Sound of Merlin vs Packard.

[Viking]

I read somewhere in my Spitfire books that the firing order was altered in the Packard built Merlin’s to reduce crankshaft resonance ( darn if I can find the pages again!). As far as I can recall the Merlin’s and Packard’s where almost identical technically, except for this, so the question is did this alter the sound of the engine?

Anyone have soundtracks?

Regards
Viking

[Bearcat]

Never heard that.. good question..

[kristorf]

No sound track but it always gets me the differance between a Spit/Hurricane/Lanc engine and a P51's sound when they fly around at Duxford.

The Brit Merlins are smooth and relativily quiet, where as the Mustang has a 'popping' sound more akin to a Formula 1 car with traction control on full tilt.

Both sound awesome though and get the hairs on the neck standing up.

[BadAim]

Originally Posted by kristorf

No sound track but it always gets me the differance between a Spit/Hurricane/Lanc engine and a P51's sound when they fly around at Duxford.

The Brit Merlins are smooth and relativily quiet, where as the Mustang has a 'popping' sound more akin to a Formula 1 car with traction control on full tilt.

Both sound awesome though and get the hairs on the neck standing up.

I would expect that to be more the result of the exhaust layout than anything, and of course the packard probably has a Crane Fireball cam in it --- us yanks can never leave well enough alone

[BrassEm]

Originally Posted by kristorf

Both sound awesome though and get the hairs on the neck standing up.

Amen to that! Thank god we've dedicted people who can make these classics still fly.
~s

[mauld]

TRY THIS FORUM IT HAS QUITE AFEW SPIT EXPERTS
http://forum.keypublishing.co.uk/for...daysprune=&f=4

[Viking]

Thank you for the link (and the video link!) I think that I might have been wrong (still searching trough my books) but I believe this site might cast some light on this topic! http://users.bigpond.net.au/Shackleton/rolls.html It appears that I have mistaken the Griffon for the Packard! Bad me!

“However, the firing order was different from the Merlin. A 60 degree V-12 with a 120 crank and paired throws has a number of permutations on ideal firing order, no one being superior to another provided the intake system is "tuned" for the firing order chosen. However, the exhaust note will vary. This gave the Griffon its classic "Griffon Growl" exhaust sound, not as sweet as the Merlin but still impressive!! Different valve timing contributed to the difference in exhaust note.” Etc.

viking

[Al Schlageter]

Allison V-1710

Firing Order
RH turning: 1L-2R-5L-4R-3L-1R-6L-5R-2L-3R-4L-6R
LH turning: 1L-6R-5L-2R-3L-4R-6L-1R-2L-5R-4L-3R

Timing Ignition:
Intake fires 28° BTDC, Exhaust 34° BTDC, Sparkplug gap = 0.012-0.015"
Intake: Valve opens 48° BTDC, Closes 62° ABDC, 0.015" clearance (cold), 0.533" lift
Exhaust: Valve opens 76° BBDC, Closes 26° ATDC, 0.020" clearance (cold), 0.533" lift

V-1650-7

Firing Order 1A-6B-4A-3B-2A-5B-6A-1B-3A-4B-5A-2B

Spark timing Fully Advanced: Intake 45° btc, Exhaust 50° btc, Magneto breaker gap 0.011-0.014

Cam Timing
(crank degrees) Intake: Valve opens 31° BTDC, Closes 52° ABDC, 0.015" clearance (cold), 0.590" max lift -- Note: Time w/0.020
Exhaust: Valve opens 72° BBDC, Closes 12° ATDC, 0.020" clearance (cold), 0.590" max lift
263° intake duration, 264° exhaust duration
Note: Tappet clearance for timing -- 0.020"

The Griffon rotated opposite to the Merlin.

Larger capacity engines always produce a deeper growl.