CI DENALI

I recently installed a Mast VVT "Escalade" or "Truck" cam (specs in sig.) and, after having to spend an extra week waiting to get a new phaser, (since the instructions weren't exactly clear on which bolt couldn't come out of the phaser and I pulled the wrong one, causing the spring to go out of round), I finished the install without incident. This weekend I was able to run it on Friday and Saturday nights, with various tuning tweaks, and I have to say that I feel like I have just wasted a bunch of time and money for nothing.
Firstly, let me disabuse any of you that think you can throw one of these VVT cams in and pick up a bunch of HP. You will have to get a proper tune for it, which will require spending quite a bit of time and money on a dyno, and from what I'm seeing, it might not be worth it, IMHO.
I say this because I made at least 12 passes on the weekend, and so far I have not bettered my previous ET, either N/A or on the N2O. We have changed shift points, ignition timing, cam phaser timing, VVE table and logged every run. I have a friend helping me with the tuning, who has a 2000 LS1 Vette running 6.7 ETs, with hundreds of passes on the stock bottom end, so I'm sure he knows what he's doing.
We encountered a number of issues, as one does in trial and error, but I have yet to see a better time than I ran before the cam swap.
Even though I am sure that the tune is not perfect, I would have thought that if this cam can really pick up at least 40 of the 70 or so HP without any real loss of low end torque, like Mast says it should do, and increase the RPM range by 1000RPM or so, I should have seen at least a tenth or so out of it, even with the worst of tunes.
To put things in perpective, on each run N/A, my AFR varied between 13.1 on the launch to low 12s at high RPM, and on most runs on the spray, it was in the low 11's, which is where the AFR's were before the cam swap.
Ignition timing was varied between 18 - 29 max, and the cam phaser was changed from the factory curve (10 degrees of retard at high RPM I think) to a curve which matches the one that GMHTP did for their Comp VVTcam install (8 degrees of retard at high rpm) and then back to the factory tune again, and the ignition tables were adjusted accordingly.
Not only did the ET increase (by an average of .15 secs or so) in most instances, but my MPH (which is the real indicator of HP gain) did not improve.
Don't get me wrong, I realize that this modification, as with most things of this nature, require good tuning to make power, and hot rooding is a labour of love, but the real **** kicker is that I can't even seem to find anyone that will sell me a tune that will work with the VVT cam. I asked Mast before I bought the cam if I could buy a tune from them (I would have bought the EFI Live Auto Cal with th etune in it) but they said they "didn't sell a tune for that cam" and it didn't really need much tuning, and that Horace could help me with the tune. But, so far, my e-mail to Horace has gone unanswered. Wheatley has indicated that he doesn't know much about tuning the phaser, since most of the time people remove it (which I think was very honest of him BTW), so I am really feeling lost right about now.
All in all, I am very disappointed, since this cam has a distinctive lope and seemingly no real power gains. It pulls good up top (shifts at 6700RPM), but the timer tells me a different tale.
I apologize about the length of this, but I didn't want anyone else to fall into the same trap as me.
If I could figure out how to make the 6L80E work without the EFI, I would probably rip the EFI off and install a carb, because I'm sure that I could do better than 11.4MPG with that anyhow!

Daryn

iTrader: (19)

you should have gotten a regular cam!

CI DENALI

No, I don't agree! I should've got YOUR cam!
Boy, am I kicking myself now!
I am going to try to do some more tuning on it though, and see what that brings...

denali-08

iTrader: (1)

you should of diseable the vvt, I did.

charcoal03silvy

iTrader: (1)

What's vvt? variable valve timing?

denali-08

iTrader: (1)

yes sir

ChevyThunder17

iTrader: (45)

That's a total bummer man. Could it be that with your timing is all over the place. Did you log any of your runs?

CI DENALI

Yes Sir. We varied the high and low octane tables on several of the runs, and we ran it with anywhere between 18 - 29 degrees of max timing. We kept stepping up the high and then low octane tables by like 2 -3 degrees. We logged all of the runs. One thing we noticed was that the timing goes pretty high on the launch, like 30+ degrees, but then immediately ramps down to a much lower number and then ramps back up in each gear to whatever the max was (18-29). That must be part of the VVT function.
I even watched the LTFT's on the launch to make sure they were slighly negative at launch (on most runs) and the AFR, from what I saw, was decent on most runs, but did go way rich on a couple of runs. I don't yet have the LM-2 tied into the EFI Live, so I only got to see part of the AFR curve during a run, so we don't have the AFR logged, unfortunately.
I'm still not sure if it's a VVT issue or just a shitty cam. Certainly the LS3 variant that GMHTP tested recently, with 2 more degrees of ignition timing and a little more lift on the intake, wasn't very impressive. Compared to the other 9 cams it made less power than everything else than other than the stock LS3 cam. The other thing I noticed from that article is that the LS3, even with the bigger cams, still makes good low end and mid-range torque, comparable to the VVT Comp cam that GMHTP did a while back. So, I'm really starting to wonder about the value of VVT in these engines. Wish I had read the recent article before a ordered this POS from Mast. I would definitely have stuck a Comp or Lunati grind in it and thrown the VVT away.
Oh, the other thing is that it now throws a random misfire (0300) and a MAP (0160) DTC every now and again, but I'm going to double check to see if I ghave a bad plug or wires and check the MAP sensor as well.

ChevyThunder17

iTrader: (45)

That sounds like a function of torque management. Was that turned off? It pulls timing during a shift to protect the transmission.


I think that the VVT is more for saving gas than it is for making power. That just sucks that you had to go through all of this and lose. Perhaps with some more tuning it'll work better for you.

CI DENALI

Yes we have modified the torque management, but have not eliminated it entirely. We still have TM by spark (timing) enabled and disabled TM by ETC and fuel. We have also shortened the shift times etc. This was the opposite, it seems to add a bunch of timing on the launch and then pull it out. It does pull quite a bit of timing on each shift, but it always did that before the cam was installed as well.


I'm thinking that the VVT should work, if I can get it tuned properly. And I've seen from the test that GMHTP did on the Comp grinds that they make power. I'm just wondering if it's the cam grind (lobe, LSA etc.) that is the problem. I have yet to see a dyno chart for this camshaft. (Mast has the one for the bigger L92HO VVT cam and they told me that this one only makes like 10-15hp less, but who knows?).