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Thread: Why does an 8psi turbo on stock motor blow a new headgasket, twice?

  1. #51
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    Thanks, this is all very helpful.

  2. #52
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    Update: 350 miles into break in and I have the air fuel mix pretty well dialed in. Timed ‘on the ball’, using A/F gauge showing about 13 at 3000 rpm under light load, rises to 15 under boost. Idle is about 11. At this point I’ll take a richer air fuel ratio and figure it out in the spring, but it pulls well to 5000 rpm without any stuttering. Had a bitch of a time coordinating getting it to idle when warm, but reference back to the FAQs and some really good posts by JRCook helped a TON

    Which gets me to my final point—-without the time and expertise of the forum members, this project had zero chance. So THANK YOU ALL VERY MUCH!!!!

    Will update in the spring—-I still need to install a LSD that I got off an E36 small case—-before a February Winter Rally here in Vermont (God I hope Covid doesn’t screw that up).

    Bill

  3. #53
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    Cool

    Good to hear you got it stable and running.

    Several vaccines have been fast tracked and one is here right now made in Belgium by Pfizer and a German firm being flown in packed in dry ice waiting for approval and then distribution--The U.K. became the first country to approve Pfizer’s vaccine this week with the first round of immunizations expected to roll out next week. Hopefully the vaccine will sent out fast,, two shots are done a couple weeks apart and get this place somewhat back to normal..

    Randy

  4. #54
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    A tight limited slip will show that c-19 crap whose boss
    Tbd

  5. #55
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    Another update: I had it running pretty well, new 2.25” exhaust sounded and felt great. AFR still rich at 10.5 idle, swinging up to 15 to 16 at full throttle. I rechecked the valve clearances and set them cold to .006. I installed a Volvo 240 turbo vacuum canister on the distributor, set the timing at 25 deg advanced at 2550 on the Z, and started tweaking the air/fuel ratio a little bit at a time (like 1/16” turn as in FAQ) and ....

    it is all messed up. Running crappy. Enrichening the Air/Fuel ratio seems to help some, but engine still overheating under load—-3/4+ gauge when usual is between 1/4 and 1/2. It does have new radiator, new hoses, new 71 degree thermostat. Some white exhaust, certainly more than before. It was rainy and super humid today, maybe that is a factor? Since today it was in the 50s, I was able to back flush the block and it came out completely clear, I had thought maybe there was a blockage because the inlet hose popped off below the temp sensor where it goes into the block. There is flow through the engine as the top hose is hot and you can feel the flow. It idles cool enough, and temp comes back down after driving. I pulled the exhaust head pipe and it is dry, no coolant.

    Could the vacuum canister be the issue? Do I have it wildly out of whack with air/fuel ratio? Am I slowly being driven insane by a 39 year old car?

    I’ll test the compression and figure out how to do a leakdown test too, which will give necessary info.

    Please help, any advice would be very appreciated. If I cracked the head or blew another headgasket I think I might puke. At this point thinking of putting it away until spring, or giving it to a local mechanic to finish it off. But that feels like failure.
    Last edited by Vermont320i; 12-26-2020 at 12:08 AM.

  6. #56
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    1" exhaust pipe per 100 HP is a good rule of thumb. If your exhaust pipes get too large it cools the exhaust gas too fast and the exhaust gas gains weight making it harder on the motor to push it thru the tail pipe, performance drops,back pressure is too low to keep the exhaust stream by pulses optimal. Bigger exhaust is matched too bigger displacement, Do you see ?. You had it running fine you should stay with a good build until you can prove it will be better to change something, wanting ,calculated, and actual results are almost 100 % different-there is always small details that have to be accounted for that are Absent -T from the calculations.

    This is why blueprinting is important--you know precisely where everything was, the tolerances and now where it is, positive or negative feedback is the result and then go from there.

    Randy
    Last edited by 320iAman; 12-26-2020 at 03:52 PM.

  7. #57
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    Thanks Randy. Very helpful. I do see, now. I can take it back to ‘known good’ and do some research. Original vacuum canister, timing and A/F Ratio adjustments as before. Those were the changes from ‘known good’, which happened after the exhaust was redone. I don’t fully understand that, maybe I didn’t drive it far enough to test it properly. I had thought I was at the stage of tweaking it and finishing off necessary work like the vacuum canister and a boost sensing WUR, and had intended to install the WUR next.

    I’ll have to mull that over a bit, maybe put in some sort of reducer after the down pipe and test it out. Exhaust work had to happen anyway as I had cobbled together a link between my downpipe and the stock exhaust in front of the converter. The exhaust guy thought he was doing me a favor going all the way back. I suppose it could be needed someday, then I’ll have it! I did keep the old pipes and will work it out with him.

