Please show me your custom intake manifold!
 

Hello all,

I would like to replace the CIS on my 79 SC. Replacing it with ITB is well documented. What I would like to know is the pro vs. cons of ITB vs. a custom intake manifold.

What should I take into consideration? Recommended lengths, shapes, size of injectors etc. etc.

I will be running standalone management and ignition coils.

If you have pictures and specs it will be greatly appreciated!

Many thanks in advance,

F.

P.S. Engine internals are stock and I would like to keep it that way.

Stock Porsche manifolds are very hard (if not close to impossible) to beat. If you want something better than an SC manifold, get a Carrera 3.2 manifold. If you want something better than the Carrera manifold get the 964 manifold. Etc.

Unfortunately they are not that easy to locate around here :-( That is why Im looking for alternatives...

Has anyone attemted this?

Francois,
Shipping isn't as bad as you think. I believe there is one or two for sale on eBay so you may want to ask about shipping to France. There is usually at least one available and sometimes some Carrera fuel injectors as well.

I shipped a 914-6 oil tank to France for about $30.00, with the US Postal Service, 5-8 day service. The box was approximately 18X18X6 inches, and weighed 10 lbs. In metric, I'd guess 50cmX50cmX13cm, and 4.5 kilos.
I have no idea how many Euros.

Shipping to South Africa will be atleast $100.

Also, I dont like all the plastic, cables etc. on the Porsche manifolds. I love the look of the ITB, nice and clean... That is another reason Im thinking to build the custom intakes, to clean up the engine bay...

How about a Carrera 3.2 aluminum intake. You could polish it.

I talked to a guy that did a lot of work and spent a lot of money trying to better the Carrera intake and he couldn't. If you're going for looks that fine, but I wouldn't expect to gain power from a custom intake.

I found this in another thread, I think it was from a 3.8 RSR. Im considering building something similar. It should provide a really wide flat torque curve seeing its a fairly long path for the air to travel.

One question I have around this intake is how does the air get to the connecting pipe closest to us, the one connecting the two halves so to speak?!?!?!

Do you think it could work? I like experimenting :D http://forums.pelicanparts.com/uploa...1168189106.jpg

Hi there,

If you are going to make up your own intake, why not consider going the ITB route. The consensus thus far in this thread is that you would not be able to improve on the 3.2 Porsche manifold.

The ITB option is costly, especially for those of us in RSA, but there are other options.

You will need a lot of design time to get the benefit of the pulsing in the plenum. This is much easier with the ITB option. You only need to worry about the pulses in the individual intakes.

Here is a pic of the setup that I have been using in some or other form for the last two years. All parts are available locally, and it has been fun.

http://forums.pelicanparts.com/uploa...1168190214.jpg

I am busy making up a new setup for my car, which will be ready by about March. This will operate with the new ECU.

I hope this helps.

WOW, that looks really nice! :-)

Please can you elaborate on your spec, cost involved as well as who did the work...

Also, how is your 911 used? Road/Track etc.

Many thanks!

Hi Francois,
The car has evolved from a standard 911 SC to a 3.2, 300 HP monster. I currently race in the Porsche Challenge series.

The car is very streetable, with the exception of no fast idle on cold start. When starting in cold weather, it will idle at about 500 rpm for a few minutes, and then it's fine.

I did all the work myself. I used the base of the SC manifolds and merged them to the existing manifold, the the throttle bodies cam with. The throttle bodies cam off a Toyota RSI.

The throttles are 45 mm diameter.

The trumpets and the air filters with the Madonna style injection was also manufactured.

In the chase for more HP, I will be improving on this design, which will also make a sleek, minimalist look in the engine bay. The new intake and ECU will be set up on the current motor, and once everything is working will install the 3.5l motor that is yet to be built.

I hope this gives you inspiration.

Definitly ;)

Im not as brave as you though, Im keeping the internals stock for now...however long "now" turns out to be, I dont know yet :D

A friend of mine suggested using M3 throttle bodies and injectors coupled with VR6 ignition coils, what do you think?

Apart for the RSi ITB, what other cars ITBs could be used?

Would it be possible for us to get together sometime, I can really do with the advice...

