Id think that with 430whp you'd already be over 500 crank easily.

 

Do you degree a VVT cam in when installing?

 

A few years after its inception this is still pretty new territory with a lot of question marks. I definitely want to cam my L9H, this thread has been very informative.

 

Hicksport,
Did TSP lower your max RPM concidering you have the stock L92/LY6 solid intake valves V.S. hallow stem LS3s?

 

We always check them, same as the non-VVT camshafts. The downside is that it is more difficult to check VVT clearance as compared to the old technology.

 

Seeing as no one seems to really yak about this I might as well offer up where Im at with it. Clearly the VVT application itself is simple. Advance to the max at low RPM for bottom end torque and retard to the max at the top end for max high RPM output. The thing I dont have time to do and was hoping someone would ( I find myself here too often these days *sigh* ) Anyways the thing I dont have time to do is calculate out the factors that contribute to cyl pressure/vacuum at specific RPM points and then multiply the parameters over my cams intended RPM range. At least this is where I was going to start but seeing as its mid summer and I have only had three or four hours sleep in 5 days because Im so busy working? I think WHEN I actually get to it my VVT curve is going to look something like this;

1000RPM: 20 degrees advance +4 cam in the grind
3000RPM: 15
4000RPM: 10
5000RPM: 5
5500RPM: 0

Then I'll drive it to the dyno and start playing. The only major drag is how drastically "playing" with the valve timing will impact the a/f spark as well so its gonna be painful.

This info is coming out anyways so I dont see the logic in holding it back, It only prevents some of us from buying your ****

 

This is what I got with a no vvt cam swap LY6, dynatech longtubes and through a 4L80e which robs lots of power on the dyno. The same cam in an LS3/t56 camaro made over 470 at the wheels.

Here is the cam:

Vengeance Racing Stage II LS3/L92 Camshaft 227/239 .614/.624 115+3

I did the chain, double springs and pushrods as well.



I wanted to keep vvt, but noone would post their curves or proof that it is superior. I didn't exactly give up on torque either.

VVT guys:
If VVT on a fixed exhaust, intake driven cam is better, prove it!

 

Well... The fastest all motor stock cube 6.2L runs VVT so...

Besides that I think the point it seems most miss about VVT is not peak hp its power under the curve. All things being equal ( same lift/duration.lobe ctr etc ) if you ran two identical cams one with VVT and one without in the exact same engine the VVT cam will produce more power in areas where the static cam will not. For instance obviously if your grind peaks at 7000 RPM then VVT is not going to make much difference at 7000 RPM but... where the peaky cam sucks down low say around 2500-4500 the VVT will help a LOT and give you more grunt.


I dont quite get your point about fixed exhaust intake driven? What exactly are you referring to here? The cam is fixed in its grind that does not change with these types of VVT cams. All the changes is the advance or retard ( cam timing ) and that it can be controlled on the fly. So in your case that +3 you have ground into your cam to try and make the bottom end a little better? Well with VVT you can have +23 and to make it better you can retard it to your liking up top. This is the only thing that VVT in these engines does and it makes a difference. Granted its not "massive" but its there so why not use it?

Now as for them independently variable VVT systems on Fords new engines and whatnot.... Just look at the results there. VVT is here to stay so ditching it is just losing out a bit is all. Its not like your engine wont run great without it its just that it will run a little faster and harder with it. Thats it


BTW sorry TSP for outing you earlier I had a few pops and hadnt been laid in over a week. All good now

 

What are you referring to?

The problem is that all things are not equal. Most of the VVT cams available compromise on lift compared to non-VVT counterparts, assumably to prevent valve-piston interference.

The only exception that I've heard of so far are the TSP cams which seem to run more lift than similar duration VVT cams offered by Comp or Mast. You can find links to the dyno performance for a TSP cam in an L99 somewhere higher in the thread. I have not compared it directly with a similar duration non-VVT cam, but I would have to assume the performance would be better in some areas of the curve.

Until TSP recently released their ballpark specs for their VVT cam offerings, I was very disappointed by the VVT cam offerings having 0.030-0.040in less lift than most similar duration aftermarket non-VVT cams. IMO that is too much of a sacrifice in lift.

I am pretty sure he's referring to the fact that the intake and exhaust timing can not be varied independently in the LSx VVT system.

 

While PtoV may be an issue with VVT cams, the other factor may be DoD. In some cases, the two are used together. I have a 6.0L that is DoD and VVT. There are limitations around the DoD lifters which limit gross lift.

In a VVT motors I think everyone is just trying to figure out how much the cam phaser will put up with. Running higher lift cams with more spring pressure is the area of concern. Going with a slightly softer lobe and sacraficing .030 really isn't a big deal. If you put toomuch spring on it, then the phaser won't work properly, and you don't end up with VVT anyway.

People get hung up on duration or lift. Don't... Think of it as area. If you aren't geting the lift, you can trade it off for duration, or vice versa and get the same area.

