Ive only had my Impreza a couple of weeks and i'm not too familiar with the knock readings im getting on my fc commander.
I was led to believe that a reading of over 25 was bad,well ive just been out in my car and im getting readings of upto 75 but that wasn't even on boost !

What sort of reading is deemed as unsafe and why would I be getting such high readings when im not even on boost ?

Quick spec:
Hybrid fmic
550cc injectors
Apexi Power fc and commander
Apexi boost controller
GenII ceramic coated heaters and up-pipe
Hayward&Scott full system

 

hi there
not sure what the readings should be but mine is between 12 to 30 and i can only get a reading of over 50 when i hit the rev limiter,hope this helps

 

Could be a whole host of things but 75 is very high.

A quick check would be to set the FC commander to Knock then press the enter button again to get the graph up rather then the digital display.

Go for a drive and see if the knock is a very sudden spike on the trace or if it is a gradual increase with RPM.

If it is a spike I would advise you get a tuner to check it with detcans to see if it is really knocking.

If it's a gradual increase, chances are somethig else is causing it i.e loose knock sensor or something rattling near to the knock sensor.

 

75 is way too high, especially if you're not thrashing it. Drive very carefully indeed and get a engine mapper to investigate the problem.

A well setup engine will give knock count less than 20.

If you are far away from a mapper, see if they will travel to you.

There are too many causes to list and without knowing certain facts, let an expert check over the setup and mapping of the apexi.

 

Im really not sure why my reading is so high then

 

Apparently paul @ Zen performance mapped my car for optimax+octane booster. Im just running it on V-power at the moment,would that cause this problem even driving it slowly ?

 

Powerstation are at Tewksbury

edit yes, possibly. Turn down the boost setting to the lowest, this is usually 0.6 bar. Contact Paul, as he will have you mapping details on his pc

 

Cheers mate,I know the guys @ Powerstation well. Might have to pop down and have a word with them then.

 

Yes that could cause the problem.. you need to run it with booster if it was mapped with booster..

Simon

 

Cheers,ill give that a try and see if it improves things. Also,I was under the impression that the cel light would illuminate if the knock reading was too high but it didn't ??

 

mine is mapped at zen and i run it on v power and tesco99 and there is no change in the setting

 

Just read aswell that a '96 on Impreza needs to be run on booster,well mines a '96 so could that be part of the problem also ??

 

it needs to run on the fuel or equivalent RON rating as it was mapped on..

Simon

 

Ok mate,ill put some booster in with the V-power and see what effect that has. It runs 1.4 bar so I dont want to run it on the incorrect fuel

 

My car is due to go to Zen performance tomorrow for the knock levels to be investigated but I wanted to ask you guys for some more advice before that.

Been out in the car today and set the fc commander to monitor just knock on the graph mode.

Flat out on 1.0,1.2 and 1.4 bar boost im not getting much activity,around 10-15 ish peak figures.

The worst I had was at around 3500rpm in 3rd just holding the throttle at that point.Loads of activity with peak figures around 50-60 !

Is this a sign of something wrong or am I reading the figures wrong ??

 

Anyone got any ideas ?

 

Sounds like it's fine when it's under real load but not in the midrange.
Probably just a bit of timing needs pulling in the middle of the map somewhere.

I could tell you how to do it using the monitor mode, but I think it's best for you to take it to Paul @ Zen.

 

Its booked in with paul tomorrow at 1.30pm so ill see what he thinks

 

Just got back from Zen performance. What can I say,Paul is a very helpful and pleasant chap.

He said there is no det with the car at all,the peak knock readings are basically false. He couldn't tell me exactly what is the cause of this but said to change the knock sensor and see what happens.

He changed a few settings in the map but said that the car is fine so I can stop worrying about the knock readings for the moment

Anyone else experienced something like this ?

 

I had a knock of 49 today, when going down the motorway for about 1-2 sec, i tryed to drive the same but nothing else, so am putting it down to something hitting the engine or something, the peek boost was 1.3 bar so nothing strange there, so prob just one of them things

 

If your 49 was a sudden spike out the blue when you were on boost, it probably was knock. If it keeps happening get it checked.

 

yes it was, 4th gear on motorway, over taking a lorry, had a PFC fitted and mapped about 2-3 weeks ago now, the only difference was that i had my bung in the exhaust today, where i normally dont, would this may of caused it?

 

Yes. Take the bung out or adjust the map to suit.

 

Im going to replace my knock sensor after what paul@Zen told me today. Do I need to get a genuine subaru sensor or can I replace it with a bosch one like the one used for fitting a knock-link/detalarm ??

 

Anyone ???

 

no I believe the plug is different..

 

Ok cheers.

 

Any news on this? Did the change of the knock sensor do the trick? Cos I've had nearly the same problem for ages.

 

Changing the sensor made no difference ! Mine still gives high readings every now and again and the check engine light flashes but im assured its a false reading.

Im thinking about getting a knocklink or Detalarm and see what happens with that.

 

I get this too. However mine seems to do it when slowing down.

Spoke to Paul who advised that as long as its not doing it on load its fine, and quite common for my age of car (V4 Type R)

Its when it does it under full load you need to worry.