LNF Cam adjustment

[cobaltssoverbooster]

Intake Cam Peak Lift 5.9804 mm 6.2551 mm 5.9557 mm 6.1112 mm
Intake Valve Peak Lift 10.3 mm

Intake Valve Timing 126°

Intake Duration
@1mm lash 203.6°

Intake Valve area
@1mm lash 1171.3 mm2

Exhaust Cam Peak Lift 6.1061 mm

Exhaust Valve Peak Lift 10.3 mm

Exhaust Valve Timing -120°

Exhaust Duration
@1mm lash 194°

Exhaust Valve area
@1mm lash 1106 mm2

[cobaltssoverbooster]

someone please help me understand the lnf valve timing
intake is positive * and exhaust is -* like wtf
do i just disregard the fact that its a negative or positive value and use it as a vca value? what im trying to find is the vca value so i can finish my excell sheet its so close im makin plans for my happy dance....not really i dont dance just drink some beer

[stromboli86]

i wish i knew, but im in for the happy dance lol. Im just glad that while i was busy tricking my cams to change at idle i accidentally fixed my up and down idle issue on cold start!!

[cobaltssoverbooster]

baahaha win! ^

[cobaltssoverbooster]

based off of the factory cam specs i listed above this engine at full advance is showing no signs of any overlap at all its showing seperation by an average of 42* at all times.
so i honestly dont think my program is going to work until i find the real cam specs from full lock to lock on the phasers.

ive got alot of hours into this program so all i would have to do is change the values for what i find if thats the case. still trying different ways of computing. the formulas are getting very visually busy just to make them do things the way they should turn out.

[cobaltssoverbooster]

ok well here is the file i promised but results do dissapoint as the motor never has any overlap so the factory gm specs have to be some bullshit middle of adjustment specification and if i had that then i would have true perfect results.

[stromboli86]

So i went ahead and doodled on your excel sheet... sliced, diced and what not. Did some calculations using GMtech's crank degrees idea(so about 25degrees adjustment per cam), figured out what numbers i should see in several cells using pen and paper, then mangled the formulas and numbers used to achieve my calculated numbers! Might look closer to what you are expecting!

Stock cams barely hit overlap during cruise(when exhaust is most retarded and intake is most advanced) and are extremely far apart at idle when they are parked(exhaust "advanced" and intake "retarded")

What do you think? haha, its getting late

[gmtech16450yz]

Not sure what you guys are doing with those numbers, but I think you need to step back a minute and make sure you can see the forest through the trees. I would be extremely surprised if the LNF doesn't run any valve overlap. That just doesn't make sense.

One of the biggest reasons they started putting variable valve phasing in engines is to lower emissions. You can't lower combustion temps and NOx without overlap. You can't time the cams for better turbo spool without there being overlap. It doesn't make sense that with the 25* of individual cam timing authority moving the exhaust valve closing and the intake valve opening closer together that you're barely going to hit overlap after moving the cams 50 degrees?

So take a break from the Excel work and go out and pull your valve cover off. If there's an intake and exhaust valve open at the same time just by turning the engine over, then there HAS to be A LOT of overlap when the engine is running and those actuators are fully phased.

[gmtech16450yz]

Here's what GM says about it...

[stromboli86]

That chart at the bottom must refer to the intake camshaft... or both, just individually in some cases. Im confused more now lol. As far as the chart i was just fooling around with numbers on the LNF cam card. I dont know the actual valve opening and closing times and the numbers used were all at 1mm lash... it was late!

[cobaltssoverbooster]

That's what I said before....the gm spec is in the middle of phaser travel. The cam overlap but my fixed point isn't correct. When I tear it down later ill solve it then.

Not sure what you guys are doing with those numbers, but I think you need to step back a minute and make sure you can see the forest through the trees. I would be extremely surprised if the LNF doesn't run any valve overlap. That just doesn't make sense.

One of the biggest reasons they started putting variable valve phasing in engines is to lower emissions. You can't lower combustion temps and NOx without overlap. You can't time the cams for better turbo spool without there being overlap. It doesn't make sense that with the 25* of individual cam timing authority moving the exhaust valve closing and the intake valve opening closer together that you're barely going to hit overlap after moving the cams 50 degrees?

