the hustler effect. smaller A/R on bigger turbo = better spool. - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


DIY Turbo Discussion greddy on a 1.8? homebrew kit?

Reply
 
 
 
LinkBack Thread Tools
Old 08-20-2009, 12:47 AM   #21
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by JasonC SBB View Post
Either #1 or #3 will spool quickest but if you can get the turbine maps then I can tell you for sure.
the 2871 has the same hot-side as the gt2860rs super turbo.
hustler is offline   Reply With Quote
Old 08-20-2009, 03:24 AM   #22
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

GT2860RS with 0.86 A/R
vs
GT2871 with 0.64 A/R

I'd need to see the full turbine maps. Basically look at the compressors, for say 3500 RPM and 7.5 psi, read out the RPM and efficiency. Calculate the shaft power and engine horsepower. Then, look at the turbine maps and determine if that exhaust flow at that horsepower can deliver that required shaft power at that shaft RPM. Whichever has more excess shaft power will spool quicker at 3500 RPM. Repeat this at 0, 5, 10 psi; at whatever psi there is no excess shaft power from the turbine, will be the max boost at that RPM.
JasonC SBB is offline   Reply With Quote
Old 08-20-2009, 03:29 AM   #23
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

P.S. my gut feel is the 2871 with 0.64 would spool quicker, but a 2860 with 0.64 would be even quicker.

The reason for that is the small A/R would generate more shaft power at lower exhaust flow rates, even when comparing the 2 compressors (and thus at different shaft RPMs).
JasonC SBB is offline   Reply With Quote
Old 08-20-2009, 11:07 AM   #24
y8s
2 Props,3 Dildos,& 1 Cat
Thread Starter
iTrader: (8)
 
y8s's Avatar
 
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,038
Total Cats: 407
Default

Quote:
Originally Posted by hustler View Post
if you ignore spark angle, then why waste time with this bullshit question?
what if I let you pick one of two conditions? all used with the same spark table OR all tuned to MBT by whatever means necessary--like a super low comp motor or water injection or 100 octane fuel.

you can't really argue the point about MBT without actually putting the .64 on and tuning it because even though it might seem to preclude running near MBT, none of us has data to prove it. so lets assume we can cheat that portion by other means in choice 2.

Quote:
Originally Posted by hustler View Post
the 2871 has the same hot-side as the gt2860rs super turbo.
All those turbos share the same hotside wheel. 53.8mm 76 trim. here's the garrett excuse for a map.

y8s is offline   Reply With Quote
Old 08-20-2009, 11:26 AM   #25
Elite Member
iTrader: (4)
 
Join Date: Sep 2006
Location: Charlotte, NC
Posts: 3,049
Total Cats: 4
Default

I'm with Hustler on this one. I'm switching to a bigger A/R turbine because I almost exclusively track my car and I would rather have lower underhood temps and lower engine load than 400rpm earlier spool.

Bigger A/R = less restriction = less overall heat output by the turbine = lower underhood temps = happier track car..... at least that's what "Maximum Boost" taught me.
Efini~FC3S is offline   Reply With Quote
Old 08-20-2009, 11:49 AM   #26
y8s
2 Props,3 Dildos,& 1 Cat
Thread Starter
iTrader: (8)
 
y8s's Avatar
 
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,038
Total Cats: 407
Default

Quote:
Originally Posted by Efini~FC3S View Post
I'm with Hustler on this one. I'm switching to a bigger A/R turbine because I almost exclusively track my car and I would rather have lower underhood temps and lower engine load than 400rpm earlier spool.

Bigger A/R = less restriction = less overall heat output by the turbine = lower underhood temps = happier track car..... at least that's what "Maximum Boost" taught me.
circular logic.. hustler got his turbo originally from Corky who wrote that book
y8s is offline   Reply With Quote
Old 08-20-2009, 12:10 PM   #27
Newb
 
Join Date: Aug 2009
Posts: 21
Total Cats: 0
Default

Well, I'm new here, so I'm not going to jump in the fray...but I do have a question:

Where are the pre and post turbine pressure measurements? That is what dictates whether a turbine A/R is too "big" or too "small."

Turbine pressure ratios dictate spool. Not EGT's, although EGT's and mass air flow dictate how much energy there is to be extracted from the exhaust.
thefoos is offline   Reply With Quote
Old 08-20-2009, 12:26 PM   #28
Elite Member
iTrader: (41)
 
Join Date: Jan 2006
Location: Seabrook, TX
Posts: 2,409
Total Cats: 19
Default

I am running the .64 on my 2860 for my street/track car. I did that beacsue I am ultimately not looking to make 375 hp, just around 300-340. Even then, the car will be a handful on the track.

