Jetting the dellorto for blow through....
 

Anyone who has purchased or had their 48 mm Dellorto turbo prepped, do you know what jets you are running?


I am running a DHLA 48 sidedraft Dellorto in my blowthrough setup. I have been trying to figure out a good jetting setup to shoot for to bring the carb into tune, but I don't want to start diving into it until I have an idea of what to go for. The car runs good at idle (which is at about 1100 rpm's). It's high, I know, but I also have a locked dizzy, and it's the lowest I can set the idle so that the car doesn't misfire every few seconds.

The problem I have is in the progression from idle to about 3500 rpms. Granted, I am running a big turbo, so it won't really hit full boost (10 lbs) until about then, but I don't think that is why it is like that. In my research on turbo prepping this carb, I found a vw book that talks about using modulator rings to enrichen the mixture under boost. So I made some out of aluminum, and put them on. They work great, as without them, the mixture goes much too lean when the boost comes up. Unfortunately, now from idle to about 3500 as I specified, it goes extremely rich, then when it get's to the specified rpm, my mixture goes into the thirteens...

I plan to take the modulator rings off if I can find a jetting setup that I am confident with, as I know Robert from Rotaryshack does not use them, and he def has way more experience with this stuff than I do, but I hope someone out there can help me... :)

Robert at rotaryshack is who you need to talk to.

If you need to boost above 10psi, you need to machine the carb so it can be sealed for turbo application. For the costs, buy a weber instead as it comes pre-sealed.

Got ahold of Robert from rotaryshack, and I have to give him kudos. I personally have never bought anything from him, and he was super helpful, he wasn't trying to rush me off the phone or anything... I found out that my turbo is too big. This naturally was a huge dissappointment for the budget "tuner" that I am trying to be, but at least now I know what the plan now is. Going to just try to get it close to finish out the driving season, then send out the carb to rotaryshack during the snow, while keeping my eyes out for a smaller turbo (60mm or smaller). I'd really like to upgrade to water cooled.... :)

Thanks to everyone for the help!

Dude sounds like to me you have a bad boost leak... I had the same problem the car would idle rich but as soon as I hit boost it ran lean... Check around the carb hat. And all your couplers..
I put a gasket around the carb hat and bam it solved my problem... Hopefuly it works for u

Do some research why Maserati and Lotus used these carbs on the blow through aps they offered. The dhla needs no boost prep at all. In fact turbo emulsion tubes are offered from the factory.

Suggest you poke around on Lotus Bi turbo Blow through setups.

wow why was this bumped from the dead?

Oh well my info still stands for future use.

e tubes from the DRLA will fit the DHLA