knocksense question

[kildea]

ok, so i have knocksense, and it's great and stuff but ....

when i hit the wastegate boost limit/level my knocksense registers knock.
the wastegate spring should limit boost to 160kpa, this is where the knocking begins.
the actual pressure levels off at closer to ~170kpa.

it's an external wg, mounted to the header, and i figured the fluttering of the valve is maybe just the right sound to be heard as knock (by the sensors) ... but i don't want to ignore the knock only to find out that it was in fact actual knocking after the engine is toast.
my afr's are in the 12's and lower in this range (not really tuned all that well yet, but i figured safer to be rich) so i don't think it would be lean pinging, and adjusting the advance does not seem to do anything about the onset of knock sensing at 160kpa (it's literally exactly at 160 kpa, and this is on two different megasquirt boxes, so i don't think it's megasquirt related unless it's some sort of noise issue in the wiring).

so does anyone have a suggestion? maybe there is another variable i should be looking at to determine if this is likely to be real pinging?
maybe install a manual boost controller and crank up the boost, see if the pinging threshold bumps up a bit in the pressure range?

[Karl Buchka]

Disconnect the waste gate and drive it... very carefully.

[linuxman51]

that, or pull timing out and see if it still does it (not like 1 degree, pull like 8 degrees)

[Karl Buchka]

that, or pull timing out and see if it still does it (not like 1 degree, pull like 8 degrees)

I've looked at the spark map he's running and where the 'ping' is occurring there's only like 16 degrees of advance. It doesn't seem logical for it to be pinging with 16 degrees of timing and at 160kpa. This on 93 octane and the compression ratio is high 8's I think.

[The Aspirator]

Pull timing like Kenny said or squeeze back the adjustment knob on the knocksense. You've got it fed back into MS for datalogging?

[kildea]

Pull timing like Kenny said or squeeze back the adjustment knob on the knocksense. You've got it fed back into MS for datalogging?

yeah i do.

i disconnected the vacuum to the wastegate and the ping level resumed at 170kpa.
so i think it has something to do with that wastegate openning.

i'll get a datalog this week and post it if people are interested, and i'll tinker with the knocksense nob a bit.

[lclark96]

keep us posted, ill be adding knocksenseMS soon on mine as well

[crazy0000]

FWIW, the sound of pulling my car out of reverse(you know the noise it makes) is the Perfect knock sound. It sets the light off everytime. and also my light goes off above 4500RPM and I'm scared to turn the adjustment any further as I don't think it will detect knock.

[Boris740]

FWIW, the sound of pulling my car out of reverse(you know the noise it makes) is the Perfect knock sound. It sets the light off everytime. and also my light goes off above 4500RPM and I'm scared to turn the adjustment any further as I don't think it will detect knock.

I suspect that the threshold is to low. The adjustment can be subject to empirical judgment. There are twoways which can be used alone or in combination.

One is to advance the timing until you hear it knocking under the mild load.
Other is to put small quantity of low octane gas in nearly empty tank and
induce it to knock that way. In either case it should not take much of a
load under these conditions for knock to occur. At this point you adjust the threshold
potentiometer inside the Knocksense/MS so that the LED flashes with knock.