- Joined
- Dec 3, 2009
- Messages
- 22,409
- Reaction score
- 246
- Location
- Van Nuys Ca.
- My Bike Models
- 1983 Interstate
2018 KLR 650
2018 BMW S1000 RR
- My Bike Logs forum link
- https://classicgoldwings.com/forums/dan-filipi.122/
It's time now in my trials to start listing what modifications and jetting I've done to the Weber 32/32 dft and the type 4 VW plenum and why I've made these mods.
This is going to be long since there is a lot to explain as to why I've done what I've done.
I owe A LOT of credit to joedrum and the time we've spent chatting talking about the steps I've taken.
It's important to know that I'm running home made 1" runners with custom flanges for the shortest possible distance to the intake valve.
The reason this is important is because different size runners and configurations WILL affect the jetting to dial in this carb properly.
I don't expect others to make runners like I've done but I hope what I have done will help others mod in a single carb whether it is runners like mine or larger runners using the stock intake horns or other plenums.
Ok first, the power valve and an explanation of what it does and how it works.......
What the power valve does is enrichen the primary circuit (jetting) under engine load.
The control for this valve is based on manifold vacuum..... That is vacuum below the throttle plate.
Higher vacuum will close a small ball valve such as when cruising under part throttle and less throttle.
When the ball valve is closed, there is no "enrichment" taking place.
Under a load (accelerating) vacuum will drop below the throttle plate.
The lower vacuum will open the ball valve and enrichen the primary circuit.
How much does it enrichen?
Beats the heck outa me!
Therefore I disabled it by epoxy plugging it's passages.
Actually 4 reasons I disabled it?
1. How much it enrichens is an unknown variable for properly jetting the primary for the best air fuel mixture.
2. Interestingly the manifold vacuum on my bike is damn near or below the 3" of vacuum that this thing starts enrichening when cruising part throttle!
3. The ball valve was leaking past when at rest. This meant I had yet another unknown variable enrichening which was throwing off my jetting attempts and confusing things.
4. This in an EPA carb designed for lean burn idle. It was designed for a 1600 CC+ engine to meet requirements for that engine and it's related smog devices. To tune this carb I've since found taking this thing out of the picture is a great benefit for added simplicity and getting the jetting right.
Improvements I've noticed after disabling it......
1. After reving, rpm drops fast to idle like it should. With it working, drop to idle was much slower, almost like a anti-stall valve.
2. Engine breaking (coasting) has a much better feel.
3. My idle is steadier. When connected, idle would vary up and down in time with the drips that were leaking out of it. (Sheesh)
I found that after disabling it, it was running much too lean under power.
This made total sense, so on to the next step....Re-jetting for best burn and power.
I bumped the primary jet up from 1.07 to 1.15.
It still ran to lean but much better.
Next up, make the lean mix more efficient or...vaporize more of the un-vaporized mixture..... the raw gas that would be wasted otherwise.
How I did that was to add heat to the plenum.
This has proved to work magic!
Where I was too lean without heat, power is smooth and strong.
With the heat the plenum is warm to touch while cruising in 50 degree weather where unheated it would be nearly ice cold.
I plan to insulate the copper and heat plate just the way it is because my design has proven to be very effective.
What I'm doing next is lower the primary jet down to 1.10.
The ride test after will tell me what I do next, insulate the heat plate/plenum, or jet down to 1.05
This is going to be long since there is a lot to explain as to why I've done what I've done.
I owe A LOT of credit to joedrum and the time we've spent chatting talking about the steps I've taken.
It's important to know that I'm running home made 1" runners with custom flanges for the shortest possible distance to the intake valve.
The reason this is important is because different size runners and configurations WILL affect the jetting to dial in this carb properly.
I don't expect others to make runners like I've done but I hope what I have done will help others mod in a single carb whether it is runners like mine or larger runners using the stock intake horns or other plenums.
Ok first, the power valve and an explanation of what it does and how it works.......
What the power valve does is enrichen the primary circuit (jetting) under engine load.
The control for this valve is based on manifold vacuum..... That is vacuum below the throttle plate.
Higher vacuum will close a small ball valve such as when cruising under part throttle and less throttle.
When the ball valve is closed, there is no "enrichment" taking place.
Under a load (accelerating) vacuum will drop below the throttle plate.
The lower vacuum will open the ball valve and enrichen the primary circuit.
How much does it enrichen?
Beats the heck outa me!
Therefore I disabled it by epoxy plugging it's passages.
Actually 4 reasons I disabled it?
1. How much it enrichens is an unknown variable for properly jetting the primary for the best air fuel mixture.
2. Interestingly the manifold vacuum on my bike is damn near or below the 3" of vacuum that this thing starts enrichening when cruising part throttle!
3. The ball valve was leaking past when at rest. This meant I had yet another unknown variable enrichening which was throwing off my jetting attempts and confusing things.
4. This in an EPA carb designed for lean burn idle. It was designed for a 1600 CC+ engine to meet requirements for that engine and it's related smog devices. To tune this carb I've since found taking this thing out of the picture is a great benefit for added simplicity and getting the jetting right.
Improvements I've noticed after disabling it......
1. After reving, rpm drops fast to idle like it should. With it working, drop to idle was much slower, almost like a anti-stall valve.
2. Engine breaking (coasting) has a much better feel.
3. My idle is steadier. When connected, idle would vary up and down in time with the drips that were leaking out of it. (Sheesh)
I found that after disabling it, it was running much too lean under power.
This made total sense, so on to the next step....Re-jetting for best burn and power.
I bumped the primary jet up from 1.07 to 1.15.
It still ran to lean but much better.
Next up, make the lean mix more efficient or...vaporize more of the un-vaporized mixture..... the raw gas that would be wasted otherwise.
How I did that was to add heat to the plenum.
This has proved to work magic!
Where I was too lean without heat, power is smooth and strong.
With the heat the plenum is warm to touch while cruising in 50 degree weather where unheated it would be nearly ice cold.
I plan to insulate the copper and heat plate just the way it is because my design has proven to be very effective.
What I'm doing next is lower the primary jet down to 1.10.
The ride test after will tell me what I do next, insulate the heat plate/plenum, or jet down to 1.05
opcorn:
