Understanding timing?
Thread Starter
Le Mans Master
Joined: Jan 2009
Posts: 5,656
Likes: 112
From: ocean springs mississippi
Understanding timing?
05,A&A ti trim blower,alky meth,LT'S,z06 bimode exhaust....using dashlogic .
Watching timing while driving yesterday.
High gear/low rpm= 50-60*
Lower gear/high rpm=10-18*
Just trying to understand what I need to be looking for or concerned about?
Watching timing while driving yesterday.
High gear/low rpm= 50-60*
Lower gear/high rpm=10-18*
Just trying to understand what I need to be looking for or concerned about?
Race Director
Joined: May 2004
Posts: 16,667
Likes: 1,209
From: Raleigh, NC
St. Jude Donor '15
The low RPM #'s seem high to me
I usually see around 13-14* towards the top end so that sounds about right
Keep an eye on knock retard
is it the stock cam?
The basic idea is you want peak cylinder pressure to happen about 15* after top dead center.. At WOT there's a lot of air/fuel in the cylinder so the explosion (flame travel speed) will happen faster. Thus, you want to delay ignition so that you still end up with peak cylinder pressure closer to (or after) 15*
At light throttle there's not very much fuel/air in the cylinder so you have to start the process sooner as the flame front will travel much more slowly. Thus the high numbers at part throttle stuff.
I assume you don't have HP Tuners?
I usually see around 13-14* towards the top end so that sounds about right
Keep an eye on knock retard
is it the stock cam?
The basic idea is you want peak cylinder pressure to happen about 15* after top dead center.. At WOT there's a lot of air/fuel in the cylinder so the explosion (flame travel speed) will happen faster. Thus, you want to delay ignition so that you still end up with peak cylinder pressure closer to (or after) 15*
At light throttle there's not very much fuel/air in the cylinder so you have to start the process sooner as the flame front will travel much more slowly. Thus the high numbers at part throttle stuff.
I assume you don't have HP Tuners?
Thread Starter
Le Mans Master
Joined: Jan 2009
Posts: 5,656
Likes: 112
From: ocean springs mississippi
The low RPM #'s seem high to me
I usually see around 13-14* towards the top end so that sounds about right
Keep an eye on knock retard
is it the stock cam?
The basic idea is you want peak cylinder pressure to happen about 15* after top dead center.. At WOT there's a lot of air/fuel in the cylinder so the explosion (flame travel speed) will happen faster. Thus, you want to delay ignition so that you still end up with peak cylinder pressure closer to (or after) 15*
At light throttle there's not very much fuel/air in the cylinder so you have to start the process sooner as the flame front will travel much more slowly. Thus the high numbers at part throttle stuff.
I assume you don't have HP Tuners?
I usually see around 13-14* towards the top end so that sounds about right
Keep an eye on knock retard
is it the stock cam?
The basic idea is you want peak cylinder pressure to happen about 15* after top dead center.. At WOT there's a lot of air/fuel in the cylinder so the explosion (flame travel speed) will happen faster. Thus, you want to delay ignition so that you still end up with peak cylinder pressure closer to (or after) 15*
At light throttle there's not very much fuel/air in the cylinder so you have to start the process sooner as the flame front will travel much more slowly. Thus the high numbers at part throttle stuff.
I assume you don't have HP Tuners?
Race Director
Joined: May 2004
Posts: 16,667
Likes: 1,209
From: Raleigh, NC
St. Jude Donor '15
Probably a bit too much timing down low but not a huge deal IMO. I see the same sometimes if I jam the throttle real quick down low. The knock sensors are quite sensitive. When my power steering pump was going out it was loud enough to set them off like crazy
Here's a video on knock/detonation that I really liked:
Here's a video on knock/detonation that I really liked:
Last edited by schpenxel; Oct 19, 2015 at 09:57 AM.
Thread Starter
Le Mans Master
Joined: Jan 2009
Posts: 5,656
Likes: 112
From: ocean springs mississippi
Probably a bit too much timing down low but not a huge deal IMO. I see the same sometimes if I jam the throttle real quick down low. The knock sensors are quite sensitive. When my power steering pump was going out it was loud enough to set them off like crazy
Here's a video on knock/detonation that I really liked:
https://www.youtube.com/watch?v=WuCUGcqO5SE
Here's a video on knock/detonation that I really liked:
https://www.youtube.com/watch?v=WuCUGcqO5SE
