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.7-.8 bar with 1 bar spring HELP needed

89 with new Rarly intercooler, zork, 7006 and 1 bar spring. I saw 1 bar on the stock gauge a couple of times before it fell off to .7--this was with the stock turbo LDZ, I thought the turbo was running out of breath so I installed the 7006 and have the same max boost level. The stock boost gauge and the NHS VDO clock replacement installed this weekend read exactly the same so it's not a faulty gauge. Other than these items this is a stock engine with 13,000 miles with zero runnability issues and the inside of the wastegate looks like it came from the factory yesterday. Any advice is appreciated, thanks.

Old 10-26-2010, 08:27 PM
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Sounds to me like we're having the same problem. My '87 has a 1.0 bar spring and can only get up to about .7-.8 bar then starts to fall off. I'm getting my intake system pressure tested with light pressure, then there going to fill it with smoke and see if the smoke starts to come out from anywhere in the intake track. If the intake track isn't my problem, then I most likely have an exhaust leak somewhere. I'll keep you posted on what I find with mine on Friday.
Old 10-26-2010, 10:41 PM
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Assuming the plumbing is all tight you might look at the BOV. Those 2 gaskets deteriorate with time so mileage is irrelevant. A metallic "ting" when you stab the throttle at idle (out of gear) is the clue.
Over-rich on boost can also choke the engine as can other tuning related issues.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 10-27-2010, 06:27 AM
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First suspect is usually the intercooler O ring seal.

I assume you put a new O ring and lubed it properly. Still, I would probably pull the IC and inspect the ring to see if it got pinched and reinstall the IC.

Good thought on the BOV. If that gasket has come apart I guess it could jam up the BOV piston. It is not really a seal, it is more of a cushion so clicking would probably mean the piston is moving freely.

If boost dose not come back quickly with shifts the BOV could be frozen.

However, a 13k mile car and the WG is in such good shape that gasket should be ok but you never know.
Old 10-27-2010, 08:20 AM
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I posted a month ago with the same issue. Bought NHS to verify factory boost reading,(it did), and installed 1bar spring with only a slight increase in boost. So--Eurosport in Denver is replacing the BOV gaskets along with a valve adjustmentnext Wednesday. I will report results next week.

TG
1986 930
Old 10-27-2010, 08:49 AM
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Quote:
Originally Posted by 911st View Post
First suspect is usually the intercooler O ring seal.

I assume you put a new O ring and lubed it properly. Still, I would probably pull the IC and inspect the ring to see if it got pinched and reinstall the IC.

Good thought on the BOV. If that gasket has come apart I guess it could jam up the BOV piston. It is not really a seal, it is more of a cushion so clicking would probably mean the piston is moving freely.

If boost dose not come back quickly with shifts the BOV could be frozen.

However, a 13k mile car and the WG is in such good shape that gasket should be ok but you never know.
I beg to differ. Yes they are seals and do double-time as a cushion. The two end caps on the recirculation assembly need to be sealed or they'll leek boost. You are correct, though, in that what typically happens with age is that the silicone rubber hardens and slowly deteriorates where the piston impacts it. Where do all those little pieces go is the scarey thought.
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Old 10-27-2010, 10:33 AM
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Hi Mark,

No problem. Makes me think.

I had not heard they ever leaked externally, only to click. If an external leak it might be detectable using the brake cleaner trick as the conection side should be under vac at idle.

I still would check the IC O ring conection and other potential leak points first.

However, as this problem seemed to be there before the new turbo, intercooler, and second boost gauge, there is probably something else afoot.

On the exhaust side the WG checked out ok. If there were any major exhaust leaks they would be heard. The only other thing on this side could be a clogged cat if it is was still running one.

It dose sound like something is killing his boost. If it is not going pig rich on boost the leak would probably have to be through the BOV.

Look forward to hearing what it is.
Old 10-27-2010, 11:33 AM
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I had not heard they ever leaked externally, only to click. If an external leak it might be detectable using the brake cleaner trick as the conection side should be under vac at idle..
To be honest, neither have I...but it's always a possibility if either of the two gaskets are so badly aged that they've just fallen completely apart.

Those stock recirc piston valves are pretty bullet proof and not much can go wrong with them outside of a broken spring (which may not allow it to close completely, thus recirculating a portion of the boost) or being seriously gummed up to where it's not moving the full motion. All just theory, as I've not heard of either of these two things happening but there's always a first time.
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Old 10-27-2010, 01:20 PM
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I've seen this one time. The car would not boost at all but otherwise ran perfectly. The BOV gaskets had disintegrated and the piston was jammed in the open position.
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Old 10-27-2010, 02:52 PM
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OT, I know -sorry, but where can I see a picture of the Rarlyl8 IC?
didn't know this had launched.

Thanks

Jesper
Old 10-27-2010, 06:52 PM
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Lookie:

Stock Replacement Intercooler Install
Old 10-27-2010, 07:39 PM
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Side note.

Can anyone verify that the factory style BOV is open at idle or cruse vac or do we think it just comes off its seat a little and takes the vac of overrun to open it?

One way to tell would be if someone has one out of a car and use a vac pump to see at what vac it opens.
Old 10-29-2010, 07:26 AM
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I say check the intercooler o-rings, mine cracked on the up pipe and i lost about 3-4psi
Old 10-29-2010, 07:41 AM
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Back from the shop with BOV seals replaced and valve adjustment----boosting to .8 and falling back to .75 where it was at .7 and falling back on extended boost. Still has a 1bar spring so some improvement but somethng else is still leaking.

TG

1986 930
Old 11-04-2010, 02:24 PM
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We may not be asking the right questions.
> At what rpm does the boost fall off? Full throttle?
> What are the operating conditions?
> Did both turbos hit 1.0bar and then taper off?
> What muffler do you have?
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 11-04-2010, 03:02 PM
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Boost starts to receed at about 6k, tends to hold under partial throttle but fall off under full throttle. Today---65 degrees. Didn't spike to 1bar, only .8. Muffler is stock with cat. But this is a good point to ponder as I had removed the 1bar spring when I ran a Maganaflow without the cat as it was overboosting. Return to stock set up was to get past Colorado emissions.

TG
Old 11-04-2010, 04:33 PM
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Cheap test, take the muffler/cat off and see what happens.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 11-04-2010, 09:11 PM
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.1 bar improvement

got it back from the shop tonight--installed new BOV seals and was told one seal was cracked but nothing impeading the piston travel. Is now holding .8 bar boost--better than the .7 bar before the new seals but we're still not near the 1 bar the spring should be producing---no damaged o-rings so I'm at a loss. this has had to happen to someone else.

Old 11-05-2010, 08:07 PM
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