The carbon ones certainly look faster. Especially when framed by an official NSR-World carbon carb shroud. Mmmmm carbon shrouuudd.....
Don't you think Tyga should make carbon flywheel/ignition covers for the NSR? I reckon they ought to. _________________ After years of moaning about immigrants now i am one...
The TYGA reeds work well enough with the stock reed cages and stuffers but don't perform as well as the full HRC set up (which as it happens doesn't use the plastic stuffer).
It's a good compromise though as the HRC reeds and cages arn't very common. _________________ If I have to take the carbs off once more...
More of Steve's word games...these comments may both be true.
StephenRC45 wrote:The proper HRC reed for the NSR is nothing like the stock reed. It also uses a differnt reed cage to the stock one.
StephenRC45 wrote:The TYGA reeds wont fit the true HRC reed cages.
But there are HRC reeds and HRC stuffers that fit the stock NSR reed cages.
Anyone got any experience of back to back testing these with either stock or Tyga (or anyone elses) reeds? _________________ Please do not PM me technical questions, if you can't find it on the Forum start a thread
Well i had a set of highly modified reed cages made which gave me roughly 1.5bhp over the HRC reed stuffers and reeds [standard mc21 reed cages] on Steve's dyno! Although it does not appear until the top part of the power curve it pulls a lot better on the road.
So you can improve on HRC parts........ _________________ MC21 300
Aprilia RS250 track bike
HRC parts are not the final word. As with most commercially available stuff they are a good starting point and should be played with. On my old race bike I epoxied the plastic stuffers into the valve and then filled in with more epoxy and got grinding.
15 or so years ago I spent many hours on the dyno testing reed valves. This was after reading through lots of Yamaha white papers on the subject. Very interesting and worth searching for if you can be bothered. There's a lot about carb to reed area ratio and what they say makes sense, and tests out as gospel on the dyno and in the real world.
Remember the old steel reeds? They always seemed to fail at the most inconvenient times. This was basically down to fatigue and constantly hitting their natural frequency of resonance, which would cause them to slowly but sure destroy themselves. Thankfully, fibre and carbon reeds have a high frequency of resonance that you dont get to, so they don't (usually) fly to pieces. Where they do suffer is from the constant heat cycling and fuel washing, which breaks down and softens the epoxy holding them together.
If you want to play with reeds then you should really be looking to widen them first before increasing the lift. If you can get the same area but with less lift them the petals react faster and performance is improved. Remember that at 12,000rpm that poor little petal is opening and slamming shut at 200 times a second, so if it only has to lift say 10mm instead of 11mm then that's 2mm less travel per cycle, or 40cm per second. That's gotta be a good thing when you're looking for fast reaction times.
Another thing about lift is that if you try going too high then there's a chance that the reeds won't hit the stopper and they become unstable. HRC and others have got round this with stiff reeds or extra supporting reeds and don't actually use a stopper. The reed tension is sufficient to control this.
I don't think (when on pipe) the petal returns to seat on the cage, before it's sucked open again.Your engine will run without reeds or rotary valves when on pipe.
Central splitters help to direct air at the petal tip where it bends easiest, that looses the least amount of inertia.
Now then, I've never actually seen a reed at full chat under a high speed camera, but given that it is primarily a one way valve then it would need to completely seal the crankcase for it to be effective. Look at the blowback on an old piston ported or a rotary valved stroker that's been tuned for more power and you can plainly see that having the case unsealed at the wrong time is not good.
Yes an engine will probably run without the reeds installed, but not particularly efficiently.
Let's say you have a transfer port effective area of 850mm^2, and a 32mm carb (804mm^2) then during crank case compression you'd lose a lot of the charge back through the carb, but maybe transfer enough to keep it running. That's not taking any intake velocity, or exhaust suction pulses into account.
From various literature written by people who know more than me, a reed valve opens around 120 degree BTDC at low rpm, closing again at about 40 degree ATDC. And then there's a pretty linear change up to high rpm where the open duration increases from 160 degree up to over 200 degree, but the opening point has now moved to about 80 degree BTDC while the closing is some 120 degree ATDC. So basically the reed valve 'adjusts' to the engine requirements.
A simple 2 stroke engine is only an air pump after all. Try taking the reed valves out of your air compressor and see how long it takes to get any pressure.
Two strokes are not simple they only seem simple (sic F.Overmars)
If the reed timing self adjusts what causes that? The throttle? The reeds themselves? The ignition? RPM? My bet is again the pipe(and the throttle). The reeds will not open fully when the throttle is not open fully.
Stand off in non existant on rotary valve engines when on pipe same with piston ports. The common theme is that the PIPE is the over riding influence. I can assure you that a inlet where it uses reeds to start and then swing out of the way once on pipe makes much better HP on the dyno and runs perfectly.
Any simple simulator shows the reeds lifting at BDC as this is the time the pipe is sucking hardest.If the engine wanted more air/fuel at this point why not give it to the engine? The fully open inlet is similar to above the exhaust port starting holes in big bore mxers and perforated rear cone kart pipes. The holes 'disappear' when on pipe,
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