Warbird Information Exchange

How does a turbo-supercharged Allison, say from a p-38J, compare to a Merlin, say from a Mk IX Spitfire.

The Allison probably keeps more of its oil on the inside.

B

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Look up the performance at various altitudes of the different models and that will gives you constant values to compare.

The Turbo was an accessory to enable the engine to maintain horsepower at higher altitudes that the thinning air density robs.
The Allison had an internal Surpercharger in the engine as well.
The Supercharger in various models of the Merlin was superior in operation and effectiveness than the wartime Allisons. They operated at different speeds via a clutch/gear system and had 2 stages or sets of compressor wheels. The 2 Stage/2 Speed system did the same job as the exterior Turbo did on the Allison.

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I wrote a short article some years ago about the development of the Allison engine that might be of interest. The engine was designed to have a turbocharger for aircraft use. Here is a link.

http://rwebs.net/dispatch/output.asp?ArticleID=19

Randy

nice write up Randy. never gave a thought to how the engine got it name. good info.

This is all y"all need to know about ALLISONS and that is you can fly the Allison farther than you can ship the merlin.

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Thanks for all the replies.

Indeed! Thanks.

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James K

"Switch on the underwater landing lights"
Emilio Largo, Thunderball.

www.VintageAeroWriter.com

My buddy Ralph Payne used to be fond of saying "A Merlin in a box is faster than an Allison in a plane".

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Ralph left out the part about the merlin in the box being in the cargo hold of a 707.NEENER,NEENER,NEENER

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Hang The Expense

Another thread missing The Inspector's unique input.

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James K

"Switch on the underwater landing lights"
Emilio Largo, Thunderball.

www.VintageAeroWriter.com

I was just thinking the same thing, James. Here's a post of The Inspector's I searched out...

"Vlado,
Two seasons of wrenching in Unlimited Hydroplane racing, where after the first season, the owner looked at our really cool stack of V-7 and V-5 MERLIN blocks behind the boatshop caused by breaking rods and decided to give ALLISONS a try, we broke exactly two ALLISONS in the next 12 race season, one when an oil line fitting failed and the other broke a blade rod. Punching a two bladed 13 X 23 steel prop into a Lake @ 16000 RPM's is like digging out a trowel sized piece of your driveway 16000 times a minute, want some loading on parts? The engine turns around 5000 RPM bolted to 3 to 1 step up gearbox turning the prop (bolted to a 3 inch diameter nickel/steel prop shaft 12 feet long) about 15-16 K a minute to make 7500 lbs of plywood go 185 MPH over the water riding on less than the area of a sheet of paper divided by 2 and one prop blade.
They are as easy to work on as a really big block Chevy, you need about two dozen wrenches, a few screwdrivers, a '16 oz persuader' or two and a couple different socket sets, and some pliers, not the Gold Card pass to the SNAP OFF tool truck for Whitworth or British Standard wrenches for two bolts or fittings @ $45.00 1969 dollars, or more each that you need once a race date (maybe) but can't live without, particularly if the wrench is in the shop in South Seattle and you really need it in Guntersville, AL now. You haven't lived until you've spent all night sitting in the pits at a cold after dark lakeside finger pier trying to make a temperamental pile of metal run after sneezing a couple of rods in qualifying, and you aren't on the Miss Budweiser team, or GALE, or EXIDE.
Just before the Unlims went turbine, one of the best financed teams actually cut up several blown up MERLINS and spliced together a -9 they named 'ACNE' because it was so ugly, it lasted one race weekend and grenaded again, but it won the three heats it was entered in and the final, and no one could compete with Bernie Little and the GRIFFON powered Miss Bud.
We'd build a couple motors over the off season, put one in the hull and the other in the back of the truck and down the road we'd go. Run the valve lash on Saturday, and put it in the water before the heats we were entered in, flip the starter switch and turn the mag switch and go racing usually with the characteristic stack fires common on ALLISONS in boats (no harm and the fans and TV cameras loved it!) we weren't the fastest but we all had a couple seasons of fun on the sponsors dime.


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