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

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.

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

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.

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

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

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

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?

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

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.

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.

Nice job, 914efi

Send more pics.

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

Why didnt you 3,2L intake ??

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.

another view

Take a look Mueller.

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

another view

wow, thats not bad!!!

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

nuther

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

thanks Tim,

that is a huge plenum...and dusty too

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.

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

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

Geoff

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

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 ??

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.

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!

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.

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

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.

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

Geoff

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

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

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.

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 ???

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

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.

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

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

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???

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.

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

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

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

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?

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

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.

Its all in the combo!

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.

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)