My draw through turbo

[buguy]

I don't know crap about those carbs, but in others, it's critical to make sure you don't have the butterflies open too far at idle making it start in the transition from idles to mains on idle. Anything like that on those?
In the past I've had to drill holes in the butterflies to increase idle speed so I could lower the idle screw making the butterflies close more at idle.

[GARRICK.CLARK1]

That's very true. I did that with mine. My butterflies are totally closed off, its the 2mm hole in each butterfly that make it idle at 1000 rpm.

[advinnie]

My butterflys are nit fully closed but they are not uncovering any of the progression holes

[madmike]

I think I ended up with a 3.00 needle & seat inlet for the float on my DCOE

[advinnie]

Cheers madmike.
Can we talk about emulsion tubes?
Has anyone played with the F11 and F8 tubes and what difference did it make?

[advinnie]

At last, at bloody last I've all most got the A/F ratio right but I have found a small problem.
I've not sat at motorway speeds for a long time now due to many issues the car has had. Anyway today all issues were addressed so of I went, 1/4 throttle acceleration was great, tip in was GREAT, WOT was amazing, crusing under 3000rpm In 4th was a little rich but at 65mph/3100rpm cruise A/f ratio was in the 12's so not great but better than the 10's I was in.
So accelerated up to 100mph a few time at 8psi boost without any issues and maintained a constant 65 mph for a few miles not a problem then the road cleared so in red speed to high 80's mph for around a minute or two then noticed the A/f ratio was getting leaner and leaner a quite a quick rate then Ithe gauge hit around 18:1 ish and it felt like the ignition was turning of then on the off again.
I was unable to accelerate or maintain the current speed so dropped the speed down to 70 mph which massively improved the situation, at this point the dam ratio gauge turned off so I don't know what was going on with the fuel ratios. Dropped down to 60 mph for half a mile and everything sorted its self out went back up to 80 mph and one again after just a minute or two the problem came back. This Time I shut the engine and fuel pump down and pulled over and I could not believe it the fuel bowl was f#@king empty. But the carb top back on turned on the fuel pump and watched the fuel bowl fill, fuel pressure was still at 3psi, the floats seemed free to move so everything was working as it sort. Now this leaves just one thing and that is at 80 mph and higher the engines fuel demand is greater than the replenishment rate is.
What do you think?
I'm using a 250 needle and valve.
So in a nut shell, I can accelerate hard up to 100 mph over and over again as long as I come of the throttle and allow the car to slow down which idms giving the carb time to fill again.
Can sit at 60 all day long.
Can only sit at 80 mph for a limit time untill the fuel bowl emptys

[GARRICK.CLARK1]

bigger fuel line if not already.
Bigger fuel outlet under tank if not already.
Cross drill the carb fuel inlet needle, don't over do it.
If you have a removable fuel inlet banjo on the carb top remove that and enlarge the fuel passage that leads to the fuel inlet needle/seat. don't over do it.
Increase fuel pressure to just below were the fuel inlet needle starts to leak
make sure you have a fuel tank vent. If you do make it bigger.

[buguy]

Those have a pretty small bowl. I think I've read about people starving their engines with them before. That was probably the biggest reasons I went with a Holley. That and the availability of parts.

[madmike]

x2 on what He said I did all them mods Garrick said and still run out of fuel on my 2276 ,, works good on my trail Buggy w/1915c, but i'm not cruising @ 80mph with that thing

[GARRICK.CLARK1]

Maybe try a an adjustable fuel pressure regulator with the boost signal taken from the wastegate actuator. Not usually a draw through thing but could be made to work. Fuel pump replacement might be needed also.

[Chip Birks]

Maybe try a an adjustable fuel pressure regulator with the boost signal taken from the wastegate actuator. Not usually a draw through thing but could be made to work. Fuel pump replacement might be needed also.

This is absolutely a side draft draw through thing.

[advinnie]

Right some back ground first.
I have a holly blue fuel pump which runs at a constant 14psi. Then I all ready have a boost sensitive fuel pressure regulator which is set to give me 3psi of boost and raise 1psi per 1 psi boost. I've now enlarged everything like garrick. clark1 said to do. I've even enlarged the fuel tank vent and no joy.
Now I pulled of 12 yes 12 0-100 mph runs one after another at 8psi boost and now problems, then I had an idea how many 0-100 mph runs can I do at zero boost the answer is 2 yep just 2. When I started the Thrid run she coughed so shut down straight away and the fuel boel was empty. Next experiment was to find out at which boost level she would run with out fault and that would tell me what fuel pressure she needed to stay fall of fuel. The answer to that was 5psi which meant the fuel pressure was at 8psi. So set the fuel pressure to 8 psi turn off the boost and went for a drive.
8psi allowed me to sit at 90mph for a long time so did 7psi for fuel pressure but at 6 psi fuel pressure I very quickly started to run dry on fuel at only 85 mph. 5 psi of fuel pressure allowed me to maintain a constant 65 mph no problem, at a constant 70mph I could see on the gauge she started to run lean.
So long story short I needed 6 psi fuel pressure min to keep the fuel bowl filled. Unfortunately the problem is at 7 psi at idle I could see fuel uncontrollable dripping out the carb. This was using a 250 neddle valve

[Dan Dryden]

The problem isn’t fuel pressure, it’s volume. Increasing pressure is just a way of masking the issue. It doesn’t work though because it is too much for the carb to handle and starts leaking. What size fuel lines are you running? The very minimum should be 8mm.

[advinnie]

I'm now running 8mm feed line and the return is bigger but can't remember what size I'm afraid.

[rubenski]

Would'nt you want your feed bigger than your return?

I know efi need uprated feed line but can return trough stock line in the tunnel... at least I know some guys do!