- Mover -

I'm monitored my valve timing via icarsoft as I was driving.
From some tech articles, I've found that the M273 has a range of 40 degrees adjustment on both the intake and exhaust valves.

Intake - +36 ATDC to -4 degrees BTDC
Exhaust - -20 BTDC to +20 degrees ATDC

I've noticed the following

• at idle the intake is at +36 ATDC and the exhaust is at -20 BTDC
• at full throttle I observed the intake at -4 degrees BTDC and I couldn't make out the exhaust (I think it was +16 ATDC)

Could anyone explain the theory behind how Mercedes adjusts the cams in different situations ? The measurements they've listed don't make much sense.

Back in the day, before VVT, the intake closing was one of the most relevant items in the production of power. ie Late closing = high rpm power, early closing = low rpm power,

chassis

You have probably seen this: https://en.wikipedia.org/wiki/Valve_...e_valve_timing

Power/torque (bmep), fuel economy, driveabilty (smoothness) and emissions are all variable to be solved for as it relates to valve timing, fuel delivery and spark timing.

- Mover -

Yes, I understand the theory from many years ago. For instance, Mercedes has an intake valve opening at 36 degrees After Top Dead Center ?
Opening after top dead center doesn't make sense even factoring in it being measured at 1 or 2 mm valve/lobe lift.

Am I missing something ?

chassis

Can you provide a link to the article you found with the valve parameters?

- Mover -

https://performancetechnician.com/pd...VVT-Issues.pdf

chassis

Thanks @- Mover - . Are you referring to the verbiage on page 14, middle of the left column? The article is not well written. What is meant by "advance" and "retard" in that paragraph? Where does the information come from? Is there a Daimler WIS, Xentry or technical specification document that confirms?

edit:

The following is from WIS BE05.20-P-1001-02N for engine 276.9 (I realize this is not your engine, but rather my engine. In principle the values should be similar).

Check values (static bench measurement, I assume):
Intake valve open 4 deg BTDC
Intake valve close 36 deg ATDC
Exhaust valve open 25 BTDC
Exhaust valve close 15 ATDC

I think you are missing something. The text above is verbatim from WIS.

- Mover -

I agree, the article isn't very clear.

The measurements you've listed for your engine; since the 276.9 has variable valve timing as well, how much can the intake valve opening (4 deg BTDC) vary from the static value you have listed ?

An intake valve closing 36 deg ATDC doesn't sound right either although you are quoting from WIS (which I don't have). The duration can't be that short. Intake valves generally close after bottom dead center (ABDC) when the intake stroke has completed and the piston is starting its upward movement on the compression stroke. The reason being is that the column of air entering the intake valve has inertia and continues to fill the cylinder even as the piston begins its compression stroke.

Something isn't adding up. Below are some examples of cam timing.

http://www.schrick.com/index.php?article_id=41&clang=1



Here are some cam specs for another Mercedes engine.

chassis

@- Mover - Thanls. Do you mind qualifying yourself a bit? Where are you headed with the questions? Pardon the ask. On this site we get people from pre-teens in third world countries to seasoned former Mercedes service technicians. Some people are looking to write a 6th grade school essay, and some people are looking to get 1000hp out of their engines. Where are you on this spectrum?

I provided you Mercedes information from the authoritative Mercedes service literature. What are your credentials on this topic?

- Mover -

Thanks for providing the information. I don't think its useful to this topic going off on a tangent with regards to credentials (I have them and they are many many years of hands on experience).

As another reference to highlight specs of a camshaft, page 2 of the Schrick Technical Information pdf listed in the link below lists a typical cam card as well as several of their cams.

https://www.turnermotorsport.com/p-1...63-m6-s85-v10/

chassis

@- Mover - The figures from WIS result in 400 degrees of total intake valve open, and the figure on page 2 .pdf in the link you posted shows around 300 degrees (between 0.5mm lift points), eyeballed from the chart. To me these are roughly in the same ballpark. Page 10 in the appendix of the pdf has similar values as the WIS values for intake valve on the M276.

Is any of this amiss in your view?

- Mover -

Hahahaha.... I'm not going to bother with that one.
Yes, something is missing

Interesting that Kleemann keeps their specs to themselves. Happy hunting.

" It comes from ........"