Infidel

I like to look at it this way:

If you're putting out 5#s of boost at 6krpm (like my car), running the SAME pully on a 5.0L V8 (with the same size crank pulley) will put out only 2#s of boost. (2.5 times the volume of air/rev, and pressure and volume are linearly and inversely related to each other at the same temperature).

The reason why headwork increases power is because you actually LOSE pressure flowing though the head (because it is restrictive). Very similar to the pressure drop you see across an A/C, by improving the flow characteristics of your head, you lose less boost, allowing more air into your cylinders, allowing you to make more power.

Just two different ways of looking at the same problem.

Silver S2k4

This is a super educational thread. I have an 04 with AC and got the 9lb pulley from tech2 which will really only push about 7.3lbs into the motor. You're saying that headwork will allow for more boost to be put into the motor more efficiantly right?

If I lets say port and polish my head, would i see any more boost, would it get to full boost quicker, or just "allow" me to run more with smaller pulleys?

Also about the fuel. Its not realistic for me to get the EMS right now but would I need any kind of better fuel managment other than a vafc with stock injectors?

Infidel

I don't think l8brakr is running FI. I had around 17000 miles when I put the S/C and 4.77 gears on. I had around 22000 miles when I got the high boost package. I've put around 1000 miles since then. (It's about 45 miles each way between work and home).

Personally, I think the wear on a highly boosted S/C'd motor is much less than your average turbo kit. I think Sideways' car is running a 14# pully on a stock bottom end for several months now, with no problems. Just like how everyone likes to talk about area under the curve on dynos, wear is directly related to the "area under the boost curve".

I highly recommend upgrading your clutch. Although you CAN do this with the stock clutch, unless you do perfect, rev matched upshifts, you'll start to glaze it before too long, IMO.

Sideways

With a port and polish you should see less boost if the engine is more efficient.

landfighter

thanks,Infidel...sorry for the mis-post,my bad

Infidel

The easier it is to push air into your cylinders, the more air mass you will get in there, which will allow you to make more power. Greater airflow in a head is greater efficiency. Since the amount of air the S/C pushes is constant at a given RPM, if more air makes it into the motor, the perceived pressure (boost) will be lower, but power will increase.

The smaller the pulley you put on your S/C, the more airflow you're imposing on your motor, increasing both power and wear.

Incidentially, are more efficient head will ALSO increase wear on your motor. A more efficient head will flow more air, which will increase cylinder pressures, which allows you make more power, which is more wear. (I.e, power ~ wear).

In any case, the there are only 2 things you can do, IMO, to "allow" you to run more boost: An EMS and building the bottom end of your motor. The EMS allows you to "tune" and prevent damaging things like detonation, building the motor makes it stronger and more capable of sustaining higher cylinder pressures. Anything else you do is geared towards pushing more air mass into your motor. More air = more power.

You've got more balls than I do running a 9# pulley on a stock fuel system. If you're running a high boost and a ricky-rat fuel system, I hope you're at least checking your plugs for detonation on a VERY regular basis. If you can't afford an EMS, how can you possibly afford a blown motor?

I love that saying:
Power, Price, Reliability: Pick Two.

Sideways

[QUOTE=Infidel,Apr 14 2005, 02:21 PM]