So take a break from the Excel work and go out and pull your valve cover off. If there's an intake and exhaust valve open at the same time just by turning the engine over, then there HAS to be A LOT of overlap when the engine is running and those actuators are fully phased.

[stromboli86]

On a side note, i have managed to control my idle cam timing all the way up to 172 degrees coolant temp so far. Have a few more tables i can play with but its definitely seeming like some of the tables are mislabeled

[Matt M]

That's what I said before....the gm spec is in the middle of phaser travel. The cam overlap but my fixed point isn't correct. When I tear it down later ill solve it then.

The GM released specs for the LNF cams are given with both actuators parked for maximum lobe separation. This is where the cams are timed at idle and also when the motor is not running. The intake cam centerline is 126 degrees(atdc). The exhaust cam centerline is 120 degrees(btdc).

Each degree in the chart is 1 crankshaft degree as John stated. I have verified this by watching the cam position sensor and crank position sensor on an oscilloscope.

Yes, the ecm still uses cat warmup cam tables when the cat warmup is disabled.

The reason the exhaust cam chart uses postive numbers and the intake cam uses negative numbers is because the actuators can only adjust the exhaust cam clockwise and the intake cam counter-clockwise.(relative to crank position, so it's actually the opposite of this)

The reason for the offset in the charts is because the 0s in the charts represent top dead center for the exhaust valve closing and the intake valve opening. Setting both charts at 0 gives you centerlines of 116 for the intake and 114 for the exhaust cams. At this point, you are on the edge of overlap. Going any further from the parked position now adds overlap. If you are going to calculate overlap, you want to use the same offsets for your starting point. It really doesn't take much to figure out the overlap. Simply take the exhaust cam reading plus the intake cam reading and then subtract 16. This gives you the overlap referenced at a very low valve lift, probably .006" if they used the cam industry standard. If you want to calculate overlap referenced to 1mm valve lift, add both cam positions together and subtract 43.2. If you want to calculate beyond .050", add both cam positions and subtract 49.

If you have any other questions, feel free to ask.

[cobaltssoverbooster]

Hot diggity Matt ur awesome! I'll change the file I made
So one value editor is one degree crank did I read that correct?
And lift main table values ex: midrange are overlap values yes?

[Matt M]

Hot diggity Matt ur awesome! I'll change the file I made
So one value editor is one degree crank did I read that correct?
And lift main table values ex: midrange are overlap values yes?

Yes, altering the table by 2 will move the cam 2 crank degrees or 1 cam degree.

Yes, if the tables show -10 for intake and +8 for exhaust, the result will be 18 degrees of overlap. Remember, that is seat to seat overlap, though. A few degrees of this overlap doesn't really affect anything.

[Gremlin85]

I hear my brain sizzling...

[yoecotec]

Wow guys ! Awesome Brainstorming

[Matt M]

I believe this is what the op is looking for- http://www.youtube.com/watch?v=RfT3Q...1&feature=plcp

This was done for entertainment purposes, only. We are working on a fix for the 7400 rpm cam phase limit, but the adjustable idle lope is fun to mess with.

[cobaltssoverbooster]

Yea workin on mine today as well I was away for awhile. Looks great Matt I plan on fixing the excell file to release on Saturday and then I'll also have a cam video as well with starter adjustments if people want it. If I see there is too much shift between cells I will not post graph because I wish to not put something out to cause damage to the valvetrain.

[ericemir]

I believe this is what the op is looking for- http://www.youtube.com/watch?v=RfT3Q...1&feature=plcp

This was done for entertainment purposes, only. We are working on a fix for the 7400 rpm cam phase limit, but the adjustable idle lope is fun to mess with.

Awesome!!! I too would like this just as a show off on what I can do with the cams lol This is awesome tech these cars have!!!

But cobaltssoverbooster is right... I would only want this if its safe. If it causes valvetrain damage then its no good. im excited for good news from this!