what kind of impact are s52 cams going to have when i turbo my 328 later this year? will it be worth the $500 to get the stock 328 cams put back in?

You will feel and see a difference if you put the S52 cams in. With the mods you have, and maybe add the M50 manifold, you will see a nice difference. I say go for it.

Leave the cams in, they will add power over the stock 328 cams.

i thought you want a less agressive cams in a turbo car. i dont think card counter is using m3 cams in his monster turbo 328

You will feel and see a difference if you put the S52 cams in. With the mods you have, and maybe add the M50 manifold, you will see a nice difference. I say go for it.

i already have the cams and manifold:) just not sure if the cams will be anygood in a turbo setup.

leave the manifold and put stock cams in

so would that mean m3 guys should put in 2.8/ 2.5 cams?... interesting maybe someone should try

im not very educated about the relations between cam/turbo... researching

be nice if Def could chime in and enlighten me...

i thought you want a less agressive cams in a turbo car. i dont think card counter is using m3 cams in his monster turbo 328

I have heard different opinions on this, but a high rpm/ high power N/A cam uses alot of overlap. Overlap is the number of degrees in rotation where the intake and exhaust valves are both open, in an N/A car the incoming intake charge helps to expedite the exhaust gas out of the cylinder. I think the concern is that with too much overlap(like you would get with N/A cams for a high rpm grind) the high pressure could force the intake air out the exhaust port.

i thought you want a less agressive cams in a turbo car. i dont think card counter is using m3 cams in his monster turbo 328
you do, but unless you're going for really big power, its not necessary to bother changing the cams back....I mean, have you ever heard of any turbo 3.2's running 2.8 cams?

the 2.8 cams have a long lift duration whitch is good the the lift is less. so you be better to have some1 spec your current m3 cams i think going that way would be more cost efc.

I kinda have the same question but I'm going SC'd and I have cams as well... I'm not really worried about any negative impact on power since the s52 cams aren't what you would consider agressive but I'm kinda worried about the custom software... I talked to Steve Dinan at the LA autoshow about it and he said it isn't really a problem, he didn't sound too assuring though.
what kind of impact are s52 cams going to have when i turbo my 328 later this year? will it be worth the $500 to get the stock 328 cams put back in?

Is the duration of the M3 cams any longer? Or is only the lift different?

More lift is good, more duration *Could* be bad.

I kinda have the same question but I'm going SC'd and I have cams as well... I'm not really worried about any negative impact on power since the s52 cams aren't what you would consider agressive but I'm kinda worried about the custom software... I talked to Steve Dinan at the LA autoshow about it and he said it isn't really a problem, he didn't sound too assuring though.

We just finished tuning our Eurosport Twin Screw system for the 328i on Uli's car which happens to be running M3 cams and it worked great ~332whp at 9psi boost (with a slipping clutch). I don't think the mild differences between the 2.8L vs 3.2L cam will have any significant effects and if anything I'll bet when tuned right they would have a positive effect on a Turbo 328i. However, the only way to know for sure would be to test and tune the system both ways.

just rememberthat a factory "hot" cam is never that hot.

it should give you some good mid range and top end grunt.

just get a nice big exhaust to take full advantage, around 3" will be good.

I agree, i feel the m3 cams would help benefit the motor more. m3 cams arent radical cams with high amounts of overlap lift. It wouldnt be practical. However seeing the lift/duration/overlap specs on both cams would help a great deal to come to this conclusion.

just rememberthat a factory "hot" cam is never that hot.

it should give you some good mid range and top end grunt.

just get a nice big exhaust to take full advantage, around 3" will be good.

yeah, thats what i was hoping. after all the m3 does pretty well with the same cams, although i bet card counter would be using them if they would add that much benefit. sounds like it is not worth the trouble to put the 328 cams back in.

yeah, thats what i was hoping. after all the m3 does pretty well with the same cams, although i bet card counter would be using them if they would add that much benefit. sounds like it is not worth the trouble to put the 328 cams back in.


