Hi All,

 

I think I've narrowed down my less than perfect top end performance to boost leaks.

 

I get some detonation when I floor it - more noticable with extra passengers/weight on board - preumably the detting will cause the ecu to switch to safety boost mode and retard my ignition - the boost stays high as I'm using an AVC-R, detonation continues due to high boost (stop me if I'm talking cr*p already..). I'm assuming my leaks are the cause of the initial detonation...

 

I get some whistly hissy noises from one side when boost kicks in and am plagued with a noise like goosehonk which may well be a leak around the intercooler.

 

Can anybody confirm or deny mt suspicions please? Some of the hoses are a real pig to get at - presume an engine out job for some of the turbo hoses??

 

Thanks a lot!

 

RobH

I'm no expert, but from what I've read I thought the det sensor only worked below 3500rpm or something ??

 

I could have my wires crossed and by talking absolute bull though :D

Hopefully you're right about leaks cos I just had boost contoller fitted and now get det when i floor it and that special howl from the engine bay. also my boost goes through the roof 18.5 psi on the gauge! I wonder if thats a miss read due to boost leakage.

 

anyway sending it back they can fix it as they broke it

OK, I've done a bit more reading and it does look like the det sensor only works below 3,500 rpm - but what's the use in that?? Surely det is more likely at higher revs/engine temperatures??

 

Is a boost leak likely to cause detonation? When off boost I can see that extra air could enter the system but when on boost surely the pressure escaping would keep extra air out and actually make a richer charge!?

 

Anybody any thoughts on the possibility of ignition being retarded during detonation at high revs due to safety boost? I s'pose if det has ocurred at low revs the ignition will be retarded until ignition is cycled (?)

 

Last question - I read that decatted systems should be using LRP rather than super unleaded - is this correct? My pipes are recently decatted...

 

Cheers!!

 

RobH

Rob,

 

If your using an Avc-r then the detonation sensor circuit is unable to limit the boost pressure if the ecu is trying to run with safety boost.

 

The only thing the ecu can do on your Z if either it detects detonation or you have a faulty det sensor is retard your ignition timing. It should switch off the boost control solenoids but it is likely that yours have been disconnected when the boost controller was fited.

 

Your detonation could be a number of things.

 

Have you tried an ecu diagnostic to check for error codes? How much boost are you running with your avc-r?

 

As for a possible boost leak, this shouldn't cause detonation. If the metered volume of air doesn't reach the cylinders because of an air leak, you would generally find that the fuelling runs very rich. This would also be obvious through black smoke from the exhausts under hard acceleration. This is because the injectors are supply enough petrol for the air expected to arrive at the cylinders. A richer fuel mixture can help with detonation.

 

Unleaded or Super unleaded is the petrol you need to use and not a LRP fuel.

 

Hope this helps

 

Steve E

 

 

Originally posted by RobH

OK, I've done a bit more reading and it does look like the det sensor only works below 3,500 rpm - but what's the use in that?? Surely det is more likely at higher revs/engine temperatures??

 

Is a boost leak likely to cause detonation? When off boost I can see that extra air could enter the system but when on boost surely the pressure escaping would keep extra air out and actually make a richer charge!?

 

Anybody any thoughts on the possibility of ignition being retarded during detonation at high revs due to safety boost? I s'pose if det has ocurred at low revs the ignition will be retarded until ignition is cycled (?)

 

Last question - I read that decatted systems should be using LRP rather than super unleaded - is this correct? My pipes are recently decatted...

 

Cheers!!

 

RobH

18.5psi! Too much without bigger turbo's / intercoolers / injectors.

 

A problem with yur gauge would only read a lower pressure.

 

I would reduce your boost to 14psi or prepare for a melted piston or two!

 

Steve E

 

 

 

 

Originally posted by Voldermort

Hopefully you're right about leaks cos I just had boost contoller fitted and now get det when i floor it and that special howl from the engine bay. also my boost goes through the roof 18.5 psi on the gauge! I wonder if thats a miss read due to boost leakage.

 

anyway sending it back they can fix it as they broke it

Steve, thanks for the input. I'm running about 0.9 bar but TBH it's a bit erratic - sometimes won't make 0.9 on the setting I'm using - maybe due to boost leak getting worse with engine temp.

 

I've done the diagnostics and get 55. I guess if I get some detonation and then the timing gets retarded it may explain why the car sometimes feels a bit sluggish at high revs but next day it flies...

 

My coolant is a nasty orange colour - I've drained, flushed refilled at least ten times in the last year and it's still murky...dunno if it's not cooling properly.

 

So it looks like I have two probs (and the rest!!) boost leaks sapping my power and detonation erm...sapping my power. If I fix the boost leaks I'm gonna get more detonation until I can cure that one too! Maybe I'll look at the detonation first...

 

Cheers...

Rob

 

Check out the thread from Vijay about boost leaks.

 

Also, check the wiring harness connection to the engine temperature sensor and detonation sensor.

 

If you boost while the ecu is trying to run safety boost then your engine temperature will run hot.

 

I would also look at the boost pic up hose to your avc-r. Are you using the electronic gauage from the avc-r or do you have an analogue guage?

 

Steve E

Steve, I got a boost leak 'dummy' from Vijay and had a go with it over the weekend, very useful - problem is that I think the leak is so big the system holds no pressure or it's escaped as soon as I turn off my cr*ppy compressor - need more air more quickly.

 

That would kind of explain why I'm detonating badly at high revs sometimes - running hot on high boost when ecu thinks there's no boost - very interesting!

 

I'm using the AVC-R's built in gauge. All pipes have been checked as good for that part of the circuit.

 

I've repaired the engine temp sensor connector recently but I'm not convinced by the job, I'll have another look tonight. Det sensor circuit all looked ok yesterday.

 

Don't get me wrong - the car is mental as it is, I just feel it should be more mentallerer..er. ;) and shouldn't be detting like it is...

 

Cheers!

Sounds like a big leak.

 

You might find that air is sucked in off boost and leak on boost.

 

This will explain why your boost is not stable but I think a leak this big should be easy to find.

 

Steve E

LOL - not if you're me Steve! I'm terrified of putting my head under a car on stands...

 

Thanks for all the input..

 

RobH