How much torque does an A7 engine produce

[Steve Jones]

In August, my Ulster engine measured a maximum 37lbf.ft at 3025rpm dropping back to 32 at 5100rpm. I've recently heard of a blown engine that's just measured 56lbf.ft at 3000rpm.

Steve

[Stuart Giles]

If anyone fancies doing a bit of maths to find either the horsepower or torque of their motor, these are the formulas.

Torque  =  5252 x Horsepower 
                  -------------------------
                            RPM   

Horsepower =  Torque x RPM
                        ------------------
                             5252

The most powerful seven motor I had on a rolling road dyno was developing 40 ft/lb at 6000 revs, I don't remember the maximum torque, but I'm not sure it approached the 56 ft lb maximum figure Steve quoted even though it was running 8lb boost.

[Reckless Rat]

Speed determines how far past the apex of a bend you go before you leave the road
Torque determines how much of the wall you demolish
Momentum determines how far into the field you go before you eventually stop.

Anecdotally, of course.

[Howard Wright]

Hi Reckers

Just to add

Oversteer is when you go through the hedge backwards!

Understeer is when you go through forwards!

Cheers

Howard

[David Stepney]

If anyone fancies doing a bit of maths to find either the horsepower or torque of their motor, these are the formulas.

Torque  =  5252 x Horsepower 
                  -------------------------
                            RPM   

Horsepower =  Torque x RPM
                        ------------------
                             5252

The most powerful seven motor I had on a rolling road dyno was developing 40 ft/lb at 6000 revs, I don't remember the maximum torque, but I'm not sure it approached the 56 ft lb maximum figure Steve quoted even though it was running 8lb boost.

Where does the constant 5252 come from?

[A G Wood]

The constant 5252 arrives from the cancelling out of various other constants in the fundamental equations Stuart. There are several You Tube vids and Reddit posts on the subject which explain it in far more detail than some one with chronic Mathematics PTSD like myself can

[Colin Morgan]

Looking it up, when working in what my old physics teacher used to call 'Christian units', the 5252 figure in the conversion is the

the number of ft.lb f/min in a Horsepower (33,000) divided by 2 x Pi (6.2832...), because total distance travelled is needed for

power (force x distance /time), but only the radius for torque (force x radius).

[Stuart Giles]

Torque is just the horsepower with the rotational (work done) element removed. So 2 Pi radians in a full rotation of a shaft =6.284 then dividing this by 60 gives us Radians per second. =0.10472 a horsepower is 33000 ftlb per minute, but we need the work done per second figure, so 33000 divided by 60 =550 now divide this figure by the 0.10472 radians/second value above gives us the constant of 5252 and we have removed the rotational element

Some of that stuff I did at college has stuck.

[Reckless Rat]

A absque coram de
Palam clam cum ex and e
Sine tenus pro and prae
Govern the ablativé

Latin grammar. I have an uncanny capacity for remembering shyte.

[John Cornforth]

I thought it might be of interest to look at the other end of the scale, one of the earliest Austin Seven engines. This is a section from Encyclopaedia Britannica 14th edition Volume XII, Part 1 (1929):

Small Motor Car Engines
The "Baby Austin" Engine.—The performance of the modern tiny motors typified by recent Austin and Singer designs is so remarkable as to merit special notice. A section of a seven H.P. Austin small-car engine is given in fig. 15. The four en bloc cylinders of 2.2 in. bore and 3.0 in. stroke (see table) are fitted with a detachable head. The pistons are of aluminium alloy. The side-by-side valves are cam-operated in the usual manner. Lubrication is by a drowned oil-pump driven from the camshaft as indicated, and ignition is by H.T. magneto. Thermosyphon cooling with a "film" radiator and fan. The four-throw crankshaft is borne in two roller bearings. The mixture is supplied by a Zenith carburettor. The power output is: At Rev. per min. 1000, 1500, 2000, 2500, 2800 B.H.P: 3.8, 6.2, 8.7, 11.0, 12.0 (max.) This miniature engine propels its car containing three or four adults with ease at 35 miles per hour on an ordinary good road surface, with a petrol consumption of 40-50 miles per gallon.

Taking these BHP figures and calculating torque we get:

1000 RPM 20.0 lbs ft
1500 RPM 21.7 lbs ft
2000 RPM 22.8 lbs ft
2500 RPM 23.1 lbs ft (maximum torque)
2800 RPM 22.5 lbs ft