Its alot easier to just turn up the boost than to go through the trouble of swapping cams to net maybe 10whp over stock.:devillook

maybe after he cant extract any more possible polwer outta his setup but till then he is probably happy with his stock cams. Im sure he can chime in and tell his opinion.:buttrock

I dont think the cams will make that much diffrence either way + or - 10hp even turbo cams add only a little to our setup.If the 3.2 cams are in there leave them
if it will make you feel better swap them.One thing I do reccomend is the m50 manifold.

I dont think the cams will make that much diffrence either way + or - 10hp even turbo cams add only a little to our setup.If the 3.2 cams are in there leave them
if it will make you feel better swap them.One thing I do reccomend is the m50 manifold.

already have the manifold:) i will just leave the cams in if it will not make much difference:buttrock

It would be nice if someone could post valve events along with duration at .050 lift for both cams :)

There's a few things different with cams regarding FI, specifically turbos. As you know turbos can create tremendous back pressure depending on AR and exhaust manifold design, this makes the beast different in nature to SC and NA cams who don't have to deal with relative positive back pressure, only scavenging and flow-to-restriction points.

With positive back pressure in the exhaust system, very simply said, on the top of the induction stroke where both valves are open (intake valve starting, exhaust valve closing) you are at term that is defined overlap. If you look at both cams on same axis, the little triangle that is formed between two lobes is the point where both valves will be open. At this point, a very restricted exhaust setup (say a small log manifold on a small AR T3/T4 style turbo) can actually force exhaust back into the combustion chamber, which is known as reversion.


There's a good article on camshafts on how stuff works, I like to refer to it since it has pretty good visuals, things are easier with pictures. :) http://auto.howstuffworks.com/camshaft.htm

Any who, back to cams, the main attribute that determines overlap is the the valve events, known as IO(intake opening) IC (intake closing) EO (exhaust opening) and EC (exhaust closing).You can usually find these with the cam card often included with the cams. With reasons above, we want our exhaust valve shut before we open our intake valve to minimize chance of reversion.

Another thing is duration, or how long we hold the valve open. There are many theories and speculation but it comes down to trial and error for your application. Some people believe in a matched duration (often noted as 270/270 advertised - keep in mind, that is advertised, no at .050 lift). Basically, the thought is that a well designed and non restrictive exhaust setup will make best power given equal duration. Some traditionalist say that running a longer exhaust duration will provide more energy to spool the turbos and not cut down on dynamic cylinder pressure (keep in mind, a longer intake valve duration will lower dynamic compression, delaying max engine VE significantly). Finally, there are those who believe in induction duration bias. Mainly these are folk with engine specific cams, where the heads will flow well on the exhaust side, but intake side stinks. Mainly they are trying to achieve all the flow they can.

Now, an NA cam can have the same lift and duration as a turbo grind, but the valve events will be very different. NA engines rely on scavenging, they rely on overlap for the exhaust pulse to suck out the remaining air in the chamber and pull new air in. This could hinder performance in a turbo car, since again, the exhaust pressure may come back into the system, and overcome the intake pressure (boost psi)

SC cars have forced intake pressures, and need not worry about scavenging, since most of the air is forced out. They can get away with running the overlap normally associated with NA cams without serious negative effects.

Many engines (at least all that I have seen, and that is quite a few) will benefit from additional lift. Flow vs lift is always dependent on engine, but most FI cars like to gulp air down. Some say let the turbo do the work, others just have it because its required on most dohc style cams with moderate duration (small cam lobe). Some are just crazy and want it all.

Cliff Notes: Minimize overlap on a turbo car, and consider all children at play. :buttrock

Nate

Also, VANOS does indeed change overlap by shifting the intake cam events to an earlier time. This makes the motor more efficient (higher dynamic cyl pressure @ low to mid load/rpm by closing the intake valve sooner == more torque at lower rpm)

If going with a large setup, it would be an asset to offset large cam duration and a large turbo (and exhaust AR)

LOL, sorry but I must throw this out there for minds to feed on.

More intake duration will lower dynamic compression, keeping a high static CR motor a tad more friendly to boost. 8.5 is traditional FI CR, but some may think 9.0:1 with large cams a better bet. ;)

good right up:)

good right up:)

Hope it helps. You will find specing cams can be a black art, but keep your wants and what you're willing to sacrifice ($, spool time, peak hp, area under curve etc ...) in mind and make a decision. It also never hurts to have a sense of community - hats off to AA and ICS for sharing dyno plots of many verse setups. :cool

Stay with the M3 cams. They aren't all that "hot" and will suit a turbo nicely. Turbo cars like bigger cams just like an NA car(but with a slightly larger lobe separation angle because the overlap filling isn't very momentum based).

