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Thread: 95 LT-1 Idle Cell Comparison - Humidity?

  1. #61
    Fuel Injected!
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    Agreed with you there. Guy wanted to sell my friends and I a Mercedes Benz V12 Biturbo. For an unbelievably low price, because he couldn't get it to run. So we went over thinking, sure, why not, let's see what we're in for. Well it turns out there's no physical key for the ignition, so you can't start the car without the fob. But even more hilariously, even if you have the fob, you can't start the car if the car's been left with a dead battery for too long, because then the backup battery for the security system fails and the only solution is to have the vehicle towed to a Mercedes dealer along with you and all the paperwork proving you own the car so they can install a brand new security computer and give you new keys.

    Needless to say we walked away and wished him luck.

    Here's me wishing you luck that the slipped rotor has been the only issue this whole time. :)

  2. #62
    Fuel Injected! vilefly's Avatar
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    I was thinking that you could add 20 degrees advance across the board to your timing tables to confirm your suspicions about the distributor without taking stuff apart. Turn the key and see if it liked it.

  3. #63
    Fuel Injected! spfautsch's Avatar
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    As far retarded as it was I think the best I could've done was lock timing at max (46 btdc) with eehack. That might have given me 16 degrees advance best case, and it would have still ran like crap that way. With the egr the cam generates it wants at least 28 degrees spark advance at 925 rpm idle.

    It's kind of immaterial - I'll have it back together this weekend if the "baby" degree wheel shows up when it's supposed to. My good wheel interferes with the k-member by about 2 inches.

    After moving the hub yesterday I feel like this had to have happened gradually over numerous driving sessions. As hot as I was comfortable getting the hub without burning the lube out of the bearing, it still took quite a bit of force (with a channel lock pliers no less) to turn the hub back.

  4. #64
    Fuel Injected! vilefly's Avatar
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    https://www.blocklayer.com/degree-wheel.aspx

    Here. Print out one of these babies on card stock paper. Works for me in a pinch. Lots of options, too.

  5. #65
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by vilefly View Post
    Print out one of these babies on card stock paper. Works for me in a pinch.
    I'd have to be in a pretty big "pinch" to use card stock, but I guess it could work. The nice thing about the neat little 7" wheel I got off slamazon for $15 is that even though it's aluminum it's a nice high-density extrusion and when I'm not using it for timing an engine I can hang it on my drum kit as a gong for when I want to attempt Rush's YYZ.

    Once again I got called into service as a used car salesman over the weekend, otherwise this would have been done last sunday. If I could have found an adjustable MSD dizzy for a reasonable price I'd have been all over that - the time it would have saved would have almost made buying one new worthwhile. After getting the hub back to zero it took almost 6 hours and numerous 3/32" cobalt drill bits to get a hole drilled in the hub to lock it in place. It seems like it's some kind of powdered metal and damn is it hard!

    Anyway, I've got a couple odd things going on now - first log was with -2 degrees spark advance by way of setting the 0x012044 "Spark Reference Angle" to 2 because I thought my hub was a couple degrees more advanced than I wanted. Stock injectors with original characterization and individual cylinder trims. Judging by the idle quality I think the timing was actually spot on and my determining of geometric TDC with the engine in the car (and heads on) was off by +2 degrees.

    Right bank is quite a bit lean especially before bumping idle timing back +2 degrees and resetting blms to 128. I'm going to pull my plugs from that side to see if one of the iridium electrodes "blew" off.

    Spark plug discussion detour: I compared my ACD double platinums to a Bosch 9655 double iridium and a Denso 4713 TT iridium using the highly scientific "eyeball" method, and the Denso TTs gapped at 0.040" produced a far superior spark to all the above (even the copper NGKs I bought in desperation). Detour over, back to the main subject...

    For the second log I pulled the 2 degrees of retard back out of 0x012044 and reverted to the individual cylinder trims I arrived at months ago. Right bank still pretty lean. I forced closed loop for a short time and other than having +10 blms on the right bank it wasn't idling too shabbily. I saw a few data frames with 41.5 kpa at ~9.8 g/s on the MAF. The IAC counts hit 24 which tells me I probably need to go to the next smaller IAC bypass orifice because today was another 93F scorcher with swamp-ass humidity levels. This seems to invalidate the usefulness of enlarging the idle air feeds in the manifold.

