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Posted by: Mueller Dec 16 2004, 10:04 PM

for my 2316 it seems that the stock plenum might be reaching it's limits as far as volume goes.....so, I either fabricate a larger common plenum, or go with individual throttle bodies such as TWM or http://www.jenvey.co.uk/

single plenum would be easiest, but the individual throttle bodies look better

has anyone switched from one to the other on the same motor with everything else being the same???



*Jake Raby is the U.S. distributor of these....

Posted by: lapuwali Dec 16 2004, 10:18 PM

Biggest problem with IR throttles is getting a good MAP signal for the EFI. You need to fab up a plenum just for the MAP signal. You never need to balance a single throttle body, either. No linkage worries. Fabbing up a bigger plenum that used the stock runners shouldn't be too big a deal. Use a bigger throttle body off some other EFI car.

Posted by: ottox914 Dec 16 2004, 10:18 PM

Here is another place to check for FI throttle bodies, manifolds, and injectors: http://redlineweber.com/Redline1.htm
I have been interested in the same question for a while- general answers I get are that the longer runners/larger single plenum can be designed to boost low/mid range torque, while the I/R throttle bodies will help the top end. Might be a "package" sort of decision, thinking about valve sizes, cam, redline, etc. Jake had a thread awhile back about testing intake velocity stacks, and found 2.5" to be the best overall size, so if you go I/R this might be worth keeping in mind.
As far as real world experience, got none to share, only opinions at this time. I'm not the smartest nut on the workbench, but am working my way thru "Scientific Design of exhaust and intake systems" third edition, by smith and morrison. It'll take a while for it to all sink in, but interesting none the less.

Posted by: Bleyseng Dec 16 2004, 10:41 PM

Based on what? Have you done the math? Brad ever built something like that and it didn't work??

DaveHunt's 2270 is supposed to be running tonight and he should get it tuned soon sooo we'll all know if a 2.0l setup can work well.
Charles from L/N told it should work but maybe suffer alittle at high rpms. So, how high you gonna rev this thing??

Geoff (looks like I am heading down this slippery slope also)

Posted by: rdauenhauer Dec 16 2004, 10:56 PM

Im not smart enough to follow this ...
Why would the collection of intake air in a larger common cavity enhance mid & torq as compared individualm properly sized TB's?

Posted by: Bleyseng Dec 16 2004, 11:01 PM

air velocity I think. Under lite vacuum at cruising the plenum is a large supply of air already past the TB. Duals is great for WOT.
Thats why the throttle response it so great with a Djet set up vs Dual carbs.
or I am talking out my ass...........

Posted by: Cloudbuster Dec 16 2004, 11:10 PM

The general gist is short intake runners for high RPM, long runners for low RPM. It isn't just the piston downstroke that moves air into the cylinders, it is the masses of air moving through the engine as well. At low RPM, with low piston velocity and intake pulses stretched out, lengthening an intake runner creates a reservior of high(er) momentum air to help fill the cylinder.

I think that valve overlap is another thing that assists in cylinder filling, where both valves are open at the same time so that the outgoing air charge is creating a vacuum on the incoming charge.

Dual carbs with IRs probably have poor low RPM response due to low intake velocity, hence poor fuel atomization. (Now I'm talking out of my ass too)

Dual-length runners systems are what made the Corvette ZR-1 and the SHO Taurus great (if it wasn't sales hype)

Posted by: Mueller Dec 16 2004, 11:55 PM

Geoff,

Based on another thread in which Jake mentions it on Dave’s motor, mine will be larger and if his is already on the brink, then mine would reach the limit even sooner

Just 'cause Dave’s car runs, it does not mean the plenum is sufficient in volume, he won't know for sure until he cranks up the RPMs.....one way to know whether it works fine is how well the car responds at WOT, too much vac. at WOT and it could indicate too small of a plenum (the throttle body could do this as well, but I know he has a larger throttle body to help)

Posted by: Bleyseng Dec 17 2004, 12:17 AM

The difference between a 2270 and a 2316 isn't that much is it? You can always add a bigger TB onto the 2.0l plenum for better WOT flow, say a 55mm one. Just ream out the hole some.
I spoke with Jake and Charles the other night and they feel they can come up with a cam that will work with my new setup (103x71 using Nikkies and Djet intake, 45mm TB)

