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i have a bpu car and sometimes i can get to 18 psi and then most of the time it barely goes past 15 psi and i was wondering what the deal was and why it varies so much. any help would be appreciated.
 
J

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you probably have a boost leak somewhere. you can try tightening and reclamping your intercooler pipes. that is usually the case. i'd try there first...
if not, it could be your plugs.. change plugs every 3000miles probably would be good. ngk 3330's at the gap it comes in.

good luck!
 

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boost leaks are not usualy intermittant, bad plugs won't give you intermittant boost problems. an increase in ambiant temp could do it mor spefics would help. Are you having some transistion problems between 1 and 2?
 

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no, i'm not having any trouble between the first and second turbo. i can get almost 14 psi with my first turbo and then my second only goes to like 15 or 16 most of the time. i just put new plugs in it.
 
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What if

Sorry to butt in here, but what is usually the problem if you have problems with the 1 to 2 transition? It seems to take a really long time with mine (stays at around .6 bar) then jumps up to maybe 1.2 or so. Car definitely is down on power, but I just tightened all the hoses to the intake. May be unrelated, but on there is a strange fluttering sound at WOT coming from around the intake manifold side of the car. Any ideas?
 

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EGCV actuator bad, bad vsv to egcv leaking pressure tank or bad Iacv actuator or vsv.
If any of these valves aren't working properly, you'll have low end boost problems:

1. BOV (boost will get bled back to intake)
2. EBV (loss of exhaust energy)
3. EGCV (loss of exhaust energy)
4. WG (loss of exhaust energy)

Now if the EGCV, or EBV aren't working properly, you should have strange transition problems, as well as low boost on the low end.

If the problem is the WG, you should suffer low boost consistently, whether it's only #1 or 1+2.

If you're suspecting a stiff/sticking EBV, try pressurising its actuator with air and see if the motion is jerky. This is a real tough one to watch, especially on a hot engine.

Being a lazy individual and knowing that Supra failures tend to follow patterns, I'd look hard at the EGCV actuator. Mohd and others have found this to be one of the culprits of low boost.
the above from a converstaion I had re same problem on mkiv.com from john cribb
 
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