Advanced Hemi 212cc Predator Build

[bob58o]

What are going to weld?

I' going to fill in the step where the exhaust tube meets the flange.
Then I'm going to taper it instead of having a step.

 

[bob58o]

Going to make it look like this and matched to the shape and side of the port entry.

 

[bob58o]

Right now there are two sharp step reductions...

What about back pressure???
Fugghetaboutit?

 

[bob58o]

What do you think?

 

[bob58o]

Gift from a buddy at work.
One pair so he doesn't get too injured while handling his snakes.
One so I don't get too hurt while injuring my engine.

 

[chancer]

What do you think?

I think that is a good Idea. Have you ever looked closely at the stock exhaust? OMG what a POS.

 

[bob58o]

Last minute objections????

 

[chancer]

Get a work bench so you don't have to kneel in that gravel to weld!

 

[bob58o]

I think that is a good Idea. Have you ever looked closely at the stock exhaust? OMG what a POS.

I've got it in a box. I never looked at it. It was always the first thing that came off.

I might use it to make another pipe with 1.05" ID for fun and to see how going up 1 size on pipe diameter makes a difference and and what RPMs

---------- Post added at 02:49 PM ---------- Previous post was at 02:47 PM ----------

Get a work bench so you don't have to kneel in that gravel to weld!

The pain keeps me focused and on point. LOL

 

[chancer]

Go weld it already!!!

 

[bob58o]

First attempt...
About what I expected.
I didn't forget how bad I was at this, so that is part of the reason why I wanted to do this.

Another pass with the welder. Some tack welds.. Just might do it??

The spatter will make getting a perfect gasket surface difficult, but I think it will be fine.

Was going til wait til it looked good, but why start being shy now?

 

[chancer]

But you are going to grind that to a taper. So did you weld the outside.
Plus I am pretty sure you have the grinding, sanding, polishing tools to get rid of the slag!

 

[bob58o]

I I got these carbide burrs which I never used for porting the head.
A few more fill in's needed.
Hopefully these won't break off and somehow get sucked back into the chamber.

Still a few tack welds short of where I need to be.

This is getting uglier than I imagined..

I foresee belt sanding, hand sanding, and probably some RTV Red High Temp Gasket stuff???

It does not look pretty... Yet. It think it can and will look decent enough. It may take some time

 

[bob58o]

After Some more clean up with sanding rolls ..

Still need to fill in some spots to give me the meat I want to start with.

Then I can do some gasket tracing and material removal.

For now I'm just trying to get rid of the second step.

Then I will open up the face of the flange so that it matches the exhaust port. The opening on the flange will be 1.125" at its widest point. It will taper to the 0.8xx? ID of the 3/4 pipe.

 

[bob58o]

Exhaust port...

 

[chancer]

I am sure you have done the research but... Why 3/4"ID and not 1"ID. I mean you opened all this up to "flow" why constrict it wj=ith the pipe? Is there some sort of advantage? or is 3/4 ID just what you had.

 

[bob58o]

So I think I don't HAVE to do any more welding. I think If I belt sand (then hand sand) the flange gasket surface, I can get a clean 1.125" Diameter Surface. Any missing weld will be smoothed out by the taper I sand.

---------- Post added at 04:35 PM ---------- Previous post was at 04:22 PM ----------

I am sure you have done the research but... Why 3/4"ID and not 1"ID. I mean you opened all this up to "flow" why constrict it wj=ith the pipe? Is there some sort of advantage? or is 3/4 ID just what you had.

That is the perfectly fine exhaust from the stage 1 kit.

http://www.musclecardiy.com/perform...t-system-math-build-high-performance-engines/

Cylinder Volume = displacement ÷ number of cylinders
Ac/s = (cylinder volume x RPM) ÷ 88,200
Or RPM = (Ac/s x 88,200) ÷ cylinder volume
Where:
Ac/s = primary pipe c/s area
Cylinder volume = volume of a single cylinder
88,200 = mathematical constant
RPM = RPM at torque peak

For me assuming max Torque at 4800 RPM, optimal exhaust ID is 0.938".

3/4" inch pipe has ID around 0.85" I think.
1" Pipe has ID around 1.05" I think.

I'm right in the middle.

Larger Diameter Pipe is better for Higher RPMs and Thinner is better for lower.

---------- Post added at 04:44 PM ---------- Previous post was at 04:35 PM ----------

9.1" length with 3/4" Pipe.
5.1" length with 1 inch Pipe?

Didn't do any math... Just input the numbers..

Others say 0.82" Diameter and 42" long.

http://www.bgsoflex.com/bestheader.html

---------- Post added at 05:06 PM ---------- Previous post was at 04:44 PM ----------

According to the sim:

0.85" ID x 9.1"
Peak TQ 13.4 @ 4900 RPM
Peak HP 15.9 @ 7600 RPM

1.05" ID x 9.1"
13.3 @ 5200
16.4 @ 7900

1.05" ID x 5.1"
12.9 @ 5200
16.4 @ 7900

0.85" ID x 5.1"
13.1 @ 4900
16.1 @ 7600

0.85" ID x 13.1"
13.3 @ 4600
15.9 @ 7600

0.82" ID x 42"
13.4 @ 4600
14.0 @ 7000

---------- Post added at 05:39 PM ---------- Previous post was at 05:06 PM ----------

A Tuned Exhaust to fit the engine I built I think (according this ? sim) would be around 15" long and 3/4" pipe (0.8x?" ID).

That may reduce potential TQ and HP, but would shift the power band to a more suitable spot for my springs. Or get heavier springs. Or wait til it runs. LOL

15"

Max Tq 13.2 ft lb at 4000 RPM
Max HP 15.5 ft lb at 7000 RPM

compared to the 9.1" Pipe same Diameter

Max Tq 13.4 ft lb at 4900 RPM
Max HP 16.4 HP at 7900 RPM

 

[Poboy kartman]

I'm trying to figure out if my head hurts from drinking too much Scotch and faceplanting it into rocks....or reading Bob's posts!

 

[bob58o]

Displacement of engine = 12.9 cubic inches.

---------- Post added at 10:45 PM ---------- Previous post was at 10:37 PM ----------

There is also wave tuning. Pressure waves travel at the speed of sound. Which is about 1300 ft/sec at head temps. Using RPM and valve timing. You can match length of pipe so that pressure wave timing is optimized as it reflects in the exhaust pipe. I haven't had much success playing around with this yet.

 

[chancer]

Too bad Brett is not here to weigh in. He built some crazy Exhausts for his 2 strokes, but probably would have good input on this too.