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Posted by: orange914 Dec 13 2007, 03:20 PM

just wondering what t.b. conversions are out there and what issues have been incured?.
what size is the stock t.b. anyway

Posted by: Jake Raby Dec 13 2007, 04:59 PM

The stock unit is adequate for 150HP and 2300ccs....

Posted by: Krieger914 Dec 13 2007, 05:18 PM

The stock TB has a 45mm plate. You could bore out the stock TB 3 mm or so before you start to run out of roomand have a new plate made. The opening in the plenum it bolts to is wider than the TB- I can't remember but its about 50 mm. I don't think anyone makes conversion.

Posted by: 914Sixer Dec 13 2007, 05:45 PM

Jake said it all !!!

Posted by: jd74914 Dec 13 2007, 06:09 PM

Don't bore it out.

Think of it using this equation:

m(dot)= p*A*V.
(p is a constant, the density of air)

The engine consumes a finite amount of air (M(dot)). This value is only dependent on engine speed. The air's speed is inversely dependent on the area of the TB/runners it flows through (A). When these have larger cross-sectional areas the air inside of them moves at a slower rate (V), which kills efficiency. Maximum power can be found with air speeds of around .4 or .5 mach usually. Once you go supersonic efficiency drops though.

Basically you want high intake port air velocity for best performance.

Posted by: orange914 Dec 13 2007, 11:08 PM

sounds like any mods would defeat any gains for street 2056 d-jet

Posted by: TeenerTim Dec 14 2007, 09:53 AM

Is the 2.0 bigger than the 1.7 and do the 2.0 injectors flow more than the 1.7?

Posted by: jd74914 Dec 14 2007, 10:03 AM

2.0 Injectors flow significantly more than 1.7s. I would assume the TB is also larger.

Posted by: Jake Raby Dec 14 2007, 02:28 PM

The 2.0 plenum is larger, but it's design is the least effective of all the plenums, even on larger displacement engines. Design overcomes size in this situation.

Boring out the stock T/B without altering the engine and the rest of the intake system only HURTS drivability, especially throttle response. Been there, done that.

Posted by: orange914 Dec 14 2007, 05:38 PM

is air flow of the plenum ineffective becouse of shape (boxy/not smooth air flow) or other factor/s? if so has any one messed with upgrading negatives of 2.0 plenum?

mostly just curious

Posted by: sean_v8_914 Dec 15 2007, 12:58 PM

jake:
tell us more about the 2.0 plenum. would a 1.8 plenum work better with a 2.0 TB on a 2.0? what did you discover to be the problem with this plenum?

Posted by: ConeDodger Dec 15 2007, 01:04 PM

Mike,
Your toes are on the diving board at the pool of misery. Change that and you have a chain of changes you must make to rectify the way the car runs.

Posted by: orange914 Dec 15 2007, 05:16 PM

yep, i guess i was more curious. mostly q&a session while im waiting on my cylinders for the next stage of the build. hopefully i'm not leaving any stones unturned on this 1.7 to 2056 d-jet conversion. jeff's going to set the mps/check the harness. always good to know others experiances with this stuff

mike