Many questions

[little ghost]

What does detonation feel like whilst driving?

I know the ignition is retarded etc automatically until detonation stops, but how can you tell if it's happening? is there a huge loss of power?

I ask because my car seems to be easing off under part throttle, also at the mo i have my bleed valve turned up hugely, although both my mechanical boost gauge and factory gauge read .75 Bar max with my foot to the floor. I've been told this problem may be down to actuator on the way out?

Under part throttle, boost jumps immediatley to .75 but on wide open throttle boost is still .75. Does this mean the engine is leaning out under part throttle? If it is a dodgy actuator, what's stopping the boost from going above .75?

As far as i know the car is on the standard fuel pump...
Fault code checked all clear...

Any help appreciated

 

[Fast Guy]

Detonation can feel like a bad backfire, before you get it full on you tend to get pinking which is a metallic rattling type of noise. If you recognise this sound then back off the throttle to save damaging your engine.

The ecu retards the ignition and uses the boost solenoid to knock about 2psi off your boost, when it senses det.

Do you have the jap gauge? in which case .75 will be 750mmHG which is over a bar and off the scale. If your bleed valve is open hugely you could be running beyond the limits of the turbo and more than 1bar. If your gauge is definatley reading in bar then ignore this bit.

You could possibly have a sticky wastegate or a weak spring.

 

[little ghost]

Thanks for your help mate. ok, so it's not detonation...phew!

Just so we're clear, yes it is a jap mm hydrodgen gas thingy gauge, but the reason i say it showed same reading as my mechanical is that is was roughly right for where it was off the end of the scale! +7 (or 70) is standard boost correct? so 7.5 (or 75) is just over standard? in any case, the mechanical shows .75 of a bar peak.

Anyway, today the car was driving fine...under part throttle...part boost was observed... the needle moved according to where the accelerator was...

Whereas the other day, part throttle= full boost, full throttle= full boost.

Which of the two ways is correct for how the car should act? straight to full boost under part throttle or climbing?

I've sort of sussed that the car isn't leaning out under part throttle, because it would know how much air it was sucking in wouldn't it? and fuel accordingly?

How would a sticky wastegate cause this problem? as the wastegate would only open when peak boost is reached right? if it's wrong for boost to climb to peak that means the wastegate is opening early right?

Sorry, head in bits. You gotta sort me out here