2.0 LSJ Engine: How to: Boost Bypass Mod
01-29-2006, 05:33 PM
#1
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How to: Boost Bypass Mod
So with new people constantly asking what this is and how to do it, here it is, since its not already posted... 
And I know many people think that plugging diff. holes is the right one, well with experince, and testing on multiple LSJ's, this is the correct one that has always worked for me.
Boost Bypass Mod.
For the Cobalt SS stock boost is 12.5lbs. For example I will use a 3" Pulley.
You should see 15lbs over the stock 12.5lbs with the 3" Supercharger pulley.
Only problem is the stock boost bypass bleeds boost from 6k RPMS's up until redline.
This means that you will build boost faster with the smaller pulley, but as soon as you hit 6K rpms's the PCM bleeds boost and throws it back down to 12.5lbs(stock)
So to see that 15lbs of boost all the way to redline you will have to do the boost bypass mod, here are the instructions:
My finger is pointing to the line you need to disconnect.
Now remove the line...
..and plug it with a screw...make sure the screw is in there tight, you dont want it to shoot out LOL (happened before)
there you go, leave it disconnected, and you may want to buy a small filter for the exposed solenoid (i think thats what its called)
Some people run this mod only when racing, which is probably the better idea IMO, after all it is an engine protection feature if you think about it...
anything else? Feel free to add!!
And I know many people think that plugging diff. holes is the right one, well with experince, and testing on multiple LSJ's, this is the correct one that has always worked for me.
Boost Bypass Mod.
For the Cobalt SS stock boost is 12.5lbs. For example I will use a 3" Pulley.
You should see 15lbs over the stock 12.5lbs with the 3" Supercharger pulley.
Only problem is the stock boost bypass bleeds boost from 6k RPMS's up until redline.
This means that you will build boost faster with the smaller pulley, but as soon as you hit 6K rpms's the PCM bleeds boost and throws it back down to 12.5lbs(stock)
So to see that 15lbs of boost all the way to redline you will have to do the boost bypass mod, here are the instructions:
My finger is pointing to the line you need to disconnect.
Now remove the line...
..and plug it with a screw...make sure the screw is in there tight, you dont want it to shoot out LOL (happened before)
there you go, leave it disconnected, and you may want to buy a small filter for the exposed solenoid (i think thats what its called)
Some people run this mod only when racing, which is probably the better idea IMO, after all it is an engine protection feature if you think about it...
anything else? Feel free to add!!
01-29-2006, 05:44 PM
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Thanks guys
feel free to add any comments, or experiences in doing this mod
i dont actually run this mod, i see 15lbs, then it drops around 6k, and im happy with that, like I said, its there to protect my car
feel free to add any comments, or experiences in doing this mod
i dont actually run this mod, i see 15lbs, then it drops around 6k, and im happy with that, like I said, its there to protect my car
01-29-2006, 05:46 PM
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Hey silver, when you dynoed your car, was that with this mod or did you leave it plugged in? Because if you dynoed without this, i'd expect a bit more power than 227 which would be sweet.
01-29-2006, 05:49 PM
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boost bypass was enabled, so with the mod..yes I would have dynoed more.
When i was dynoing i totally forgot, or I wouldve done one run with the boost bypass mod.
When i was dynoing i totally forgot, or I wouldve done one run with the boost bypass mod.
01-29-2006, 06:24 PM
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DONT DO IT STOCK! you will be slower! i did it and from a 40 roll my brother will pull 5 cars lol but formt he line he would get owned less boost in the start i think or its laggy so i can get off the line faster then it builds up!
i re plugged it in on the side of road revvd it up a few times took her out running neck and neck with him again!
this should on be done with another size pulley
i re plugged it in on the side of road revvd it up a few times took her out running neck and neck with him again!
this should on be done with another size pulley
03-10-2006, 11:41 PM
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what would it do if you plug the front hose instead of the back one because that is what i did and i got my ass handed to me by a stock ss/sc i tried puting it back on and we were even by the way i have a 3in pulley i dident get to run him with the back one pluged off any info would be nice
04-01-2006, 10:35 PM
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I made a valve assembly with low pressure fitting and installed it line so that all that you have to do is turn the valve off at the track and on for the street. I was considering running a hose through the firewall so that I could use it at red lights but that is illegal.
...
...
Last edited by Mwilson; 04-02-2006 at 09:56 PM.
04-01-2006, 10:58 PM
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I did what Mwilson did, bought the valve used from clevelander2002, and everything is operating as stock until I shut it off. It is very easily hidden and can be changed back to stock very easily.
04-22-2006, 05:19 PM
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Well guys.