Posted by: ottox914 Dec 17 2004, 08:25 AM

My very basic understanding of plenum and runners VS throttle bodies: when the intake valve closes, the incoming air charge is still on its way, hits the closed valve, and bounces backwards thru the intake runner and into the plenum. By doing the math (not my strong suit) you could take in to account the speed of the "bounce back", the volume and shape of the runner, size of the plenum, and calculate lengths for runners, and capasity of plenum, such that when the incoming air charge bounces off the plenum, and rushes back down the intake runner, that it gets back to the valve as it is opening again, resulting in better cylinder filling, sort of a "super chargeing" of the intake charge. Down side to this is that is is pretty rpm dependent, based on length of runners and timing of valves opening/closing, hence some cars w/variable length "tuned" intake runners. The individual throttle bodies, if run open topped, have nothing for the charge to bounce back off of, but do offer lots of air flow and a more direct path at higher rpms. If they are run w/air cleaners, again, the overall length of the intake, from the top of the air cleaner (or thorttle plate?) to the valve is likely to be less than the stock T4 system, and the bounce back effect happens faster, and therefore provided more benefit at higher rpms, when the valves are open/closeing faster.

Thats all I think I know, if someone knows more feel free to correct me.

Posted by: Jake Raby Dec 17 2004, 08:54 AM

Bleyseng,
I have never had ANY engine that I could not design a proper cam for! The D jet that you are using is much more tricky and that cam will have split centers, split lift and split duration, so it won't be cheap! I do have 4 different masters we can work with and some data from Djet tests in the past to compare. Using the Djet SAFELY will sacrifice duration which will boost vacuum (atleast on the intake side) this will cost you drastic power of the potential of the combination using something else_Kit Carlson or Carbs... But If you really wanna use it, go for it- but its uncharted territory!

Getting a proper vac signal for the IR runners is easy. I have already found in the Kit Carlson testing the size of the vac ports needed as well as the hose and small collector that works best as well. One of the test engines that made the best power was an IR set up that actually idled and fired up with low speed operation better than the plenum based version in my 912E.

BUT you need the correct cam designed to make this easier- Yet again no problem because I'm a cam specialist on these suckers! Its just come from trial and error!

All the guessing and planning in the world and trying your heart out to get it perfect ain't gonna cut it! Unless you use a 100% proven arrangement that has all the bugs worked out and has EVERY part that was used in that arrangement installed- You can make a goof....

Don't be afraid of making goofs- If you are don't try it and pay someone else that is. Its impossible to build it perfect! It can ALWAYS be better! Take it from me, the guy that has torn a particular engine down 18 times making nothing but a cam change to find out the heads were the limiting factor because the ports and valves were too big! The issue looked cam related, but it wasn't.

Build it, drive it, and if you don't like it tear down and change it- OR get a full set up 100% designed to work and you better not complain about the friggin price, because all guesswork is removed and thats worth DOUBLE the cost alone!

BTW, I'm the only US based dealer for Jenvey TBs. I have exclusive rights to thier goodies and they are being added to our line up as we speak.

Take this seriously guys, but understand its never gonna be perfect-

Posted by: Bleyseng Dec 17 2004, 09:02 AM

Jake, I am going with the Megasquirt setup but retain the djet intake set up. If it doesnt work, well I have a set of Dells sitting on the shelf.
If Dave Hunt can't get his to run right I will be changing my direction.
Geoff

Posted by: Jake Raby Dec 17 2004, 09:11 AM

I'm sure he can make it run right, but the question is will the engines VE have to be sacrificed to do so???? If it needs weird VE numbers to be drivable and stay cool it will suffer in the performance arena.

That VE table will tell the tale.

The plenum that Charles and I have been working on will be sized for 2250-2320CC engines specifically.

Posted by: Bleyseng Dec 17 2004, 09:15 AM

Ok, 'bout how much more Volume do you think it will take.(so I can imagine this in my head). Double? 50%? 60mm TB?
Geoff

Posted by: Jake Raby Dec 17 2004, 09:41 AM

Posted by: Mueller Dec 17 2004, 11:27 AM

I like that additude

Guess I'll be going the IR route....like you said, if it does not suit me, replace it with something else till it does

Posted by: jwalters Dec 17 2004, 11:38 AM

This si the same technology all the japanese bike makers use to squeeze every last iota of power from the tiny engines...point:

Testing has showed and confirmed that having the largest Airbox possible slows down the intake velocity and turns it into pressure-----

Further testing has shown and confirmed that the use of a decent sized airbox coupled with a large plenum has the same effect--

On these engines as well as any other high rpm / high power engine the speed of the air being "sucked" into the carbs are approaching or exceeding the speed of sound--this is not good--high velocity means low pressure, think of it as a carb venturi--by being in the transonic range ( just prior to going supersonic) and pushing thru S/S, negative pressure waves develope which can in the right instance actually stop and restart the flow of air up to 100k times per second.

Which gives very poor performance and causes aircraft jet engines to " flame out" i.e.-...not run at all.

