What is the Best air fuel mixture for Power and economy Mine runs at 13 pouds of air to 1 pound of fuel on all rev ranges up to 5000.

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A Bloody Mini

1970 Mini K, 1380cc, 1.75 HIF SU, 30 70 Cam, 2" Zorts
1969 Mini K, Stock Standard and Orginal. (Slow as Hell)

I've heard it's about 13.8:1 Air Fuel ratio for a mildly tuned motor. So it sounds like your in the ball park.

Most efficient Fuel:Air ratio is 1:15(+/- 0.1). Always has been, always will be. Most economic Rev range for a piston engine is between 2100 and 2400 RPM.
The major improvement in fuel economy in modern cars is the constant monitoring keeping the mixture at the optimum ratio.

Edit...... Those figures are universal for reciprocating piston engines running pump petrol.

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"He's always been a dickhead, He always is a dickhead, He will always be a dickhead. So stop complaining when he acts like one."

Phil you are right in theory, but..
Vizard suggests (p118, HTMYM) that for maximum power a Mini engine likes to be 12.5-13.0:1 f/a ratio. I agree this is pretty rich- but whaddaya want- power or economy?

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

we want both.. don't MAKE me stamp my feet and hold my breath....!!!

And these ratios are achieved by needle selection?

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You're only supposed to blow WHAT off?

I think with a bit (lots!) of needle experimentation you can get it a little rich at full throttle for power, and still have a lean cruise. But there are limitations- too lean and it'll have flat spots.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

as I said, the most EFFICIENT for power versus economy is 1:15. Running slightly rich is a good safety measure for when you accelerate hard.

Since SU's dont have an accelerator pump of any form, until the piston steadies itself into cruise condition again, it will be running lean. That means every time you put your foot down.

Piston engined aircraft have a mixture lever, which allows adjustment for different times. Full rich is used for takeoff and landing, but it can be leaned out for cruise at altitude, espcially since less fuel is required when higher up. For that reason they all have an Exhaust Gas Temperature gauge.

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"He's always been a dickhead, He always is a dickhead, He will always be a dickhead. So stop complaining when he acts like one."

Thanks Guys.

Silly me i should have look in My vizard book first I will look next Time.

_________________
I've Got One
You've Got One
We've All Got One
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A Bloody Mini

1970 Mini K, 1380cc, 1.75 HIF SU, 30 70 Cam, 2" Zorts
1969 Mini K, Stock Standard and Orginal. (Slow as Hell)