I figured it out. You're using thousands and this is a metric engine :D
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I figured it out. You're using thousands and this is a metric engine :D
If that .040 was in metric you would have .0015 english and you would have a time BoMB!!!
I was kidding if you missed it.Quote:
Originally Posted by hydro
Santa came yesterday...
Attachment 308420
And not much time!Quote:
Originally Posted by hydro
Chris, you mention working in the .054 to .066 range, that would not be in metric as .54 mm would equate to 0.021" and .054 mm would be around 2 thou so your numbers are in inches as well.
I missed it then.
I got it the 1st time!
When I build snowmobile engines I set the squish bands in the head to match tangentially to the piston dome right at the bore edge of the piston. Squish thickness there usually .035-.040 this ensures the squish band always diverges toward the center of the bore\piston. Squish area ratio is also important. I usually have squish area 50% or less of the total bore area. This is set by the width of the squish band. Best power always comes with sharp edge break from squish band transition to combustion chamber. No radius. Literally machine it and scotch bright the edge for burr.
I said it would run 95mph on the Suwanee this weekend and it did...and then some.
I went out Saturday morning with plans to make high speed passes with some others but I was the only one who showed up. I asked some fishermen to keep an eye on me while I made one pass just to feel out the new prop.
The boat was on rails and ran super straight with much less crabbing.
She went right past 95 and topped out at 97.4mph with conservative trim, a half tank of fuel, and cold (56 degrees) but humid air.
I wanted to bump the trim but I was happy with that and with really no safety backup called it good and back to the trailer.
The pass had zero drama. The boat ran so much straighter it was far less sketchy than previous top end runs. The new heads make a HUGE difference in acceleration as well. A little more testing and a good cold dry day with high air pressure she will run 98mph.
I know it begs the question is there a 100mph pass in it and I dont think so. I suppose the same special cut Tim at performance did to my 32 done to a 34 might be driveable and do it.
Today the air was better. Not as cold but high air pressure and very dry. The motor loved it and another 1mph/100rpm faster with my little prop. I was really tempted to put the 32 on but it was a little windy.
Really want to thank Tim at Performance Propeller for the special work he did to the prop. I may go ahead and cut the tuner to Hydrotecs specs which hurts bottom end but was good for 10hp up top on their dyno.
I took before and after GPS pics with time stamps and odometer reading since I was alone :D
http://img.photobucket.com/albums/v3...ps5c8e77ae.jpg
http://img.photobucket.com/albums/v3...ps413d45ab.jpg
Very nice:thumbsup:
You cant tell but Im grinning ear to ear!
Attachment 309364
Good job Mr.D!!! :thumbsup: I think I can speak for other members who have been following your project and we can "taste" that tripple digit pass. This has been a great learning thread for all! Thanks Gary;)
:iagree::cheers:
Very very good. You are close enough to smell 100mph. The right day and hitting the right ripple may send you into that mark.
If it still feels safe I say keep trying for it. But if its not going to happen no sense getting hurt.
congrats.
C
As you say, the right day and right ripple, and even if not trying it might happen and you will not know till reviewing the GPS.
Still damn cool and keep the nose down.
Thanks guys. Just looked at the pic I took of the tach recall and it was 6860 rpm on that run.
That puts slip at 6% so that prop is probably a little tall for a 32. By comparison I ran 91.5 the day before with a 33 x14.5 four blade cleaver which is 15% slip. The cleavers just dont have enough blade at my engine height even a 4 blade.
I have gained about 13-14mph since this thread started and 7mph since the new powerhead was first run.