Too much velocity is bad juju-----

Posted by: Jake Raby Dec 17 2004, 12:03 PM

The only true test is in the driver's seat....

100% of what I have developed has been proven this way...

Most of what I have was developed was done before I ever owned a dyno.... Including the camshafts- Thats why they are so damn effective in the driver's seat..

Posted by: SirAndy Dec 17 2004, 03:26 PM

single plenum ...

use a 3.2 upper intake and cut off 2 of the runners.

the dia. of the runners is a bit bigger than the 2.0 runners, perfect for anything from 2056 to 2316 (according to my pre-school math).
the 3.2 plenum has much more volume over the 2.0 plenum, which is gud.
also, the runners are much longer, promoting low/mid range torque.

all you need to do is find a set of short dual carb runners and mate the 3.2 intake to them. they're only about 3 mm off.

i went through this whole setup for my 2056, did all the math/research.
just haven't deceided yet if i'm actually going to use it ...
Andy

Posted by: nebreitling Dec 17 2004, 03:51 PM

that's a brilliant idea, andy.

Posted by: Bleyseng Dec 17 2004, 05:36 PM

Got a pic of what you are talking about?

Posted by: SirAndy Dec 17 2004, 05:57 PM

yes.


take a 3.2L upper intake with TB and cut it along the green lines in Pic 1.
take off the 2 front runners and weld the plenum shut.
the mounting position of the remaining runners (yellow arrows in Pic 2) alomst perfectly mate on a dual carb intake (yellow arrows in Pic 3).
they're only a few mm off on each side, so it would be easy to make a small adapter to mate them together.

you can use the 3.2 TB, Air Filter, the fuel rails and injectors and just run a MS Brain for the Injection ...

Pic 1:


Pic 2:


Pic 3:

Posted by: Jeroen Dec 17 2004, 10:16 PM

Mike, do a search on the pelican taildraggers forum
Some guys there are modifying motorcycle throttle bodies (which can be bought cheap)

Posted by: Mueller Dec 17 2004, 11:27 PM

thanks...read 'em all and now I'm on eBay

Posted by: Qarl Dec 17 2004, 11:40 PM

http://www.abdgraphics.com/iansite/ianthrottlebody2.htm

Schweet!

Posted by: SirAndy Dec 18 2004, 02:33 AM

trust me, you want a single TB ...

Andy

Posted by: Brett W Dec 18 2004, 08:07 AM

The common plenum system will make more power than an IR manifold. The IR will allow instant throttle response, therefore making them a much better choice for a situation where rapid and frequent throttle position changes occur.

While I was at work last night, I was thinking about coming up with a couple of prototype Common Plenum manifolds. I was trying to decide what throttle bodies and fuel injectors to set them up with. The Djet stuff in my opinon is not a good choice for fuel management, but Kit Carlson might be up for the task.

What kind of interst would I see. Since I don't have a running injected car, and am not planning on building one anytime soon, I need someone to do some testing. Jake, got anything running Kit Carlson with an engine with more capacity, 2270+.? Here is the problem. IT would only work for a teener, because anyone running any kind of Upright cooling system would not be able to run this. Don't think I want to try and design one for an upright motor.

Posted by: Mueller Dec 18 2004, 01:31 PM

why???

some of the new BMW's use what appears to be a combination of both, individual throttle bodies just a few inches away from the intake ports, but all of the t/b share a common plenum for the air?


Brett,

I think the best choice for the throttle body would be something from a newer car that has aftermarket support for....I've noticed on eBay, a bunch of Ford Mustang and Focus throttle bodies, both stock and aftermarket such as BBK


Now about the placement of the throttle body if going with a plenum design???

cross off how the 1.7/1.8s are mounted......the 2.0 seems like it would be ideal for even flow, but it sure as hell looks goofy with the t/b just sitting up on top.....having the intake on the underside of the plenum similar to 928s (and even some Cosworth Indy motors) is an option, but you have to worry about clearance between the motor and the t/b...also there might be an issue with heat and also the overall height of the plenum would have to be higher for the t/b and aircleaner/ducting

now we go back to the intake that Andy posted, do we want 2 seperate plenums connected together with the t/b in the middle or make one single plenum with the t/b mounted to it (top like 2.0 or front, similar to a newer GM V8)??

Posted by: Aaron Cox Dec 18 2004, 01:42 PM

heres a wild thought....use carb manifolds.... weld injector bungs on them.... make a common air box that has a throttlebody on it and connect it to the two carb manifolds

Posted by: TimT Dec 18 2004, 02:09 PM

Mike the GT3RS we just tore down has a big box plenum, that sits on individual throttle bodies.

The air intake is tuned with different restrictors that are plaed at the air inlet for the plenum...

