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Discussion Nitrous Oxide

Discussion in 'The Pub' started by Frankster, Jun 3, 2021.

  1. Frankster

    Frankster "Play stupid games, win stupid prizes" Staff Member Premium Member Ride and Events Crew

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    Just wondering if anyone on here has ever used a Nitrous Oxide kit on a small capacity 4-cyl engine like a ZXR250? Seems that most kits are for fuel injected motors and all seem to be for large capacity motorcycles. I've seen those rubbish 6sigma kits used on single-cylinder motorized bicycles, but I'm after something for multiple carbs.

    https://www.ebay.com/itm/170399789492?hash=item27ac9e71b4:g:4O8AAMXQ-KRRh0Bv
     
  2. gregt

    gregt Well-Known Member Premium Member

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    My experience is with nitro fuels in carbs. Which is fun.

    As I understand NO2, you've got to increase the fuel supply when on the gas. This is very hard to arrange on carbs.
    EFI on the other hand lends itself to this well.
     
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  3. Andych

    Andych Senior Member Premium Member

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    No real experience with NOS but.... being an avid Street Outlaws fan..... apparently NOS drag cars suffer many more piston melts when trying to get similar power to high boost turbo or Pro charger cars... fuel and also timing control would be critical I guess.
    Much easier in a car with the ignition systems etc they run. They are constantly changing tunes depending on the road surface, ambient temp, etc.
    Might be a touch more difficult with a bike....
     
  4. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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  5. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    We need a bonkers post emoticon - this one qualifies :prankster: - but on what Greg has said, and I could be totally off target with this, what about a power jets which are operated by a solenoid - would you even be able to use the choke circuit for that - it could go VROOM or it could go BOOM
     
  6. Murdo

    Murdo The Good Doctor Staff Member Contributing Member Ride and Events Crew

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    If you have a look at the kit shown above it includes the high pressure fuel pump, twin nozzles for fuel and gas and solinoids to supply both.
    The system works by injecting the gas plus the extra fuel required through the nozzles straight into the inlet port after the carbs, so carburation is not effected when off the NO2. This is usually set up to work off micro switches connected to the throttle linkage.
    So, come to start line, switch on master switch to activate relays and arm the system, when lights go green and full throttle is applied the switches contact and relays open/close to activate the nozzles allowing gas and extra fuel into cylinders. Sounds simple but getting the right amount of gas and fuel, plus retarding the timing to stop detonation is a balancing act that takes a lot of burnt pistons to get right. I consider this far too complicated to be bothered with on a bike, just get bigger bike if you want to go faster.
     
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  7. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    I should have actually looked at the ebay listing

    Nothing I'd ever even consider undertaking even as a thought experiment - it's just pure headache material, but this is an interesting read
    https://www.enginebuildermag.com/2012/12/nitrous-its-naughty-and-nice/
     
  8. Frankster

    Frankster "Play stupid games, win stupid prizes" Staff Member Premium Member Ride and Events Crew

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    I was looking at NOS as a 'simple' way to get a few extra ponies out of the 2fiftycc drag bike. If it was a single cylinder engine, then it might be a workable solution to have a quick way to give the engine a shot of NOS during the run, but 4 cylinders and carbs seems way too hard for me.

    Thanks for everyone's comments and Mr. Murdo for his, as always, detailed analysis. As Murdo and a few others know, my finances don't allow me to think about burning pistons, so I'm going to park the NO2 thought and change direction to what @gregt mentioned in his post. I was also looking at running Alcohol (methanol) fuel which 'only' requires jetting changes, but this fuel is corrosive, so again not too keen on causing large scale damage to my engine(s).

    My 'experience' with Nitromethane is limited to running some in my RC (Remote Control) car when I was much younger and having been around Nitro-powered engines at the drags since Noah was a boy. I know people run Nitro with carbs on the salt and that if it's done right then you get a nice power increase. The Afflick family run small (10-40%) loads in their world record small capacity bikes, but I'm pretty sure they run FCR type carbs and not CV carbs like I do. So, @gregt feel free to post anything that you think might persuade or dissuade me from going down this route for either drag racing or WOT runs on the salt.

    Once again, thanks for everyone's comments/feedback and that engine building mag link @ruckusman & here's a 'bonkers' emoji you can use for my next crazy post.

    Bonkers Emoji.jpg
     
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  9. jmw76

    jmw76 Well-Known Member Premium Member

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    You could try E85 fuel. The V8 supercar guys get more power out of this than super unleaded.
    Again you need a jetting change and you need to ensure your fuel system components are compatible with it.
    A simple solution is to make sure you do not store your bike with any fuel in it. Just dump it after an event.

