Common plenum or individual runners???, for gas milage and drivability Options

[RD Evans]

Here is a link to a custom made manifold that might work with our motors? (IMG:style_emoticons/default/welder.gif)

SDS-FI Manifold

[Mueller]

thanks for the link...nice and simple manifold....i'm thinking with our motors we'd want to add some joints to the setup for expansion.....

[Bleyseng]

Hmm, I thought the intake valves on a 3.2l are 49mm which are much bigger than 42mm stocker. Could always upgrade to 44mm valves....
I trip to a junkyard is in order to look for parts...
Andy, what size does the manifold drop down to at the head flange?

Geoff

[TimT]

This guy makes a nifty throttle alternative "barrel throttles" like slide valves only they rotate.

Jon Milledge

I saw one of the 944s' equiped with this, car was wicked fast...

[Mueller]

pretty damn slick Tim........much easier to seal the "barrels" than a slide...damn professional looking, cannot wait to see what the 911/914/6 version looks like

[DNHunt]

I can't offer much except that about the only thing working well on the new engine right now is the MAP sensor. The old 2.0l with the same sensor and same single throttle body had about 45 kPa of vacuum at 1000 rpm. The 2270 is around 65 kPa. Jake was kidding about a vacuum signature. This thing wants air. I suspect I'll need more throttle body and maybe more plenum.

Anybody thought of a riser on the stock plenum with about a 65 mm throttle body. Easy to make, cheap. You could probably add a couple hundred cc's without too much problem. On the down side you get a shaped column of air aimed at the flat bottom of the plenum you get another gasket and you have to open the top of the plenum up. Also, you loose that nice big air box before the butterfly.

Dave

[Air_Cooled_Nut]

The 3.2 looks way too big!

actually, each individual runner on the 3.2 is only slightly larger than a stock 2.0 runner.
they are the *perfect* size for a 2.1 - 2.3 engine.
in fact, there is a formula that porsche used on all their aircooled FI engines.
using that formula and the displacement of your engine (per cylinder) you can calculate the dia. of a individual runner. (and vice versa) ...

the one thing that is much larger is the volume of the plenum, which is gud ...
(IMG:style_emoticons/default/cool.gif) Andy

Post the formula! Post the formula! Post the...did someone say beer? (IMG:style_emoticons/default/beer.gif)

[Jeroen]

IIRC slide valves only work better at WOT, when there is no restriction to the inlet path

[SirAndy]

Andy, what size does the manifold drop down to at the head flange?

40mm at the flange compared to 36mm on the stock 2.0L runners ...

(IMG:style_emoticons/default/wink.gif) Andy

[Bleyseng]

hmmm, that is damn close then. Someone here must know the ratios....

[Bleyseng]

Andy, what size is the 3.2l TB?
65mm TB Dave, damn thats big! My 3.0l Ranger doesn't even use that although the modguys slap on those to get more hp at high rpms.
So, thats about 20 inches of vacuum then??

Geoff

[Brett W]

The early 90s Honda Prelude which was a 2.0 engine used a 62mm throttle body. It should more than be able to supply the air for a 2270 or 2316. Especially if the plenum is sized correctly. They can be had for less than 50 dollars all day long. The TPS is adjustable and can work with most any injection system.

Barrel throttles do an awful job of delivering a smooth mixture to each cylinder. They vector the mixture much more than do slide throttles or standard butterflies. The benefits to either are at WOT anyways.

The real ticket would be to take a set of Motorcycle TBs and adapt them to work with your injection system. You could run two sets of injectors. Have low mounts for part throttle driving and a set of high mounts for WOT and High rpm work. It would make great HP.

I had thought in the past of building some sort of common plenum kinda like the Ford Taurus SHO unit. A unit with long and short runners so you could get good torque and high rpm power. The Porsche Vario Ram unit works very well. You could use two throttle bodies and stagger the openings for a similar effect.

There is no formula for designing a manifold. You can run a bunch of numbers but you still need to do lots of testing. Most engines can get away with intake plenum volumns of .8-2 times that of engine displacement. Lots of that will depend on the application. The Subaru runs a very small plenum, while some of your F1 cars, GT cars etc, use a pretty large air box on top of an IR manifold. Look at the Carrera GT manifold. dual individual plenums. The Ferrari I believe uses a common throttle body though.

[SirAndy]

Andy, what size is the 3.2l TB?

i don't have my notes handy, anyone here has that number handy?

according to the formula, the ideal TB size for the 3.2 would be ~57mm on the top and about ~52.5mm at the narrowest part of the "venturi" ...