Ill shoot some pics. its all carbon fiber and say Porsche Motorsports on it

Posted by: Mueller Dec 18 2004, 02:17 PM

that is sorta what Andy posted...the question(s) is how to make the plenum and of what design?


here is my 1st grade type sketches


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Posted by: Mueller Dec 18 2004, 02:21 PM

interesting....how much difference in area do the restrictors have between each other??

Posted by: Aaron Cox Dec 18 2004, 02:24 PM

beautiful drawings

pony up for the jenveys and be done with it

Posted by: Bleyseng Dec 18 2004, 03:25 PM

Aaron, I was thinking along those lines last nights as I have a set of carb manifolds on the shelf. Just need to get some tube bent, weld on some flanges and bolt that to the manifolds. The plenum could be anything and weld on a TB. The sizing is the key as how big should stuff be?? The 3.2 looks way too big! I read that the runners should be about 10% larger than the intake valve or velocity suffers.

Geoff

Posted by: Aaron Cox Dec 18 2004, 03:26 PM

cool...im not the only crazy one then

Posted by: SirAndy Dec 18 2004, 04:32 PM

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 ...
Andy

Posted by: Mueller Dec 18 2004, 05:09 PM

the 3.2 upper might work, my issue with it is that's going to be ugly


Andy, any thought on the single t/b plenum verses a single plenum with multiple t/bs such as the car Tim mentioned?

Posted by: SirAndy Dec 18 2004, 05:25 PM

i believe that as long as you have a single plenum to draw air from (all cylinders share the plenum and therefore are connected), both versions should produce good results.

the multiply TB/one common plenum setup will probably give you faster throttle response but then you have to deal with syncronizing 4 TBs ...

as far as *ugly* goes, we all know that beauty is in the eye of the beholder ...
Andy

Posted by: Aaron Cox Dec 18 2004, 05:34 PM

beauty is in the eye of the beer holder

Posted by: Mueller Dec 18 2004, 05:59 PM

hmmmmm, I wonder if a setup like this would make slide-valve throttle bodies work better thru out the entire rpm range????

Posted by: RD Evans Dec 18 2004, 06:32 PM

Here is a link to a custom made manifold that might work with our motors?

http://www.sdsefi.com/air12.html

Posted by: Mueller Dec 18 2004, 06:39 PM

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.....

Posted by: Bleyseng Dec 18 2004, 06:49 PM

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

Posted by: TimT Dec 18 2004, 06:54 PM

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

http://www.jmengines.com/throttle.htm

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

Posted by: Mueller Dec 18 2004, 07:28 PM

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

Posted by: DNHunt Dec 18 2004, 07:50 PM

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

Posted by: Air_Cooled_Nut Dec 18 2004, 08:29 PM

Post the formula! Post the formula! Post the...did someone say beer?

Posted by: Jeroen Dec 18 2004, 08:47 PM

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

Posted by: SirAndy Dec 18 2004, 09:45 PM

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

Andy

Posted by: Bleyseng Dec 18 2004, 11:04 PM

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

Posted by: Bleyseng Dec 18 2004, 11:16 PM

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

Posted by: Brett W Dec 19 2004, 12:38 AM

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.

Posted by: SirAndy Dec 19 2004, 12:45 AM

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" ...

Andy

Posted by: 914efi Dec 19 2004, 08:37 AM

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.


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Posted by: Mueller Dec 19 2004, 12:21 PM

914efi, nice DIY job

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

Posted by: Brett W Dec 19 2004, 01:55 PM

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/intake/intake.html
http://www.grapeaperacing.com/GrapeApeRacing/tech/inductionsystems.pdf

Posted by: Jake Raby Dec 19 2004, 02:08 PM

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

Posted by: Air_Cooled_Nut Dec 19 2004, 09:30 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!

But since the EFI isn't being sold [w/o engine] to the public that really doesn't help us much, now does it?

Posted by: Brett W Dec 19 2004, 10:36 PM

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

Posted by: McMark Dec 20 2004, 01:12 AM

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! 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.

Posted by: 914efi Dec 20 2004, 07:36 AM

Mueller, The TB is just visible at the left rear of the plenum box, it is mounted to the side and faces to the left. It is under the rear lid a bit also. This was a tight fit in the 914.

I have this in CAD if anyone wants the file (Cadkey), I could make a step or iges. One useful thing in this file are the locations of the ports and some of the engine details.(911)

I do have radiused ends on each runner. The runners are welded into the plenum, and then the 'horns' are epoxied on through the cover. The runners are all equal length, they protrude into the plenum different amounts depending on location.

