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Author Topic: Milwaukee Midget  (Read 1576747 times)
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jacksoni
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« Reply #6150 on: January 28, 2017, 11:17:44 AM »

Hoffman- that plot appears to show a lot of reversion at the valve on both IO and IC? Also, how do you correlate those plots to your goal of 300fps + or - as stated?
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Jack Iliff
 G/BGS-250.235 1987
 G/GC- 169.741  2009
 G/GMS-178.835 2010
Milwaukee Midget
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« Reply #6151 on: January 28, 2017, 06:21:54 PM »

Okay - long overdue - I give you . . .

FRANKENSPRITE

https://www.youtube.com/watch?v=T--m4NVyzhg&feature=youtu.be
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"Problems are almost always a sign of progress."  Harold Bettes
Well, I guess we're making a LOT of progress . . .  rolleyes

We are NOT rebuilding . . . We are reloading.

GOD SAVE MG - The Queen can take care of herself!
4-barrel Mike
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« Reply #6152 on: January 28, 2017, 07:14:15 PM »

Cool!

Mike  cheers
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Mike Kelly - PROUD owner of the V4F that powered the #1931 VGC to a 82.803 mph record in 2008!
Milwaukee Midget
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« Reply #6153 on: January 28, 2017, 07:23:43 PM »

Mike -

I suppose this makes me a "fool"?   wink

 cheers
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"Problems are almost always a sign of progress."  Harold Bettes
Well, I guess we're making a LOT of progress . . .  rolleyes

We are NOT rebuilding . . . We are reloading.

GOD SAVE MG - The Queen can take care of herself!
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« Reply #6154 on: January 28, 2017, 07:47:13 PM »

Chris,
THANKS
Terry
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Milwaukee Midget
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« Reply #6155 on: January 28, 2017, 07:54:23 PM »

Terry,

You engineered it - I just screwed it together!

I'll bring it down to Indiana this spring and flip you the keys.
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"Problems are almost always a sign of progress."  Harold Bettes
Well, I guess we're making a LOT of progress . . .  rolleyes

We are NOT rebuilding . . . We are reloading.

GOD SAVE MG - The Queen can take care of herself!
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« Reply #6156 on: January 28, 2017, 08:00:34 PM »

Chris,
Careful. You may never see it again.
Terry
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wobblywalrus
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« Reply #6157 on: January 29, 2017, 12:00:59 AM »

There are a lot of years of flow bench data on the Triumph.  It is possible for me to fairly accurately extrapolate and interpolate flow vs lift curves at 28 inches.  A bunch of late nights were spent modeling various valve sizes and port flows.  Real big valves and lots of low lift flow hurt performance.  It reduced the trapped mass 'cause too much flow was getting past the valves at the wrong time.  These times are when the engine cannot trap and compress the mixture or it blows off cylinder pressure too early.

The best valve size combo had an intake mach maximum between .5 and .6.  These are valve sizes only 1mm larger than standard.  The flow curves with well developed port shapes that gave good flow at mid and high lifts worked best.  They supply the engine with mixture when it has high demand.

That surprised me.  I always thought more is better.  It seems just enough is best. 
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jacksoni
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« Reply #6158 on: January 29, 2017, 09:10:36 AM »

Sweet!!!
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Jack Iliff
 G/BGS-250.235 1987
 G/GC- 169.741  2009
 G/GMS-178.835 2010
hoffman900
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« Reply #6159 on: January 29, 2017, 09:35:47 AM »

Hoffman- that plot appears to show a lot of reversion at the valve on both IO and IC? Also, how do you correlate those plots to your goal of 300fps + or - as stated?

That is a the valve seat. As you can see, moving up into the throat then just a little over an inch into the port, it drops off.

I think one thing to keep in mind is what good low-lift flow can and can't do. Low lift flow will make the engine think it has more duration than it does (remember, seat-to-seat duration is what the engine really sees).

