forced induction question

[itsbrokeagain]

if you have that much exhaust back pressure then your exhaust is too small.

look at what the guys in scandanavia are running. there is a reason people here struggle to produce 300whp and people over there do 500whp in their sleep.

+1 fucking million.

[blueapplesoda]

http://forum.miata.net/vb/showthread.php?t=243805

http://www.turbochargedpower.com/Camshafts.htm

FI Cams...not NA Cams. Although mild NA Cams work pretty well too.

from max boozd

Camshafts
Make no mistake in the fact that the turbo performance cams are very different from atmospheric performance cams. The characteristics of long duration and high overlap for atmo cams are unwelcome in the turbo system. The street turbo, which is generally small, operates on exhaust manifold pressure somewhat higher than intake boost pressure. This situation, when presented with long-duration, high-overlap cams, creates a huge amount of reversion. Thus the "turbo cam" tends to become a low duration, very limited overlap camshaft..

[nando]

yes, that is the conventional wisdom.

conventional wisdom also says you should run a small turbo for faster response (typically an expensive garret BB turbo). But the reality is it ends up restricting the engine, where a larger, more efficient turbo design would spool faster and produce more overall power with a broader torque curve.

the longer duration cam will also let you run a higher static CR and further enhance the torque curve over a broader RPM range. There are lots of claims of 600hp 4 cylinder engines (for example) that make that peak number for a very narrow RPM range (~300rpm) and then die horribly after (due to the small turbo) in addition to being flat in the low RPM/cruise range.

[Spinning Tires]

http://forum.miata.net/vb/showthread.php?t=243805

http://www.turbochargedpower.com/Camshafts.htm

FI Cams...not NA Cams. Although mild NA Cams work pretty well too.

from max boozd

Camshafts
Make no mistake in the fact that the turbo performance cams are very different from atmospheric performance cams. The characteristics of long duration and high overlap for atmo cams are unwelcome in the turbo system. The street turbo, which is generally small, operates on exhaust manifold pressure somewhat higher than intake boost pressure. This situation, when presented with long-duration, high-overlap cams, creates a huge amount of reversion. Thus the "turbo cam" tends to become a low duration, very limited overlap camshaft..

Thats pretty much what i've been saying the whole time but no one gives a shit. I guess some people would rather learn from their mistakes

[whterice]

thank you for this information

[nando]

Thats pretty much what i've been saying the whole time but no one gives a shit. I guess some people would rather learn from their mistakes

like I said, look at what the E30 guys in scandanavia are running. You'll see a lot of catcams 280s and schrick 288s, making several hundred HP at the wheels.

running a turbo cam isn't "wrong" (depending on your goals) but neither is using an N/A cam.

[Spinning Tires]

point taken