[BRY65]

I agree with Greg. The stock mufflers are the primary restriction in the stock engine system. They provide the necessary backpressure to allow the stock system to run. If you change to the K&N filter, the muffler backpressure will be the same and thus a neglegable (if any) amount of additional air will flow thru the new filter. No real hp gain, but you will have the convenience of a rechargeable filter.

 

[BRY65]

If the pipes are the primary restriction and limit the airflow, then why do folks get better performance when they run topless? (or is that only w/ race tuner / pcIII, etc?)It seems that they would not be able to increase the airflow if the pipes limit it that much.

The improvement is with the addition of low restriction pipes and a different flash / tuner. The system restictions are first the stock mufflers, second stock air filter, third stock air box cover. Modifications to the last two without changing the mufflers and map will not gain any hp advantage.

 

[BRY65]

I have to disagree.You will notice a difference with just the filter and topless.It is snappier off the line,and better throttle response.The stock filter is made from paper.The K&N is a oiled cotten filter.It flows more air than a paper element.The more air you can get into the engine the more power it will make.Yes it will run leaner.
And yes you will need some kind of fuel richment device.

Vinny, how much additional hp do you think that you are getting? ChopperSteve is claiming only a 2-5 hp and 5 ft-lb torque increase with his muffler mod and a reflash. I doubt that you will get much of this without removing the muffler backpressure.

 

[BRY65]

It's really noticable down low in the rpm's.Itwas only mybe 1 or 2 hp.It gave it more throttle response.And a cool sound of rushing air being sucked in, when you snap open the throttle.

Vinny, I'm sure your right. It's possible since at low rpms, the backpressure hasn't completely built up yet. I'm sure that as rpms increased, the hp advantage decreasd or lost all together. Have a good one bud...