I will take a more current picture and post it. This was built 4-5 years ago before the boom in this stuff really happened. I gues it still hasn't really happened. The megasquirt seems to be getting more people involved.

Posted by: 914Timo Dec 20 2004, 08:05 AM

Nice job, 914efi

Send more pics.

Do you have any pics from the inside. That would be interesting.

Why didnt you 3,2L intake ??

Posted by: 914efi Dec 20 2004, 08:55 AM

I bought a 3.2 intake on the advice of a local 'respected' porsche racing guy, and the diameters of the runners are way too big. The injectors will not be in the ports of the smaller engines. I have T heads on my engine, and I had to slightly relieve the edges of the ports when I moved the injectors down, but the 3.2 would be too far out. Some of the newer smaller injectors will make this easier to do, but the design of the port injector mount was a bit of a challenge.

Posted by: 914efi Dec 20 2004, 12:45 PM

another view


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Posted by: Bleyseng Dec 20 2004, 03:30 PM

Take a look Mueller.


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Posted by: jwalters Dec 20 2004, 03:54 PM

QUOTE (914efi @ Dec 20 2004, 10:45 AM)

another view

wow, thats not bad!!!

Posted by: TimT Dec 20 2004, 04:19 PM

Mike here is the GT3RS plenum, I couldnt find where we put the throttle bodies


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Posted by: TimT Dec 20 2004, 04:20 PM

nuther


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Posted by: TimT Dec 20 2004, 04:22 PM

YOu bolt the different restrictors to that round flange. The small restrictors knock almost 50hp off


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Posted by: Mueller Dec 20 2004, 04:48 PM

thanks Tim,

that is a huge plenum...and dusty too

Posted by: TimT Dec 20 2004, 08:35 PM

QUOTE

and dusty too

grrrrrrrrr We had the dyno installed when we were down in Savannah. The concrete guy promised he would cut the floor with a wet saw. Instead he used a dry saw and cover the whole shop with a finelayer of dust lets just say final payment hasnt been made for the concrete work.

Posted by: Mueller Dec 20 2004, 10:08 PM

concrete dust?? that is even worse.......

can you tell me if there are any baffles or ducting inside the plenum, if not, it's okay, you've done enough with just the picture

Posted by: Bleyseng Dec 20 2004, 11:33 PM

Check out how short those runners are! Nice carbonfiber....so can you make me one for a 4 banger??

Geoff

Posted by: Mueller Dec 21 2004, 12:05 AM

QUOTE (Bleyseng @ Dec 20 2004, 10:33 PM)

Check out how short those runners are! Nice carbonfiber....so can you make me one for a 4 banger?? Geoff

it took me 1.5 hours to get home tonight due to traffic and fog...during that time I talked to Sir Andy for about 20 minutes about manifold/plenum design and the rest of the time I spent thinking how the heck can I make something just like the Porsche Motorsport plenum for my /4

it looks to be all one piece, how do they make a hollow c/f or 'glass part like that??

could you make one from wax, cover it with the carbon fiber and once cured, melt the wax out of it??

with the intake like the GT3RS, one could easily take the plenum off to test it with the throttle bodies exposed directly (add air horns) and you could also keep the plenum on the throttle bodies but remove the butterflies and install 1 single throttle body on the opening of the plenum...3 different methods of induction with one basic design

Posted by: 914Timo Dec 21 2004, 01:35 AM

QUOTE

how do they make a hollow c/f or 'glass part like that??

Multi-element mold.

QUOTE

could you make one from wax, cover it with the carbon fiber and once cured, melt the wax out of it??

Wax or styrox (Do you know what styrox is ?? I am not sure if styrox is correct term. The white bubble stuff, you know.)

I have thought the same. Only problem is, that the outside will not be smooth and may look ugly depending how good you are laminating. However, the inside would be very smooth.

One possibility might be put the plenium together from many separate pieces. Then you could use one mold and make all six (or four) air horns from the same mold.

914efi, I see your problems with the 3,2L intake now. Just one question, why you have put the TB in such a tight place ?? Why didnt you put it in top of the plenium. It could be in the cover of that accesshole, or could it ??

Posted by: McMark Dec 21 2004, 02:44 AM

That air box looks like it barely fits in there. 1" - 1.5" clearance probably, judging from the shadow cast by the rear deck lid.

Posted by: 914efi Dec 21 2004, 07:11 AM

I had various ideas on where to put the TB, but when you factor in weather protection, cable position, plenum simplicity, air filtering, etc, it made sense to put it on the side. I was also trying to maximize length of the runners. If I made the whole thing shorter I could have more easily put it on top, but it would have shorter runners and a smaller plenum. I have the runners at a length that allows them to resonate at the torque peak of the engine.

