individual throttle bodies
 

Friday ramblings ...

if you look at a 996 intake manifold you'll notice that, unlike the 986, each side is TWO parts (#1 and #24):

3.4l / 3.6l Intake Distributor

note part #24:

PORSCHE 911 CARRERA TYPE 996 1998 - 2004 ANSAUGSTUTZEN 99611010152 | eBay

a nice straight piece that houses the injectors at one end.

while not round, I wonder if it would be possible to mount individual throttle plates in these things - shine up the inside, drill it through longitudinally, mount three little plates, add all the mechanical bits and bobs, tps, etc.; similar to this:

Anyone running ITBs on a NA 996? - Page 2 - Rennlist Discussion Forums

(thanks jake)

plop the rest of the manifold on and reinstall oem vacuum lines, maf, etc.; all the intake bits less the tb. would have to figure out the cable/e-throttle conversion, but otherwise the ecu should cooperate as you are still metering the air. probably need a wideband O2 and piggyback to finetune fueling when open loop, however.

benefits? better throttle response. more hp? dunno. cool factor - totally.

that would look so cool
Glass engine cover would have to be a must tho

individual throttle bodies
 

So are you trying to suggest 6 individual throttle bodies?

I asked about the obx tb kit a few months back. There were a couple if replies there but nobody who was running such a car.

The challenge is MAF sampling with IR arrangements. The second challenge is linkage, especially for cars that were originally E gas.

I have an arrangement but it has yet to have the development completed.. Just haven't had time. Had bigger fish to fry, trying to make the engines not failure prone.

yeah, when you think itbs the mind immediately goes to hella-cool venturi trumpets poking out of the engine bay. tough to do on a boxster, however. i was thinking of an approach like a 911 rsr:

http://forums.pelicanparts.com/uploads8/RSRTB1154376577.jpg

where the itbs sit between the intake manifold and head. this way you can still keep your maf and the ecu should work as before.

and there is the issue of throttle control. one option would be to use a flash for a cable throttle car and retrofit a cable system (ie, early 3.4 996 flash should work for 3.2 boxster with 987 maf housing; dunno what for larger 996 engines).

or you could somehow repurpose the tb electric motor to turn the throttle linkage. ive seen pics of the inside of a tb and it is just a gear on the end of the motor shaft turning a gear on the end of the throttle plate shaft. swap the throttle plate gear over to your new assembly and fab a bracket to hold the motor in place. put a motor on each bank and no need for linkages between the two. you would need to find a tps sender with the same output as oem, which i dont think is an issue.

this would be easiest if you use one long throttle plate shaft to operate all three butterflies (as per jakes); no linkages, and easily operated by a converted tb motor. my concern would be that, if we are reurposing the original, oblong manifold part as originally posited, then the butterflies would be installed along the long axis and max obstruction when fully open; put them in along the short axis and they wouldnt be as in the way when fully open. this makes the linkages a lot more complicated, however.

You could certainly put a servo on the linkage
But the maf would be tricky.

Might just have to mock up something inferring maf values based on throttle/linkage movement.

Essentially that's how my RSR does it with the Motec Setup
But I'm sure actually measuring would be better

I'm sure a maf could be sandwiched between the trumpet and the intake

Mike

inferring airflow from throttle position (taken from the tps - throttle position sensor) is how alpha-n tuning works. possible with most aftermarket ecus and what the oem ecu does when the maf stops working. very effective at partial throttle where the narrow band o2 sensors can trim the car back to stiochiometric during closed loop operation. can get out of whack at wot /open loop, but this is where you get a wideband o2 sensor, an afr meter and a piggyback to fine tune your afr and keep things closed loop.

there is a tuner in britain that can tune your ecu to run in this manner. the purpose of this thread, however, was to consider using itbs with the stock manifold - the oem intake runners are, for all intents and purposes, venturi trumpets thatfeed each cylinder which draw from a larger plenum. this plenum has a single air source which is already metered by the maf.

Just rig up a slide valve with linkage attached to top of gas pedal. Press the gas pedal & slide valve opens. Make sure you use quality throttle return springs! :cool:

If a MAF sensor could be installed into one velocity stack, could the flow sample of that one MAF be mapped into the ECU to represent the flow of all 6 TBs. Or could the signal from that MAF be amplified X 6 ( using X 6 just for discussion sake, even though it may not be that simple).

Cool factor would be great but actual performance would be none at least in the day to day aspect, I don't think there is enough plenum volume to have any type of torque for low rpm.

right?

yeah, initially I would think that using the oem plenum would be a bit of a buzzkill for performance improvements. I would anticipate an increase in throttle response, but no flow improvements at any rpm for 996 applications (of course, you could use an x51 intake, but big $).

on a boxster, however, you would be using a 996 manifold designed for a 3.4 on the smaller 3.2 engine, so some benefit there (regardless of itbs or no). further, the 996 manifold is taller, so longer venturis, so assume better low rpm performance, along with throttle response.

the other concern is the obstruction to airflow multiple butterflies would introduce into the system vs the one large butterfly we currently have, unless we went with aftermarket itbs vs repurposing the intermediate manifold piece.

yet another concern is where would we get vacuum for the aos, fpr and brake booster? the only thing I can come up with is a bracket where my ac pump used to be, for mounting a mechanical vacuum pump and running an aftermarket aos. this starts to become a lot of work. with a mechanical vacuum pump you now have the opportunity to add oil pumps, however ...

the more I think about it, the more i am drawn towards keeping the one tb, but still going with an alpha-n scheme (and piggyback for fine tuning). this lets me get the maf out of the airflow; improves airflow, removes a failure-prone, expensive component from the system, and adds tuneability.

further research shows that softronic, protomotive an evoms all do alpha-n tunes, albeit for the 996 turbo.

Packaging is the challenge with any arrangement like this. The MAF is just one challenge.. We have a syncline system thats used on our aircooled engines that is easily applicable to this application, and we already have the throttle bodies and flanges made up.

Its far from simple and tuning will be a challenge, especially with short manifolds. Camshaft optimization becomes another world when playing with ITBs.

I have always wanted to build my own induction system for small block V8 (for the track). I found some TB pairs here,
Product Categories Throttle Bodies : RHD Engineering

Have thought about trying the Megasquirt system.
MegaSquirt EFI Engine Management Systems, Fuel injection ECU

Like I don't have enough to do.