Author |
Message |
corradolvr Samba Member
Joined: August 18, 2008 Posts: 297 Location: WA
|
Posted: Sun Aug 29, 2010 7:26 pm Post subject: Dual Carb Plumbing |
|
|
Got Dual IDF Weber 40s and I'm not really sure exactly how to plumb them. I thought I could just use a "T" of the output from the fuel pump then run a line up to each one, but I don't want it to look sloppy. Does anyone have any pictures of there dual carb plumbing, or advice? _________________ My Build Post
http://www.thesamba.com/vw/forum/viewtopic.php?t=3...highlight= |
|
Back to top |
|
|
tanner_122 Samba Member
Joined: July 20, 2009 Posts: 1224 Location: Norco CA
|
Posted: Sun Aug 29, 2010 7:29 pm Post subject: |
|
|
i run one out of the pump and have a t behind the dog house and they only place u really see my fuel lines is where they go to the carbs
im running dell 40's _________________ 91 jeep Cherokee "TANK" |
|
Back to top |
|
|
corradolvr Samba Member
Joined: August 18, 2008 Posts: 297 Location: WA
|
|
Back to top |
|
|
tanner_122 Samba Member
Joined: July 20, 2009 Posts: 1224 Location: Norco CA
|
Posted: Sun Aug 29, 2010 8:03 pm Post subject: |
|
|
oops should have given more details
my cell is in the back seat then it goes out to my holly red pump then under the package tray to a pressure regulator then filter then the T going to each carb _________________ 91 jeep Cherokee "TANK" |
|
Back to top |
|
|
Glenn Mr. 010
Joined: December 25, 2001 Posts: 76902 Location: Sneaking up behind you
|
|
Back to top |
|
|
corradolvr Samba Member
Joined: August 18, 2008 Posts: 297 Location: WA
|
|
Back to top |
|
|
tanner_122 Samba Member
Joined: July 20, 2009 Posts: 1224 Location: Norco CA
|
Posted: Sun Aug 29, 2010 9:31 pm Post subject: |
|
|
mine is very similar but i used braided line _________________ 91 jeep Cherokee "TANK" |
|
Back to top |
|
|
bartman Samba Member
Joined: February 22, 2004 Posts: 767 Location: palatka, fl
|
Posted: Mon Aug 30, 2010 2:34 pm Post subject: |
|
|
Here's another. I'm running IDFs now with this setup:
|
|
Back to top |
|
|
Scott Gilbert Samba Member
Joined: August 03, 2004 Posts: 71 Location: San Diego, CA
|
Posted: Mon Aug 30, 2010 11:09 pm Post subject: |
|
|
One small detail is to make the hose lengths equal to each carb from the tee. Under hard acceleration when both inlet needles are open fuel will flow to the path of least resistance. I had my 2276 plumbed like Glenn's and couldn't figure out why the plug readings were different from side to side. I changed the fuel hose to equal length and the plugs became identical. |
|
Back to top |
|
|
corradolvr Samba Member
Joined: August 18, 2008 Posts: 297 Location: WA
|
|
Back to top |
|
|
Glenn Mr. 010
Joined: December 25, 2001 Posts: 76902 Location: Sneaking up behind you
|
Posted: Tue Aug 31, 2010 3:40 am Post subject: |
|
|
Scott Gilbert wrote: |
One small detail is to make the hose lengths equal to each carb from the tee. Under hard acceleration when both inlet needles are open fuel will flow to the path of least resistance. I had my 2276 plumbed like Glenn's and couldn't figure out why the plug readings were different from side to side. I changed the fuel hose to equal length and the plugs became identical. |
Weird... i've not seen a difference in the 8000+ miles i've driven. _________________ Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"
Member #1009
#BlueSquare |
|
Back to top |
|
|
Scott Gilbert Samba Member
Joined: August 03, 2004 Posts: 71 Location: San Diego, CA
|
Posted: Tue Aug 31, 2010 10:35 am Post subject: |
|
|
It is only under hard acceleration when both float bowls are requiring a lot of fuel. Depends on needle & seat size (3 mm in my case). It would never be a problem with normal street driving. But most of us with dual carbs like to accelate hard on the street from time to time.
Best way to test it is to clean your plugs and drag race all day! Or put an O2 on each side and datalog.
Then again it is just easier to use 6" more of hose and put the tee in the middle.
[quote="Glenn"][quote]
Weird... i've not seen a difference in the 8000+ miles i've driven.[/quote] |
|
Back to top |
|
|
Glenn Mr. 010
Joined: December 25, 2001 Posts: 76902 Location: Sneaking up behind you
|
Posted: Tue Aug 31, 2010 11:01 am Post subject: |
|
|
For a dead stop and shifting at 7600rpm I have no problem running up to 107mph where I shift into 5th and its still pulling.
While I'm not doing that everyday I do drive the engine hard at times and the last time I pulled the plugs to check them they were pretty even from cylinder to cylinder. And that's with 8000+ miles on them.
