Triple Weber DCOEs
- Thread starter Matthew68
- Start date
In 1979 to 1984, Lotus and also Alfa Romeo's AutoDelta made Dell Orto equiped Independent runner side draft carb cars with 7:1 compression ratio, 9 psi boost turbos. Based on the twin cam 16 valve Lotus or 8 valve DOHC Alfa engines
Stock 1974 or 2174 cc Esprits were either 155 to 160 hp on 9.5:1 compression with DHLA 45's and various choke sizes, but normaly 37 mm chokes, with any one of about five different E tubes. Rpms at peak power were 6000 for the 1974 cc, and a little less with the 2174 cc.
When turboed, the carb size was kept the same, and just the emulsion tubes retrimmed. Hp when up to 230 to 265 hp, depending on the model. Still at about 6000 rpm. 44% to 71% increase in power, with no increase if carb venturi size.
Key thing is the carbs were not upsized, so if you want to use a less than huge Weber or DellOrto, then you can go turbocharged if you keep the turbo away from the carbs.
Specfic interest is the Alfa Romeo GTV 2000. Only being 8 valve per cylinder, they were about 35 to 40 hp down on the same sized Lotus engines
The 1962 Alfa DOHC, with the exception of the one year only US SPICA MFI,
it always used the 32 mm choke DHLA 40 carbs in European tune, and when AutoDelta turbocharged, the 120 hp at 5500 rpm 1962 cc engine went to 168 hp at 5500 rpm and 174 lb-ft at 3500 rpm with about 9 pounds of boost.
jetting and calibration was the "19116" Dellorto DHLA40H for the 168Hp to 175 PS Alfa Romeo Alfetta GTV Turbo ...
32mm Chokes
7848.2 Auxillary venturi,
140 Main jets;
7772.14 Emulsion tubes;
230 Air correctors;
62 Idle jets;
35 Pump jet;
150 Needle valves.
The stock non turbo 120 hp
For the standard Dell'Orto 40DHLA as fitted to the stock 'Euro' 2000cc engine, the following setting apply -
Choke size 32
Main jet 135
Air corrector jet 200
Idle jet 50
Pump jet 33
Emulsion tube 7772.10
Choke jet 70
Float needle 1.5
The non intercooled install was very neat. The internal changes were compression and liner to head gasket related, and the 1975 to 1987 competion sucess of the Alfetta/GTV based cars was expetional.
If any of you are stuck with sub optimal choke sizes that strangle the power peak downwards to 3500, 4000, 4500 or 5000 rpm, just take the leaf out of Lotus and Alfas book.
add a turbo
The issue is that some of us want to use DCOE 40'S OR 42'S with smaller chokes, so in thoise cases, you stuck with 32 mm chokes. On a 200 cube engine, the peak power rpm is down around 4500 rpm. Add a turbo, and you can keep the small size chokes, and get a 44% power boost without moving your peak power rpm upwards at all.
So a triple DCOE 40 or 42 engine with 180 hp at 4500 rpm 3.3 liter engine with 32 mm chokes would move into 260 hp to maybee 290 hp at 4500 rpm pretty easily with just a small T03 60 series turbo at 9 pounds boost. Your c/r would have to suit the application, but its possible to run 10.5:1 with boost modulated control of the turbo, as long as you have the right kind of MegaJolt/EDIS waste spark ingition ramps.
Stock 1974 or 2174 cc Esprits were either 155 to 160 hp on 9.5:1 compression with DHLA 45's and various choke sizes, but normaly 37 mm chokes, with any one of about five different E tubes. Rpms at peak power were 6000 for the 1974 cc, and a little less with the 2174 cc.
When turboed, the carb size was kept the same, and just the emulsion tubes retrimmed. Hp when up to 230 to 265 hp, depending on the model. Still at about 6000 rpm. 44% to 71% increase in power, with no increase if carb venturi size.
Key thing is the carbs were not upsized, so if you want to use a less than huge Weber or DellOrto, then you can go turbocharged if you keep the turbo away from the carbs.
Specfic interest is the Alfa Romeo GTV 2000. Only being 8 valve per cylinder, they were about 35 to 40 hp down on the same sized Lotus engines
The 1962 Alfa DOHC, with the exception of the one year only US SPICA MFI,
it always used the 32 mm choke DHLA 40 carbs in European tune, and when AutoDelta turbocharged, the 120 hp at 5500 rpm 1962 cc engine went to 168 hp at 5500 rpm and 174 lb-ft at 3500 rpm with about 9 pounds of boost.
jetting and calibration was the "19116" Dellorto DHLA40H for the 168Hp to 175 PS Alfa Romeo Alfetta GTV Turbo ...
32mm Chokes
7848.2 Auxillary venturi,
140 Main jets;
7772.14 Emulsion tubes;
230 Air correctors;
62 Idle jets;
35 Pump jet;
150 Needle valves.
The stock non turbo 120 hp
For the standard Dell'Orto 40DHLA as fitted to the stock 'Euro' 2000cc engine, the following setting apply -
Choke size 32
Main jet 135
Air corrector jet 200
Idle jet 50
Pump jet 33
Emulsion tube 7772.10
Choke jet 70
Float needle 1.5
The non intercooled install was very neat. The internal changes were compression and liner to head gasket related, and the 1975 to 1987 competion sucess of the Alfetta/GTV based cars was expetional.
If any of you are stuck with sub optimal choke sizes that strangle the power peak downwards to 3500, 4000, 4500 or 5000 rpm, just take the leaf out of Lotus and Alfas book.
add a turbo
The issue is that some of us want to use DCOE 40'S OR 42'S with smaller chokes, so in thoise cases, you stuck with 32 mm chokes. On a 200 cube engine, the peak power rpm is down around 4500 rpm. Add a turbo, and you can keep the small size chokes, and get a 44% power boost without moving your peak power rpm upwards at all.
So a triple DCOE 40 or 42 engine with 180 hp at 4500 rpm 3.3 liter engine with 32 mm chokes would move into 260 hp to maybee 290 hp at 4500 rpm pretty easily with just a small T03 60 series turbo at 9 pounds boost. Your c/r would have to suit the application, but its possible to run 10.5:1 with boost modulated control of the turbo, as long as you have the right kind of MegaJolt/EDIS waste spark ingition ramps.