Discussion Nitrous Oxide

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.

 

We need a bonkers post emoticon - this one qualifies - 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

 

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/

 

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.

 

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 ?

 

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

 

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.

 

@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.

 

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.

 

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.

 

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

 

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.