Can timing

[PurpleRam]

Im not sure we are both on the same page. I know the difference between the spark timing tables and cam vvt tables. What im saying, is that when you go and adjust the vvt tables, like for my 5.7, 125 is max advance, and then retard it 1 degree to 124, it moved the cam 1 degree, as shown in the log for cam position. If the tables were showing crank angle, it would be showing 123 degrees, since the cam moves 2:1 from the crank.

Yes, you are correct, what we use in the tune(HPTuners) is CAM degrees , attached is the base setting I use for SRT392 cam in 4x2 Rams

[LilSick]

i talked to Nick at Clay Smith. Then i talked to Faith at Web. Got both of em confused : )

Was trying to get ahold of Rod at isky but he was busy so i drew out a flying W

for the centerline to be a number that is less than 180 degrees (cuz i know its not on the compression stroke) it has to be in cam degrees

icl.png

corrected myself Brian - sorry for the bum steer

[Hemituna]

Yes, you are correct, what we use in the tune(HPTuners) is CAM degrees , attached is the base setting I use for SRT392 cam in 4x2 Rams

Actually, the numbers used/shown in PCM/HPtuners are cam lobe C/L in crank degrees....just like you read from a crank degree wheel.

It is the mid-point of the lobe expressed in crank degrees from TDC. This only tells you lobe position (adv or ret) not the valve open and close (that varys with C/L and duration).

The numbers can seem confusing as intake advance makes intake C/L numbers smaller, but exhaust advance makes exhaust C/L numbers bigger,
Intake retard makes intake C/L numbers bigger but exhaust retard makes exhaust C/L numbers smaller......WTH???

So, say you have a 6.4L Hemi. Stock cam LSA is 120.5 with 14degs advance ground-in.

Lets put 120.5 in both intake and exhaust tables (I know the exhaust table is the controller but for this example lets do both)

The phaser will retard 14degs (the ground-in advance) from the lock-pin/full advance start position and the cam is now "straight up"..that is - no advance or retard so both lobes on same 120.5 C/L.

Now lets advance the cam 4 degrees. Intake will be at 116.5 and exhaust 124.5 C/L.

Advance another 4 degrees. Intake will now be at 112.5 and exhaust 128.5.

Fully advance the phaser and you will see 107ish and 134ish which is the 120.5 +-14deg adv +- variation in cam sprocket and chain length.

These are the numbers you are seeing in the cam tables and on scanner.

Sounds crazy but is simple maths and once you get your head around it kinda makes sense. (helps to have done multi cam engines)

[Hemituna]

In the 6.4L stock cam example above.
ICL is 120.5 crank degrees ATDC (on the intake stroke)
ECL is 120.5 crank degrees BTDC (on the exhaust stroke).
This is why the C/L numbers go opposite ways when you adv/ret the cam.

[LilSick]

the confusing part is that the center line is in crank degrees from tdc...

but not tdc firing

[Captain052]

Hi.I have. 2012 6.4 charger that has LT,90mm throttle body, ported intake,CAI. I just put a comp cam stage 1 HRT. With phase limiter. Car tuned fine runs and starts fine with good 12.7 WOT fueling and minimal knock. Now the issue is regarding the VVT tables. The car ranges from 134 degrees to 117 degrees exhaust cam degrees. Now the issue is i don’t understand this table. Stock exhaust wot tables have high degrees below 4000 and lower degrees above 4000 rpm. Now is the high numbers advance or retard? Because i tried lowering the numbers in the high rpm to gain more hp but i feel the car power drop. Doesnt make sense. Normally retarding the cam should gain hp up top. I hope you can help me out with this. Appreciate it a lot!

[Spray-Cam Hell-Ram]

Yes, retarding the Intake cam should in most cases gain HP up top. Which means your exhaust cam would need to be advancing. Don't forget that it's the exhaust cam that we make adjustments to... and the theory that "retarding a cam should gain HP up top" is referring to retarding the intake cam I believe. This seems to be a common oversight being that most platforms work from the intake cam side.

[LilSick]

the easiest way to explain cam timing (can timing : ) is with what i have heard referred to as a flying W

with each leg of the W being one stroke (180 degrees crank rotation)

the only problem with that is that it usually starts with the intake stroke as most people think - intake, compression, power, exhaust

best way if don't understand is to START WITH THE EXHAUST STROKE

think of the four cycles as EXHAUST, INTAKE, COMP, POWER

[LilSick]

or look at the cam from the front:

[LilSick]

in the next pic ^^^ you can see that because of the direction that the motor rotates the exhaust is first, followed by intake

looking at it like that always helped me make more sense when considering overlap or centers

on a gen 3 both lobes are on the same cam

adv one you adv the other

as you adv it the ICL is decreasing and the ECL is increasing

hopefully those 2 pics ^^^ will help you to understand why

remember - the exhaust lobe is before (or in front of) the intake lobe

[chuckk]

I have a cam here with ICL at 106 ATDC and ECL at 116 BTDC. Assuming to retard the cam as RPM increases, wouldn't the numbers go from 138 to more retarded values of 138+ ? Looking at the stock ecu file shows maximum value of 138.

That means the hptuners numbers uses numbers referencing BDC. So 138 ABDC is fully advanced, then 93 ABDC degrees would be turning the cam counter clockwise (retarding it).

Why are they referencing BDC ?

[LilSick]

that is not bottom dead center

btdc = before top dead center

[chuckk]

that is not bottom dead center

btdc = before top dead center

I know that. The cam sheet I have shows the ECL being 116 btdc. If you want to retard the camshaft, you need to move it counter clockwise. Going counter clockwise would only bring the ECL 116+ btdc. (Or use the factory 138 number and increase it by the amount you want) But you can't go above 138 as it is the maximum number.

The hptuner numbers tells us that 138 is fully advanced and 93 being maximum retard. If that is the case. They are in relation to BDC. Why is that ? Or I got something else wrong.

Sorry, I confused the actual movement you do with the cam with the centerlines position on a 360 degree circle.

[LilSick]

the centerlines position on a 360 degree circle.

did you see that W i drew above?

don't think of a circle...

think W = 720 degree

if you do not degree the cam and know where you are, and then compare that to a log, they are just numbers anyways

[LilSick]

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