    At this point I think I only have one other problem to locate. But...

    In both of these logs it didn't start right away like it was before this problem manifested itself. So I have more troubleshooting to do, because before this started I never needed to crank more than 1-1/2 engine revolutions before it took off.

    Hopefully it won't take me another two weeks to track down these problems. I'm about exhausted...
    Attached Files Attached Files

  6. #66
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    There is a lean condition on both sides, that evolve to one side later, that can be caused by numerous things.
    The mechanical issues must be ruled off first. I would start at tapping the hole in the intake blade and load the last good ind cyl trims you have on record. The extra air from the hole can screw up alot of the fueling so as a first measure just make it temporaly tapped.
    At this point make an idle log. If there is no improvement on lean bank to bank condition, swap injectors per bank. Now you can rule out a clogged or pissy injector. If the lean bank moves with the injectors the injectors are toast.
    The last mechanical issue could be small exhaust leaks. It can affect 02s reading even if the leak is after them. Just for the record did you swap the 02s with delco ones.

    If nothing of this help it is time to do some tuning. The maf table needs to be dialed first, than fine tune the individual cyl trims. Than tune the spark and again fueling since spark and fuel at idle are closely related and couple of degrees less or more advance can shoot your afr off chart.

    I am having the same hard cold starting issue that developed out of nowhere. It will start right away after it has been running for a while cold or hot. The issue shows if it have been sat for a couple of hours no matter cold or hot is the engine. NO tuning helped at all so far, so i am thinking a mechanical issue could be the problem.

    Spark reference angle offset all timimg tables by the amount specified. It doesn`t correct injector timing and any other opti related calculations.

  7. #67
    Fuel Injected! spfautsch's Avatar
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    Quote Originally Posted by kur4o View Post
    There is a lean condition on both sides
    If you look at the first log the extreme lean condition on both sides improves on the odd bank when I manually increase idle timing from 27 to 29.

    Another factor is the BLMs - I keep forgetting to increase the keepalive value to 128. I don't necessarily intend to continue running open loop, but that would be something anyone who is (running open loop full time) should do. Anyway, when I reset them to 128 the lean condition improves markedly.

    Quote Originally Posted by kur4o View Post
    I would start at tapping the hole in the intake blade
    There are no holes in the throttle blades and I've re-adjusted them back to fully closed so there should be very little air getting past the throttle at idle.

    Quote Originally Posted by kur4o View Post
    ... If there is no improvement on lean bank to bank condition, swap injectors per bank.
    I believe my plan of attack will be putting my big injectors back in. I have the feeling the 150k mile stock Multecs have had the varnish in them solidify from sitting dry in my parts bin for 2+ years. I'm crossing my fingers this is my starting problem also.

    Quote Originally Posted by kur4o View Post
    Just for the record did you swap the 02s with delco ones.
    Yes, these logs were taken with the AFS75s. If you scan through the second log there's a ~30 period starting at 142.1 where I forced closed loop. When I switched back to open loop the odd bank BLM was still 128 but the even bank had climbed all the way to 142. This was with the factory closed loop parameters restored - not a single item has been touched, even 0x26fb Integrator / Transport Delay.

    Quote Originally Posted by kur4o View Post
    If nothing of this help it is time to do some tuning. The maf table needs to be dialed first
    I think my methodology is going to be leaving the MAF calibration alone until all other avenues have been explored. From what I've been able to find on the subject I don't think I'm going to be able to considerably improve on what GM did there.

    Quote Originally Posted by kur4o View Post
    I am having the same hard cold starting issue that developed out of nowhere. It will start right away after it has been running for a while cold or hot. The issue shows if it have been sat for a couple of hours no matter cold or hot is the engine. NO tuning helped at all so far, so i am thinking a mechanical issue could be the problem.
    I had the same warm restart issue before increasing displacement, and I was able to find a sweet spot between prime pulse and cranking VE. Unfortunately the prime pulse table lacks the resolution necessary for much fine tuning in the warm / hot regions, especially with larger than stock injectors.

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