Fuel Pressure + Dellorto

[rosso]

Hi all,

I recently installed a single Dellorto DHLA40 on Lynx manifold onto my 8V 1800 RV engine in a MK1 Golf, this engine was an upgrade from the original 1600 a year ago.

I used the original parts back on this engine with original Solex carb until the carb gave up the ghost. I am writing to ask if anyone thinks i may need an upgraded fuel pump, i assume the fuel pump is on the front of the engine and is a mechanical type?

I am using a simple adjustable Fuel Pressure Reg with the new carb as Dellortos are not rated to more than 2.5-3PSI of fuel pressure i have been told. Will this work with the original pump setup and return line etc if i mount FPR on carb side of the fuel line Y joint?

Thanks for any help.

[Jarred]

Carbs generally dont need much fuel pressure, but rather more volume. (ie, high volume, low pressure) So I've been told/read.

Providing you're mechanical pump is working fine, you shouldn't have any issues just using that, unless the carb is really thirsty, IMO.

Read through this sticky. Plenty of good info.

http://www.vwwatercooled.org.au/newforum/upload/showthread.php?t=22010

[twin eng, twin turbs]

I have done this conversion before on a 1.8l 8v, and jarred is right about the fuel flow / volume.

I originally fitted a 32/36 dgv webber on a ts passat manifold and found the fuel flow from the standard pump was up to the task. But this is about the largest carby the original pump is able to flow.

I upgraded to a 40mm DCOE webber on a lynx manifold and encountered some issues that is very relevent to your setup. The standard pump was unable to flow enough fuel for top end power. With a regulator set up aswell, any revs above 4500rpm it leaned off on the dyno so i upgraded to a holley blue pump which was overkill but did the job well. Another tuning issue that was encountered was the lynx manifold design is hard to tune for with cylinders 1 and 4 feed off one throat and cylinders 2 and 3 off the second throat of the carby. 2 and 3 were easy to tune due to the similar length and volume of the runners, but 1 and 4 are hard to tune with a big difference in runner volume and length resulting in cyl 1 running to rich constantly fowling the spark plug so cyl 4 could be right.

[Peter Jones]

I found a Facet wasn't keeping up with twin Dells.

I've just installed a 72gph Carter Rotary Vane pump which seems to be just right.

I'm told 6psi is the nominal pressure for the Dellorto/Webers. You also need a lot of flow if you're maintaining high RPM.

http://www.vwwatercooled.com.au/forums/images/imported/2008/11/P1320264-2.jpg

Pete

[GRN_VAGN]

I found a Facet wasn't keeping up with twin Dells.

I've just installed a 72gph Carter Rotary Vane pump which seems to be just right.

I'm told 6psi is the nominal pressure for the Dellorto/Webers. You also need a lot of flow if you're maintaining high RPM.

http://www.vwwatercooled.com.au/forums/images/imported/2008/11/P1320264-1.jpg

Pete

Old thread i know, But Pete
Im running the same pump as you pictured, and using a rekitted weber 32/36 weber.
Im getting over fuelling, as its super rich and wont drive.
Are you sure these pumps are right? im about to buy a Regulator and PSI gauge to be on the safe side, but i also have a return.
I guy i was chatting to last night while watching a mates Skyline on the dyno said that as soon as float bowl is full, needle and seat shut, the excess fuel will go back to tank via the return line. Sound right?

Just want to drive it :( ran ok on old carb, so i know its a tune problem now.