Problem With Boost!

[Banjo]

Hi my ST185 GT4 has been fitted with a blitz dual spec s boost controller. It seems to boost up to 1 bar and then drops to 0.75 bar. Ive checked all hoses and there doesnt seen to be any leaks.

Does anyone know what i could be doing wrong as i cant seen to keep the boost high in the other gears it just drops! Thanks this problem is driving me daft!!

[richiekuk]

Hi, pretty sure that the characteristics of the 185 and 205 would be the same.

I set my boost controller up on the rollers last week, and found the boost spikes first to a high reading then drops off.

You should be able to sort this by going a bit more in depth with the set up of your boost controller, and altering the boost across the rev range and the duty cycle.

Takes alot of trial and error.

If it was set up on a rolling road by a professional then take it back cos he should know what he's doing and be able to keep the boost relatively stable.

Richie K

[Sketchy]

Also have you disconnected and blocked off the TVSV??

Initial overshoot is caused when you try to increase the boost to quickly for the wastegate to keep up.

When you use a boost controller you effectively blocking the boost signal to the actuator until a set boost level occurs then you open the path up. At this point the actuator sees the boost and starts opening the wastegate in an attempt to control it. Normally this results in overshoot due to the time it takes for the actuator to come up to pressure and open the wastegate and then for the exhaust gases to be diverted. Once open the wastegate pull the boost down to the required level at which point the boost signal to the actuator is cut so that the level you want is kept. etc.

That's a basic system eg relief valve.

With an EBC the solenoids in the boost pipe are normally of a variable type so you can adjust the rate of the initial boost rise (Gain). i.e. the valve opens slightly at an earlier point and gradually opens more up to the require boost level. In this case the actuator is partiall filled as the boost rises so that once the boost level reaches the correct point the wastegate is fully open and the boost is being correctly controlled and you don't get any overshoot. This is the other end of the equation and will result in no overshoot but also the slowest boost rise rate.

The trick is to adjust your settings to get somewhere in the middle where by you have a good rise rate but also an acceptable amount of initial overshoot eg 1-2psi

[Banjo]

Thanks guys....The advice is much appreciated ive tried it and it seems a bit better. :)