4-1 exhaust, better performance?

[grifff]

I have an old set of 4-1 pipes. My old pipes are toasted from the exhaust manifold, to where they turn under the frame. I was was wondering how 4-1 pipes give you better performance. I've just taken everyones word for it, without knowing why. From what i know its all about air flow.

[dragxs11]

Hi Grifff, My understanding is that you may grab a few extra top end horses, but the primary advantage is weight loss. And of course that cool Ferrari sound

[Dennyz]

On the extreme side, I feel the 4:1 system I have on my "F" is a very effective exhaust solution. Possible the most efficient exhaust system for the XS on the street. And, providing a more modern look to the old horse.

The down side is that it requires significant fabrication and modification to install. Plus, may not provide the looks many are interested in. It is definitly not a "bolt-on" system.

It is a painted Jardine 4:1 with a 2 1/4" header pipe connected to a Titanium R1 muffler. The system is very light and very quiet.

It provides great power (across the entire RPM range) and fuel economy. I have created 4 of these systems to date. In all cases, the rider has noticed a significant improvement in performance and fuel economy.

It one case (pictured), the bike has a K&N OEM replacement filter, drilled air box and stock jetting. He gets 40+ mpg and great low end power. His high RPM (5k+) power is pretty flat, but should be expected with stock jetting.

I attribute the performance improvement to incredibly low back pressure. The R1 muffler is designed to support 145hp engine and accommodates the XS's 95hp very well. With the large header pipe and low restriction muffler, the XS motor is running as close to an open header as possible. If one of the aftermarket R1 replacement muffler where used, the system would provide even better flow. Of course, would be more $$ and produce more sound.

-The Jardine header - $125.00 (eBay)
-The 2 1/4" header pipe and muffler mount are fabricated from mandrel bent steel tubing ($25.00) and aluminum bar stock ($10.00).
-Stainless Steel clamp- $5.00
-Titanium R1 Can - $65 (eBay)
-Can of Krylon BBQ Black - $5.00

The stock muffler/buddy peg mount must be cut off to provide clearance for the can. Also, the break lever must be modified to clear the header pipe. The bike pictured has had the stock aluminum muffler mount modified to provide a new buddy peg location.

Basic tools: cutoff saw, band saw, and mig welder (steel and aluminum).




Note: - this is an updated picture of the system Denny has on his bike, not the picture he originally posted.

[chevy45412001]

air flow?

I beleave you mean exhaust flow? Weight savings is one advantage,but also some manufacturers claim better exhaust scavenging takes place with a 4-1 set up. Were the exiting exhaust actualy pulls the exhaust from the engine alowing more air fuel to enter the engine.A stock system has a more restricted flow(more back presure) Always remember an engine is an air pump,the more air and fuel you can shove in and out the more power you will develope. Thats one of the reasons a good head job can gain A LOT of power. bigger valves =more air in and out.Air does not like to change dirrection xspecily in an engine(reason why a good head job will address short turn radius on the intake side of things) Another reason why NASCAR spends millions of dollars in a wind tunnel to cheat the air.ITS all about the FLOW,GO WITH THE FLOW...lol (I don't know if any of what i've said is true its what i've been told and read, besides that i'm XStreamly close to changing to XSesiveus Maximus or whatever)

[chevy45412001]

Sweet

by the way i like that exhaust system there Dennyz looks awsome.

[skids]

Re: air flow?

I contend that if you get good exhaust scavenging, it will be at a particular rpm range, and if that happens, the impulses will cause interferrance at other ranges - hopefully at ranges you don't really care much about.

Originally posted by chevy45412001
I beleave you mean exhaust flow? Weight savings is one advantage,but also some manufacturers claim better exhaust scavenging takes place with a 4-1 set up.

[Robert Haller]

When I took the baffle out of my Jardine 4-1 exhaust (K&N replacement filter, stock jetting), it became an open header with no backpressure to speak of. My bike ran worse and there was a decrease in low end power. Admittedly running wide open pipes should require a jetting increase, but I was curious to see what would happen. When I put the baffle back in it ran much better.