Lotus Elan

Morgan Carb Tune versis Synchrometer

PostPost by: William2 » Sun Dec 24, 2017 12:40 pm

I am slightly confused over the merits of these two tuning devices.
I currently have successfully used a Synchrometer to balance my Dellorto 40 carbs but was thinking of investing in a Morgan Carb Tune manometer after Christmas.
I realise that one advantage of the manometer method is that you don't have to remove the airbox cover. The main question I have is, am I correct in saying that you also have the advantage of being able to adjust the idle mixture so that the manometer levels are as high as possible as well as balancing the airflow of both carbs. Whereas the Synchrometer is only monitoring the trumpet airflow and thus is only concerned with adjustment of the throttle slow running.
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PostPost by: richardcox_lotus » Sun Dec 24, 2017 3:02 pm

I think that?s the main benefit. As the vacuum takeoffs are the inlet side of the butterflies, you?re recording what the engine is seeing at all points of the throttle plate positions.
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PostPost by: bill308 » Sun Dec 24, 2017 3:03 pm

Hi William2,

I use a pair of 4-bank mercury manometers in lieu a BK Synchrometer on my carb 308. I'm curious as to how well the Morgan Carb Tuner works. Seems it should work as well and no mercury. I like the idea of Stainless slugs floating on air, in tapered tubes.

Idle mixture is best set using a Color Tune or having gas sampling ports on each exhaust branch like cab 308's due. There needs to be a way of evaluating the mixture in each cylinder an each cylinder's mixture is set separately, The other thing a Color Tune will do for you is let you see what is or is not happening during throttle blips. Is the mixture going rich during acceleration and leaning out at steady state?

Gas sampling using a wide band O2 instrument like the Innovate products allow proper data logging of over the road mixture. With rpm and manifold vacuum signals, one can correlate driving condition with mixture. Typically, data snapshots are taken about 10 samples/second on the bulk exhaust. After the idle mixture settings are equalized and appropriately set, the collective mixture signal, sensed at or after the collectors, is sufficient to dial in jets, air correctors and emulsion tubes.

I believe a Synchrometer can give you an air flow reading, but can only see one barrel at a time, whereas a Carb Tune will give you a simultaneous vacuum comparison of 4-barrels, hands free, throughout the rev range. It's especially good at looking at transients, or short duration throttle changes, Balance is most important at low throttle openings where a small increase in throttle opening makes a big difference in air flow and idle mixture is critical. Five degrees of throttle angle change at 1000 rpm makes a big difference in rpm while the same deflection at 3000 rpm makes little difference. You notice carb balance and the resulting drivability change when engaging the clutch and during initial acceleration. This whole dance is much smoother when the balance is good.

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PostPost by: john.p.clegg » Sun Dec 24, 2017 3:23 pm

Wouldn't be without mine...

2017_0714dellorto0007.jpg and



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PostPost by: alan.barker » Tue Dec 26, 2017 8:05 am

+1 Carbtune 100%
Alan.b Brittany 1972 elan sprint fhc Lagoon Blue 0460E
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