Dellorto Jettings

[judson]

I've got a wicked flat-spot in the 910 I put in my Jensen-Healey. I think I'm running the idle jets too rich, but I'm not sure...

Does anyone have a list of suggested (or stock) carb jets (either Weber of Dellorto)for the Naturally Aspirated Esprit 2.2?

As every application is different, I will have to fine-tune my engine, but it would be nice to see what other people have used.

Thanks in advance!

[Esprit2]

judson said:

I've got a wicked flat-spot in the 910 I put in my Jensen-Healey. I think I'm running the idle jets too rich, but I'm not sure... Does anyone have a list of suggested (or stock) carb jets (either Weber of Dellorto)for the Naturally Aspirated Esprit 2.2?

Judson,
Do you mean 912? The 910 is the 2.2 turbo engine. If you built a N/A engine from a 910 core, then is it a hotrod or does it mimic a Lotus spec engine? Carbs/ cam/ compression all play together. If you have strayed significantly from Lotus-stock cams and compression, then the Lotus carb specs will have to be tweaked as well.

When does the flat spot occur? What carbs and jetting are installed now?

Listed below are the Lotus OEM carb jetting specs for the 912 N/A engines. Such charts usually get "realigned" when posted on this forum, but you should still be able to read it okay. Contact me offline if you want it in MS-Word. I have a Word.doc that gives similar data for all the Lotus specs for the 907/ 910/ 912 engines... along with some notes and opinions on tuning them.


Lotus Spec 9
About right for a mildly warmed up 2.2 liter.
9.5:1 or 10:1 compression, up to 104 cams, headers.
Carb Type ....................... DHLA 45E
Choke .............................. 37 mm
Main Jet .......................... 160
Main Air Corrector Jet ... 230
Main Emulsion Tube ...... 7772-8
Idle Jet ............................. 55 (a little lean, try up to 58)
Idle Jet Holder ................. 7850-9
Float Weight .................... 8.5 gr
Float Setting Height ........ 14.5 - 15.0 mm
Float Needle Valve ......... 170
Pump Jet .......................... 50H
Starter Jet ......................... 95
Starter Emulsion Tube ..... 7482-3
Power Jet .......................... ---
Slow Running Speed ....... 900 - 1000 rpm
Idle CO Level (hot) ........... 0.7 - 1.5%


Lotus Spec 10
10.9:1 or 11:1 compression, 104 or DS2 cams, 2.2 liter.
Carb Type ....................... DHLA 45E
Choke .............................. 37 mm
Main Jet ........................... 135
Main Air Corrector Jet ... 150
Main Emulsion Tube ...... 7772-8
Idle Jet ............................. 56 (little lean, try up to 58)
Idle Jet Holder ................. 7850-9
Float Weight .................... 8.5 gr
Float Setting Height ........ 14.5 - 15.0 mm
Float Needle Valve ......... 170
Pump Jet .......................... 45H
Starter Jet ......................... 80
Starter Emulsion Tube ..... 7482-3
Power Jet .......................... 70
Slow Running Speed ....... 900 - 1000 rpm
Idle CO Level (hot) ........... 0.5 - 1.5%


Esprit NA, 1988 Onward
Tag Number
Front ................................ 5395A
Rear ................................ 5394P
Lotus Part Number
Front ............................. A912E2336F
Rear ............................. A912E2337F
Carb Type ....................... DHLA 45D
Choke .............................. 37 mm
Main Jet ........................... 135
Main Air Corrector Jet ... 150
Main Emulsion Tube ...... 7772-8
Idle Jet ............................. 56 (a little lean, try up to 58)
Idle Jet Holder ................. 7850-9
Float Weight .................... 8.5 gr
Float Setting Height ........ 14.5 - 15.0 mm
Float Needle Valve ......... 170
Pump Jet .......................... 45H
Starter Jet ......................... 80
Starter Emulsion Tube ..... 7482-3
Power Jet .......................... 70
Slow Running Speed ....... 900 - 1000 rpm
Idle CO Level (hot) ........... 0.5 - 1.5%
Pump Delivery .................. 8cc / 20 strokes
Pump Lever Clearance ..... 0.1 +/- 0.05 mm
Fuel Delivery Pressure ..... 4.0 +/- 0.25 psi

Good luck,
Tim Engel
Lotus Owners Oftha North
Minnesota, USA


>> Edited by Esprit2 on Wednesday 1st December 17:43

[rlearp]

Hey Tim,

I would love to have that Word document for my 907 work. I'm getting ready to bolt some carb onto mine here soon and fire it up, some advance reading would be nice. My email is [e-mail]. Thanks!!!!

Ron

[judson]

Tim,
thanks a million...exactly what I need...a starting point for my custom 907/910/912 whatchamacallit engine.

Judson