Maggie Boost
Thread Starter
Heel & Toe
Joined: Jan 2007
Posts: 24
Likes: 0
From: San Mateo, CA CA
Maggie Boost Missing
No boost while flooring it in 1st gear. Just had gauges installed for my Maggie & noticed in 1st gear from a stop there was no boost when I took off hard from the stoplight. Got up to 4500rpms & shifted to 2nd & still didn't see any boost. After shifting into 3rd I let off the gas & then from a roll stomped the gas finally saw the boost gauge rise to about 4-5. Is this normal? I thought there was some boost almost instantly esp after 2500 rpms? I do know from a roll I gassed it on the freeway & I not only heard the Maggie whining but the gauge did go to 6. It sure pulls hard from a roll, just not from a standstill. Is something wrong?
Last edited by 67silverandblack; Dec 31, 2008 at 10:54 PM.
Racer
Joined: Aug 2008
Posts: 367
Likes: 0
From: Sacramento ca
I've got a maggie and it seems every time I get on it pretty good the boost gauge goes pretty quick. Going from a stop if I drive it "light" or not give it much gas I do not see the vacuum increase. Are you seeing no boost when you do get on it?
Thread Starter
Heel & Toe
Joined: Jan 2007
Posts: 24
Likes: 0
From: San Mateo, CA CA
So you get boost if you are driving normal, say from a stop sign in first & second?
Racer
Joined: Aug 2008
Posts: 367
Likes: 0
From: Sacramento ca
well I get boost pretty much whenever I give it gas. If I drive really light I get no boost but I am new to F/I and I am sure some others can give you a better knowledge of what happens (or more importantly what should happen) with a maggie set up. I do get plenty of boost whenever I give it plenty of gas I guess you could say (regardless of speed / gear)
Thread Starter
Heel & Toe
Joined: Jan 2007
Posts: 24
Likes: 0
From: San Mateo, CA CA
New to FI with the Corvette, but I did have a Ford Lightning & since it was supercharged, I guess I am comparing the two. If I recall there was boost almost at all times. Even taking off from a stop & part throttle.
Maybe since the Lightning was an Auto thats why the boost?
Maybe I should have my Vette checked out.
Maybe since the Lightning was an Auto thats why the boost?
Maybe I should have my Vette checked out.
Drifting
Joined: Jan 2004
Posts: 1,255
Likes: 4
From: Holliston MA
Just had gauges installed for my Maggie & noticed in 1st gear from a stop there was no boost when I took off from the stoplight. Got up to 4500rpms & shifted to 2nd & still didn't see any boost. After shifting into 3rd I let off the gas & then from a roll stomped the gas finally saw the boost gauge rise to about 4-5. Is this normal? I thought there was some boost almost instantly esp after 2500 rpms? I do know from a roll I gassed it on the freeway & I not only heard the Maggie whining but the gauge did go to 6. It sure pulls hard from a roll, just not from a standstill. Is something wrong?
How hard are you getting on it? When I do "normal" driving, I dont get into boost. But once I put the pedal to the floor, the boost kicks in imediatly.
Drifting
Joined: Dec 1999
Posts: 1,541
Likes: 2
From: Raleigh NC
Make sure your by-pass arm is not catching on something. When I installed mine the arm was hitting the the brake booster hose. I was seeing minimal boost. Once fixed, boost was instantly up to 5 psi in any gear.
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Melting Slicks
Joined: Sep 2004
Posts: 3,178
Likes: 13
From: N. County/San Diego
Assuming you`ve ruled out a gauge problem, your boost gauge should show decreasing vacuum then increase into boost from tip-in of the throttle, your`s does not sound like it`s functioning properly.
BTW, if you`re not sure where the by-pass is, it`s the black cylinder shaped valve (vacuum lines connect & an arm comes out the top) on the driver side by the blower snout.
Thread Starter
Heel & Toe
Joined: Jan 2007
Posts: 24
Likes: 0
From: San Mateo, CA CA
Just checked out the by pass arm. It is not sticking & moved free of the hoses.
Should I replace the by pass valve?
From a roll I get boost in every gear. I just don't get boost when I mash the peddle from a dead stop. No wonder why around town in the rain I had no traction issues in 1st & 2nd gear. People were warning me about this & it is yet to happen.
Should I replace the by pass valve?
From a roll I get boost in every gear. I just don't get boost when I mash the peddle from a dead stop. No wonder why around town in the rain I had no traction issues in 1st & 2nd gear. People were warning me about this & it is yet to happen.
Last edited by 67silverandblack; Dec 31, 2008 at 08:52 PM.
