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Knocklink - False alert ?

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Hi everybody,

I recently bought an G4 Knockling with a bosch donut knock sensor 0261231110 and an homemade loom (0.35mm² wiring with shield) on my new engine.

I have regulary red flashings alert at 3500rpm 0.5bar of boost (not full throttle) and randomly between 4000 at  5000rpm at 1.15bar (low boost) and the same thing on high boost (1.5bar), sometimes no flash.
I tried to replace the sensor, first it was on the top near the 4th piston, and after, it was on the down beetween 3rd and 4th piston at the genuine sensor place) but still flashing at theses Rpm.

After that, I tried to reduce the ignition timing (see the map before/after) but still the same... I'll try with much less timing again.

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Does my engine is very noisy (forged, bigger camshaft with crossing, bigger turbo, uprated engine mount...) or is it real knock (I haven't try to ear, I don't have the material and the experience to).
Had you ever this problem?

my car is a Ford Sierra cosworth 4x4 (4cyl 16v turbo)

Thanks for your help

 

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The Cosworth uses a very short con rod and creates a lot of piston slap, even though the later engine ran a lot more gudgeon pin offset it still creates false knock, most of this dissapears as soon as you move to a 136mm rod and WRC style pistons. 

Now I know that does not help you but at least you can understand why you are getting false knock.

The KnockLink is a great tool for tuning, it will show knock but unfortunately will also show false knocks, exactly what the YB engine is known for. BUT its a great tuning tool because you can see both then work out exactly like you have done by reducing the timing and see if its real knock or false knock.

If you have one of the higher end ECU's things get easier still, with the internal knock control you can introduce knock windowing which illuminates 90% of false knock by only listening to it during the period knock is most likely to happen, you can also then work out which cylinder is knocking and trim them individually.

One more thing, as long as you have not gone above the standard 8:1 compression your engine will not be knock limited, in that you will hit maximum torque before you get knock by 4-8 degrees, so I do not advise people tune these to knock and back off but tune to peak torque.

Hope that helps explain what it going on.

Clint

 

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Thanks Clint for this answer.

I forget to mentionned it, but now I'm near 8.3:1 compression.

so the Knocklink won't be usefull on a tuned YB...
But does a Knockblock with headphones could hear knock on a noisy Yb?

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What fuel are you running ?

Yes the k]Knockblock and headphones will hear everything knock and false knock, but once you get used to it you will be able to tell what is what, imagine if like your light but with audio ;)

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I'm on  SP98 (Ron 98) but I also use a BD15 inlet cam with BD8 exhaust, timed at 105°-110° (which increase knock risk) and a GT3071r, so I need to find a good way to hear real knock to correctly adjust ignition.

Thanks for all yours answers

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I would retime them cars to 110/112 will increase the torque spread the 15 is more like a rally cam than a race cam so phasing it out of its operating area is not a good idea.

you need to get on a dyno to tune your car, and be very careful around peak torque 4500 rpm I would imagine.

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