JGM Simon... confused

Car's got half a tankful of V-Power in (but it was mapped by you on 'only' Esso 97, with knock level set to 40). Went to overtake in third gear, then fourth, before manouvre completed.

Checked Commander and got a knock reading of 56! - not the 40 or less.

Parameters got up to:-

Knock... 56
Boost... 1.09kg/m2
Revs.... 6251rpm
IDC...... 93.5%
MAF..... 4830V
Temp.... 94C

Obviously don't know what ign adv would have been as it logs max adv e.g. at the lower loads, etc.

Can higher readings simply be a momentary 'spike' and therefore, nothing to concern myself with? ... Didn't notice any rapid flashing of the CEL (but I may have missed it, if it would have ).

 

It could have been "noise" picked up on gear change.

 

Duly noted mate ... any more suggestions?

 

One off or consistent?
Could be bad tank of fuel.
Did cel flash?

 

Don't normally go on boost when going to/from work (rarely hoon) - so just the once thus far. Also, pretty sure the CEL didn't flash, as it normally does catch my eye (paranoia you see )

I'm actually off to Zen tomorrow for a new starter, cooler 'stat and 2 new remaining coilpacks to be fitted. When that lot's done, then on the way back I'll try some acceleration runs (re-zeroing on the Commander after each one) to find out what the max knock level seems to be settling at... I'll post up my observations.

Cheers.

 

could it be down to a fualty coil pack, as you are getting these replaced?

 

It's a possibility. They are just on the edge according to Paul at Zen. He said they would just about tolerate the 1.1bar of boost - but that was in August. So they could have further deteriorated since then.

I'll see what happens after they get fitted...

 

Get Paul to check with det cans rather than waiting until the way home
if it is missing slightly it would cause a higher knock reading.

Simon

 

Ah yes, good idea! lol

I'll do just that, thanks

Also, Simon, would my slightly higher than normal coolant temps promote knocking - or does the PFC 'suss' that out, and would temper boost/ign anyway?

 

how high is your knock count normally ?

 

JGM mapped it and set the level to 40 (motor quiet at that level)

 

temp does seem high to me, IIRC my temps used to be between 87 - 91, would creep up in traffic but the fans kicked in at 92 I think so it didnt stay there for long.

Could also be gearbox noise though, especially if you changed gear at over 6k

 

Well as it was mapped mid last year and has been perfect until now something must have changed.
Yes high water temp could bring on det

 

Failing head gaskets and elevated engine coolant temps would appear to be the culprit here. I am sure John will be able to comment further!

 

Right, here's the story...

Tim at Zen done a blinding job today fitting the Zero Sports 71deg C stat and a GGR remanufactured water pump. Annoyingly though the old stat still opened (albeit very slowly) and the old pump looked perfect - free spinning, blades in good condition, etc. (I really wanted the stat NOT to open lol, or the pump turbine to be broken off the shaft loler... but unfortunately no. Damn it). Also, sniffer test didn't turn yellow one iota, though .

Anyway, I instructed Zen to fit the new stat and pump, as it would at least rule out those two culprits, plus a possible potential airlock (as new coolant was carefully filled via the turbo's coolant hose, with the bleed hose to the rad's top nipple disconnected).

When we ran the car up to temp, all was looking excellent - temps rose much slower and stabilsed at mid 80s (on the old pump/stat, they would 'rapidly' climb to 97 odd!). Stat opened and you could feel the bottom hose get hot. Fans kicked in dead on 90deg... I was really encouraged.

Tim took it out for an extensive test drive. Came back 20mins later with a deadpan face, popped bonnet and...... worst fears confirmed. Rapidly bubbling coolant in expansion bottle, bottom hose stone cold, header tank level gone down by half and - here's the clincher - header tank reeked of combustion fumes big style! They totally overwhelmed the sweet coolant smell!

So, when on-boost, massive airlock created! So Pavlo, you and JGM - and others - are spot on!... need new HGs!

So Simon, in answer to your question, defo elevated temps bringing on those high knock readings (as agreed by Zen's Paul too - he picked up on it straight away).

So no on-boost driving till HGs are done.

BTW, off boost car temps are now wicked - typically between 83-86! At least I've got a pukka coolant system now: silicone top and bottom hoses, new rad, new pump, new stat

So not all bad, I suppose.

 

hope you get it sorted soon, probs not the best time to happen.. how much is it looking to cost?

reading all these threads on here lol scares you, i never had any knock detectors on my old scoobs etc.. and they ran perfect in my time i had them.. the more knowledge you get the more worry comes with it..

but then again i wasnt a member of any forums during the time i had them, except my last one and that was only a few months

 

Don't be put off eggy.

BTW, the knock reading is only an upshot of the high temps - not the other way round.

When you're on/off boost, the HGs literally 'rock' about on the cylinder head surface - I've probably got a very small fracture/gap created that is enough for gases to get past under high boost conditions only (hence the negative sniffer test) and into the coolant galleyways...

When the HGs are fixed, Im sure the knock readings will come back to below 40, like they were before.

 

cheers lol sometimes it makes u think , just kee it standard lol but the modifying bug gets you

and once ina modified scoob the standard 280 doesnt feel fast no more

 

Yeah, modding can be a double-edged sword sometimes. 'Cause when stuff goes wrong, you always ask yourself "What if I had never done that?..."

Who know what's caused the gasket/s to fail? It could have been that slow stat causing the coolant to back up in the system, raising temps .

Thing is, my coolant system issues seem to have stemmed from when I decided to fit an STi upped 1.3bar pressure cap. From that point on, after about a couple of months the top hose split and rad got a pinhole within two weeks of each other! It could have been the upped pressure because of the cap that could have caused the HG to fail - who knows? .... Damn, why did I fit that cap?!!!