Another way of looking at it is this, especially as it relates to a 2 valve engine:

To get a certain amount of lift you need a certain amount of duration. The velocity and acceleration of the lifter is going to be dictated by type and diameter. There is a fixed value. Yo can only move the lifter so fast. Since we only have a certain amount of time (duration) to create lift, this will ultimately be the limiting factor.  Spintron development and spring technology have allowed us to do more and be less abusive to the valvetrain, but ultimately we're still limited.

Take for example the NASCAR flat tappet change to roller lifters. I asked Jay Wiles of Hendricks if they would gain any more power. His response was no because they were already at the acceleration limit of what a spring could do. The flat tappet cams used high rocker ratios (2:1+). The rollers, while allowing for more aggressive profiles will need less rocker ratio to keep the valve acceleration equal to that. The net is there was really no change in the actual valve lift profile as the engine sees it. Anyway that is a tangent.

So getting back to velocity. You could convert it back mathematically, but the point to illustrate is what is important in the valve lift equation. There is a lot to be said about velocity - just look at what Larry Meaux, Darin Morgan, Chad Speier, Larry Widmer, Curtis Boggs, and many, many others have written over the years. Just to rant, it cracks me up when people talk about drag racers hogging the ports out. Nope, not the good ones. The only difference is that a drag race engine will likely rev a little higher, so the port cross section will be a little bigger, but the same physics apply. This is why when you see a cylinder head that is sized properly and produces peak power at say 7500rpm on a 1.8L engine, when put on a 1.0L engine will want to peak at 9500rpm. Do the math and you'll see why. Piston cfm demand drives the whole engine equation and everything else is sized from there.
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Rex Schimmer
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« Reply #6160 on: January 29, 2017, 04:04:52 PM »

Chris,
Watched the vid and did not see ANY smokey, tire churning burn outs!! What gives?

Rex
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Not much matters and the rest doesn't matter at all.
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« Reply #6161 on: January 29, 2017, 06:42:39 PM »

Chris,
Watched the vid and did not see ANY smokey, tire churning burn outs!! What gives?

Rex

Kate was taking the video, and as open and honest as our relationship is, there remains a few things one just doesn't do when the wife's watchin' . . .  wink

I need to sort it out a bit - get it so it idles - maybe roll back the timing a bit. 

Now I DID punch it a little heading up 55th street.  I was doing about 25 mph in 2nd, and rolled into it.  It's running a bit rich, but when it cleared its throat, the rear end cut loose and it put quite a few fence posts in the rear view mirror in a hurry.

This is going to require a bit of discipline to drive smoothly.  It's capable of getting you into big trouble in short order.

I'm thinking of installing seat belts . . .
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"Problems are almost always a sign of progress."  Harold Bettes
Well, I guess we're making a LOT of progress . . .  rolleyes

We are NOT rebuilding . . . We are reloading.

GOD SAVE MG - The Queen can take care of herself!
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« Reply #6162 on: January 29, 2017, 08:20:15 PM »

'Fence Posts' on 55th Street shocked shocked shocked shocked shocked
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2011 AMA Record - 250cc M-PG TRIUMPH Tiger Cub - 82.5 mph
2013 AMA Record - 250cc MPS-PG TRIUMPH Tiger Cub - 88.7 mph
2016 AMA Record - 750cc M-CG HONDA CB750 sohc - 130.7 mph
2016 AMA Record - 750cc MPS-CG HONDA CB750 sohc - 137.7 mph
Chasis Builder / Tuner: Dave Murre
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« Reply #6163 on: January 30, 2017, 11:28:15 AM »

Fordboy,
Did you get my PM?
Terry
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Elmo Rodge
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« Reply #6164 on: January 30, 2017, 10:24:55 PM »

'Fence Posts' on 55th Street shocked shocked shocked shocked shocked
Digital fence posts, I'm sure.  grin Wayno
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