    Bill
    Last edited by Vermont320i; 12-27-2020 at 01:27 AM.

  8. #58
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    Racing cars tend to user bigger than stock exhausts as they are not concerned with doing Daily Driving. New exhaust pipes ect is a good idea , proper sizing them to the motor and exhaust manifold is not something that is written about a lot yet does have its place.

    I worked with a guy some time ago that had a Ford Galaxy, 4 speed , with 400 Plus Cu in displacement motor , dual exhaust with cherry bomb glass pack mufflers and was tuned in too sizes of exhaust pipes--stock or close was good enough.

    M10 motors have exhaust pipe that are around 1.75 in or 1 and three quarters inch diameter this is good for 105 HP 125 HP M10 motors and up to 175 horse power or so... The cats are 2 in dia the after market ones like Walker-- reducers are used to match the in and out diameter differences... Original 1980-83 BMW M10 E21 Cats are straight bolt in and out and costa plenty unless one can get them before the predatory price markups.

    Keep up the Good Work


    Randy
    Last edited by 320iAman; 12-28-2020 at 05:40 PM.

  9. #59
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    Today I checked the compression, 150psi +/-2 on 1, 2, and 3, 0 on 4. #4 plug missing center electrode. Looks like I’m taking the head off to check THAT out. Hope a valve isn’t messed up, but likely.

    I’m thinking that might be most of the problem, but will update, and follow up on exhaust size issue. Might be a while before I can get to it, but still shooting for February 27th 220 mile night time winter road rally with this car with limited slip diff. Back up plan is the wife’s Audi A4 Quattro wagon, which would be a more capable but less fun choice!
    Last edited by Vermont320i; 12-28-2020 at 06:53 PM.

  10. #60
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    Quote Originally Posted by Vermont320i View Post
    Today I checked the compression, 150psi +/-2 on 1, 2, and 3, 0 on 4. #4 plug missing center electrode. Looks like I’m taking the head off to check THAT out. Hope a valve isn’t messed up, but likely.

    I’m thinking that might be most of the problem, but will update, and follow up on exhaust size issue. Might be a while before I can get to it, but still shooting for February 27th 220 mile night time winter road rally with this car with limited slip diff. Back up plan is the wife’s Audi A4 Quattro wagon, which would be a more capable but less fun choice!
    Damn it man. My condolences. . . I'll drink beers for ya this afternoon.

    I know the AFR's reaching into 15-16s under load is no good. But I have to wonder if burned an exhaust valve on #4, usually valve before piston but never know. Post the damage.
    88 M3
    91 318is
    91 318i
    83 320is
    08 X3 3.0si

    "If it flys, floats, or f*cks, rent it!"

  11. #61
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    Safe the head ache and get a proper stand alone ecu. All of that could have been avoided in the first run. The absence of proper spark and fuel control is just a pain.
    Last edited by PowerKraut; 12-29-2020 at 03:00 PM.
    1982 E21 323i
    M50B25 Turbo
    Borg Warner S362 SX-E
    ECU Master Emu


  12. #62
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    PK, not sure I understand. The k-jet fueling system is pretty well documented on this forum as “adequate’ for a low boost turbo system on the 1.8 four cylinder. I agree it isn’t optimal.

    I would like to know what caused a plug to lose its center electrode, are you saying the fuel management system caused this? Interested, and willing to listen.

  13. #63
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    Got a picture of the spark plug(s)? And type of spark plugs.
    Tbd

  14. #64
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    Quote Originally Posted by Vermont320i View Post
    The k-jet fueling system is pretty well documented on this forum as “adequate’ for a low boost turbo system
    You are right, the K-Jet is kinda "okay", but with a standanlone you would have just SO much more control over your engine


    I would like to know what caused a plug to lose its center electrode, are you saying the fuel management system caused this? Interested, and willing to listen.
    Depends if its burned, or molten, or just broke off? .. need a pic to say anything about it. If it just "fell off" it could be anything, like maybe it was dropped before it was put in the car or so.
    1982 E21 323i
    M50B25 Turbo
    Borg Warner S362 SX-E
    ECU Master Emu


  15. #65
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    Sorry, no pics right now. #4 plug center electrode was just gone. So it sounds to me like too lean and too hot, both of which are from the turbo application with little control of fuel supply under changing conditions. Which makes PowerKraut correct.

