Boost Problems.
Thread Starter
Racer
Joined: Jul 2004
Posts: 315
Likes: 15
From: Ornskoldsvik
Boost Problems.
Hello.
Firt of all. I´m from Sweden so you´ll have to excuse my spelling.
I have recently started my -85 TPI c4 with P600B sc, and i have some questions. The car starts up and runs fine but when i´m driving and give it full throttle it runs real bad. The Boost gauge shows no overboost. I have about -20-25psi vacum but it stops at 0!!. What is the problem? Is the belt slipping? Even when i´m standing still and rev the engine up to about 4-5000r/pm there is no boost. I can´t find any leakage at all. The car runs bader now than it did whitout the sc installed.
I have installed the msd 6al inside the cupé ( passanger side ) if it does any difference?
Following parts are installed.
383 eagle stroke fully balaced and arp-bolted.
ported and modifed heads 76cc
comp cams full rocker roller package and comp cams blower cam.
msd 6al with 3-step module.
ported intake.
lucas 38# injectors.
Aeromotive A1000 fuel pump.
8,7:1 cr.
Procharger P600B sc
Front mounted intercooler.
Turbo xs bov.
Manual transmission.
etc.
greatful for some useful information.
/Svante.
Firt of all. I´m from Sweden so you´ll have to excuse my spelling.
I have recently started my -85 TPI c4 with P600B sc, and i have some questions. The car starts up and runs fine but when i´m driving and give it full throttle it runs real bad. The Boost gauge shows no overboost. I have about -20-25psi vacum but it stops at 0!!. What is the problem? Is the belt slipping? Even when i´m standing still and rev the engine up to about 4-5000r/pm there is no boost. I can´t find any leakage at all. The car runs bader now than it did whitout the sc installed.
I have installed the msd 6al inside the cupé ( passanger side ) if it does any difference?
Following parts are installed.
383 eagle stroke fully balaced and arp-bolted.
ported and modifed heads 76cc
comp cams full rocker roller package and comp cams blower cam.
msd 6al with 3-step module.
ported intake.
lucas 38# injectors.
Aeromotive A1000 fuel pump.
8,7:1 cr.
Procharger P600B sc
Front mounted intercooler.
Turbo xs bov.
Manual transmission.
etc.
greatful for some useful information.
/Svante.
Advanced
Joined: Apr 2004
Posts: 74
Likes: 0
From: Miami Florida
I don't know if this is your case but my friend had a similar problem on his Z06 and it was the belt slipping. ATI helped him staighten out the problem but it took thicker pulleys and belt to get it to work.
Race Director
Joined: Feb 2002
Posts: 11,268
Likes: 14
From: Honolulu, HI
Originally Posted by Svante
Even when i´m standing still and rev the engine up to about 4-5000r/pm there is no boost.
Are you actually driving this car or just sitting still and reving it?
Last edited by vvv90; Jul 20, 2004 at 11:25 AM.
Drifting
Joined: Aug 2002
Posts: 1,475
Likes: 0
From: Speedo Indiana
Originally Posted by vvv90
You won't EVER see boost by sitting and reving the car. The surge valve closes under vacuum. aka driving under load.
Are you actually driving this car or just sitting still and reving it? :skep
Are you actually driving this car or just sitting still and reving it? :skep
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Thread Starter
Racer
Joined: Jul 2004
Posts: 315
Likes: 15
From: Ornskoldsvik
Yes i am driving the car when i´m checking the boost gauge. 
More testing today. I have moved the hose from the boost gauge to the throttle body, where the hose to the "how do you say? Valvelid? originaly is inserted."
Dunno if this is a good place to mount it but it shows about 2-3psi when i´m at 2-2500r/pm with ~5% of the throttle open. But when i give it full throttle i loose all the pressure. The same if i´m reving the engine.
