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EFI info


DATN510

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IMG_20111118_184102.jpg

These items I also got at HF made this next task go alot easier. Most important is to hold on tight to the melal and ware thick gloves.

IMG_20111118_184352.jpg

When I had small cuts I just went to the edge and broke the piece of so it wouldn't get caught in the blade and go flying. IMG_20111118_183618.jpg

This is as far as I got for now it took me about 2 hours to get to this point. More to come

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So begins the EFI manifold, here is the materials I'm using that cost $70

IMG_20111118_165037.jpg

The materials I go are a 5' piece of aluminum tubing with an inside diameter if 1.490" with a 1.650" outer diameter. With. 0.140 wall thickness.

flange and pleneum base I got. .5" x 4"x 4'.

And a 3'x2'x0.140 (1/8 inch) for the outer part of pelenum.

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I then cut the pleneum base @ 16".

Here is where I need some info. Do I taper the end of the pleneum base at the #4 cylinder or #1 or if any. With the outer cover do I make the entrance wider and go smaller at the end to compensate for the #4 cylinder getting the same amount of air?

Tired now need to go to bed, goodnight all. IMG_20111118_220109.jpg

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Not sure what the popular wisdom is on this, I would think the bigger the better. The port and runner length can be tuned for length. A very very rough formula is 79200 divided by the peak torque RPM you want. Very very rough but a starting point...

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79200 / 3600 RPM = 22. 22 what? inches, CM, some other measurement?

 

This is a very rough formula and is intended just to make it easier. The real formula involves the speed of sound in relation to air temperature, port cross sectional area and can easily be upset by radical cam timing. In effect the vacuum pulse from the intake must travel up the intake port and runner to open air (in this case the plenum) where it 'echos' back as a pressure wave. The trick is to get the length of the runner so that this pressure wave just barely sneaks back into the cylinder past the closing valve like Indiana Jones. The speed of sound will remain fixed so at low RPMs the runner will have to be many feet long, but as the RPMs go up the time is shorter so the pulse needs to get back sooner and a shorter pipe is needed. Port tuning only affects a fairly narrow RPM range. Try 6K... now it comes down to 13.2 inches. When you subtract the head port to valve face distance, (4-6" just guessing) the runner length is about 9" or less. 7,000 RPMs would be just over 11" long minus the head port length for a runner of around 6-7". .

 

As I said this is a very rough and simplified formula. You can tune for a specific RPM range to take advantage of a small increase in free cylinder filling.

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I had a video at one time of a fella that had a variable runner length EFI system where the runners would shorten as a function of throttle opening.

I also had a rather dry & heady book from the 50's or 60's that was on the science of frequencies as applied to intake and exhaust design.

 

Can't find either now.... dammit.:angry:

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I did some more work on the manifold yesterday, first ill show you a mistake I made useing the table saw. I used the table saw to cut the middle part of the flange and this is what happeded.IMG_20111119_135928.jpg

 

First I centered the holes on the penum base with the gasket and drilled the holes.

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I was planning on having the runners fit into a slot at the hole for more strenght but I drilled the hole to big.

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But it will still work

 

Then I drilled the port holes in the plenum base.

 

 

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I first got a 2x4 and cut a larger hole then the hole I was routering so the bearing wouldn't hit anything.

 

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Then came the tedius part of routering air horns into the plenum base, I first did a few practice runs and it was a good thing I did. Cause the bearing on the router bit came off and screwed up my test piece.

 

After putting the bearing back on I started the routering.

 

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I took it very slow, just took a little off at a time and held tight on the router.

 

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The routering went perfect on this stage, but the router didn't go deep enough to where It.

 

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So I went to home depot and picked up a round bit with a smaller radius to get the lower part of the bowl.

 

Sorry didn't get pics of this,but I will explain. I cut a smaller hole in that same piece of wood for the bearing to hit so I could router the bowl lower to about .02 which was perfect.

 

Look at that like one long volocity stack with no air restricktions.

 

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Then I cut the lip out on the plenum base with the table saw.

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This cut was just right.

 

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Plenum cover fit perfect.

 

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Then I started working on the plenum cover, I started with some thin strips of cardboard to get the general size I wanted and cut it out on a bigger piece of cardboard.

 

I went with 11" wide on the front and 8" on the back for beter flow to the 3 and 4 cylinder lenght is 16"

 

 

 

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I then rolled it some and taped it to theplenum base for a sample mock up.

 

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And this is what I ended up with.

 

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Now I need to figure out how to roll this sheet of metal without spending any money.

 

I'm leaving for Ashland Oregon on Tuesday so I need to save my money.

 

And please coment on this build your input is important as it is helpful.

 

Later

Mike

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1.375 diameter. Please explain why and how to fix?

You want the flow to all the cylinders to be equal.If there is a straight "run" to one cylinder and not others,that cylinder will run lean as it will get more air flow.Is the TPS going to be mounted perpendicular to the head-flange or on a slight angle,pointing towards corner where the fender & radiator support meet?

 

And the diameter is the same as a L-20B maifold runner-but you knew that...right? :cool:

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