VVT Cams
10-26-2011, 04:44 PM
#201
1) VVT-"friendly" lobes have compromises like slower ramp rates or lower lift, thereby putting VVT cams at a disadvantage
2) VVT-"advantaged" lobes are designed differently to take advantage of the VVT feature, thereby putting them further ahead than nonVVT lobes that have simply had VVT phasing enabled
Seems to me like the jury is out on whether we're talking 1 or 2. Maybe TSP can answer.
10-26-2011, 05:22 PM
#202
6600 rpm clutch dump of death Administrator
That logic only works if the VVT cam has the same lobes as the nonVVT cam. If they are different there are two possibilities:
1) VVT-"friendly" lobes have compromises like slower ramp rates or lower lift, thereby putting VVT cams at a disadvantage
2) VVT-"advantaged" lobes are designed differently to take advantage of the VVT feature, thereby putting them further ahead than nonVVT lobes that have simply had VVT phasing enabled
Seems to me like the jury is out on whether we're talking 1 or 2. Maybe TSP can answer.
1) VVT-"friendly" lobes have compromises like slower ramp rates or lower lift, thereby putting VVT cams at a disadvantage
2) VVT-"advantaged" lobes are designed differently to take advantage of the VVT feature, thereby putting them further ahead than nonVVT lobes that have simply had VVT phasing enabled
Seems to me like the jury is out on whether we're talking 1 or 2. Maybe TSP can answer.
That being said, you take a VVT cam and install it straight up, its going to make X hp. Retard it, and you are going to loose power down low, and pick up power up top. Its engine 101. So, VVT or non VVT is irrelevant in that regard.
If there are limits on ramp acceleration, and lift, you can take that into account in the lobe slection and trade it for duration as an example.
10-26-2011, 06:12 PM
#203
That logic only works if the VVT cam has the same lobes as the nonVVT cam. If they are different there are two possibilities:
1) VVT-"friendly" lobes have compromises like slower ramp rates or lower lift, thereby putting VVT cams at a disadvantage
2) VVT-"advantaged" lobes are designed differently to take advantage of the VVT feature, thereby putting them further ahead than nonVVT lobes that have simply had VVT phasing enabled
Seems to me like the jury is out on whether we're talking 1 or 2. Maybe TSP can answer.
1) VVT-"friendly" lobes have compromises like slower ramp rates or lower lift, thereby putting VVT cams at a disadvantage
2) VVT-"advantaged" lobes are designed differently to take advantage of the VVT feature, thereby putting them further ahead than nonVVT lobes that have simply had VVT phasing enabled
Seems to me like the jury is out on whether we're talking 1 or 2. Maybe TSP can answer.
But in a VVT ONLY application you can run whatever lobe you want
BTW its running now
10-27-2011, 10:42 AM
#204
6600 rpm clutch dump of death Administrator
I took the two graphs and showed roughly what you would see if you take the best points of advancing and retarding the cam. If you look at the curve, you can see that it is fatter, so you have better average power across the board, and you pick up across the board.
10-27-2011, 10:52 AM
#205
Thanks for the graphs J-Rod I think I'll target some of those RPM specifics when I get to tuning this thing so at least I have some starting point rather than run and gun and watch the results.
Im just waiting on some parts now and then the tuning process begins so I should have some numbers for my set up soon.
In case anyone is wondering its a stock 07 L92 6.2L with an uported LS3 intake running the 87mm truck TB though 1.75" SW headers, 2.5" Y and a single 3" exhaust in front of a t56. Its a PatG spec'd custom grind EPS VVT street cam. Nothing crazy but hoping to make good numbers. I'll be posting results as soon as I have them
Im just waiting on some parts now and then the tuning process begins so I should have some numbers for my set up soon.
