Tuning the VW Plenum Manifold, Adding a Venturi to the Tube Runners

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westgl

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This thread is to Tune the VW Plenum manifold to get Maximum Torque and Horse Power out of our Single carb. manifold system,

and get rid of any hesitation, or bogging, that is not related to the carb itself,

And find out what works best.

To provide a bike that can get away from a Dead stop, very well.

I am working on a Venturi, that is Loosely based on CM85's Venturi, and according to him, he got this info from Tom the GM engineer, at Langdon's Stovebolt it will have a tapered squish down area it's whole length, for speed up and mixing of air/fuel charge.

I have one done as of now.

1.050" ID Smallest opening of the Venturi, this is the last 1" of the venturi, right before the 90 degree bend going into the head
P1020183

P1020183

1.050" ID Smallest opening of the Venturi, this is the last 1" of the venturi

You are seeing the VW plenum Outlet end you can see that it tapers three times, and has Four ID size changes, 1.300" ID x 3/4" long then 1.170" ID x 2.0" long, then 1.050" ID x 1.0" Long and back to 1.300" ID.
P1020184

P1020184

A look inside the completed Venturi

You are seeing 1.300" x 3/4" long then 1.170" ID x 2.0"...

A look inside the completed Venturi

You are seeing 1.300" x 3/4" long then 1.170" ID x 2.0" long, then 1.050" ID x 1.0" Long
P1020185

P1020185

A look inside the completed Venturi

You are seeing 1.300" x 3/4" long then 1.170" ID x 2.0"...
 
okay im glad you worded this just right ... but im afraid captain discount and tom are really off base here

when you choke down that close to the head ...with smaller opening than the valve ...its causes resistance drag ..harder to turn the crank ....when it its that far from the carburetor ...its almost useless in an oldwing situation there air speed at the carb is a problem with the smaller displacement motor of the oldwing .....this pretty much why 1200s heads vortex type stuff are failures in performance and mpg ...

what you want ...and this is me joedrum speaking ...is there to be full run opening of the runner before the choke .. witch is shape like an hour glass to not place any resistance on the motor ...this ensures deep intake of charge with least amount of effort ...and speeds the air up closer to the carb ...but there are always other variables to this to consider ...

on oldwings its air speed at carb that's more important than this captian discount and tom thing or what ever they named it

im pretty well sure its not very good for oldwing to get good performance .....seems to create drag and way to far from carb

i went with in the runner choke it in the plenium end .....not close to head ...so far its hard for me to discount what I got but I try to ...and if change is needed I do it ....there is a perfect spot for this choke as it is in the oldwing set up ...and im betting where mine is at is a heck of a lot closer than at the elbow and head

but one never knows till they try all things not just think them ...so we will see :mrgreen:
 
Joe i am currently running a 1.050" ID choke in the venturi outlets.

I have to say, it runs Great!!

Torquey, powerful, Fasst!

But i have Not tried this other avenue as of yet,

Being open at the carb end and choking down toward the elbow near the head.

I feel i would not be testing every possible performance aspect of tuning the Plenum and runners, Until tried.

I will provide a ride report.

Even if only more or better air fuel mixture, through the venturi, was the only benefit, that may be enough.

But if more torque can be had, I am all for it, since it is a unknown at this point.

It may be a enormous flop, that provides very poor performance.

At any rate it is worth finding out.
 
yep that's my way of looking at it :builder: :mrgreen: yes id like to hear more on jungos too ....but its hard to get around 44mpg its seems to be close were all close here ....dan got 40 ...most 1100s run at this or below ....I do think this what were talking about is the biggest factor in getting this moded carburation to work good ... :mrgreen:
 
[url=https://www.classicgoldwings.com/forum/viewtopic.php?p=100366#p100366:1r9eka0t said:
dan filipi » Thu Oct 17, 2013 8:14 am[/url]":1r9eka0t]
I'd like to hear more how well jungo's bike is running.
His runners are 1.18" I.D I think and NO chokes.
Click to expand...

Me too,

That Make me think that if Jungo is Not running any chokes at the plenum, then they are the 1.400" ID and wide open, then go down to a 1.18" ID that is like the venturi, starts large ID at the VW plenum, then tapers down toward the head.

My rev1 was also like that, as it had 1.400" ID at VW plenum outlet, then smaller as it gets closer to the head, Hoses were also collapsing further reducing the ID size down smaller the hose Length toward the head, I also had hose stiffeners in the hose reducing down to 1.120" ID near the Oem manifolds

Seems to me like the funnel large at the opening near carb, smaller near oem manifold or head worked good on Rev.1

Question is what works best & Most efficient.
 
[url=https://www.classicgoldwings.com/forum/viewtopic.php?p=100348#p100348:1dq49cpu said:
westgl » Thu Oct 17, 2013 9:07 am[/url]":1dq49cpu]
I am working on a Venturi, that is Loosely based on CM85's Venturi, and according to him, he got this info from Tom the GM engineer, at Langdon's Stovebolt it will have a tapered squish down area it's whole length, for speed up and mixing of air/fuel charge.

I have one done as of now.
Click to expand...
do you have pix of these venturi bits outside of the runners?
 
[url=https://www.classicgoldwings.com/forum/viewtopic.php?p=100370#p100370:2ozb8p4v said:
82a » Thu Oct 17, 2013 8:34 am[/url]":2ozb8p4v]
[url=https://www.classicgoldwings.com/forum/viewtopic.php?p=100348#p100348:2ozb8p4v said:
westgl » Thu Oct 17, 2013 9:07 am[/url]":2ozb8p4v]
I am working on a Venturi, that is Loosely based on CM85's Venturi, and according to him, he got this info from Tom the GM engineer, at Langdon's Stovebolt it will have a tapered squish down area it's whole length, for speed up and mixing of air/fuel charge.

