Torque screw mod for fully debaffled pipes

[diamond_jim]

Anyway you can make something like this and experiment?

[ertyqway]

I'm not so much of a fabrication guy, but more of a designer. I could easily draw it up and model it in CAD, but building it? I haven't got any of the right tools.

I'll sketch something and post it.

[mxedit]

Originally Posted by nicocorea

Would someone kindly explain how exhaust mods can affect the mixture entering the cylinders???

Exactly, all this exhaust mod stuff happens downstream of the fuel mixture in the cylinders, so what we're really talking about is the alteration in how the exhaust works, back pressure, etc. You don't start modifying settings for lean/rich mixture until you change something about your intake.

[johnnyvl800]

How you mount the cones that were mentioned. My quads exhaust had different size cones that affected the ranges considerably.

[xtenzzive]

If you lose your back pressure in the exhaust, you will gain top end HP as the exhaust is expelling more volume of gasses, but there is a limit to top end based on fuel delivery, timing, and airflow to cylinder. If you increase backpressure you will gain noticeable low end torque, but lose your higher end exhaust scavanging. There is only a happy medium you can play with. You get one or the other, till you change the whole game up(fuel processor, cam, timing adjustment) and most of those will do the same effect. BTW has anyone found custom cam's for our motor? I could sure do with a little more lobe separation and duration. I would just retard the timing if I knew how......soon...

[diamond_jim]

I tried this mod after I made the new airbox but before I installed an Fi2000. I was playing with both the intake (using restirctor plates) and the exhaust to see what I could do with the bike with new intake and open exhaust but no fuel processor. So I was trying the restrictor plate and adding some exhaust back pressure to insure I wasn't running lean and to simply experiment and see what happened.

But now I have a Fi2000 and all is great.

[07M50zAllDaWay]

Originally Posted by nicocorea

Would someone kindly explain how exhaust mods can affect the mixture entering the cylinders???

I'm an HVAC tech by trade, but I think I can apply some of those theories to your question. If I'm wrong about anything here, feel free to point it out. Here goes:

The air intake is a fixed orfice, engineered to work with the stock exhaust and it's calculated static resistance. By modifying the exhaust, you are reducing the static resistance(back pressure). Hence more air is able to enter the mixture, as more is allowed to be exhausted.

Seems like it would be the same as an air-handler. Design and install it for X cfm. Size the supply and return ducts accordingly. Set the fan to the proper RPM, and you have your "stock" system. Now rip out the return duct and increase it in size by 50%. You have reduced the static resistance on the back side of the fan. You will see an increase in CFM(air movement), even though you have done nothing to increase the fan RPM or touched anything on the supply side of the system.

Saying all this, I still debaffled my pipes and have not noticed a change in performance...lol Perhaps the computer is able to self adjust for slight mods like this?

[xtenzzive]

Exhaust is expelled by the piston pushing the air from the combution chamber while the exhaust valve is open and the intake vavle is closed. If the resistance is reduced on exhaust stroke then it will free up the exhaust stroke and increase the inertia from the spent compression stoke. This wouldn't have any effect on the intake volume pulled into the combustion chamber, nor the amount of air pulled in. This type of mod usually losses Torque, and gains top end hp. If the orginal exhaust was too restrictive, then residual exhaust gases may be left in the combustion chamber dirtying the fuel mixture with spent gases that are less volitle. The only way to get a bigger combustion is to force more air into the combustion chamber (supercharger, longer duration cam, higher lift cam) or in our case the air filter setup is really restrictive so upgrading that will improve HP/tq allot, but when you do this you will get more air than fuel and the CPU on our bikes doesn't adjust adquately causing the fuel mixture to run too lean, so to fix this you need to increase fuel flow to the mix, thus you have added more air and more fuel which will increase hp/tq and with the debaffle you have solved the other problem you would've had which would be no way to get all that extra flow out.

[xtenzzive]

What I meant to say is that exhaust mods could never pull more air into the combustion camber. Exhaust stroke and intake stroke are separated on most stock motors. Now you through a large duration cam into the mix and we are talking a different game since the valve strokes overlap. But not on a stock bike.

[07M50zAllDaWay]

Originally Posted by xtenzzive

Exhaust is expelled by the piston pushing the air from the combution chamber while the exhaust valve is open and the intake vavle is closed. If the resistance is reduced on exhaust stroke then it will free up the exhaust stroke and increase the inertia from the spent compression stoke. This wouldn't have any effect on the intake volume pulled into the combustion chamber, nor the amount of air pulled in. This type of mod usually losses Torque, and gains top end hp. If the orginal exhaust was too restrictive, then residual exhaust gases may be left in the combustion chamber dirtying the fuel mixture with spent gases that are less volitle. The only way to get a bigger combustion is to force more air into the combustion chamber (supercharger, longer duration cam, higher lift cam) or in our case the air filter setup is really restrictive so upgrading that will improve HP/tq allot, but when you do this you will get more air than fuel and the CPU on our bikes doesn't adjust adquately causing the fuel mixture to run too lean, so to fix this you need to increase fuel flow to the mix, thus you have added more air and more fuel which will increase hp/tq and with the debaffle you have solved the other problem you would've had which would be no way to get all that extra flow out.

Excellent point, one I clearly missed in my previous post. While it's certainly true that removing baffles or other exhaust changes decrease the resistance the pipe offers, the engine shouldn't see an increase in combustion air due to the intake valves being closed on the pistons upstroke. I'll grab my gauges and freon and quietly go back to my own field of expertise....

[07M50Limited]

Originally Posted by xtenzzive

What I meant to say is that exhaust mods could never pull more air into the combustion camber. Exhaust stroke and intake stroke are separated on most stock motors. Now you through a large duration cam into the mix and we are talking a different game since the valve strokes overlap. But not on a stock bike.

Thats right, no exhaust mod, can ever pull more intake air in, exhaust mods, are for getting the air out when you do a intake mod, and to equalize the flow, and if you do to much exhaust mods, without the intake, you suffer,from back pressure loss, and lose performance