You think I should just go for the 2871? Damn I wish there was more real life experience with these on this site for 1.6's.

don't forget the the cams or the IM...


regardless, you should know the math behind it:

Volume Air Flow = (L/28.317) x (RPM/2) x VE

1.6L / 28.317 = 0.0565

8000/2 = 4000

VE = 118% (according to my VE table)
.0.0565 x 4000 x 1.18 = 266.7 CFM /14.47 = 18.43 lb/min

The .64 housing at 2PR (15psi) maxes out around 16 lb/min, where the .84 reaches max efficiency around 21 lb/min, so in this situation, the .84 might be better served.

If you were to stay around stock redline, 7250, then you'd be closer to 17 lb/min of gas turbine flow so it's kinda a toss up since the turbine will be working just over it's full potential without choking up.

Brain, does that equation work the same with a smaller turbo?

Garrett's site doesn't list the 2860r-5 with a .86 housing. So by the looks of it I may have to go with a 28RS. I'm buying Lev's Blox intake manifold which should help a bit as well.

its just volume air flow, it doesn't change. you are always ingesting and compressing the same volume...only the density and rpm will effect it. you just need to see a turbine map and then you can determine what size would be best fit for the amount of exhaust you are flowing.

the general consensus we've determined here is a pretty good rule of thumb.

Newbsauce has a 1.7L with a .64 A/R 2871, at 17psi his TQ, even with an IM, TQ was still dropping off...so maybe it's time for a bigger turbine housing, we kept pushing the timing and there was just no more power to be had up top.

http://www.boostedmiata.com/gallery2...e_after_IM.jpg

Shit... I thought I had it all figured out with compressor maps but now theres something new to learn.

From what I've read as well though... with a v-band TiAL spool is a bit better still? So it may be best to just go for the .86 if I'm going TiAL.

With the head and intake manifold it shouldn't be terrible.

the spool shouldnt be that different, but my new 2871 vs my used 2860 spooled the same.

its well worthwhile though

.63/.48 = T3 housings. a T25 .86 is about comparable to a T3 .63 housing. Nobody in their right mind goes beyond a T3 .63 housing (I think the next step is .81 or something).

Jason has measured really high TIP with his 2560 .64, and didn't BEGi have shit results with their original S6 car (rharris' car) with a .64 housing?

If you're going to push the car beyond 300whp, I'd really consider an .86 housing very strongly.