This is the high butterfly setup our shop is currently using for individual throttle bodies. The black intake stacks and adapters and linkage is of our own design.

We also use the factory 3.6 plastic intake with good results with EFI.

Rothsport Racing
Tualatin, Oregon

http://forums.pelicanparts.com/uploa...1168194910.jpg

Any idea of what hp/torque figures Im looking at with ITBs and standalone management on a engine with stock internals? Im trying to decide if it will be worth the expense and time...

Also, will I have enough flexibilty in the system if I decide to start working the internals? Too what extent will this be possible?

The individual throttle bodies are better suited for race applications than for street driven cars.

See the dyno sheet below for a stock internal 3.0 Euro engine with single throttle body, DTA EFI, and 3.6 plastic intake. It also has 1.5 inch headers with performance muffler.

http://forums.pelicanparts.com/uploa...1168196416.jpg

Thanks for the info RSScotty :-)

The vehicle would be for spirited road use and the occasional trackday. If possible I would like some flexibility to develop the internals further before having to do major upgrade to the EFI should I wish to develop it more for the track at a later stage.

Considering the dyno chart you just posted, would I be better of with something like the RSR intake manifold I posted earlier based on my needs above?

We have found that the RSR intake you posted a picture of is not suited for a 3.0 liter engine. It works best on big blocks (3.8) with large airflow capabilities.
The biggest bang for the buck is still with the 3.6 intake for a street and sometimes track car. With the resonance flap, it fills in the torque better in the 3800-5000 rpm range compared to an engine with individual throttle bodies.

If you are concerned with the appearance of the 3.6 intake, you can always paint it to a color of your choice...and remember it does not use the factory air flow meter when you go to EFI....you adapt a air filter like a K&N right off the OEM throttle body.

The other option is to use 6 indivdual throttle bodies ( these install in between the cyl. heads and the 3.6 intake) instead of the factory single tb. We still use the factory throttle body, we just delete the throttle plate. This makes for instant throttle response and gets along better with race type camshafts so you can make the engine idle.

Here is the standard Jenvey set up, with their manifolds. Same throttles as RSScotty's shop uses but they have their own taller manifolds and much better linkage. With the standard Jenvey stuff you need to adapt their cable to the bellcrank on the transmission (not too big of a deal).



http://forums.pelicanparts.com/uploa...1168217578.jpg

http://forums.pelicanparts.com/uploa...1168217594.jpg

This is in my 914-6.

http://forums.pelicanparts.com/uploa...1168282557.jpg

I have a full solids cad file on it if you want it.

I don't doubt that Porsche built a "good" intake. Fact, I'm probably going to use the 3.2 intake on my turbo for ease. BUT, Porsche kept improving and developing their intakes so even they weren't completely happy. They, though one of the best engineering firms, are under different restraints than an individual. There is going to be a trade off running an intake ideal for a 3.6 on a 3.2 though maybe a miniscule issue and to the performance stance possibly mute.

I'd use Porsche's research for runner length and plenum size. I'd also do a lot of research to determine best taper angles and modify length depending on the rpm YOU plan to use. You could improve on flow at the intersection of the runners to plenum. Many have argued that the stock TB and opening are restrictive.

Saying the above, I'm going with Jenveys for my NA since I still like the response of my MFI and ITB's. Fun over pure numbers for the street because if I just wanted fast I'd buy an EVO for the street.

Thanks for the info (and support) Luke :)

Please please can anyone provide me with detailed photographs and measurements for a 964 plastic intake?

I can then use this as the basis to start developing my custom intake, making improvements where it is believed to be restrictive.

Many thanks in advance fellow Pelicanites :D

Who was it that not too long ago was building up a pretty slick intake in carbon with itb's and machined goodies all over? From what I remember he gave up because producing them would become cost prohibitive.

If this is for yourself then go all the way by all means! In that case it might be in your best interest to "borrow" all the different intakes you would like to build off of, i.e. 964, 993, 993 vario, rs, and all the others. Then you have to take into account what the engine will be asked to do, rev to hell and back, produce smooth power, peak power, streetable all that nonsense. The engineering can become overwhelming but if its just for street and kicks at the track a somewhat off the shelf unit like the Jenvey's becomes very attractive.

