2012 Blown 6.2L 1500 w VVT cam questions

[stan]

I am putting a 1900 Magnuson blower on a customers 2012 1500 Chevy pickup with a 6.2L engine that has VVT but no AFM.
We are also putting a Comp Cams small VVT cam with 214/228 duration and .559/.571 lift on 116 LSA. Also putting in there phase limiter kit and some better springs.
Keeping stock exhaust and converter so I don’t want to get carried away with the cam.

Has anyone ever messed with the VVT tables on one of these or will they work ok stock?? If I understand correct the retard at part throttle is simply for fuel mileage and figured it was probably close???? Maybe you should limit the tune to match the 22 degrees travel of the phase limiter???

However they are retarding the cam 3 degrees at 4000, 6 degrees at 5200 and 8 degrees above 6000 in the factory tune at WOT. Is that in crank degrees or camshaft degrees??? If its Cam degrees that seems like a lot. My guy at comp didn’t have any suggestions at all. Would you mess with this or leave it alone??? Probably won’t put it on a chassis dyno but might if I have to.

[brandonleg]

Some good info here:

http://www.hptuners.com/forum/showth...t=total+timing

For a 2011 6.2, 2012 should be the same based on the actuator p/n:

Below is from Alldata.
(see attached pic)

A CMP actuator dynamically changes valve timing events relative to piston timing by controlling camshaft position. This is sometimes referred to as variable valve timing or camshaft phasing. Variable valve timing or camshaft phasing does not change duration or lift.

•By advancing camshaft timing, an improvement in low end torque can be achieved.
•By retarding camshaft timing slightly, an improvement in high end power can be achieved.
•By retarding camshaft timing significantly, an improvement in light load fuel economy can be achieved.
There are 5 cavities divided by vanes within the CMP actuator.



•When oil is directed to the advance cavities (1), the camshaft timing is advanced.
•When oil is directed to the retard cavities (2), the camshaft timing is retarded.
•When oil is directed to both cavities, the camshaft is held stationary.



The CMP actuator has a 52 degree range of authority. With the engine not running and no engine oil pressure to the CMP actuator, the high tension spring positions camshaft timing at the 7 degree advanced park position. During normal engine operation, and based on performance requirements, the ECM may adjust camshaft timing, as required, within a range from 7 degrees advanced to 45 degrees retard.

[stan]

So based on this the Cam is advanced 7 camshaft degrees or 14 crank degrees until 4000 rpm. Then the table in my tune I posted retards the cam 3 degrees for a total of 4 cam or 8 crank degrees advance. By 6000 we are at 8 on the table so the total retard is now 1 cam or 2 crank degrees.

Is that correct????

Has anyone ever fooled with these numbers for a small aftermarket cam like I am going to use??? Do you think the factory retard settings would be close??? It will be interesting to see what the ICL is on the factory cam and my aftermarket cam in the parked position on this motor. 16 Crank degrees still seems like a lot to move a cam around for max performance at WOT. I understand the big retard going on at light throttle for fuel mileage.

[Area47]

you can't run the stock vvt tables with an aftermarket vvt cam. it will throw a p011 in a heartbeat.

you're limited to 20 degree's. you have to set the vvt tables a lot lower than that to keep the code from popping up. im running 8.2 degree's at part throttle. {log indicated} to keep the ses light away.

[stan]

With a 22 degree phase limiter I figured I could run close to that at the part throttle areas. I think the stock tune has 26 degrees in some places. I was going to reduce those cells to 20 and smooth the rest out. You don't think I can run that much???

[brandonleg]

Why keep 'em at all? Are you worried about fuel economy?

Zero that table out, actually, zero all three of 'em out - low mid and high baro, I forget the exact name, and zero the corresponding areas of the VCP spark, go for a drive paying attention to part throttle response, and see if you still want to keep them then.

