924Board.org

[morghen]

So...i've bought a 1 bar spring from ebay...i'm quite sure its a 1 bar spring....everybody knows that the "silver" marked springs are 1 bar.

the turbo is perfect...no play..not eating oil..no smoke..seals are perfect..all good.
no vacum leaks..no boost leaks.
WG diaphragm is in good order.

teoretical possible causes:

1. POP-OFF valve malfunction - Question: does yours make a loud CLICK whenever the car is at idle and you give it sudden gas pedal?

2. clogged exhaust system - i'm thinking the cat and/or the intermediare silencer could be clogged and restrictive and cause the lack of boost.
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Supercharger and EFI kits
https://www.the924.com

[Rich H]

1: I was wondering that too, mine certanily does!
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1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

[gegge]

[Grenadiers]

Spike has a 1 bar spring as well, and a top mounted GT intercooler installed. I too get less than the expected amount of boost. This car has a solid exhaust system, no cat, rebuilt turbo, and no vacuum leaks. I hear a buzzing noise coming from the wastegate sometimes when slowly accelerating (normal driving), my black 931 does this as well. Almost sounds like a metal on metal rattle, and it's not detonation. Doesn't do it at the higher rpms though when shifting thru the gears at speed.

I manually turned up the boost to 11psi yesterday, and the car took off! THat's when I feel it's going to explode! I turned it back down!

' * severe pressure loss in the intake/intercooler ' - I wonder if this is the culprit as well? My intercooler is solidly attached at three points, so I doubt it's pulling away from the throttle body. So, does the volume of air in charge tube/intercooler affect the WG spring system?

After about 800 miles on the reassembly, time to hoist the brown car up on the lift, take a look at things.
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'83 944 Track car.
'88 924S Track car.
'89 944 Turbo
2004 Winnebago Vectra monster RV
2012 Jeep Wrangler
2014 Kia Soul
2001 Ford F350 powerstroke

[morghen]

turbo is in good condition, no smoke, no oil, no play.

if there is lost boost there should be a woosh sound and there should be oil around the place it goes out trough...i have found no such thing.

i doubt that the turbo cant deliver..its the K26...it should deliver.
and if it does not make boost..then it should flow....wich it does not...the car is slow. 15 secs on the 1/4mile.

so the pop-off valve is probably ok...i took it off..cleaned it..oiled it..and put it back on..did not notice any wear or work plastic parts.

the two theories that stand for me are:

A. restrictive exhaust...wich could also solve my glowing exhaust manifold issue...it glows a bit when i do a few 1/4 mile runs.

B. spring is soft...why this can happen?...no ideea...but i have only one way to test this.

gegge(or anybody) do you have a 1 bar spring that you know it produces 1 bar and you're willing to ship to me for testing? ofcourse i'll pay for the shipping and shipping it back to you.
thanks.
_________________
Supercharger and EFI kits
https://www.the924.com

[Rich H]

Just get the wastegate spring and put a known load on it and measure deflection. So take a KG weight and put it on the spring measure it's length, then get someone else with a 1 bar spring to do the same.
_________________
1994 Lotus Esprit S4 - Work in progress...
1980 Porsche 924 S2 DITC Turbo - Original spec
1978 Homo-Sapiens - Tired spec
1953 Landrover S1 - Pensioner Spec

[gegge]

If you are running 0,7 bar and intercooler I am guessing that you got 200hp already. Even if the compressorside is able to provide required airflow for 1 bar I doubt that the #4 turbinehousing is. The GT got a larger #6 for the same powerlevel and the GTS got a #8 for the level you are aiming at.

I think the pressure in the exhaust manifold is high enough to open the wastegate. The spring has to overcome both inlet manifold AND exhaust manifold pressure. You are trying to raise both.

Three solutions IF this is the problem:

* buy a #6 compressorhousing from GT or S1
* pressurize the top of the wastegate from the inlet manifold
* remove silencers to minimize backpressure
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Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs

[gegge]

A simple trick to check if that is the problem is to remove the wastegate line from the inlet manifold. You should see more than 0,7 bar, maybe even hitting the overboost protection
_________________
Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs

[Vince Ponz]

I have a 1 bar spring and no problems exist. Power comes on strong around 23 to 2500 rpms. No sound of any kind. Prior to putting in the 1 bar spring I would get some whine.

I am happy with it, although I do not beat on it a lot anymore.
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"Never let them see you sweat"
77.5 924 modified track car
79 931 Euro stock
88 924S SE
87 911 Targa stock

[emoore924]

Might be 1 bar at the WG and 0.7 where you're measuring the manifold pressure.

[Grenadiers]

[morghen]

the turbo is a perfect condition K26...should be able to provide plenty..
gegge are you saying that the hotside is too small?

i have a K27 wich i could have installed but the missing BOV and the fact that the cold side was different made me stay with the K26.

i'll remove the line from the intake manifold to see if it gets higher...
My bet goes on restricted exhaust...i'll unmount all silencers, leaving just a test pipe.
thanks !
_________________
Supercharger and EFI kits
https://www.the924.com

[ideola]

Hotside is not the constraint on the K26. Should be plenty good for up to 400 BHP. Cold side is the constraint. I think your glowing exhaust is telling you something. Not sure what, but I think you need to find the root cause of that.
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erstwhile owner of just about every 924 variant ever made

[morghen]

yea..i'm sure the glowing manifold and the low boost are connected.
like i said...my bet is restricted exhaust..i'll try to see in this weekend..before i leave to germany.
_________________
Supercharger and EFI kits
https://www.the924.com

[Grenadiers]

Just a hunch, but have you checked your timing? Could be timing is too retarded either by misplaced distributor, or advance not working properly.
_________________
'83 944 Track car.
'88 924S Track car.
'89 944 Turbo
2004 Winnebago Vectra monster RV
2012 Jeep Wrangler
2014 Kia Soul
2001 Ford F350 powerstroke