Reading Dyno Sheets
Started by
_Unidentified_
, May 31 2006 04:39 PM
7 replies to this topic
#1
_Yella SLuR_
_Yella SLuR_
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Posted 31 May 2006 - 04:39 PM
Just be interested to know what the dyno print-out curves tell you about how an engine is running. Of particular concern are the ridges and bumps. I can sort out the AFR no worries. I will get serious about it one day Andrew if your offer still stands, still housing though.
#2
_Yella SLuR_
_Yella SLuR_
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Posted 31 May 2006 - 04:41 PM
Is the object to get a smooth curve without the little ups and downs, or big ups and downs?
#3
_[2_FLY]_
_[2_FLY]_
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Posted 31 May 2006 - 05:32 PM
There is a bit of a hesitation at the start of the curve (around the 88km/h mark).Mine used to do that was a powervalve problem.
Looks like and ignition breakdown right up the top too. Your afrs start pretty good but are getting a touch rich at the top end. Ideally you want to keep them in the mid-low 12s
Looks like and ignition breakdown right up the top too. Your afrs start pretty good but are getting a touch rich at the top end. Ideally you want to keep them in the mid-low 12s
#4
Struggler
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- Name:Andrew or AJ
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Posted 31 May 2006 - 08:46 PM
Hi Pat, sorry I haven't been here for a couple of days.
I wouldn't worry about the jaggered looking curves. When the ramp starts the engine is in a state of transition and it takes a sec. or 2 to sort itself out. It does go progressively lean in the top end though, this could be fixed with a air flap and/or needle hanger adjustment. I would really want to see the whole AFR dropped to mid, low 12s for safe max power. The dip in power at the end could be due to the operator getting off the pedal, or something else, possibly valve springs.
Let me know if you want some dyno time, I like playing with the old Q jets.
I would say this is caused by the air flap opening too quick as evidenced by the lean condition, but would warrant further investigation.
13 :1 is actually lean.
An ignition miss will show up in the AFR as a rich spot, as fuel is passing through the engine without being burnt. No evidence of that here.
I wouldn't worry about the jaggered looking curves. When the ramp starts the engine is in a state of transition and it takes a sec. or 2 to sort itself out. It does go progressively lean in the top end though, this could be fixed with a air flap and/or needle hanger adjustment. I would really want to see the whole AFR dropped to mid, low 12s for safe max power. The dip in power at the end could be due to the operator getting off the pedal, or something else, possibly valve springs.
Let me know if you want some dyno time, I like playing with the old Q jets.
There is a bit of a hesitation at the start of the curve (around the 88km/h mark).Mine used to do that was a powervalve problem.
I would say this is caused by the air flap opening too quick as evidenced by the lean condition, but would warrant further investigation.
Your afrs start pretty good but are getting a touch rich at the top end. Ideally you want to keep them in the mid-low 12s
13 :1 is actually lean.
Looks like and ignition breakdown right up the top too.
An ignition miss will show up in the AFR as a rich spot, as fuel is passing through the engine without being burnt. No evidence of that here.
#5
_Yella SLuR_
_Yella SLuR_
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Posted 31 May 2006 - 09:23 PM
Yeah, too lean. 13 parts air to one part fuel, really want 12 parts air to one part fuel. I'm wondering if the VR fuel filter is too restrictive as well.
I promise you we will play at some time Andrew, just don't ask me when at this stage. Poor ole car hasn't got much of a look in of late.
I promise you we will play at some time Andrew, just don't ask me when at this stage. Poor ole car hasn't got much of a look in of late.
#6
_Oldn64_
_Oldn64_
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Posted 31 May 2006 - 10:52 PM
Hey Pat,
What needles (secondaries) and hanger are you running?
Cheers
What needles (secondaries) and hanger are you running?
Cheers
#7
_devilsadvocate_
_devilsadvocate_
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Posted 01 June 2006 - 07:54 AM
Its just as important to get afr right at cruise(light/moderate throttle) right through the rev range as well,
#8
_Yella SLuR_
_Yella SLuR_
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Posted 01 June 2006 - 08:10 AM
Oldn, I don't know mate. But it's been to the specialist carbie dude, and he reckons they are right. It doesn't idle well when cold, which is showing up on the dyno as ultra-lean, making me think clogged or too restrictive fuel filter.
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