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Thread: S52 New Build Tune/Timing/VANOS Challenge in Seattle

  1. #1
    Join Date
    Sep 2018
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    Seattle
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    E36 M3

    S52 New Build Tune/Timing/VANOS Challenge in Seattle

    Hi All -

    First post from a 10-year+ lurker on Bimmerforums, based in Seattle. I've never been this stumped on an issue before - hoping you might be able to diagnose / suggest a course of action for further diagnostic without a top end tear down.

    Car is a 1997 M3 sedan, Arctic Silver. I've owned it as my daily driver since CPO purchase in '99 with 20K miles. It's been a great car. Tracked once a Pacific Raceways early on, road time ever since.

    Last year at 175K began to experience leaking valve seals (upon inspection the bottom end was rock solid -- could have gone another 125K).

    I pulled the trigger on a complete NA rebuild of the original S52, going with 11:1 compression.

    Goal is to get another 175K out of the car with some power upgrades for fun.

    Primary components are CP Carillo pistons, Pauter rods, mild Schrick cams, 24 lb rebuilt and tested injectors, high flow Porsche MAF, AFE CAI. Basically anything recommended for livable NA power on pump gas, I did it. Decided to replace the transmission and diff at the same time. Machine work was done at a very reputable race/restoration shop, an established indie mechanic put it together. I got the car back a year ago October '17 and began daily driving the car again with the new drivetrain. I should mention that prior to the rebuild, the stock VANOS seals had been replaced with Beisan seals and rattle kit.

    As the weather warmed up in May/June and I started driving windows rolled down, and noticed a distinct high metallic ping/rattle/thrashing sound from the engine bay -- only under load (uphill) when the motor is fully hot. It starts around 3500, peaks at 4K, and fades above 4200 RPMs. It's a higher RPM range than the "marbles in a can" sound typically associated with VANOS issues. The noise is not audible with the car windows up -- but loud with windows down and especially when driving along a guard barrier. A tech at the build shop suspects pinging/detonation.

    The initial tune on the rebuilt motor was sourced by the shop from another car and never felt strong. (Important life lesson here -- aftermarket tuning is fundamental to an aftermarket build -- this shortcut was a total fail). Between what I think are pinging/detonation symptoms and the lack of power for what should have been a strong build, I decided to dyno the car at Carb Conn in Kirkland with Randy at Epic Motorsports tuning online using a sniffer for AFR. The first runs were max 220WHP and 225 Wtorque and peak AFR of 14.6... low power and WAY lean from what I have read. The final tune that day was 236WHP and 241.5 Wtorque at a peak AFR of 13.5. There was no perceptible rattle/pinging during the dyno session, but the car had been sitting for awhile prior to the dyno time -- and as soon as we left the session and I was heading home the rattle/pinging was back.

    Since the dyno/tune on July 6, I have two persistent issues. The first is the pinging/rattle around 3,700. The second is a cold start idle issue that may be related. (dyno graph attached)

    The open loop idle of the car during a morning "cold" start (in a 60 degree garage, for the first 50 seconds of idle) sounds and rocks like a Harley. The initial aftermarket tune (before the dyno time and Epic) had resolved this by disabling the VANOS during cold start by applying a dealership ECU patch. This symptom has returned now that the Epic tune is in place.

    I performed two tests to try to diagnose these issues:

    On advice from Randy, I disabled the VANOS solenoid by unplugging the connection at the unit. Two observations from this: first, the cold start issues resolve COMPLETELY with the VANOS solenoid unplugged. The first 50 seconds of the open loop start are smooth as butter. And second, the pinging/rattle under load disappeared.

    The second test, suggested by my shop, was to fill the car with a tank of Trick 101 unleaded race gas. With the race gas on board (and VANOS plugged in), the open loop idle is as bad as ever but the pinging/rattle at 3,700 is completely gone. Returning to 92 pump gas, the symptoms return.

    So both the idle issue and the pinging/rattle under load fully resolve with VANOS unplugged, while the pinging/rattle (but not the cold idle issue) is resolved with race gas.

    Through all of this, no CEL until the solenoid was unplugged. After unplugging the VANOS solenoid, I read two codes, electrical and mechanical VANOS failure but I assumed they were both just related to the intentionally disconnected cable.

    If you're still with me so far, here are my theories (informed by my shop and Randy) and related open questions:

    1. Bad VANOS -- the idle issues and the pinging/rattle under load are both reflective of a bad VANOS.

    2. VANOS misalignment -- the VANOS is fine, but was misaligned upon reinstall -- it's off by a tooth or two.


    Could this cause timing to over advance?

    For both 1. and 2., these don't really make sense in isolation... if the VANOS is still mechanically engaged (even with solenoid unplugged) wouldn't I still hear a VANOS rattle? It seems more likely to me that the pinging/rattle goes away because the disabled VANOS is no longer advancing timing into detonation territory (see below).

    Notably, the car doesn't (butt dyno) feel any different with the solenoid unplugged, leading me to believe there is a VANOS issue.

    Regarding the cold idle issue, I'm not clear as to why the idle dramatically improves when the VANOS solenoid is unplugged, as the VANOS should be in the fully retarded position at idle anyway, right? I understand that single VANOS is an on/off, full retard/full advance mechanism. Why would open loop idle completely smooth out with the solenoid unplugged?

    3. Tune still too lean/too advanced -- and/or needs the dealership cold start VANOS patch.

    This is simply a tune issue. Even at 13.5 peak AFR (reading high via sniffer, I'm told), we're still just too lean for the compression. Randy has suggested that the timing map and fuel map are both sufficiently conservative to avoid any detonation, but I'm not convinced.

    What is the AFR range for an 11:1 compression S52?