    I think as Randy has noted, I need to do some studying. Certainly of air fuel ratios, how to change them, how they change in this engine. Unless I like continually taking my engine apart! Which apparently may also be true.

    Plugs were Bosch Silver, wr9ds
    Last edited by Vermont320i; 12-30-2020 at 02:30 PM.

  16. #66
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    Quote Originally Posted by Vermont320i View Post
    PK, not sure I understand. The k-jet fueling system is pretty well documented on this forum as “adequate’ for a low boost turbo system on the 1.8 four cylinder. I agree it isn’t optimal.

    I would like to know what caused a plug to lose its center electrode, are you saying the fuel management system caused this? Interested, and willing to listen.
    The center electrode and nothing else? Very unusual, was is burned away, or missing completely?

    click to enlarge
    spark-plug-anatomy.png
    Tbd

  17. #67
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    Just the center electrode. Missing completely. It was there when re-installed two months ago. The plugs were the same ones as when I bought the car 18 months ago. I saw no reason to change them. Maybe I dropped it and it had a hairline crack, maybe it was overheated. Maybe both. I’ll work on getting the head off this weekend.

  18. #68
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    Quote Originally Posted by Vermont320i View Post
    Just the center electrode. Missing completely. It was there when re-installed two months ago. The plugs were the same ones as when I bought the car 18 months ago. I saw no reason to change them. Maybe I dropped it and it had a hairline crack, maybe it was overheated. Maybe both. I’ll work on getting the head off this weekend.
    Or maybe a defective plug. For future reference... be aware of 'fake' high demand spark plugs, just in case.
    Tbd

  19. #69
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    Gents; compression tool in the hole eliminates the plug for lack of compression she burned away for a reason sadly probably related to anything above 14.7 AFR under load. This isn't a honda. Lean running under load will eat things quickly. Stainless aftermarket valves seem to go faster than factory sodium filled etc. Stock pistons, ring lands etc as examples. Could just be a gasket fail between cylinders at #4 who knows till open up.

    Ditto on counterfeit plugs though it's a real thing these days.
    88 M3
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    "If it flys, floats, or f*cks, rent it!"

  20. #70
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    I’m thinking the compression is zero because a chunk of the electrode is in the exhaust valve in #4. No visible coolant in down pipe, nor in oil. If the gasket failed between 3 and 4, wouldn’t 3 have shown little/no compression, too? I’ll have it open within a few days and will update. Good thing I’ve done this a few times, no big deal!

    Bigger question is: how to get air/fuel ratio correct throughout rpm range? As it says in the FAQs, minimum equipment to know situation is wideband o2 meter/gauge, vacuum canister from 240 turbo, and WUR from 240 turbo. 2 out of 3 right now, but I probably should not have run it with stock WUR. I have a volvo 240 turbo WUR (140-123 )on order from special-t auto in Texas. They are taking my spare WUR as a core.
    Last edited by Vermont320i; 12-31-2020 at 07:31 AM.

  21. #71
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    Quote Originally Posted by Vermont320i View Post
    I’m thinking the compression is zero because a chunk of the electrode is in the exhaust valve in #4. No visible coolant in down pipe, nor in oil. If the gasket failed between 3 and 4, wouldn’t 3 have shown little/no compression, too? I’ll have it open within a few days and will update. Good thing I’ve done this a few times, no big deal!

    Bigger question is: how to get air/fuel ratio correct throughout rpm range? As it says in the FAQs, minimum equipment to know situation is wideband o2 meter/gauge, vacuum canister from 240 turbo, and WUR from 240 turbo. 2 out of 3 right now, but I probably should not have run it with stock WUR. I have a volvo 240 turbo WUR (140-123 )on order from special-t auto in Texas. They are taking my spare WUR as a core.
    Correct on the compression assessment regarding head gasket between 3 and 4. You may even just have a valve adjustment that is too tight (wishful thinking). I'm not up to goal for info on the afr equipment.
    Tbd

  22. #72
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    Cant help you with the kjet tuning stuff, but i'd sure go rather rich. i think you will have a hard time to tune it properly on the kjet. i would go at least for 0,9 (lambda) under load with a boosted setup. 0,85 or even 0,8 is okay as well. i think just like with a carb turbo setup, you just have to accept that there will be no "perfect" tune.
    1982 E21 323i
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  23. #73
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    I’m sure I must have run too lean for too long. Ignorance has its price. Will post pics of top end tear down later this weekend.

  24. #74
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    Spark Plugs tell a story about what's happening in there. Sure hope you didn't throw them out already.
    Tbd

  25. #75
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    Nope, they are on a shelf in the shop. Just never had my phone there yet.

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