    My little race car, GSXR1100 powered, was originally set up to run on Methanol (previous owner). There are no special components in the system. I have always run it on high octane petrol. I only have a small tank and any improvement in power is quickly offset by reduced range for circuit work. The 140 jets I use need to be changed for 220 for methanol.
    With my current tank, I can just squeeze out 8 - 10 laps of Philip Island at a sprint meeting on unleaded petrol or Avgas.
     
  10. gregt

    gregt Well-Known Member Premium Member

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    We went through the fuel thing here when our F3 roadrace class came in late 80's.
    There were a few F2's running alcohol and even nitro but no F1's at the time. F3 was a natural for fuel wars.
    400 fours 500 twins and unlimited singles. Using alcohol in the twins and singles levelled the playing field
    of piston area vs bike weight. I was involved with the first five years winner. I sorted his fuel in the first year when he ran a GSXR400. Then built him an EX500 which ran on alky and won the next two years. In the second year of that bike he ran up to 25% nitro with our alky base.
    Then the game changed. Kawasaki got him to change to the ZX4. One of those on nitro was untouchable. The twins and singles couldn't cope. Even my supercharged twin couldn't.
    Then the biggest change. Petrol only. The singles and twins were gone.

    E85 has if anything, slightly less calorific value than Methanol. It's not a huge power gain in itself. Like all alcohols it's the gains from a denser, cooler charge that you see. As i've pointed out above, this becomes more apparent as you go to bigger bores.
    I've run a customer 250 Kawasaki four on alcohol. Yes, it ran cooler but I'd doubt it made more power. With bore sizes this small, you can squeeze compressions up to seriously high figures without detonation on petrol.

    Murdo - the guy who won F3 here for I think 5 years running was Tony McMurdo. Coincidence - or are all of the breed free thinkers ?
     
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  11. jmw76

    jmw76 Well-Known Member Premium Member

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    Incidentally, I run a 13:1 compression ratio on my 81mm bore GSXR1216 normally aspirated motor.
    No detonation issues.
     
  12. Frankster

    Frankster "Play stupid games, win stupid prizes" Staff Member Premium Member Ride and Events Crew

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    I've run a customer 250 Kawasaki four on alcohol. Yes, it ran cooler but I'd doubt it made more power.

    Well, in that case, there's no point in going down that path.

    With bore sizes this small, you can squeeze compressions up to seriously high figures without detonation on petrol.

    So, you're suggestion is to raise compression and leave the bike on pump petrol to gain more power?

    Murdo - the guy who won F3 here for I think 5 years running was Tony McMurdo. Coincidence - or are all of the breed free thinkers?

    Pretty sure our Murdo isn't related to Tony, but you never know.

    @jmw76 I'll give you a call tomorrow. Can't visit due to this lockdown, but at least I can pick your brain about what you've posted.
    @gregt So, my thought of running a small amount of nitro in the bike with CV carbs? These engines make 45hp from the factory. I've seen Dyno sheets for a ZXR250 showing 52HP. That engine had a lightened crank, smaller main jets (#110 instead of #125 & #128) and no filter in its airbox.
     
  13. gregt

    gregt Well-Known Member Premium Member

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    First close up the squish. With this stroke, about .032in should be OK. Deck the block to get it right.
    I don't know about aussie petrol but 100 octane is available at the pump here and the MNZ Tech steward has tested it and it's equivalent to FIM 100 unleaded. High in aromatics which means we can compress it to the moon.
    Back in the 750/4 WSB era, TKA were running the ZX7's at around 14:1 on the supplied fuel.

    The F3's here on nitro were using slide type carbs. CV's have a nasty habit of melting the diaphragms.
    Also most CV's of this era have plastic floats - they won't stand methanol either.

    From observation, I'd doubt if lightening the crank does very much. Finishing it properly and clearancing the bottom end will gain you more. They're better than the FZR cranks - but still worth doing properly.

    Dialling the cams in is also worth doing. I can't remember what OE was on the one I did - but it finished up on 103/104 lobe centers. Which worked quite well. The downdraft heads like close lobe centers.
     
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  14. Frankster

    Frankster "Play stupid games, win stupid prizes" Staff Member Premium Member Ride and Events Crew

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    First close up the squish. With this stroke, about .032in should be OK. Deck the block to get it right.

    0.032inches is 0.8128mm, so I will see what it is as standard and then go to 0.82mm. Is this the area you said to 'deck'?

    Deck the block.jpg

    I don't know about aussie petrol.

    We have 98 octane at the pump. Should I get higher octane race fuel?