I think a lot of people get hung up on a gross lift number and never consider things like the ammount of variance a ground can have. People argue over 2º never considering their cam might vary 2º based on the way it was ground. Folks don't seem to consider the ammount of pushrod deflection they get. So again, don't get hung up on just one number.

For a VVT cam I would take a much different tack in designing the cam than I would for a conventional non-VVT engine. Since you can retard the camshaft20 degrees I would plan my camshaft events around what I could do with that ammount of retard to maximize power across my selected RPM range.

 

Bandit was accurate in summarizing my thoughts.

I agree with you that vvt is here to stay. I disagree with you about the power under the curve that vvt provides on ls engines. Did you look at my torque curve and where it starts? At 2600 rpm we floored it on the dyno and instantaneously produced near peak torque which stayed flat. I compared this with Mast and Comp vvt cam dyno sheets and I made more power everywhere. I have yet to see results from the TSP cam, but judging by Hick's numbers, I made more power than him as well, since I'm running a 4L80e. I really wish some guys running their vvt cams would post their dyno results. Vengeance predicted these results and required dual valve springs with this cam.

I’m sure that there is some benefit to fuel mileage in running a vvt cam in an ls, but there appears to be no evidence that vvt produces higher engine output at any engine speed, in an ls application, until someone can develop or prove otherwise.

The dual overhead cam engines that can vary intake and exhaust valve timing independantly also have 2 to 4 times the number of phasers to overcome spring pressure if this is really an issue. Many of them can vary lift and duration as well, which is an even greater benefit. I’m sure I would never ditch vvt on an engine like this.

 

futureuser, if you could put that exact same grind on a phaser AND have it work, there would very likely be more area under the curve. It's unlikely the cam advance ground in and fixed into the cam is ideal for all RPMs. The problem is that cam isn't availble for VVT. Whether that's a phasor overcoming spring pressure issue or what, I have no idea. That was partly what I was tryin to ask in the very beginning of the thread. Why / how do the VVT cam grinds need to be different? Do they have to be less agressive so the phaser can operate? Is the adjustment range too wide to prevent P-V interference? Or are they just not being offered for some other reason?

 

Is this true or is this a myth? Does the phasor actually have problems controlling the cam timing when subject to higher spring pressures? If so, could this be remedied by running higher oil pressure?

 

I agree with you. I didn't mean to compare the same cam with or without vvt. I was trying to compare aftermarket vvt cam to non vvt cam packages. I have the same questions as you.

I checked out the links to the texas speed vvt3 cam results and I am impressed. It seems that it would be comparable to my cam if it was in an L99.

 

Check out this...picked up nearly 4 mph in the qtr and dropped 3 tenths with VVT.

http://www.highperformancepontiac.co...ers/page2.html

 

I read the article and it says he turned the vvt on with a switch, as in he disabled it, initially. I'm sure there would be a detriment to disabling vvt with a vvt cam. Its not the same as comparing an aftermarket vvt cam to an afternarket non vvt cam.

 

I understand what you're suggesting, two identical engines one with vvt one sans vvt. The problem with this comparison IS cam selection. You're making the assumption that both cams selected are ideal (perfect) for that engine.

However, the article clearly shows the power made with the same cam, same head flow, same compression etc etc is more than without.

 

I think I agree with you. My argument is same engine, one with optimized vvt cam set up, one without. The grinds are different, the tunes are probably different.

Bandit, I just reread your first post and I realize I have almost singlehandedly hijacked your thread. Sorry.

 

THIS^

I think this is exactly where we should be pouring our thoughts into. For instance back up the clock on early LS1 cams where they borrowed lobes from sbc grinds and yeah sure they worked but as time went on all sorts of new lobes were developed that worked much better for LS engines than those old lobes ( not to mention easier on valvetrain ) and took advantage of the larger base circle etc. So considering previous LS cam development and looking at VVT progression I think the hardest thing ( at least for me ) to wrap my head around is how to maximize returns on cyl pressure at given cam timing vs cam specs themselves. It is a whole hella lot more complex when you start think about RPM vs event timing AND then figure out whats the best lift/duration etc. There is a wealth of knowledge to be gained here and I guess what Im curfluffled about is why there are so many naysayers when this advantage seems to have obvious benefits.

As for the fuel mileage comment above? While GM uses VVT to minimize pumping losses mainly and this does benefkit fuel mileage by timing the valve events such that you only keep as much cyl pressure as absolutely nec so the engine "spins" easier thereby reducing parasitic losses BUT... Think about it. If its that easy to make it spin easier then turn the tables and make it spin the absolute MOST cyl pressure you can and watch the power turn up. So in a sense I would have to think that a properly tuned VVT set up will probably get worse fuel mileage than a static cam if you maximize the pressures for returns. I guess you could always make it so at cruise speeds etc the VVT tables are different but Im not sure if the tuning suites are capable of this much control yet.

Anyways certainly interesting discussion and I at some point in this life will be posting results from my EPS VVT cam. Too much work and too many hotties I just cant do it all

 

Not at all. This kind of discussion was exactly the reason I started the thread.