In case anyone is wondering its a stock 07 L92 6.2L with an uported LS3 intake running the 87mm truck TB though 1.75" SW headers, 2.5" Y and a single 3" exhaust in front of a t56. Its a PatG spec'd custom grind EPS VVT street cam. Nothing crazy but hoping to make good numbers. I'll be posting results as soon as I have them
11-12-2011, 01:04 PM
#207
But regardless in the meantime Im going to push forward with the tune and get it more responsive as right now its a bit confused down low and seems to hunt for the correct timing ( assuming both cam and ign ) before it takes off. I can say this sucker has TON of torque.... A hella lot more than my TR224 LS1 ever had
My guess is having the comp phase limiter in there and still running stock timing on both cam and ign is messing it up so Im going to attempt to sort it even if I only have 4000 RPM to play with today.
11-12-2011, 03:18 PM
#208
Well to say my own guesstimations made an improvement is an understatement lol. First off to keep it easy I zero'd out the variable cam ign timing table. It might be beneficial so I'll play around with it later but for now Im trying to simplify things and get this thing running better. After zeroing that table out now all thats left is the cam phase itself which is ALL over the place in stock form. You can see its really not there for power its there for mileage as it has this plume shaped tables with wide advance/retard variances to let the engine pump easy at cruise speeds but meh dont need that so out she goes. Just with these changes it already feels a lot more powerful now. Note the cels represent timing retard. My cam has +4 advance ground into it so Im running 8 degrees of cam retard by 5600 RPM and I gradually roll it up in 2 degree increments starting at 4000 RPM
Heres what I did to all three boards of VVT timing. Going to work though ign timing now
Heres what I did to all three boards of VVT timing. Going to work though ign timing now
11-17-2011, 03:42 PM
#210
Got the rev limiter sorted and have added more to the cam phase and ign timing with excellent seat of the pants results. I start rolling the phase into retard at 3600 RPM now and Im at 10 degrees max retard by 5600 RPM. Bumped the cam ign timing back on and added in small amounts. Raised high oct ign timing by a couple of percent from 3200 RPM+ and made a very noticeable gain. I think Im going to leave things as they are now until I hit the dyno so I can do some sweeps and compare numbers but I can feel theres lots more in it yet. It still feels like its breathing pretty effortless. Safe, but far from MAX power
11-20-2011, 12:42 PM
#211
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LS in a JK We have a 2010 Cadillac Escalade engine we are putting in a Jeep, it has VVT and AFM/DOD.
We are looking into a different cam for more power any ideas, we are new to the LS world. thanks for the help.
We are thinking of getting rid of the AFM/DOD
We are looking into a different cam for more power any ideas, we are new to the LS world. thanks for the help.
We are thinking of getting rid of the AFM/DOD
06-01-2012, 02:46 AM
#214
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Still havent made it to the dyno for a professional tune but running on the strip with my own homebrew tune got me a best of 13.1@113mph with 2.1 60ft for the first time out. Need to figure out this launch with the t56 its a bit trickier then with an auto. Running 275/60R15 et streets and truck weighs 3850. Should be easily in the 12's with some launching practice.
06-03-2012, 11:49 PM
#215
Still havent made it to the dyno for a professional tune but running on the strip with my own homebrew tune got me a best of 13.1@113mph with 2.1 60ft for the first time out. Need to figure out this launch with the t56 its a bit trickier then with an auto. Running 275/60R15 et streets and truck weighs 3850. Should be easily in the 12's with some launching practice.
08-09-2012, 02:48 PM
#216
I have been learning more about the VVT-2 cam that I have and thought I would share. I know this erodes at the secrecy surrounding the TSP grinds, but with what I've learned I would say there really is no big secret to this grind. The cam specs were on the card delivered with my cam and I obtained the lobe numbers from Comp with very little work. The grind uses LSL lobes and the specs are 227/235 .614/.621 113LSA+6 (107ICL). This cam is identical to the 277LR 3-bolt camshaft (54-458-11) that has been out for a couple of years, with the exception of being 2 degrees more advanced (107 vs 109 ICL, assumably to take advantage of the VVT). If you were to install this in your VVT engine and command it to have 2deg of retard, you would have the same cam specs as the 277LR. This is nice information to have because there are a lot more 277LR cams installed out there and even some magazine articles involving that grind to look at for comparison. For example, this article predicts a healthy 550hp at the crank using the nonVVT version, L92s and flattops on a 6.0: http://www.hotrod.com/techarticles/e...t/viewall.html
I have also read reports of low speed driveability sacrifices with the nonVVT 277LR, which the additional 2* advance in the VVT-2 might help with. What that article above points out is the piston-valve clearance with flat tops may be marginal withthe nonVVT cam and I'm sure it can only get worse with the added advance of the VVT-2: definitely check your PTV clearance if you install this cam (or any cam really).
