OK I have recently gotten into fabricating my own stuff. I have the privlage of workign with a machinist/tool and die maker in the army right now.

My question has to do with intake manifold design. I want to make my own but I dont know what calculations to use to figure out Runner Length or Plenum volume. What calcualtions could I use to figure out what woudl be optimum for my application?

 

Hi Chris,

I don't design intakes but have been around a number of people who do. I chew on their ears til they tell me what I want to know.

I look at it like this... the runner size isn't an issue because we are simply going to work from the cylinder head port and apply that same taper or something very similar. The intake runner (intake) is just an extension of the cylinder head.

Now for lengths.... how much room do you have to work with? If you keep the runners straight then chances are you're going to have something shorter than 6". Not to worry though cause from what I read in Cosmo the other day... that's about average.

On the plenum volume, I'd have to go get some of my research materials. There is some info on this over at Larry Widmer's site (TheOldOne.com) or something like that. Just search Google for it. I'll post up some more info later.

On injector angles, alot of the guys I've talked too don't feel they're that important. Then there are those who do.
If you look at Mike Moran and some of those other guys you'll see that whoever built their intakes wasn't too concerned with it either. Even the LS6 head has a little worse targeting than the LS1, but they felt that the port was more important than the targeting. It's an open debate for sure. Then again, some injectors have wider spray patterns than others...

On building.... I'd look at what Kinsler does with theirs and make a valley cover. Just makes things easier to work on when you're in there taking things apart.

Just a few thoughts.

edit: This may help you out.

http://www.theoldone.com/archive/

-Mindgame

 

I know nothing about this but found this site. might help might be not.
http://snow.prohosting.com/~johngift/intakefab.html

 

Wow that's ummmm nevermind.

 

This is my 1st impression.

People will build things but man... some of them sure are ugly.

edit: Oh... that really threw me bad. Meant to ask a question.

Is this intake for FI or is it going to be carbureted? The plenum volume for carbureted is much more critical than that for FI.

-Mindgame

 

Nice MG!

Really good link you put up thanks... I never new baking soda and super glue did that!

Bret

 

Definitely different! I kinda liked the end product...kinda.

 

Not only does that intake probably weigh 50-60 lbs., but did you see the hole he cut in his firewall to clear the back of the plenum? Nice.

http://snow.prohosting.com/~johngift/On1.jpg

I've heard/read that intake plenum volume should equal the displacement of the engine it's feeding, but I can't verify that one way or the other. Hogan's Racing did my calculations for me.

 

yeah at least that much... the larger the pleanum the smaller the TB you need. No wonder a LT1 intake needs a monoblade

 

What is your application?

 

Well the application isnt set in stone yet. When I get back from Iraq I am going to be Building a "street legal" (i use that term loosely) Race Car. My ideas are either an Lt1 OR LS engine (I might go with a 5.0 or 32v 4.6, but I am a GM guy at heart, just might be a cost effective thing) I will be running it in the Silver State Classic (130 mile race on NV highways). It might also see some SCCA racing and some time at the drag strip. But the car will not be ment for normal street driving.

Also I have a Jeep Cherokee 4.0L striaght 6 that is turboed which I want to do as many custom things as possible to. Its a Typhoon/Syclone (and WRX and EVO) killer. who would suspect the Cherokee

 

It will definetly be EFI. Damn that was exactly what I was looking for. I am trying to gather all the info I can right now so I can have everything planned out before I start building.

Oh mine wont be that heavy. I like Aluminum and have access to a CNC machine. I just have to learn how to program the thing first LOL

 

I have my intake harmonics chart at the bottem of the page. I have some other stuff you might want to see, If I can find it.

 

Here is a use full one.
http://www.rbracing-rsr.com/runnertorquecalc.html
That's all I got.

 

wonder how much boost that anchor will hold