Bmw M50 Headers

[cwbaader]

Am in the process of getting a check to clear for my current car and I will work on this after that clears. I am really anxious to see what happens when the vanos kicks in. Anyone know at what RPM it changes (stock) and perfered (modified)?

[digger]

i think the vanos advance disables at around about 4000rpm to 4500rpm based on heresay. i dont know how much it moves exactly other than that catams suggest the ECL is 101 fixed and the ICL goes from 110 to 85 ICL when advanced. the stock cam is 195 at 1mm so my assumption of 190 @0.050" is about right.

http://www.catcams.com/products/camshaf ... TUP_id=193

[Hairyscreech]

Are you using the M3.3.1 ECU (red or silver label 413)?

If so it is not at a set RPM but as a given calculated load.

For any throttle opening/RPM/acceleration rate/air flow the ECU generates a "load" value that is used to determine the fuel and timing needed, when this load value goes over a certain point the vanos is switched.

Trouble with that is the ECU uses a map for the load points to switch on and a map of load point to switch off, thus it can be on or off in a range of load/RPM values.

I don't have Tunerpro on my work PC to grab the graphs off but I will try to take a look for you later tonight.

Pretty sure it is retarded-advanced-retarded.

[cwbaader]

Spoke with a very knowledgable tech yesterday. At idle, cam timing retards to make motor idle better, then advances to a set point (actually where cam is timed statically) when at cruse, and then at WOT can advance to as much as 122 degrees lobe separation. He seems to think that point is about 46-4800rpm. I would think bringing it in sooner, say 36-3800 would make more power/wider power band.

[naukkis79]

M50 Vanos is on/off. When it's on it will advance intake cam timing 25 crank degrees. WOT std timing is advanced between ~1200-4200 rpm. With more cam or better headers it's better to keep cam advanced to higher revs( more overlap).

There's also different table for part throttle, cam is put in advanced position in middle revs when engine load is high enough.

[cwbaader]

Going to be interesting tuning the new DIY MegaSquirt for this car.

[digger]

M50 Vanos is on/off. When it's on it will advance intake cam timing 25 crank degrees. WOT std timing is advanced between ~1200-4200 rpm. With more cam or better headers it's better to keep cam advanced to higher revs( more overlap).

There's also different table for part throttle, cam is put in advanced position in middle revs when engine load is high enough.

i agree with this it will be max advance(lowest ICL value) lowend to midrange rpm and retard (higher ICL value ) above some set rpm, i dont think the exhaust will have as big an effect on the optimal adv/ret switch point as a cam with more duration will (more duration means you can keep the IVC more optimal for higher rpm while utilizing more exhaust pull to scavenge assuming primaries are tuned with correct length so its less of a tradeoff), but i dont tune these engines. i do know a few guys who do and could probably advise what mods affect switch point etc.

it doesnt seem to have a big effect on the pipemax recommendations which correlate more to do with peak hp rpm and absolute hp (i.e. engine size,rpm and VE), of the cam specs duration seem to be the best influencer

[Hairyscreech]

I opened up the BIN files I have from the 413 ECU earlier and the graph below shows the standard Vanos strategy.

The Load as noted before is abstract, ECU calculates this from primarily the MAF sensor but also from the TPS and other senors. (I believe air temp, coolant temp and acceleration rate of the RPM is also a factor but not got a solid enough disassembly of the ECU code to be sure yet).

Red line is the trigger point for the vanos solenoid turning ON, On means retarded.
Blue line is the trigger point for it turning OFF and returning to the "advanced" or stock timing.

It's not quite as simple on the stock ECU as "on above Xrpm" for the MS you should be able to do a dyno run with the cam advanced, one with it retarded and then pick your switch points where the torque curves cross.

[naukkis79]

It's not quite as simple on the stock ECU as "on above Xrpm" for the MS you should be able to do a dyno run with the cam advanced, one with it retarded and then pick your switch points where the torque curves cross.

Or you can log live data and from maf-flow or calculated engine load you will see optimal switch points.

Also M50/M52 vanos is extremely slow to switch, for M52 Siemens DME you could flash 41.2 firmware from US M3 which lets you map vanos switch points per gear so you could trigger vanos at WOT to switch at lower rpm at lower gear to have actual switch to happen at desired rpm.

[cwbaader]

Well, after a couple of years I have come back to this again. No more stock motor...although I'm running stock at this point with only a PNP MegaSquirt. Making 200 at the wheels even with cast iron headers.
Now for the new stuff. Am running SCCA Limited Prep E Production. engine allowance is .5" lift at the valve, and 12 to one compression ratio....that tends to muddy the waters some. Bottom end is no problem, and the headers I'm running are equal length but 14" primaries with 1.58"ID. Secondaries are about 2.17"ID and unequal length. I suspect the secondaries to be too small and prior experience tells me you can extend the power curve by running different length collecotrs merged into a single exhaust. Current power band is good a 4500, great from 5000 to about 7200. What I'm looking to do is increase compression and cam with the goal of making in the neighborhood of 260+HP. Not many off the shelf cams available, but I'll try plugging in to the example and see what drops out.
Thanks for all the help...I'll keep trying.

[digger]

14" primaries are too short. something 24-26" is more intune with the power band

[cwbaader]

Actually on my first pass on PM the 5th harmonic covers that diameter. What I am wondering about now is the recommended 3"+ collectors.
Note...takes a really good fabricator to get 25-27" primaries in the room available (think KromerKraft)...I'm not that guy.

[digger]

PM collector diameter recomendations are always huge, its hard to see a twin 3" being better than twin 2.25"

s50b32 euro headers would be closer IMO id just adjust the secondary length to 2nd harmonic and merge to a single 3" tailpipe.
the longer primary scavengenges a bunch better through the midrange and despite being a tuned length the shorter runner's timing of the wave is ok at the very topend but the scavenge wave strength is lower in magnitude and narrower