I´ve also installed a new belt, an extra belt tensioner and i also have used belt spray to give it more traction. The belt is very stretch now and i can hardly twist it. I´m beginning to wonder if the Sc is broken.
The a/f meter shows one dot into the rich area.
Btw. What do you mean with the surge valve? Where is that located? Don´t understand all the words =)
More testing today. I have moved the hose from the boost gauge to the throttle body, where the hose to the "how do you say? Valvelid? originaly is inserted."
Dunno if this is a good place to mount it but it shows about 2-3psi when i´m at 2-2500r/pm with ~5% of the throttle open. But when i give it full throttle i loose all the pressure. The same if i´m reving the engine.
I´ve also installed a new belt, an extra belt tensioner and i also have used belt spray to give it more traction. The belt is very stretch now and i can hardly twist it. I´m beginning to wonder if the Sc is broken.
The a/f meter shows one dot into the rich area.
Btw. What do you mean with the surge valve? Where is that located? Don´t understand all the words =)
Last edited by Svante; Jul 20, 2004 at 05:33 PM. Reason: misspell
Pro
Joined: Dec 2002
Posts: 704
Likes: 16
From: Dallas Texas
Originally Posted by Ice-Vette
What are the pulleys sizes ?
Or pulley ratio.
I have ratio of 2.235 with 383 and 12psi of boost.
Or pulley ratio.
I have ratio of 2.235 with 383 and 12psi of boost.
Thread Starter
Racer
Joined: Jul 2004
Posts: 315
Likes: 15
From: Ornskoldsvik
I have the standard pulley on the crank, dunno the size there without looking it up. The pulley on the sc i about5-6cm/dia. I will look it up for you tonight when i´m in the garage.
blower inlet side restriction? You mean the air filter? I´m using Bmc twin kone airfilter.
But i dont understand why the boost drops when i´m giving it full throttle. The Bov blows when i´m closing the throttle. But it doesn´t make any bigger noise.
Can it be anything mecanical problem with the engine that is causing the problems? The engine sounds good and doesn´t make any bad noises..
/Svante.
blower inlet side restriction? You mean the air filter? I´m using Bmc twin kone airfilter.
But i dont understand why the boost drops when i´m giving it full throttle. The Bov blows when i´m closing the throttle. But it doesn´t make any bigger noise.
Can it be anything mecanical problem with the engine that is causing the problems? The engine sounds good and doesn´t make any bad noises..
/Svante.
Pro
Joined: Dec 2002
Posts: 704
Likes: 16
From: Dallas Texas
I had a 90 degree rubber elbow that would collapse above ~4500 rpm and would cause to the car to fall on its face...like it was dying.
On my LTx based engine, my car would fall apart when I would go into boost and then it would run bad for several days...turned out to be a bad check valve to the optispark. Under boost it was blowing intake charge into distributor. I capped the opti and haven't had a problem since.
On my LTx based engine, my car would fall apart when I would go into boost and then it would run bad for several days...turned out to be a bad check valve to the optispark. Under boost it was blowing intake charge into distributor. I capped the opti and haven't had a problem since.
Instructor
Joined: Sep 2000
Posts: 125
Likes: 0
From: Orange Park, Fla
Originally Posted by Svante
Yes i am driving the car when i´m checking the boost gauge.
More testing today. I have moved the hose from the boost gauge to the throttle body, where the hose to the "how do you say? Valvelid? originaly is inserted."
Dunno if this is a good place to mount it but it shows about 2-3psi when i´m at 2-2500r/pm with ~5% of the throttle open. But when i give it full throttle i loose all the pressure. The same if i´m reving the engine.
More testing today. I have moved the hose from the boost gauge to the throttle body, where the hose to the "how do you say? Valvelid? originaly is inserted."
Dunno if this is a good place to mount it but it shows about 2-3psi when i´m at 2-2500r/pm with ~5% of the throttle open. But when i give it full throttle i loose all the pressure. The same if i´m reving the engine.