I have one done as of now.
Click to expand...
do you have pix of these venturi bits outside of the runners?
Click to expand...


I will have to take a couple of pictures.
 
From Left to Right in picture,

Left side goes into the VW plenum outlet, it is my 1.400" ID of outlet, then reduces down to 1.300" ID reducer for a smoother transition from Plenum casting area to machined outlet area.

Then that plenum outlet tube of 1.300" ID tapers down to 1.162" as shown in the picture.

PVC pipe, is for a good mechanical seal, and holds everything together, here the OD for seal and ID to hold everything together.

The part to the Right is the 1.050" ID alum choke. This may or may not be needed?


P1020207 1 Comp 355kb

P1020207 1 Comp 355kb

Left to Right
Left side goes into the VW plenum outlet, it is my 1.400" down to 1.300" ID...
 
I may try and use the Tapered tube only first

Tapered tube is:
1.300"ID taper down to 1.162"ID tube.

and then do a road test, to get an idea.

I am sure it would run good.

It is more along the line of Rev.1, except on rev.1 Plenum outlets were 1.400" where as this way they would be 1.300" ID
 
I also was thinking of getting a 1.400"OD tube with a a .091 wall thickness, this reduce the ID down to 1.218"ID, another reduction could be made down to 1.125" or 1.00" which i think is 1.050" ID.

Then open back up to OEM manifold ID
 
Yes

My 1.050" ID section is 1" Long.
the 1.162"ID section is 2" Long.

The 1.300"ID section is 1-1/4" Long.
 
The Other scenario I was thinking of using is take the

1.050" ID choke out of the VW Plenum.

Replace it with 1.400" od x 1.300"id tube x 1-1/4" Long, then reduce to 1.22" ID x 2" long, then down to 1.050" ID at about 1" before the 90 degree bend, then open back to 1.350" ID.

You would have all that engine vacuum suction power down by the head, opened up a little more down at the plenum end.

It will have to be tested
 
I have some 1.250" OD S.S. Grab Bars on there way to me.

They are 1.130" ID.

I will with them use a 1.300"ID x 1.00" long plenum outlet.

The 90 bend toward the head will hold a reducer, in there if the od is a good tight size.

When My Grab bars make it here I will start fabricating them to fit then play with some tuning

But Parts are taking me WAY too long to make manually.

I am going to have to take a week or so off to get my shop straightened out.

I have a couple of die grinders I could knock these 4each 1" id chokes out in less then 1 hour easily.

It takes me way too long to get anything done

I need to build some shelving, to get all my stuff off of the floor and get organized and get my compressor mounted and a new cord installed.

And My drill/Mill needs a new cord to match the Power outlets in my shop
 
haven't run across any more info, not that i looked much

[url=https://www.classicgoldwings.com/forum/viewtopic.php?p=100354#p100354:200r2hdh said:
joedrum » Thu Oct 17, 2013 9:59 am[/url]":200r2hdh]
okay im glad you worded this just right ... but im afraid captain discount and tom are really off base here

when you choke down that close to the head ...with smaller opening than the valve ...its causes resistance drag ..harder to turn the crank ....when it its that far from the carburetor ...its almost useless in an oldwing situation there air speed at the carb is a problem with the smaller displacement motor of the oldwing .....this pretty much why 1200s heads vortex type stuff are failures in performance and mpg ...

what you want ...and this is me joedrum speaking ...is there to be full run opening of the runner before the choke .. witch is shape like an hour glass to not place any resistance on the motor ...this ensures deep intake of charge with least amount of effort ...and speeds the air up closer to the carb ...but there are always other variables to this to consider ...

on oldwings its air speed at carb that's more important than this captian discount and tom thing or what ever they named it

im pretty well sure its not very good for oldwing to get good performance .....seems to create drag and way to far from carb

i went with in the runner choke it in the plenium end .....not close to head ...so far its hard for me to discount what I got but I try to ...and if change is needed I do it ....there is a perfect spot for this choke as it is in the oldwing set up ...and im betting where mine is at is a heck of a lot closer than at the elbow and head

but one never knows till they try all things not just think them ...so we will see :mrgreen:
Click to expand...
 
Well one of my sets of SS grab Bars came in today.

I will start adapting my first venturi to this new grab bar.

These Grab bars are really nice.

They will make for a very professional look.

I hope i can do as well at fabricating them to meet my needs.
 
In looking at the OEM manifolds, they are Not the same ID all the way through the bend length of the manifold run, and out, they reduce in ID some through the bend, there is a section that has a Ridge in about the middle,

I thought before it was a flaw in the ID of the oem manifolds, but now think it may be intentional to reduce the ID some, then opens back up before the head opening.
 
Since our Carb. for the New Single carb Conversion is way up stream, of the head, it is very hard to compare the OEM carb and to use any dimensions from the OEM carb as a size comparison as flow is going through the closer to head placed OEM carb. and i do not think they would act the same way.

But looking at the GL1500, That is a Much better comparison to what we are doing.

I would like to look at a GL1500 Intake manifold, and Carb. off of the bike.

I would like to see the ID of the manifold to see any tapering, or reduction in ID, and also look through the carb. as that carb is a down draft carb.

It may be different. But, It would be good to look at.

I may have to Call my Friend at the local Cycle salvage, to see if he has a GL1500 intake manifold, & Carb. he can lone me for a couple of days

I would love to take some measurements off of the GL1500 parts.

I think that the head intake port & intake manifold flange at head mount, is a much smaller ID on the GL15, than it is on the GL11 or GL12.

The GL15 appears like it has a larger opening at the carb and gets smaller at the head, like the Venturi I want to make.

Could Honda have this all backwards on there later version the GL15?

We are soon to find out.
 

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