Stock 1.6 with 2860RS at 12psi - Page 4 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 09-06-2010, 11:28 PM   #61
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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.
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Old 09-07-2010, 09:51 AM   #62
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Quote:
Originally Posted by shlammed View Post
get the 2871R 0.64 housing then... if you were to run the engine up to or over 8 grand then you would need the extra flow of the 0.86
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.
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Old 09-07-2010, 02:17 PM   #63
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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.
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Old 09-07-2010, 02:24 PM   #64
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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.

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Old 09-07-2010, 02:32 PM   #65
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****... 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.
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Old 09-07-2010, 03:45 PM   #66
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the spool shouldnt be that different, but my new 2871 vs my used 2860 spooled the same.

its well worthwhile though
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Old 09-07-2010, 04:17 PM   #67
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Quote:
Originally Posted by jtothawhat View Post
.86 hotside I think is too big, should have went .63 the power difference isn't worth the lag associated with the .86. Numbers don't seem right though, I made 60+ whp more at only 3 more psi then you with a .48 hotside
.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 **** 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.
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