Originally Posted by Concillian
high compression on gas that supports it will give more power at "low" boost. (low being anything below the threshold where the CR + octane allow ~MBT as actual timing without det.) So while high compression isn't going to spool like AVCS will, it is helping your peak HP numbers.
There are plenty of turbos that spool like yours or better and can make this power if they had the compression advantage your engine does, but you won't see dynos of them, since the vast majority of people who would build high compression for better off-boost or midrange torque would build with AVCS, since it's a bigger factor. Anyone who actually cares about boost threshold and off-boost torque will have AVCS.
As a result, your oddball engine has guaranteed there are no fair comparisons. Anyone who points to something that shows a better dyno, you're going to point at the spool and say look, AVCS. It's pointless showing any examples, there's just nothing that will come out of it.
Your dyno only really shows 2 things:
1) moderately higher compression + moderate boost on E85 is a good thing. You're gaining power since there is octane to spare on normal compression.
2) The HTA71 doesn't suck. This may seem like a small thing, but I think it's kinda big. You might expect it to suck from what appear to be mismatched wheels, but a turbo that sucks cannot have a decent balance of spool and power, but your chart shows a decent balance of spool and power.
I don't think you can draw the conclusion that the HTA71 is better or worse than similar sized turbos until you get it on an engine that doesn't have gimpy spool built-in, though.
See...now we are speaking the same language.
I do however disagree that there are a 'lot' of turbos that can spool at 3800-3900 and pull this kind of peak power and boost to to 7.5K the way this one does.
I agree with you on the above points...i wish i had been able to go with AVCS, as an autocross car, it would have been incredibly valuable.
This turbo is excellent, especially if you are running E85, it has exceeded my expectations in every possible way.