My goal was to build a good street system. Most people are doing this for racing which is a different set of priorities. I also did not want to cut anything on an original six to make stuff fit. So far all of my mods to the car are reversible and I have all of the original parts. The cage ideas might not be so easy to do with low impact!

Posted by: 914Timo Dec 21 2004, 08:27 AM

Very interesting, 914efi. Obviously you have done lot of work and research.

You wrote earlier that you have a CAD file from your intake and you could you send it. I would like to have it. Could you send it to me ?? I use AutoCAD and MicroStation. Do you know if I get it open with these programs ? I will PM my e-mail to you.

Posted by: Bleyseng Dec 21 2004, 09:12 AM

Mueller, I too after seeing that CF manifold thought of ways to make one. I thought the best way was to make a mold so it you could make a run of them or just make one out of wax.
Geoff

Posted by: Jake Raby Dec 21 2004, 09:37 AM

My Carbon Fiber tech has been on the plenum for quite some time now.. To do a part like that in Carbon it needs to be "Vacuum bagged" to pull the resin through the part and make it very strong as well as cosmetically enhandced.

It just takes alot of time and money to make the mold.. I have spent 2K on it so far and I have not even seen it yet... It took him over a year to do the carbon Fiber DTM mold.

Posted by: Bleyseng Dec 21 2004, 09:54 AM

Ah, but the question here is- Is the carbonfiber manifold for a upright type4 or for a 914?

Geoff

Posted by: kwales Dec 21 2004, 02:21 PM

Ya know you can tune your intake runner length in two ways....

One is to cut it to length. As the pulse is reflected up the intake runner, it hits the cut end and reverses direction...

Now iffin you were, clever you could reverse the pulse where ever you wanted (in a system) by adding an anti-reversionary feature (cone) in the manifold- say below the MAF or MAP sensor. That sucka would act as a one-way valve and allow air to be sucked in and would reverse the pulse once it hit the AR feature...(See Feuling patents on AR exhaust)

Now iffin you were brilliant, mebbe by taking a thin wall tube and placing it into the manifold near the ideal tuning point with the AR feaure on the trailing end would allow you to move the AR feature to locate the tuning point.....

Since that tunes it for one RPM, moving it back and forth with a mechanism would tune your intake over the RPM range........

Kenny needs math! Quit hoardin it Ahndie........

Ken

Posted by: TimT Dec 21 2004, 02:40 PM

QUOTE

moving it back and forth with a mechanism would tune your intake over the RPM range.

kinda like varioram on the 3.8's?

Mike, there are no baffles or runners GT3RS plenum. However, the small restrictor has a cone that goes into the plenum.. I dont have a small restrictor so no pics

Posted by: Qarl Dec 21 2004, 03:37 PM

I don't think the carbon fiber plenum needs to be strong at all. Only strength is for the connection points for the throttle body or afm.

Posted by: Mueller Jan 14 2005, 10:54 AM

QUOTE (Qarl @ Dec 21 2004, 02:37 PM)

I don't think the carbon fiber plenum needs to be strong at all. Only strength is for the connection points for the throttle body or afm.

I was thinking about that statement (for a few weeks it appears, LOL)
and I got to wondering about what happens if you have backfire and what are the chances of spliting the plenum wide open???

I know for some of the 911's they had a pop-off valve that could be added to help prevent damage in case of backfire, maybe it would be a good idea to add one to a newly design plenum if going with a composite material ???

Posted by: Britain Smith Jan 14 2005, 11:39 AM

The backfire issue was the reason that Brad and I decide against an aluminum intake plenum on my turbo motor and had it made in steel.

-Britain

Posted by: Mark Henry Jan 14 2005, 01:31 PM

I can't believe I didn't see this thread before...

Anyways...I'm also debating a IR or plenum system for my 2.7/4.

A Honda Accord 2.0 FI TB....at 64mm it's huge compared to a 914 TB. Not too much crap on it, has an idle bleed screw, but it does rotate opposite from a 914 TB, so I'd have to get a new TPS.




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Posted by: Mark Henry Jan 14 2005, 01:36 PM

If I was going to do an upright, like a DTM, I would consider something of this flavor...


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Posted by: Mueller Jan 14 2005, 01:43 PM

QUOTE

A Honda Accord 2.0 FI TB....at 64mm it's huge compared to a 914 TB. Not too much crap on it, has an idle bleed screw, but it does rotate opposite from a 914 TB so I'd have to get a new TPS.

it's interesting how large some TB for the size of the motor they come off of....I have a Mustang 5.0 TB that looks to be about 2/3 of the size of the TB that belongs on my 2.8 VR6 engine

i bought an oxy-acetelene welding setup last night, so I'll be welding/burning up a new plenum for the car pretty soon

Posted by: Mueller Jan 20 2005, 04:21 PM

more plenum ramblings.....

okay....let's say we take a stock 2.0 plenum, cut it in half and widen it to do 2 things...1st would be to increase the volume for a larger motor and the 2nd thing it would accomplish is allowing one to cut down the overall length of the intake runners.

