[ryanryan]

Just curious since they seem to be the cat's meow in the OEM world, and all that new technology usually becomes popular in the drag racing world. Wouldn't it help a lot with spool-up off the line? And you could even use it to slow you down at the end of the run!!!

 

[JOHNBOY66]

Just curious since they seem to be the cat's meow in the OEM world, and all that new technology usually becomes popular in the drag racing world. Wouldn't it help a lot with spool-up off the line? And you could even use it to slow you down at the end of the run!!!

Does the OEM use the VVT for better spool up?
No. They use it for better control. Boost control is integrated right into the ECM. This gives the engine calibration nerds more control over the turbo. A very good example of this is the truck in your avatar. The VVT is used at cold weather start to help the engine heat up quicker. Engage the high idle function. When the outside temps drop to below 32F it will raise the idle in Park and close the VVT up. This creates more restriction and therefore heat. Your truck will heat up much faster.

Another reason for VVT is emmissions. The added pressure of the VVT really help propagate EGR flow because of the pressure it can add. This allows the engine to run a more performance oriented cam profile.

The real problem for VVT in a race set up is IMHO that while it can help with spool up once your spooled your flow is hampered by the VVT vanes. As a good buddy says. "Once spooled you just wish that shit would get the hell out of the way"

 

[Fryguy302]

VVT basically makes the powerband wider....which is great on a street car, but not necessary on a drag car. Drag cars with the correct gearing and torque converter or clutching can get down the track in a narrow RPM window.

 

[buick-lsx]

On tech it's been said that the vvt lifters can't stand the added pressures from boost and the stronger valve springs needed...

 

[JOHNBOY66]

On tech it's been said that the vvt lifters can't stand the added pressures from boost and the stronger valve springs needed...

I believe the VVT the OP is referring to is Variable Vane Turbo. I think your thinking of Variable Valve Timing.

 

[buick-lsx]

I believe the VVT the OP is referring to is Variable Vane Turbo. I think your thinking of Variable Valve Timing.

You are correct lol, thanks

 

[Fryguy302]

I believe the VVT the OP is referring to is Variable Vane Turbo. I think your thinking of Variable Valve Timing.

lol, sorry that's what I was thinking he was asking about also.

 

[YFU Racing]

because it would get outlawed a year later

 

[GrannySShifting]

On tech it's been said that the vvt lifters can't stand the added pressures from boost and the stronger valve springs needed...

Theres nothing different about the lifters. The VVT mechanism is a plunger in the cam bolt in LSx engines that moves the clocking on the cam sprocket.

I actually have started working on using it in a turbo application, to advance cam a bunch to aid spoolup. Working out control algorithm specifics. Found someone to write/make the hardware up.

 

[LilJohn]

The small displacement guys are seeing good results from some units like the HE351VGT holset unit. It seems it takes them some time to figure out how to control the VVT. they arent seeing bigger hp numbers but the numbers down low are staggering. Friend has one on a 2.3 ford and it made 50 more horsepower from 3400-5500 and the average numbers were way way better. Made his Thunderbird fun to drive on the street again.

 

[bamared]

the VVT on the turbo's is relative to variable inlet guide vanes on a turbine engine. changes the angle of attack of air going to the compressor. the lower demand from the engine, the angle is grater, and the more demand from the engine the vanes move for less angle. and yes, i agree about a street strip car being a more practical application. That is until they produce a turbo with a compressor " cold section", with a set of blades behind it compressing that air even more. only time will tell

 

[ryanryan]

Does the OEM use the VVT for better spool up?
No. They use it for better control. I know they don't use it just for better spool up, but it sure as hell helps. A very good example of this is the truck in your avatar. The VVT is used at cold weather start to help the engine heat up quicker. Engage the high idle function. When the outside temps drop to below 32F it will raise the idle in Park and close the VVT up. This creates more restriction and therefore heat. Your truck will heat up much faster. I'm well aware of the elevated idle function on my truck and how it works. I love it on the cold mornings!!!

The real problem for VVT in a race set up is IMHO that while it can help with spool up once your spooled your flow is hampered by the VVT vanes. As a good buddy says. "Once spooled you just wish that shit would get the hell out of the way"
I figured that may be a problem, but I didn't know how much it would effect the flow.

And yes, I am taking about variable vane turbos.

 

[bamared]

i would think that if the VVT affected the flow, they would just change the profile of the compression and housing to make up for the restriction. correct? I cant see it hurting performance for what its designed for.

 

[ricer]

more importantly why hasn't direct injection hit the racing world yet....everything you read that is the latest/greatest thing and sounds very interesting................sorry for the hijack, back to VVT

 

[GrannySShifting]

It has. Drag racers are just in the neanderthal stages of adopting new technologies it seems at times. Why NASCAR and Prostock still uses carburetors is beyond me.

Everywhere else practically you can find DI with hundreds of bars of rail pressure

 

[TiAL]

It's because the vanes can't take the EGT's of gas engines (aside from the 997 turbo - the only gas car to have it)

 

[Blaine B.]

It's because the vanes can't take the EGT's of gas engines (aside from the 997 turbo - the only gas car to have it)

And what a car it is both stock and stage 3

 

[SuperCooper]

It's because the vanes can't take the EGT's of gas engines (aside from the 997 turbo - the only gas car to have it)

I would agree with that but maybe it would be clearer this way: you could make vanes that would take the heat, but it is very difficult to have vanes that live AND still actuate with no lube in such a harsh environment.

The existing VGTs are having enough trouble as it is staying more or less trouble-free (with regards to actuation) with lowish EGTs.

Someday I think VGT will be more commonplace in the racing world, but we ain't there yet.

One other thing mentioned earlier, the efficiency of the turbine hits a wall and once you push past that, it just drops like a rock. You have to stay within its sweet spot.

Hope this helps.

 

[slow67]

I like Holset's version of it, they call it VNT. Many fewer moving parts.