I don't feel that in the range that I will be running, with respect to power, that the heat will cause a significant enough difference to merit a larger A/R. If and when I push it further, then it may come into play more. At that point I will move up to an .86 2871, IF I need more than 325hp on the track for some retarted reason. These assumptions were made on my limited knowledge of how all of this crap works, so if my logic is wrong please call me out on it.
rharris19 is offline   Reply With Quote
Old 08-20-2009, 06:52 PM   #29
Junior Member
iTrader: (7)
 
Join Date: Nov 2006
Location: Makakilo
Posts: 444
Total Cats: 0
Default

Quote:
Originally Posted by Efini~FC3S View Post
I'm with Hustler on this one. I'm switching to a bigger A/R turbine because I almost exclusively track my car and I would rather have lower underhood temps and lower engine load than 400rpm earlier spool.

Bigger A/R = less restriction = less overall heat output by the turbine = lower underhood temps = happier track car..... at least that's what "Maximum Boost" taught me.
Garrett agrees with that line of thought too:
TurboByGarrett.com - Turbo Tech102
Quote:
Originally Posted by Garrett Turbo Tech 102
Turbine A/R - Turbine performance is greatly affected by changing the A/R of the housing, as it is used to adjust the flow capacity of the turbine. Using a smaller A/R will increase the exhaust gas velocity into the turbine wheel. This provides increased turbine power at lower engine speeds, resulting in a quicker boost rise. However, a small A/R also causes the flow to enter the wheel more tangentially, which reduces the ultimate flow capacity of the turbine wheel. This will tend to increase exhaust backpressure and hence reduce the engine's ability to "breathe" effectively at high RPM, adversely affecting peak engine power.

Conversely, using a larger A/R will lower exhaust gas velocity, and delay boost rise. The flow in a larger A/R housing enters the wheel in a more radial fashion, increasing the wheel's effective flow capacity, resulting in lower backpressure and better power at higher engine speeds.
r808 is offline   Reply With Quote
Old 08-21-2009, 06:02 PM   #30
Elite Member
iTrader: (41)
 
Join Date: Jan 2006
Location: Seabrook, TX
Posts: 2,409
Total Cats: 19
Default

I may have fallen victim to my own idiocity. With my smaller .64 ar I am not hitting a brick wall for power. It may be the turbo or may not, but i have a feeling it is just because I thought I was doing the right thing for response, but it punished me severely in overall power. I should have gone with a .86 2871 to begin with.
rharris19 is offline   Reply With Quote
Old 08-21-2009, 06:15 PM   #31
meatbag
iTrader: (50)
 
gospeed81's Avatar
 
Join Date: Nov 2008
Location: Houston, TX
Posts: 7,357
Total Cats: 26
Default

Links to dyno sheet?

Sorry, I looked.
gospeed81 is offline   Reply With Quote
Old 08-21-2009, 06:35 PM   #32
Tour de Franzia
iTrader: (6)
 
hustler's Avatar
 
Join Date: Jun 2006
Location: Republic of Dallas
Posts: 29,114
Total Cats: 351
Default

Quote:
Originally Posted by rharris19 View Post
I may have fallen victim to my own idiocity. With my smaller .64 ar I am not hitting a brick wall for power. It may be the turbo or may not, but i have a feeling it is just because I thought I was doing the right thing for response, but it punished me severely in overall power. I should have gone with a .86 2871 to begin with.
Details on how Y8's is a mouthy-------? Seriously, sentence #1 and #2 contradict the last sentence.
hustler is offline   Reply With Quote
Old 08-21-2009, 06:50 PM   #33
Junior Member
iTrader: (1)
 
Join Date: Dec 2008
Location: Silicon Valley
Posts: 160
Total Cats: 0
Default

Quote:
Originally Posted by rharris19 View Post
I may have fallen victim to my own idiocity. With my smaller .64 ar I am not hitting a brick wall for power. It may be the turbo or may not, but i have a feeling it is just because I thought I was doing the right thing for response, but it punished me severely in overall power. I should have gone with a .86 2871 to begin with.
Not to cause a fuss, but I don't understand the third sentence with all the buts. Actually, it may have been infinitely more less clear if you had buts instead of periods between every statement. I am just saying that I had to read it twice and still don't know what it says. I think the first and last sentence make perfect sense though. Sorry for my idiocitiness.
superslow is offline   Reply With Quote
Old 08-21-2009, 06:52 PM   #34
Elite Member
iTrader: (1)
 