Instead of the stock t/b, pretty much any t/b could be mounted on top or how about 2 throttle bodies of smaller size???

hmmmm???

Posted by: lapuwali Jan 20 2005, 04:41 PM

QUOTE (Mueller @ Jan 20 2005, 02:21 PM)

more plenum ramblings..... okay....let's say we take a stock 2.0 plenum, cut it in half and widen it to do 2 things...1st would be to increase the volume for a larger motor and the 2nd thing it would accomplish is allowing one to cut down the overall length of the intake runners. Instead of the stock t/b, pretty much any t/b could be mounted on top or how about 2 throttle bodies of smaller size??? hmmmm???

Now you've killed one advantage of a single TB: no throttle synchronization required. The only advantage I can see to a smaller TB on a large plenum is less throttle sensitivity at small throttle openings. Intake velocity across the TB seems to be completely unimportant unless there's a lot of other resonance tuning going on, but this is all black magic to me. Velocity in the runners I see as being much more important. Shortening them is going to raise the power curve higher in the rev band (according to the usual theories, anyway), and you're building a big, torquey engine. So, it seems that's to cross-purposes to me.

64mm is bloody huge. Compare this to the 2x28mm restrictors required on all DTM cars. That's a total area of 200 sq.mm for the Honda v. 176 sq.mm for the 475hp V8s used in the DTM. The Accord certainly doesn't need that big a TB for flow, so they must be using it for some other reason.

Posted by: Bleyseng Jan 20 2005, 04:49 PM

Think progressive TB Mike. Lots of them out there to pull off junkyard cars. Small opening for low rev throttle response and the big secondary for WOT. Woohoo!
The more I read and check stuff out, I think DaveHunt is gonna have to go to this to be able to tune that sucker.

Geoff

Posted by: Mark Henry Jan 20 2005, 05:23 PM

James on a T4 with the DTM, that woud be 4 X 28mm on dual/dual Webers.
On Jakes/Kit Carson's test engine the were running Jenvey TB's and I forget the size off hand, but it was 4 X 45mm - 48mm or something like that.

64mm is big for a single TB but I'm going to have a 2.7 type 4

Posted by: dinomium Jan 20 2005, 06:14 PM

I got this from the 2004 GT3 cup car manual... pretty kewl stuff INDEED!


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Posted by: lapuwali Jan 20 2005, 06:28 PM

Somewhat apples and oranges, though. With individual throttles, you need to look at peak flow for each cylinder with that relatively tiny manifold volume providing no real "buffer", so each throttle has to flow enough for that cylinder at peak. While that one cylinder is sucking as hard as it can, the other three are basically idle. With one TB feeding a sufficiently large plenum (at least the combined size of the number of cylinders drawing air at once, or 500cc for a 2.0 four), then the air for one charge is being drawn from the plenum, and the TB only has to flow enough to keep one cylinder full (on a four, 1.5 on a 6, 2 on an 8).

...I'm hand-waving here, not operating off actual theory, but this sounds close to correct. I have NO data, this is me just thinking out loud. I'm sure Jake will pound me into the ground with actual data...

So, if a 28mm venturi works with a pair of dual Webers on the target engine, then a single 28mm TB with a plenum one cylinder in size should also work. Probably upping the size of the plenum and the TB some to account for inertia effects and cam overlap is a good idea, hence the 45mm TB on the 2.0 (which is probably bigger than actually required for flow). Note that many a 2056 is out there making more power than a stock 2.0, and each cylinder is being fed by a 32mm venturi or thereabouts. A 150hp 2270 is using, what, 36mm vents on 44IDFs?

Posted by: Bleyseng Jan 20 2005, 07:35 PM

Well, you are mixing apples and oranges since carb vents and TB's have little in common. The venturi is where the fuel is mixed and you must achieve proper atomization. The TB is a air metering device sized by the air charge needs.
Dual TB's suffer from poor driveablity and tuning but a great for drag racing where they are tuned for one basic rpm (WOT).

The plenum and runners FI is a different concept than dual carbs. Since the intake air doesnt have to hold fuel in it and the fuel is delivered smack on the valve, its more tuneable. The runners are sized to hold atleast one chambers volume for an intake stroke. The plenum holds the recharge air plus additional as there is overlap from other cylinders. How the engineers calculate this with math is beyond me. I am hoping out resident math wiz has figured it out!

