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 Posted: 01-09-2017 04:55 pm
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Esprit2

 

Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 289
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Bfitz241 wrote:
I believe my carbs are plain "45", but I'll check to be sure.All Dellorto DHLA models are arguably better than the corresponding Weber DCOEs, so a plain "45" isn't a lesser carb. The "45E" was developed for Lotus first, and then saw wider use. It has a number of detail differences that give it finer resolution for sneaking up on precise emissions settings. Things like 5 or 6 idle progression holes in a unique Lotus pattern, verses as few as two in some Weber DCOEs. And Idle Mixture screws with a finer thread and a longer, more finely tapered needle.

All the Lotus set-ups, like "Spec 5", are based upon the 45E model with it's finer resolution. If those set-ups are used in the 45, or other letter-suffix models, the results 'may' not be exactly the same. But the Lotus "Spec _" is still a better starting point for a non-E carb on a 907 than some generic formula or Des Hammill recommendation. Just expect that you may not get exactly the same results that someone else talks about getting without first doing a little tuning of your own.

For instance, a plain 45 with fewer/ larger idle progression holes than in a 45E 'may' require a slightly richer idle mixture to avoid hesitation. And the number of turns required to tune the Idle Mixture Screws will be less.

Details, and you may have to work out a few of them on your own. But once you have it tuned up, the 45 is still a great carb, and better than the comparable Weber DCOE.

Also keep in mind that Lotus had to meet European Emissions Standards, so the factory set-up is on the lean side. And it got progressively emissions-leaner from Spec 1 to 3 to 5 to 9. You can make any Spec 907 run better than stock if you tweak the jetting a bit richer than stock.

I have three 907s with 45Es, and I work on a number of local club member's Lotus & JH cars with DHLAs, including 910 Turbos. Then I have one Europa S2 with a single Weber DCOE 45. That one DCOE causes me more constant fiddling to keep it in tune than all the other DHLAs I work on, combined.

Love your Dellortos, they're great carbs. It's just that if you aren't running 45Es, or if you want better than factory emissions lean, you may have to make a few creative adjustments from the Lotus or JH spec to dial them in.

Regards,
Tim Engel

Last edited on 01-10-2017 01:57 am by Esprit2