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

[theKbStockpiler]

I can't seem to find the specifications on 914 throttle bodies. Do 2.0s have a bigger throttle body or intake runners? What about the injectors?

Thanks in advance!

[theKbStockpiler]

For starters , I notice that the 2.0 liter version has the throttle body on the top of the plenum. Some of the bus ads for fuel injection parts show a plenum/throttle body that looks just like the 1.7 914 system.

[aircooledtechguy]

The 1.7L plenums are a similar design to the bus with the throttle body coming out the side. However the volume of the two plenums is vastly different with the 1.7L being very narrow compared to a 1.8L. The 1.8L Porsche plenum is exactly like a bus 2.0L plenum only there is no provision for an EGR.

The 1.7/1.8 runners for the two are also very similar with only the tube diameter being slightly different. Both sets of runners use 4 bolts to mount to the head.

The 1.7/1.8 TBs are similar and are fitted onto the plenum on a cone-shaped mount like a bus. Porsche TBs ALL have TPS-style mounts because they all ran throttle switches of some kind regardless of engine size.

2.0L Porsche plenums are totally different since the TB comes out the top vertically and they have more volume still.

The TB mounts flat with a flat gasket and has a larger butterfly.

The 2.0L runners are a much larger diameter tubing and mount with 3 head studs.

Hope this helps. . .

[theKbStockpiler]

Thanks!

[raygreenwood]

Good answer. Some to add.

The 411/412/914 1.7 plenums and TB are the identical part # as are the runners. The 412 q.8 plenum is identical to the afore mentioned 1.7. So are 1.8L 412 runners. Only the bus as far as I know uses the stepped entry runners on the 1.8L. The 914 might. Ill have to look.

The 1.8 and 2.0 bus has a 5mm (IIRC) larger TB than the 1.7L 411/412/914. The1.7 and 1.8 in 411/412/914 use the same Tb diameter and basic casting.

The 2.0 914 runners...yes larger....plenum is one of the few I have not cc'd. But...the airflow in the 2.0 plenum is the worst of the bunch. Without a splitter under the TB.....you have the streams for all 4 cylinders trying to change directions 90* and overlapping . The turbulence is ugly and you can hear it.

On the 1.7 and 1.8L the angled TB causes teh intake stream to bounce off the side of the plenum immediately after the TB..partially canceling some turbulence and recentering the plume in the plenum. Its not perfect...but is better than the 2.0. Unfortunately its too small for a 2.0......but is dead perfect for a 1.7.

Add 2.0 runners to a 1.7/1.8 plenum and its perfect for a 1.8.

Also a 2.0 bus TB with the positive returrn spring is an excellent upgrade to the stock 1.7/1.8L plenum. Get an exhaust pipe expander and carefully expany and straighten the opening to the plenum behind the TB. If you have a steady hand...it will look just like factory. It bolts right up to the larger 2.0 bus TB and is a decent improvement if you tune for it. Alone...it will do nothing. Ray

[Steve Arndt]

Pyle utilized a 2.1 liter Wasser WBX plenum on his T4 build. He should add to this post the volume and entry/exit info to complete the data set.

[aircooledtechguy]

On my Squareback that is running a 2056, I used a 2.0L bus plenum with the 914 2.0L runners. I simply added a longer case bolt at the flywheel end mount and added a 1/2" spacer to "clock" the plenum so the runners lined-up on the 3/4 side. Then welded a custom flange so I could run the larger 914 2.0L TB w/ TPS for the MS2. Man, does it work awesome!!

[Piledriver]

Pyle utilized a 2.1 liter Wasser WBX plenum on his T4 build. He should add to this post the volume and entry/exit info to complete the data set.

I confess to never actually having measured the volume, but I did check it for leaks!
It SHOULD be pretty close to the 2L 914 volume, I welded in a ~2.5" strip in the middle so it's a Vanagon (same as 2L BUS shape/volume wise) with a side entry TB. The runners are ~30mm or so shorter on the 2L 914 setup, plenum wider to match.

I have run both the 45 (maybe 42, can't recall) 2L Bus and 50MM WBX TB (with a ground flat butterfly), air cleaner right on TB so the tuning is much higher in the range than stock, and quite noticable when it kicks in. I think it works better with the smaller TB, as it pulls a bit lower. (It IS just a 1.8 Bus motor, web73 with 914 2L heads...)

I'll add a VE table from my MS, its pretty good to visualize the bumps in the power curve.
Mind, >3K and under ~87 MAP my AFR target in 19:1, and this table provides accurate results, could use some work in the lower right corner, hard to reach.

[aircooledtechguy]

Pictures are worth. . . well you know.

[Piledriver]

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.

[raygreenwood]

Thanks for the 1.8L 914 plenum picture,. Working on L-jet injected 914's has been so few and far between I did not realize it used a larger plenum than the 1.8L in the 412 and bus. Iherefore I had not realized that it is roughly (exact?) the same plenum as the 2.0 bus.
Ray

[aircooledtechguy]

I pulled out a fist full of TBs and did some measuring for the record. Hope this helps someone down the road. . .

1.7L Porsche TB = 40mm, w/ TPS, cone mounted
1.8L Porsche TB = 42mm, w/ TPS, cone mounted
2.0L Porsche TB = 45mm, w/ TPS, flat mounted
1.6L Beetle TB = 45mm, w/ TPS, flat mounted
2.0L Bus TB = 45mm, w/o TPS, cone mounted

[aircooledtechguy]

Thanks for the 1.8L 914 plenum picture,. Working on L-jet injected 914's has been so few and far between I did not realize it used a larger plenum than the 1.8L in the 412 and bus. Iherefore I had not realized that it is roughly (exact?) the same plenum as the 2.0 bus.
Ray

The only real differences I've seen in the 1.8L/2.0L plenums has been that buses have an EGR valve and mount, where the Porsche plenums do not (though the dimple is there). Internally they then have the exhaust sprayers too which can't be good for flow.

[Steve Arndt]

I pulled out a fist full of TBs and did some measuring for the record. Hope this helps someone down the road. . .

1.7L Porsche TB = 40mm, w/ TPS, cone mounted
1.8L Porsche TB = 42mm, w/ TPS, cone mounted
2.0L Porsche TB = 45mm, w/ TPS, flat mounted
1.6L Beetle TB = 45mm, w/ TPS, flat mounted
2.0L Bus TB = 45mm, w/o TPS, cone mounted

2.1 wasser plenum 50mm cone mount

[Piledriver]

I pulled out a fist full of TBs and did some measuring for the record. Hope this helps someone down the road. . .

1.7L Porsche TB = 40mm, w/ TPS, cone mounted
1.8L Porsche TB = 42mm, w/ TPS, cone mounted
2.0L Porsche TB = 45mm, w/ TPS, flat mounted
1.6L Beetle TB = 45mm, w/ TPS, flat mounted
2.0L Bus TB = 45mm, w/o TPS, cone mounted

2.1 wasser plenum 50mm cone mount

...With an aluminum butterfly that is thick on one side for better low end progression.
These seem to be usually worn out for some reason, the autos have a ~5 lb linkage arm hanging off it.