I did this today with my stock SS/SC (05), and apparently it makes somewhat of a difference. I seem to be getting better low-end/launching traction and better operation in first gear. I don't know why that is..
On the other hand, I noticed that before the bypass, running around 6000 RPM seemed to be a pointless venture. After the bypass I feel as though I'm able to gain power for a longer RPM range. Is it supposed to be that way? Pretty weird, but it doesn't seem to be hurting anything, and actually I was able to stay neck and neck with TxL's SS/SC (Injen intake / Corsa Touring Exhaust) and did absolutely fine. Last week we tried this, and he was slugging me....
I did this today with my stock SS/SC (05), and apparently it makes somewhat of a difference. I seem to be getting better low-end/launching traction and better operation in first gear. I don't know why that is..
On the other hand, I noticed that before the bypass, running around 6000 RPM seemed to be a pointless venture. After the bypass I feel as though I'm able to gain power for a longer RPM range. Is it supposed to be that way? Pretty weird, but it doesn't seem to be hurting anything, and actually I was able to stay neck and neck with TxL's SS/SC (Injen intake / Corsa Touring Exhaust) and did absolutely fine. Last week we tried this, and he was slugging me....
07-11-2006, 03:35 PM
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Wacky Number
I have a 3" South Florida Pulley on my 06 Cobalt and it's displaying 15 lbs of boost after 6000 rpm in 2nd and higher, but it won't read anything above 10 lbs of boost in 1st. And even when it reads 10 lbs, it's really jittery. Anyone have a clue as to whether this mod will cure that? I think it's because my stock tires can't hold the horsepower the car is putting out and I'm getting too much wheel hop until 2nd. But don't quote me on that, after all, I'm not a 3rd grade math teacher.
10-24-2006, 01:05 AM
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well, since chevy decided to make a s/c cobalt and make the same motor for the ion this is the only place i can seem to find any info on this mod. I actually have a 2006 civic si with a comptech S/C at 4.5 psi. it runs about 6psi and is suppose to drop at about 6k rpms back to 4.5.. well i see the actuator, but u guys have a solenoid... i dont see jack on mine. basically there is one damn vaccum line from the actuator to a housing on the SC and thats is. so im guessin i just pull it off then and thats it? i mean i can plug the part going to the actuator. ONE PROBLEM~ this goes foreveryone. dont leave that damn solenoid open like that. run another tube and get some type of filter because any type of unclean air can really mess things up.
that being said... should i jsut unplug that one hose, put a cap on the actuator and leave the tube ? whats my case? also, since the actuator doesnt work after that, that means the bypass is shut at all times correct? or its open? because vaccum closes it, so no vaccum stays open? or no vaccum just closes? that means there is constant air going through the S/C. gas miles are messed with because its not running from the plenum anymore, its going straight through so basically u have taken a eaton roots type S/C that ran at like .5 psi around town to everytime u touch the gas u start to run in more boost.. anyway, i guess i might go in the garage real fast and see what i can do....
that being said... should i jsut unplug that one hose, put a cap on the actuator and leave the tube ? whats my case? also, since the actuator doesnt work after that, that means the bypass is shut at all times correct? or its open? because vaccum closes it, so no vaccum stays open? or no vaccum just closes? that means there is constant air going through the S/C. gas miles are messed with because its not running from the plenum anymore, its going straight through so basically u have taken a eaton roots type S/C that ran at like .5 psi around town to everytime u touch the gas u start to run in more boost.. anyway, i guess i might go in the garage real fast and see what i can do....
10-24-2006, 02:18 AM
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ok, so i did this. i unplugged it but there is no need to plug off the tube to the actuator because there is no vaccum to it at all once that hose is off. well atleast on mine. i notice there is 2 hoses on urs. BUT i think the midrange got a little crazy in 1st gear. if u unplug it while the car is running, u can actually watch the valve close. BUT ur fuel economy is jacked because now there is no bypass u are constantly boosting. so not a good idea to leave it off. on the other hand i do belive my mid was good, but thats only 1st gear in my car because i dont redline till 8k take it to 8400 and i land right at about 6200 when i shift or higher. so basically, i cant tell if it bleeds off, or stays shut when im shifting from second on. i cant really tell? but down low, its there.
ofcourse mine is a pain in the ass to reach. its undet the S/C and there is no room to move ur hands so it took DAYS to hook back on. so i had to get another hose and put a valve thats all i had so i stuck it between them. ****! anyway, i need a boost guage i guess.....
ofcourse mine is a pain in the ass to reach. its undet the S/C and there is no room to move ur hands so it took DAYS to hook back on. so i had to get another hose and put a valve thats all i had so i stuck it between them. ****! anyway, i need a boost guage i guess.....