Rationalize this with me...
08-02-2005, 10:50 PM
#1
Rationalize this with me... Vehicle: 1999 Corvette
Mods: Aggressive H & C Fast 90mm NW TB
Important info:
Throttle Cracker Disabled
- The ECU won't add any air before it gets to idle
Spark Under and Over speed disabled
VE within 3%
RAF is dead on + - 0
Desired:
The idle comes down and should stick @ 900....
Actual:
The idle comes down and drops below desired RPM
Suggests the TB is not opening enough at idle and the computer is correcting for it so....
The Effective area needs to be changed... Does it need to be shifted left or right?
Phil
Mods: Aggressive H & C Fast 90mm NW TB
Important info:
Throttle Cracker Disabled
- The ECU won't add any air before it gets to idle
Spark Under and Over speed disabled
VE within 3%
RAF is dead on + - 0
Desired:
The idle comes down and should stick @ 900....
Actual:
The idle comes down and drops below desired RPM
Suggests the TB is not opening enough at idle and the computer is correcting for it so....
The Effective area needs to be changed... Does it need to be shifted left or right?
Phil
08-03-2005, 08:57 AM
#5
you disabled the overspeed spark conrtol? have you noticed better idle quality with this? im working on trying it on my car now actually to try to get idle to change no more than 75 rpm max to min. so what are you saying? when slowing down the idle drops lower than it should? or the airflows arent matching up? i assume you used your 90 mm effective area settings? i tried my stock settings on a car that i did and it was off a bit at first from mine but now its comming right back where it should. dont you want throttle cracker to start adding air before it gets to idle so it wont dip lower?
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08-03-2005, 12:45 PM
#8
FormerVendor
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Have you tried logging teh ltits and stits with HPTuners. THese two pids will tell you how much correction is needed to get the idle dialed in and you add this to your raf table and call it a day....
08-03-2005, 12:54 PM
#9
The LTIT and STIT are right where they need to be. Here's what I think is happening....
When coming off of a rev, the engine needs 1.95 lbs of air per min, the VCM says you need 8 steps to make it idle when you really need 10 steps(more throttle position)
Phil
When coming off of a rev, the engine needs 1.95 lbs of air per min, the VCM says you need 8 steps to make it idle when you really need 10 steps(more throttle position)
Phil
08-03-2005, 12:57 PM
#11
going to the left will open more let more air in going to the right opposite. phil when you get a chance let me know about effective area for ETC cars and how thats working out. we talked a while back and i just never got an update on how you got it taken care of, dont kow if its a different process. your idle trims will change after you do this as well.
08-03-2005, 01:03 PM
#12
TECH Junkie
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when tuning my idle, my Desaic_B (desired idle air flow) was 5 and my desired air flow was 10. According to the HPT write up, the Effective area table needed to shift right, EFILive down, in order to make the two match.
Once I had all my numbers right, I was able to adjust the idle set screw to get the counts in line.
Once I had all my numbers right, I was able to adjust the idle set screw to get the counts in line.
08-03-2005, 01:04 PM
#13
From Nick Williams and gojo - move "Eff Area" Table 6 places to the right (1st step at 24 mm2) . Return the "Idle Air Parked" table to stock values. Do an Idle Relearn.
My suggestion- If you want to Zero the LTITs then pull both PCM fuses for longer than 3 minutes.
My suggestion- If you want to Zero the LTITs then pull both PCM fuses for longer than 3 minutes.
Last edited by Bink; 08-03-2005 at 01:27 PM.