Boost problems on a 97' 945

[Beadybc]

Hello I'm having problems with:
1) Overboost
2) Not enough boost

I've put a 19t on my 97' B230FK and to help control the boost I've fitted this EBC: EBC Instructions. The solenoid valve is fitted as shown in the instructions but the boost sensor is currently T'd between the recirculation valve and the inlet manifold as I wasn't sure what this in the diagram was:
Screenshot 2023-03-06 164058.png

Any guesses?

- Target boost is 1.2 Bar.
- Current external wastegate actuator spring is rated at 1.2 Bar. (I have tried 0.6 Bar as well)

El problems:

First of all, I cannot tell the system my target boost, it's just not a feature. If I set the base wastegate spring pressure on the controller to 1.2 Bar and the boost cut off at 1.4 Bar then as soon as the car gets near to 1.0 Bar, it will shoot up past 1.2 and the boost will be cut by the controller. The same happens if I have a 0.6 Bar spring in and I set the base spring pressure to 0.6 Bar.

However if I have a 1.2 Bar spring in the wastegate actuator and I tell the boost controller that the base spring pressure is actually 0.8 Bar, the car won't overboost, it will underboost by only going up to 1.0 Bar.

If I use 80%+ throttle, the car will get up to 1.0 Bar of boost and stay there though the revs. If I use 50%-80% throttle It will go back to trying to overboost. The same happens if I have a 0.6 Bar spring fitted and I set the base spring pressure to 0.4 Bar.

So currently it's either drive slow or really fast. Any ideas?

[deeman940]

i had overboost problems with a hybrid 19t on my 940. i am not sure what was causing it but i suspect my MBC. i should of got an electronic one. the holes in my head gasket looked like ovals as head was lifting!!

[Rversteeg]

From quickly reading the manual it seems that this is a simple open/close solenoid valve in the line between the inlet manifold and the wastegate actuator. As long as the actual inlet manifold (turbo) pressure is lower than the set pressure the valve is closed, preventing any turbo pressure from reaching the wastegate actuator. The waste gate will remain closed, regardless of any actuator spring you put in. As soon as the required maximum turbo pressure is reached, the solenoid will open the valve and turbo pressure flows to the actuator, opening the waste gate.
I installed my mechanical boost controller the same way and this has been working for many years now. I don't see why you would need the T-piece or mess with stronger or weaker actuator spring. The spring only needs to close the waste gate after the turbo pressure has dropped again.
Rob

[GingerMagic]

Ditch the T-piece, plumb the MBC direct to the inlet manifold ( there should be a spare outlet, you may need an adapter ) and hopefully this will work.

The T-piece can interfere with continuous supply to the MBC, giving sporadic results.

[Beadybc]

Originally Posted by Rversteeg

From quickly reading the manual it seems that this is a simple open/close solenoid valve in the line between the inlet manifold and the wastegate actuator. As long as the actual inlet manifold (turbo) pressure is lower than the set pressure the valve is closed, preventing any turbo pressure from reaching the wastegate actuator. The waste gate will remain closed, regardless of any actuator spring you put in. As soon as the required maximum turbo pressure is reached, the solenoid will open the valve and turbo pressure flows to the actuator, opening the waste gate.
I installed my mechanical boost controller the same way and this has been working for many years now. I don't see why you would need the T-piece or mess with stronger or weaker actuator spring. The spring only needs to close the waste gate after the turbo pressure has dropped again.
Rob

So do you reckon I try using my manual boost controller instead of the electronic one and connect it between the wastegate actuator and the turbo housing?

[GingerMagic]

My bad, my boost gauge is direct to the inlet - the MBC is in the pipe leading to the wastegate.

I'll post a picture if it helps?

[Rversteeg]

So do you reckon I try using my manual boost controller instead of the electronic one and connect it between the wastegate actuator and the turbo housing?

A manual boost controller (MBC) is simply a spring loaded valve. It prevents the manifold pressure from reaching the original wastegate actuator (WGA) until the pressure is high enough to overcome the preload of the MBC spring. The preload is adjustable and should be set higher than the WGA spring. With the MBC set in series with the WGA the highest pressure setting determines the maximum tubo pressure.

The MBC setting is done with a pressure gauge and can only be done under the bonnet.
Your electronic boost controller (EBC) is a bit more sphisticated and uses a valve that is electrically controlled instead of by a spring. The pressure is measured by a pressure sensor and can be manipulated in more ways, even during driving. The principle is the same though: an additional valve in series with the original WGA.

In both cases it is not necessary to fiddle with the original WGA spring as the actual maximum turbo pressure is determined by the additional MBC/EBC. Simply cut the small rubber hose that runs to the WGA and add an MBC or EBC in between. As the hose is quite short, I disconnected the hose on one side, added an MBC and reconnected it by using an additional 20 cm of hose. Piece of cake, takes no more than 10 minutes.

[Beadybc]

Originally Posted by Rversteeg

A manual boost controller (MBC) is simply a spring loaded valve. It prevents the manifold pressure from reaching the original wastegate actuator (WGA) until the pressure is high enough to overcome the preload of the MBC spring. The preload is adjustable and should be set higher than the WGA spring. With the MBC set in series with the WGA the highest pressure setting determines the maximum tubo pressure.

The MBC setting is done with a pressure gauge and can only be done under the bonnet.
Your electronic boost controller (EBC) is a bit more sphisticated and uses a valve that is electrically controlled instead of by a spring. The pressure is measured by a pressure sensor and can be manipulated in more ways, even during driving. The principle is the same though: an additional valve in series with the original WGA.

In both cases it is not necessary to fiddle with the original WGA spring as the actual maximum turbo pressure is determined by the additional MBC/EBC. Simply cut the small rubber hose that runs to the WGA and add an MBC or EBC in between. As the hose is quite short, I disconnected the hose on one side, added an MBC and reconnected it by using an additional 20 cm of hose. Piece of cake, takes no more than 10 minutes.

You’ve made me realise that I was being dumb as I’m trying to run 1.2 bar and have a 1.2 bar wastegate actuator spring so I could’ve just run a hose from the wastegate actuator to the turbo housing so thanks for that.

[Beadybc]

I removed the electronic boost controller but left the boost sensor part in place, the car now boosts correctly but under load it’s still only reading 0.9 bar at the inlet manifold when the wastegate actuator is set to 1.2 bar?