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    Effects of ECU tuning...

    This thread is in response to some of the comments made in the "Jdm BP vs USDM BP" thread, which was unecessarily closed(note to mods: please don't close a thread that has useful information, even if there is bickering).

    I'm only going to comment on tuning and it's effects on a naturally aspirated engine, since the method in which FI tuning increases horsepower is mostly by increasting boost.

    First, everyone would be suprised at how much power is to be had from ECU tuning. You can take nearly any completely stock engine, and get 5-10hp(sometimes more) just from installing and tuning a stand-alone engine management system. You have to keep in mind that manufacturers consider fuel economy, reliability and emissions when setting base maps and tuning from the factory. Another factor is fuel quality; just from adding higher octane gas and tuning your ignition timing appropriately, large gains can be had. Mazda did not feel it was justified to require premium fuel to increase horsepower to 130 on the $13,000 BP powered Protegé.

    Most new cars, the 3rd Gen Protegés being the epitome of this, run pig rich at Wide Open Throttle(WOT). Upwards of 11:1 A/F ratios is common. Why? Because too rich is better than too lean, although they seem to have gone overboard. Best power is in the 12.5-13:1 area for an NA car(14.7:1, or stoichiometric, is best for complete combustion and around 16:1(or higher) for fuel economy), although every car will responsd differently. So if you lean out a completely stock 3rd gen with an FS-DE, I'd suspect a few horsepower would be the result. Because of the nature of OBDII equipted cars, these A/F issues are hard to tune around, which requires the need for a complete stand-alone(no piggybacks need apply).

    Although I never had my 93 GT on the wideband 5-wire A/F system at the shop where I dyno tune before modding it to check stock A/F ratios, so I can't comment on how rich we run from the factory. I do however know that adding more fuel on a stock BP will not make power; potentionally the contrary. After installing my RX7 AFM, I tuned the flapper-door tension so that it ran the smoothest. This turned out to be too rich. When I hit the dyno, as you can on my first dyno chart, I was 7whp down from the red curve. Power would go up as we would tighten the flapper door tension one click after every run, until the first run in which we lost power, in which we would go back to the previous setting and call it a day. So just adjusting A/F ratios, I went from being too rich and down 7whp, to being just right and up another 3whp(10 more than when I stepped in the door that day). The AFM has been a great tuning tool, as it allowed me to take advantage of my exhintake cam, and just through loosening the flapper door tension, we got 2whp during that dyno session.

    Ignition timing is the big gainer here with ECU tuning. If anyone has been following my build, you'd know I'm running an extreme amount of initial advance. When I did my baseline dyno run a couple years ago, it was 110.9whp. A great number for a baseline run of an engine that's supposed to have 125hp. The next dyno chart shows my exhaust already installed on the day we started tuning the ignition timing. For those who don't know, I'll explain how ignition timing makes power at the end of this post. We did the baseline run, then observed ignition timing. To my suprise, it was ALREADY set at 16° BTDC at idle. This explained my high baseline, so we did about 7 runs testing everything between 10° and 22°(it did not ping at 22°) initial advance. It turned out that best power was at 18°. On the dyno chart, it shows the difference between 16° and 18°; 1.3hp and .9lb-ft. Just from 2°. I don't have the chart that shows the difference between the stock 10° and 18°, but it equalled a 7whp difference. Which means that nearly everyone one of you with a BP is missing out on 7whp if you haven't already changed your ignition timing to 18° and started adding premium fuel. This last chart shows the difference between 14° and 18° to give you an idea of how much ignition timing makes a difference.

    In regards to the MP3, I'm going to assume that 3-5hp is due to ignition timing alone, and that more still could be made with a stand-alone, with another 3-5 to be made from fuelling adjustments.


    *Ideal ignition timing happens before the piston is even at Top Dead Centre on the way up the cylinder during the compression stroke. This is because the flame front takes time to propagate and by the time peak cylinder pressures occur, the piston is well past TDC and it's forces can be used to push the piston down the cylinder. By using higher octane fuel(which both burns more slowly and is more resistant to pre-ignition), you can create that spark sooner with the benefit being higher cylinder pressures, and therefore more power. Ideally, you want peak cylinder pressures to occur around 20° ATDC. Advancing ignition timing reaps diminishing rewards, since you will get to a point that peak cylinder pressure will happen when the piston and connecting rod are at TDC, doing no good for anything. OEM ignition curves are therefore very conservative to reduce pre-ignition and detonation which could occur when hot spots, carbon deposits, poor fuelling, overheating or the distributor being slightly off time.
    Attached Files

    #2
    Good info
    1992 black & white GTR's :
    http://www.wihandyman.com/forum/showthread.php?t=18023

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