Knock during dyno

[streetsweepergto]

I had my vehicle on the dyno recently

I had a pull where the knock retard went crazy
Even though previously backing down the timing in that area.

I let off , back to idle for a few seconds and proceded with the pull again.
Only this time I ended up with .1 value in 1 cell.

This happened 2-3 times.

Each time It happened was after I shut the vehicle down to flash and make fuel corrections.

The last pull ended in 502 rwhp and 451 rwtq.

It's a ls2 by the way.

Is it possible that I was having false knock?

It's a hci ls2 m6 gto

If have logs to show if anyone is interested.

[C6Z_sd]

Anything's possible. Post a scan and tune.

[righton]

Has your IAT Spark Correction -Add table been altered? If so, check your IATs in your log. You IATs could be very high after sitting resulting in knock, if timing is not pulled.

[4evervette]

happed to me as well few times ..try to duplicate that in the street and nothing happend the cars runs great then come back to the dyno and it start knocking like crazy ..

btw what type of dyno u had this ( mine was mutsang dyno )

[streetsweepergto]

was a mustang dyno

here are the 2 logs
for the last 2 pulls.

pull before last and last pull have same exact tune.
made the pull first it started to knock, backed out of it.
then went at it again. got 0 knock.

weird

checked my iat tables
they only start pulling timing until iat gets over 104F
my iats never went over 95 f.
but does the pcm say screw it and pull timing a couple degrees earlier?

[8850]

Looks a little lean where you are showing KR. My 08 likes about a 12.4 AFR. However I have a stock cam. Would try richer at WOT.

[righton]

I believe the PCM will pull timing in the midway area of the previous column (95 degrees) to column (104 degrees). But since you are in between columns 86 and 95 I doubt any timing is being pulled due to IATs. Anyway, looks like you have knock, not just timing being pulled.

I had experienced knock on the dyno due to no dyno fan turned on, but my IATs were over 100F.

I'm H/C/I LS2 too, small cam and run AFRS from 12.3 peak torque to 12.6 peak power.

I like how you don't use one flat AFR.


btw, are your heads milled or are you running a thinner gasket?

[streetsweepergto]

62 cc chamber etp 215 3.900 bore heads.
with stock ls2 head gaskets.

should be around 11.25-11.5 to 1 compression.

it could be a few things that could of been causing it.

1- i run the ngk preset for my ngk afx wideband
2- up 10 percent ethanol in the fuel but my stoich is still set at 14.69971
3- too much compression for what ever quality fuel im currently getting.
using 93 octane but who the hell knows what it is.

the point is, btw the 2 logs 1 of them with the same exact tune knocked and the other did not.

so is this normal, can one expect knock to be dynamic or consistent?

i know my ve table for pe is dialed in perfectly.
im sure if i shift the wot table to be richer it will command it with less then a 3 percent error.
have not made any wot logged pull on the street, car is too loud and too violent to do it without being noticed or drawing attention.

wish i had more dyno time, im to inquisitive to just forget it.