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Northstar Engines and System Technical Discussion Discussion, Nitrous A/F findings & questions. in Cadillac Engine Technical Discussion; Hey Guys, in an effort to get to understand this northstar better I've been playing with datalogging off the stock ...
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    wydopnthrtl's Avatar
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    Nitrous A/F findings & questions.

    Hey Guys, in an effort to get to understand this northstar better I've been playing with datalogging off the stock narrow band 02 sensors. Now I know you can't use them for actual WOT a/f numbers.. but it would seem to me you can use them for trends and to see if your richer/leaner than a previous log. No?

    Ok so last night I recorded a *no nitrous* run. A *35 shot* run and a *overly rich* run. (35 shot but with too big a fuel jet)

    The non nitous logs look identical to nearly every other car I've ever logged. But when shooting nitrous I'm confused as to why the readings are all over the place? At first I thought it might be fuel drop out. So on the third run I made it pig rich by putting too much fuel to it.

    Notes: all testing was on a 35 shot so as not to hurt anything should something go wrong.
    And each one of these data logs are very close to each other when it comes to a 1000rpm power brake and then going WOT up to 70mph.


    Rich






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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Nitrous A/F findings & questions.

    Probably a misfire. You might be running out of room on the stock ignition system. Did you close up the gaps on the plugs?

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    Re: Nitrous A/F findings & questions.

    Yep they are one range colder (NGK TR6s), I've cut the ground strap back to expose the spark more, and gapped them at 0.030".

    You may be right on this point. This weekend I'll pull them and put in a new set.

    Rich

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    chevelle is offline Cadillac Owners Enthusiast
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    Re: Nitrous A/F findings & questions.

    I really don't think you can make any sort of conclusions off those O2 sensors. They are basically just on/off switches. Anything richer than 14.65 will show 1 volt and anything leaner than 14.75 will show no volts so they are VERY "narrow" band. So narrow as to be useless for saying anything other than "rich" or "lean" of 14.7:1.

    Likely you are just seeing excess/unburned oxygen in the exhaust from a misfire when the O2 voltage drops.

    I haven't been following your NOS stuff but I assume this is a "plate" system at the throttle body...?? If so, then that would probably explain the apparent anomalies in the O2 readout. With the manifold design on the Northstar (large plenum, long runners, no heat) it is virtually impossible to get any sort of good fuel distribution from fuel induced with a plate system. You would get pretty good NOS distribution but you really need a port NOS system if you are using a wet system. Possibly bumping the fuel pressure artificially when the NOS is on would be a better way to put the extra fuel in....???

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Nitrous A/F findings & questions.

    Quote Originally Posted by chevelle View Post
    I haven't been following your NOS stuff but I assume this is a "plate" system at the throttle body...?? If so, then that would probably explain the apparent anomalies in the O2 readout. With the manifold design on the Northstar (large plenum, long runners, no heat) it is virtually impossible to get any sort of good fuel distribution from fuel induced with a plate system. You would get pretty good NOS distribution but you really need a port NOS system if you are using a wet system. Possibly bumping the fuel pressure artificially when the NOS is on would be a better way to put the extra fuel in....???

    Good points. I think you're referring to a dry kit in the last sentence there. The problem with the N* fuel injectors is they snap snut at 60(65?)psi. Barely 15% more flow, which would not be adequate for much more hp.

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    Re: Nitrous A/F findings & questions.

    Chev,

    Yes a direct port is best. With the caddy I'm just playing and learning. The full on DP setup is on my truck. (up to a 450shot )

    There is no plate on the caddy. It's a wet system and the injector is opposite of the IAT sensor. Otherwise the a/f would go nuts. Also, it's a pulsed system that ramps up the shot size over a programable time frame. ight now I'm shooting fuel first and ramping over 0.7 seconds on the above logs.

