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Since we are talking about a defined power figure (400whp), that defines our airflow requirement, and we don't have to worry about RPM.
With turbine A/R you are playing with backpressure and flow. Small A/R builds backpressure early (read: spools early) and maintains that pressure as power and flow increase. Large A/R is lazy on the bottom but allows for more turbine flow on top, which promotes flow through the entire engine. If you are worried about spool, you generally want to stay small. Sometimes that's not true, and the factors at play in making that decision are really, really hard to model (like, only OEMs do it).
To start: I do not disagree with all you say Savington, but I am not fully sure the 0.64 A/R 6258 is a good match to a 2ZZ-GE.
You have to fill in the numbers. I think two factors are important and different from a Miata: gearing and N/A power.
RPM does matter for the car as a whole as it goes hand in hand with gearing.
The 2ZZ-GE does make 30% more power compared to the BP normally aspirated and does it at higher revs. If your gearing allows or even forces you to use the higher revs, then a higher A/R might be desired as it will not choke the motor at higher RPM.
I guess you have to fill in the numbers and apart from a horsepower number, you might also want to define a power band. The 2ZZ will be on par with the BP from 3000 to 5000 rpm, but from 5000 rpm onwards the 2ZZ is a different beast. The 2ZZ will make more power at the same boost level.
The only EFR Lotus Elise I've found, and he removed the whole trunk area... Not a good sign for being able to physically fit this unit, but the acceleration looks amazing.
Another point to consider, tuners familiar with the 2ZZ are suggesting a 10:1 or 10.5:1 compression ratio for what I'm looking to do.
Been reading on the honda boards and they're mirroring @Savington's advice for small displacement motors. The .64 T25 flange is the way to go, so twin scroll is out.
So between the higher compression, higher head flow and higher red line, I might be able to get away with spooling up a 6758 in .64, what say you guys?
Keep in mind that I'd like to have that mid-high 300s on pump, and the only people I've seen do that on the 6258 on here are Ari 99Mx5. His 375whp on the mustang dyno, on pump is exactly what I'm looking for, most fall into the low 300s range though.
Also the car will be using an A2W with this setup (similar routing to this setup only A2W instead of A2A) so the cold side tubing length is about 1 foot
We have done it on E02K's car too. No one seems to ever remember
I searched for that screen name, trying to look for the thread to look into it, but I'm assuming E02K isn't their full screen name.
My thought on this is to get to these higher 300s on pump on the BP motors you need some port work to the head and full length manifold. Was going to check out E02K's build to confirm
12-27-2017, 06:12 PM
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