Why would one retard ignition?

[LEAKYSEALS951]

WELCOME!

To ignition timing "days of our lives..."

(or perhaps I should say intake/exhaust cam timing)

I have a question. Let's say you are an engineer. At your disposal is a variable timing system for both intake and exhaust camshafts for your engine for optimal performance.

With that in mind, why would you want to retard either intake or exhaust cam timing in your setup?

And with THAT in mind, I get to the point of this and say this- I am rebuilding my xc70 which has (imagine this...) variable cam timing on both intake and exhaust cams.

To sweeten the pot, know this, I marked everything, and sent the head off to be rebuilt, with one caveat... The head rebuilder pulled the VVT cam gears off the cams themselves. Basically- unlike every car I have owned, he left me with a f#$#$ up. there is NO marking to say "place cam gear here"


In short, the head rebuilder screwed every reference mark I had, and I think he did it out of spite!

Not only that, volvo VIDA has discrepancies in their own tutorials on how to set these suckers.

With that in mind, I wondaaa...... (like a fish called wanda)... why would one want retard capability in a setup?


In the next couple of weeks, I will have the "opportunity" to get to setting this puppy up, and I am stressed bigtime! I seek knowledge in this area so I can be like NEO from the matrix and see the numbers rattling off the walls with a greater understanding of they "why" to make good choices in my infinitely screwupable setup.

Only 20 valves at risk.... no pressure!

[fastfredracing]

You need the cam locking tools

[LEAKYSEALS951]

edit- or better yet- if you, a friend or, loved one, have knowledge of how the heck to pull this off, please know I will compensate greatly in beer, wine, whatever...

TIA

Ron

[LEAKYSEALS951]

Originally Posted by fastfredracing

You need the cam locking tools

They are coming in the mail, should be here shortly. I am trying to weed outall the internet videos of "do it like this" versus the volvo vida guides of "do it like that" which are contradictory at best.

All the videos stress the importance of the camlocking tools. They set the cams right. The challenge is setting the cam gears on the cams, knowing the vvt will change even that relationship.

This, also overlaid by varying degrees of complexity. 2000's had only the exhaust as variable, by 2005 exhaust and intake. Also, earlier models were spring actuated, whereas later models are purely oil pressure driven on advance/timing.


Basically, the diy videos are telling me to advance the cvvt's to a forward position and set it, where volvo is retarding it. Ordinarily, I would heed to volvo vida, if not for the fact ALL internet diy'ers are telling volvo to go to hell. Based on what I have seen on vida guides, I can see why the internet diy world is saying it.

In my 2 fleapower head, I can understand the system IF there is no need for retarding things from a basepoint. Also- This premise makes more sense on later vvt systems which are not spring loaded under the premise of "if there is no oil pressure on startup- have the cams set at a nominal position to allow mechanical pressure to spin things in a non interference sense until oil pressure can build to a point to advance as necessary." I cannot see a retarded timing being given too much heft in a situation where without oil pressure, retard, could mean really retarded to the point of interference....

(This is why I drink?)

[wdfifteen]

I got nothin for ya. I do remember trying to adjust the linkage on my buddy’s 348 with three deuces. If the second set of carbs opened too soon the engine would hit a flat spot in acceration due to lack of vacuum. It’s a pretty delicate balance. Also, you don’t want to feed too much alfalfa to yer horse. But we didn’t have computers then and emissions control meant not farting in church.

[LEAKYSEALS951]

I'm just going to throw this thread in for fun, HOWEVER, I want to stay on the simple topic of.... Why would one want to retard cam intake/exhaust for any reason whatsoever?

dat is d Qstion!


and here's why my head hurts-
https://forums.swedespeed.com/archive/index.php/t-225475.html

In other news- I set a new record- EIGHT HOURS TO INSTALL 11 bolts!!!!!!!!!

New (well 2005) cars arent meant to be worked on!

[LakeCleElum]

Title talks of retarding ignition. Post talks of timing Cams. Which is it?

You want top end power or more torque?

Back in the early '80's, when roadracing motorcycles, I played with cam timing a bit....I slotted the bolt holes in the sprockets, so the cams could be rotated a few degrees both ways....

Best to do your homework and find the specs for you application....

[LEAKYSEALS951]

I'm Clark Griswold. I am on a quest for fun at wallywold. Aunt Edna is ON the roof. I just don;t want valves getting bent, or even error codes in an "ideal world"

[beepbeep]

This is VAG knowledge but is should apply to Volvo as well: Generally, intake cams are continuously phased to broaden the torque curve. Exhaust phasing is mostly on-off affair for emission reasons, affective around idle and engine braking.

That being said, you could mount them the way you believe they should be then turn motor the engine manually w/o plugs to check no valve contact (with both phasers moved between extremes. If engine goes around, fire it up. If phasers are "tooth off" ECU should log code "cam advance not achieved" etc.

If *ignition* timing is delayed, you will notice it by very smoothly running engine and cat glowing cherry red.

[silverc4s]

I seem to remember that the turbo Corvairs had a “pressure retard”for the spark timing. The opposite of vacuum advance....
Not sure if that’s any help. Maybe the Volvo has a turbo??

[LEAKYSEALS951]

The volvo does have a turbo. I found another Volvo Vida manual today which corresponds more which what the internet DIYers are saying. I feel a "little" more comfortable now, but not totally comfortable. A LOT of new "while you were in there" stuff is going into this engine and I don't want to screw it up.

I miss my simple little marks. Align everything at TDC, and be done with it!

What I was trying to get at last night was the idea that I wish I could know if the setup for this VVT stuff sets up a retarded cam timing as the start point, from which it can advance things with hydraulic pressure to typical TDC relationship, and then various advance points, or if it just started at a TDC scenario and would put in advance from there on out.

I was trying to get my thick head around what the benefits of cam retard would be (if any). and yes, sorry if I mixed the terms of ignition timing/cam timing.

Thanks for all the feedback.

[fastfredracing]

If it makes you feel any better, I remember struggling with trying to set the cam sprockets up on the last one I did. I had to read the procedure several times before it made any sense to me.
There is no way around it either. If you try to leave the sprockets bolted to the cams, you cannot replace the cam seals, and have no real way to ensure that you have them seated correctly when it goes back together .
Good luck !

[LEAKYSEALS951]

Originally Posted by fastfredracing

If it makes you feel any better, I remember struggling with trying to set the cam sprockets up on the last one I did. I had to read the procedure several times before it made any sense to me.
There is no way around it either. If you try to leave the sprockets bolted to the cams, you cannot replace the cam seals, and have no real way to ensure that you have them seated correctly when it goes back together .
Good luck !

Thanks! The struggle awaits!

[Dansvan]

Advancing the camshaft increases low end torque. Retarding the camshaft increases high end torque. The more efficient the combustion chamber is the less ignition advance is needed.

[sammyg2]

This apply to both cam and ignition timing to varying degrees (get it, degrees? i crack me up):

1) Knock sensors adjust timing for optimum performance. Ability to bun different fuel blends without screwing up performance for all of them requires variable timing.
2) Lower RPM needs retarded timing for max torque, high RPM needs it advanced.