Before I even started the motor for my dad's car I gave up on the barrel throttle system I was working on and went with the Jenvey setup. The picture in the first page of this post with the black "runners" or manifold and black trumpets with Jenvey's sandwiched in between I believe was a Steve Weiner idea that I saw a few years ago at the GAF in Ventura. Instead of using the Jenvey crossbar linkage a Porsche Motorsport linkage is used to simplify things. I have seen them on many 993 race setups and it is not simply a one off as others would have you believe unless the dimensions were changed for some reason.

edit: to rsscotty, I call bs on saying that was your own design unless you are in cahoots with Steve Weiner. I saw that exact setup years ago at the GAF. Also the cross linkage system is either the Porsche racing bit or an adaption. While it is rather slick its not like you guys came up with it on your own.

Secondly I dont think that being in SA is a hindrance in terms of obtaining bits and pieces. Plenums on each bank lend themselves nicely to turbo power and somewhat better torque. A modern GT3 RSR runs an almost identical plenum to a Daytona Prototype the difference being the RSR runs two 29.2mm restrictors whereas the DP has an "open" intake although they merely chopped a hole in the top and placed a BMC air filter in there and blocked off the holes where the restrictors would normally mount. This isnt secret info, you can see it in pictures.

Depending on cashflow, troubleshooting, time, perfomance, and any other variable you can imagine there are still many decent options. If I had unrestricted access to a CNC machine then my dad's motor would have some step off intakes cum throttle bodies. Since I dont I went with I thought was the next best thing, Jenveys. The quality, adjustability and performance of these is pretty darn good. You can tailor them by running different size trumpets, different length manifolds, if any at all.

There is a huge amount of chocies of "off the shelf" parts available to you.

Jenvey straight shot or tapered, TWM weber style manifolds or straight shot, 964 plastic, 993, 993 vario, 993 rs, cup, rsr, 9m (nine meister), 3.2 intakes, slide valves, bla bla bla. The only setup I have never seen on a porsche and I wanted to be the first in my mind to do it was barrel throttles. With plenums you can go single throttle, twin throttle, 6 throttles its up to you. For fun I would like to try a 964 plastic manifold with twin throttle bodies. Mount the manifolds on the opposite head as normal pointing outwards yellowbird style and put throttle bodies on the ends. Might be fun.

Whatever you end up doing I am sure you will enjoy. Best of luck

Thanks for all the info Porschekid962 - I will look into what off the shelf parts are readily available locally...

Please can you elaborate on this and maybe post some pics, Im not familiar with it...what would be the benefit over say ITBs?

"The only setup I have never seen on a porsche and I wanted to be the first in my mind to do it was barrel throttles. With plenums you can go single throttle, twin throttle, 6 throttles its up to you. For fun I would like to try a 964 plastic manifold with twin throttle bodies. Mount the manifolds on the opposite head as normal pointing outwards yellowbird style and put throttle bodies on the ends. Might be fun."

Only FYI and a laugh ;). Taken off a running 73 T , CIS. had 2 barrel Holly. http://i138.photobucket.com/albums/q...p/DSCN0789.jpg

barrel throttles
 

Barrel throttles are commonplace in high end motorsport divisions. AER engines use them, F1 motors go back and forth between butterflies and barrel's, JUDD, Cosworth, Illmor have used them on race motors to name a few. Pretty much everyone is familiar with the butterfly throttle so I wont get into that. Then there was the slide valve throttle setup. Great at WOT but not the greatest part throttle response and then there is the problem of airborne particulates getting into the mechanism and gumming it all up. Have not seen a modern race engine using slide valves, barrel's yes. The great thing about the barrel style throttle bodies is their relative simplicity and low number of moving parts. I am going to grossly simplify things here but you basically have a rod/cylinder/pipe what have you inside of a barrel. This pipe or rod has cutouts where the intake ports are and as you rotate the rod through 90 degrees you open and close the throttle.

