Split BLM's at idle/closed throttle ONLY ... ?
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Joined: Apr 2003
Posts: 2,628
From: Pgh, PA
WS6T3RROR - Idle is set at 825. I have considered playing with it both up and down 50RPM's to see what happens.
My idle timing was pretty low also and did not transition smoothly into my Main Spark tables so I upped the idle timing to 32* and will see what happens. As long as I get no KR I am going to up it another degree and see what happens to my idle vacuum. If it doesn't change then no need to continue advancing...
My cam has a lot of overlap, but not a lot of duration. It has some pro's and con's - one of them being that at idle it has similar characteristics to a much larger duration camshaft. So we will see what I can tune out ... I don't want the idle any higher than 950 but I am confident between tuning (because my tables were did need some smoothing out) and advise from some of the more experienced guys on here I can greatly improve from where I currently stand.
Thanks again by the way!
My idle timing was pretty low also and did not transition smoothly into my Main Spark tables so I upped the idle timing to 32* and will see what happens. As long as I get no KR I am going to up it another degree and see what happens to my idle vacuum. If it doesn't change then no need to continue advancing...
My cam has a lot of overlap, but not a lot of duration. It has some pro's and con's - one of them being that at idle it has similar characteristics to a much larger duration camshaft. So we will see what I can tune out ... I don't want the idle any higher than 950 but I am confident between tuning (because my tables were did need some smoothing out) and advise from some of the more experienced guys on here I can greatly improve from where I currently stand.
Thanks again by the way!
Thread Starter
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Joined: Apr 2003
Posts: 2,628
From: Pgh, PA
wrd1972 - You have a similar cam to me! Mine should have slightly more aggressive lobe profiles and higher lift. Same duration. Mine is what would be the LE1.5...
Can you give me some rough estimates here for your timing at idle, what kind of kPa readings at idle, and the idle speed? Thanks I appreciate it!
Joe
Can you give me some rough estimates here for your timing at idle, what kind of kPa readings at idle, and the idle speed? Thanks I appreciate it!
Joe
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Joined: Nov 2002
Posts: 74
From: Markham, ON
LE2 Cam here and similar split BLM...
The driver side looks to be good at 130LT/128ST but the passenger side LT is at 160.
Currently have my idle timing @ 32-33°, 950rpm. MAP is around 65. I have the TB stop screw backed off and drilled out the IAC passage in the AS&M 58mm.
Let me know if you make any progress.
Dave
The driver side looks to be good at 130LT/128ST but the passenger side LT is at 160.
Currently have my idle timing @ 32-33°, 950rpm. MAP is around 65. I have the TB stop screw backed off and drilled out the IAC passage in the AS&M 58mm.
Let me know if you make any progress.
Dave
Last edited by DDZ/28; Sep 25, 2009 at 06:50 AM.
Thread Starter
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Joined: Apr 2003
Posts: 2,628
From: Pgh, PA
Dave,
Thus far I have been unsuccessful. I have brought my idle timing up from 27* to 32*. I will continue to advance timing as this has been smoothing out my idle. As a result my IAC counts are lowering from 50ish to 26ish at a hot idle. This is (I assume) from a more efficient burn at idle. Less fresh air is pumped out via the exhaust.
I am going to continue to play with my tune. Will be advancing my Closed TPS Spark Timing another degree or two and then trying to thread the TB Stop Screw in as far as I can (again) without the TB Blades sticking. This will force the vast majority of Idle Air to travel through the IAC passageway. Also, I will try pulling some plugs after letting it run at a hot idle for a while to try to diagnose a problematic cylinder that could be rich/lean and causing the split.
If this still does not cure my issue, I will be purchasing an IR Thermometer and tuning Individual Cylinder Fuel Trim Multipliers the best I can...
Joe
Thus far I have been unsuccessful. I have brought my idle timing up from 27* to 32*. I will continue to advance timing as this has been smoothing out my idle. As a result my IAC counts are lowering from 50ish to 26ish at a hot idle. This is (I assume) from a more efficient burn at idle. Less fresh air is pumped out via the exhaust.
I am going to continue to play with my tune. Will be advancing my Closed TPS Spark Timing another degree or two and then trying to thread the TB Stop Screw in as far as I can (again) without the TB Blades sticking. This will force the vast majority of Idle Air to travel through the IAC passageway. Also, I will try pulling some plugs after letting it run at a hot idle for a while to try to diagnose a problematic cylinder that could be rich/lean and causing the split.
If this still does not cure my issue, I will be purchasing an IR Thermometer and tuning Individual Cylinder Fuel Trim Multipliers the best I can...
Joe
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Joined: Jul 2002
Posts: 1,277
From: Phoenix, AZ
Thought I would ask. Very bad split.
My cam is more aggressive than yours and have perfect 128/128 BLM's at idle so a solution is out there.
