Question for the masters about timing! Read plz

[Jon K]

Hey guys.

As some of you know I am in the process of supercharging my M50non Tu. The cams in this car are technically lumpier than in the M50TU for obvious reason (lack of vanos, for one). I am on the forced induction boards and such and I read people retarding the timing by +2 degrees. The example I read was particular to the M30 motor, which has only one cam to begin with. Having dual cams, is there any gain in this for an forced induction setup? And which cam would i retard, im assuming the intake but I could be wrong. Also, I haven't ever messed with timing. Is it even possible to retard the timing of an M50 non TU? Any help is appreciated.

[Martin in Bellevue]

With adjustable cam gears, you could dial out the overlap that blown motors don't need. I'd try an initial retard of the exhaust cam in your situation.
I'm no timing master, try Graham A Bell's book on performance engine setup.

[MSM]

You could also try Graham A Bell's reasonably recent book on forced induction performance tuning, its green and it's called "Forced induction performance tuning" :D

Very good book that covers most forms of forced induction fairly well. Alongside all the new FI specific related content, the book contains a lot of content that was in his earlier book "Four Stroke Performance Tuning", but it has been edited and updated for forced performance applications. The book seems somewhat more technical and in depth than Corky Bell's "maximum boost", but its always good to have a couple of sources of similar information to base your own understanding of something on. :)

[632 Regal]

Personally I would go with the adjustable sprokets. Set the cams straight up where they were initially designed and then play with timing settings. Don't guess where you think they should be without getting the baseline first. Cam timing sometimes doesn't do what logic says it's supposed to. Rule of thumb is advancing lowers the range while retarding raises the range, didnt happen that way several times for me.

[Jose]

Rolling road. That´s basicly what you need when playing with timing. In that way you can really see if there are any changes. Bare in mind that altering the timing using adjustable camsprockets also changes the distance-timing between valves and pistons. If you are to play with this on a charged engine, and it fits in the budget, replace the valve springs by motorsport ones. This will keep the valve train strict enough on any possible overreving.
We played with the timing too on the bi-turbo M30 on the rolling road but we set it back to standard. The engine lost power instead of gaining any at all. Be carefull for detonation and don´t forget to change your plugs for colder ones.

[Jon K]

Rolling road. That´s basicly what you need when playing with timing. In that way you can really see if there are any changes. Bare in mind that altering the timing using adjustable camsprockets also changes the distance-timing between valves and pistons. If you are to play with this on a charged engine, and it fits in the budget, replace the valve springs by motorsport ones. This will keep the valve train strict enough on any possible overreving.
We played with the timing too on the bi-turbo M30 on the rolling road but we set it back to standard. The engine lost power instead of gaining any at all. Be carefull for detonation and don´t forget to change your plugs for colder ones.


The M50 non-vanos that I have has double valve springs, it revs 7200rpm without issue by default.

[Jose]

I know it does, have the same engine in my ´92 325 coupe, still the difference between std and uprated springs is big. It´s a big job to do anyways. I found it a **** thing to do but had no choice as I fitted schrick cams.