Anyone build one? (open mouth insert foot) Looks like it'd be really easy... Seeing the power gains from FM and BEGi's aftermarket manifolds just something that I'd be interested in trying.

 

It's been done. I've seen a few of them around. It's not a real popular mod though for some reason. If you can make up the flange then it shouldn't be hard at all. You can even get aluminum plenum that just needs ends and runners with flange welded on.

 

something i plan on doing much later this year
i am planning to use OEM manifold and cut the flanges off and make my own plenum and runners and weld it all up
goal is to incrase plenum volume and runner thickness and to make them shorter than stock

 

Think the reason for this is just the labor involved or people just don't think its worth messing with?


This was something I was thinking about, grab an escort or Protege mani from the junk yard and slice off the "flange" basically with injector bosses with a bandsaw. Get some aluminum tubes for runners and a rather large aluminum tube for the plenum with a good sized throttle body, something like a BBK 70mm for a 5 liter.



I'm trying to find an article I read several years ago about the volume requirements of an intake manifold but can't seem to run it down..

 

I think it's mostly because people are getting 200+ horsepower without them and don't want to run much more than that most of the time. The people that want crazy power end up with a new intake mani, like MarkP for example and 1badmx5. Both of those guys want 400 and 500 HP respectively.

The cost and knowhow is the most limiting factor i believe. They're not real easy to just throw together with a flux core in your garage so i can understand why people don't do more of it. I personally won't be using one anytime soon.

 

i already have a spare manifold, its just a matter that i dont need it yet
once i build my motor and want some serious power ill do it, but for now im ok with the stocker

 

Paul made 271 HP at 14 psi with a 2560 with the stock mani, i think you'll be alright. It would be a nice upgrade when time and money allows though. Though headwork would probably be even more beneficial. I don't know myself though.

 

Dunno, almost sounds like it really isn't worth the time. What Head and bottom end was paul using?

 

I think it's something like 2 or 2.5 times the engines displacement.

So something like 3.5 to 4 liters for a miata.

 

Do you recall if thats TOTAL volume, or PLENUM volume? Any specific volume for the runners required?

 

stock 99 head and bottom(EEK!)

VICs system not operational.

 

Heh, i was in point pleasant beach couple days ago...

Anyways... we made one just because we wanted too. Should see gains, heck... I expect them... but the build was never about numbers.

We made this...

 

I have cad pattern for 99 head and a few flanges cut out from mild steel.
Flanges I need as spare until mine IRTB gets finished, might be a while though.

hrk

 

I went with the stock throttle body cause I don't think you need a huge TB for turbo forced induction unless you're thinking of sick power. Part throttle driveability may be alittle twitchy. There's inexpensive honda throttle bodies in the 62-65mm area if you must go a little larger and may be easier to package.

I built my intake not for performance but to practice welding aluminum and to allow me to run my intercooler pipes thru the fender and away from the hot radiator. It'd be easier/smarter to just do an over the radiator setup but I'm not smart. I reused the lower half/runners of the factory manifold; the runner length is basically the same as stock. I used a bandsaw to cut off the pleninum.

It takes a lot of time and a welder with a really really high current capability. I used the huge lincoln tig they have at work for welding aluminum cylinder heads. My "little" TIG185 couldn't handle the current by a long shot.

I could go with a larger TB by just hacksawing the TB flange off and welding another on with the proper mustang or honda bolt pattern. The manifold is all 1/4" aluminum except for the TB flange which is 1/2".

Pics:




More at the bottom of this page:
http://www.shoremotorsports.com/MiscProj.htm

 

Increasing the plenum volume may not be a bad idea, however shorter runners may be counter productive. You'll see torque gains at low- to mid-RPMs with longer runners. The turbo will more than offset the inefficiencies at the higher RPMs. Between the two you should smooth out the power delivery.

Corky and I have been (occasionally) talking about designing another intake manifold. He isn't completely happy with the current version. (See MarkP's set up.) We're not certain where the deficiency is in the design, but I have a couple of ideas I'm wanting to try once we get my car back on the road.

As to "tuning" an intake, the idea is to time the air pulse to be pushing (not rebounding) on the intake valves as they open. So, the length of the runner must be an evenly divisible fraction of the distance the pulse will travel at a specific RPM. - Thus the efficiency is aimed at a small RPM band.

- L

 

Here's a good thread to look over if you wanna build your own intake manifold:

http://www.galantvr4.org/ubbthreads/...31&Main=554229

Enjoy

 

Cool link, thanks!

 

It's worth getting it running IMO. I have back to back runs on my website of it operating and not operating. Very noticeable and repeatable improvement.

 

Man. What a difference. Is that with stock engagement or with you controlling it to turn on at a certain RPM?

 

You know I can't remember exactly, but my testing showed that the best switch point was close, or a little above, the stock position. About 5300-5400rpm IIRC - my graphs don't cross there mainly I suspect due to smoothing carried out in DLL. I can take a look at my TECgt file later and let you know.