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Thread: Bridgeport dellorto settings
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dubber91
Newbie
Posts: 6
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posted July 08, 2007 02:33 AM |
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Bridgeport dellorto settings
Hi guys, new member here....
Ive got a huge bridgeport NA motor built around turbo II housings. I want to run a 48 dellorto on it: i current have 42mm chokes.
Has anyone got any baseline jet sizes to run this sort of motor? It seems to lean off quite a lot....
Cheers
Steve
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Klaus44
Redlining
Posts: 365
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posted July 08, 2007 10:31 AM |
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You'll want to...
...get in touch with Racing Beat, and see if you can talk to one of their seasoned, oldschool-knowledgeable experts about that, IMHO.
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repumax
Redlining
Posts: 427
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posted July 08, 2007 05:47 PM |
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Dellorto is way to small for a Bp. Best set up is a Weber 51mm or a Holley.
____________
1974 Mazda Repu
1986 Yamaha RZ 500
1988 Yamaha YSR 50
1991 Suzuki RGV 250
1992 Yamaha TZR 250 SP
1996 Aprilia RS 250
2003 Ford F-450 6.0 Diesel
2004 Mazda RX8
2006 Yamaha Banshee
2014 18' Eclipse Toy Hauler
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dubber91
Newbie
Posts: 6
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posted July 09, 2007 02:54 AM |
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But in terms of CFM the dellorto is the same (or there abouts) as an IDA. Ive always been wary of people telling me dellortos are too small....
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repu510
Hauling
Posts: 141
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posted July 09, 2007 08:24 AM |
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believe it or not, the dell doesn't flow enough for a BP. that is why you're experiencing the lean out. i'll re-iterate what klaus said. check w/ RB or Mazdatrix. they'll be able to help you select the right fuel system for your BP. one thing about rotaries, they really like to suck down the fuel. the reason why most guys blow their engines is due to running too lean. i've ruined 2 motors in the last 15 years because of that. just when you think you have enough fuel, you dont. but that's just from my experience.
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Klaus44
Redlining
Posts: 365
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posted July 09, 2007 09:58 AM |
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...and...
...then there's always the rest of your fuel delivery system to consider, and whether or not it's up to the needs of your chosen carb., and the hi-RPM demands of your motor.
From pick-up tube, to fuel pump, to pressure regulator, and even fuel filter(s), it all comes into play... especially when the pedal's to the metal!
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Brad
Rotorhead
Posts: 1672
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posted July 09, 2007 10:32 AM |
Edited By: Brad on 9 Jul 2007 10:33
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I have a dellorto 48 dhla on my 12a J-bridge
and it dyno'd 205 to the ground with 42mm chokes. And we still could have put larger fuel jets or smaller air jets to richen it more if needed but the air/fuel ratio was perfect when we were done. 2.25psi fuel pressure and a holley pump is all it needed.
it's using a lake cities intake manifold which totally changes the jetting so my jets won't work if you're using the typical wrap around intake manifolds.
I had to go way way way down on the air correctors; it eats a lotta fuel at high rpms especially at and after the motor is at PEAK volumetric effeciency (6000rpms).
now, with that said and done, the current trend is to put VERY LARGE 2bb carbs on ported rotaries which increases the air flow potential and you get every last hp possible.
56mm Gene Berg IDA copy with 48mm chokes for peripheral port 13b's, 54mm Gene Berg IDA copy with 38mm chokes street port 13b SCCA EP class.
____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge
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dubber91
Newbie
Posts: 6
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posted July 09, 2007 01:59 PM |
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thanks for the advice. My reasoning is that in simple terms, a 48mm tube flows the same regardless of orientation or manufacturers stamp. So long as the fuel jets supply the right amount of fuel then i cant see why a 48 dell wont work.
I think perhaps my fuel pump is not up to the task: it is a red top facet. I can only supply the carb with 3 PSi max before it spits past the needle and seat.
what jet sizes do you run? I guess they will be around thhe right size for me....
Steve
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Brad
Rotorhead
Posts: 1672
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posted July 09, 2007 03:49 PM |
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220 fuel and 160 air.
And, when I moved the carb from ontop of motor to next to motor with the little 4" long intake manifold, the motor needed significantly smaller main fuel jets.
one facet fuel pump is not enough, try a carter 6psi model and regulate it down to 2.25.
What jets are you using now and what are the air fuel ratios?
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dubber91
Newbie
Posts: 6
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posted July 10, 2007 01:44 AM |
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I am running 230 mains, 230 airs, and 75 idles if i recollect correctly. I am also running 7772.8 emulsion tubes. my AFRs are just a little close to 14.7 to be safe really. Starting around 14.5 it richens slightly, but then returns to around 14:1 at around 6000RPM. So i guess the mains are little small, and the air correctors a little big?
Cheers
Steve
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Brad
Rotorhead
Posts: 1672
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posted July 10, 2007 08:01 AM |
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richen it up
those jet #'s are for stock port motors.
Tune with fuel jets first. Put in bigger fuel jets which have the biggest affect at low to midrange, then finetune upper rpm range with air jets.
13.2 - 13.4 at WOT is what most people shoot for these days.
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dubber91
Newbie
Posts: 6
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posted July 10, 2007 08:58 AM |
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so what mains? i think ive just bought some 240s...... and 140 airs...
Steve
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Brad
Rotorhead
Posts: 1672
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posted July 10, 2007 02:15 PM |
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Can't give exact #'s since I've never run the dell on a bridgeport 13b with the U-shaped manifold.
I'd guess 240 or larger, perhaps even into 250 or 260.
Do you have an air/fuel meter in the truck or using one on the dyno?
Keep fattening up the main fuels until it's a nice constant 13.2-13.4 up through 5000rpms, then the airs really kick in.
____________
-brad-
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-
Bridge
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dubber91
Newbie
Posts: 6
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posted July 11, 2007 12:30 AM |
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Ok that sounds like a good place to start Ill go with the 240 mains and the 140 airs ive just bought and see what happens.....I think fuel pump might be an issue though...
Thanks very much for your help: ill get back to you with the results...
Steve
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