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Thread: M30 chip options that don't require premium fuel/don't throw a CEL?

  1. #1
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    M30 chip options that don't require premium fuel/don't throw a CEL?

    Hi all. Wondering if there is a good EPROM chip option for my '90 735i with a 179 ECU number that still allows me to use 87 octane and does not throw a check engine light. Shogun's chip hit all the right marks...slightly better fuel economy, more performance, while not requiring higher octane. The only problem was that the check sum number was different for my US spec E32, which caused my check engine light to remain on. Any recommendations? Thanks!

  2. #2
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    Just received the 2 chips back I sent you, thanks for testing them both on your car. Checked them immy, no fault compared to the master and others. Looks like the problem is that my chips are made and based on EURO spec cars and these do not have CEL. So most probably the checksum is different. Maybe your built year/month original chip is slightly different than others, which I sent to US and they did not tell me of any probs. But these were different production months/years M30.
    Maybe easiest is you get a chip made for US version, demand for M30 chips is low nowadays and to make an extra version only for you is too much work and I would also need the original chip to compare.
    Shogun tricks and tips for the E32 series are HERE!

  3. #3
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    Thanks for double checking the chips, Shogun. Glad they both returned to you quickly.

  4. #4
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    Chips have NOTHING to do with octane. The fuel you need is based on the compression ratio of the engine. Octane ratings are about fuel stability under compression. The higher the compression engine, the higher the octane needed. But there is no much miss-information out there that people consider it fact that somehow chips can change the physics of an engine. Always use the fuel required for the engine you have.

    Fun fact, E85 fuel is 108-110 octane.
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  5. #5
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    But doesn't the advance in spark timing that is common with chips for our cars often require a higher octane to avoid detonation? The spark is occurring earlier (before the piston reaches TDC) and thus a slower burning fuel (higher octane) is needed ¯\_(ツ)_/¯

  6. #6
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    M30 engine does not have knock sensors like the M60, where the timing can be adjusted/retarded by the DME. The knock sensors are used only to retard ignition timing if knock is detected.
    The M1.1 and M1.3 for the M30 engine are very old, basically the M1.3 can store more faults than the M1.1, they are interchangeable for the M30. The original DME M1.1 and 1.3 were designed in such a way, that there were no problems worldwide and with a big safety reserve to cover all eventualities like extreme high altitudes in the mountains, extreme climates and worst fuel available in those days more than 30 years ago throughout the world.
    The vintage DME (Mo-tronic) is very simple and only controls injection and ignition, that is why they have been called Digital Motor Electronics. In contrast there is the even older Je-tronic, which ONLY controls the injection. The injection duration and the ignition angle are stored in maps and are retrieved depending on the speed and accelerator pedal position, nothing more. Cold running factors, temperature-dependent idle RPM, etc. are retrieved from a characteristic curve. The motronic can not do more than regulate ignition and injection, what else should I change if there is not any more?
    Thus, during chiptuning of these ancient DMEs, only the moment of ignition and injection are changed = slightly more horsepower, better torque curve. These parameters are changed:
    Ignition at: idling + partial load + full load,
    Injection at: idling + partial load + full load


    Here an interesting discussion: Changing spark timing to use a lower octane fuel? https://mechanics.stackexchange.com/...er-octane-fuel
    Shogun tricks and tips for the E32 series are HERE!

  7. #7
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    Quote Originally Posted by schnell944 View Post
    But doesn't the advance in spark timing that is common with chips for our cars often require a higher octane to avoid detonation? The spark is occurring earlier (before the piston reaches TDC) and thus a slower burning fuel (higher octane) is needed ¯\_(ツ)_/¯
    Not really. Detonation is detonation. There is no such thing as a slower burn, at least not at the scale we are talking about here. If anything, detonation happening even earlier before TDC would let you use a lower octane and the compression ratio is lowered. But you are still reaching full compression at TDC.
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  8. #8
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    You are confusing detonation and the controlled burn initiated by the firing of the sparkplug. Detonation is unwanted behaviour of gas mixtures under pressure where pockets of gas can self-ignite causing destructive pressure waves (known as knocking, pinking or pinging).

    Although the compression ratio has an affect on the propensity to detonate, the pressure produced by the wave-front of burning fuel has a much greater bearing. Higher Octane fuels have a better resistance to detonation (but interestingly, less latent energy) and in the UK the rating at the pumps is the fuels Anti-Knock Index (AKI) and not its Octane.

    What has this to do with ignition timing? Well, it has a great deal as the earlier the ignition timing (within limits) the higher the resultant cylinder pressure. The higher the cylinder pressure the more chemical energy is converted to mechanical energy. Higher cylinder pressures require fuels with a higher AKI.

    With no way to test if the engine is suffering from detonation, the ignition timing has to be retarded to a point where pre-ignition is unlikely to occur - and so less power is produced from exactly the same engine running on a higher AKI fuel with timing that is further advanced. This is why knock sensors were introduced on the M60 V8 - these engines can run on low AKI fuels but can also run on higher AKI fuels by slowly advancing the spark timing to the onset of detonation. Where lower AKI fuels are used the same system retards the ignition timing using the same method.

    M30 and M70 engines do not have knock sensors so their ignition timing is set to a point where lower AKI fuels do not detonate - and thus produce less power than would be available with higher AKI fuel and more advanced timing.

    This is the reason for the OP's question - do any chip sets that alter the ignition timing operate correctly on low AKI fuels? A chip set that does not advance the timing is not utilising the engine to its full potential so it is a relevant question!
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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