tuning with water/meth inj, a/f ratios
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tuning with water/meth inj, a/f ratios

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    Default tuning with water/meth inj, a/f ratios

    anyone using water/meth injection with a boosted engine, what a/f ratio to shoot for when in use. i am at 11.5-1 off the injection, when it comes on it goes to 10.0-1 seems too rich, turning up the boost a few lbs seems to do little to the rich condition, motor is pump gas small block chevy, twin turbo blow thru carb, air water intercooled, also how much boost can be added to the tune up safely with the water/meth inj. currently at 10lbs 30deg timing. thanks
    
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    gn7
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    You have to remember that when you hit the injection, you are not adding one bit of extra air to burn the meth. NONE! How can it not go richer? Its impossible, and its impossible to correct. More FUEL means more AIR!
    You can only lean out the "off" injection carb mixture, which isn't all that wise. If you had EFI you could set it up to lean the EFI mixture out while on the meth injector. With a carb, it is what it is.

    Part of the idea behind the meth injection is to richen up the "in boost" mixture.



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    Senior Member ap67et10's Avatar
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    you are leaving a good chunk of power on the table if you are anywhere in the 10's. If you are only running 91 pump and meth I'd tune it a little more fat than I would a boosted setup on a race fuel mix or E85. I always shoot for right at 12.0:1 with E85 or Race fuel and end up in the 11.7-12.3 range. However for you the 11.5 is safe on 91 pump you could lean it out a little, and then you shoot for low to mid 11's with the Meth, so in the 11.0-11.6 range. Try to stay out of the 10's if you can, you are probably fine if you creep up into the 12's, but I wouldn't go much above 12.2-12.3 for 91 and meth . Also if you run the meth all the time you can probably add some timing, but before you blindly add, make sure you do some precision spark plug reading to find the heat mark on the strap.


    Andrew
    Last edited by ap67et10; 09-13-2012 at 02:11 PM.

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    If you are going to really get the power out of this setup you should lean out the no meth setup to get the with meth setup in the 11's. This means that you need to ensure you always run the meth when coming into boost though. That also means you must make sure you have enough in a tank where you don't run out. If you do run out, then it means bad things will happen.

    Andrew

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    yeah, would rather not take fuel away from the carb, i have burned up pistons in the past with adding timing so going to keep it on the safe side for now, also the carb seems to get richer when more boost is added, going to creep up on the boost a little more and see what happends with the
    a/f, maby i need a smaller nozzle for the meth inj? could prob take a few jet sizes out of the rear and
    still be plenty safe. so whats worse on the engine, more timing or more boost?

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    gn7
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    Quote Originally Posted by ap67et10 View Post
    If you are going to really get the power out of this setup you should lean out the no meth setup to get the with meth setup in the 11's. That also means you must make sure you have enough in a tank where you don't run out. If you do run out, then it means bad things will happen.

    Andrew
    Andrew, do you think its better to lean out the amount of water/meth that is injected, or lean out the mixture of meth to water ratio and keep the amount injected the same?
    Quote Originally Posted by brent b. View Post
    so whats worse on the engine, more timing or more boost?
    Neither hurt the engine. Its the dentonation that does. Either will bring it on. The engine doesn't know which was the cause. Its a balancing act. I'd stay away from adding timing because it doesn't seem to affect the WOT power the way boost does. You could probably back down to 28 and not notice much when WOT, but you may notice it at lower Rs and no boost.
    Depends were you spend most of you time. If you run WOT alot, you might like the boost up with less timing, or the other way if you spend alot of time at part throttle low boost.

    A good timing computer lets you have both worlds.



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    Last edited by gn7; 09-13-2012 at 03:03 PM.

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    it gets lazy on the bottom end below 28deg, prob going to increase boost and leave the timing alone for now. thanks for the input on my delemma! my mix is 50/50 now, i will keep an eye on the plugs and am shooting for 16-18lbs, hope it stays together!

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    What are you using to monitor knock? And how is your methanol system set up? What turns it on and when?

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    Last year I ran a blown gas set up with water/meth and nitrous

    565 chevy
    14-71 bds
    ais water meth kit at 50/50 mix
    8.6:1 static c/r
    27 timing

    I ran 10lbs of boost and a 250 hit of nitrous on 91 pump gas with this set up, water meth came on at 8 psi.

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    Quote Originally Posted by gn7 View Post
    Andrew, do you think its better to lean out the amount of water/meth that is injected, or lean out the mixture of meth to water ratio and keep the amount injected the same?


