ThomasP
Senior Master Sergeant
Hey Reluctant Poster,
Thanks for the info.
Thanks for the info.
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According to Allison it was a a venturiHi ThomasP.
The fuel in the Allison V-1710 is introduced right directly into the supercharger impeller intake. In fact, it sprays right onto the small end of the supercharger impeller. I've helped assemble some 20 of them. The supercharger discharges directly into a large intake manifold that goes straight down the Vee between the cylinder banks. About halfway down, it splits into two tubes going up each cylinder bank. When it reaches the top, each of the two up tubes splits into two 3-cylinder intake manifolds, and the fuel sprays directly into the center of each 3-cylinder manifold. Fours manifolds times three cylinders per manifold is 12 cylinders.
The fuel flow would make the two end cylinders rich and the center cylinder lean. The turbulators or venturis, depending on what terminology you like, kept the air-fuel mixture moving around and kept the mixture even for all cylinders. Reputable builders today don't use the older, non-modified intake manifolds. I've seen them referred to in documents as turbulators, but whether it is called a turbulator or a venturi, it keeps the air-fuel mixture moving around and in more or less homogeneous suspension.
I have much less experience with Merlins, but the Merlin intake tract likely isn't nearly as smooth inside, and maybe that helps.
It also didn't help that early P-38 squadron leaders were having their pilots run the Allisons at low rpm and high MAP on British fuel that was not bad in any way, but WAS different from what the Allisons were jetted for in their carburetors from the factory. That meant lower air-fuel mixture velocity, which might have been the difference between the Allison and Merlin issues (yes, the Merlin had issues in British service, but they were addressed quickly, with the factory right there with test cells and fuel to run in them). I do not claim to know for sure if these U.S. practices were the exact reasons that caused the Allison issues.
What I DO know, for sure, is use of the modified intake manifolds, proper jetting for the fuel used (the early Allison were jetted wrong for British fuel), and proper engine operation eliminated the issues and made the P-38 run very well, even in the ETO. It all took about 9 months from reported engine problems until they were more or les corrected. The cockpit heater and the dive recovery flaps took longer.
Cheers.
Al avgas produced in the US was to the same specifications regardless of it destination.
Agreed. The point I am trying to make is that it wasn't some eccentric British specification, it was the varying nature of the avgas production process that all engines had to account for. The feedstock made a difference as did the method of octane boosting such as Alkylation vs Houdry catalytic cracking vs Thermofor cat cracking vs Fluid Cat cracking vs adding Cumene, etc. all of which could be added in various combinationsHowever the specification/s allowed quite a bit of latitude in the actual fuel composition.
Late war (like 1943 on) was allowed up to 4.6 cc lead per US gallon for 100/130 fuel. Not all batches needed the full 4.6cc to meet the specification. Not all batches got the same percentages of other additives, like the heavy aromatics.
The specifications were a performance specification. Not a recipe.
Performance also included BTUs per pound of fuel, vapor pressure, residual gum, and a number of other things that had no bearing on power output but a lot to do with keeping fuel filters and other small fuel passages clear, getting proper vaporization at altitude (cold temperatures) while avoiding vapor lock at high temperatures.
As long as the fuel met these performance specifications it would be purchased and used almost regardless of actual chemical composition.
There were practical limits. Too much lead fouled spark plugs. The Heavy aromatics had less BTUs per pound than the fuel specs called for so going past 20% aromatics in the blend made it hard to meet the BTUs per pound requirement. The different aromatics had different vaporization temperatures and other properties. A lot of "blends" depended on what a particular refinery had for base stocks and for additives available at a given time.
For two years I had the dizzying job description of inspection, expediting, shipping coordinator for a Japanese engineering company. I frequently was given purchase orders for stuff I and no one else in the company really knew anything about. Some stick in the memory like a "steam sparger" WTF is that. Another was for some rotary airlock valves (also known as star valves). I had no idea what they were or what makes a good or bad one or even any problems you may encounter, so when I arrived at the factory in a beautiful place by a lake near the Alps in South Germany I just asked" these rotary valves, WTF are they". Then there was a complete fibre glass heated pipeline for Hong Kong, who in the world knows anything about fibre glass pipelines apart from the people who make them? At times it was a hoot, the blind leading the blind, with all sorts of words made up like "turbulator".Turbolizers were briefly mentioned in an episode of Battlestar Galactica. The original series.
Actually some wereAgree, but they weren't complaining about being too cold either.
I am well aware of all the data you posted and the way twin engine aircraft are heated, either via engine exhaust or by a separate heater unit. Using an engine exhaust heat exchanger on a twin engine aircraft is obviously inadequate because of the distance between the engine nacelle and the cockpit. Many twin engine aircraft, both commercial and military aircraft will use an independent heating unit because of this. As mentioned many times before, the heating system on the P-38 was ACCEPTED BY THE AAC early in the program. It wasn't until feedback from the field, where the P-38 was being operated as a high altitude escort (something that the aircraft was never designed for) where Lockheed was given the go-ahead BY THE AAF to fix the heating system!!!!Also of note was the cockpit sealing was extremely poor. Considering that Lockheed built the high altitude XC-35 research aircraft before WWII this is inexcusable.
But hey, you call it whatever you want.
The test in question was concluded on January 26, 1943. That's almost a year before the P-38 starting flying long range escort missions over Germany. In fact the tests were being conducted in the same time frame that the time the P-38 was entering combat in the Pacific and North Africa. Regardless of who decided not to improve the heating there was plenty of time to implement a fix before the P-38J began having issues over Germany.I am well aware of all the data you posted and the way twin engine aircraft are heated, either via engine exhaust or by a separate heater unit. Using an engine exhaust heat exchanger on a twin engine aircraft is obviously inadequate because of the distance between the engine nacelle and the cockpit. Many twin engine aircraft, both commercial and military aircraft will use an independent heating unit because of this. As mentioned many times before, the heating system on the P-38 was ACCEPTED BY THE AAC early in the program. It wasn't until feedback from the field, where the P-38 was being operated as a high altitude escort (something that the aircraft was never designed for) where Lockheed was given the go-ahead BY THE AAF to fix the heating system!!!!
Understand that during WW2 (and in today's world) a manufacturer cannot implement a modification without government (or customer) approval!
Lockheed gave "the customer" what they asked for with regards to Circular Proposal X-608. If you want to hold someone accountable for the poor heating system, start with Lt. Benjamin S. Kelsey!!!
Oh - in that March 1943 report, you left out one thing:
View attachment 647278
Yes, there was plenty of time to implement a fix, just as there was plenty of time to fix other issues on the P-38 as well as other aircraft. Again, the contractor (Lockheed) can't and won't implement any major design change (as it's a modification to the contract) unless government approved. My guess is someone at Wright Patterson decided the heating issue wasn't important enough to order an aircraft modification through a contract change or didn't want to halt the production line to implement this modification.The test in question was concluded on January 26, 1943. That's almost a year before the P-38 starting flying long range escort missions over Germany. In fact the tests were being conducted in the same time frame that the time the P-38 was entering combat in the Pacific and North Africa. Regardless of who decided not to improve the heating there was plenty of time to implement a fix before the P-38J began having issues over Germany.
View attachment 647331
I would certainly agree that the P-38F was superior to its American contemporaries.