Pogue

1, Was boosting at 16 psi, fitted decat downpipe, now boosting at 19 psi, why ?

2, The heatshield no longer fits, should I trim it down or leave it off ?

3, What oil pressure sender will fit in the #3 cylinder oil gallery, I have the adaptor (1/8 npt to 18x1.5) but the autometer sender is too tall and hits a pipe from the turbo inlet (MY98 UK)is there a smaller/shorter sender ?

Any help gratefully received

STi wanna Subaru

iTrader: (1)

Give us more info about your car? year, model, mods?

Pogue

UK MY 98
Dawes
Full decat (Scoobysport)
Itg filter

STi wanna Subaru

iTrader: (1)

I would say your boost gauge is over reading for a start. I'm not sure what the fuel cut is on a MY98 but on the MY99 it's about 17 psi. I think it is less on the MY98.

Have you hit fuel cut yet? (a sudden loss of power, normal in 4th or 5th)

I know people would recommend a knock link with that set-up to check for det, especially as you have raised the boost.

I'm sure other people can offer better advice than I can.

STi wanna Subaru

iTrader: (1)

You would normally have to cut the heatshield to fit. I had to remove the bottom 1/4 to fit over my scoobysprt D/P.

Was the Dawes on before you fitted the downpipe? have you altered it?

Pogue

The guage is dead-on, it read 12-13 psi before I fitted the Dawes.
It will spike up to 19 but cut immediately, if I accellerate slower the fuel cut comes in at 17. I was just wondering why changing the downpipe would make it boost higher.

SiHethers

Pogue

I've had exactly the same problem with my MY99. The original exhaust is restrictive and the wastegate gas enters the turbine gas close to the turbine. The combination of these mean boost is lower for any given degree of wastegate opening compared with a free flowing exhaust. As this is controlled by your Dawes, with your now low exhaust back pressure, which means a more efficient pressure difference across the turbine, you get more boost.

Thats my reckoning anyhow

The solution is to wind back the Dawes until you achieve the desired boost. Even doing this I still get some pretty crazy peaks as spoolup is so fast. My current plan to fix this is to remove fuelcut so I can run a higher target boost, say 18psi If that doesn't work, I'll lengthen the wastegate actuator rod to soften the boost delivery. Make sure your bleed hole on your Dawes is 1.0-1.5mm also as a small one will accentuate overboosting.

Note I've also got a knocklink and deltadash for monitoring, and use NF booster. I wouldn't recommend doing what I'm doing without these measures

Simon

Pogue

Cheers Lethers

I've got the dawes at 1.5 mm already and I have an HKS FCD on order.

I'll wind the Dawes out tonight so I'm back at 16psi.