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View Full Version : Knock knock, False knock? LS3 mutant in C5 car LS1 pcm



BHC5
July 1st, 2017, 12:31 AM
Hello members of the board!
Newby novice here. I've recently completed a mutant LS1-2-3-7 motor build and stuffed it into my old turd C5. After learning how important injector data is, I finally have it on the road beginning my journey with tuning. I'm about 80% happy with the VE tables, but I'm seeing Knock Retard when I crack the throttle past 40% around 3000rpm+ downshifting before blasting. Also have some KR when at WOT. I've tamed down the timing tables (so I think) and tried to get HIGH / LOW / BASE Spark all in the ball park so nothing is jumping around.

The car is a C5 using LS1A pcm 24x crank, LS3 block, LS2 TB, recycled LS1 map, recycled LS1 valley type knock sensor on the side of the engine block. I only have one sensor connected right now (the second one was touching a header primary)

Here's my tune and a log. Any insight would be greatly appreciated thank you.

joecar
July 3rd, 2017, 08:15 AM
You log shows that it might not be real knock... but maybe something hit (exhaust on chassis...?)



BTW: smooth your VE table (it can't interpolate easily like you have it).

BHC5
July 3rd, 2017, 09:52 AM
Thanks for your reply Joecar. I will get to smoothing. :thankyou2:

BHC5
July 4th, 2017, 12:32 AM
maybe something hit (exhaust on chassis...?) DING!!! Second opinions Rock... :rockon: I'm running those silly DynoMax VT mufflers with the flappers inside them... I bet they're causing the KR I'm seeing. Thanks again Joecar.

joecar
July 4th, 2017, 11:41 AM
Do you have a Chassis Ear (or some other listening phone)...?

BHC5
July 4th, 2017, 01:29 PM
I do not. Where might I find something like that? If not too crazy $ I could purchase one.

joecar
July 5th, 2017, 03:31 AM
ebay

The non-wireless ones are about $100. The wireless ones are about $200.

Depends on how intense you are with your car, the Chassis Ear comes in useful when trying to locate the source of any kind of noise (of course, I sometimes still fail).

BHC5
July 6th, 2017, 02:20 AM
Did a little test. I wired the flappers in the mufflers to be open all the time. Went out for a test log, and Success!!! :banana: I had full timing until my riggings got hot and one side closed/got loose on me. LOL So now I know why Dynomax has discontinued those VT mufflers... The flappers may cause Knock Retard.

I found a ChassisEar for $108 on a tool website, (not sure if I'm supposed to suppress other sites?) Tool topia. Looks like something I could use. Thanks again Joecar for the help. :good:

joecar
July 6th, 2017, 08:14 AM
Good job :cheers: :cheers:

( you can mention other sites, if there's a problem I have the ability to sanitize )


I use the non-wireless ChassisEar for suspension squeaks/rattles, noisy wheel bearings, and other things.