    Neither hurt the engine. Its the dentonation that does. Either will bring it on. The engine doesn't know which was the cause. Its a balancing act. I'd stay away from adding timing because it doesn't seem to affect the WOT power the way boost does. You could probably back down to 28 and not notice much when WOT, but you may notice it at lower Rs and no boost.
    Depends were you spend most of you time. If you run WOT alot, you might like the boost up with less timing, or the other way if you spend alot of time at part throttle low boost.

    A good timing computer lets you have both worlds.


    Well I think it has to do with what you asked....what are the main goals of this setup and how is it typically driven? If its a hot rod, and gets run like one, then the best thing to do would be to keep it at 50/50 mix and lean out the secondaries in the carb run the meth on a boost activated switch of your choice. Then tune the carb to hit 11.5-11.8 AFR with the meth and run the meth all the time while in boost.

    If its a little more of a cruiser, and gets used a bunch for cruising will just a little hot rodding, then I'd dumb the mixture down a little, maybe a 25% meth 75% water mix and then also reduce the percentage of mixture a little....it depends on how much hes putting in now though...then see how that does. If you need to pull just a tinny bit of jetting out of the secondaries to get the no meth a little closer to 12.1:1 and the with meth closer to 11.5:1 Then probably leave the timing alone and raise the boost a 3-4 psi. You could get away with running the meth on a switch that is just manually operated if you do it like this, since it would be good on just gas for the majority of the boost it sees and the meth would be needed above 9-10 psi for safety...however I just hate the idea of manual switches. I'd still much rather see an automatic switch of some sorts.

    If you want to add a whole bunch of boost....add more methanol....if you want to just be safe and add just a couple of pounds of boost, add more water. If you want 5-7 psi of boost for the top end and a couple degrees of timing to help the low end then run the 50/50 mix.

    In short, the methanol is best for cooling the charge, water is best to prevent knock....meth is fuel, water is not, so these ratios will screw with your AFR depending on how you mix them. That's why like GN7 asked....what do you want from the boat?

    Typically you can safely add a good 5-7 psi of boost on a 50/50 mix and a couple degrees of timing. This timing will definitely help your bottom end which is why I mentioned it, but as was mentioned, it doesn't help all that much with more boost. The boost is what gets you moving on the top end, the timing will just help mid range and out of boost running, so you could also buy a timing retard setup like GN7 mentioned.

    What is your compression ratio right now? It kind of matters because you may still have room for error if you are setup on 8:1 compression right now, but if you are 9:1 you are on the edge already with 10lbs.


    Andrew
    Last edited by ap67et10; 09-13-2012 at 05:31 PM.

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    Default E85

    Why don't you guys with boost just run E85 straight up. I would think it would be cheaper to run than 91 and meth inj.
    couldn't you just set the engine up for high boost. Or is E85 what you are using for Meth?
    Just a question from someone that doesn't know much about boosted engines other than my diesel truck.

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    Just to clarify GN7, if he doesn't want to get a bunch more out of it, I'd both dumb down the mixture and the percentage. Adding water means you can also reduce the percentage you are inserting and still retain the knock control. You loose the charge cooling which is huge for the bigger boost gains, but is safe to add a few psi.

    If he wants to run it hard, I'd stay at 50/50 mix and run the percentage the same, but reduce the 91 fuel through the carb and use meth all the time during boost.


    Andrew

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    Quote Originally Posted by Tinkerer View Post
    Why don't you guys with boost just run E85 straight up. I would think it would be cheaper to run than 91 and meth inj.
    couldn't you just set the engine up for high boost. Or is E85 what you are using for Meth?
    Just a question from someone that doesn't know much about boosted engines other than my diesel truck.

    if you can get E85 to run in your meth injection, you are stupid....since as you mentioned it is way better and easier to just run E85 and no injection. If he's running meth injection its 50% water 50% methanol. Most people choose meth because they don't have E85 near them, or it just isn't as readily available as they would like. I do agree though...E85 as a fuel, ditch the injection and turn the boost to the moon!


    Andrew

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    gn7
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    Quote Originally Posted by ap67et10 View Post
    Just to clarify GN7, if he doesn't want to get a bunch more out of it, I'd both dumb down the mixture and the percentage. Adding water means you can also reduce the percentage you are inserting and still retain the knock control. You loose the charge cooling which is huge for the bigger boost gains, but is safe to add a few psi.

    If he wants to run it hard, I'd stay at 50/50 mix and run the percentage the same, but reduce the 91 fuel through the carb and use meth all the time during boost.


    Andrew
    Thanks



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