Need info on .64 vs .86 housing with GT2860
09-06-2014, 09:13 PM
#1
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Need info on .64 vs .86 housing with GT2860
I searched and did not find anything conclusive. Anyone with experience using both please let me know your thoughts.
I have a twin turbo 3.6 running GT2860's with .64 AR's. I am thinking of swapping out the housings for .86's to gain a bit more top end. Since Miata's are 1.8 with single turbos I though the results would apply on my application.
I have a twin turbo 3.6 running GT2860's with .64 AR's. I am thinking of swapping out the housings for .86's to gain a bit more top end. Since Miata's are 1.8 with single turbos I though the results would apply on my application.
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09-06-2014, 10:41 PM
#2
yes. Spools later more top end. It' generally accepted that after the 2560r you jump to the 2871 .86.
the spool to power trade off at this point isn't significant enough to warrant not stepping up. .64 is usually a 2560 or a potato. After that it's .86 time unless you efr.
If you want data on it savington has some .86 dyno info but .64 2860s are not common at all around here.
the spool to power trade off at this point isn't significant enough to warrant not stepping up. .64 is usually a 2560 or a potato. After that it's .86 time unless you efr.
If you want data on it savington has some .86 dyno info but .64 2860s are not common at all around here.
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09-06-2014, 11:24 PM
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I have noticed that with a free flowing exhaust and the free flowing .86 Tial V-band turbine housing, I get boost creep to around 3 psi higher than the wastegate spring pressure. This is on a BEGi S6 with 38mm external wastegate. Pretty sure that with a more restrictive .64 exhaust housing I would not be having the creep issues.
Keith
Keith
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09-07-2014, 08:51 AM
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yes. Spools later more top end. It' generally accepted that after the 2560r you jump to the 2871 .86.
the spool to power trade off at this point isn't significant enough to warrant not stepping up. .64 is usually a 2560 or a potato. After that it's .86 time unless you efr.
If you want data on it savington has some .86 dyno info but .64 2860s are not common at all around here.
the spool to power trade off at this point isn't significant enough to warrant not stepping up. .64 is usually a 2560 or a potato. After that it's .86 time unless you efr.
If you want data on it savington has some .86 dyno info but .64 2860s are not common at all around here.
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09-07-2014, 09:55 AM
#6
I have noticed that with a free flowing exhaust and the free flowing .86 Tial V-band turbine housing, I get boost creep to around 3 psi higher than the wastegate spring pressure. This is on a BEGi S6 with 38mm external wastegate. Pretty sure that with a more restrictive .64 exhaust housing I would not be having the creep issues.
Keith
Keith
Once I put the spacer in I could fully swing the gate open without it hitting anything. Creep went away.
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09-07-2014, 12:01 PM
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yes. Spools later more top end. It' generally accepted that after the 2560r you jump to the 2871 .86.
the spool to power trade off at this point isn't significant enough to warrant not stepping up. .64 is usually a 2560 or a potato. After that it's .86 time unless you efr.
If you want data on it savington has some .86 dyno info but .64 2860s are not common at all around here.
the spool to power trade off at this point isn't significant enough to warrant not stepping up. .64 is usually a 2560 or a potato. After that it's .86 time unless you efr.
If you want data on it savington has some .86 dyno info but .64 2860s are not common at all around here.
So you think all of the 2860 dynos I find on MT are the .86? That helps.
Last edited by k24madness; 09-07-2014 at 06:53 PM.
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09-07-2014, 01:01 PM
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I haz 2860 but I've yet to install it. I've often read that the 2560 or the 2871 are the best choices, but I got my 2860 for a great deal and figured "good enough for me" coming from a journal bearing t25.
I assure you, one day I'll find out.
I assure you, one day I'll find out.
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09-07-2014, 01:15 PM
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I have noticed that with a free flowing exhaust and the free flowing .86 Tial V-band turbine housing, I get boost creep to around 3 psi higher than the wastegate spring pressure. This is on a BEGi S6 with 38mm external wastegate. Pretty sure that with a more restrictive .64 exhaust housing I would not be having the creep issues.
Keith
Keith
I don't know if begi changed their sg down pipe or not but I had to add a t25 flange to mine to allow the wastegate arm to open all the way. When it would swing open it would hit and partially plug up the wastegate gas exit.
Once I put the spacer in I could fully swing the gate open without it hitting anything. Creep went away.
Once I put the spacer in I could fully swing the gate open without it hitting anything. Creep went away.
Keith
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09-07-2014, 04:41 PM
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The EWG tube dumping just after the turbine outlet is not in any way ideal, but I think the free flowing Tial .86 housing and 3" exhaust (2.75" down pipe) are contributing factors. What is it about the manifold that would encourage boost creep?
Keith
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09-07-2014, 07:15 PM
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I just found this. My power goals are 500whp at 14-15psi. Does the swap from .64 to .86 still make sense? Will the spool be 300+rpms slower?
