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  1. #1
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    Bucking under boost?

    I have a 2000 M Coupe with an Active Autowerks intercooled OBD2 Stage 2 turbocharger system that will sometimes 'buck' under boost... usually when I back off the throttle to shift...ideas?

    I've also been getting a code reading on misfires. Nick at Technique Tuning has software that he says should eliminate the problem. Is anyone running Nick's sftware?

    Thanks much,
    Cole

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    VWBMW
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    Re: Bucking under boost?

    Divertor valve (if used) installed backwards or Blow Off Valve setting too loose?

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    Re: Bucking under boost?

    Thanks VWBMW, I'll get it checked out...c

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    just curious where are you located?


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    Re: just curious where are you located?

    I am in Minneapolis. The BMW dealer's tech and the locally respected BMW tuner are not turbo guys, they have really only worked with superchargers. Any ideas on who could dial it in? I've thought of shipping it off to AA in Florida since it is their system, but that's at least $1,500 on a good transporter and a month round trip.

    Any help or suggestions appreciated,
    Cole

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    m3boost
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    Re: just curious where are you located?

    Sounds like you're blowing out your spark..regap to .026

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    Re: Bucking under boost?

    Well, after two weeks in the shop (BMW dealer) my tech can not find the problem. He has talked it over with Active Auto countless times and all I got was a $500 bill...and he was very kind in the amount of hours billed compared to hours spent on my car. He and AA seem completely unable to solve this issue.

    I swapped a very good, bullet proof Dinan SC system for AA's in hopes of more power (as advertised and promoted). Over $16,000 later ($11,000.00 for AA's system plus the labor, and unsucessful continued trips back to try and get it right) and about 18 months of trying to get it installed, I have a car that drives like crap. At this point I can't afford to go back to the Dinan, I can't afford to go back to stock, and I can't afford to sell a car that i've put so much into that you now can't drive.

    I'm not going to flame them in this post. I think they must have good products, but I can't attest to that yet. I'm going to ask AA to help me make it right and work with me. They have seemed very helpful, but I'm still in a bad way and am at a deadend if they can't help.

    I will keep the FI board posted. Hopefully...soon good news and a sucess story. I'd love to write a glowing report telling you all how awesome AA and theirs products are!

    All the best,
    Cole

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    Re: Bucking under boost?

    If you are using the factory ECU, how are you programming your boost fuel circuit? Many times the piggyback method of boost fuel/ignition control creates conflicts, and they can be a never ending battle to hunt down and reprogram out...been there/done that with porsche carerra boost mapping problems, and this sounds oh so similar...

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    Re: Bucking under boost?

    Hello all,
    I apologize for not updating my post from 5 months ago, but it has taken that long to shake things out. I saw no other way to resolve my problems than to send the car to AA and let them sort it out. The only good covered transporter I found that would do a Minneapolis to Miami delivery cost $1,500.00 EACH way…but I was stuck. The car with at least 15K in modifications (complete suspension, heavy duty clutch, lightweight flywheel, custom differential mount upgrade, bigger custom radiator & oil cooler, etc., etc., etc.) and another 16K into the turbo system and it drove so poorly that I’d have a hard time selling it for 15K! So off it went in expectation that AA would get it right.

    Karl Hugh has been very good about staying in touch with me, and they have been working away for the last 2 months. That sounds incredibly long, but in their defense they got the car days before the Thanksgiving holiday, then their Dynamometer broke, then there are the Christmas and New Years holidays. And, I said I wanted them to drive it and really shake it down before putting it back on the trailer. At this point much time and money had gone into the car and I wanted to be sure it is right, a few extra weeks are fine with me

    I apologize for an extremely long post, but I am not technically able to give a concise and accurate evaluation of the process. And I'm guessing those whose eyes don't glaze over will enjoy digesting the process AA went through. (I omitted my input for brevity believing Karl’s reports are of more interest and enlightenment.)

    Karl’s reports have been:


    We did get the car yesterday, it is a nice car. So far we took it for a quick spin and even with the boost control off, the boost is still going past 15 psi!!! Did you know about this? Please email me a list of the problems you have so we can look it over methodically.


    Barry took the car out and did verify that the boost is overboosting so we took the car and put it on a lift to check the wastegate, it was rusted shut, not sure why, but the valve is all pitted and the housing is all rusty. We removed it and it is not really worth repairing, the shaft is too bad. We have ordered a new one already and should have it here by tomorrow. We will install it and then go from there. I will let you know more after we install the new one and do some more testing.


