davefaedeen

hi guys how can i check the engine faults coes with a FC commander ?? my car is getting high knock levels and i think it may be due to the old knock sensor!!!

my95 sti with new v7 bottom end.

prodriverules

iTrader: (52)

How high is your knock going mate?and when is it occuring?

davefaedeen

Hi its at higher revs even on low boost AF told me to check if anything was loose in the engine but nothing is!! its getting mapped by him again in january, the car has been off the road of a year i just serviced it new fuel filter oil feul etc... here is a pic from the FC commander,

Ian

iTrader: (10)

when i wanted to read mine, i drove to the garage, pluged the standard ecu in, read codes, then re fitted the apexi

job done

Ian

iTrader: (10)

bad batch of fuel?

prodriverules

iTrader: (52)

54 is getting up there abit,could be as daone said bad fuel but could also be something else,does it feel different when it happens like a small misfire or anything as it could be plugs or coil pack problem.

davefaedeen

i have ran 2 diff tanks of 99 through the car, i mite give optimax a go next time to see if that makes any diff, the previous owner had the car mapped to optimax by AF but my local garage is tesco, they are both 99 octane fuels so i dont think fuel is the problem?? the check engine light has come on 3 times due to the high knock level so now am driving it round like a shopping car set to the lowest boost arrrggghhh help!!! daone i dont have the old ecu am afraid gutted!!!

davefaedeen

no problems when it happens, just me lifting my foot off the peddel like a bat out of hell when the engine light comes on !!!

davefaedeen

any ideas gents????

davefaedeen

bump

bruce

iTrader: (5)

Were the heads skimmed when fitted to the new bottom end? could be a slightly raised compression ratio causing this. That happened on my old 2 litre engine after head gasket change with a head skim. Needed to get the map adjusted.

SCOOBYLADVA

Hi mate,

You cant check on the PFC commander iirc.

Jolly Green Monster

iTrader: (4)

Is it mapped for the new bottom end?

Compression will be altered by pistons, gaskets etc

davefaedeen

Thanks for the posts guys am just waiting to hear back from the previous owner weather the map was carried out post or pre v7 bottom end install

davefaedeen

Ok so i contacted the last onwer and it was mapped by AF after the rebuild the heads were also polished during the rebuild, so that cant be it??? do you think the knock sensor is faulty?? as its prob the original from way back in 95? am totally stumped surely the engine isnt actually knocking???

Splitpin

It is impossible for me to answer your question with 100% authority as I don't know how the Apexi knock detection circuitry/detection algorithm is actually designed. The Subaru OE ECU knock detection system, for example, is a bit primitive and can sometimes get confused by high levels of transmission or road noise, triggering "false" knock correction. If the Apexi ECU works in a similar way, it may be getting similarly confused.

However, as a general point, if your knock sensor was faulty, it would be more likely to under-read rather than the reverse.

This being the case, the problem you have is that while you can assume that the engine "isn't actually knocking", you don't know. The pecautionary principle applies here. It is better to assume the worst, and prove the suspicion wrong, than assume it's a false positive and find in a couple of months' time, after it blows up, that the ECU was giving you a genuine report.

Fitting a new knock sensor on an elective basis might be an interesting, low cost next diagnostic step. Another way forward would be to contact Andy (or a conveniently located reputable tuner) and ask them to have a quick listen with some det cans. Or maybe fit a Phormula KS3/4 system and see what that has to say.

davefaedeen

splitpin thanks for your reply, i will order a new knock sensor and also see if i can get someone to look at the car with some det cans to see whats up. i have a feeling it could be down to noise, eg the induction kit or the old gearbox, but like you say its better to be sure. as it stands the car is being driven off boost untill i get a true cause for the high reading! it could also be due to the new ARC TMIC the previous owner fitted before sale??! my next question is what knock sensor do i need?? as when googled 3 diff types come up.

Splitpin

The knock sensor is basically just a piezoelectric microphone. It sends pretty much all the noise the engine/transmission/car is making in the the ECU, and from there it's a combination of a bit of analog filtering plus some software before the ECU has to decide what is random noise and what is knock. Like I say the Subaru control units can often guess wrong (they can sometimes miss legit knock too, unfortunately) so you're doing exactly the right thing in keeping your foot off until you're sure.

Everything's possible. Only one way to be certain.

Correct replacement is the 22060AA031 type. Available here. When you fit it, make sure you get the tightening torque correct - as too loose, they don't read properly, too tight, you can crack the body and give it an early death. I usually fit a slightly modified bolt that can't contact the plastic part of the body, which removes the breakage risk.

WUZ

iTrader: (14)

If it doesn't cure the problem, I'm back in Aberdeen on the 10th and could easily pop round with the Detcans and have a listen?

Russell

davefaedeen

Hi Splitpin thanks for your reply i will order a new knock sensor and see if that cures the problem. hopefully we can get to the bottom of this!! Russel I will be back on the 19dec.. will you still be in aberdeen around this time>>> as I would like to take you up on your offer!!!

cheers again