Milwaukee Midget

[fordboy628]

Fordboy,
Did you get my PM?
Terry

Yes.    Thank you.

That is a generous offer and no doubt Chris will want to take you up on that.

 
Fordboy

[fordboy628]

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. 

The trick is to "fulfill demand" in the "most timely and efficient" manner.

You are ahead of the curve here Bo.    Most guys never get this.

 
Mark

[fordboy628]

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.

Effective mechanical spring control of the decelerating valve mass has been the limitation at the edge of performance for a very long time.    That is exactly why F1 has gone to pneumatic valve springs.   Very low mass and spring rates that can not be achieved within the properties of metals.

Valve train mass, in itself, presents its' own set of problems.    This is why "edge of performance" systems use components made from 'unobtanium' & 'highcostium', all DLC coated . . . . . .

For most non-professional racers, the trick is to balance performance and cost at some "affordable" and "sustainable" dollar amount.

Unless you have access to NASA type amounts of cash . . . . . . . .

 
Sensibleboy

[Milwaukee Midget]

'Fence Posts' on 55th Street

Digital fence posts, I'm sure.  Wayno

Metaphorical fence posts - an old Iowa expression, meaning "shittinandagittin".

[Milwaukee Midget]

I'm looking at the weather - The coasts have been pummeled, but here in Beerhaven, 60 degrees in February?  I picked the right weekend to take 4 days off!

Joined about three other neighbors in washing cars today.  A little soap, water, turd polish . . .




Seat belts are in - mostly for looks - I'm fooling myself if I really think they'll do anything other than make it easier on the first-responders to find me.  Took care of a manifold leak on Friday, some Holley parts are due in the mail tomorrow, but other than some carb adjustment, a loose ground in the dash and trying to find some fool to underwrite it for insurance, it's pretty much good to go.

Still waiting on the K-block . . .

[4-barrel Mike]

Nice plate! 

Mike

[Milwaukee Midget]

Nice plate! 

Mike

It used to reside on the Magnum - thus, the big scrape from misaligned attempts to hook up the trailer.

When I left it with a certain tank racer and his bearded bibbed buddy in Utah in '14, I came back to find a small sign covering the number, and it read "PALE ALE".

As if driving this thing wasn't already an open invitation to get pulled over.

[Jack Gifford]

Beerhaven still have any of those old 'fenders-must-cover-tires' laws?

[Milwaukee Midget]

Beerhaven still have any of those old 'fenders-must-cover-tires' laws?

Jack, I'm not sure - I see a lot of Hondas and F-250s running around with rubber extending past the lip. 

It's the audio system I'm concerned about - glass packs and baffles. 

The baffles helped quite a bit, but we hit 60 degrees today, and the Harley guys were covering their ears when I rolled up to the lights at 76th and Burleigh.

There's not a lot of room for real mufflers under this thing . . .

[wheelrdealer]

Chris:
As long as it has a glove box, you are fine. That's where you store the non-moving violation tickets. When you drive a rebel car you have to pay a rebel's dues. Go out and make the dogs howl and the old folks cringe.

If a thong is a swim suit then glass packs or baffled pipes are mufflers.

Looks like a wide ride.

BR

[wisdonm]

Glad to see you're driving it. Chris. Check with Hagerty insurance.

If you get a noise ticket go to court and claim selective law enforcement by demanding to see how many Harley  noise tickets he has written in the last year.

[Seldom Seen Slim]

My first bike was a Honda 750 with straight (looking) pipes.  Inside were little baffles, just big enough to obstruct a policeman's pencil.  The cop would stop me for no mufflers ( it was a tad bold-sounding) and I'd ask him to check the pipes.  Stick a pen up there and it'd only go in a bit and he'd allow that I had "mufflers".  "Stay out of the throttle around me" -- and I'd go on, quietly, for a mile, at least.

Give it a try, Chris.  I envy you and your fun car.  Dang. . .

[SPARKY]

Envy?  not me---I am just thinking what a big smile my buddy Podunk is going to have when he sees this post---his dream come to fruition---going through the gears making noise, smiles and thumbs up----just happens to have a different owner-driver but the little beast lives        to the both of you!!!!!!!!!!!

[Podunk]

 

[SPARKY]

Chris a man in the music business should know how to record this little snarly, big eyed pomey pygmy so that the unwashed masses in the outer world might enjoy it going through the gears