Knock Levels When Car Has Been Left In The Sun.

[WogsRus]

Ok

So if my car has been sitting in the sun for a while, and i go to start it, the knock will sit at about 20-30. I can drive the car no probs feels much thesame as if the knock was at 10.

Now if i turn the carr off after say 5 minuts of driving, and turn it straight back on again, the knock goes back to say 5 and slowly comes up to 10.

Now i have checked the wirying, definatly got the right wire. Have performed a check on all sensors, and all good, no errors in the ECU.

SO is this common?

Or is there something wrong?

[paulr33]

covered in the powerfc faq in great deal, you should read it (in my sig)

[WogsRus]

Sorry forgot to mention that the reading are form an SAFC II i don't have a PFC but i will read the FAQ anyway.

[WogsRus]

allright read the knock part of teh faq, but it states nothing as to what levels are acceptable, as long as no more then 50.

What i am interested in is that if i turn the car off and then back on again, the knock reading disapears down to 5 or so.

Normally the knock on the SAFC II, shows under 5 if it's cool outside and under 15 if it's HOT outside.

Is that normal.

[paulr33]

do some more reading, read all the parts of it, even the advanced sections on reading knocking signals. knocking has nothing to do with temperature outside. it is (the likely culprit) purely engine detonation that the knock sensor is picking up.

the guide covers the possible causes (fuel, timing, heat, boost) and how to take action to correct it, minimize it and debug it with your tuner (giving them the right information will also help). whilst the guide is aimed at the powerfc, it should be the same logic for debugging it with the safc.

the guide also goes on to list other causes for knock detonation which can include road noise, engine bay noise, mechanical rattles, etc

[WogsRus]

ok BUT, the question remains, i turn the car on, the knock is 30 straight away, drive 5 minuts, turn off, and knock now sits at 5. THIS only happens IF THE Car has been outside in heat all day. OTHERWISE the knock is never above 15 while driving.

[WogsRus]

forgot to mention as well, the SAFC II has a knock reading base line thing, so for example i can set the lowest knock at idle as per the manual, which means that i can reset the knock at the high mark and it will show me zero knock in the monitor screen.

Edited January 4, 2007 by WogsRus

[paulr33]

it just sounds like the calbiration is out, i didnt know the safc had a calibrate function. the car shouldnt be knocking at idle. it would be a really screwed tune or like the worst fuel known to man and the most advanced timing to make it knock at idle. so base it around its not humanly possible to knock at idle (extremely unlikely) and see how u go.

driving around mid 20s to 30s is ok, its only when it gets up near 40/50/60 that it should become a concern. the powerfc throws the engine check light on when knocking goes past 60 so keep that in mind.

[WogsRus]

yeah the SAFC II does too, i found out when my cas stuffed up, cos i forgot to do up the bolts.

The tune is all good, the tuner had his kncok sensor put on and it showed no knocking or detonation or anything funny.

It just seams strange that if the car has been in the sun and then i turn it on, bang 30 straigh away, within a secon, then drive for 5 monuts, the car still pulls thesame, no differance, and turn off and hay 5.

WFT i mean it's weird.

[WogsRus]

ohh it's never got above 32 i think while driving. Normaly no more the 15 on a hot day, and 5 on a cool day.

[Mr Italy!]

Yeah i have this one happen to me. Was thinking about it lastnight.

When its hot and ive parked in the sun, as soon as i turn the car on it sits on about 30. After driving for a bit in a stinking hot day it'll sit at 40 when im idleing at lights... this has always confused me because theres obviously no audable knock (to the naked ear, my engine would be so far gone by now if there was) and it runs fine.

I've seen it get as high as 50 while idleing, so it makes me think its a butt load of background noise or some sort of interference with the knock sensors for the readout to stay high instead of dropping while idleing...

Edited January 4, 2007 by Mr Italy!

[BAMR33]

How long do you leave it in the sun to when you start it up. I'm thinking if its a shortish period the fuel would be affected by the heat from motor not the sun and the fuel would be in a gaseous expanded state, which would make it run a bit lean for couple seconds untill some fresh fuel is pumped through.

[WogsRus]

well it's in the sun the whole day.

[Mr Italy!]

The problem with that is that the knock level wont go down - it goes a bit down when in gear and im driving, but when i idle again it goes back to the previous idle figure or even higher...

[WogsRus]

well mine goes down allright, all the way to 5 or so. BUT only after i have restarted it after 5 minuts or so.

[Mr Italy!]

well mine goes down allright, all the way to 5 or so. BUT only after i have restarted it after 5 minuts or so.

Yeah mine does that only after a restart - but if you leave it on the first time it stays high.

For example i started mine just then and it was in the sun, started at 27. Let it idle for a while, went up to 29. Turned it off, came back 5 mins later and it started at 20...

[ferni]

No idea about the SAFC, but the PFC has a 'max' value reading and this is sticky - so it won't reset till you turn the car off and back on. So if you have a knock of say 20, then give it some stick, and it hits knock of 30, then the knock reading stays on 30 until you clear it through eh PFC handcontroller or restart the car.

Are you sure the SAFC isn't displaying the MAX value and not the live value?

[Mr Italy!]

^ Yeah the safc has that too, but i know its not set to sticky.

Its random that it wont come down once its hit a level at idle - it goes down while driving but idleing it goes up and stays up....

[WogsRus]

well it look slike we have the same problem. I was going to try the seocn knock wire and see if maybe the knock sensor is funny.

[Mr Italy!]

well it look slike we have the same problem. I was going to try the seocn knock wire and see if maybe the knock sensor is funny.

Yeah it does sound like we've got the same thing going on.

I think i had it connected to the second knock wire for a while but experianced the same sort of thing - but this was ages ago and my memory might be misleading me.