[Area47]

the part throttle vvt tables i came up with work very well with the tsp vvt cam i have. response is good and gas mileage is good as well. i personally wouldn't advise zeroing them out for the sake of not learning how to make it work in your favor.

your cam is milder than the one i run, so my tables may not work for you. the max degree's mine will pull is 17.8 {indicated on the tables} more or less the limit before it will trigger the p011 code.

[stan]

This is a daily driver for my friends truck. I want it to idle like stock or close to it. He really doesn't want to give up any advantage the VVT can offer in fuel mileage. If it is only being done for emissions then that is something else but I understood the big retard at part throttle was to give the engine a shorter compression stroke which aids in fuel mileage. Similar to the ISKY Mileamore cam and piston package from back in the 80s with delayed intake closing and special 15 to 1 CR cast pistons. The idea back then did help fuel mileage but at a price of very poor low rpm torque. Now we can have our cake and eat it too so to speak.

I am suprised more people on here have not worked with this. Seems everyone just wants to eliminate it. I will try zeroing out the part throttle areas just to see what it drives like. If it makes a really big difference then I will let my buddy decide if he wants to trade throttle response for fuel mileage.

No one has answered me yet on the WOT aspect of this tune. Do you think the 8 degree retard in the stock tune is close to what I would want for this cam??? Someone on LS1 tech did a simulation program of 10 degree retard vs straight up vs 10 degrees advanced. The results showed to support doing close to this for WOT power.

Does the 8 degrees in the table really represent 16 crankshaft degrees of cam movement???

[brandonleg]

Oooops, I forgot you guys are running a cam. Belay my last...

[LSxpwrdZ]

I tuned a Hennessey 2010 Camaro with a blower not long ago that was auto and had VVT. It picked up tremendously adjusting various parts of the timing curve. However from what my memory serves it wasn't far off from stock. The camshaft was also unknown in this car. It sounded non-stock but with the combination of crazy loud exhaust and the blower there is literally no telling what camshaft it had in it. Best bet is to get plenty of dyno time and work with those tables exclusively for a couple hours. That is what I did on this particular customers car and it paid off.

[stan]

Thanks James. Sounds I might just have to take this to a dyno to get the most out of this deal. Probably wear out the truck if I wanted to.

Do you know do the values in the intake cam position table shown above in post #5 represent camshaft or crankshaft degrees retard??

[LSxpwrdZ]

It was my understanding that they are crankshaft degrees. However the numbers are reversed and backwards meaning that entering 0's in the table doesn't put the cam dot to dot so to speak. Here is a spreadsheet that I built to help with VVT. You paste the table into the spreadsheet and it basically back calculates it to crank degrees retard or advance from dot to dot. - numbers are retard and + numbers are advance. Looking at the data in this matter makes much more sense to me how and why the camshaft works like it does.

I personally love VVT and would never disable it if I had the luxury of using it. So much more flexibility and broadening of powerband using it!

Source for info:http://www.hptuners.com/Forum/showthread.php?t=17883

[stan]

Thanks James, I think I get it now. Everything is in Crank degrees. The numbers in the charts in HP tuners are in crank degrees of retard from parked. The cam is advanced in the park position 17 degrees (or 7 degrees in the 2012 6.2 I'm working on). What was really confusing to me was the drawings I have seen showing the 62 (or 52 or 46) degrees of travel that the cam phaser has and the fact that it was scaled out in CAM degrees on the drawings. When I looked at the inside of a phaser I realized there wasn't room with 5 oil chambers to have that much travel. Best I could measure from the pictures if found, it had to really be 31 cam degrees or 62 crankshaft degrees.

[cam]

Best bet is to get plenty of dyno time and work with those tables exclusively for a couple hours.

This^

Mines still sitting at "best guess" stage at the moment. I zero'd out the stock tables and began using phase movement around 5000 RPM and iirc its only at about 4 degrees total retard now but ive had it as much as 10 ( no codes either? Hmmm ). Anyways it seems to be working very well but I had other trans and driver issues with the car before I made it to the dyno to do the above. When I do i'll post up what worked, and didnt work.

Wish i had more free time to play with this stuff but so it goes.