What is the difference between the two and more specificaly in the 4 pot range. Such as will M42 cams work on a M44?

Bahh this is a bad subject. People still think that Big NA cams are bad for FI. Not true and I will have tons of people here come and argue in the next few post's. Turbo cams are usually a waste of cash. Just go visit Honda tech. They figured out a long time ago that big NA cams work well with turbos. those old theories are just that theories. Long story short Cams work with turbos. maybe not Non idle .5 inch or bigger lift but good size def works and works well. It is just more time to stuff air in. It seems there is a direct connection between high NA power and high FI power. Tuning is the biggest issue.

Bahh this is a bad subject. People still think that Big NA cams are bad for FI. Not true and I will have tons of people here come and argue in the next few post's. Turbo cams are usually a waste of cash. Just go visit Honda tech. They figured out a long time ago that big NA cams work well with turbos. those old theories are just that theories. Long story short Cams work with turbos. maybe not Non idle .5 inch or bigger lift but good size def works and works well. It is just more time to stuff air in. It seems there is a direct connection between high NA power and high FI power. Tuning is the biggest issue.
:lol
Most of us run stock NA cams.

ya... but what about superchager aplications?

Bahh this is a bad subject. People still think that Big NA cams are bad for FI. Not true and I will have tons of people here come and argue in the next few post's. Turbo cams are usually a waste of cash. Just go visit Honda tech. They figured out a long time ago that big NA cams work well with turbos. those old theories are just that theories. Long story short Cams work with turbos. maybe not Non idle .5 inch or bigger lift but good size def works and works well. It is just more time to stuff air in. It seems there is a direct connection between high NA power and high FI power. Tuning is the biggest issue.

Street turbo aftermarket cams are usually higher lift, but not as much more duration than stock as a street naturally aspirated aftermarket cam. Significantly more duration means significantly more overlap. Sure, the intake will be open so more air can go in, but the exhaust will be open at the same time so that air can go right back out without building much more cylinder pressure and without making much more power.

Cams like those in the BMW E36 M3 S52 are good street turbo cams. They may not be aftermarket, but they are a big step up from the cams found in the BMW E36 standard 2.5 and 2.8 liter non M3 motors. They have more lift, but not tremendously more duration. I think that one could go a little further without suffering much in the way of consequences to gain some more upper end power.

Your experience in Honda motors may not be univerally applicable. Many of those Honda motors make about 100 lbs of torque and don't even get there until about 6000 rpm. Forget about the midrange -- there isn't one. All the talk about valve overlap bleeding off cylinder pressure on a street turbo that makes great low to midrange boost is not so applicable.

You are almost into the non-street turbo category already with the Honda -- you guys have nothing to lose since you do not make any power until high rpm. With a non-street turbo, the low end does not matter. The turbo is so big it won't be making any boost there anyway. The midrange is pretty much the same thing, just like on some of the stock Honda motors. Its all about upper rpm power. In the upper rpm, things happen so fast that the overlap is not really a problem -- and the radically turbocharged Honda with big NA cams makes great power. For non-street turbos designed to sacrifice the low end and midrange and to make massive high rpm power, whether Honda or BMW, the big NA cam is a great choice.

Philip Bradley

I fully understand overlap and lift. I was more speaking in terms of large gains by running cames that people said "BAD FOR FI". People are finding that cams are good. Yes I understand you guys have been running stock Na cams. Like i stated there is always an upper limit. I mean lets face it a cam with huge overlap will not work good as you stated. I was just pointing out that there alot of previously "wrong" choices that have been found to make great improvements Honda or BMW. I only used Honda as an example as they seen to have experimented a bit more than other makes.:)

Running a larger cam will only benefit if you have the right setup, like a tubular exhaust manifold and a properly sized turbine housing along with a free flowing exhaust. Larger cam with a log manifold and restrictive turbo and exhaust will create to much back pressure and reversion.
I'm in favor for running a larger cam even though was told not to. At the moment running a 294 duration cam from the original 274. I picked up 40rwhp just with a cam swap with same amount of boost.

It usually isn't a big issue until you get into really high boost pressures (20-30 psi) and high duration race cams. A mild street cam will work great. I think the reason most bimmer guys don't run aftermarket cams is because the stock cams are actually pretty radical anyway.

:) thanks for the info guys. wow 40 whp is a big gain nice werk.