    4. Cam indexing is off -- the VANOS is fine, aligned correctly and working properly, the tune is good, but the Schrick cams are out of alignment.

    Is it possible the cams are misaligned? This could explain detonation when the VANOS is advanced. It doesn't explain why the idle resolves with disconnected solenoid. The cams were indexed twice (but using blocks only).

    5. Vacuum (or exhaust) leak when hot -- causing a lean condition

    Seems highly unlikely give the complete rebuild. This would explain the pinging/rattle and why it only happens when fully warm. It doesn't explain the idle issue. It doesn't explain why both issues resolved with the solenoid disconnected, although no VANOS = less advance and less det under load. It doesn't explain why high octane gas resolves the rattle.

    6. Valve/piston interference from cam + VANOS advance

    Randy had speculated that the cam and VANOS advance could be causing the valves to impinge on the top of the pistons. The pistons are 0.35 above the deck but we are using a 0.80 HG per machinist recommendation. It seems the results would be more catastrophic if interference is happening at extreme advance (hot with VANOS). This seems like an unlikely root cause, but I'm throwing it out there.

    Well, that's all I've got. Input welcome. I'm hoping to have my wonderful daily driver M3 back in a condition that (1) allows me to drive with VANOS and (2) allows me to drive on 92 pump gas -- with a smooth(er) idle and no pinging/rattle. I would like to definitely rule out mechanical issues before circling back with Randy or spending more $ on dyno time to adjust the tune. On the other hand, I would like to avoid tearing down the head to confirm cam indexing. I can replace the VANOS next but it was just rebuilt <10K miles ago.

    What should I test/replace next?

    SZ
    Attached Images Attached Images
    Last edited by SeriesZ; 09-18-2018 at 04:53 PM.

  2. #2
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    I would not have raised compresssion to 11.0:1 with 91 octane. But all the things you mention are what I would be checking out — vanos and cam timing. Make sure the vanos spring plates are assembled correctly and that the later anti rattle spring is there. I think it was standard by 96 but am not sure. I’d check your fuel pressure also at idle and load.

  3. #3
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    Dang this sounds like it could be vanos/tune/fueling issue.

    From what I remember the standard schricks are not very hard to install, and don’t need to be timed different then stock cams.


    I’d contact RK tunes about a flash tune, and see how that works out for you .





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  4. #4
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    At least older RK tunes disabled some obd2 functions, which might avoid CEL but would be of no aid in actually getting the car sorted out. I would want to get the car sorted out rather than mask the problem(s).

  5. #5
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    Quote Originally Posted by pbonsalb View Post
    At least older RK tunes disabled some obd2 functions, which might avoid CEL but would be of no aid in actually getting the car sorted out. I would want to get the car sorted out rather than mask the problem(s).
    I’m saying maybe it’s a fueling issue with the tune. I haven’t heard rave reviews of Epics e36 obd2 tuning honestly.

    I’m also not a fan of his support of his products when purchased second hand.


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  6. #6
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    Pictures of the plugs would help.

    If race gas fixes it I’d guess too much timing.

    Lots of things can go wrong with a tune to mess up cold idle.

    We are local now, why don’t we meet up and let me take a look.


    Sent from my iPhone using Tapatalk
    1989 535i - sold
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    1998 Turbo: PTE6870 | 1.15 ar | Hp Cover, Custom Divided T4 bottom-mount, 3.5" SS exhaust, Dual Turbosmart Compgates, Turbosmart Raceport BOV, 3.5" Treadstone Intercooler, 3.5" Vibrant resonator and muffler, Arp 2k Headstuds | Arp 2k Main studs | 87mm Je pistons | Eagle rods | 9.2:1 static compression, Ces 87mm cutring, Custom solid rear subframe bushings, Akg 85d diff bushings, 4 clutch 3.15 diff, , Poly engine mounts, UUC trans mounts W/ enforcers, 22RPD OBD2 Stock ECU id1700 E85 tune, 22RPD Big power Transmission swap w/ GS6-53

  7. #7
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    Thanks for the replies - If this is a tune issue (advance or AFR) and not mechanical (cam or VANOS), wouldn’t the knock sensor normally retard the timing before the pinging is audible?

    On the idle, I don’t understand the VANOS geometry well enough to know why simply unplugging it resolves the problem.

    Vollosso - I’ll PM you...

  8. #8
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    Quote Originally Posted by vollosso View Post
    Pictures of the plugs would help.

    If race gas fixes it I’d guess too much timing.

    Lots of things can go wrong with a tune to mess up cold idle.

    We are local now, why don’t we meet up and let me take a look.


    Sent from my iPhone using Tapatalk
    Bamm local goodnesses


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  9. #9
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    Take the car to Volosso and he can figure it out much quicker than any of us can remotely. An unsorted car is no fun and you can spend a lot of money at shops that don’t know these cars very well trying to figure things out.

  10. #10
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    Volosso will probably fix it, but you could also install either Testo or Romraider logger, and then you can see in detail what's happening inside the engine when the problems occur..

    All you need is a Windows laptop, an FTDI232 USB to OBD adapter cable (and for the European people, also a 20 pin BMW to OBD adapter cable), and the software you can download for free. As a bonus you can also use INPA with the same setup.

    Very interesting:


    You can look at the knock adaptation tables, at the lambda integrator, at the Vanos degrees (camshaft).. It will very probably help to pinpoint the problem.
    I haven't tried these programs yet, but will do so soon as I'm also having some strange issues (very negative additive adaptation values)..


    1997 E36 BMW 323i
    (European) 275k km (171k miles), with following small mods:

  11. #11
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    Thanks! I’ve read a bit about these tools — and have some software (but not hardware) proficiency — would be awesome to have real data to work with. I’m going to source a cable and try my hand at the software...

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