(IMG:style_emoticons/default/wink.gif) Andy

[914efi]

This is what I built for my 2.2E engine. It seems to work well (nothing to compare to). The runners are sized to match the port dia. I have had lots of problems with low speed driveability, but have now traced it to factors other than the manifold. I am using SDS, and it does not do a good job with engines like this that have low vac at idle. The megasquirt system will work better where you can program MP settings at specific rpms rather than just relying on MP signal. This was not out there when I did this, or at least I was not aware of it.

I think I might make the runners a bit smaller in hindsight, since the restriction from the heads is the limitation, and the smaller runners might help the low speed a bit. The TB is from a 3.0L Nissan, and I reduced its dia a while ago to try to get more progressive tip-in. I don't know the actual size, but I can measure if anyone needs it. If you watch your MP at WOT full load, and as long as it stays at atmospheric, you know the TB is not too small.

BTW I have moved the injectors to the ports since this photo was taken. once again for better low speed work. I am using injectors from a 3.2, and this also presents a few problems as the duty cycle is so low at low speeds, that the output can double very quickly.

[Mueller]

914efi, nice DIY job (IMG:style_emoticons/default/smilie_pokal.gif)

a couple of questions if you don't mind...location of throttle body, I don't see it.....do you have any sort of air-horns or radiused inlets inside the main plenum going to the runners? (if not, this could be an issue if the runners just mate directly to the flat sides of the plenum)


Brett, I know the low speed drivability supposed to suck with slide-valves and barral valves, but it seems that using those with a plenum, some of the problems can be overcome.

Dave,

My MS install on the 1.8 w/2.0 heads and 2.0 plenum and a header pulled 55kPa at idle, I wonder if it was due to the more effeicient heads on the smaller bore motor ???

Now, what material would be best to build the plenum out of??? I'd have to say some sort of plastic or non-metal material so that heat soak does not happen as easily.....time to start hitting those websites to learn how to use and make something from carbon-fiber (IMG:style_emoticons/default/smash.gif)

[Brett W]

Mike,
The slide throttles could work fine on a street motor, they would be prohibitivly expensive though. It would work really well with a dual injector setup. I have yet to hear fomr anyone that barrels would work for anything but a constant throttle position like a circle track car. The plenum or lack there of doen't affect the problem of mixture tubulence in the intake tract. It is really bad at part throttle meaning you would have to run extremely rich to possible overcome some of that effect. It is possible that you would have plug fouling issues at street rpm levels. Just use a standard butterfly type throttle. It will be substantially cheaper and easier to work with.

Do a google search for Helmholtz resonator. You should find several sites that discuss it, how to calculate it, and it's effect on a NA engine.

Carbon fiber or some sort of thermoplastic would be the best option. you could do a double wall aluminum panel on the bottom of the manifold and sandwich some fiberglass between the layers and then coat it for more heat resistance.

http://advancedinductionresearch.com/photo_gallery.htm
http://www.advancedinductionresearch.com/
http://enaf1.tripod.com/teche.html
http://www.n2performance.com/lecture1.shtml
http://www.me.psu.edu/me415/SPRING02/intak...ake/intake.html
http://www.grapeaperacing.com/GrapeApeRaci...tionsystems.pdf

[Jake Raby]

I have tested Kit Carlson with I/R on a 2563cc engine.. It worked excellent!

[Air_Cooled_Nut]

QUOTE (Jake Raby @ Dec 19 2004, 12:08 PM)

I have tested Kit Carlson with I/R on a 2563cc engine.. It worked excellent!

(IMG:http://www.914world.com/bbs2/html/emoticons/finger.gif) But since the EFI isn't being sold [w/o engine] to the public that really doesn't help us much, now does it?

[Brett W]

Jake
What Type of injectors did it allow you to run? Peak Hold or Saturated?

[McMark]

QUOTE (Air_Cooled_Nut @ Dec 19 2004, 07:30 PM)

QUOTE (Jake Raby @ Dec 19 2004, 12:08 PM) I have tested Kit Carlson with I/R on a 2563cc engine.. It worked excellent! (IMG:http://www.914world.com/bbs2/html/emoticons/finger.gif) But since the EFI isn't being sold [w/o engine] to the public that really doesn't help us much, now does it?

Yes it is, just not yet. (IMG:http://www.914world.com/bbs2/html/emoticons/tongue.gif)