Bypass? - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Forced Induction All questions and problems regarding Superchargers, Turbos, NOS, ZEX, intercoolers, water injection, etc.

Reply
 
 
 
Thread Tools Search this Thread
Old 06-22-2004, 11:53 PM   #1
Senior Member
True Car Nut
Thread Starter
 
Join Date: Oct 2002
Location: Genoa, Illinois
Posts: 4,013
Thanks: 0
Thanked 0 Times in 0 Posts
Allmachtige is on a distinguished road
Default Bypass?

I need to be educated on the L67. I was advised to check the bypass valve because sometimes I noticed the boost needle changes slightly under load...but it may just be the SC building up boost. I dunno...I have only 1 week of experience with this engine so far.

So what am I checking for on the bypass valve, where is it located, and what is the process?
Allmachtige is offline   Reply With Quote
Old 06-24-2004, 12:57 AM   #2
Senior Member
Posts like a Turbo
 
Join Date: Jun 2004
Posts: 287
Thanks: 0
Thanked 0 Times in 0 Posts
caminated2k is on a distinguished road
Default

I don't mean to show my intake pic again but you can see the bypass in this shot:



On the top of the supercharger in this pic you will see a vacume line distro system with one that comes out and curves to the right with a white stripe on it and leads to a black canister, that is the boost bypass valve.

make sure the vacume lines that run to it are tight and not cracked. Also start the car and rev it in park and watch the little arm that comes out of the bottom of it, it should move DOWN when you rev. This means it is closing the valve in the blower to stop the recirculation of the boost pressure to the top of the blower. It keeps all boost in the lower intake manifold. If this arm moves UP at all meaning opening you can have a fluctuation in boost under WOT.

So again, check the vacume line system and make sure it'* all sealed up. If you need to you can losten the bolt on the blower that the boost bypass bracket attaches with and the bolt on the outside bracket and slide the canister in a down and left direction closing the gap for the arm to close to a shorter distance. This is known as the boost bypass valve 'trick'. You will see boost faster as the arm will close before it normally would allowing full boost pressure at less throttle %age.

If you have more questions or need images/step by step, let me know.
a
caminated2k is offline   Reply With Quote
Old 06-24-2004, 10:40 AM   #3
Senior Member
True Car Nut
 
Join Date: Jul 2003
Location: Westerville, Ohio 2000 Black SSEi
Posts: 6,127
Thanks: 0
Thanked 0 Times in 0 Posts
Rogue is on a distinguished road
Default

Disadvantages to this trick?
Rogue is offline   Reply With Quote
Old 06-24-2004, 11:20 AM   #4
Senior Member
Posts like a Turbo
 
Join Date: Jun 2004
Posts: 287
Thanks: 0
Thanked 0 Times in 0 Posts
caminated2k is on a distinguished road
Default

Disadvantage is fuel economy, as you hit boost faster at a lower throttle %age, it needs more fuel. I have yet to see any more problems with the trick than that. I tried it to see if perhaps my valve didn't close all the way causing a boost leak.. that wasn't the problem but now on the freeway in cruise control it will hit 7lbs of boost before it downshifts LOL.. gotta change that back
caminated2k is offline   Reply With Quote
Old 06-24-2004, 02:16 PM   #5
Senior Member
True Car Nut
 
Join Date: Jun 2002
Location: Bedroom, Ontario
Posts: 3,266
Thanks: 0
Thanked 0 Times in 0 Posts
Drifter420 is on a distinguished road
Default

must be my computer.. it'* rex'd
Drifter420 is offline   Reply With Quote
Old 06-24-2004, 09:43 PM   #6
Senior Member
True Car Nut
 
Join Date: Jun 2003
Location: Purgatory
Posts: 6,313
Thanks: 0
Thanked 0 Times in 0 Posts
PontiacDad is on a distinguished road
Default

Quote:
Originally Posted by Rogue
Disadvantages to this trick?
Pcm can also pull timing and set a ses code if pulling hard and you let off the throttle.
Its an ok trick for the track but does have the ability to harm the engine
PontiacDad is offline   Reply With Quote
Old 06-25-2004, 11:19 AM   #7
Member
Posts like a V-Tak
 
Join Date: May 2004
Location: NW Burbs/Chicago and St Pete,FL
Posts: 82
Thanks: 0
Thanked 0 Times in 0 Posts
artk is on a distinguished road
Default

I don't understand, my boost needle moves upward every time I accelerate.
What is the problem I'm missing?
artk is offline   Reply With Quote
Old 06-25-2004, 11:21 AM   #8
Junior Member
Posts like a Ricer Type-R
 
Join Date: Aug 2002
Posts: 10
Thanks: 0
Thanked 0 Times in 0 Posts
willwren is on a distinguished road
Default

You're running the stock pulley. I don't think you'll see the problem until you get into higher boost levels.
willwren is offline   Reply With Quote
Old 06-25-2004, 08:40 PM   #9
Senior Member
True Car Nut
Thread Starter
 
Join Date: Oct 2002
Location: Genoa, Illinois
Posts: 4,013
Thanks: 0
Thanked 0 Times in 0 Posts
Allmachtige is on a distinguished road
Default

Should be installing 3.4 pulley this weekend.
Allmachtige is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Vats Bypass 93 bonneville with pellet randy Audio (and aftermarket electronics) 2 08-27-2003 01:20 PM
VATS *Permanent* bypass mevans49083 1992-1999 7 08-13-2003 03:10 PM
Boost Solenoid Bypass 2000SilverBullet Forced Induction 39 07-03-2003 08:12 AM
Bypass automatic light contol pontiacfan1978 1992-1999 26 06-06-2003 12:29 PM
Re: Aux Tranny cooler, should I totally bypass the radiator? brminder 1992-1999 3 04-05-2003 07:29 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 03:16 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.