Turbo fueling issue.

[Garrick Clark]

Hi Guys.
I have a fueling issue on my turbo engine.
Its dual 40 dells.
225 fuel inlets on the carbs
72 psi pump going into a fuel reg that returns to the tank.
Got a steady 3 psi at idle.
fuel reg gets a signal from the carb hat.
SO, I start it up. let  it idle till oil is like 150, then go for a drive.
It will run good, for say 15 mins. boost comes on and pulls hard.
When I get on a dual carriage way it sort of seams like its running out of fuel. power drops off and I have to slow it down as the AFR gauge goes lean.
could it be the 225 inlets being too small, or is it a fuel pump/reg issue.
My fuel system is
a CB Tee outlet.
13mm hose to the pump, no pre filter as this caused cavitation, bosch pump. (72 psi max)
Fuel reg drops this down to 3 psi at idle. 8 mm hose to carbs and return to tank. vented fuel cap.
Has anyone used the biggest inlet needles that euro carb sell. there 400's.

[DWL_Puavo]

You could try to increase the fuel pressure to 4 psi, if the needle valves are good they should be able to handle that pressure just fine. It should increase your fuel flow to about the equivalent of 275 inlets. But your current setup should flow quite enough for fast speeds anyway - although not sure how much a monster your engine is.

Otherwise there shouldn't be that much problems with the fuel system - heat comes into mind but it's usually problem when the fuel is not constantly circulated and also usually with slower speeds as the fuel stays in carbs bowl longer (I had to google what is "dual carriageway" btw). Heat usually causes bad starting and idle after engine's been off after it's been hot, and bakelite's between carb and inlet manifold help that a lot.

Could you log somehow the fuel pressure? Maybe easiest with some kind of digital pressure sensor, but doable with gopro cam or maybe even with a bit of fuel hose extension and rear view mirror?

[Garrick Clark]

Hi DWL.
Thanks for the reply.
I was thinking about this last night. I have the fuel reg on top of the number 1 and 2 carb hat. the fuel gauge is on the end of the reg on  Tee pipe. It says 3 at that point. I'm wondering if its lower at the carbs. I will increase the pressure on the reg and see what happens.

A little test I could try is to block the return, block the pipes to the carb, change the fuel gauge to 0 -100 psi and see if in fact it pumps what its supposed to at max.
I do have the Bakelite's fitted.

[Fiatdude]

Do you have a return line or is the system dead headed at the carbs??

[Garrick Clark]

I have a return to tank.
It uses one of those CB Tee connecters on the end of the tank

[Fiatdude]

As I understand the issue -- When under boost it is running OK, but just cruising down the road it starts to lean out... Is this right?

[Garrick Clark]

Yeah that it. A  good run down a dual carriage way (high way) isn't going to happen as it just sort gives up like no fuel . AFR gauge wont show rich if I press the throttle to floor. In fact it gets worse. I have to be careful and back off quick as the boost is still rising.

[spoolin70]

Does it still go lean if you accelerate slowly without bringing in boost ?

Regarding the fuel regulator, is it known to be good ? I mean was it new in a box or at the bottom of some old parts ?

I used a Malpassi regulator before that got some moisture inside from the boost reference tube from the water/methanol injection kit I was using. The parts inside rusted really badly and it sent the pressure high - around 130psi.

Changed to a Fuelab regulator and re-routed the reference tube through a moisture collector and all was fine.

Thanks
Darren

[Erlend / bug66]

Does the regulator actually rise pressure with boost?

Chuck a gopro at the gauge and see if it rises.

I struggled with my EFI setup before I made a vacuum junction box, hade each runner fed to the junction (below throttle plates). That cured the issues

[Garrick Clark]

Hi Guys.
 Thanks for the ideas.
I did a dead head test tonight . pressure gauge went to 80 psi. It was slow to get there but it did it.
I bought the reg new.
Next step as mentioned above is a go pro camera or something similar.
I can get it to go lean without boost. It does it at the same throttle opening each time.
I have some modified .2 emulsion tubes fitted. Basically they are the same as in the CB turbo book that Lyle makes.
Thin at the bottom, fat at the top, no holes along the length of the tube, 1 hole above the fuel level in the well.
I think the ratio of the reg is 1.1