which is a very bad idea

Those are a bit big for my application. Based on the compressor maps of the 56 trim 2871, 18-20psi will put me right in the center of the middle efficency island while also providing reasonable spool. Any number of turbos can get you to a peak power number, but I didn't want to be running out of steam with the super 60 or disco potato and I didn't want a oversize turbo (relatively speaking) like the 60-1, SC61, T04E 57 trim for a 1.6L that would spool really late giving me a very small powerband. Having had several turbo kits and the opportunity to drive many turbo cars, I'd say more important than just the final peak numbers is the shape of the torque curve and power delivery. My 2 cents.

whatever term? you mean which turbo?!

T3 Super 60 = T3 Super 60
T3 Super 60 :ne: T3/T4 60-1

T3 Super 60 = 60mm compressor wheel
Garrett 60-1 = 76.2mm compressor wheel
60mm :ne: 76.2mm

T3 S60 = 60mm
T3/t4 60-1 = 60 trim
60mm :ne: 60 trim

T3 Super 60 = 275-300HP
T3/T4 60-1 = 600-640HP
300HP :ne: 640HP

:noes: :noob:

ha ha, be nice, I have never needed a turbo that big so got them confused!!

Been thinking about this a bit more and making a big assumption, here's my take:

The assumption that I'm making is that since the turbine wheel stays the same, that the overall radius of the T28 and T3 housings for the same turbo stay pretty much the same.

Making the above assumption, the turbine A/R is simply a ratio of cross-sectional flow area to the distance from the center of the housing. So to make the math easy, let's say that the 0.64 A/R T28 housing has an inlet cross sectional area of 100 units squared. So, at a radius of 100 units from center, the cross sectional area would be 64 units squared.

Since a T3 housing has a 133% larger inlet area, the beginning inlet cross sectional area would be 133 units squared. Then, at the same radius of 100 units from the center of the housing, the cross sectional area would be 63.84 units squared with a 0.48 A/R (0.48 * 100 * 133/100), and 85.12 units squared with a 0.64 A/R (0.64 * 100 * 133/100)

Thus, assuming that cross sectional area can be taken as a surrogate for flow, the 0.48 A/R T3 housing mathematically should flow very similar to a 0.64 A/R T28 housing, and a 0.64 A/R T3 housing mathematically should flow similar to a 0.86 A/R T28 housing.

Yes, trying to convince myself that I'm making the right choice. Yes, it's called rationalization.

Assumptions suck.

I don't know if I would assume the A/R of the T3 housing (or the T2, or any turbine ever) is the same starting at the inlet to the turbine. Just because the hole at the inlet flange is the T3 size, doesn't mean 1" into the turbine it's still the same amount larger than the T2 turbine. My GT1548's have a T2 flange but neck down very quickly after the flange. If I were ATP and making custom cast turbines, I would copy the geometry of the original, except with the modified flange attached. So .64A/R T2 would be the same as a .64A/R T3. But that's my logic. If they are taking standard T3 turbines and machining them to mate to the GT28 center section I dunno then.

I would call and talk to some Guru at ATP.

I may have misunderstood your point, but the shorty tubey should spool better than a log mani.

Thanks for the suggestion. I did e-mail the tech guys a bit back and finally got an answer today pasted below. No turbine flow map, but better than nothing! Woohoo!

"It's just as you suspected, T3 of the same A/R is bigger than T25.

T3 .48 has similar turbine flow numbers as T25 .64 A/R.

This is due to the two being different "framesizes" and so the scaling of
the dimensions are different.

Thank you."

Tom's is not a shorty tubular. I'd expect it to spool slower than a log / shorty tubular, but make more top end.