Feck me! (Unexpected BPU)

[Homer]

I managed to boost at 1.3 on the way home today. I have a 1.0 bar RR :S

 

Have you read the rest of this thread mate

 

You don't have a 1.0 bar restrictor ring, no such thing exists. No restrictor ring is set to a particular peak turbo pressure, there are other factors involved to determine the turbo pressure, a key one is charge denisty (which varies dependant on weather conditions)

[monsween]

yea i have read the rest of the thead

 

i know its an inacurate system at best hehe

[nigelboyne]

Thanks, seen that article alright but since IK 22/IK24 fall under the up to 1.3 bar just was wondering what they where like in reality (Peoples experiances)

 

i ran ik22 when high setting was 1.2bar they were fine. run ik24 now i have first cat out and boost up to 1.4 seem to be fine. change every 2nd oil change 10k. you might get longer out of them if your useing car as daily drive of boost

[TLicense]

As for the 2nd point, surely if the EBC works the way it has been explained then it is progressive too? The solenoid lies about the pressure by x% as it is duty driven? At 1.0bar it tricks the system into thinking it is only at 0.6bar or something around that. This would mean that it would be allowing 0.6bar to the wastegate actuator. As the wastegate actuator actuates at 0.7 or thereabouts it would remain closed. Also, the stock system obviously uses a spring in the actuator (or a vacuum, not sure) so that would mean, if your thinking is correct, the EBC would give a faster spool at the same boost levels? Not heard of that one before. Would be interesting if it was the case though

 

Ah no. I may be wrong but I think you've misunderstood how the BC is controlled within the electronics. You dial in a % duty that corresponds with the boost target that you're looking for. So say 50% duty could equate to 1 bar for instance on your particular car. However you also have control over how quickly the BC opens the solenoid to that percentage. This is gain and is strictly called proportional gain as it's basically the 'P' part of a P.I.D. control system. (There's loads on the internet on these).

Setting a high gain will mean that the controller will ramp up really quickly from 0% duty to 50%, but as they only have an predetermined integral function (the bit that slows the rate of increase down as you approach the target 50% in this example) it can end up overshooting the target. As it's overshot it then tries to reverse the direction and reduce the value back but can end up undershooting and so on. It would basically be an underdamped system.

If you set a low proportional gain you'll creep up onto the 50% target but because you've taken a length of time to open the solenoid you can end up with a boost spike. (Remember that boost is rising all the time until the target reaches 50%) This would be an overdamped system.

The ideal situation of course is where you set the gain as high as possible and just before the system goes unstable. This called critically damped.

 

The stock system does have an EBC of sorts as it has the wastegate actuator VSV, which is controlled by the ECU.

 

I hope that helps. It's a bit of a job to get your head around at first.