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Thread: Looks too loose to me ..
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09-19-2017, 05:23 PM #316000 RPM
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09-19-2017, 07:22 PM #32
I toy with the idea whenever I see it sitting in the driveway going nowhere. Think Im gonna take it to florida for the winter
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09-19-2017, 09:04 PM #33
Loaded question(s) ...
The way I look at it is the port timing is like the camshaft and the conduit from the air inlets on the cowling to the exhaust exit as the intake , heads and headers .
Too much camshaft and it's gonna be a stone . A really good set of heads with a small camshaft will still make good power across a wide - flat torque curve .
Going with that thought process , Smokey told Chevrolet in the early 1950's that the intake port on their yet to be released SBC approached the valve seat at way to low of an angle . That they needed to raise the port , make the turn early and shower the entire circumference of the valve ... they fired him for saying that .
Of course , head designers and porters have been following the higher is better trend for the last 65 years . Look how far above the deck my ol buddy Curtis cut's in these troughs ..
http://raceflowdevelopment.com/produ...2300-13-5-sbc/
Remember when Honda , a predominantly 4 stroke company revealed those aluminum tank with a green stripe Elsinores in the early 70's ? They changed the game . Those were the first massed produced 2 strokes where the transfers swung wide , made the turn early and used the entire port as an exit for a uniform column , instead of running the charge up a tight wall and expecting it to make the turn at the top.
Outboard designers did the best they could by rotating the ports around the axis. It allowed them to keep the bore centerlines close and get at least a little bit of arch on the long side wall .
Having all the sleeves out opens up a lot of areas that need improvement . But they will never look like this on the short side ...
I feel pretty lucky that I grew up where I did , when I did . Between racing at Miami / Hollywood , Moroso , Orlando Speedworld and my Porsche peeps , I had-have access to some really talented people and sophisticated equipment.
One area that seems to be lacking is a good outboard dyno with enough sensing and logging ability to be able to produce quantifiable results .
Maybe that will change in the near future ... In the mean time , I still have a pretty good weather station and a few different test wheels that have been on enough stuff to know if it's sealed up and can breathe ...
Over the weekend , I had an issue where I welded up a cracked base on a 20" can . My guys rented me a little cabinet time to deck and re establish some hole's ... since a 20" won't fit in my mill , let alone add any tooling to the spindle ... LOL
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09-19-2017, 09:23 PM #34Screaming And Flying!
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Love that bridged exhaust port and the way the inlets are under it
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09-19-2017, 09:38 PM #35Member
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What cylinder is this with a cast aluminum exhaust port flange??
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09-19-2017, 09:46 PM #366000 RPM
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09-19-2017, 09:58 PM #37
This Aprillia cylinder is kind of crazy . A main transfer on each side with an axillary port on each side of the main transfer . No doubt it has a boost port above the intake port , which feeds thru and under the piston as well as a pair of side saddle's which dump across the mouth's of the transfers .
Just when you think it done and they have followed at least one rule and kept a bit of distance between the transfer and exhaust , they go and put a set of exhaust boost ports above the front set of aux transfers ... Whewwwww
I don't get the bleed hole directly above the exhaust port , but those guys have won enough small bore GP championships , than no one in their right mind can question their tactics ..
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09-19-2017, 10:21 PM #38Screaming And Flying!
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yep that is weird?
maybe to get control of chamber flow at low speed, loopers are not very good at that?
Some a re going injected, I wonder how that will change them?
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09-20-2017, 05:34 AM #39Screaming And Flying!
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Jeopardy Music
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09-20-2017, 11:47 AM #40Member
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To relieve a small portion of compression at high RPM as compression can be a top end killer.
Torque is ET and RPM is MPH.. right ? first rule in all racing with rotating assemblies.
So, knowing that, keeping your exhaust port degree timing lower (open to close) does 2 things:
1. raises corrected compression ratio over a higher port degree timing
2. lowers RPM thus increasing Torque (in conjunction with head pipe length with outboards theoretically lack)
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09-20-2017, 11:51 AM #41Member
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I'd really like to see the the depth of the rear transfer as it is fed from the side transfer area as their must not be room in the case for volume depth.
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09-21-2017, 12:17 AM #42
I'm not really sure . I was looking for air cooled Elsinore or ATC 250R jugs to show how Honda used "air column control" to change the game in two stroke technology. Unfortunately most pictures from that era seem to fall under ruin via photo bucket.
FMPulse quips :
Jeopardy Music
The only thing better would be the Fongoloid calling someone ignorant from his second grade English level ...
SnotrekieI'd really like to see the the depth of the rear transfer as it is fed from the side transfer area as their must not be room in the case for volume depth.To relieve a small portion of compression at high RPM as compression can be a top end killer.
Torque is ET and RPM is MPH.. right ? first rule in all racing with rotating assemblies.
So, knowing that, keeping your exhaust port degree timing lower (open to close) does 2 things:
1. raises corrected compression ratio over a higher port degree timing
2. lowers RPM thus increasing Torque (in conjunction with head pipe length with outboards theoretically lack)
Having slept on it , without trying to get involved in "tech-lock" ( the art of overthinking something to the point of doing nothing }
I thing both ends of that cylinder represent forward progression .
Not being under constraints of packing cylinders as close as possible , they stepped outside of using a square stud pattern at the base and moved the intake side outward to where they could feed the transfer area from the side . Yes facing down is the wrong direction , but at least they are lobbing the charge in the general direction . They still have the intake and rear boost port to feed the crank case and the back or the cylinder in the conventional manor .
I think where I was stuck was worrying about short circuiting the fresh charge out of the way to close axu exhaust ports and on that particular cylinder , the small hole above the exhaust port .
I came to the conclusion that : they don't care what they lose out of any of those holes . Unlike an outboard , they have expansion chambers to shove the escaped charge back in . And in the case of the little hole , even after the standard exhaust port closes .
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09-21-2017, 12:48 AM #43Screaming And Flying!
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Yes Chaz, they don't care. Lol
Great pictures
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09-21-2017, 07:17 AM #44
I guess I could have went into great detail about what percentage of the charge escaped and how much of that was returned as clean and useable . Of course we could then go into how much heat was induced to the overall mixture and other variables that can at best be an estimate .
It was just easier to say , "they don't care"
Either way , you wouldn't be happy ...
Great pictures
Something I noticed ..... Nothing you post , belongs to you ...
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09-21-2017, 07:28 AM #45Screaming And Flying!
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That's right Chaz, what escapes through the relief port over the exhaust, it hangs around missing blowdown and scavenging and waits for a push back in .
Super
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