Why is this happening? Re: Boost Falling Off
Why is this happening? Re: Boost Falling Off Well I finally got my pulley alignment issue sorted out with my MMS crank pulley. I have a 4.0" blower pulley. I took it out for a few runs and it pulls well down low but it can barely do over 5#. What is happening is at WOT, at about 5200rpm my boost is at about 5# then drops suddenly to about 2.5# and lower. It's hard to tell but it sounds as if I hear some wooshing air when this happens... I dont think it is my ATI Race bypass valve because it is pretty heavy duty. Is this a sign of belt slip? I kinda thought belt slip would hold a certain psi not drop. Do I have a massive leak somewhere? Every hose clamp is tight. I double checked all of the piping. Bad head unit? Anyone had this happen to them? Thanks!
Originally Posted by Got Me SOM
prob belt slip. tighten her up.
On The Tree
Joined: Jan 2005
Posts: 104
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From: Northern Virginia
Boost problem Exact problem I was having, 5200 rpm boost dropped, did you make sure your vacum line is on the correct side of the vacum check valve, Also have you check to make sure if your knock sensors aren't coming on and retarding your timing. What heads are you running and bore size of block, Also did you key your crank for your balancer. Do you know your spring # what are they open and closed.
Originally Posted by 1FASTLS
Exact problem I was having, 5200 rpm boost dropped, did you make sure your vacum line is on the correct side of the vacum check valve, Also have you check to make sure if your knock sensors aren't coming on and retarding your timing. What heads are you running and bore size of block, Also did you key your crank for your balancer. Do you know your spring # what are they open and closed.
I would recheck the BOV installation. I know in the ATI install manual it states to make sure the valve is installed correctly. " With the pro flow valve inlet end is the end with the screw head in the center of the butterfly valve".
Might even try to just take it out for one easy run and see if that cures your problem. If you build boost then, well you can either narrow it down to a bad BOV or a Vacume source problem.
Might even try to just take it out for one easy run and see if that cures your problem. If you build boost then, well you can either narrow it down to a bad BOV or a Vacume source problem.
Originally Posted by 618HAWK
I would recheck the BOV installation. I know in the ATI install manual it states to make sure the valve is installed correctly. " With the pro flow valve inlet end is the end with the screw head in the center of the butterfly valve".
Might even try to just take it out for one easy run and see if that cures your problem. If you build boost then, well you can either narrow it down to a bad BOV or a Vacume source problem.
Might even try to just take it out for one easy run and see if that cures your problem. If you build boost then, well you can either narrow it down to a bad BOV or a Vacume source problem.
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Belt slip, look for the belt powder around the pulleys and the face of the alternator, around standoffs...those are the places it'll build up. With the MMS, I had to tighten the **** out of the belt to the point where I could pluck the belt like a guitar string, and belt dressing was used in massive quanities.
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SDCE is your friend
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I'm going to ship out my bracket to SDCE next week. I am fed up with this bulllshit. Tomarrow I am going to mark the crank and pulley and check for rotation. I will also make some runs with the bypass unhooked. Unfortunatly I can't tighten my belt anymore. I have the dual idler bracket and if I crank the tensioner any more the belts will touch. Right now they are only about 1/4" apart.
Originally Posted by NA$TY-TA
ill have to agree.... with the MMS and a 4.o" blower pulley i was seeing 11 psi on a stock motor, baby cam, LT's and LS6 intake..... belt slip......
SDCE+ATI = perfect set up.
EDIT..now thats more like it, with the SDCE set up you won't have to worry about the belt ever again.
MMS was fun but I ran through belts like nothing with that set up...the cog was even worse.
Originally Posted by SSls1man
Just asking , how can you rule out the B/P valve ? Boost is droping out at the same time "wooshing air" is heard ?
Originally Posted by frcefed98
Have you tried a smaller belt? Might take some effort to get on, but you might be able to make it work..
I really wish ATI would actually try to make a kit that works, especially when someone lays down that much $ for one. Without any outside modifications mine couldn't even hit 5#........... pathetic.
Originally Posted by Ferocity02
Anyone have any SDCE boost numbers so I know which pulley to get? I'd imagine I want the 4.0" one. I am looking for a solid 8-9#.