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Why pull timing?

This is a discussion on Why pull timing? within the Nitrous forums, part of the LSx Technical Help Section category; I'm new to nitrous and trying to understand. As some of you know, I'm about to spray a measly 125 ...

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    Member RealLiveMD's Avatar
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    Why pull timing?

    I'm new to nitrous and trying to understand. As some of you know, I'm about to spray a measly 125 wet shot on my 400hp NA car. I'm using a standalone. If I get the A/f between 11.5-12 with the race fuel, what's the purpose of pulling some timing. I've heard 2 per 50hp= 5 degrees.

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    Member RealLiveMD's Avatar
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    33 peeks, no responses. Does anyone understand this stuff?

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    Senior Member mrr23's Avatar
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    not that much timing. on a stock timing table, i've run a 150 wet shot with no timing pulled. years ago i got a rule of thmb from NOS to pull 1* per 50hp and the first 50hp doesn't count.

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    Senior Member bills98ta's Avatar
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    I'm 26.5 with a 150 dry shot. No knock... I've bumped it up to 28, but didn't gain ET, so I went back down.

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    Junior Member Caribe's Avatar
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    Using a standalone with race gas with a 125 shot, I don't see why you would have to pull timing. Do you have a way to monitor KR(knock retard) on a run?

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    Member RealLiveMD's Avatar
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    I can put it on a dyno. for a few runs. With HP tuners plugged. It should pick up knock retard, right? After the install I'd planned to do a few runs on the dyno to dial in my a/f ratio anyway. Then, the plan was to always spray the same shot.

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    Junior Member jakesz28's Avatar
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    The reason to pull timing while spraying nitrous is with the increased cylinder pressure you don't need to ignite the fuel as early. If you did not pull timing and the ecm did not register knock and pull it for you, it can easily hurt performance from preignition.

    There also isn't a set afr ratio to shoot for. I would put a new set of plugs in it and make a pass or pull on the dyno shut it off and check the plugs. You want to plugs to be nice and clean. If you can see a tan or dark fuel ring on the porcelin it is to rich.

    As far as the 2 dgrees per 50hp. That is garbage. It was started off that way in the early years of nitrous use. But if you decide to spray larger shots and multiple stages that will get you in trouble real quick. It is not uncommon for a sbc running 36* timing N/A to pull the timing all the way back to 15* on a 300hp shot. By the 2* rule you would only have to pull 12* but I have ran it at 15* which is a 21* difference.

    Now that was a convention head motor. Once you go to a 18* to 12* head there are people that are only running 5-10* timing while spraying.


    This is just the way I would warn a person when it come to helping a new guy out. There are large numbers of people spraying with out pulling timing but there are times motors don't last

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    Member RealLiveMD's Avatar
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    Quote Originally Posted by jakesz28 View Post
    The reason to pull timing while spraying nitrous is with the increased cylinder pressure you don't need to ignite the fuel as early. If you did not pull timing and the ecm did not register knock and pull it for you, it can easily hurt performance from preignition.

    There also isn't a set afr ratio to shoot for. I would put a new set of plugs in it and make a pass or pull on the dyno shut it off and check the plugs. You want to plugs to be nice and clean. If you can see a tan or dark fuel ring on the porcelin it is to rich.

    As far as the 2 dgrees per 50hp. That is garbage. It was started off that way in the early years of nitrous use. But if you decide to spray larger shots and multiple stages that will get you in trouble real quick. It is not uncommon for a sbc running 36* timing N/A to pull the timing all the way back to 15* on a 300hp shot. By the 2* rule you would only have to pull 12* but I have ran it at 15* which is a 21* difference.

    Now that was a convention head motor. Once you go to a 18* to 12* head there are people that are only running 5-10* timing while spraying.


    This is just the way I would warn a person when it come to helping a new guy out. There are large numbers of people spraying with out pulling timing but there are times motors don't last
    Completely understood. My shop was telling me to just get an 11.5 ratio and it's all good. I never needed to check plugs. There is so much BS that shops can shoot you. That's why I appreciate you guys. The thing is, I can potentially pay for anything nitrous, but I hate to pay and get screwed. I want all the info I can get.

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