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Thread: Tune Knock an Indication of Motor Health?

  1. #1

    Tune Knock an Indication of Motor Health?

    I'm about to put down a good chunk of change on an Evo 9. This particular one had its engine rebuilt and has a good list of accompanying mods. 1000 Injectors, S2 cams, forged rods, crank, pistons, headwork, i/c, i/c piping, exhaust w/ HFC, and FP red. The owner states that on his break in tune, he would get the occasional knock, indicated by the flashing of the engine light. This individual had since got a new tune, and states that it no long knocks- thus far. The motor at this point is only a couple thousand miles old. On the new tune, he states that it put down 300 on a Dynamic Dyno.

    Mind you, the tunes were done by reputable shops, ones that most guys on here have gotten their tunes from. With that being said, I feel that the knock on a tune that is supposed to be conservative for break in is questionable. In addition, on a retune with those mods listed above, even on 91 pump, I feel that the engine should have been able to put down more. I worry that there is some issue with the engine; and that the tune had to be extra conservative to prevent knocking.

    What's your take on this situation. Any insight would be appreciated.

  2. #2
    Canyon Racer evo_jfa's Avatar
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    Simple, take the car with that reputable shop or another of your preference. it could be less expensive if the original shop retune it. Check motor compression, complete the retune and doubts cleared. No flashing CEL, low knock good within limit on the ECU counter, once you have a flashing CEL light, isn't good. If the motor run on a Dyno, he should do run a pull, which is not a good idea if the tune is complete.

    As additional validation test, have ready a oil change done by the same shop just after the retune, check for debris on the oil filter and you'll feel more confident.

  3. #3
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    Apex Hunter's Avatar
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    Get that thing over to a reputable Evo shop for a PPI if you are seriously considering the purchase, so they can give the car a good overall inspection, including the tune. Compression/leak down test to check mechanical health if they want.

    How many counts of knock is the CEL programmed to flash at? How many counts of knock are even in question here? Could be not so big a deal, or it could be a big deal. If the car is only seeing a couple of counts of knock under certain conditions, like after sitting in traffic and heat soaking the intercooler, or other conditions that would adversely affect the knock threshold, that'd be understandable. On the other hand, if conditions are good and it's seeing 5+ counts of knock when boost comes on, i'd be wondering about that tune and whatever else. Also, it wouldn't be the first time a knock sensor has picked up other sounds, not related to what is going on in the combustion chambers.

    When speaking about EFI tuning, I've found the term "conservative" to have a broader meaning than one might think sometimes. Seems like these days, everyone asks for a conservative tune, which is synonymous with "don't blow my shit up". No kidding? You want to drive your car home? I have a feeling most tuners take it with a grain of salt. Most people want to make the most power they can, safely. There you go.

  4. #4
    SoCalEvo.net Shop


    Mike W's Avatar
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    Either check it out at the shop that did all the work or at another shop. The cool kids always get the cars checked out before they buy them. The funny phone call is the one that goes "I just bought a used modded EVO and I want to get it checked out to see if it is any good" Ummm shouldn't you do that before you bought it? And if you had a perfect built EVO, why would you be selling it? Sure stuff in life comes up and that sucks and you need to sell the car you just finished. But be suspicious always. Compression test, stick a scope down in it to check out the cylinder walls, cut open the oil filter, run it on a known dyno. HAve someone that knows what a put together EVO is supposed to look like have a look and see if anything is on upside down or backwards. Missing clamps or other cheaped out things can be a sign that you need to dig deeper, How much ebay and fake JDM wannabe shit on a car tells a lot about the owner and priorities. Some built motors are just noisey. Not knowing what the light was set to and how loose it was all put together adds up to the light really meaning nothing for this story. How much would it be worth to you not to buy a half dead car?

    Mike W

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