Turbo dells.

[GARRICK.CLARK1]

Guys. Thinking of re fitting my 40 dells.
1 issue I had was I could set the idle mixture with the hats not fitted. Basically N/A MODE. Then with the hats fitted and the plumbing to the turbo IT would choke up. Is this the same effect as being at high altitude . NO AIR. How you get round this. Is it enlarge the air jets.

[madmike]

weird ? do you have a clogged air filter on the turbo?

[GARRICK.CLARK1]

Hi Mike. No clogged filter. Its like the air flow to the carbs gets restricted.

[GARRICK.CLARK1]

Help.
I'm trying to run N/A with my dell 40's ,I have it running down the street quite good. Why N/A. Well the turbo oil seals have blown so N/A for a while.
The PLX AFR gauge is confusing me.
When i'm steady cruising the gauge shows 13.2,
I put my foot down and the gauge goes leaner than 13,like 13/14/15 etc
I take my foot off the throttle and the gauge numbers drop to 10.

Shouldn't the gauge at cruise be say 13, then with foot down go rich to say 10

Then with foot off throttle shouldnt it show lean an hell , (no throttle no fuel).

[madmike]

My Innovate gauge is so 'touchy' it show's lean for a slit second when I crack the throttle , you think it's this way with your's?

[66brm]

Foot off throttle at high rpm give you maximum manifold vacuum, drawing fuel through but not enough air to fire. The opposite happens when you quickly open the throttle, heaps of air in but it takes a bit for the fuel to get moving

[GARRICK.CLARK1]

Mike and 66. I'll have to do some more driving.
Brm66 . The foot off throttle at high revs giving max vacuum is making sense. I did notice on over run it was cracking/popping out the exhaust. So that will be the vac drawing on the mixture screw and half of the 1st progression hole. Yes.
I have backed off the plates VERTUALLY all the way and drilled a hole in each plate to achieve a 1 k idle. I now have only HALF of the 1st progression hole beneath the plate

[GARRICK.CLARK1]

So if the vac on over run is drawing on the mixture screw and the 1st progression hole and with butterfly's almost closed the 10 on the gauge cant be fixed. I can live with this now I know what's going on. Wonder if I can close the butterfly's some more and have no progression hole in the vac signal part of the manifold. That would help wouldn't it. I have read that the idle fuel is coming from the mixture screws so closing blades off should be a good idea.

[buguy]

So you would close the throttle more and maybe drill a bigger hole in the throttle blade to increase idle speed?

[GARRICK.CLARK1]

Yes.That's my next thing to do. Close the plates completely and drill the butterfly hole's a bit bigger than they are now so I can still get 1 k rev at idle. I think the holes in the butterfly plates are on the same side as the progression holes in the carb. I'm wondering if these holes should be on the opposite side of the butterfly plates. (THE NONE PROGRESSION HOLE SIDE OF THE CARB). Would the vac from the engine suck through the holes in the plates and drag some fuel out of the progression holes and draw it through the plate holes.
OR instead of drilling holes bigger, MAYBE increase the idle timing to 15 from 10 to increase idle speed.

SIDE NOTE. I see the only place fuel should get to the engine AT idle is from the mixture screw holes.
THEN. The initial first rev of the engine the fuel comes from a total of three places.
The mixture screw holes.
The progression holes in the side of the carb, Depending on the butterfly angle.
The pump jets.
No wonder They can get too rich down low.

[turbobaja]

Do your Dell carb(s) have an idle air bypass screw for each bore? What kind of Dell carb are you working with? If you've got the air bypass screws, open them up instead of drilling holes in the throttle blades to achieve your desired idle rpm w/out opening up into the progression ports. If you're fueling off the progression holes with the blade at it's stop, you'll have a really hard time tuning your idle. Part throttle driving is fueled purely through the idle fuel/air jets and the progression ports provide the path for that air/fuel mixture into the bore. Get those blades below the progression ports at an idle and enjoy adjusting the idle with the volume screw as designed. Part throttle tuning is done with idle jet changes and can be a little leaner than stoich w/out problems due to nearly no load on the engine. Once you tip into the throttle past the progression ports, they'll lose signal (vacuum) to those ports as well as the idle volume screw and you'll be fueling only off the Mains. Open up the main Air jet to bring the mains in sooner if you've got a lean dropout between the idles and mains. Venturi sizing makes a large difference too with the strength of the signal (vacuum) to ALL of the jets.

[GARRICK.CLARK1]

Little update. I have it running correct N/A now. So onto refitting the turbo pipe work.
The only 2 things I've changed from n/a is refitted the hats and fitted the mod rings. I'm expecting it to be RICH at idle now with the hats fitted as the only air supply is through the 2" hole on each hat, This is of course without the turbo out pipe connected to each hat. I may have to go smaller on the idle jets.
The turbo does push a bit of air out AT IDLE, so this extra bit of air being blown into the hats at idle might correct it.

[GARRICK.CLARK1]

Got it running good at 1 bar
55 idle
140 main
36mm vents
33 pump jets
Turbo E tubes
32 MM CB mod rings . I Guarantee you need these. Either CB ones or home made.
190 Air jet.
Lower than standard float level.
Enlarged float bowl vent.

[madmike]

awesome

[GARRICK.CLARK1]

Thanks Mike. There is more to it and I will post up more if peeps are going through it.