Hey everyone, I'm new to the board and I have a question and Im hoping you guys can help me out. I'll start out by giving ya a little background info.. I used to own a 02 mustang GT with a forged motor and a kenne bell. Now i hang around a mustang speed shop here in south florida and ive seen a lot of fast car's being dyno'd. now my questions is why are V8 powerbands so flat while i see a lot of s2k's are peaky.

(by peaky i mean they start off very low and just drastically spike up at the higher rpms..)

i dont know anything about s2k's are any other 4 cyl so can someone help a noob out here :]

 

Well, we have variable cam timing aka vtec.. At like 6200 rpm the cams chane over an we get a boost in power. Plus, 4 cylinders will always have a pretty linear gain in hp unless they have a huge turbo slapped on. Where as you v8 owners have a big spike kinda early and is kinda flat on out. You also gotta remember it is visually amplified cause we rev way higher than most v8s. An ap1 s2k revs to 9k

 

ohhh ok, that makes sense..I was always confused as to what vtec did lol. someone told me it had different cams, someone else told me a the injectors just feed more fuel, someone else even told me there is a 5th piston that kicks in at a certain RPM...lol i was starting to think this stuff was complicated.

thanks for answering though!, I have to learn these things seeing as im looking for an s2k! Gas is ridiculous, and my old Stang couldn't take a turn if it got hit on the opposite side by a semi throwing it into the turn and even better was my stopping. Ford brakes are guaranteed to stop the car...eventually..lol

Im really stoked about having something fun to drive through turns not just in a straight line!

 

A tuned NA S2000 has a very flat powerband (torque curve) with lowered VTEC. Many of the turbocharged S2000's have very flat torque curves once they reach full boost. The SOT supercharger has a flat torque curve as well. Flat torque curves = an increasing line for horsepower.

Most of the supercharger kits exaggerate the curves a lot.
With a centrifugal SC, the torque curve increases linearly with RPM (just like boost). That causes the horsepower to skyrocket with RPM. That's why the superchargers look peaky.

Most V8's and V6's in domestic cars have lots of torque at low RPM which falls toward high rpm. That causes a fairly flat horsepower curve.

Flat torque curves are a sign of a motor that is efficient at a wide range of RPM. A torque curve with significant dips at the high or low end means that the motor isn't efficient at that RPM. Most big V8's are very efficient at low RPM, but choke as the RPM rises. (torque is a nice indicator of VE)

Tim

 

Damn, we have a convert! Welcome to the fold.

BTW:
http://s2000.byteserve.com.au/images/vtec_str.mov

 

what causes the pin to move over so that your using the vtec lobe?

 

It's pushed by oil pressure which is switched by a solenoid. The solenoid is triggered when certain conditions are met. Something like 6000rpm, 85% throttle and engine temp of 85 degrees centigrade I believe.