http://e30m3performance.com/tech_articles/engine-tech/dtm_slides/index.htm

this is a nice write up on slide valve throttles. Notice when the slide plate is at WOT there is a gap through which contaminants can ingress to the inner workings of the piece.

http://www.aerltd.com/products.html

Page from the AER site, its not the greatest pic but if you look at the intake runners its rather hard to tell where the throttles are. That is because barrel throttle mount is cast as part of the head, rather slick and saves a bit of weight. You can just see the upper half of the barrel bore on the left bank of the engine at the base of the intake runner.

http://www.lumenition.com/roller.pdf

still not a schematic drawing but you can begin to see how these throttles go together. I am not on my home computer so I forget exactly where I found it but there is a decent drawing and pictures of the inner workings of a barrel throttle somewhere.

There are debates in motorsport as to which throttle setup is better. No restriction at WOT is great for F1 but even they want some turbulence to aid in fuel air mixture at part throttle and lower rpm's. The butterflies will give you a sharper throttle response though and have been tried over many years. Afaik there is no aftermarket barrel throttle setup available for a Porsche application. One problem that comes to mind on an air cooled motor is the bending and twisting of a barrel throttle bore mounted atop 3 individual heads as things heat up, cool down, rev up and down. This might add undue stress to something that needs to remain very precise.

The potential gain in performance would most likely be negligable over a properly setup butterfly ITB system. The coolness factor would be out of this world though. The main reason I gave up on this was of Jenvey and money. Every time you build a motor you have to compromise here and there. The trick is to minimize these compromises without breaking the bank which is a worry to almost all here. When I can raise enough funds I will build the motor I have been designing for years. Flat 6 will be about as close to factory as it gets with the exception of reusing some internal parts namely the crank.

In order to minimize hassle I say go with the Jenvey stuff. I do not work for them I just see that their stuff is better than TWM. You can get fancy with the steve weiner long runners, not too dificult for a competent machinist to make for you, order some trumpets, get a 993 rsr throttle linkage and your off and running.

have fun

If your plumbing your own runners (tubes) into a fabricated plenum, you might consider 180 degree rolled lip trumpets extending into the plenum. There have been studies showing an increase in flow by installing these small trumpets inside a plenum as if exposed to the atmosphere.

Mark Hargett might be the designer of the intake your speaking of above. He had a great design and had it in plastic rough prototype form. He seemed questionable in his commitment to finish any time soon. Do a search for this.....it might have reference to a itb turbo intake or such. He is quite heavy into forced induction, but quite the craftsman. Good for ideas, if nothing else.

http://www.itsfun.nu/if2_2006/2402/if2_007.JPG
http://www.itsfun.nu/if2_2006/2402/if2_005.JPG
http://www.itsfun.nu/if3/if3_210.jpg

Great looking setup Goran - please post some more pictures if possible...

Off topic question - I see you dont have the standard plastic shroud that covers the alternator and top of engine, doesnt it affect the cooling of the engine?

F.

It's not mine. It belongs to IF2 car and is custom made by company called ML Wankeltrim by a guy who's guru on Wankel engines and induction in general. I'm posting pictures so you can get an idea how optimal turbo intake might look like.

Plastic shroud (well not quite plastic, it's carbon fiber) is there, but was removed during assembly.

Here are few more pictures so you understand how it fits together:
http://www.itsfun.nu/if2_2006/0403/if2_011.jpg

http://www.itsfun.nu/if2_2006/0403/if2_051.jpg

http://www.itsfun.nu/if3/if3_028.jpg

Yeah, like Goran shows on the "trumpets" on the runner design. That is exactly what I was explaining if using tubes and fab'd plenums. A tapered runner can often improve yet again, though this is getting tricky and expensive. Our "sheetmetal" intakes in drag racing are going to run just short of 2 grand and thats for a "V" configuration with straightish runners.

I'm actually surprised that Porsche didn't seem to take advantage of this in their cast runners. Get volume in and then build velocity like an ITB does or old MFI for that matter. Love all the taper in the desing that Goran presents.

They actually did, but only on race models. If you cut 956 or 935 plenum you will find tapered cones for each cylinder.

I guess it was too expensive to include this on ordinary cast plenums.