Need help understanding the cause of knock
Thread Starter
|
Cruiser
Joined: May 2008
Posts: 117
Likes: 3
From: Milwaukie Oregon
Need help understanding the cause of knock
I have been working on a tune on my 103 and have been plagued with engine knock. Not that I can hear but is detected by the master tune software. Motor runs strong but under high loads I will see the timing go away as low as 13 degrees with a retard fast of 8 additional degrees at 100% throttle at 5800 rpm My injecter pulse width as high as 19 ms and injector duty cycle as high as 95% and the o2 sensors pegged rich. I am running a 103 cid motor woods tw6hg cams stock valve size black diamond valves Compression ratio 10.1 to 1. a SE 50mm throttle body with 4.78g/sec injectors flat top forged pistons. Have any of you run into this. Is it as simple as wrong spark plugs or hot spots on the head. There is minimal carbon on the pistons and what I see with a bore scope looks like a dry lake bed.
Cruiser
Joined: Feb 2008
Posts: 114
Likes: 0
From: Southern Indiana. (Louisville KY Metro Area)
What kind (brand) of wires? Spark Plugs?
Though usually, knock is due to fuel and/or timing.
What AFR are you seeing at this knock area?
4.78's with 19ms would seem rich enough though...but all builds are different.
If enough fuel...take out some timing in the knock area and try.
BTW.."...o2 sensors pegged rich" Elaborate?
Curious, what year bike too?
Though usually, knock is due to fuel and/or timing.
What AFR are you seeing at this knock area?
4.78's with 19ms would seem rich enough though...but all builds are different.
If enough fuel...take out some timing in the knock area and try.
BTW.."...o2 sensors pegged rich" Elaborate?
Curious, what year bike too?
Outstanding HDF Member
Joined: May 2007
Posts: 2,304
Likes: 31
From: Florida
I have been working on a tune on my 103 and have been plagued with engine knock. Not that I can hear but is detected by the master tune software. Motor runs strong but under high loads I will see the timing go away as low as 13 degrees with a retard fast of 8 additional degrees at 100% throttle at 5800 rpm My injecter pulse width as high as 19 ms and injector duty cycle as high as 95% and the o2 sensors pegged rich. I am running a 103 cid motor woods tw6hg cams stock valve size black diamond valves Compression ratio 10.1 to 1. a SE 50mm throttle body with 4.78g/sec injectors flat top forged pistons. Have any of you run into this. Is it as simple as wrong spark plugs or hot spots on the head. There is minimal carbon on the pistons and what I see with a bore scope looks like a dry lake bed.
Looks like your getting plenty of fuel....I'd look at a TW6 cam for your build and a better throttle body. Dan Basiley is boring out the stock TB to a 50mm for $375.00 that will out perform the SE 50 mm TB.
If I where to give you an educated guess on your abnormal combustion (detonation) at top end I would have to say it is "After Gas" ....fuel unburned from poor combustion on the stroke before and detonating on the next compression stroke. Again the TW6H cam wants more compression than the 10.1 you are running and it wants to breathe better that what the stock valves will allow and this can contribute to the poor combustion in your engine.
The only other thing I would mention is if the VE tables are off so is the tune....the VE Tables HAVE to be correct for the bike to run correct so this is the root of the tune .If the VE Tables are right on (which I don't think they are because your injector is at the point that it is open all the time at 5800 rpm with a large injsctor and that doesn't make sinse in your build) again if the VE Tables are right on then look at the components selected for you build.
Just a couple of thoughts.
Doc
Last edited by Doc 1; Nov 28, 2008 at 11:17 AM.
Thread
Thread Starter
Forum
Replies
Last Post
The Northern Bum
Touring Models
17
Jul 19, 2012 09:37 AM