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Joined: Apr 2003
Posts: 2,628
From: Pgh, PA
Dave,
TB is stock for now ... Want to upgrade to a 58MM or Monoblade in the future (for the D1SC I have laying around collecting dust...) but do not want to open a whole nother can of worms until I diagnose this issue.
I truely do think it is something with my tune, but we shall see. Hopefully I get to the bottom of this sooner rather than later.
Joe
TB is stock for now ... Want to upgrade to a 58MM or Monoblade in the future (for the D1SC I have laying around collecting dust...) but do not want to open a whole nother can of worms until I diagnose this issue.
I truely do think it is something with my tune, but we shall see. Hopefully I get to the bottom of this sooner rather than later.
Joe
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Joined: Nov 2002
Posts: 74
From: Markham, ON
"Are you sure that your TB does not dump the air into the main plenum? My TPIS did until I modified it to force all the air into the idle air plenum"
Yup I'm sure. Modified it exactly like some of the websites I've seen. I'm going to try drilling that hole out a little more just to see what happens. Also going to try playing with the Individual Fuel Trims....
What's weird was I had a single plane intake on last month & the driver side had BLM's maxed at 160. Put a ported stock intake on and now it's the passenger side?
Yup I'm sure. Modified it exactly like some of the websites I've seen. I'm going to try drilling that hole out a little more just to see what happens. Also going to try playing with the Individual Fuel Trims....
What's weird was I had a single plane intake on last month & the driver side had BLM's maxed at 160. Put a ported stock intake on and now it's the passenger side?
Thread Starter
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Joined: Apr 2003
Posts: 2,628
From: Pgh, PA
JakesZ28 - Thanks, I will use that as a last resort. My cam is "oddly" proportioned being a 224*/230* .600/.600 108+2 LSA but its not THAT aggressive. I believe this is a tuning issue.
This Sunday I will be (hopefully - time & weather permitting) running it at hot idle for 20-30 minutes. Checking as many plugs as I can to see if I have a lean or rich cylinder(s). I also will check (again) with starting fluid all around the manifold, TB, injectors, etc. for a vacuum leak. And lastly, I will double check for any exhaust leaks prior to the 02's.
However, I believe this car is mechanically sound. The problem I feel is in the tune. I feel this way because the Split BLM's are drastic at idle. As soon as you increase RPM by any means (driving, light load, heavy load, no load, downshifting, etc.) the split is essentially gone. It is totally gone in many cells and less than a 2-5 split in the few remaining instances. If I have a vacuum leak, or bad O2, it would be more consistant and not just a problem at idle.
I ordered an IR Thermometer that should be here by Tuesday or Wednesday if reading the plugs is unsuccessful. Maybe that will shed some light on it.
I believe my problem to be in the Individual Cylinder Fuel Trim's "On-Idle"... If anyone wants to take a looksee at it:
Cyl. Off Idle At Idle
1 - 1.03 1.06
8 - 0.98 0.95
4 - 1.02 0.95
3 - 1.02 1.00
6 - 0.99 0.98
5 - 0.97 0.95
7 - 0.98 0.94
2 - 1.02 1.08
Thanks,
Joe
This Sunday I will be (hopefully - time & weather permitting) running it at hot idle for 20-30 minutes. Checking as many plugs as I can to see if I have a lean or rich cylinder(s). I also will check (again) with starting fluid all around the manifold, TB, injectors, etc. for a vacuum leak. And lastly, I will double check for any exhaust leaks prior to the 02's.
However, I believe this car is mechanically sound. The problem I feel is in the tune. I feel this way because the Split BLM's are drastic at idle. As soon as you increase RPM by any means (driving, light load, heavy load, no load, downshifting, etc.) the split is essentially gone. It is totally gone in many cells and less than a 2-5 split in the few remaining instances. If I have a vacuum leak, or bad O2, it would be more consistant and not just a problem at idle.
I ordered an IR Thermometer that should be here by Tuesday or Wednesday if reading the plugs is unsuccessful. Maybe that will shed some light on it.
I believe my problem to be in the Individual Cylinder Fuel Trim's "On-Idle"... If anyone wants to take a looksee at it:
Cyl. Off Idle At Idle
1 - 1.03 1.06
8 - 0.98 0.95
4 - 1.02 0.95
3 - 1.02 1.00
6 - 0.99 0.98
5 - 0.97 0.95
7 - 0.98 0.94
2 - 1.02 1.08
Thanks,
Joe
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Joined: Aug 2005
Posts: 4,405
From: Kantuckee Yo'
I was told that this was for WOT cell only.
Are you sure?
Bringing this one back to life.
Joe,
Did you resolve your cell 16 split BLM?
I am now chasing this problem once again. There are times when mine is 128/128 and then it will like a flick of the switch, go big split.
I have built an insert for my BBK TB to force all of my idle air through the small hole, the OEM idle air circuit. This allowed me to further close my blades without them sticking like before. This helped the splits just running in the garage a little but I cant drive it right now due to weather to properly test.
