Five Reviver
Silver Level Sponsor
Sorry DW I haven’t been able to but for consolation here’s the latest 40/45 DCOE comparison video from Penguin Motors
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Enjoy.
Weber 40 DCOE mods for more flow
- Thread starter spmdr
- Start date
Sorry DW I haven’t been able to but for consolation here’s the latest 40/45 DCOE comparison video from Penguin Motors
spmdr
Diamond Level Sponsor
So, the above video confirms, when using 40s, 32 to 33 mm chokes are about as good/big as you can
effectively use.
This tells me the Z World chart above has some validity and my efforts (moding 40s) are on the right trail.
In this test, optimized 40s made 144 HP and 140 ftLBs
Optimised 45s made 160 HP (+16) 152 lbs (+12) (with no loss vs 40s, above 2500 rpm).
So, Five Reviver, In light of the above, I think you should put in for a Name change.
More like Five REVer...?
BTW, Reviver/'REVer, did you match (increase) the intake size to the New 45s?
DW
effectively use.
This tells me the Z World chart above has some validity and my efforts (moding 40s) are on the right trail.
In this test, optimized 40s made 144 HP and 140 ftLBs
Optimised 45s made 160 HP (+16) 152 lbs (+12) (with no loss vs 40s, above 2500 rpm).
So, Five Reviver, In light of the above, I think you should put in for a Name change.
More like Five REVer...?
BTW, Reviver/'REVer, did you match (increase) the intake size to the New 45s?
DW
Doesn't all this depend on whether or not the tightest restriction in intake tract is the venturi? So, if the manifold runners or intake port on the head are only 38mm, for example, then isn't a 45 venturi too large for that? I wonder if the Ford X head in the video has at least 45mm I/D all the way through? So many questions . . . .
spmdr
Diamond Level Sponsor
Thor, I'm not an expert on areo or even Physics, but my guess
is the intake path is a variety of restrictions.
Improving/reducing Any of the restrictions improves overall flow.
And under the heading of flow is the component of velocity.
Carbs function with velocity changes.
In the performance world, the trick is to get the least velocity
change in the carb and still have the carb function.
In the Alpine case, the stock (S5) intake valve is about 39mm.
There is a general relationship with intake valve/port size and
max usable Carb venturi size.
The point with this thread is that the typical 40 DCOE with STD
30mm chokes is too small/a significant restriction for good High
RPM Alpine engine performance.
BUT, going to the required bigger choke size (36+mm) is beyond the functional
range of the 40 DCOE.
....And how much can the 40 DCOE flow be improved?
So Thor, 45mm chokes wouldn't be much of a restriction.
45mm Webers come standard with 36mm chokes.
DW
is the intake path is a variety of restrictions.
Improving/reducing Any of the restrictions improves overall flow.
And under the heading of flow is the component of velocity.
Carbs function with velocity changes.
In the performance world, the trick is to get the least velocity
change in the carb and still have the carb function.
In the Alpine case, the stock (S5) intake valve is about 39mm.
There is a general relationship with intake valve/port size and
max usable Carb venturi size.
The point with this thread is that the typical 40 DCOE with STD
30mm chokes is too small/a significant restriction for good High
RPM Alpine engine performance.
BUT, going to the required bigger choke size (36+mm) is beyond the functional
range of the 40 DCOE.
....And how much can the 40 DCOE flow be improved?
So Thor, 45mm chokes wouldn't be much of a restriction.
45mm Webers come standard with 36mm chokes.
DW
Five Reviver
Silver Level Sponsor
DW I took out heaps of metal from the intake port.
As to REVer, this Alpine keeps teaching me that it takes a lot of reviving to enable the revving, which in turn leads to more reviving. A nasty little circle!
As to REVer, this Alpine keeps teaching me that it takes a lot of reviving to enable the revving, which in turn leads to more reviving. A nasty little circle!
Jay Laifman
Donation Time
Jay Laifman
Donation Time
These are all 32s for 40s. I found a set of 33s that I'll probably buy as well. This is for the 1300 cc Alfa racing motor.
One thing I don't know, the "better" set with the nicely curved intake side and sharper mid section, all are great except one has a bunch of small pock holes in it. I don't know if those would cause any harm. If anything they might further disturb the air flow and keep the fuel atomized. But, I'd like to find a smoother one. Or maybe those holes can be filled with epoxy or something. Or just ignored.
One thing I don't know, the "better" set with the nicely curved intake side and sharper mid section, all are great except one has a bunch of small pock holes in it. I don't know if those would cause any harm. If anything they might further disturb the air flow and keep the fuel atomized. But, I'd like to find a smoother one. Or maybe those holes can be filled with epoxy or something. Or just ignored.
spmdr
Diamond Level Sponsor
Jay, I would suggest you NOT use the "better"
rounded front edge chokes.
Because they do not match the size of
the Aux venturi.
I have the same issue with the 34s I bought.
I think the better (laminar) flow is with
a choke with the same size leading edge inside diameter
as the Aux ventury exit edge inside diameter.
However, there is a case to be made that SOME
turbulence is desirable in strategic places
in a Carb, to enhance fuel vaporizing??
...at the expense of flow???
I'm having a hard time seeing how turbulence at
the transition of the Aux venturi to the choke is a good thing.
BUT, maybe it is??
DW
rounded front edge chokes.
Because they do not match the size of
the Aux venturi.
I have the same issue with the 34s I bought.
I think the better (laminar) flow is with
a choke with the same size leading edge inside diameter
as the Aux ventury exit edge inside diameter.
However, there is a case to be made that SOME
turbulence is desirable in strategic places
in a Carb, to enhance fuel vaporizing??
...at the expense of flow???
I'm having a hard time seeing how turbulence at
the transition of the Aux venturi to the choke is a good thing.
BUT, maybe it is??
DW
Jay Laifman
Donation Time
Interesting. That makes sense. Great to know. I guess the open question then is if the faster opening to the trailing end adds other benefits.