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Thread: 3800 Timing

  1. #1
    Tuner in Training
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    3800 Timing

    I've been tuning my 2000 Monte Carlo for the past two days, inculding MAF calibration, tuning the VE table, and further tuning of the VE table with the narrowband for low rpm drivability. I started tuning the spark table today after figuring out how to get the histogram working. What I don't know is how much timing is safe for the low end. IE under 3000 rpm and under 0.40g of cylinder airmass. The only way I know to street tune timing is to keep adding degrees until I hit knock, then dial it back. Which is what I've been doing for the top end. But I'm not getting any knock in the low end. The base map on a stock tune at 1400rpm and 0.36g airmass is 19*, I got all the way up to 32* without any knock. Am I going about tuning my base timing table wrong?

    Spark Tuning Step 9.1.hpl
    Spark Tuning Step 10.hpt
    02 Monte Stock.hpt

  2. #2
    Tuning Addict 5FDP's Avatar
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    Without a dyno you don't really know where power is stopping. On a stock camshaft and exhaust it's not making any more worthwhile horsepower past the mid 20's. Taking it into the 30's isn't doing you much. I'd stick to 24-28 degrees in the upper rpm cylinder airmass.

    I ran 35-45 degrees at cruising speeds and normal driving around area's. Then it sloped into the 20's and upper teens when I went into boost. Your NA engine won't have boost but the slope down as rpm/cylinder airmass rise is still going to happen. Get rid of that huge dip in your timing too. Then when you're done make sure to minus 4-5 degrees from the entire low octane table so it works like it should. Both table should not be equal as then it can't remove timing if it did knock.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
    Tuner in Training
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    Quote Originally Posted by 5FDP View Post
    Without a dyno you don't really know where power is stopping. On a stock camshaft and exhaust it's not making any more worthwhile horsepower past the mid 20's. Taking it into the 30's isn't doing you much. I'd stick to 24-28 degrees in the upper rpm cylinder airmass.

    I ran 35-45 degrees at cruising speeds and normal driving around area's. Then it sloped into the 20's and upper teens when I went into boost. Your NA engine won't have boost but the slope down as rpm/cylinder airmass rise is still going to happen. Get rid of that huge dip in your timing too. Then when you're done make sure to minus 4-5 degrees from the entire low octane table so it works like it should. Both table should not be equal as then it can't remove timing if it did knock.
    While watching some youtube videos on tuning, I may have found a way to get around not being on a dyno. Using (torque/rpm) * 5252, I can log horsepower. I know it wont be nearly as accurate as a dyno, but it may give me an idea as to where I stop making power with timing.

    But, I noticed when I went back to the tune file with the spark table I have been running for a long time, I was already getting some knock in the upper rpm. I have a 180* thermostat on the way vs the 195* thats stock, and I'm hoping that will get rid of most of my knock. After I get that installed, I'll have another go at spark tuning.

    The main reason I wanted to tune the spark table wasn't power up top, but throttle response down low. Also, while I am running a stock camshaft, I have the stock manifolds and crossover, but thats where it ends. I run a chopped downpipe, catless.

    Regarding your comment about the high/low octane tables. I'm very new to tuning. Is that how the ecm pulls timing? I thought the reason there's two tables labeled high/low octane was for different spark tables in relation to the octane of fuel being run. I run strictly 93.

    Using HP Tuners to log horsepower source:
    https://www.youtube.com/watch?v=CavfWIVoy-o&t=235s
    Last edited by WolvenScout; 05-13-2020 at 05:50 PM.

  4. #4
    Tuning Addict 5FDP's Avatar
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    The computer never knows what fuel is being ran through it. It's going to target the same fueling whether it's 87 octane or 93 octane.

    The timing tables are different from each other because if there is knock retard it can revert to the lower timing value to try and remove it. If you don't do that it could continue to knock. Say there is a knock event that pulls 4 degrees of timing but both tables are the same, it will take that 4 degrees away until the knock is gone but then slam that 4 degrees right back in and you could start a never ending cycle of knock. If the timing tables are different it can slowly feed the timing back in because it will pick a timing value using the knock learn factor.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.