I am confident there are no vacuum or exhast leaks. Also the rest of the operating BLM's do not appear to be badly split.
Assuming it remains, how big an effect does the individual fuel trims really affect BLM splits? Have people used this to fix cell 16 splits?
Are you sure?
Bringing this one back to life.
Joe,
Did you resolve your cell 16 split BLM?
I am now chasing this problem once again. There are times when mine is 128/128 and then it will like a flick of the switch, go big split.
I have built an insert for my BBK TB to force all of my idle air through the small hole, the OEM idle air circuit. This allowed me to further close my blades without them sticking like before. This helped the splits just running in the garage a little but I cant drive it right now due to weather to properly test.
I am confident there are no vacuum or exhast leaks. Also the rest of the operating BLM's do not appear to be badly split.
Assuming it remains, how big an effect does the individual fuel trims really affect BLM splits? Have people used this to fix cell 16 splits?
Last edited by wrd1972; Jan 26, 2010 at 10:33 AM.
Registered User
Joined: Aug 2005
Posts: 4,405
From: Kantuckee Yo'
Here are some pics of my TB mod:
I have done some tweaking on the blades and found the best position I could. The blades are nearly completely closed and the TPS voltage is .71V and the IAC counts are very steady at 35-38 points. I also raised the idle RPM from 800 to 950 RPM.
The TB mod seems to have made the cell 16 BLM's more consistant but they are still clearly split. They seem to be planted at 118/130 after some quick road testing. I am going to do some more testing to see if they stay like this.
My current (tuner tweaked) individual cylinder trims at idle are:
1 - 1.02
8 - 0.98
4 - 0.98
3 - 1.01
6 - 1.01
5 - 0.98
7 - 0.99
2 - 1.02
FTR, the OEM stock individual cylinder trims at idle are:
1 - 1.06
8 - 0.95
4 - 0.95
3 - 1.00
6 - 0.98
5 - 0.95
7 - 0.94
2 - 1.08
I am also gonna try the individual trim numbers that WS6T3RROR posted to see what happens.
I am intersted in hearing someone chime in on the individual bank fuel trims and whether there is hope for fixing the split.
I have done some tweaking on the blades and found the best position I could. The blades are nearly completely closed and the TPS voltage is .71V and the IAC counts are very steady at 35-38 points. I also raised the idle RPM from 800 to 950 RPM.
The TB mod seems to have made the cell 16 BLM's more consistant but they are still clearly split. They seem to be planted at 118/130 after some quick road testing. I am going to do some more testing to see if they stay like this.
My current (tuner tweaked) individual cylinder trims at idle are:
1 - 1.02
8 - 0.98
4 - 0.98
3 - 1.01
6 - 1.01
5 - 0.98
7 - 0.99
2 - 1.02
FTR, the OEM stock individual cylinder trims at idle are:
1 - 1.06
8 - 0.95
4 - 0.95
3 - 1.00
6 - 0.98
5 - 0.95
7 - 0.94
2 - 1.08
I am also gonna try the individual trim numbers that WS6T3RROR posted to see what happens.
I am intersted in hearing someone chime in on the individual bank fuel trims and whether there is hope for fixing the split.
Last edited by wrd1972; Jan 27, 2010 at 08:48 AM.
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Joined: Oct 2001
Posts: 1,517
From: Engineerland
Didn't read the whole thread again but, if you're able close the blades down and try to get the iac counts up closer to 100. The idea being to force much more of the idle air through the iac manifold to try and avoid the cross talk between cylinders that happens when it goes through the blades/plenum.
Registered User
Joined: Aug 2005
Posts: 4,405
From: Kantuckee Yo'
Didn't read the whole thread again but, if you're able close the blades down and try to get the iac counts up closer to 100. The idea being to force much more of the idle air through the iac manifold to try and avoid the cross talk between cylinders that happens when it goes through the blades/plenum.
I do however have the bypass hole drilled in the passage and because of that I cant get my hot idle IAC's any higher than they are now without reducing the size or plugging the hole. Without the bypass when I first got the TB, the hot idle IAC were very high and out of what most would call "normal" spec. The bypass hole is currently a "fuzz" bigger than the hole in the OEM stock TB.
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Joined: Oct 2001
Posts: 1,517
From: Engineerland
Ok, if you've modified the iac motor bypass then you're ok. I have just found that with some aftermarket throttle bodies the accuracy of the blade and bore machining leaves something to be desired.
If your counts are almost pegged at cold start, are they that way a long time or do they quickly come down to normal. Is your target idle a lot higher when cold? If your target idle is really similar and the iac stays nearly pegged when cold sometimes that indicates that the open loop target fuel is a little too rich. Just something to think about.
If your counts are almost pegged at cold start, are they that way a long time or do they quickly come down to normal. Is your target idle a lot higher when cold? If your target idle is really similar and the iac stays nearly pegged when cold sometimes that indicates that the open loop target fuel is a little too rich. Just something to think about.