Trimming too much fuel in closed loop
I have my brothers 96 camaro running great in closed loop...its a 383 solid roller LT motor with over 30 degrees of overlap. It does have a 24x 411 swap. I do agree it would be easier to run a open loop hybrid tune as mentioned above...that's initially how I had his car setup. The main thing was getting good injectors and data then getting the maf/ve table dialed. Big cam cars are very picky about fueling down low. We went through a couple sets of injectors before we found a set(Deka 60's) that had enough fuel headroom on E85 and still offered good drivability . All that being said I would try a different set of injectors since it has been mentioned those 80's have poor idle quality before going any further. Or you will chase your tail tuning that thing.
Thread Starter
Joined: Oct 2002
Posts: 523
Likes: 58
From: Winnipeg, Manitoba, Canada
It's on the dyno right now. New tuner guy wants to try tuning the SD 80 first. If it doesn't work properly he'll switch to SD 60.
So far with 21 degrees of timing it's at 575 rwhp.
So far with 21 degrees of timing it's at 575 rwhp.
Thread Starter
Joined: Oct 2002
Posts: 523
Likes: 58
From: Winnipeg, Manitoba, Canada
Are you saying that's specific to the 80's? The 60's are rock solid and work like gold. I dont believe idling is the issue. It's the fuel trims in closed loop skewing the AFR due to the size cam. Longtubes, overlap, big injectors, yeah it wont like closed loop at idle with factory narrowband O2's.
Looking at his log file it's idling at 900 rpm at ~70 KPA. For comparison my 427 with big Brodix BR7s is running a 252/260 duration cam idling at 1000 rpm at ~80 KPA and it idles clean as a whistle in closed loop with ID 1700s with no tip in issues because it's not constantly trying to pull fuel due to dirty combustion from a relatively crappy injector. I would suspect that it doesn't matter how much fuel he pulls out down low, the trims will still go negative and it will just make it idle and recover worse. Putting it in OL at idle will cover this up since it won't be trying to trim fuel but with a better injector it would have no problems running in closed loop at idle.
Thread Starter
Joined: Oct 2002
Posts: 523
Likes: 58
From: Winnipeg, Manitoba, Canada
I'll post a log tonight. I got it idling much better. No more huge trimming issues and no stumble under load. Just trying to deal with it bucking at 1500 rpm.
Deka Siemens 60's are the gold standard for fuel injectors. In the last decade before or after them I have not seen anything that can compare for fuel flow, repeatability, or range of useable fuel pressure. Almost every competitor has at the very minimum idle problems, and on the other end high pressure lockup. It seems that we should have something better all these years later.
Thread Starter
Joined: Oct 2002
Posts: 523
Likes: 58
From: Winnipeg, Manitoba, Canada
If I was to switch to another injector, are SD60 the same height as the SD80? I'm using a custom fuel rail and mounts and don't want to have to fabricate new mounts for different heights.
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Verdad Gallardo Yes SD 80s are garbage injectors at lower pulsewidths, plenty of larger injectors out there now a days that are MUCH better down low. The SD 60s are far different then the 80s.
Looking at his log file it's idling at 900 rpm at ~70 KPA. For comparison my 427 with big Brodix BR7s is running a 252/260 duration cam idling at 1000 rpm at ~80 KPA and it idles clean as a whistle in closed loop with ID 1700s with no tip in issues because it's not constantly trying to pull fuel due to dirty combustion from a relatively crappy injector. I would suspect that it doesn't matter how much fuel he pulls out down low, the trims will still go negative and it will just make it idle and recover worse. Putting it in OL at idle will cover this up since it won't be trying to trim fuel but with a better injector it would have no problems running in closed loop at idle.
Looking at his log file it's idling at 900 rpm at ~70 KPA. For comparison my 427 with big Brodix BR7s is running a 252/260 duration cam idling at 1000 rpm at ~80 KPA and it idles clean as a whistle in closed loop with ID 1700s with no tip in issues because it's not constantly trying to pull fuel due to dirty combustion from a relatively crappy injector. I would suspect that it doesn't matter how much fuel he pulls out down low, the trims will still go negative and it will just make it idle and recover worse. Putting it in OL at idle will cover this up since it won't be trying to trim fuel but with a better injector it would have no problems running in closed loop at idle.
There are plenty of better injectors out there than the SD 60s, an ID 1300x flows double what those do and would be better in every single way. Fuel injector clinic and fuel injector connection also use Bosch EV14 cores and have been very good throughout the years for those that don't want to pony up for IDs. Siemens Deka injectors don't even have stainless steel internals and aren't rated for alcohol based fuels or anything with MTBE in them either, and good luck getting them to open above 80 psi ACCURATELY where as the IDs will go above 100 psi and still work correctly.
Now that you have figured out how much bad behavior can be corrected with proper tuning, I should mention that eventually you will get to the point where you have fixed everything, but you still have not achieved a factory smooth micro cam style tune. Eventually your hardware choices will catch up to you. I only mention this because I have seen both sides. People with mild hardware and horrible tunes putting up with bad drivability, and people with full on race everything who want stock drivability are both living in a bad version of reality.
Thread Starter
Joined: Oct 2002
Posts: 523
Likes: 58
From: Winnipeg, Manitoba, Canada
Now that you have figured out how much bad behavior can be corrected with proper tuning, I should mention that eventually you will get to the point where you have fixed everything, but you still have not achieved a factory smooth micro cam style tune. Eventually your hardware choices will catch up to you. I only mention this because I have seen both sides. People with mild hardware and horrible tunes putting up with bad drivability, and people with full on race everything who want stock drivability are both living in a bad version of reality.