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  #21  
Old 08-31-2021, 11:49 AM
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Quote:
Originally Posted by HWYSTR455 View Post
As for injector placement, you want the injector end pointing directly at the back of the intake valve. You can choose injectors with different spray patterns depending on desire. .
I did a year and a half study on injector placement, at my job years ago, and
I will say that there is no IDEAL injector "Point" location for the spray based on that very accurate, engine dyno Research Study.

Way too many variables involved.

The key thing is that: depending on the speed of the air/fuel charge as it approaches the valve seat (engine rpm), the air flows differently around the
valve seat and into the chamber. That is why ports will have tumble which may change to swirl and vise versa depending on the head design.
A 4 valve head has much better control of the flow patterns into the combustion chamber/cylinder vs a 2 valve head.

That is why there are so many variables in 2 valve head design.
But I guess Generic Statements are as good as anything else in injector
placement and angle.

The reality is you would probably be with-in a couple of HP if the injector rails (from an end view) were vertical on the intake vs trying to get the injector pointed exactly at the back of the valve. If you were doing Emissions work, maybe you create 4 or 5 designs and see which one gives the lowest emissions for the EPA Testing.

Just my experience on this topic.

Tom V.

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  #22  
Old 08-31-2021, 12:38 PM
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I would still think pointed down the port towards the valve would be better than pointing straight down at the floor of the runner, or at least that would be my line of thinking. Maybe a 45 degree 'lean', down the port even.

But suspect you're right about not much of a difference. I was parroting what Marren told me in previous conversations. Guess it's more of a general' or 'generic' statement as you mentioned Tom...

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  #23  
Old 08-31-2021, 03:01 PM
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If you are running in a water craft at a given fixed speed then you can design the fuel spray for spending most of the time at that engine rpm point.

Same deal with a Drag Race engine. Not the case with a Road Race Engine or a street driven application.

So you are correct, for Drag Racing pointing the injector at the center of the valve bowl might be better but cannot believe that anyone using a Offy dual quad intake is assuming max power and needs more than a simple vertical Injector Position.

Tom V.

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  #24  
Old 08-31-2021, 07:49 PM
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Quote:
Originally Posted by 67Fbird View Post
Typical method for measuring \-----------/

would be part sitting flat and use 2 dowels..... 0\-----------/0

with know diameters and measure over the outside then a little trig per the known angle (45)......onless you have a couple moldmaker ball-pins
https://us.misumi-ec.com/vona2/detail/110300560910/
and a CMM.

Otherwise it's going to take you a minute to do all the set-ups accurately and then figuring per plane.
I know how to measure the manifold using dowel pins; was just trying to save the 5 min setup time. You know, being lazy! But, I had forgotten about tooling balls. That's a great idea. Probably best to use a factory intake vs an old aftermarket one as hopefully they're machined more accurately-- but that's probably wishful thinking.

  #25  
Old 08-31-2021, 09:45 PM
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hahahah...then you trow i running a batch fire system.....where it gives 3 aquirts with the valve CLOSED.....

bigger issue of what size are the holes...I know all mine are for standard dowel sizes! still a PITA .. obviously work in machining?

  #26  
Old 08-31-2021, 10:22 PM
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Quote:
Originally Posted by HWYSTR455 View Post
I would still think pointed down the port towards the valve would be better than pointing straight down at the floor of the runner, or at least that would be my line of thinking. Maybe a 45 degree 'lean', down the port even.

But suspect you're right about not much of a difference. I was parroting what Marren told me in previous conversations. Guess it's more of a general' or 'generic' statement as you mentioned Tom... .
I will add one piece of advice given to me long ago by a Chief Engineer:

"ONE PIECE OF DATA, TOM, IS WORTH MORE THAN 1000 OPINIONS.

Tom V.

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  #27  
Old 09-01-2021, 05:28 AM
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Never thought about combining vectors for the injector nozzle spray. Kinda like compensating for windage at the gun range. The faster the intake port velocity the farther upstream it needs to point?

  #28  
Old 10-16-2021, 12:28 AM
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Quote:
Originally Posted by JC455 View Post
You can contact Mark at http://www.luhnperformance.com/
for more info on getting your own done.
Tell him John sent ya!
Are any of these up and running on engines? Do you know the runner length?

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  #29  
Old 10-16-2021, 11:20 AM
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All of the Offy Manifolds have very short runner lengths.

They built the manifolds for easy installation.

Manifolds tune by harmonics. 1st harmonic length was long, like the old Chrysler
Cross Ram Intakes. See Picture below.

Other Runner Length manifolds were designed for racing speeds.

The Offy intakes fit that situation but are good because of the Injector Placement options, not the tuned length.

Tom V.
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  #30  
Old 10-16-2021, 01:27 PM
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This is an illustration of what a 1st harmonic, 2nd harmonic, 3rd & 4th harmonic waves look like.

Tom V.
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  #31  
Old 11-23-2021, 01:52 AM
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Just as an update I called Luhn about these intakes last week. Unfortunately they are waiting on some small parts to finish them up. Iirc he said he had several (6-7) very close to finished up. I called to inquire of the rpm range of the intake. He believes it will be great in the 1500-6500 rpm range with very strong torque production.

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