OK, a bit more boost now. It is definitely lazy on the bottom, although it doesn't feel that way on the street. I think the IWG is being blown open because the preload is so low. I'm going to add some preload and maybe play with the medium boost actuator this week.
Run 1 = stock exhaust, 5psi
Run 2 = 3" catted exhaust, 7psi
Run 3 = 3" catted exhaust, 11psi
Easy to test by comparing boost curves with and without wastegate can connected (til overboost cuts in). I will guess it's the boost control.
On my GT2560 I got 200 ft-lbs at 3300 RPM with a 5 psi (albeit large diameter) can.
Pull 9 is without boost control on, and the boost doesn't rise smoothly to peak either. Leads me to believe it's mechanical and not a settings issue. Maybe not blowing open but cracking at low pressure which substantially delays the powerband.
Disconnecting the boost line to the wastegate can will tell you the max potential spoolup. (properly tuned EBC should match it). And if it's still weak, then the higher boost can test compared to that will tell you if it's blowing open.
Not necessarily expecting people to do that, since you can just buy any V8-specific T5 and it will work here, but I am anticipating that a lot of people will opt to buy the V6 box and swap the input shaft since you save several hundred dollars in the process. In fact, you can buy the box from LKQ (~$250), a Tremec rebuild kit ($330), plus the input shaft and requisite parts ($50), and probably pay someone else to assemble it ($300ish), and you'll still have a new V6 box with the better OD for less money than the V8 box.
You've done the research on the combo, that's tedious. If you say "buy this part from here, that part from there", or better yet "my part number xx" then awesome. I'd be on board for that.
I know you opted to do a shifter adapter and cut the tunnel to make it fit. What do you think about removing that freeze plug? I don't think it can be left open, but I think it could be sealed back up fairly easily.
The hole needs to be sealed somehow. I think the shaft extension needs to be supported as well, perhaps with whatever is used to seal the hole. Tricky. I haven't seen BEGI's or that other place's solution. If you seal to whatever extension, the seal has to allow radial and axial movement.
I did find one guy overseas who built a sealed box below the rear offset shifter that sealed to the hole with a boot and allowed the extended shifter to pass thru it. The support for the shaft was built into the offset mount. I cannot find the pics on google at the moment. But it looked like a PITA.
To connect the extension to the guts of the trans, he removed the plastic shifter ball socket and clamped to the gate piece with a shoulder bolt. It acted like a dowel to keep slop out of that attachment, but I wasn't sure how he got to the nut on the bottom to tighten it.
Would the difference between a v6 belhousing and v8 belhousing be a spacer plate to change the length? Could you build the belhousing for the shorter one and add a spacer between the belhousing and gearbox?
PPF adapter would need to change a bit too I guess. Is the difference in length big enough to require different driveshafts?
Just brainstorming. Because I like $250 for a gearbox. But I don't want to swap input shafts right away. But I also don't want to try and build 2 bellhousings.
V6 input shaft length is ~7.8" IIRC. V8 is 7.18". The spacer plate alone would be ~$100 in material, plus machine time to make it usable, plus modification of the PPF, plus a different custom driveshaft. Way more work than swapping the input shaft. On the T5, you remove the bearing cover (4 bolts), slide the input shaft out (seriously, that's all you do), slide the new input shaft in (with the bearing already pressed on because the place you bought it from did that for free), install the new bearing cover, and then check preload and reshim as necessary. The hardest part is re-shimming.
We will build around the V8 input shaft because that's what every aftermarket gearset is built around.
e: Start at 1:07. He has the input shaft out in ~30 seconds. If you can get the transmission out of the car in the first place, the input shaft swap is a piece of cake
Watched most of that video. It frustrates me watching him just chuck parts and bolts everywhere when he takes it apart. I guess if you've done it 100x you can figure out how it all goes back together, but that gave me a headache.