All kinds of factory turbo cars come with cams just as "hot" as M3 cams, and they get huge gains with bigger turbos by going to higher duration/lift cams. In fact, durations as large as 288* and such on both intake and exhaust aren't uncommon.

Stay with the M3 cams. They aren't all that "hot" and will suit a turbo nicely. Turbo cars like bigger cams just like an NA car(but with a slightly larger lobe separation angle because the overlap filling isn't very momentum based).

All kinds of factory turbo cars come with cams just as "hot" as M3 cams, and they get huge gains with bigger turbos by going to higher duration/lift cams. In fact, durations as large as 288* and such on both intake and exhaust aren't uncommon.

288 advertised duration possibly, 288 @ .050 wouldn't idle at anything under 2,000RPM. LSA is really relative, but mainly based on the fact you can't extend lift without a bigger base circle on most dohc cams.

288 advertised duration possibly, 288 @ .050 wouldn't idle at anything under 2,000RPM. LSA is really relative, but mainly based on the fact you can't extend lift without a bigger base circle on most dohc cams.

Yes, which is a big cam for a 4 valve modern design combustion chamber that flows very well.

I'm not really following you on how LSA is related to base circle size...

thanks for all the inforation given, Def and Nate At MOF.

Yes, which is a big cam for a 4 valve modern design combustion chamber that flows very well.

I'm not really following you on how LSA is related to base circle size...

I guess related was a poor choice of words, but the two effect each other like a married couple. In most 4V DOHC heads there is very little contact patch with the follower/rocker. You usually won't see higher lift cams with near stock duration, nor LSA. When you increase lift, you make the lobe base circle smaller, increasing the ramp rate, which increases the theoretical lift created. The problem with this, especially on 4V DOHC heads is that to much of a ramp rate will cause exponential mechanical lash. You don't have a lobe anymore, you have a rectangle with a rounded tip. Grinders will tinker with LSA to compensate for a few things. The first is mainly ramp rate, second is to keep factory engine management happy, as steep exhaust pulses can confuse a closed loop system thinking it's running way to rich, and will play with long term and short term fuel trims to try and compensate, creating a tuning nightmare.

Still trying to figure out why cams for these cars cost 1000+, but I guess that is part of the BMW tax.

Yes, which is a big cam for a 4 valve modern design combustion chamber that flows very well.


You make a good point here. Some engine mappers fall victim to Supraitis, bigger is better. You'll see that many were making 500whp a year ago on huge builds, where now many are making 500whp on a stock long block with much refined engine management.

Bigger sometimes does not mean better :)

To add on this, these are from BMW World, they seem to be credible:

M52B28 - Single Vanos, Mid 90s- 98
Displacement (liters)2.793
Bore/Stroke (mm)84/84
Valve Timing (IO/IC)1°atdc/49°abdc
(EO/EC)39°bbdc/9°atdc
Valve Lift I/E (mm)9.0/9.0

Square bore/stroke ratio, with a forged crank, aluminum block with dry sleeves, killer combo :buttrock

I can't seem to bring up cam specs for the S50/S52, can anyone find them?

Found some stuff on Schrick Cams, they offer good information on reading cams and understanding lobe geometry.

http://www.turbo-garage.com.ua/garage/techinfo/catalogs/Dr_Schrick.pdf


If someone is thinking of running Schrick's, they have significant overlap, hopefully the motor and turbo are sized and built accordingly.

We just finished tuning our Eurosport Twin Screw system for the 328i on Uli's car which happens to be running M3 cams and it worked great ~332whp at 9psi boost (with a slipping clutch). I don't think the mild differences between the 2.8L vs 3.2L cam will have any significant effects and if anything I'll bet when tuned right they would have a positive effect on a Turbo 328i. However, the only way to know for sure would be to test and tune the system both ways.

awesome news josh! finally starting to button up the screw install on my car (lots of health issues in the new year). i'll give you a call later on regarding the software. :D