Maybe it bumps to 11 deg when you factor in the timing chain slack + LS2 damper

 

let's not start that again.. LOL

 

Measured mine. Correct chamber .257. Wrong chamber .220. Because its a five vane setup, its hard to measure the dia. I approximated 3.335 where he had 3.294. If I use his number I get 17.89 vs 15.31 crank degrees (8.943 vs 7.657 cam deg). That's over 2 crank degrees lost for you Mike and another confirmation we are shy a few deg from Comp's advertising.

 

Clint,
Stop posting here and finish your engine build. I want to hear your comments on your TSP VVT2 cam. LOL

 

Thanks for the clarification Clint. I opened up the tune today and verified
The duty cycle approaches 100% trying to retard the cam up to 20deg, but
My measured rotation was pegged at 7deg. Then the PCM codes REP and you get to pull to the side of the road..

Oh well, I think we learned a lot about the VVT system and tune here and
My questions are answered.. Thanks to everyone..

 

Are you trying to measure end to end? The comp rods are sized to gage length which will be shprter than the overall length. They use gage length because overall length is affected by hole tolerance.

Would love to ride in that 1500!

 

Wish it was mine. It is really fun to pass someone drop down to third and pull in at over a hundred. Going to really hurt someone in a stock mustangs feelings someday.

 

Good to know im in the right ballpark with my values but theres no spray here lol. Just a fun street car that cruises like a baby at 1500RPM. Truth be told this cam i have in here is so mild mannered Id love to stuff a more aggressive grind designed for 7500 RPM peak and get a little crazy but I have other projects that I need to focus on. This car gets too much attention anyways


The one shocking part of this engine is its RPM range wow it wails! I've buzzed 7500 many times and its as smooth as butter up there. My limiter got messed up somehow with some of the tables I hacked through to get everything working properly but I did initially have it set to 7K.

Anyways back to the tune here have any of you guys played with VVT spark at all?

 

We didn't use n2o on the dyno. Old man Patterson made it clear about that. lol The problem is that those engines have much bigger cams so I don't know how well they compare. 286/312 @ .050 117 lc .980 lift. I ran that at 2 deg crank retard. If GM is taking 7.5 cam or 15 crank out on a stock cam that puts it at apx 8 degrees crank retarded at 6000 rpm. If I trust my test methods my baby Silverado cam didn't like that much retard. I just guessed at 3 deg crank retard for my final setting at 6000.

I Zeroed out all the 4000 and up spark adders because I wanted to see my timing in just one table. I did that to the PE spark adder table as well like most other tunes I have seen do. I did leave the part throttle spark adder table still in there but I did reduce the big numbers by about 40% because we are not retarding the cam near as much. Nothing scientific, just a guess. I'm not getting any knock, part throttle or WOT is all I know.

I really want to get ahold of my Moms 07 Tahoe. It has VVT I'm pretty sure, I know it has DOD, and play with the Cam positions. Thought about setting the cruise at 70 and resetting the avg fuel mileage indicator on flat ground for several miles til it stabilizes. Probably do it two directions to get an average.
Do this once with the stock 26 degree or whatever it is setting.
Then do the same thing with the cam at full advance with the VCM controls.
Then maybe do it again at 13 deg retarded to simulate where my cam with 10 degrees later closing intake valve (5 cam) + 8 from my blocked actuator.
Then maybe once again at 21 (5 for my cam + 16 for the actuator opened up to what I consider the most I could run and still have .100 PTV on my exhaust).

After this I can decide if it would be worth the trouble to take the actuator back out of the 1500 I just did and machine a little off the blocker.

Stan

 

From the few aftermarket VVT tunes I've seen so far, it appears people are making cam phasing depend on engine speed only. I think if you want to see a MPG benefit, you're going to need a "hump" in your VVT table to put some dependency on load at lower and mid RPM ranges. That will give low/mid-RPM, part throttle cam retard which has the late intake valve closure effect. I'm not sure how much mileage benefit there will be given the limited amount of timing we have to play with. I am also under the impression that VVT in OEM GM application is not helping so much with fuel efficiency but more for lowering combustion temperatures to improve emissions and adding improved matching for cam timing vs. RPM.

 

"I think if you want to see a MPG benefit, you're going to need a "hump" in your VVT table to put some dependency on load at lower and mid RPM ranges."

Of coarse you are. I left the part throttle area similar to stock but had to limit it way down to only 8.5 degrees vs 26 in certain areas. I'd show you but then I'd have to kill you. lol Here you go. Stock vs modified. I ended up another degree more at 6000 in my final tune.

 

I think it's interesting how little retard you ended up with. If I read your table correctly, you're at almost 4* cam (8* crank) retard at 6,000rpm, which puts your 114+7 (107ICL) cam at 114-1 (115ICL).

The TSP cam I have is 227/235 .614/.621 113+6 (107ICL). The TSP tune I've seen for it had 7* cam (14* crank) retard at 6,000rpm which puts it at 113-7 (121ICL). That's quite a bit more retarded (not pun intended).

I wonder if this has to do with boost, your particular cam, or if you might actually benefit from more retard.

