nitrous on a blower motor

Discussion in 'PSI Superchargers Tech Questions' started by blownmudrail, May 13, 2009.

  1. blownmudrail

    blownmudrail New Member

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    i have a blown sbc and wondering about nitrous to cool the charge? is there any ratio on shot of nitrous verses how cool the air will become?
    ex 250 shot nitrous= 75 degrees air change?
    and when you change the air temp can you speed the blower up more?
    want the nitrous on a hand operated solinoid can i heat the air up over 130* and then use the nitrous to cool it back off?
     
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  2. mark6052

    mark6052 Member

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    blown and nitrous =

    :eek::eek: there are reasons why its not allowed in dragracing. BOOM comes to mind. unless you are really rich, very smart, and know a tech at one of the nitrous outfits. dont. if you cant build enough HP with what you have build a bigger engine. sbc are cute but get real.
     
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  3. GregM784

    GregM784 Member

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  4. GregM784

    GregM784 Member

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    Using nitrous will affect a/f ratio, same as upping the blower. What fuel do you run?
     
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  5. mbaker3

    mbaker3 New Member

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    Never tried it but I would think that because you are putting more oxygen into the mix with the Nitrous, you would have to back off the blower to compensate in the A/F ratio and resulting cylinder pressure. So would you really be increasing the HP? Hmmmmmmm, can't wait to hear from someone that knows.
     
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  6. Ken Sitko

    Ken Sitko Super Comp

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    There have been a few prominent top alcohol guys that tried the nitrous deal years ago as sort of a development project, or even possibly making the step up to top fuel using alcohol and nitrous. From what I heard, it was near impossible to get a smooth transition; when the nitrous kicked in, the tires broke loose hard. Lots of time and money was spent, so I don't think you want to go down that road.

    Ken Sitko
    Sitko Family Racing TAFC
     
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  7. mark6052

    mark6052 Member

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    maybe trying an intercooler would be a safer way to go. I believe BDS used to sell them I assume there are others. less complicated, does the same affect. then you dont have to chase the extra fuel needed to compinsate for the nos. go lean and BOOM.
     
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  8. JRB

    JRB Guest

    I know of a few pro mod guys who have used Nitrous. On Blown alcohol stuff. Both Roots and Screw. It is very instantaneous when it hits, obviously, but it does tend to wake the car up quite a bit. You just need to be really smart when it come to bringing it on. There are quite a few things to take into account for.
     
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  9. Bottlefed

    Bottlefed New to Blowers

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    Is this motor on gasoline? I knew a couple of guys running nitrous with gas on blowers to cool the charge back in the day, if its alky the hat nozzles usually do a good enough job on there own.

    As far using the alky nitrous combo to allow you to burn more fuel and generate more power, shocking the tires should not be a problem these days. You can get nitrous controllers that will duty cylcle the nitrous and fuel solenoids anywhere from 10% to 100% on whatever timer or throttle based setting you desire.

    Then you are on to the other problem, back in the day everyone thought that lean nitrous to fuel mixtures burned up motors. Over time everyone has come to find that excess fuel and timing is what usually causes problems. What happens is that someone has too much timing and an excessivly rich mixture, the extra fuel keeps it from detonating then when you pull fuel to lean on the tune-up it detonates and lifts a ring land allowing oil into the chamber which burns causing combusiton chamber temps to skyrocket and melt the pistons then a lean condition gets the blame. Conversly with the same overfueled and overtimed engine if you pull timing then the extra fuel washes the rings which also causes the rings to drag and lets oil into the chamber causing the same burndown that gets blamed on the motor being lean. These days when you are setting up a nitrous motor you calculate (or flow) the nitrous fuel ratio that you want then pull a fair amount of extra timing and read the plugs and continue to lean the mixture till you either just barely have a light hydrocarbon ring or none at all (depending on who is tuning) then you slowly feed timing back in a degree at a time until the performance increase starts to wane.

    I have put in the long winded nitrous speech because on a blown injected alky motor you usually have way more alky (to cool the mixture) than you need from a combustion standpoint, on a motor that does not have the oxygen rich chamber conditions of nitrous oxide its not a problem (for the rings) but on this sort of setup tuning nitrous will probably be a real pain and lifted rings and detonation will probably be pretty common, the only advice I could offer is to go real easy on the timing.

    PS I agree completely with what Ken said, take the road more travelled and improve your setup by conventional means.
     
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    Last edited: May 14, 2009
  10. JNJ

    JNJ New Member

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    I have used NOS fogger plate on my blown SBC with a 6-71 2% - 8% over and used 116 oct race gas carbed. We used a progressive nos controller and only had it set on 20% to do exactly what an intercooler would do, cool the air intake charge. It picked up our motor at least 150HP on the dyno if I remember correctly. We did have a few booms from leaning it out and had to have the blower repaired several times.

    You can see some videos of it on the dyno at my website at www.jnjdragracing.com, we did however tear up pistons etc until we got the right tune.

    Since then I have switched to Alky with a enderle bird and will never go back to race gas / nitrous on my engine.

    John
     
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  11. Bottlefed

    Bottlefed New to Blowers

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    Mudrail,

    I think most of the power increase of nitrous through a blower is due to the oxygen in the combustion chamber not the cooling effect. The amount of charge cooling would be dependent on the amount of nitrous vaporized in the intake vs the amount/density of air entering the motor so its kinda hard to give an exact answer.

    But unless my math is way off this should be close, Nitrous Oxides latent heat of vaporization is roughly 160 btu per pound compared to alcohol at 473 btu per pound so even though the boiling point is 127degrees below zero you would probably need to inject twice as many pounds per hour of nitrous as alcohol to get the same cooling of the intake charge. If my memory serves me correctly, a 400 hp nitrous kit flows around .5 pounds per second. A 1500 hp blown motor can have 1 lb per second of alky flowing through the hat nozzles, so to get the same cooling effect you would need to put 2 lbs per second or 1600 hp worth of nitrous to achieve the same cooling effect.
     
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  12. blownmudrail

    blownmudrail New Member

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    i have seen it work wonders on some of the blown alcohol motors in mud racing, was just trying to see what you guys thought of it. thanks for some of the answers that were honest, some were redicilious. jeremy
     
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  13. RUGSTER

    RUGSTER New Member

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    Nitrous on Blower motor!

    Jeremy,i can't see a "redicilious" post anywhere!:rolleyes:But there's plenty of in depth answers from guys that have blown up way more than you and me.:D
     
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