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michla
Samba Member
Joined: January 17, 2003
Posts: 331
Location: Wasilla, AK (yes, there's drag racing up here !)
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 Posted: Sun May 09, 2010 11:47 pm Post subject: Weber 48 IDA's want 7-9psi fuel pressure ! |
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I'm working with a pure drag 2287cc Type 1 engine fed by dual 48IDA's. Fuel feed is a Holley Blue (new pump) and regulator, monitored by an AutoMeter indash electric fuel gauge (sender at post-regulator) and VDO direct feed pressure gauge plumbed inline just after the regulator as well. Both read the same PSI. Fuel line is 5/16th's hard line all the way to the back of the car, regulator mounted to firewall (yes--standoff) at rear.
The Webers seem to want 7-9psi of pressure! All my Weber tech books say no more than 4psi and yet the engine "lopes" predictably at idle and sputters as if lean when revved set @ 4psi. Sounds like fuel starvation to me. All lines good, no kinks or plugged this or that.
Should I just go with it or does anybody want to tell me I'm going to spray gas all over a hot engine someday?  |
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Oil Phil-M
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Joined: October 08, 2005
Posts: 541
Location: Vancouver, BC
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| Posted: Mon May 10, 2010 12:28 am Post subject: |
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| I can say when I added a proper regulator to my fuel system to bring the psi down from 5 to below 3 that I needed to turn out my idle jets. I concluded the higher pressure was effectively forcing fuel out of the float bowl ever so slightly. This was with very mildly modified T4 bus with 40IDFs. |
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Bruce
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Joined: May 16, 2003
Posts: 17284
Location: Left coast, Canada
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| Posted: Mon May 10, 2010 1:00 am Post subject: |
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When you're free reving it, sputtering has nothing to do with fuel pressure.
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michla
Samba Member
Joined: January 17, 2003
Posts: 331
Location: Wasilla, AK (yes, there's drag racing up here !)
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| Posted: Mon May 10, 2010 7:22 am Post subject: |
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| Thanx guys...Bruce, why would the sputtering go away when I increase fuel pressure then ? |
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[email protected]
Samba Member
Joined: August 03, 2002
Posts: 12785
Location: Salt Lake City, Utah
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| Posted: Mon May 10, 2010 7:54 am Post subject: Re: Weber 48 IDA's want 7-9psi fuel pressure ! |
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you need to set your floats, then get 3-3.5psi.
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michla
Samba Member
Joined: January 17, 2003
Posts: 331
Location: Wasilla, AK (yes, there's drag racing up here !)
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| Posted: Mon May 10, 2010 9:58 am Post subject: |
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| John, floats are set perfectly using special Weber gauge. |
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[email protected]
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Joined: August 03, 2002
Posts: 12785
Location: Salt Lake City, Utah
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| Posted: Mon May 10, 2010 10:14 am Post subject: |
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once you get 3-3.5psi the carbs will respond properly to your changes.
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Oil Phil-M
Samba Member
Joined: October 08, 2005
Posts: 541
Location: Vancouver, BC
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| Posted: Mon May 10, 2010 10:55 am Post subject: |
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| Quote: |
| once you get 3-3.5psi the carbs will respond properly to your changes |
John, is there any problems running these carbs at a lower psi? I noticed the fuel pressure in my lines increasing after the motor was turned off and things heat up. To compensate I've set the pressure down around 1.5 psi. This way when the pressure increases it still stays below 3.5 psi.
I've never noticed any problems with fuel starvation. Just curious if there is a psi limit on the low end. |
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Dale M.
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Joined: April 12, 2006
Posts: 20377
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Mon May 10, 2010 11:19 am Post subject: |
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As long as you can move enough VOLUME of fuel to keep float bowls full, there is no lower pressure limits....
Dale
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[email protected]
Samba Member
Joined: August 03, 2002
Posts: 12785
Location: Salt Lake City, Utah
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| Posted: Mon May 10, 2010 12:34 pm Post subject: |
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flow is related to pressure. Lower pressure means lower peak flow. If the carbs don't run dry, it's fine. One trick is the mod to increase the float bowl volume (2 holes in each carb).
But there's no reason to set it lower than 3-3.5psi, the carbs are designed to work best at those pressures, so why go lower?
One more thing, do NOT use that chrome "regulator" with the dial on it, those are junk.
Either use a stock pump shimmed
our rotary self regulated to 3.25psi
another electric pump with holley regulator set to 3-3.5psi.
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JasonBaker
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Joined: February 08, 2010
Posts: 1642
Location: Cleveland, TN
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| Posted: Mon May 10, 2010 12:49 pm Post subject: |
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What about the re-jetting the carbs? I had my fuel pressure set at 5lbs and it seemed too lean. I corrected the pressure and adjusted the timing and carbs, head temps went down too.
Last edited by JasonBaker on Wed May 12, 2010 1:03 pm; edited 1 time in total |
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vwracerdave
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Joined: November 11, 2004
Posts: 15297
Location: Deep in the 405
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| Posted: Mon May 10, 2010 2:03 pm Post subject: |
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Have you verified the accuracy of your fuel guage.
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michla
Samba Member
Joined: January 17, 2003
Posts: 331
Location: Wasilla, AK (yes, there's drag racing up here !)
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| Posted: Mon May 10, 2010 2:59 pm Post subject: vwracerDave |
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vwracerDave--I wrote:
| Quote: |
| Fuel feed is a Holley Blue (new pump) and regulator, monitored by an AutoMeter indash electric fuel gauge (sender at post-regulator) and VDO direct feed pressure gauge plumbed inline just after the regulator as well. Both read the same PSI. Fuel line is 5/16th's hard line all the way to the back of the car, regulator mounted to firewall (yes--standoff) at rear. |
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michla
Samba Member
Joined: January 17, 2003
Posts: 331
Location: Wasilla, AK (yes, there's drag racing up here !)
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| Posted: Mon May 10, 2010 3:06 pm Post subject: Jason |
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Thanks Jason, the color of the plugs looks good, but you know it wouldn't hurt to remove the jet stacks to make sure there's nothing clogging them-thanks for making me think of that. Despite the Earl's inline fuel filter and the small inline mesh fuel screens at the entrance to the float bowl, it's amazing how airborne grit gets sucked down the stack chamber.
I'm going to do just that--pull the jet stacks and blow 'em out. |
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alcoholic-bug
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Joined: June 24, 2010
Posts: 2
Location: hawaii
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| Posted: Thu Jun 24, 2010 10:54 am Post subject: E85 use in Deul 48 IDA's |
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Does anyone have experience with using E85 as fuel with duel 48 IDA's??
I can't seem to find any resources of info on using that type of hybird fuel for type 1 engines.  |
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YASHA7FOLD
Samba Member
Joined: January 11, 2012
Posts: 75
Location: Montana.
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| Posted: Sun Mar 18, 2018 4:00 pm Post subject: Re: E85 use in Deul 48 IDA's |
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| alcoholic-bug wrote: |
Does anyone have experience with using E85 as fuel with duel 48 IDA's??
I can't seem to find any resources of info on using that type of hybird fuel for type 1 engines. |
Do not use any fuel that contains ethanol. The ethanol will destroy every rubber seal in a carburetor. |
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jason
Samba Member
Joined: August 07, 2002
Posts: 3445
Location: Garage
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| Posted: Sun Mar 18, 2018 6:49 pm Post subject: Re: Weber 48 IDA's want 7-9psi fuel pressure ! |
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| Only rubber is on newer accelerator jets. |
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