NA6C-Guy's Avatar
 
Join Date: Feb 2008
Location: Birmingham Alabama
Posts: 8,038
Total Cats: 43
Default

Continue
NA6C-Guy is offline   Reply With Quote
Old 08-21-2009, 07:52 PM   #35
Elite Member
iTrader: (7)
 
samnavy's Avatar
 
Join Date: Apr 2006
Location: VIRGINIA BEACH, VA
Posts: 6,020
Total Cats: 175
Default

These are really good threads, just the right amount of discussion vs. friendly ****-talking.

This thread, and about 1/2 dozen more like it have cemented my choice of the .64 Disco as the turbo of choice for a 300whp street-car.

What I really want is a few more people to start exploring the 300whp range on stock 99-00 motors and gather datapoints. So far, there are only a few guys who do it.

S4, exhintake, adj cam-gears, Adaptronic, 3" exhaust... I CAN'T WAIT FOR CRUISE TO BE OVER!!!
samnavy is offline   Reply With Quote
Old 08-21-2009, 11:11 PM   #36
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

BTW this is what full turbine maps look like so one would be able to predict spoolup. Compare to what y8s posted above from Garrett:





And a subset of the above

JasonC SBB is offline   Reply With Quote
Old 08-21-2009, 11:32 PM   #37
Junior Member
iTrader: (7)
 
Join Date: Nov 2006
Location: Makakilo
Posts: 444
Total Cats: 0
Default

Edited for binge drinking post crapping stupidity.

Last edited by r808; 08-30-2009 at 04:26 AM.
r808 is offline   Reply With Quote
Old 08-22-2009, 12:03 AM   #38
Elite Member
iTrader: (41)
 
Join Date: Jan 2006
Location: Seabrook, TX
Posts: 2,409
Total Cats: 19
Default

Sorry, I need to clean up that last sentence. I really didn't read through it before I posted. What I was saying is that I thought the trade off for ultimate power for quicker response would be better than what it was. I am now feeling the punishment for not doing my homework and assuming my logic is flawless.

This turbo would really be great for a daily car.
rharris19 is offline   Reply With Quote
Old 08-22-2009, 10:35 AM   #39
Newb
 
Join Date: Aug 2009
Posts: 21
Total Cats: 0
Default

Quote:
Originally Posted by rharris19 View Post
Sorry, I need to clean up that last sentence. I really didn't read through it before I posted. What I was saying is that I thought the trade off for ultimate power for quicker response would be better than what it was. I am now feeling the punishment for not doing my homework and assuming my logic is flawless.

This turbo would really be great for a daily car.
There is a lot of assuming and bs in this thread. Making decisions without some sort of data and analysis means you all are tuning blind...

What are your pre and post turbine pressure measurements? What are your compressor efficiencies? What is your pre-turbo pressure to manifold pressure ratio? What data are you using to make your assumptions?
thefoos is offline   Reply With Quote
Old 08-22-2009, 02:30 PM   #40
y8s
2 Props,3 Dildos,& 1 Cat
Thread Starter
iTrader: (8)
 
y8s's Avatar
 
Join Date: Jun 2005
Location: Fake Virginia
Posts: 19,038
Total Cats: 407
Default

Quote:
Originally Posted by hustler View Post
Details on how Y8's is a mouthy-------? Seriously, sentence #1 and #2 contradict the last sentence.
you of all people should know how important it is to question the current dogma. that's what I'm doing.

Quote:
Originally Posted by rharris19 View Post
Sorry, I need to clean up that last sentence. I really didn't read through it before I posted. What I was saying is that I thought the trade off for ultimate power for quicker response would be better than what it was. I am now feeling the punishment for not doing my homework and assuming my logic is flawless.

This turbo would really be great for a daily car.
you mean you should have chosen the 2871 .86 at first instead of trying the 2860 .64 for a street car and hoping for better spool with the latter?
y8s is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 57 07-19-2017 05:11 PM
Expected intake temps on the track? tazswing Race Prep 20 10-03-2015 12:04 PM
Moroso Air Oil Separator Catch Can Aroundcorner Miata parts for sale/trade 2 10-01-2015 04:20 PM
ISO 1.6 turbo cast iron manifold cale saurage DIY Turbo Discussion 16 10-01-2015 12:25 PM


Tags
a/r

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 03:28 AM.