Engine won't hit full boost - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


2000-2005 Discuss your 2000-2005 Bonneville SE, SLE, and SSEi Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

Reply
 
 
 
Thread Tools Search this Thread
Old 08-06-2011, 11:42 PM   #1
Member
Posts like a V-Tak
Thread Starter
 
Join Date: Mar 2011
Location: St. Charles, MO
Posts: 53
Thanks: 0
Thanked 0 Times in 0 Posts
jedwards83 is on a distinguished road
Default Engine won't hit full boost

I've heard a stock L67 should hit 7.5 lb of boost. At what RPM (during WOT) does this typically occur?

Lately my car has been feeling slower than normal, and it runs ~4 PSI at WOT until it'* past about 5k RPM, but it still never gets to 7.5 psi, maybe 6.5 at best.

I remember at one time I could get the needle right at the base of the orange bar without too much effort. Any explanation for this?
jedwards83 is offline   Reply With Quote
Old 08-07-2011, 01:43 PM   #2
Senior Member
True Car Nut
 
raptor660's Avatar
 
Join Date: Mar 2010
Location: Eaton Rapids MI
Posts: 2,964
Thanks: 0
Thanked 0 Times in 0 Posts
raptor660 is on a distinguished road
Default

this is DANTHURS area.. not sure if he has been on here... try PMing him
raptor660 is offline   Reply With Quote
Old 08-07-2011, 01:47 PM   #3
Senior Member
True Car Nut
 
rjolly87's Avatar
 
Join Date: Jun 2003
Location: Las Cruces, NM
Posts: 6,857
Thanked 298 Times in 246 Posts
rjolly87 has a brilliant futurerjolly87 has a brilliant futurerjolly87 has a brilliant futurerjolly87 has a brilliant futurerjolly87 has a brilliant futurerjolly87 has a brilliant futurerjolly87 has a brilliant futurerjolly87 has a brilliant futurerjolly87 has a brilliant futurerjolly87 has a brilliant futurerjolly87 has a brilliant future
Default

You may want to check out the supercharger belt and tensioner, belt slip is one of the many things that could cause the issue you are describing. Does the supercharger sound like it always did?
rjolly87 is offline   Reply With Quote
Old 08-08-2011, 07:50 AM   #4
DINOSAURUS BOOSTUS

Expert Gearhead
 
BillBoost37's Avatar
 
Join Date: Mar 2005
Location: Enfield, CT
Posts: 41,391
Thanks: 0
Thanked 0 Times in 0 Posts
BillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of lightBillBoost37 is a glorious beacon of light
Default

air density and humidity can effect this greatly. You will also notice less boost if you are getting KR. Summertime is going to be slightly lower boost than winter as well. Again..density.
BillBoost37 is offline   Reply With Quote
Old 08-08-2011, 09:44 AM   #5
Member
Posts like a V-Tak
Thread Starter
 
Join Date: Mar 2011
Location: St. Charles, MO
Posts: 53
Thanks: 0
Thanked 0 Times in 0 Posts
jedwards83 is on a distinguished road
Default

That seems to be what it is. When I first noticed it, it was in the mid 90'* and humid, pretty typical in mid summer here.

When I got on it this morning (temps were back in the 70'*) it was right where it should be at WOT, and even jumped into the orange on the upshift. Didn't think temp/humidity would have that much an effect, but it does.

I've also noticed at higher elevations (took couple trips to Colorado this summer), it would only reach 5 psi on a good day, I'm guessing same thing. Car felt slower than molasses.
jedwards83 is offline   Reply With Quote
Old 08-08-2011, 10:48 AM   #6
Senior Member

True Car Nut
 
2kg4u's Avatar
 
Join Date: Sep 2006
Location: Windsor, Ontario / Detroit, Michigan
Posts: 4,804
Thanked 220 Times in 181 Posts
2kg4u has much to be proud of2kg4u has much to be proud of2kg4u has much to be proud of2kg4u has much to be proud of2kg4u has much to be proud of2kg4u has much to be proud of2kg4u has much to be proud of2kg4u has much to be proud of2kg4u has much to be proud of
Default

Check the boost control actuator and boost control solenoid. Make sure the arm that controls the betterfly valve is travelling to full extension. There are write ups on the forum you can search for, but let me know if you can't find them.
2kg4u is offline   Reply With Quote
Old 08-08-2011, 10:57 AM   #7
Senior Member

True Car Nut
 
2kg4u's Avatar
 
Join Date: Sep 2006
Location: Windsor, Ontario / Detroit, Michigan
Posts: 4,804
Thanked 220 Times in 181 Posts
2kg4u has much to be proud of2kg4u has much to be proud of2kg4u has much to be proud of2kg4u has much to be proud of2kg4u has much to be proud of2kg4u has much to be proud of2kg4u has much to be proud of2kg4u has much to be proud of2kg4u has much to be proud of
Default

When the car is not running, the arm on the boost control actuator will be fully extended. When you start the car, the arm "pulls up" into the actuator. Under WOT the arm will again extend (to the position it is in when the car is not running) to open the */C gate valve. In other words, when the arm is retracted into the actuator you have no boost. When the arm is extended out of the actuator you have full boost.

One test you might want to try is to remove and plug the vacuum lines gong in to and out of the actuator (this will mean the actuator will not move from the fully extended position it is in when the car is not running) and take the car for a drive. This will give you full boost at all times, regardless of throttle position. If you notice a difference in boost, your problem is a bad bcs or bca. Do not drive the car like this for more than a quick test, or the gods of engine damage will pay you a visit.
2kg4u is offline   Reply With Quote
Old 08-08-2011, 05:26 PM   #8
Member
Posts like a V-Tak
Thread Starter
 
Join Date: Mar 2011
Location: St. Charles, MO
Posts: 53
Thanks: 0
Thanked 0 Times in 0 Posts
jedwards83 is on a distinguished road
Default

Thanks for the tip! I will try this and report back if things don't appear to be working correctly.
jedwards83 is offline   Reply With Quote
Old 08-08-2011, 10:51 PM   #9
-- SITE DONATOR --
True Car Nut
 
ymmot04's Avatar
 
Join Date: May 2009
Posts: 4,638
Thanked 5 Times in 4 Posts
ymmot04 is a glorious beacon of lightymmot04 is a glorious beacon of lightymmot04 is a glorious beacon of lightymmot04 is a glorious beacon of lightymmot04 is a glorious beacon of lightymmot04 is a glorious beacon of light
Default


Also, if you notice that the little black foot isn't going all the way down when you give it a good rev, you may need to grease the rod that goes into the supercharger and turns the boost flappamajiggy.

I hit mine from the outside with some PB Blaster and let it sit for an hour, then hit it again and wiggled it around a bit. It loosened right up and has been fine ever since.
Attached Thumbnails
Engine won't hit full boost-bcabcs.jpg  
ymmot04 is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
trying to get full boost 2kg4u Forced Induction 10 09-08-2009 08:16 PM
Boost Control Solenoid Maintenance and Boost Control Actuator Test for low Boost* Toddster Trouble shooting + Test Procedures 0 03-21-2009 07:24 PM
Supercharger gauge not showing full boost. chuck03 Forced Induction 26 10-16-2006 05:13 PM
Full boost? F14CRAZY Forced Induction 3 06-22-2006 12:15 AM
to hit, or not to hit ga93sle General GM Chat 17 03-29-2006 09:28 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 10:04 AM.


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.