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Thread: LOOPER TECH TIP's.........
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08-22-2017, 09:26 PM #61Screaming And Flying!
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has anyone ever posted the block mods to a closed deck engine?
Did we ever decide that the bottom 2 cylinders get a hard time as they are way cooler so probably have a higher bmep?
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08-23-2017, 04:53 AM #62
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08-23-2017, 05:06 AM #63
The bottom cyls do have a denser charge since they are cooler. This is why they reduced compression on the bottom two.
All the newer di stuff back to fichts are cooled similar to how Al mods the carb engines. Heads are still the last to get water and on the di stuff cyl temp is high all the time.
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08-23-2017, 06:21 AM #64I'd rather be competitive w/junk I built in my garage than win w/stuff I bought.
I refuse to allow common sense to interfere w/my boat buying decisions.
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08-23-2017, 06:33 AM #65Screaming And Flying!
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The bottom and top exhaust looks similar its the middle 2 that have a lot shorter pipes as thats the join then it goes down to the bottom.
When we know no 2 blows and 5 and 6 have an issue that the factory recognised then you look at the exhaust and its hard to see the connection
but yes the bottom 2 have a 180 to get out.Last edited by powerabout; 08-23-2017 at 06:47 AM.
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08-23-2017, 07:04 AM #66Screaming And Flying!
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If scavenging less on the bottom 2 what do we get?
Less reverse pulse so less bmep?
and does that mean less carb signal so leaner?
cooler ( due to water passages) so more bmep with leaner mixture?
so how do we get No2 blowing up?
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08-23-2017, 07:26 AM #67
very good amount of info on this topic.
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08-23-2017, 12:11 PM #68Screaming And Flying!
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You figure the fresh incoming charge has enough time to shed ambient temperature and heat of compression from the case and gain density before entering cyl? What's the fire order , could be that two cyl are lower because of tuned pairs stuffing effect is strong compared to the long run out of the three. At speed the long run may be delayed too long and arrival may be near closing raising compression or not stuffing effectively.
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warpt liked this post
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08-23-2017, 03:37 PM #69
1-6 is firing order.
Bottom cyls run coolest since they r the first to get cool water. If you run the same compression on all 6 u will need to go up a couple sizes on the lower mains. The factory reduced compression in bottom two. Yamaha does the same
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08-23-2017, 04:09 PM #70Screaming And Flying!
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Yamaha does it for the same reason. No need to richen because cyl pressure at speed about the same. Bottom cylinders first because they have more chance to heat at speed. That's how I figure it works
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08-23-2017, 07:06 PM #71Screaming And Flying!
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so why is no2 is the one that blows up?
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08-23-2017, 07:29 PM #72Screaming And Flying!
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What's the fire order, top bottom mid? Then bottom is stuffing top , longest run could be a weak stuff . Could be at high rpm just plain too much heat being last on cooling.
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08-24-2017, 06:24 AM #73
Yep.. the magic question? both 1&2 get the same water that"s already run past a glowing hot exhaust runner... but #2 has the thrust face on the exhaust port side, if one of the 2 fails most likely going to be the left side. You would think 3 & 4 get the hottest water it goes in right above where the 3 cylinders meet at the middle of the ex-runner (hot hot hot)mixed with hot water thats already past by the top cylinder exhaust port. The etecs plumb some cool water into the block 1/2 way up by the use of hoses and a closed off base gasket to help cool the runners and im sure it gets cooler water to the upper cyls. Dave
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08-24-2017, 06:57 AM #74
Added hoses on my latest project (way behind, moving ect..) lower hose cools runners in 2/3 area upper has metal tee and aims water at upper cyl inlet areas, have another plug to move it up if it doesnt work out as planned lol.. Dave
Last edited by H2OPERF; 08-24-2017 at 07:02 AM.
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powerabout, FMP liked this post
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08-24-2017, 07:05 AM #75