    The F3's here on nitro were using slide type carbs. CV's have a nasty habit of melting the diaphragms. Also most CV's of this era have plastic floats - they won't stand methanol either.

    Well, that's the end of that idea.

    Finishing the crank properly and clearancing the bottom end will gain you more.

    Sorry Greg, I'm not a mechanic, so not sure what that actually means. I can google it and read up about it, but if you have any 'how to' information, then it would be greatly appreciated.

    Dialling the cams in is also worth doing. I can't remember what OE was on the one I did - but it finished up on 103/104 lobe centers. Which worked quite well.

    I have set valve clearances on my bike, so I have some experience in this area, but I don't understand what 'dialing the cams in' actually means. The cams have marks in them to set them correctly when putting the top end back together after changing shims and the timing wheel has no option to 'move it' and change the timing. One of the forum members in the USA was going to make up some modified timing wheels, but I'm not sure if he ever did it. The engine is just for drag racing, so WOT only.

    The downdraft heads like close lobe centers.

    More details please. What about porting, blueprinting? Thanks for your help and sorry for the barrage of questions.
     
  15. jmw76

    jmw76 Well-Known Member Premium Member

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    @Frankster to dial the cams in you need slotted cam sprockets so that you can move the position relative to the cam. You will need a good degree wheel and a dial indicator to do this properly. It is a fairly involved process. I have played around with the cam timing on my race car a bit. You can essentially move the peak torque and power points up and down the rev range a bit. You will loose in some aears and gain in others. You might not actually get a lot of benefit. Lots of trial and error with different timing to get it where you want. You need to be careful with timing numbers as you can get valve to piston contact under some circumstances. Made worse when you see eck the block.

    Is there a cylinder block assembly that bolts up to the upper crankcase half you have highlighted? Usually you just skim the top of the cylinder block. The face that the cylinder head mates with.

    I never go bellow 1mm for safety. If you get witness marks on the tops of your pistons, you have gone to far.

    You will need to assemble the motor and measure the deck height first on all cylinders, before making changes.

    Peter.
     
  16. gregt

    gregt Well-Known Member Premium Member

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    There's been some discussion on here about FZR250 cranks and the poorly finished oil holes. That's relevant here too.
    That work is what I mean by sorting the bottom end.
    Yes, skim the top of the cylinder block to get the squish right. The figure I quoted of .032in is safe with this very short stroke and light pistons. When you measure the existing squish, be sure to bolt the barrel down on the cases - with base gasket.
    The one I did, had the pressed on cam sprockets as you quote. From memory - it was a long time ago - I measured the OE timing and removed at least one sprocket and pressed it back on where I wanted it.
    Yes, it's possible to convert them to bolt-on while you're in there. Dialling in is one of those things covered in several online vids and articles. I've been doing it since the early 1970's and tend to assume everyone knows how.
    Naturally, once the cam timing is where you want it, you'll plasticene the valve pockets, reassemble and turn it over slowly by hand. Lift the head again and cut the plasticine to see what your valve to piston clearance is. With valves this small and light you could go as close as .030in IMO. I'd pick that even with a skimmed head it will be bigger than this. You're only running stock cams right ?
    Porting - yes, a cleanup won't hurt. Get the shortside radius right on the inlets first. They're not bad as stock.
     
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  17. jmw76

    jmw76 Well-Known Member Premium Member

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    I forgot to mention. When you start adjusting the deck height, the cam timing will move as the cam chain length is essentially fixed. There might need to be some minor degreeing adjustment just to get back to the stock numbers. Sorry, I wasn't aware that the cam gears were pressed on.
     
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  18. Frankster

    Frankster "Play stupid games, win stupid prizes" Staff Member Premium Member Ride and Events Crew

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    You're only running stock cams right?

    Yes, everything is stock.

    @jmw76 thanks for your input.
     
  19. ruckusman

    ruckusman White Mans Magic Master Premium Member Dirty Wheel Club

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    I read somewhere, an interesting technique - to test the valve to piston clearance, wind the engine through and exert pressure onto the top of the valves so that they touch the piston then use a feeler gauge to see how much clearance there is

    That obviously isn't an alternative to using plasticine to know where to remove material, but would be a logical first step to see if you need to disassemble and use plasticine
     
  20. gregt

    gregt Well-Known Member Premium Member

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    You can - and I do - use this method with lever type valve gear. i put a dial gauge on the valve stem and measure valve to piston over the range 20 - 5 degrees before and after TDC.
    With bucket and shim it's pretty well impossible - so plasticene or modelling clay is the only accurate way of doing it.
     
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