recently i have seen the by pass valve mentioned more and more, i saw a few sites that sold a modified one. what the heck is it? im not even sure if i have one? 2003 S. would you guys recommend one and what does it do for performance?
also i should probably post a new thread but.....i have a few questions about the oil catch can too. whats the purpose? obviously to catch oil entering the engine due to the supercharger, but why put one on? just to clear up smoke issues in the morning?
thanks alot guys :impatient

 

The bypass valve is there so that the SC almost free spins when not on boost. This increases gas mileage. It's controlled by vacuum, from in front of the SC in stock configuration. From the factory, lots of BPVs have less than ideal setting of the set screw that controls how closed it gets, and so some leak more boost than others. This is an easy fix if you bother to take the valve off yourself to check and adjust. The other mod to the valve is to use a shorter stiffer spring in the diaphram, and this means that it takes more vacuum to start opening, and also it seems to not open as far. Net result is that it closes earlier when you start to floor it, but the trade off is a bit of a jeckyl/hyde personality. Personally, I Didn't like it cause it made real light throttle modulation a bit of a pain. Other feel differently. Another mod to the BPV is where you get the vacuum from, with some using a post SC manifold tap to get the signal. Some like it, some don't. Search on "Vacuum Gain System" for more details on that one.

For completeness, I did the VGS, reset my own stop, and stretched the stock spring a bit. I'm happy... To each thier own.

Matt

 

The BPV opens and blows off the boost when the throttle is shut. It shuts and sends the boost to the intake when the throttle is opened. I had the Detroit Tuned BPV installed and it created a jerky on/off response that I did not like so I had it taken out. Like Dr. O. says some stock BPVs don't close all the way so you loose boost.

 

Dr. O, I'd like to make the BPV adjustment stop mod, and would like to know more about the spring adjustment you made too. Please could you outline details or refer me to where I could find a how to. Apreciate you help.
Regards, Lee (WLSH BST)

 

you guys are great. so knowledgeable. i think ill keep my system the way it is, no BPV for me. hey you guys wouldnt happen to know anything about a lightened crank pulley by Alta? i have heard it can destroy your engine so as to date i havent installed one but i am interested. ive heard good and bad. any thoughts?
2003 Cooper S Alta CAI, 15%Alta pulley, Cooper S guage set ( boost and alt ) 25% tint, Alat short antenna,16"x-lite rims on dunlop SP Sport Maxx 205/50/16. pure silver with black viperstripes. MORE MODS SOON

 

ah yes conan the barbarian

 

do a search for Ryephile's "yo yo chronicles" and get comfortable.

I started getting the Yo Yo on my 2002 MCS after 105K and replaced the stk BPV with the Detroit tuned model and it took care of the erratic throttle and seems to be costing me 3 MPG . I don't think I'll swap it out however.

 

and it has all the details. So if you're really serious you need to earn you wings by reading all the 20+ pages! It's also a good history lesson on some of the developmenets of the earlier mods.... FWIW, the DTBPV was known as "Ryephix-II" or something like that. Ryephile came up with it, and the evolution of the name is another story indeed!

Matt

 

I hate to say this since I have been a newbee myself when it came to these questions and concerns but after having gone through so many threads and discussoin, pages and pages and months of analysis, opinions, you would only have to direct the next person coming in asking those same old question back to those threads and have him/her go through all of those pages, threads and figure it out.

I know I did read every single post and thread that was discussed about questions I had. I then read some more and when still in question, I asked few people that I had come to learn they were the professionals and knew what they were talking about.

So, I guess the best thing to do is go through the forum, spend lots of time reading, and then read some more do some search and see if that answers your questions. If all fails then read more and look/search more.