Cam Timing Tables

[Bobby]

Hey guys just looking for some information regarding the values in some cam timing tables if anyone can help out.

For the main cam angle table do these values refer to the intake valve opening angle, eg would -10 mean the intake valve will be opening at 10 degrees before top dead centre, or does it just mean that the intake cam is advanced 10 degrees from its "installed position" and has no reference to the intake valve opening timing? 

Secondly the exhaust cam overlap table, does this reference when the exhaust valve will begin to open in regards to the intake valve closing, eg 30 would mean that there would be 30 degrees of overlap meaning the the exhaust valve would be opening 30 degress before the intake valve would close?

This is the way I have interpret these table, just looking to clarify if this is right or whether i am way off. If I am interpreting these right then you would have to make the assumption that there is one of two things happening. Either a, there is somewhere in the PCM where you could tell it the came specs, or b which I think is more than likely the case that the cams are installed with 0 overlap and overlap only occurs when asked for from the PCM? Which would explain why tuning cams would be a pain in the ass if the specifications are unknown.

Thoughts?

[Roland@pcmtec]

The PCM assumes cams are installed with no overlap. Completely agree that it would be much simpler if cam grinders made all barra cams with 0 overlap and let the pcm do its job. Would halve the tuning time required. 

Overlap table is exactly that. It takes the intake cam position then adds the overlap angle to it to make it open sooner. 

Intake cam angle timing is simply +- top dead centre, so positive is retard, negative is advance. 

[Bobby]

So it seems like the way I’m thinking about it is right.

However just confirming that cam timing table values refers directly to the intake valve opening event, similarly to the new mustangs tables that actually refer to this as intake valve opening (IVO)? That’s assuming it has factory cams, larger duration cams installed with the same cam timing would have the intake valve opening earlier, so to get the intake valve opening at the same position as factory cam you would have to retard the cams.

[Roland@pcmtec]

I'm not really sure what you mean to be honest, what is the alternative?

[Bobby]

Based off that response I assume there isn't an alternative and it is intake valve opening.

[Sam]

Sounds like yous both have confused each other but are talking about the same thing 😄

[Bobby]

Whilst we are on the topic, do you know who actually grinds cams so there is 0 overlap?

[Roland@pcmtec]

14 minutes ago, Bobby said:

Whilst we are on the topic, do you know who actually grinds cams so there is 0 overlap?

No cam grinder that I know of. Some workshops do their own cams and they might, I think Precision/Hoontune might?

[Puffwagon]

Kelford do custom cams for the barra. Crow will do custom cams. Here's another option.

I reckon there would be more but there's a couple at least who say they'll do it. You'd just need to work out the specs yourself or talk to them to work out what you need. It wouldn't be too hard to sort out.

Edited May 8, 2020 by Puffwagon

[Roland@pcmtec]

Yeah custom would be the way to go. Personally if I was doing R&D I would just add lift and a tiny bit of duration with no overlap.