Tim, thanks for your reply, however we should take a few more things into account here. Firstly when the group "think tank" happened a few years ago there were a few of us with standard cowls seeing vastly inconsistent results. In other words at no time would we ever see the same spread or order of peaks. Sure there is a small variation each time, but we were getting vastly differeing results such that every test was so different you could not make any adjustment as the next result defied the change even.
You might recall when I pulled the Alternate Air source, I found a large DP, and then and only then could I get a consistent "GAMI Spread" test a few times in a row.
I also recall the issue of stumbles when LOP, some of us were keen to get to the stumbles stage at least, as tuning was a nightmare.
The very instant we fitted a "turbo" injector system, all this went away. Tuning became predictable and consistent.
You might recall we all went to great lengths to be as scientific as we could, and not react to just heresay. I do wonder however, if those folk who do not seem to have a problem have different setups and for that matter are not operating at higher altitudes and WOT.
The problem is created as you say by DP. And if you are at low level, pull the MP back to 23", the problem seems to go away, less pressure inside than out.
Now my expectation is that everyone has a pretty well sealed upper deck, cooling is good, CHT's from 300-330 typically, and they have the air intake rubbers sealing well. If they do this, I then expect they will generate some ram air effect and have a higher pressure in the intake Vs the upper deck or ambient.
All that being equal...........and here is my point, now that you know that this is a likely scenario....and you will build a good low leakage cowling etc, and you want to tune for good LOP operations, and you do not want to be like a dog chasing its tail,
AND you live in Australia a long way and time/expense for everything later on, you would be far better off ordering the engine with Don's injection and turbo rail setup from the start.
If I ordered a new engine tomorrow, I would have Dons system installed before it was shipped, or at least all the parts sent with the engine in a box so I could install it.
It cost me thousands $$ in time, fuel, airfreighting injectors, flow bench adjusting and a few damaged threads, so why would I expose myself to all that when for a few hundred dollars I could have the better option from the start. It is just so much easier to do when the airflow to the bleed hole is perfect.
Of the three folks down here, that eventually fitted my home grown turbo kit which uses standard injector bodies, we all found an instant fix. This was not just a one off.
Why did I build my own? First it was not money, it cost about the same, but it was at least 2 weeks quicker, I made them suit a stock injector which we tuned locally, and could buy locally. I had two other folk down here needing them so it was worth the trouble.
Would I do that again? No, apart from the fact my "fit a standard Injector" is better for us, if I had to do this again I would order an engine and have all the bits done for me.
A set of bleed air rails and turbo nozzles for a six cylinder Lycoming adds $713.00 to the price of the kit. I know most customers don?t want to spend needless money. We would rather take each case separately as the majority of installations run just fine with the stock parts.
Don, I certainly can't speak for all your customers, but are you sure that is exactly how all your customers think. I do not think your customers are thinking this through long term. Your Turbo Nozzle kit is not cheap, nor is it expensive, but for $713 compared to the REAL COST of mucking around, it is cheap. And is it cheaper if they fit this from the start? Less the standard injector? Might only be $550 then.
Folks....please do not read this post as me attacking Tim or Don. A lot of us spent a lot of time and money sorting this out, I just do not see the small investment compared to the benefit as being that trivial, especially when you live down here.