    We have the new wastegate installed already and that is fine now, we can control boost, we are having a small misfire and we suspect spark plug or spark plug gaps too big? We will have the car in the shop again tomorrow and we will have more information for you by Tomorrow or Wednesday. We are hoping to have it on the dyno for the testing, that way we can check air to fuel, boost, HP T etc.


    During a tuning session we had a fuel delivery problem and found that as we passed 11 psi we started to have fuel pressure fall off. We removed the passenger seat and removed the fuel pump, we installed a higher volume one and that is fine now. We then strapped the car down on the dyno once more and the power is good, but again we have a problem when we pass the 12 psi boost mark, the HP and T takes a nose dive, we discovered that the catalytic converters are partially clogged and so as we move more air and exhaust flow we now have a choking problem in the exhaust. So far the rear wheel HP is around 310 at 11 psi and we hit 350 at 14 psi but nose dives after 5000 RPM. The car is back off the dyno. I need to know what you want me to do from here.


    (On my approval they replaced them with high flow cats.)


    The car is on the dyno now, we seem to be having a small knocking problem or something with the knock sensors, the power is not bad but the curves are not smooth and slightly up and down. Will know more by tomorrow. Low boost ~10 psi is making ~315 rwhp.


    HI Cole,
    I have some questions:
    1) do you have any other cams in the car that are not stock?
    2) was any other work done on the car engine
    3) Is the Schrick intake manifold extrude honed?
    4) Any Specific Dinan mods on the motor or fuel system?
    We have been experiencing a nasty dip in power between 5K and 6K, and then the power comes back up. We checked a ton of stuff and we could not find anything wrong, so we did the basic tests, compression, cam timing etc.
    Compression is very even at 120 psi (a bit low to me, I expected to see maybe 140-145), so I am thinking that you may have some high lift high duration cams in there?
    I did some custom tuning on the ignition maps for this lower compression and I was able to get that nasty dip out, this is ok, but it bugs me that maybe there are some high duration cams in the motor? Please answer the questions above so I can have a better understanding of what I need to do.


    (There were no engine or cam modifications other than an AA supplied head gasket to lower the compression, AA supplied fuel injectors, and a Schrick intake manifold which as the installer said "don't think so but the ports were very smooth, while still showing evidence of sand-casting".)


    Ok Cole,
    I have attached the latest dyno runs from this morning. Look at the notes I made on it, this is the dip that we are trying to remove, but to no avail. I suspect that the dip is caused by the Schrick intake manifold, I have never tuned one with a Schrick intake manifold before. My recommendations is to install an OBDIM3 manifold, we have seen very good results with that. Other than an OBDI , we can only go back to a OBDII one, we will lose some top end power but will have very strong midrange and bottom end. I really cannot spend any more time on the car with the hardware the way it is, software cannot fix this dip, we have been trying all sorts of things in the last couple of weeks and no real luck. Power is good at peak ~ 359-360 rear wheel HP, which translates to around 440-450 flywheel HP. Call me if you want to discuss the chart



    OK Cole,
    the car is done, we found a used M50 intake manifold from 95 M3, made up the necessary brackets and connectors and installed it in the car, retuned the software and now we have it running very nicely. The car is a beast on the road!! We are in the process of making you a nice heat shield around the HFM. I will take it on the road again tomorrow to shake it down some more before we give you an OK to arrange shipping it back. I will also go over your bill and get you a copy with all the breakdown. Here is a dyno chart of the car on low boost 11 psi and high boost 15
    psi. This is rear wheel HP so to go to flywheel HP multiply by 1.29-1.31



    Thanks for everyone's suggestions and I'll post a final report once everything is worked out and I actually drive the car!

    All the best,
    Cole

    ps I will try to post the dyno charts next week, I'm currently traveling.

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    Re: Bucking under boost?

    If haven't checked for leaks, you might want to. My Alpina was doing a similar thing, and it turned out to be a crack in a coupler between the AFM and the cold air intake side of the turbo. Basically it was letting unmetered air in, burning lean and detonating. Best of luck resolving this...

    ---JT
    '89 635CSi
    '86 Alpina B7/1 Turbo Coupe, #72
    '99 528i Sport - wife's grocery getter

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    Re: Bucking under boost?

    I didn't see a post that you had resolved the problem, but here's another idea: too much fuel pressure. If you're still using the stock injectors, they may be hydrolocking at the point when you're ready to shift (under high boost). I've had the same problem with my car and it just takes a little tweaking of the fuel pressure to resolve and/or larger injectors.

    Jamie

    '86 TCD 535i euro
    '86 535i
    '87 535is
    '88 535i

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