BTW.. ever see how they plumb the 4 IDAs on a Cobra?
_________________ Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"
Member #1009
#BlueSquare |
|
Back to top |
|
|
[email protected] Samba Member
Joined: July 02, 2003 Posts: 591 Location: Florida Space Coast
|
Posted: Tue Aug 31, 2010 12:12 pm Post subject: |
|
|
It probably makes more of a difference depending on the output of the fuel pump.
I think the cobra uses a high output pump and those lines are rather short. _________________ 1974 Standard Beetle to Baja Bug
http://picasaweb.google.com/fvee1234/BajaBug02# |
|
Back to top |
|
|
Scott Gilbert Samba Member
Joined: August 03, 2004 Posts: 71 Location: San Diego, CA
|
Posted: Tue Aug 31, 2010 2:32 pm Post subject: |
|
|
Glenn,
I’m just saying what I have seen in my case. Take it for what it is worth. Don’t know why you wouldn’t think that putting the tee in the middle is a good idea. Look at the fuel flow and pressure as it travels through the fuel line. Fuel pressure is only 3.5 psi to begin with, what is going to happen when the 1st carb N/S is completely open allowing all available gas in? Pressure drop to the 2nd carb. 1st carb is receiving more psi because it is closer to the pump. If you have a tee and equal length fuel hoses that issue is eliminated.
The dynamics of the engine are different under hard acceleration than when cruising. My case was exactly the same as you. My plug readings looked great because I used the car on the street mostly, but when drag racing it didn’t pull as hard as I thought it should in 4th gear. I found that in 4th gear the 1-2 side carb was running out of gas. I changed the fuel line, it solved the problem, plugs looked great, and the car went faster. Pulled hard all the way through 4th gear. Went faster on the street too! My stock weight street car would run 11.70s @ 115mph with a 2276 & IDAs. I shifted at 8K without taking my foot off the gas.
Maybe they plumbed IDAs on a Cobra like that back in the day, but that doesn’t mean it was right. |
|
Back to top |
|
|
Glenn Mr. 010
Joined: December 25, 2001 Posts: 76902 Location: Sneaking up behind you
|
Posted: Tue Aug 31, 2010 2:36 pm Post subject: |
|
|
Scott Gilbert wrote: |
Maybe they plumbed IDAs on a Cobra like that back in the day, but that doesn’t mean it was right. |
I think Carol Shelby knows a few things about building hi-po engines.
Anyway... we're splitting hairs when talking about street engines. _________________ Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"
Member #1009
#BlueSquare |
|
Back to top |
|
|
VIN Samba Member
Joined: June 01, 2006 Posts: 941 Location: phoenix
|
Posted: Tue Aug 31, 2010 5:55 pm Post subject: |
|
|
best pic. i have right now, electric fuel pump up front.
equal length lines from the tee.
|
|
Back to top |
|
|
corradolvr Samba Member
Joined: August 18, 2008 Posts: 297 Location: WA
|
Posted: Tue Aug 31, 2010 11:48 pm Post subject: |
|
|
That got complicated. Well If they are tuned with different lengths shouldn't that accommodate the length difference? in a pressure system with relatively low changes in height, a fluid less dense than water, and low pipe friction factor I wouldn't think it wouldn't matter a whole lot. _________________ My Build Post
http://www.thesamba.com/vw/forum/viewtopic.php?t=3...highlight= |
|
Back to top |
|
|
[email protected] Samba Member
Joined: July 02, 2003 Posts: 591 Location: Florida Space Coast
|
Posted: Wed Sep 01, 2010 5:24 am Post subject: |
|
|
I think it would only be an issue when you are close to exceeding the ability of the fuel pump. If you have more than enough gas being pushed (like FI with a return line) then this won't be an issue, but if you are having trouble keeping the bowl full, then it would be. _________________ 1974 Standard Beetle to Baja Bug
http://picasaweb.google.com/fvee1234/BajaBug02# |
|
Back to top |
|
|
joescoolcustoms Samba Member
Joined: August 08, 2006 Posts: 9054 Location: West By God Virginia
|
Posted: Wed Sep 01, 2010 7:26 am Post subject: |
|
|
I friend that races Super Stock Class bought a new to him drag car, changed how the fuel lines were run and picked up 0.010 in the 1/4. Doesn't sound like much, but it put him to the point of just under the record for that class.
I cannot see it making any difference on a street engine, I would think the tickets from so much wide open throttle use would be of a bigger concern. If your leaning out one side, your fuel pump is not adequate. _________________ Bad News Racing 2018 NORRA 1000 3rd in Class
Best Day Ever Racing 2022 NORRA 1000 2nd in Class and first All Female team to complete the race
Everyone is gifted. Some just do not open the package.
Looks like it was painted with a live chicken,polished with a brick and buffed with a pine cone |
|
Back to top |
|
|
|