john banks

My ECU not picking up detonation seems to coincide with fitting a manifold. The Bosch sensor does pick it up but it two wire. Can I just ground one and use the other? I know it responds to a wider frequency range and this may help.

dowser

Interesting John, I was also wondering whether I'd damaged my factory sensor somehow when fitting the manifold

Where is the factory item? Best is to measure both for impedance - if similar, give it a try.

Richard

john banks

I was in a rush before a track day, so just grounded one of the Bosch wires and used the other, but still left the Knocklink attached. No joy, and the signal to the knocklink was attenuated. The factory knock senor is under the return from the dump valve and pretty awkward to get to even with the IC off.

Mervyn reckons that the frequency of knock can be different after a manifold. Oddly after the manifold went on it was still sporadically taking a token bit of timing away, but really doesn't seem to work at all now

Track day was OK - even with plenty of heatsoak didn't detonate once - I must have the timing about right then, but I would rather have the knock sensor active.

I'll check all the loom and resistances etc, but it seems like the Subaru knock sensor just doesn't work with some manifolds is my best guess now - not that manifolds necessarily just take away all your knock!

ustolemyname??stevieturbo

iTrader: (1)

John, If you are reprogramming the ecu, how about just doing away with the knock sensor? People like motec dont seem to think them reliable enough, and hence dont use them on their ecus. You just map the car accordingly, and that way dont get any false retardation. You would still use it for the knock link, and have a visual indication to see whats happening.

john banks

I suppose so Steve, but I can run more advance for more of the time if I have it running reliably on knock correction. The map I had running 21 (10 static + 11) at 4000 up to 28 (10 + 18) a high revs, with 1.3 bar and 8% CO worked really well on track with no active knock sensor I have to say. Have to say in support of running without that it can retard for no apparent reason sometimes.

pat

Stevieturbo,

*reliable* knock detection is quite difficult, in many cases you may be pulling timing out when there really isn't any det at all. I've seen this a few times on Scoobies... now if this were the case on a race engine and it ended up losing you a few hundredths of a second per mile, and you ended up dropping from 1st to second place for no good reason you'de be somewhat annoyed. Also, bear in mind that races are generally run on controlled quality fuel, so that no single comeptitor / team has any advantage over the others on the basis of the fuel that they are using. Given these conditions, a race engine management system such as the MoTeC does not need to run closed loop knock control. The dyno map should be pretty damn close and no "duff tank" problems should cause det.

If we start looking higher up the price range we find that knock control returns. For example the Pectel T10S has no less than ten knock channels; they employ digital signal processors to accurately detect knock; but let's not forget here that the T10S is *TEN* times as accurate as the MoTeC, and of course it will control your active transmission etc

FWIW, the latest generation Pectel T6 has now got "rudimentary" knock control built in. The older T6 had optional knock control via mezzannine DSP board but demand was low due to the additional UKP 1500 price tag and the aforementioned stuff about race fuel etc. I will be testing the new knock control features when I fit my new T6, I'm expecting it to be better than stock and Link knock control but not a patch on the old T6 optional control or the T10S... at least it will identify which cylinder is detting and will pull timing away from the offending one rather than across the board

Cheers,

Pat.

JIM THEO

Just to mention that after my new style PE manifold (MY00/PPP) I had a small amount of knock correction (-1) while before with only the PPP I had sometimes too much knock (-4) and RED lights two times on knocklink.
After a Magex downpipe no knock correction at all, even with 40 degrees ambient temp and even on fast starts at traffic lights!
My knocklink doesn’t light now (it is under the IC and near the factory sensor) except the first green so must be something else wrong with the manifolds and the OEM knock sensors!
Should I worry why my car runs so "safe" now compared with the past?
JIM

john banks

I believe the PE manifold is OK with the knock sensor. Even if it wasn't if your knocklink is working (ie a few greens at high revs) and not showing detonation then you should be OK.

BTW the Bosch sensor triggers a CEL. My OEM sensor and loom and ECU are all ok, but it doesn't respond to knock.

[Edited by john banks - 8/18/2002 3:21:56 PM]

tweenierob

Anyone know where i can buy a bosch knocklink sensor from, mine has been over tightened and i would like to replace it...
Rob


[Edited by tweenierob - 8/18/2002 11:23:47 PM]

tweenierob

BTTT

john banks

BRD, Scoobymania. Or ask someone the part number of the Bosch sensor not me it is on my block and I am not removing it again.

Sam Elassar

john

you shouldn't not rely on the knocksensor or knock retardation. it is just as an extra percaution, isn't it.

did you try det cans to see if your car is actually knocking and it is not just some other noises that the knocklink is picking up?


sam

tweenierob

Cheers John
Rob

john banks

Sam you can hear it is det - it got a lot hotter outside and was a lot more obvious - (that is why I got the Knocklink) - I couldn't get the stethoscope acoustically coupled to the block adequately for it to be useful. It gets worse with heatsoak and disappears when you retard the ignition. It also first appears at 5000 RPM. Only ever on full load. Reducing the boost also abolishes it.

The JECS ECUs do rely on the knock sensor as the car arrives originally - I have seen them actively adjust very nicely - when they work - which seems to be invariably the case on a standard car. Otherwise a heck of a lot of STis/P1s would blow up, as well as PPPs, and standard cars run on NUL. I am happy to trust it if I know it is working - rather have some decent timing and go out on track and if it heatsoaks it will do something about it. Tricky to map it on the road or rolling road with timing you know will cope with the track.

[Edited by john banks - 8/19/2002 8:51:02 AM]