Here is another article using the 277LR on a stroker: http://www.carcraft.com/techarticles...d/viewall.html
Another note, in the newer catalogs for single bolts cams, there is a 277LrR single bolt cam (146-458-11) which has more exhaust duration and slightly more exhaust lift for the rectangular port heads. The 277LR cam (54-458-11) was designed for cathedral port heads, though the difference is subtle.
Hopefully this helps others trying to make a camshaft choice.
I have also read reports of low speed driveability sacrifices with the nonVVT 277LR, which the additional 2* advance in the VVT-2 might help with. What that article above points out is the piston-valve clearance with flat tops may be marginal withthe nonVVT cam and I'm sure it can only get worse with the added advance of the VVT-2: definitely check your PTV clearance if you install this cam (or any cam really).
Here is another article using the 277LR on a stroker: http://www.carcraft.com/techarticles...d/viewall.html
Another note, in the newer catalogs for single bolts cams, there is a 277LrR single bolt cam (146-458-11) which has more exhaust duration and slightly more exhaust lift for the rectangular port heads. The 277LR cam (54-458-11) was designed for cathedral port heads, though the difference is subtle.
Hopefully this helps others trying to make a camshaft choice.
Last edited by -TheBandit-; 08-09-2012 at 04:54 PM.
08-09-2012, 03:59 PM
#217
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Thanks so much man! Thats pretty badass and its nice to finally know what I have for comparison sake, Hope you dont get any **** for it, watch out for guys in black suits coming after you! 107icl is kind of extreme for a street car dont you think?
08-09-2012, 04:10 PM
#218
The black suits are on their way I'm sure. I feel bad disclosing this considering the great service I've had from TSP but I honestly think it only helps them for customers to be informed.
I think you may be confusing ICL (intake centerline) with LSA (lobe separation angle). A 107*ICL is not out of the ordinary and the VVT will change it. For example, at 2* retard, the ICL will be 109*, matching the LSR277 cam. At 4* retard, the ICL would be 111*. That's the nice thing about VVT - you can change the cam's performance on the fly by modifying the timing of the valve events.
On another note, when you see something like "113+6", that means the LSA is 113 and the cam is advanced 6 degrees such that the ICL is 113 MINUS 6 = 107.
With VVT the VVT-2 cam can be 113+6, 113+5, 113+4, etc etc.
I think you may be confusing ICL (intake centerline) with LSA (lobe separation angle). A 107*ICL is not out of the ordinary and the VVT will change it. For example, at 2* retard, the ICL will be 109*, matching the LSR277 cam. At 4* retard, the ICL would be 111*. That's the nice thing about VVT - you can change the cam's performance on the fly by modifying the timing of the valve events.
On another note, when you see something like "113+6", that means the LSA is 113 and the cam is advanced 6 degrees such that the ICL is 113 MINUS 6 = 107.
With VVT the VVT-2 cam can be 113+6, 113+5, 113+4, etc etc.
08-09-2012, 04:27 PM
#219
I'm not sure that's the case. I actually think more cam advance at part throttle would be better for mileage because the intake would close sooner, thus less cylinder fill to make the engine consume less air for a given engine speed. I think the retard is actually aimed at getting more internal EGR for emissions purposes. I'd love to hear more on this theory though. I could be confusing things!