 

I tried both of these tunes with the virtual dyno program I use and the less retarded tune made 5 to 10 more hp. Don't remember exactly. If you read my last post I said my final tune I ended up adding apx another degree at 6000 or 5 cam degrees total. That puts me at 117 ICL. Didn't waste my time testing this till I go to a chassis dyno but I feel its close. You have to have pretty repeatable data to test this kind of thing.

btw you would be at 107+14 = 121 ICL with your cam and tune at 6000 rpm
I was at 107 + 8 = 115 not 113 with the attached tune at 6000 rpm.

 

Does your dyno program take ignition timing into account? When the cam is more retarded, you can add more ignition timing (advance) since the DCR is lower. I wonder if advancing the ignition timing develops more power to offset the loss your dyno program is predicting?

 

http://www.hptuners.com/forum/showth...t=virtual+dyno

Here is Brad Barnhills program I use along with data taken from HP tuners. Lock the converter and the tranny in 3rd gear with the scanner, find a nice level road (private of coarse lol) on a kansas day with no wind. slow down to apx 30 mph (2000 rpm) and let her rip to 6500. Convert the data to excell and load it into the program using the correct vehicle weight, tire size, gear ratio, trans ratio, frontal area, and drag coeficient.

It works pretty well but you have to use the same road in the same wind conditions to get repeatable results. Of coarse things like water temp and IAT will change your results too.

I need to donate something to him.

 

Half my build is from this line of thinking ^ Someone has to figure it out so off we trudge into never never land and hopefully bring back some worthwhile knowledge.

Kind of why I was asking about VVT spark earlier.

As for utilizing the low RPM hump yeah Im sure that has some benefit for mileage by easing the pumping losses but is not really a concern for me as of yet. This will be the last bite of cake on my build in the meantime Im trying to get all systems go and get the most out of them but there are some inherent weirdnesses with the e38 related to making it a stand alone system that has caused me a lot of grief. As my tune sits now I get a little bit of KR but only in 4th gear and for whatever reason 4th gear also pulls the hardest. Im concerned that this has to do with VSS related tables as I have a t56 and the VSS coming straight off the trans causes "issues" and 158 speedo pegging etc. Basically a can of worms with little answers but as time alllows I will be digging into these things further and hopefully gain some more ground.

Looking back some of the things I thought were happening? were in fact not, so some of the posts I made, make no sense as a result LOL. But thats to be expected when messing with new tech. As the first quote says I took my best guess and worked at it then often was sidetracked by something else that cropped up which led me to this point which is running and driving well but more on the table.

A dyno sure is a handy tool for sorting out these things though. Wish i had one here

 

Since my cam is the basically the same,
I was planning on dyno'ing soon. I ran across a LS3 PatG spec'd cam (http://forums.corvetteforum.com/c6-t...whp-445tq.html )

which was

So If i lock the tune at 4 in every cell of all 3 baro tables, I
should basically have a 228/236 .614/.619 113+2 cam to
ballpark test against this non-VVT cam. Then by dropping back in the VVT variable tables, get an idea of how much, if any, the VVT system benefits..

Thoughts? It would be running a MAF tune, so there's shouldn't be much variability between the two runs.

 

I missed this earlier. I tend to fly through most threads these days, Anyways no the cars still in pieces but I may have some time soon to get it sorted so it "might" see some asphalt again before snow flies.

By the looks of it the DC is fine assuming the scaling is similar to injectors where 100% is actual ratings and not some arbitrary value like TPS etc. I dont see what else logging the intake cam dc could provide?

So long as the cam is retarding as commanded I cant see worrying about the DC values of the phaser unless they were to go past 100%

I wonder if the DC is logging values because the phaser is trying command to a place where the limiter is blocking it? Just a thought that may be why its giving you some values when the cam isn't moving?

 

This is pretty much what i was thinking to do. Hit the dyno and start with a baseline of VVT zero'd out completely, then a pull with stock phase profile loaded, then my own profile, and compare results and make changes accordingly. This should make it pretty easy to see where the cam timing is making gains or losses and work from there.

 

I think there's a lot more to it than that unfortunately. You could tune the engine for a fixed cam position using conventional methods, but I think once you start changing the cam phasing you are dealing with multivariable optimization. For example you might get the same torque at a given RPM for two different combinations of cam + ignition + fuel, perhaps with different volumetric efficiency, combustion temps, BSFC, transient response, detonation resistance etc etc. It could get tricky trying to find the balance which I think is why some tuners shy away. Different cam timing will need different fuel & spark, so it will take some time and potentially a lot of iterations to get it right.

I also think there's flaw in comparing the patG cam to your cam. The difference in cam timing is not negligible (2 deg of duration and different lift). Also do you know if it uses the same LSL lobes as our VVT-2? I think a better starting point for comparison would be the nonVVT version of the cam I pointed out in another thread. If you personally want to prove out the merits of VVT, you could command fixed phasing over the whole table and tune it for that, but data is available already for a similar setup and I don't think I would waste my tuning time on arguing VVT merits. I just don't think it's worth trying to settle a bench racing argument when you could be driving toward the right tune for your VVT enabled setup. I tend to think the TSP L99 tune would be a better starting point given whatever hours they put into developing both the cam and tune, but from there it's going to take dyno and driving time to sort it out.