Sheet Metal Intake Manifold - Design Question

[jaybnve]

I'm taking a stab at building a sheet metal intake, but I don't know how much taper to put in the runners. The ports in the heads are round, about 2.25" in diameter, and the runners will be about six inches long. Assuming I match the port dimensions at the head, what should the diameter of the runners be at the plenum? Is there any formula available to calculate this, based on engine speed range or displacement? Also, does anyone know how sensitive the manifold will be to this parameter? Thanks in advance for all replies!

[JeffMcKC]

Re: Sheet Metal Intake Manifold - Design Question

Jay I think my pipemax program has some of that It also give length of runner measured from intake valve to plenum. I will look at noon, I was told because I am doing the same thing on mine that a larger stroke likes more taper from engine builders I respect but it was trial and error for them

[jaybnve]

Re: Sheet Metal Intake Manifold - Design Question

Jeff, thanks for taking a look at that for me. Here are some more specifics on my combination, in case it will help. Stroke is 4.600", cubes are 585", distance from intake valve to intake mounting surface of head is 3.5" along the centerline of the port, peak RPM is 7000, peak HP RPM is 6500, and peak torque RPM is 5500. Thanks again for your help - Jay

[JeffMcKC]

Re: Sheet Metal Intake Manifold - Design Question

Jay, if you want a complete pipemax on it, I need :Bore, true comp ratio, valve stem dia Intake& exhaust, valve dia. In & EX cam lifts and duration@50 and lobe sep. int & ex, and what your installing it at, exhaust from valve to port , what size header,. It will give you a lot of info. You can PM it if you like.

[milner351]

Re: Sheet Metal Intake Manifold - Design Question

keep us posted on this Jay - this sounds very interesting.

pipemax is likely the best way to go about this - there are some really weird things that happen with fluid flow dynamics in pipes - especially when you mix fuel with the air.... I'm assuming this is a carbed intake?

Do you have Heywood's engine books? He's a Dr at MIT - we used his books in college and he is paid by many of the OEMs to give classes on site - his books are available through SAE and other sources - there is a two volume set that goes into all kinds of combustion theory and includes many examples and equations.

Some of this design ends up being forced by geometry and space available under the hood scoop - but there are ratios that should be considered when designing the volume of the plenum in relation to the diameter and length of the runners....

What cool project!

[JeffMcKC]

Re: Sheet Metal Intake Manifold - Design Question

PipeMax is a program adapted from a pipe organ tuning program it takes in acount only air flow its mainly used for headers and collectors with great results, It also tells the intake lenghts and runner size to use the pulse wave from the water hammer effect of the intake valve closing


This is another good one

http://www.enginedesigner.com/index.html

There is a free version to try

[CTX-SLPR]

Re: Sheet Metal Intake Manifold - Design Question

I have an Excel version I built for tuned port harmonic calculation. However it does not do pipe diameter.

[revolutionary]

Re: Sheet Metal Intake Manifold - Design Question

I've been playing with Pipemax as well and it is a really worthwhile investment if you are planning on building an intake or headers.

[Dynoroom]

Re: Sheet Metal Intake Manifold - Design Question

Hi Jay, Plenum volume is another area that needs to be looked at. With the deck height you have this will make it easier to try different volumes. Since the engine will only see maybe 75-7800 rpm I would try a plenum with roughly .75 the displacement as the engine. You can add spacers to see how it affects drivabilty. This is not a real big issue with efi though.

Thanks for the update on the bore centers, real interesting. I don't think you're going to have any issues with the voids after the sleeves are installed the way you're going to do it. Looking forward to talking to you more about it soon.

Have fun & Good Luck!

[CDMBill]

Re: Sheet Metal Intake Manifold - Design Question

I would think you would want to be replicating a tunnel ram type manifiold if hood clearance is not an issue. A look at the Hogan's catalog show a number of dual throttle valve inlet as well as some cross-ram style with a wide relatively flat plenum, single throttle valve, to preserve runner length. The wet or dry question obviously plays a huge role. EFI would make this a whole lot easier proposition.

Hmmmm 2.25 round intake ports? That suggests only two heads that I know of....

[CTX-SLPR]

Re: Sheet Metal Intake Manifold - Design Question

doing a sheetmetal intake has to be a nightmare for FE motors.

Sorry for the side track, I can send you my excel version and you can play with it if you like. It might not be the most intuitive thing though and it only does runner length though I did try some pipe sizing stuff but really don't think I have much beyond the hydrallic diameter done with any sort of accuracy.

[JeffMcKC]

Re: Sheet Metal Intake Manifold - Design Question

Jay, make sure you figure out how to not have warpage become a problem. I just lost 1000.00 on mine, no time to try to fix it before Drag Week, so Monday I will get a 300 tall block intake, to mill down to fit. 1700.00 and TRE will build any manifold you want.

[squirrel]

Re: Sheet Metal Intake Manifold - Design Question

ouch! bummer.

[JeffMcKC]

Re: Sheet Metal Intake Manifold - Design Question

Yeah, taking some arrows on this one. The .300 tall intake has larger runners I think I can mill down the intake gaske face to drop it down to a std. block, and still have a larger runner with a 4500 top

[jaybnve]

Re: Sheet Metal Intake Manifold - Design Question

Sorry to hear about the intake blues, Jeff. I've been there / done that once before, when I built a sheet metal intake for my high riser engine. I was going to address the warpage issue by welding it together while bolted to a dummy engine, but my 180 amp TIG welder was not up to the drill. So, I had to weld it on the bench, and it warped like hell. I ended up welding big donuts around each port, and then remachining the base of the intake to make it work.

Since I have zero time to do the intake for this new engine, I'm going low tech and building it out of steel. I'm having a local steel place laser cut all the pieces from my CAD files. I also bought Street rod exhaust megaphones from Speedway that just happen to have the taper recommended by the Pipemax program (I broke down and bought a copy, by the way). So, I'm going to take a stab at a one day sheet metal intake! Once I have all the laser cut pieces, I just have to cut the megaphones to length, tack it all in place while bolted to an engine, and then fry it all together. Then it will go onto the mill for machining the EFI bosses and rails, and finally off to my machine shop to cut the flanges to eliminate any warpage issues.

I have exactly one day I can devote to the sheet metal intake project, and still make it to Drag Week with it mounted on the engine. Otherwise, I have to go to a different induction system. Wish me luck :D