Differences in 1.7 ,1.8 and 2.0 throttle-bodies , plenums..

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Re: Differences in 1.7 ,1.8 and 2.0 throttle-bodies , plenum

Post by Lars S » Wed Aug 14, 2013 11:29 pm

Piledriver wrote:
aircooledtechguy wrote:Pictures are worth. . . well you know.
I agree.
Heres my widened Vanagon plenum setup next to a std Vanagon Plenum. (looks identical shape to 2.0 bus)
Made to be same width as 2.0 914 and tweaked slightly to work with 2.0 914 manifolds.
What characteristics would a plenum with more volume bring to an engine generally, i.e. what are the ups and downs?


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Re: Differences in 1.7 ,1.8 and 2.0 throttle-bodies , plenum

Post by Piledriver » Thu Aug 15, 2013 1:44 am

All else being the same, only enlarging the plenum would shift the resonance peaks lower on the scale, and probably boost the upper end... might reduce the "Q" of the circuit, and broaden the range of resonance while reducing the peaks somewhat, vs a smaller plenum with everything tuned to the same peaks.

In practice, with the air cleaner directly on the TB, instead of an ~14" duct feeding it, it moves the range down somewhere useful, and adding a couple inches in the middle has the side benefit that it is wide enough to physically connect to the shorter 914-2L runners. (That was the primary reason)

~Everything effects the tuning of the intake to some extent.
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Re: Differences in 1.7 ,1.8 and 2.0 throttle-bodies , plenum

Post by Lars S » Thu Aug 15, 2013 4:07 am

In my thoughts a smaller plenum volume would give quicker throttle response or this may only be in theory and never noticeable...?


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Re: Differences in 1.7 ,1.8 and 2.0 throttle-bodies , plenum

Post by Piledriver » Fri Aug 16, 2013 3:20 pm

My throttle response is ~ITB-like, I suspect you would be hard pressed to measure the difference.

Note: A lot of folks misinterpret huge throttle area and LACK of fine throttle control for "throttle response" on ITBs and setups with oversize TBs. An "on/off switch" is not better or faster throttle response, although it may feel "sportier".
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Re: Differences in 1.7 ,1.8 and 2.0 throttle-bodies , plenum

Post by fusername » Sat Dec 28, 2013 11:51 am

does anyone have a pic of a 914 2.0 FI setup fully done? I have from the plenum down, no TB or air cleaner, and I am wondering exactly how they whent about it from the factory. I think this will be the basis for my 2.2L bus motor with MS.
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Re: Differences in 1.7 ,1.8 and 2.0 throttle-bodies , plenum

Post by Piledriver » Sat Dec 28, 2013 1:12 pm

No, but Jake proved the tangent entry style ~every other T4 setup has made significantly more HP.
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Re: Differences in 1.7 ,1.8 and 2.0 throttle-bodies , plenum

Post by Lars S » Sat Dec 28, 2013 1:14 pm

fusername wrote:does anyone have a pic of a 914 2.0 FI setup fully done? I have from the plenum down, no TB or air cleaner, and I am wondering exactly how they whent about it from the factory. I think this will be the basis for my 2.2L bus motor with MS.

This is a 73 914, 2.0:
http://www.914world.com/bbs2/uploads/po ... 922089.jpg


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Re: Differences in 1.7 ,1.8 and 2.0 throttle-bodies , plenum

Post by fusername » Sat Dec 28, 2013 4:18 pm

Piledriver wrote:No, but Jake proved the tangent entry style ~every other T4 setup has made significantly more HP.
dang. I was hopeing I could just weld in a small teepee/collecter kinda dealio under the downpipe, but I assume that was tried out? Looks like I could just use a 2.0 bus plenum, but it still exits on the wrong side, I need to run my intake out thru the drivers side.
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Re: Differences in 1.7 ,1.8 and 2.0 throttle-bodies , plenum

Post by Steve Arndt » Sat Dec 28, 2013 5:42 pm

Flip it upside down and move the mounting bracket. That will change the cylinder offset to match and reverse the TB location.

When Pile made his wider plenum he cut it at the seam. You could cut it and reverse "half" of it to get the geometry you need.

Grab a 2.1 vanagon plenum and cut it up.

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Re: Differences in 1.7 ,1.8 and 2.0 throttle-bodies , plenum

Post by Piledriver » Sat Dec 28, 2013 7:26 pm

Steve Arndt wrote:Flip it upside down and move the mounting bracket. That will change the cylinder offset to match and reverse the TB location.

When Pile made his wider plenum he cut it at the seam. You could cut it and reverse "half" of it to get the geometry you need.

Grab a 2.1 vanagon plenum and cut it up.
It will be a very, very tight fit ahead of #3. The factory setup works well...
(Trying desperately to figure out why the stock setup for a bus will not work in a bus...)

That's what mine is made from, bus 2.0 is ~ same dimensions, IIRC the spigots for the Vanagon head pipes are a tiny bit bigger, and the TB taper allows for a 50MM TB OR a 45mm TB without a ridiculous step.
I widened mine to more or less match the 2L 914 plenum volume and fill the gap between the shorter 914 runners.
I am apt to pop out an even wider one for shorter runners, although I have a potentially interesting slot feed dual plenum idea I want to try RSN.

The 2L bus plenum won't get you there as easy if you want to use the slightly larger TB.
(I ended up running the smaller factory 2L 45mm bus TB, as the Vanagon TBs are usually worn out for some reason)

I don't think anyone ever tried Ray Greenwoods suggested "turtle" but you are still trying to get air to turn a hard 90 degrees in a short distance. I suspect all else being the same the factory 2L bus or Vanagon plenum would still kick it's ass, esp if you can widen the plenum, get the runners and TB to the right length so everything hits together.
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Re: Differences in 1.7 ,1.8 and 2.0 throttle-bodies , plenum

Post by Lars S » Sun Dec 29, 2013 12:02 am

If you dont happen to know, some people have made a solution with TWO throttle bodies: :D

http://www.914world.com/bbs2/index.php? ... -jet++twin


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Re: Differences in 1.7 ,1.8 and 2.0 throttle-bodies , plenum

Post by fusername » Sun Dec 29, 2013 12:14 pm

hmm, I guess I need to measure and document what I got. I need to come out the drivers side as I am putting a donaldson air filter OUTSIDE the vehical, and if it comes outside on the pass side the sliding door will hit it, so I need to come out the drivers side. THe unidirectional 914 intake was a big plus for that, easiest to make it go wherever I needed, plus better access to the TB since I might want to put a TPS on it, and when you are tinkering access is a big plus. I had considred flipping a bus plenum but I had no idea how it would line up. I thought the 914 2.0 might make better power since the path to each runner is ~the same, vs a ljet style causing I assume a vortex in there, which may mess with a MAP sensor based FI, or atleast make it location dependant.
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Re: Differences in 1.7 ,1.8 and 2.0 throttle-bodies , plenum

Post by fusername » Sun Dec 29, 2013 12:15 pm

this basically proves tho that I need to make a mockup motor, good thign i didn't throw away those blown 1700 heads. shame I melted my last spare case down for ingots...
give a man a watch and he'll allways know what time it is. give him two and he can never be sure again.

Things are rarely just crazy enough to work, but they're frequently just crazy enough to fail hilariously.

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