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[ROOT]/includes/functions.php:3887) [phpBB Debug] PHP Warning: in file [ROOT]/includes/functions.php on line 4755: Cannot modify header information - headers already sent by (output started at [ROOT]/includes/functions.php:3887) [phpBB Debug] PHP Warning: in file [ROOT]/includes/functions.php on line 4756: Cannot modify header information - headers already sent by (output started at [ROOT]/includes/functions.php:3887) RS Motorsport :: Classic Speed Restored • View topic - weber fuel delivery
Going over my new MK1 (will post pics as soon as I can wheel it out of the garage) and it has rubber lines all the way from tank to the weber 45's. it has a large efi style fuel filter canister into a carter style rotary vane pump then through another smaller clear plastic style paper element style filter, and then goes through a small fuel/oil style cooler under the car before making it's way to the carbs. Firstly I wanted to replace the bulk of the fuel line with steel line. I bought 8mm steel line for this purpose but am now wondering if that is sufficient (approximate internal dia 6.2mm) after reading up on webers a bit more and realising how important volume is. Will this line size be sufficient? it's a heavily modified 2.3 pinto.
Second question is, do I need a fuel cooler or is it just another thing to go wrong for no perceptible advantage, and restricting flow?
Essentially I was thinking remove the cooler and maybe the second element style filter (is that really needed as well?) and use steel lines along the underneath to the engine bay to a holley low pressure regulator I have taking as smooth a path as possible.
6.2mm id pipe is way to small. I run 10mm id hose from back to front on a mild 2lt Pinto running 2 x 45 Dellorto's. Most people with high horsepower motors would be using at least 12mm id hose. I use a Commodore EFI filter at the back without any issues.
Whats the ID of your pressure reg fittings, t-piece, or banjo fittings into the webers? If you have a decent pump with a good flow rate (as apposed to pressure) then there should be no need to go such extremes.
You don't need 12mm-1/2" fuel lines or anything near that and if you were running a return line to regulate the pressure a 1/4" fuel line would be fine with a pair of 45's as don't forget guys you could have 2"-50.8mm fuel lines if you like but you still have to pass it through the needles and seats How big are your needles and seats?
Thanks for all the input guys, Danny, i'm not sure what sizes the needle and seats are, haven't got that far yet in my experiences with webers, Iv'e just come from the land of big V8's. I have a holley (1-4psi) regulator which I was going to use 5/16 (about 6.2mm ID) barb fittings on both the inlet and outlet. I can't see that I need to go bigger on the carb side of the regulator as the genuine holley T piece fuel union that attaches to the first carb is only about 6.2mm internal diameter so anything bigger is only going to get choked up at that point. I can see though that a larger fuel line from the rear to the regulator at the front of the car could be desirable as it would reduce pressure loss and increase available volume up to the point of the regulator. It's a Carter rotary vane pump with the part number 152-875 which I can find no specs for with a google search but have deduced as best I can that it's a marine version of their low pressure (5-6psi ish) 72GPH pump (not confidant on the flow specs though). I'm not running a return line either, and I think i'll discard the fuel cooler and filter after the pump and just keep the filter before the pump. I appreciate there are many different opinions on fuel line size but irrespective of HP and engine size etc, I struggle with the idea of having huge lines 10-12mm ID when it still comes down to 6mm ID at the genuine weber fuel fittings. Oh and the motor puts out approx 200HP if that figures into the equation. So all in all i'm leaning towards an 8mm ID main line form the pump to regulator, with nothing else in between, unless someone can come up with a genuine calculation to prove otherwise, or am I missing some greater point here?? And please don't take that as discarding the advice of those who say I need bigger, I just know i'm sure it's possible to actually do some calculations on fuel requirements for any engine (I don't know how to do these) but unless someone can hit me with these calculations I have to draw what feels like a common sense conclusion on everyones suggestions that vary quite considerably. I appreciate all your inputs though, feel free to keep adding to the discussion. Cheers, Llewellyn
The Dynomation 5 program I have will model fuel flow requirements. If you like you could PM your engine specs to me and I can run it through. I will need to know almost everything about your small block, cylinder head, cam specs, valves sizes.....etc to run the sim properly. Just as an example, the data suggests that at 8500RPM the calculated air fuel requirements would be 118 lbs/hr, converted to metric using an SG of .72kgs/L gives you 75L/Hr. To keep it honest I re-ran the sim using E85 and the fuel rate goes up to 113L/Hr.
I run dellorto 48's on my cosworth with a 12V Facet fuel pump and a fuel pressure regulator set at 2psi with 3/8" lines. Not saying this is ideal either just what I use.
Mk 2 Escort Sports Sedan 2L N/A YB Cosworth engine rebuild completed. 100% Mongrel FORD...actually Oz block & crank, Yankee pistons, English head & rods, Ozzie cams & valves!
i have been running a 2.1 pinto on 48,s revs to 8000 , for 30 yrs now with a std mech fuel pump , & 1/4" id lines have tried an adj reg with no discernable difference i know mech pump robs a bit of hp but electric pumps are more prone to failure i do have an elec pump mounted in the boot ready for quick change just in case but never used it no need to overcomplicate fuel systems no point using lines bigger than needle & seat size
Thanks for the offer of doing the calculations for me steve but I unfortunately don't know enough about my engine specs.
Appreciate all the input people, Interesting seeing others take on the many factors involved. Have decided to just run 3/8th line with as little restriction/fittings etc as possible. I get the impression that should be either adequate or more likely more than adequate.
Something else that occured to me that may throw another spanner in this discussion is the use of EFI style filters. the previous owner ran one before the pump and as others have mentioned they use them also but I have also read of the different flow charachteristics of them compared to carbureted filters. The specs you can find for them also while advertise as flowing enough, they would surely be measured at EFI like pressures rather than 2-3psi as we are running?? yet any conventional carb filter seems like it would also be a restriction with their small barbs/elements etc. Does anyone have any thoughts on this or know of a particular model/part number they have found to work well, other than shelling out for a fancy expensive race one??