire throttle. none of them had/have vvt or afm, the cable is better, but still not crispy like a old school v8. I have not driven one on a stand alone ecm, they might be good and it's just how gm codes the stuck ecm? but I've driven many different tuned and bone stock ls cars thru the years and all just feel a bit mushy compared to what a old small block chevy or even a old pushrod Ford 5.0. even old carbed v8's are nasty like that when tuned well with decent compression.

all those are single cam in block. so I don't blame a cam, especially a small one for low end.


end of the day they all run the numbers and go faster but I've always found it a bit odd. I have a guy that works in the shop next door that's always got his eye out for a 57 chevy at a good price. so he talks to the restoration shops and stuff. he tells me the market for non ls swapped classics is pretty bad. noticeable differences in how quick they sell and level of interest. I just don't get it. why would you want to cruise around a old classic car with a laggy ls in it. you lose all the character.

blah.

 

[Noggles]

Nope.. Have never felt anything in VVT system in many trucks I've driven.. Have never
noticed it in my 6.2 with either camshaft...
You are probably feeling the DOD/AFM and the torque converter if it's totally stock.
I don't think anyone could "feel" VVT even if you tried

I feel something that changes around 2500ish rpms at part throttle and I know its not dod/afm because this is when I am taking off from a stop and its not the torque converter locking because its not an rpm drop. Plus I think the converter locks during the 2-3 shift and this happens in every gear at the same rpm. It honestly feels like the cam timing change my old 5 cylinder Colorado had with its variable vale timing and also like the Honda vtec engines I have been around. If what I am feeling isn't the vvt then I probably need to look into it further but I am pretty certain it is. My truck is a 5.3 but my dad has a 2013 6.2 Denali and I am curious if I can feel it in his as well so I will go drive it as well.

my experience with ls engines is they are always laggy and I don't really know why. I don't believe it's the single cam.

I don't count anything auto cause they kinda have to be mushy, Lotta things going on in there but I've owned a few ls in manual cars, both cable throttle and fly by wire throttle. none of them had/have vvt or afm, the cable is better, but still not crispy like a old school v8. I have not driven one on a stand alone ecm, they might be good and it's just how gm codes the stuck ecm? but I've driven many different tuned and bone stock ls cars thru the years and all just feel a bit mushy compared to what a old small block chevy or even a old pushrod Ford 5.0. even old carbed v8's are nasty like that when tuned well with decent compression.

all those are single cam in block. so I don't blame a cam, especially a small one for low end.


end of the day they all run the numbers and go faster but I've always found it a bit odd. I have a guy that works in the shop next door that's always got his eye out for a 57 chevy at a good price. so he talks to the restoration shops and stuff. he tells me the market for non ls swapped classics is pretty bad. noticeable differences in how quick they sell and level of interest. I just don't get it. why would you want to cruise around a old classic car with a laggy ls in it. you lose all the character.

blah.

I think what causes this is the weight of everything in the driveline. I put a lighter flywheel in my ls1 trans am and it made a significant difference. Most ls vehicles are auto with a big heavy locking converter and heavy flexplate so there's a lot of mass to turn there. Plus there is a small delay in throttle response because of all the electronics versus a vacuum operated carb that opens and air and fuel goes in.