It's the turbine. You can't flow anything past ~275-280whp through a .64 T25 turbine housing. Look at BEGi's early attempts with the .64a/r 2860RS on the S4 (?) manifold - the power numbers were pathetic.
I'd never recommend a .64 2860RS to anyone. Hell, I don't even recommend the .86 2860RS - the 2871R's compressor is so much more versatile and the response difference is negligible.
2560R for <250whp or stock motor
2871R for >250whp or built motor
I'd never recommend a .64 2860RS to anyone. Hell, I don't even recommend the .86 2860RS - the 2871R's compressor is so much more versatile and the response difference is negligible.
2560R for <250whp or stock motor
2871R for >250whp or built motor
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09-08-2014, 12:54 PM
#16
man my reading comprehension was total fail I missed the twin part too.
Well that is my limited knowledge based on reading and some real life experience.
I've never used them in twin fashion either but between a couple of my friends and their 240s & my audi. Most of the audi guys switch from twins to a single 2871.
Well that is my limited knowledge based on reading and some real life experience.
I've never used them in twin fashion either but between a couple of my friends and their 240s & my audi. Most of the audi guys switch from twins to a single 2871.
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09-08-2014, 01:10 PM
#17
Now that you got me thinking about it. People upgrade to k04's all the time on audis 2.7t and get somewhere around ~480 (the k04 isn't far off from the 2860 but way crappier curve). Where are you at right now with your .64 housing? Couldn't you just upgrade to a gtx housing? That's a 10% gain supposedly over the gt version...
ANyway just thinking out loud.
ANyway just thinking out loud.
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08-13-2018, 06:13 AM
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Bumping this old thread. I got things apart right now and it’s a good time to re-evaluate the .64 vs .86 turbine. This is NOT a Miata but rather a old 911 twin turbo. Since it’s 3.6 liter running two turbos I figured 1.8 Miata single turbo results could be carried over. I know I’ll loose low end spool with the larger AR. With my equal length headers would that be significant? Looking at current .64 results does it looked choked? Top end seems to breath freely so maybe they’re the way to go? I welcome input one way of the other.
Build 11:1 compression, 7psi boost, 3.6 2v air cooled engine with cams 100 oct. Playing with E85 blends next.
AWD dyno, 7psi tapering to 5psi. I have since added EBC and hold 7psi to redline.
I think the compressor is a great match for this application. When rowing gears 5,500 to 7,200 the map is in the most efficient range.
Build 11:1 compression, 7psi boost, 3.6 2v air cooled engine with cams 100 oct. Playing with E85 blends next.
AWD dyno, 7psi tapering to 5psi. I have since added EBC and hold 7psi to redline.
I think the compressor is a great match for this application. When rowing gears 5,500 to 7,200 the map is in the most efficient range.
Last edited by k24madness; 08-13-2018 at 12:18 PM.
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08-13-2018, 01:00 PM
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At just 7psi, I think you'd be silly to upsize the turbine housings. Big housings are for people who are looking for more power at the expense of low-end response. It's almost always people who are running high boost and running into issues with high TIP (turbine inlet pressure). At 7psi, you don't have high TIP issues. The dyno also indicates no flow restrictions at all (rising power to redline). If you want more power on the top end, just add 1-2psi.
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08-13-2018, 01:48 PM
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Thanks Andrew!
I may may turn up the boost a bit but honestly it’s pretty damn fun as it sits. With the EBC now taking care of boost taper it should not be falling off on top end like shown on the dyno.
The concept from the beginning was to create a fun responsive car. Most of these older 911’s have terrible turbo lag. With 2V non VVT design the challenges are tough. I focused on broadening the torque curve with high compression, wide LSA cams and a unique VRAM intake (multi stage resonance intake with retractable trumpets). I don’t need much boost to get the airflow for good numbers. Right around 450-500AWHP these cars get fun! The ultimate limit is cylinder head temps. I built the engine with E85 in mind, possibility a E50 blend to help keep things cool.
I’ll move forward with the .64 housing again. While apart I’ll have it extrude honed. The guys at Tial and Garrett seem to think it’s well worth the expense.
I may may turn up the boost a bit but honestly it’s pretty damn fun as it sits. With the EBC now taking care of boost taper it should not be falling off on top end like shown on the dyno.
The concept from the beginning was to create a fun responsive car. Most of these older 911’s have terrible turbo lag. With 2V non VVT design the challenges are tough. I focused on broadening the torque curve with high compression, wide LSA cams and a unique VRAM intake (multi stage resonance intake with retractable trumpets). I don’t need much boost to get the airflow for good numbers. Right around 450-500AWHP these cars get fun! The ultimate limit is cylinder head temps. I built the engine with E85 in mind, possibility a E50 blend to help keep things cool.
I’ll move forward with the .64 housing again. While apart I’ll have it extrude honed. The guys at Tial and Garrett seem to think it’s well worth the expense.
Last edited by k24madness; 08-13-2018 at 02:13 PM.
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