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Knock Values On Powerfc

Spook's_Skyline
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itbmils Proficient

itbmils

Posted
Posted

what about the internals used - forged internals will read higher knock - yes ?

this is especially so when the engine is cold.

I get readings in the 40-55 range on my R32 GTR - but dyno testing show no ping (thank god!!)

I've spoken to guys that have built and raced GTRs for many years - and the answer to this question depends on many factors. So I guess - the correct answer is - it depends

Get your car on a dyno – that's the only way to tell for sure (AFAIK)

Cubes Grand Master

Cubes

Posted
Posted (edited)

Forged internals won't read higher.. Maybe if they are running super sloppy clearances, if that were the case the motor wouldn't last much longer than 25,000km's.

The knock sensor works off various frequency's..

I have forged pistons in the 3ltr that run on the sloppy side, to Wiseco's 24+psi/race spec. They see a max of 10 on start up, once idling and you can hear the pistons slapping away, knock is 1.

When reading knock levels I think the trick is to watch the graph, under acceleration it will rise up and hold fairly even, ping or detonation is when you see sharp little spikes. If yours is rising to 45-55 and those values are consistent, i.e no spikes then there's no need to worry.

Also remember a little spike here and there won't hurt a fairly stock motor, push 300rwkw+ through it and its a different story.

Edited by Cubes
The Mafia Grand Master

The Mafia

Posted
Posted
yer my car will idle at 3-7 but a WOT can get up to 25-30 and have seen it get to 42 max when backing off mainly was tuned on a dyno

you'll find that what you have just stated is pretty damn spot on

itbmils Proficient

itbmils

Posted
Posted
Forged internals won't read higher.. Maybe if they are running super sloppy clearances, if that were the case the motor wouldn't last much longer than 25,000km's.

The knock sensor works off various frequency's..

I have forged pistons in the 3ltr that run on the sloppy side, to Wiseco's 24+psi/race spec. They see a max of 10 on start up, once idling and you can hear the pistons slapping away, knock is 1.

I have wiseco's too - not sure on the clearance - but it's VERY niosy @ start up, and I get higher knock readings (still under 50 tho)

When reading knock levels I think the trick is to watch the graph, under acceleration it will rise up and hold fairly even, ping or detonation is when you see sharp little spikes. If yours is rising to 45-55 and those values are consistent, i.e no spikes then there's no need to worry.

good advice - I have not looked for this - but I think I'm OK

Also remember a little spike here and there won't hurt a fairly stock motor, push 300rwkw+ through it and its a different story.

well - I am pulling 300awkw - so why is that different (knochk is knock - right) ?

Cubes Grand Master

Cubes

Posted
Posted
I have wiseco's too - not sure on the clearance - but it's VERY niosy @ start up, and I get higher knock readings (still under 50 tho)

good advice - I have not looked for this - but I think I'm OK

well - I am pulling 300awkw - so why is that different (knochk is knock - right) ?

Its interestering you get high knock readings on start up, I know of an other R32 that on startup spikes to 50 or so. Why it does this I don't know, it shouldn't but it does.

I have heard some VT Commodores ping on start up.

Probably just a bad ignition timing and rich cold start afr mixture causing a rapid uneven burn.

Detonation is detonation but when you make more power you have higher combustion pressures, as a result a little detonation is much more likely to damage something. Exactly why those little old ford lasers can rattle along for many years without cracking a piston. :D

Chris32 Veteran

Chris32

Posted
Posted

mine registers about 30-40 on startup

I reckon its something to do with the starter motor on the flywheel

Engage that while the motor is going, I see about 40 knock if I do that

itbmils Proficient

itbmils

Posted
Posted

OK

let's take this thread in slightly different direction

is what the PFC reads as knock actually detonation ?

WAIT !! before you answer ....

I have just had a power run done this morning - and one of the things I asked them to look at was knock. My PFC will sit @ ~40 all day - even under light load and low boost, but I have no signs of detonation (or so I'm told). This has been checked and rechecked by three different workshops on three different dynos and three different days.

if the man with the head phones on says – no ping – then I happy with that :(

My understanding is that the knock sensors will pick up ANY noise – and translate that into a reading on the PFC hand controller. This supports my understanding that if you have forged internals with large clearances – you'll get what the PFC picks up as knock – but it's not actually detonation – it's just a noisy engine.

I had an old 323 BMW that had the same thing once.

I have weisco pistons – and I do no know what clearances where used – but I do know that I can hear the forged internals – even once the engine is warm. So if I can hear them – so can the PFC.

This is all just my opinion, and opinions can be changed – so I'm happy to hear evidence to the contrary.

gawdzilla Contributor

gawdzilla

Posted
Posted

I have wisecos @ 87mm.. i don't really hear the piston slap, and the motor doesn't sound any different once warmed up. My knock gauge on the pfc floats around 0-25 while just driving around normally. No abormal knock value upon startup.. my guess is around 0-10 on the start. haven't gunned it yet on the new motor (no tune)

itbmils Proficient

itbmils

Posted
Posted

so - I'm guessing I have a loose motor

clearance was set by Marty White from John White Racing up here in Bribane. They also did the hone and deck of the block and a port and polish (reco) of the head.

He does the work for Theo W - so that was good enough for me (yes I spoke to Theo before going to him)

Cubes Grand Master

Cubes

Posted
Posted (edited)

Might just be an 'over active' knock sensor. Picking up frequency's it shouldn't or something?!? :P

On that note now the warmer weather is here I can't actually here any knock. I had a listen this morning.. No Slap, water temp was 24degree's before I had started the car first thing this morning.

Last winter some mornings I saw water temps of 2degree's. :D

Edited by Cubes
paulr33 Grand Master

paulr33

Posted
Posted

i havent noticed much more knock since air temp's have increased. if anything they are a little better. i dont get any knock on startup. i think knock of over 100 ish is "detonating" as ive never heard mine ping on the road. only time ive ever heard my car ping was stock everything and i ran 1 bar (bypassed the actuator by accident) and then it pinged its ass off

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