    Fuel drop out with the design of this intake is my biggest concern. That's why I went FAT on the last data log. Another way to tweak the N/fuel ratio is to lower bottle pressure. Upping fuel pressure can cause other problems that I'd rather not deal with.

    As far as distribution goes I did pull all 8 plugs. The two cylinders towards the drivers side were *slightly* leaner than the others. But not much at all.

    At this point I'm supposing the spark is weak and that this just is a flawed way of looking at it. I have a wideband and really ought to hook it up instead.

    Rich

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    chevelle is offline Cadillac Owners Enthusiast
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    Re: Nitrous A/F findings & questions.

    I doubt your spark is the problem. That system has plenty of voltage capability.

    From your description the NOS system is basically a plate style...just it has a single entry point for nitrous and fuel....right? A plate might actually be better if it could introduce the NOS and fuel in various spots around the plate perimeter. If it is a single point entry system then there is absolutely no question that there is a fuel distribution problem. There is no way you are going to put fuel into the tuned intake and get any sort of good distribution with a single point fuel entry NOS system. No way.

    When you mention bottle pressure I think you mean trying to affect the fuel delivery thru the wet portion of the system by lowering the nitrous pressure???

    I meant to change the fuel delivery with the engines OEM injector system. To increase fuel delivery to offset the requirement for the NOS you would increase the fuel pressure. This is possible to do by adding a bypass to the return fuel loop in the OEM system with a restriction in it and then blocking the return fuel with an additional solenoid when the NOS activates. Set it up so that the orificed bypass goes around the solenoid so that all the return fuel has to go thru the bypass (with the restriction) when the solenoid closes. Once you figure out the orifice sizes for the bypass this will bump the fuel pressure up in the OEM system and thus deliver more fuel directly thru the injectors so that it would be distributed properly.

    With this sort of experimenting I would definitely get colder plugs and clip the ground electrodes to prevent them from inducing preignition just to be on the safe side.

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Nitrous A/F findings & questions.

    Quote Originally Posted by chevelle View Post
    I meant to change the fuel delivery with the engines OEM injector system. To increase fuel delivery to offset the requirement for the NOS you would increase the fuel pressure.
    Again, you'd need to change your injectors to something that can handle higher pressures. The northstar injectors that I tested failed to open above 60-65psi.

    As for the nitrous nozzle, he posted this picture in another thread:


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    chevelle is offline Cadillac Owners Enthusiast
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    Re: Nitrous A/F findings & questions.

    There is still quite a bit to be gained by a step increase in fuel pressure in the OEM rail. Generally you can assume that the amount of fuel delivered will increase the same percentage as the pressure increase you create. If the stock fuel pressure is 50 PSI and you bump it to 60 then that is 20% more fuel which would account for about 60HP worth of dry NOS.

    No matter what "nozzle" is used there is no way to get adequate fuel distribution with a single point wet system using a highly tuned manifold like the Northstar has. Maybe if you injected propane as the supplemental fuel but not with gasoline.

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Nitrous A/F findings & questions.

    Quote Originally Posted by chevelle View Post
    There is still quite a bit to be gained by a step increase in fuel pressure in the OEM rail. Generally you can assume that the amount of fuel delivered will increase the same percentage as the pressure increase you create. If the stock fuel pressure is 50 PSI and you bump it to 60 then that is 20% more fuel which would account for about 60HP worth of dry NOS.
    It's flow through an orifice though, which is proportional to (P2^0.5/P1^0.5).. or in your example pressures, 9.5% more fuel, or maybe 30hp - if you wanted to run on the ragged edge of where the injectors could possibly slam shut during a WOT nitrous run.

    Quote Originally Posted by chevelle View Post
    No matter what "nozzle" is used there is no way to get adequate fuel distribution with a single point wet system using a highly tuned manifold like the Northstar has. Maybe if you injected propane as the supplemental fuel but not with gasoline.
    That's true, I thought we were talking about nitrous distribution, sorry. I think in any wet setup you'll see gasoline start to pool in the bottom of the manifold as an added problem.

