The story is this.

Since being mapped by AndyF 2 years ago I have had no problems at all.

I have altered the rows above 15 to allow an increase from 1.25 bar to 1.45 bar and still only get 10 -15 (same as before) on my commnder knock readings.

Bearing in mind that nothing else has changed (except a wideband sensor), why would I get a sudden spike of say 20-30 on cruise?

Its only every now and again and doesn't light up my knock link at all. This is over 3 tanks of V-Power from 2 different garages.

I'm stumped unless something like the MAF is about to fail?

Wayne.

 

There was a thread about this a little while ago.

Mine to does this, usually on over run.

Spoke to Paul who mapped the car and its quite common for this to happen. As long as it doesnt happen when the car is being driven hard its not a problem.

 

True, but if it suddenly starts doing it when it didn't before then its not normal.

Just thinking that something may be wrong thats all.

Wayne.

 

Guess the only way you will know for sure is if you can get someone with det cans to check it out.

 

Knock sensor can pick up other engine/road noises too. If it just an occasional spike (and 30's is still very low, my PFC is set to warn if it hits 70+) then I wouldnt worry about it. If it is a consistant thing, especially under hard driving conditions it would be worth looking into.
As said, 30's is still low. Before my rebuild, I would quite often see the knock spike up to high 20's low 30's and occasional 40's under hard driving on V-Power

 

Every engine is different though....

Have you correlated the PFC knock count with actual audible det?

IMO, it's a bit misleading to suggest to the original poster that he shouldn't be worried about 30 / 40 counts, when it may actually be detonation and not just background engine noise increasing with rpm.

...just my 2p worth

 

what is it you have adjusted, is it the fuelling and timing?
It could be that you are switching between load sites under certain conditions and it is this what is causing the spikes.

You best bet though is speak with the original mapper in question and find out like fiestaboys says what level was actually knock and not just noise.

 

The parts of the map that I have adjusted are above row 15 so nowhere near where the load points for cruise conditions (rows 6 -8). Fuel and timing adjusted and wideband showing 11.8-11.4 afr through the range on full chat. Knock at 1.45 bar reads 10 - 15.

The areas of the map for cruise are unchanged in the last 2 years since mapping. So I would have to state that it is NOT the map.

The reasons for my concern are shown below

1) This is NOT normal for my car.

2) It has started to do it after everything, including my mapping has been proved to be fine.


I am looking for what may cause it, such as anything being faulty or on its way out. I was thinking that maybe a rich mixture may leave fuel in the cylinders causing det, although my wideband shows 14.7 on cruise.

I have no idea.

Wayne.

 

If it never did it before and nothing in the fuel or map has changed then perhaps it's a 'hardware' problem i.e. a fuel pressure regulator or fuel pump on the way out? I had knock spikes showing on my Power FC on very light cruise and it was bloody annoying - take it from me, I know how irritating it is. Regardless of how 'harmless' it may be, you WANT to know what's causing it when it never happened before.

So my bet is on something in the fuel system wearing out or going wrong so you're going ever so slightly leaner on cruise than before, which may be enough to push it over the edge? Not enough to show up when you're using more throttle and boost when presumably you're mapped richer anyway and the engine won't notice a slight lean out so much? Just a theory, I may be completely wrong, but check your fuel system. Could even be something silly like a clogged fuel filter.

 

I am looking for what may cause it, such as anything being faulty or on its way out. I was thinking that maybe a rich mixture may leave fuel in the cylinders causing det, although my wideband shows 14.7 on cruise.


...best way to answer that is to buy a set of det cans and correlate what the commander is telling you to reality.

If you've not heard det before, then you'll need to be a bit brave and do a global advance sweep until you start hearing a bit of 'snap, crackle, and pop' starting up.
I know, ... not a great description of something that can destroy you're pride and joy!

Andy F could probably advise better, especially on what spark safety-margin he uses @ wot.

In the meantime, i'd check the condition of the spark plugs, hopefully you've already upgraded to a new set of colder ones when you mapped it with Andy, if not then I'd replace with iridiums asap.