Tilt, thats why you come back each year to the Con

to finish all the discussions you ran out of time for the year before!
My understanding on the engine is that the WWII version of the engine of the Yak-9U was the VK107, the VK107A was introduced after the war which had water injection I believe (or some other form of WEP). The Korean vintage Yak-9U used the VK107A. I was reading that in the Air & Space Museum Bookstore in a really good book on aircraft engines, that I wanted too buy but passed on, because it was quite expensive. Like $80 or something. But since then I've really regretted it, since its hard to find and I wish I'd bought it. I have some engine charts somewhere of original Soviet data on Yak's and V-105PF and VK107 engines that a friend sent me, but since I don't read Russian, it doesn't help me alot.
I believe that the data on production 9U's from 1945 that outperform the 1944 version is simply a matter of quality. Production quality increased, and if you read Gordon & Khazanov, made major improvements in performance.
I waffle back and forth somewhat on my stand of the "production versus prototype" issues, and I definitely realize the issue of some "fudging" of data at times, especially early in the war when Stalin was executing everyone left and right. But then I think back to the fact that the Allied aircraft used for testing purposes weren't exactly "standard" untouched aircraft straight off the production line either. Usually they had the best engineers and mechanics from the factory and or the Air Force, making sure that the aircraft performed up to its maximum limits. And if the aircraft wasn't performing up to par, it was fixed and tinkered with until it did. Remember, big contract's and alot of money were riding on these tests, so there was alot at stake.
So when you then compare the Allied tests against tests made to determine production line quality, I just don't quite think its an "apples to apples" comparsion either.
I'll let you know how good the new Gordon & Khazanov book is. I'm really looking forward to seeing if its up to the quality of their past work. I also bought Gordon's book on the Mig21 and the Mig15, both of which are excellent. So I have the Mig17 book on order, and the new Yakolev book as well.