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Welding Class - Final Project - L Intake Manifold


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After using a handy dandy calculator.. I determined that with my camshaft.. w a 260 duration.. and the ID of 1.375".. and a desired peak torque at 5,000 RPM.. The runner should be about 6.39" long. This length will allow the intake waves to hit their 9th pulse. To choose every 8th pulse.. the pipe should be 7.275" long.

 

Nascar uses the 3rd intake pulse.. If I wanted to use the 3rd pulse.. I would be looking at a length of around 20" inches!!

 

this is the link to the calculator!

http://www.velocity-of-sound.com/velocity_of_sound/calculator3.htm

 

 

The pics are from my mock up stage. I believe the runners are 6.5" long right now. I measured 16" inches from Cyl 1 to the strut tower. and 14" from Cyl 6 to the heat shield. My pressure plenum will be interesting to build lol. I only need to weld up Cyl. 3 and Cyl 4 now.. then the manifold will be complete. then turbo time!

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Pr0x... the pipe is actually calculated from valve seat to runner inlet.

 

take a string, and put it under an opened valve. mark it, fasten it by either closing the valve or taping it down, and then measure the proper length and see where you'd like it to go based on engine height in the engine bay.

 

20 inches from the valve seat is something like 14 inches, including throttle bodies, so in reality, the stack will be somewhere around 5- 8 inches.

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Ok I recalculated..

 

from the center of the intake valve.. to the throttle boddy.. is 11.2" inches.

 

With my ID (remeasured its 1.4" not 1.375) and my length.. I will hit the 5th intake pulse, with a peak torque of 5350 RPM!

 

Hmm.. works out perfect since the L series runs out of breath at 5,000 RPM...

so hopefully this manifold will increase the airflow and extend the power range =)

 

I wont be cutting the runners at this time.. how about a second opinion?!

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Ok I recalculated..

 

from the center of the intake valve.. to the throttle boddy.. is 11.2" inches.

 

With my ID (remeasured its 1.4" not 1.375) and my length.. I will hit the 5th intake pulse, with a peak torque of 5350 RPM!

 

Hmm.. works out perfect since the L series runs out of breath at 5,000 RPM...

so hopefully this manifold will increase the airflow and extend the power range =)

 

I wont be cutting the runners at this time.. how about a second opinion?!

 

Hi Pr0x.

 

If i may make a suggestion regarding chosen RPM/tuned frequency.

 

I used a program called Dyno2003 (PM me if u need it), and I input the parameters as close to my engine setup as possible (RB30/26). Within the programs out-of-the-box settings, there seems to be a multitude of L Datsun engine setups that you could try.

 

Add a turbo in the forced induction section, and it will give you a close indication of what the final output horsepower would be... give or take 20 or so (can never be too sure... real world differs immensely at times).

 

It also shows you torque output. Both in the form of a dyno graph.

 

I would then find out what place the most horsepower is being made and tune it for 500 to 1000 rpm before that sweet spot, so you can dig some grunt out from under power-band to get you back in there faster or provide a bit more response leading up-to that point.

 

Not sure if that would help in any way, but it's better than just a shot in the dark with the 5000 rpm flat spot assumption.

 

There are a lot of N/A L's that make power well above that.

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well im an idiot.. and I made the runners too long. and because I cut the pipes at angles.. if I cut them any shorter.. my spacing will be wayyy off.

 

Soo for my plenum.. I have a 4" wide base.. and a 4" diameter pipe.. I cut the pipe in half.. so its a D shape plenum.

 

But thats 2" in height..

 

Is this plenum too small?! im reallly worried about the volume.

 

I calculated the following.. volume = 3.14 x R (squared) x h

 

Soo.. a 4" pipe.. has a 2" radius.. which is around 301.59 cubic inches at 2 feet long.

Cut that in half because I cut the pipe in half is 150 cubic inches!!

 

the stock setup.. is a 2.5"x2.5" style plenum.. soo after the thickness of the wall.. i would say 2.25" by 2.25".

Volume = L x W x H

 

The stock intake at lets say 2' feet long.. is 121 cubic inches!!

 

Soo my plenum has 30 cubic inches more volume then stock?! ahh ♥♥♥♥ is this too small?!

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Well.. I spent $20 on a 5 foot length of 4" tubing... for some stupid reason. and already cut the piping and had it set up for the plenum I wanted. Then I measured it all and realized i made a big big boo boo

 

Id prefer not to buy more materials.. I will just weld up my own square plenum. =(

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for a high boost setup 1.5 times the volume of the engine is supposedly ideal, or good enough if supplying all the cylinders.

 

then again, some of the lower profile ITB Race V8's that I've seen look like they'd fit about 2 litres of fluid and are supplying high revving 2.5 or 3.5 litre engines if I'm not mistaken.

 

but it could just be a visual anomaly that makes it look smaller than it actually is.

 

Did you find out max torque/hp in dyno2003

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Ok.. im trying to figure out the best way to use 180 degree curved runners..

 

I am debating between silicone and aluminum..

 

a 180 degree bent 2" o.d. aluminum pipe is $35 a pop! and I need 6 of them! ugh! http://www.fortune3.com/Slomo/180_Degree_Bends-Vibrant_2_O_D_Aluminum_U_Bend_Polished_1.html

 

another option is a 180 degree silicone elbow which is also around $35 ..

 

Soo thats another $200 for this project and this design! UGH!

 

Any other suggestions?!

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Ill be honest, I have no idea what your doing. I wish you had photos or something of the problem.

 

I am also a member of the measure 6 times, cut once, and still have it too short family. Welcome.

 

Now that I am done giving you a hard time, check out these guys.

 

http://store.racing-solutions.org/albe1.html

 

They mandrel bend aluminum tubing. I bought a bunch of mild steel bends, quality is very good as is pricing. You should call them and dont have DHL ship them. It took FOREVER.

 

Good luck dude - Evan

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LoL Evan..

 

 

I am NOT using a Nissan Maxima Diesal intake manifold...

 

I will have a very similar design to the Diesal intake. I will be using my own flange, runners, and throttle bodies for this project. In order for my plenum to fit my manifold.. I need to flip the plenum ontop of the runners... just like the Maxima Diesal design.

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