North Island Series 2012-13 Final Results .......Originally Posted by NSR143
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North Island Series 2012-13 Final Results .......
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Page 770 ....
L-Plate Rider
Wobbly!
We have talked over how important the blowdown and it's size are, but what about the blowdown's intensity? If the aux exhaust ports are opening later as the main exhaust port, the peak of the pression is smaller, meanwhile the blowdown lasts longer. Of course the STA is always the same. Here is an example 'One Half'
In case of almost every race cylinder the aux exhaust ports are opening later, and this can be observed in systems with or whitout a power valve. In case of a T port the top edge radius is not 0, but pretty much bigger.
Is it important? Why don't we open the ports the widest possible? That way the ports could be positioned lower what would be optimal.
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http://www.trademe.co.nz/motors/used...-590730737.htm
Have i got an idear for you TZ350
"Instructions are just the manufacturers opinion on how to install it" Tim Taylor of "Tool Time"
Saying what we think gives us a wider conversational range than saying what we know. - Cullen Hightower
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A class at Buckets called Formula Simca perhaps...
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Attachment 282546
I have not actually done what your trying to do with the graph before myself, but because my ignition advance on WOT covers pretty much the same range as the hp, ie 0 to 30 on the Y axis I mocked up this EngMod2T dyno graph to see what it might look like.
Yellow for ignition advance and blue for power jet on/off.
Yesterday I received an email from Neels, the author of the EngMod2T simulation software to tell me that EngMod can graph what Diesel Pig was looking for and how to do it. EngMod2T is a very well supported package.
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There are two factors in play with the tripple port setup.
You have drawn them correctly with 68% main port width, as this allows greater blowdown area to be gained via the aux ports.
Out at 72% that has proven to be approx the reliable max width, you loose some blowdown, and gain total area. ( not relevant at all ).
The problem is that even at 68% you cannot run a flat port roof with 8mm corner radi, as the ring life will be zero.
Secondly is that it has been proven in many dyno sessions that having all 3 ports open together looses power.
I can only explain this as a function of the fact that the effective duct length from the outer corners of the Aux is alot longer than that from the main port
mid point to the header.
Thus you get a smearing of the initial wave amplitude ( wider but lower intensity ) as it exits the cylinder into the duct during blowdown.
This reduces the effectiveness of the expansion phase, creating less depression around BDC, and less plugging efficiency as the piston closes the port.
It would appear that having a 68% main port opening first gives a good, high amplitude wave action in the pipe, then the Aux STA gets the blowdown pressure dropped as much as is possible prior to the Trans opening.
A few pages back was a drawing I did years ago of a T port with the outer edges higher than the mid point, thinking that this would ameliorate the duct length issue, but later
testing proved it didnt work well at all.
So by inferrence even lifting the Aux higher than the main wont fix this issue either in a 3 port.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
Moped rider
Mag has just come out, 21.4 bhp after a few runs on the dyno... .
On Facebook if anyone is interested, here:
https://www.facebook.com/groups/prac...5170764195858/
Dave
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I have ridden the future today! YZ250 twostroke EFI round the back yard. Video was taken, I'll post a link when it's on line. It's a little more civilized than the Bighorn. Nice and clean power spread. No dyno run yet, just seat of the pants. We have only had about an hours worth of tuning so far.
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Who knows what about carbon / carbon pistons? Wobb?
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About zero thermal expansion; good dry friction; because of the lower specific mechanical strength wall thickness needs to be so much higher that any weight advantage is lost. The biggest problem: because of the lower thermal conductivity the crown cannot git rid of its heat, which provokes detonation.
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l have this book somwhere about a japanese guy making pistons for 500 gp bikes . wish l could find the wright up. 1500 dollars each around 15+ years ago. also made conrods
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Thankyou, Frits, crazy man, thought as much. I tried ceramic coated pistons some years ago and that's what they did , get hot and help detonation. I wonder about these modern metal sintering ( laser welding metal layer by layer ) apparently you can change the metal as the component is built up. A piston could start off aluminium alloy and end up with say a copper finish layer on top, flash chrome over that. Perhaps?
Anorak
Along these lines
Nice Yamaha twins site also has the race kit info for the RZ500
Kinky is using a feather. Perverted is using the whole chicken
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Today was the Dominic Howe, 20 laps one way then 20 laps in the opposite direction.
Glen riding Gigglebuttons, from the "Dark Side" Team ESE RS-FZR150 took the honors.
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