200 CFM Research

[200cfm]

Poured a second mold late this evening on the test head. Thinking of slicing it to get CSA measurements.

What are folks using to slice their molds? I tried a band saw and it did a terrible job. How do you get a dead smooth slice, "like a flat piece of paper cut." If the slice is butchered it is useless.

[jfholm]

Tom,
Something like this which is only .012" thick would be ideal. You might find one at Home Depot or Lowe's. My wife has a thin flat wide fine tooth bread knife. Shhhh you did not hear that from me. :;): or just try a nice flat sharp stiff knife.
John

[bruce]

What about a cheese knife? The one that is just a wire

[49-1183904562]

Ask the guy at the Delli if he would do it after hours?? it just sanitery silicone.

Rick

Realy Tom a very sharp butchers knife sprayed with Silicone spray should do it.

[jfholm]

You will not find a sharp butcher knife in my house :;):

John

[slracer]

I've been out of touch for over 2 weeks and trying to get caught up with Forum info.

First, Tom, Great job! Congrats!

Second, you are right on about density and the speed of sound in a gas: "Not sure about the density or mass causing the mach number to change in a gas. Might change at higher altitude because of the temperature change. Pretty cold at 30,000 ft so a sound wave would travel at a different speed."

Just for info: The US Standard Atmosphere shows the speed of sound from 36089 ft to 65616 ft to be constant at 968.077 fps with the temperature a constant -69.7* F while the density varies from .000706 slugs/cu ft at the lower limit to .000171 at the higher altitude. Temperature is the key!

Doug

[200cfm]

Here is the final mold. The expansion area after the pushrod turn was filled in and the curve dip before the headbolt turn was filled in. Never will be dead straight but a lot straighter than where it started. I took the mold all the way to the 45 seat itself to capture the entire turn from the SSR. (tom)

And I left out the clay divider ridge between the two channels since that ridge is going to be difficult to cut/shape.

[jfholm]

Tom,
A couple of interesting threads pertaining to boosted engines over at

and this one I think is an old thread of yours that has taken new life

If the second thread is yours you will have to change your user name and you are no longer 11 second Avanti but pushing 9 second Avanti

John

[jfholm]

Tom,
I talked to a friend that is into turbo charging and he verified with me that you still do need to worry about port size for a turbo's motor especially at the lower rpm low boost situations. Also his belief was that because of the boost you can pack more air fuel through a smaller port due to the pressure. This makes sense as how to you get more volume through a hole? Either increase pressure or make the hole bigger. That is a simplistic view. What he and I could not come up with an answer is how do the port sizes effect the mach number in the port with a turbo engine. I would have to think it would be close to the same as a n/a engine.

Bottom line is will the turbo port go into a choke situation with a smaller port just like a N/A engine? I would think so, but I am not sure on this. Any one else have any thoughts on this? Let's help Tom get into the nines

[blaktopr]

Lots of thoughts, but all over the place. But how about this. Looking at the "choke" in relation to time and cylinder fill. In a NA app, when the piston is on the down stroke, the choke can occur sooner especially at max piston speed. In a boosted app, because of the ability for the increased volume to occur through boost through the same size "hole" sooner, choke is not occuring. But when the pressure differential becomes less later in the cycle, I am wondering if the conditions start to look closer to NA. (???)
For boosted apps, I think I would look at port shape and pressure recovery out of the valve. Plus the exhaust side. I see 9's a comming.

Chris

[jfholm]

And I forgot to mention to Tom that the port molds are sure looking better. Getting to be a real nice shape.

John

[jfholm]

Tom,
I found a great thread over at Speedtalk. You should read this full thread it is pretty informative. Here is one quote from it that helps a lot!

"Here's a (probably not original, given my penchant for reinventing the wheel) thought about highly supercharged engine cam timing: Since the charge density may be two or three times that of an NA engine, so will be its inertia, thus it should be possible to leave IVC much later without reversion detracting from the trapped V.E.

Along the same lines, although charge density does not affect the speed of sound in the mixture, temperature does and a high boost engine, even with a good intercooler, will almost inevitably have much higher mixture temps. Thus a higher fps port velocity will correspond to a given optimum Mach number and so minimum port areas might need a re-think ..."

The link to the thread is:



So what I interpret it to mean is the need for a larger intake port CSA than a N/A engine. This is the direction I was leaning to in the first place.

John

[jsa]

[jsa]

[jfholm]