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    Re: Nitrous A/F findings & questions.

    Quote Originally Posted by chevelle View Post
    No matter what "nozzle" is used there is no way to get adequate fuel distribution with a single point wet system using a highly tuned manifold like the Northstar has.
    I completely agree. And a plate would'nt be any better either. A plate would only allow for bigger droplets of fuel vs this pictured crossfire injector. Plates are inferior for inducing phase change which means the first 3ish seconds of nitrous flow the fuel and N02 are not mixing properly. And then you'd be spraying onto the IAT sensor anyway.

    As far as upping the fuel pressure I just am not interested in going that far with the caddy. My goal was to bust a 13.9 which I did with as small a shot as I could. It took a 100shot and supprisingly the motor needed to be hot too.

    IMO, this stuff is interesting. And if basic science is'nt considered a guy could get caught up in spraying bigger and bigger only to hurt the motor.

    I'll pull the plugs this weekend and give it another try.

    Rich

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    Re: Nitrous A/F findings & questions.

    wydopnthrtl, please continue to post more info on this experiment. It is very informative for use DYIers who would want to know more. chevelle and eldorado1 your contributions are priceless as well. Thanks.

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    Re: Nitrous A/F findings & questions.

    Update:

    I changed the plugs yesterday. Went to a set of Denso IT20s (very expensive plug) I happen to have a set laying around because that's what I'll be using next year in the truck. Anyway they are about the best plug you can buy with ultra good quality components. They are all gapped at 0.038" and man does it idle smoother. I have'nt data logged a run yet but I did put the 50shot jets in. And it's as smooth as silk off/on nitrous. Very noticably smoother than were the NGKTR6's.

    OK here are two vids of what the ractested kit does when it's ramping up the nitrous/fuel plume. The motor was'nt running so you'll notice the fuel spurting for a second and then stopping as there is no pressure to keep it going. The whole point here is to show how well the kit can ease into a shot and also how well the nozzle dispurses the plume. The ability to ramp up the shot size is easy on the low rpm loads.. and allows for bigger power up top where the higher rpms can cope with it.

    VIDEO 1 is a 1/2 second ramp up. And VIDEO 2 is a 3 second ramp up. And for what it's worth.. somewhere around a 1.2 -to- 1.5 second ramp is where you cannont feel the power coming on. Other than hearing the solinoids pulsing the only way you can tell is that the motor is revving quicker.

    Also here are some pics of the NGK TR6s I just took out. These plugs have 3-4k miles on them and about 35-40lbs of nitrous sprayed. Anywhere from a 35 shot to about ten 100shots. (as seen in the 13.95 video) They indicate a very well distributed heat (cylinder to cylinder). Better looking than were my previous plugs. However they look too clean. Almost new in fact. This means the burn/plug was too hot. Not lean mind you.. just too hot. Any hotter and you might start to see aluminum spalling on it. (aluminum from the piston) I'm not too sure.. but the small specs on them just might be a little aluminum? Not all had this and they did get knocked around a little. It might just be some dirt. Anyway, the solution is to run a colder plug and a slightly richer nitrous/fuel ratio. The next time at the track I'll run a 100 shot again but keep the bottle pressure down about 100 psi. It will lower the power a little.. but will keep the burn a little cooler for some added safety.






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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: Nitrous A/F findings & questions.

    Iridiums are well worth the money. How much were the denso's? IIRC the NGK TR7IX's are about $7 a piece.

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    Re: Nitrous A/F findings & questions.

    The last two deals I've gotten were exceptional. $50 factory direct and the other was a package deal with some COPs for the truck.

    Otherwise I usually pay about $90 for a set of eight.

    Hopefully on this eldo I'm done tuning and won't need to change these things for at least another 75k miles.

    About the only other thing I'd like to try is hooking up my wideband. If/when I do I'll data log and report what does what. (I want to get into that before running the truck anyway)

    Rich

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