Lets Clear up some VVT myths.....

[Rhino79]

Ok guys, here is the story that sparked me to post this thread.....

We had a customer drop his car off for a Whipple install, cam install, and a zl1 pump and of course dyno tuning.

He had already ordered his parts online.

The company he bought his parts from sold him an ls3 conversion kit and basically said vvt was crap and it would make noises, and that they always do ls3 swaps on the l99s. They also sold him a melling pump that flows less than the stock l99 pump as well.....

I truly car about the finished product, if I didn't I would just have swapped parts, tuned it and sent him down the road. BUT that's not who I am.

I called him, and spent about 25 mins on the phone with him, explaining the facts about afm and vvt. Sure everyone knows afm is junk. I agree totally. But the VVT is a great advantage! I told him it was my job to make sure he is happy with his car, and I want to build him the best product I can, but it will take maintaining the vvt. So after talking, we decided to get him a custom grind VVT cam for his whipple setup.

Look, vvt is simply on the fly cam degree-ing. Its not a bunch of smoke and mirrors. It doesn't make any noise that an ls3 wouldn't make. It uses a hydraulic phaser (cam timing gear), to move the cam centerline during operation to optimize the ENTIRE power curve.

All of the desired cam position is controlled in the calibration file.

At idle the phaser is fully parked (fully advanced). As engine rpm increases and depending on the cam specs, you will be able to start retarding the cam to help upper rpm power, and to carry power past peak better.

Now what is wrong with being able to degree a cam, on the fly?

GPI is a performance division of a dealership. Look we see tons of vehicles come through for all types of repairs, and since the Phaser was introduced on the LS engines, I have not seen 1 failure. I have made an unbelievable amount of track passes, dyno runs and everything in between. My rev limit is 7600, and I shift around 7000 rpm.

SO,
VVT is NOT noisy, its just a hydraulic actuator
VVT is NOT problematic.

VVT IS more versatile and smaller grinds vs their ls3 rivals can make equal or better power.
VVT IS the future. New vettes, new truck, new cars. Period. Actually we will have variable ratio rocker arms before too long....

Its not just for EGR, and the only reason to NOT utilize it is if your tuner doesn't know what he is doing, or if they don't understand what cam degreeing is. At either point, its time to find a competent shop to perform your work.

Let me know if you guys have any questions.

Ryan

[flyer08]

Thank you rhino. Need more tuners like you. Took a while to find a tuner in my area that wanted to do a VVT install and not direct me to ls3 conversion.

Now I just need to talk to you about the 7k shifts before I hit up the track Saturday with my tuner

[Rhino79]

No problem man. Sure its relatively new to the LS cars, but GM spent a lot of time and money developing it and even putting it in the all new LT1. Its the best of both worlds for sure.

[Supercharged SS]

Can you please explain the advantages/disadvantages of using a VVT cam with FI?


Thank you.

[Rhino79]

Just like with any other setup, being able to move the centerline around to make more power over a wider range.

Lets say you have a cam that's on a 108 icl and one that's on a 112 icl. Of course the 108 would make better lower rpm power and most likely more in the mid range, where the 112 icl will make better power up top.

So with aftermarket vvt setups you have 20* of retard with the phaser limiter installed. So basically you can have a cam that may be installed at 108 for example and have the ability to pull it back up to 20* to find out where it makes and carries the power best at.

I will make multiple dyno runs with the Phaser on the whipple car fixed at full advance (installed centerline), the I will retard it 2*, and make a pull, 2 more degrees and make a pull and I will be happy to post the graphs to illustrate how just a few degrees of centerline change can make nice gains in power.

[white ZL1]

Originally Posted by Supercharged SS

Can you please explain the advantages/disadvantages of using a VVT cam with FI?


Thank you.

Somewhat ignorant here, but me thinks it would be exactly the same as N/A?
I'm sorta interested in seeing how the additional low end torque that you should be able to dial in would work with any of the centri blowers.

Hey Rhino....how about laying a graph of no vvt tuning over one that is optimized so folks can see the difference?

edit: wow, reading my mind and beat me to the punch

[Supercharged SS]

Originally Posted by Rhino79

Just like with any other setup, being able to move the centerline around to make more power over a wider range.

Lets say you have a cam that's on a 108 icl and one that's on a 112 icl. Of course the 108 would make better lower rpm power and most likely more in the mid range, where the 112 icl will make better power up top.

So with aftermarket vvt setups you have 20* of retard with the phaser limiter installed. So basically you can have a cam that may be installed at 108 for example and have the ability to pull it back up to 20* to find out where it makes and carries the power best at.

I will make multiple dyno runs with the Phaser on the whipple car fixed at full advance (installed centerline), the I will retard it 2*, and make a pull, 2 more degrees and make a pull and I will be happy to post the graphs to illustrate how just a few degrees of centerline change can make nice gains in power.

Thank you. What about vvt vs the ls3 conversion? Is one going to out shine the other?

[Rhino79]

If you have 2 cams, exact duration, exact lift, exact same lsa. The vvt will make better average power and do it over a wider range.

[Supercharged SS]

Originally Posted by Rhino79

If you have 2 cams, exact duration, exact lift, exact same lsa. The vvt will make better average power and do it over a wider range.

Gotcha!!

[Camarojt]

Here is a question I have. I have heard that the limitation to a VVT cam is the fact that you can't go as big as you could go with a conventional LS3 conversion. So what you gain in the ability to retard the cam up top, you lose with size limitations?

1) is this a true statement?

2) id also like to see a dyno comparison of a VVT and LS3 conversion cam.

I've always been a big fan of VVT!

[Rhino79]

If someone here has a ls3 conversion that wants a vvt cam, I will be happy to swap it at a discounted rate, to offer up some comparison.

If there is a size limitation of vvt, I haven't seen or experienced it. I run Brian tooleys Extreme springs, and while Im not going to give out my exact specs, my duration is bigger on both lobes than the mast ss, and lift is approaching mid 600s.

When retarding the cam, you are losing exhaust ptv clearance. The l99 has huge valve reliefs and even a large cam such as mine at full 20* retard, still has ample clearance. So the only limitation really is intake ptv, which I solved by flycutting. And that's only an issue on a large cam like mine. Anything smaller would clear just fine.

[white ZL1]

Sooooooooooo tempting. A nasty vvt cam and some TFS heads would be interesting.

[Rhino79]

Indeed it would!

[SPCBA]

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