How to easily & inexpensively mod your bypass valves: Bypass valves are on some exhaust sytems and serve to regulate the sound level, keeping it mellow at low rpm's (when closed) and allowing them to scream at high rpm's (when open). Some owners disconnect their bypass valves rendering the exhaust loud all the time. Many of these same guys reattach their valves after they get tired of it being too loud. This got me thinking.....(not like a good Penthouse, but still ) The Capristo Twin system features unique adjustments on their bypass valves so that the valve can be partially open at low rpm's, thus allowing some raw exhaust noise to escape.....you just adjust these screws until the noise level is where you like it, setting the low-end noise level. So I figured....why can't we do the same to our valves???? So for $1.75 I did.....works great, check it out: Here is your typical bypass valve, this one is in the open position, no vacuum is applied to it. Image Unavailable, Please Login
Start by removing the clip...it just pulls out....then allowing the arm to slip off Image Unavailable, Please Login
Now here's the key ingredient...a simple lock-collar, 1/4" for 430, CS or 360 sport....and 3/16" for stock 360 Image Unavailable, Please Login
Simply slip the lock-collar onto the shaft...I left the allen-wrench attached for reference Image Unavailable, Please Login
By adjusting the position of the lock collar you can adjust how closed the valve can get...the higher up the shaft, the more the valve stays open. Total adjustment & control of your low-end setting! Image Unavailable, Please Login
You can also loosen the collar and let it drop to the bottom (or just to where the threads start)...easily allowing full travel and regular performace of the valve. Why did I do this? Because lots of guys told me the CS exhaust was too quiet at the bottom end and then some guys told me they detached their bypass valves but it was a bit too loud. This is a simply & easy solution. The lock collars can be bought at most hobby stores for about $2.
Can I do this without putting the car on a lift, how do I get access to the underside of the bypass valves ??
A 360 owner I ran into told me the easiest thing to do that worked for him was just to remove the vacuum hose, plug the hose with something like a tapered sheet metal screw, and then the valve would be open all the time. Correct?
OK understood - it's the ability to adjust the opening of the valve that is the value here. To the access question - one of the replies said that it the undreside of the valve can be accessed from the engine bay - does that mean access from above, or a need to remove an underbody tray (like the rear splitter) to access the bottom of the valve? Thanks.
Do you think keeping the valve partially open will eventually burn it out? For example, it's possible the butterfly might overheat if it doesn't have the heat sink from the valve body. Also, the constant movement of the butterfly with the hot exhaust gases could wear the mounting points.
Addressing this and other questions: Having the valves partially open should not affect the longevity of the valve nor burn it....it's just a "butterfly-style valve" fly where a round disc is rotated on a shaft to regulate the flow. Nothing to it, very crude & simple. Potential for damage: zero! The interesting thing about these bypass valves is that they require vacuum to operate/close; a lack of vacuum (having the vacuum lines removed/plugged OR disconnecting the electronic solenoid that regulates the vacuum line to the bypass valve) renders the valves permanently wide open. Note: this is why our exhaust system tend to be a bit louder when we first start them: the vacuum has to develop to then draw the bypass valves closed...thus quieting the exhaust system. When we first fire up the engine, the valves are sitting there open....they then close moments later. If you just disconnect the bypass valve/vacuum-line, then the valve is wide open all the time. On a stock 360 exhaust that's probably fine....but on the CS or 430 stock exhaust, this means the exhaust gases will NEVER see the inside of the muffler: the design of the CS/430 is such that when the bypass opens it actually allows the exhaust to flow straight from the cats right out the inner pipes/tips......I've met CS owners who say the CS is either too quiet at the low rpm's, they then disconnect the bypass and then complain it's too loud: this mod is all about regulating and being able to adjust your sound level. As it was explained to me, the Capristo Twin (basically the same as the CS or 430 exhaust) uses small adjustments to open their bypass valves a hair to allow some noise to escape at the bottom-end....too many customers were unhappy that it was too quiet. By adjusting the position of the lock collars you can choose the idle/low-rpm sound level to what you like. Without this flexibility you either had it too quiet or too loud. Why compromise when $1.75 can solve all this and identically replicate the adjustments the Capristo bypass valves have! The Challenge Stradale exhaust, 360 "sport" exahust, stock 430 exhaust and Capristo Twin are all systems that have the same design: a bypass valve that opens allowing a complete redirection of exhaust gases to come straight out the inner pipes/tips: no exhaust goes into the muffler. The stock 360 or 355 uses bypass valves in different places, these systems have their exhaust going straight into the muffler with no option to bypass the muffler itself. Once in the muffler the gases can escape from 4 different openings (2 inner pipes, 2 outter pipes)...the bypass valves in this configuration is on the larger of 2 pipes. In the closed position the exhaust can only run through the 2 smaller pipes. Once open, the exhaust can run through the smaller pipes AND the larger pipes. There ya go!
Pretty pleased with the results, start up is particularly fab, more agressive whenever you are on the throttle, without being too loud. I set mine just past halfway closed (remember down is fully open as the vacuum pump pulls them up to close them). I also tried with them fully open, you don't want this as at low revs it sounds like a tractor. Only tricky bit of putting the collars on was fitting the allen key into the collar to tighten it. I got round this by gluing the allen key into the collars before I put them on.
hmmm. I just double checked on my 03' Spyder and it doesn't have the bypass valves. Just a simple in n' out of the muffler.
You have the valves but cannot see them because the are below the black pannels/covers on the left and right side, easiest access is by removing the rear inner fender linners. valves are right there. (removing rear wheels helps) On 360CS or F430 valves can be accessed from rear of engine compartment, just open engine cover and look down.
