tech collaboration: 20V throttles

**oldcorollas** · 17-01-2007, 04:33 AM

Dimensions of Silver Top early throttles (twin linkage, square notch)

cross sectional area of manifold
manifold at head (including notch) = 11.25sq.cm = 37.8mm diameter (equivalent)
manifold at head (NOT including notch) = 8.98 sq.cm = 33.8mm diameter (equivalent)
(effectively, the port at the head in themanifold has dimensions roughly 24x42mm, and the sides have radius12mm..)
manifold at throttle = 15.2sq.cm = 44mm diameter (actually round)
manifold is 67mm in height
change in area is roughly linear (except for the port matching machining marks) (ie, you can form straight line between each side of the manifold)
at head is 59.1% of area at throttle side of manifold

gasket between manifold and throttle = 44.5mm diameter

throttle at manifold = 14.52sq.cm = 43mm diameter (actually round)
43mm diameter is machined until 25-30mm or so from the airbox side (then it turns to cast surface)
throttle opening at airbox face is typically 16.98 sq.cm = 46.5mm diameter (but can vary -/+ 0.5mm)
throttle is 74mm in height.
throttle shaft is 25mm from manifold face
pictures to follow when hosted (anyone wanna volunteer?)

thread length of bolts holding throttles to manifold are 40mm (one) and 23mm (two) measured from end of bolt to the captive washer

**oldcorollas** · 17-01-2007, 05:29 AM

Dimensions of Silver Top late throttles (single linkage, round injector notch)

cross sectional area of manifold
manifold at head (including notch) = 11.65 sq.cm = 38.5 mm diameter (equivalent) (slightly bigger)
manifold at head (not including all notch.. keeping smooth shape) = 10.975 sq.cm = 37.4mm diameter (equivalent)
minimum manifold at head = 10.625 sq.cm = 36.8mm diameter (equivalent) (fair bit bigger than early

manifold at throttle = 15.2sq.cm = 44mm diameter (actually round)(same as early)
manifold is 67mm in height (same as early)
change in area is roughly linear, but there is non linear (curving into port) in the top 1/3rd where the injector sits.
at head is 70-76.6% of area at throttle side of manifold

gasket between manifold and throttle = 44.5mm diameter (same as early)

throttle at manifold = 14.52sq.cm = 43mm diameter (actually round)(same as early)
43mm diameter is machined until 35-38mm or so from the airbox side (then it turns to cast surface)
(more unmachined (= larger) area in late model)
throttle opening at airbox face is typically 17.72 sq.cm = 47.5mm diameter (but can vary -/+ 0.5mm)
(ie, airbox side of late throttle is about 1mm larger diameter, and stays bigger until closer to the butterfly)

BUT, the plastic trumpets.... have an opening of 46.5mm for both early and late throttles!!!!
but opens out to about 47.5mm at the open end (except for the 5mm of lip rounding...
so no taper in the trumpets...

throttle is 74mm in height. (same as early)
throttle shaft is 25mm from manifold face (same as early)

thread length of bolts holding throttles to manifold are 40mm (one) and 23mm (two) measured from end of bolt to the captive washer (same as early)

**oldcorollas** · 17-01-2007, 05:54 AM

Blacktop
so far...

cross sectional area of manifold
manifold at head (including notch) = 12.15 sq.cm = 39.3 mm diameter (equivalent) (bigger than silver)
manifold at head (not including all notch.. keeping smooth shape) = 11.18 sq.cm = 37.7mm diameter (equivalent) (a little bigger than silver)
minimum manifold at head = 10.75 sq.cm = 37 mm diameter (equivalent) (similar to silver?)

manifold at throttle = 19.4sq.cm = 49.7mm diameter (bigger than silver)

manifold is 67 mm in height (same as silver)

gasket is simlar in shape but slightly bigger than throttle and slightly smaller than manifold at the flange.

throttle at manifold = 17.35 sq.cm = 47mm diameter bigger than silver
Throttle butterfly and 10-15mm machined area either side = 45mm bigger than silver

45mm diameter is machined until 35-38mm or so from the airbox side (then it turns to cast surface)(bigger than both silver)
throttle opening at airbox face is typically 19.24 sq.cm = 49.5mm diameter (bigger than both silver)

throttle is 74mm in height. (same as both silver)
throttle shaft is 25mm from manifold face (same as both silver)

thread length of bolts holding throttles to manifold are 40mm (one) and 23mm (two) measured from end of bolt to the captive washer (same as early)
BUT, Blacktop have FLAT washers, Slivertop have SPLIT washers

both blacktop and silver use a single vac line for fuel pressure reg,
but the silver have a vac top off each throttle, whereas the blacktop only has one small rubber vac line (opposit end to the fuel reg)

silvertop throttles fit on blacktop manifold (with the obvious mismatch, but same bolt pattern), but the silvertop trumpets WILL NOT fit on blacktop, as the bolt spacing is wider...( 83(?)mm vs 73mm)

**oldcorollas** · 17-01-2007, 06:50 AM

pictures to follow

**gixer** · 17-01-2007, 10:48 PM

I did flow bench some late 20v silvertop throttles, at 20 inches of water they flowed 256cfm each or 1024cfm total.

**Ben Wilson** · 18-01-2007, 08:49 AM

Originally Posted by gixer

I did flow bench some late 20v silvertop throttles, at 20 inches of water they flowed 256cfm each or 1024cfm total.

You can't use the total number like that - Then engine is only ever using one at a time..

**gixer** · 18-01-2007, 10:30 AM

ha ha I know!!!!i was stating total flow

**DeftAnesthetik** · 19-01-2007, 01:24 AM

is there an in-between version of the throttle assembly? i have dual linkage on mine but i also have a round injector notch.

**psychofox** · 19-01-2007, 09:10 AM

I suspect there was, as I have had 2 sets of 20V throttles, both with the dual linkage cable attachment - the only difference being in the manifold between the head and the throttles. I think the earlier one had a smaller area in the part closest to the head and the injectors nozzles were more enclosed. The latter one is the same as the silvertop one in Toycrash's pictures, but with dual linkage.