Milwaukee Midget

[jacksoni]

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?

[Milwaukee Midget]

Okay - long overdue - I give you . . .

FRANKENSPRITE

https://www.youtube.com/watch?v=T--m4NVyzhg&feature=youtu.be

[4-barrel Mike]

Cool!

Mike 

[Milwaukee Midget]

Mike -

I suppose this makes me a "fool"?   

[Podunk]

Chris,
THANKS
Terry

[Milwaukee Midget]

Terry,

You engineered it - I just screwed it together!

I'll bring it down to Indiana this spring and flip you the keys.

[Podunk]

Chris,
Careful. You may never see it again.
Terry

[wobblywalrus]

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. 

[jacksoni]

Sweet!!!

[hoffman900]

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.

[Rex Schimmer]

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

Rex

[Milwaukee Midget]

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' . . . 

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 . . .

[Old Scrambler]

'Fence Posts' on 55th Street

[Podunk]

Fordboy,
Did you get my PM?
Terry

[Elmo Rodge]

'Fence Posts' on 55th Street

Digital fence posts, I'm sure.  Wayno