HP loss from 29degrees to 23?
HP loss from 29degrees to 23? Guys, whats the rough average of HP lost with every degree to timing the PCM pulls with KR??
Im still seeing 2.5-3.5KR everytime my car goes WOT
Timing goes from 29 down to 23 usually
i tried pulling a few degrees of timing at WOT, but I still see the same KR. False knock??? I cant hear any knock from inside the car at WOT...
Im still seeing 2.5-3.5KR everytime my car goes WOT
Timing goes from 29 down to 23 usuallyi tried pulling a few degrees of timing at WOT, but I still see the same KR. False knock??? I cant hear any knock from inside the car at WOT...
Re: HP loss from 29degrees to 23? Probably around 5-10 HP.
It is starting to sound like false KR. If you have already pulled timing, and you are still getting the same amount of KR, then most likely it is false KR.
It is starting to sound like false KR. If you have already pulled timing, and you are still getting the same amount of KR, then most likely it is false KR.
Re: HP loss from 29degrees to 23? Oddly enough my car experienced kr on the dyno and it was audible. Still, the more timing I added, the more rear wheel torque and hp my car made. 
I had the timing backed down to 20º at first then added 5º of timing and saw an average of 11 rwhp and torque.........kr and all. Here in Kalifornia we only have 91 Octane pump gas and add 100º+ temps, you get kr aplenty. Still my engine makes better power while pinging.....pistons have lasted a year like this with minimal oil consumption......wierd.......am I the only one seeing this?
Richard
I had the timing backed down to 20º at first then added 5º of timing and saw an average of 11 rwhp and torque.........kr and all. Here in Kalifornia we only have 91 Octane pump gas and add 100º+ temps, you get kr aplenty. Still my engine makes better power while pinging.....pistons have lasted a year like this with minimal oil consumption......wierd.......am I the only one seeing this?
Richard
Re: HP loss from 29degrees to 23? I think you have to distinguish between pulling
timing with a constant mixture, and moving timing
and mixture together to keep just at knock
threshold. Because as I understand it the MBT
(maximum spark advance, best torque) lies just
short of the onset of knock. In a continuous
output scenario, KR will keep you right there
(sort of a closed-loop timing control) or maybe
just a hair into knock, one ping every N turns.
Being at MBT means basically you have the full
downstroke to apply cylinder pressure to crank
torque; any earlier and you would knock, any
later means you will huff more pressure out the
exhaust (starting later, your BDC pressure is late and your integral (pressure-curve * piston
area * crank lever arm @ angle) delivered torque
reduced.
But, the faster burn of a leaner mixture offsets
the required and allowable spark advance to make
the pressure peak's leading edge happen just barely after TDC. So MBT moves with mixture.
My question is more like, if you had (say) 13.0:1
AFR and the maximum spark (or steady-state-proper
KR) to make that mixture's MBT point, and
12.8:1 / MBT(12.8), and 12.6:1/MBT(12.6), ... where do you attain highest output torque and
highest peak HP?
For -a given mixture- you get highest HP/TQ at
the MBT (by definition) and this point is (by
conventional wisdom) at your maximum doesn't-knock
spark advance. So pulling must cost you TQ/HP and
pushing does nothing (because of the KR mechanism)
except expose you to the chance of detonation
damage before KR can save you, if it's a hard
enough knock and happens once too many (KR is
always one event late).
timing with a constant mixture, and moving timing
and mixture together to keep just at knock
threshold. Because as I understand it the MBT
(maximum spark advance, best torque) lies just
short of the onset of knock. In a continuous
output scenario, KR will keep you right there
(sort of a closed-loop timing control) or maybe
just a hair into knock, one ping every N turns.
Being at MBT means basically you have the full
downstroke to apply cylinder pressure to crank
torque; any earlier and you would knock, any
later means you will huff more pressure out the
exhaust (starting later, your BDC pressure is late and your integral (pressure-curve * piston
area * crank lever arm @ angle) delivered torque
reduced.
But, the faster burn of a leaner mixture offsets
the required and allowable spark advance to make
the pressure peak's leading edge happen just barely after TDC. So MBT moves with mixture.
My question is more like, if you had (say) 13.0:1
AFR and the maximum spark (or steady-state-proper
KR) to make that mixture's MBT point, and
12.8:1 / MBT(12.8), and 12.6:1/MBT(12.6), ... where do you attain highest output torque and
highest peak HP?
For -a given mixture- you get highest HP/TQ at
the MBT (by definition) and this point is (by
conventional wisdom) at your maximum doesn't-knock
spark advance. So pulling must cost you TQ/HP and
pushing does nothing (because of the KR mechanism)
except expose you to the chance of detonation
damage before KR can save you, if it's a hard
enough knock and happens once too many (KR is
always one event late).
TECH Apprentice
Joined: Jun 2002
Posts: 321
Likes: 0
From: Bowling Green, KY
Re: HP loss from 29degrees to 23? 98's are prone to false knock. I've seen it several times myself. I believe they almost recalled them for false knock sensors, but didn't, might want to get some new ones and see if that fixes the problem.
Re: HP loss from 29degrees to 23? thanks for the info Brent... But i did bump the timing back from 30 to 28 and still saw roughly the same knock as soon as I go WOT.. then it drops off to like 1.8 from 6000-6400rpms
one day it does it, then others it wont... argh
one day it does it, then others it wont... argh
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