Melting Slicks
Joined: Sep 2004
Posts: 3,178
Likes: 13
From: N. County/San Diego
I will take a look at the by pass valve. I guess the thing that is bugging me is I get boost in all gears from a roll. It is from a dead stop & I mash the peddle hard that I am not seeing boost. Hopefully it is something minor like he valve. Besides another gauge how would I check that out/
Unless the diaphragm is cracked or torn don`t expect to see the problem with the by-pass valve, it can still be faulty without obvious visual signs...
One option on the gauge is to find a shop who has a hand gauge and hook it up at the t-fitting at the back of the manifold and position it on the cowl while revving her up.
Also.....re-check all of the couplers/clamps to make sure everything is tight and there are no air leaks....
Thread Starter
Heel & Toe
Joined: Jan 2007
Posts: 24
Likes: 0
From: San Mateo, CA CA
This is sounding like a by-pass valve......
Unless the diaphragm is cracked or torn don`t expect to see the problem with the by-pass valve, it can still be faulty without obvious visual signs...
One option on the gauge is to find a shop who has a hand gauge and hook it up at the t-fitting at the back of the manifold and position it on the cowl while revving her up.
Also.....re-check all of the couplers/clamps to make sure everything is tight and there are no air leaks....
Unless the diaphragm is cracked or torn don`t expect to see the problem with the by-pass valve, it can still be faulty without obvious visual signs...
One option on the gauge is to find a shop who has a hand gauge and hook it up at the t-fitting at the back of the manifold and position it on the cowl while revving her up.
Also.....re-check all of the couplers/clamps to make sure everything is tight and there are no air leaks....
Thread Starter
Heel & Toe
Joined: Jan 2007
Posts: 24
Likes: 0
From: San Mateo, CA CA
I will have to check the routing of the belt, but I had a mechanic buddy help me install the belt. It seemed correct by the Lingenfelter booklet. Is there a way to tell if the belt is slipping?
Pro
Joined: Aug 2004
Posts: 651
Likes: 1
From: Janesville WI
You will see belt residue (like belt dust) if there is slipping. Are you spinning the tires in 1st when hitting the throttle? If so, the engine may not be working hard enough to boost. You will only get boost if there is significant load on the engine, thats why it will boost easier/quicker when in a higher gear. Either way, you should be seeing the boost needle move in the vacuum zone when throttling in 1st. Believe it or not, I wish I had your problem. I have trouble getting traction in 1st with anything over 1/2 throttle. I wish it would not boost at all in 1st.
Drifting
Joined: Oct 2003
Posts: 1,923
Likes: 5
From: San Antonio TX
Just got back into the garage after a quick spin & I was in 2nd gear & then I gave it about 40-50% throttle. Instant boost. Didn't break the tires loose though. I believe it went to 4# maybe 5#
I will have to check the routing of the belt, but I had a mechanic buddy help me install the belt. It seemed correct by the Lingenfelter booklet. Is there a way to tell if the belt is slipping?
I will have to check the routing of the belt, but I had a mechanic buddy help me install the belt. It seemed correct by the Lingenfelter booklet. Is there a way to tell if the belt is slipping?
your bypass is acting up, you should see boost by 2000 rpm and 100% throttle. you should see 7 #s of boost on stock maggie setup by 3500 rpm.
More Than Zero
Thread Starter
Heel & Toe
Joined: Jan 2007
Posts: 24
Likes: 0
From: San Mateo, CA CA
You will see belt residue (like belt dust) if there is slipping. Are you spinning the tires in 1st when hitting the throttle? If so, the engine may not be working hard enough to boost. You will only get boost if there is significant load on the engine, thats why it will boost easier/quicker when in a higher gear. Either way, you should be seeing the boost needle move in the vacuum zone when throttling in 1st. Believe it or not, I wish I had your problem. I have trouble getting traction in 1st with anything over 1/2 throttle. I wish it would not boost at all in 1st.
the belt load goes up with boost and air flow, so belt slip at 0 boost and low rpm (air flow) does not happen with out a lot of slip at high RPM + boost.
your bypass is acting up, you should see boost by 2000 rpm and 100% throttle. you should see 7 #s of boost on stock maggie setup by 3500 rpm.
More Than Zero
your bypass is acting up, you should see boost by 2000 rpm and 100% throttle. you should see 7 #s of boost on stock maggie setup by 3500 rpm.
More Than Zero
Burning Brakes
Joined: Aug 2003
Posts: 1,070
Likes: 9
From: MARRIOTTSVILLE MD
I don't know how you can avoid adjusting the rear belt they don't stay tight forever. A brand new rear belt will need to be adjusted several times before it settles down.
inthered