Geoff

Posted by: lapuwali Jan 20 2005, 08:21 PM

QUOTE (Bleyseng @ Jan 20 2005, 05:35 PM)

Well, you are mixing apples and oranges since carb vents and TB's have little in common. The venturi is where the fuel is mixed and you must achieve proper atomization. The TB is a air metering device sized by the air charge needs. Dual TB's suffer from poor driveablity and tuning but a great for drag racing where they are tuned for one basic rpm (WOT). The plenum and runners FI is a different concept than dual carbs. Since the intake air doesnt have to hold fuel in it and the fuel is delivered smack on the valve, its more tuneable. The runners are sized to hold atleast one chambers volume for an intake stroke. The plenum holds the recharge air plus additional as there is overlap from other cylinders. How the engineers calculate this with math is beyond me. I am hoping out resident math wiz has figured it out! Geoff

The sizing of carbs has the additon of fuel metering, true, but pure airflow is all I'm discussing here.

The venturi is going to limit the amount of airflow into the engine, regardless of whether there's fuel getting sucked through a jet or pumped through an injector. The max. power of the engine is basically limited by how much air it can ingest. If an engine can make 150hp with 36mm carb venturis (one per cylinder), then it's also going to be able to make 150hp with a sufficiently large plenum fed by a 36mm TB, since the TB will flow as much air as the venturi in the each carb.

The exact reasons why a 36mm venturi would be chosen in a carb are clear, given the need for good intake velocity past the jets. Why TB sizes are chosen as they are is, frankly, still a mystery to me. They all seem to be too big, even the 45mm unit on the stock 2.0.

Posted by: Jake Raby Jan 20 2005, 08:25 PM

Its all in the combo!

Posted by: lapuwali Jan 20 2005, 09:21 PM

QUOTE (Jake Raby @ Jan 20 2005, 06:25 PM)

Its all in the combo!

Y'know, that's probably the politest correction Jake's ever given.

Posted by: Bleyseng Jan 20 2005, 09:38 PM

QUOTE (lapuwali @ Jan 20 2005, 06:21 PM)

The sizing of carbs has the additon of fuel metering, true, but pure airflow is all I'm discussing here. The venturi is going to limit the amount of airflow into the engine, regardless of whether there's fuel getting sucked through a jet or pumped through an injector. The max. power of the engine is basically limited by how much air it can ingest. If an engine can make 150hp with 36mm carb venturis (one per cylinder), then it's also going to be able to make 150hp with a sufficiently large plenum fed by a 36mm TB, since the TB will flow as much air as the venturi in the each carb. The exact reasons why a 36mm venturi would be chosen in a carb are clear, given the need for good intake velocity past the jets. Why TB sizes are chosen as they are is, frankly, still a mystery to me. They all seem to be too big, even the 45mm unit on the stock 2.0.

The runner and plenum store the intake air charge until the valve opens then its sucked in.The valve closes and the moving air is bounced back up the runner (reversion). The air is bouncing around the plenum, helping to fill up the runners, with the valves closed. The reversion helps fill the runners too ready for the next time the open.
The plenum and runners are part of the whole system as it the cam and cam timing, as Jake is saying "Its all in the combo".
In dual carbs the air bounces back up the throat disturbing the incoming air/fuel charge Velocity. But there is no plenum to buffer the reversion or use to help fill the other runners.
The TB is sized accordingly to control the fill rate of the plenum volume not the runners. Thats the difference between the two systems. Of course too large of a TB can cause problems with tuning.

Geoff (I am not the greatest at explaining this stuff, hell I am General Contractor not a Automotive Engineer)

Posted by: Jake Raby Jan 20 2005, 09:52 PM

After the day I have had today I decided to try and be a little Mellow.....

Having a drivesft disintegrate in front of my eyes and blow out light bulbs, and send parts through the wall of the dyno room started things off really bad....

Some days i really don't want to be here- today was one of them..

Posted by: Bleyseng Jan 20 2005, 10:39 PM

Well, its days like today that you climb in the 914 and drive somewhere. It will put a smile back on your face!

Geoff

Posted by: Jake Raby Jan 20 2005, 11:59 PM

I can't...

I have no time to bolt the engine back together and back into it!

Posted by: Brett W Jan 21 2005, 12:20 AM

QUOTE

I don't think the carbon fiber plenum needs to be strong at all. Only strength is for the connection points for the throttle body or afm.

The plenum must be very strong. When you slam the throttle plates shut at 8000+ rpm with a big 3.8 litre motor you will pull a massive vaccum and implode the plenum. Been there done that. Make it strong. It also must be able to withstand a backfire as well otherwise it will explode.