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Old 12-03-2008, 12:06 AM   #1
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Default begi s3 / gt2860rs crew: what AR turbine did they send you?

I was talking to someone about how my car was making only 5psi at 4k rpm, then 7psi at 5500, and he thinks the turbine housing is too large.

What AR do you have, and at what RPM does it make 10psi? I think I have the .86 and want to change that.

Thanks.



pics for the hell of it:


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Old 12-03-2008, 12:20 AM   #2
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The big housing is not suitable for <300 whp methinks. The 0.64 housing will have far better spoolup.
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Old 12-03-2008, 12:59 AM   #3
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could having the wastegate adjusted pretty far out have that dramatic of an affect on spool? With the wastegate disconnected, the motor is stronger than the 1.6 ever was, even with the lowered compression.
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Old 12-03-2008, 01:14 AM   #4
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pain:
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Old 12-03-2008, 10:18 AM   #5
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Quote:
Originally Posted by hustler View Post
pain:
I bet you have no idea how to read that too

you never happened to look at your turbine housing to see what it actually is did you? Any chance BEGi might have documentation?
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Old 12-03-2008, 10:26 AM   #6
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What is with the inconsistency at BEGi? a friend ordered an S2 or 3 with a 2560 and the intake on the turbo is 3" funneling down to about 2. That thing looks like 2-2.5". What gives?
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Old 12-03-2008, 10:41 AM   #7
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Quote:
Originally Posted by Braineack View Post
I bet you have no idea how to read that too

you never happened to look at your turbine housing to see what it actually is did you? Any chance BEGi might have documentation?
basically, my target pressure ration (2) will be achieved with roughly 25% less airflow through the turbine.

I don't know what's up with the #'s, I'll have a friend go look at it. Any chance a "tuned" spark map will give me 1000rpm better spoolage? What about having the wastegate backed way off? I guess I need to go home, unplug the hose, and see how early it makes target boost. I think with the 1.9l, 3" exhuast, and standard DIY spark map I should be spooling sooner.

If I have to get a smaller turbine housing...then whatever, but I'm getting tired of hemorrhaging money.
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Old 12-03-2008, 10:44 AM   #8
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do you know how many lb/min you displace through your exhaust at a given rpm?
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Old 12-03-2008, 10:51 AM   #9
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Quote:
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do you know how many lb/min you displace through your exhaust at a given rpm?
no, but considering that 25% shift in flow correlated to RPM would put me at roughly 3500rpm, that would be nice. I think that's a fairly accurate assumption because 3500rpm or so is in the neighborhood of peak-torque output.

Is this unreasonable? There are other variables I must address first though...like snugging up the wastegate actuator and pulling the vac hose to the spring, then adjusting spark. I'm about to go get the car and just leave it at BEGi. Time > money.
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Old 12-03-2008, 10:52 AM   #10
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is that what the chart is saying? (and fwiw, it's a 16% shift)
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Old 12-03-2008, 10:58 AM   #11
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Quote:
Originally Posted by hustler View Post
no.

you have a 1.9L motor correct?

The same volume of air is always getting ingested regardless of RPM and boost pressure.

The Corrected Gas Turbine Flow is the amount of this air that moves through the motor during a specific time period. (lb/min)

if you calculate the amount of Volume Air Flow or Gas Turbine Flow in this case, it would be easier to read the turbine efficiency plot based on the demands of your motor.


VAF = (CI/1728) x (RPM/2) x VE

116/1728 x 7000/2 = 235 CFM (16.2 lb/min)

so maybe you want to draw a line up from 2PR and over from 16 lb/min and see where you end up. Then say, hmmmm the max efficiency of the turbine in a .63 A/R housing is just above the volume I displace...so the .86 may be too large for what I need.
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Old 12-03-2008, 11:00 AM   #12
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Quote:
Originally Posted by Braineack View Post
is that what the chart is saying? (and fwiw, it's a 16% shift)
The smaller housing is 74.4% the size of the larger one. I'm apparently talking out of my ***, so correct me. I read till 1:30 last night trying to figure out how much work I have to do when I get back home in January.
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Old 12-03-2008, 11:02 AM   #13
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Quote:
Originally Posted by Braineack View Post
you have a 1.8L motor correct?

The same volume of air is always getting ingested regardless of RPM and boost pressure.

The Corrected Gas Turbine Flow is the amount of this air that moves through the motor during a specific time period. (lb/min)

if you calculate the amount of Volume Air Flow or Gas Turbine Flow in this case, it would be easier to read the turbine efficiency plot based on the demands of your motor.


VAF = (CI/1728) x (RPM/2) x VE

110/1728 x 7000/2 = 223 CFM (15.4 lb/min)

so maybe you want to draw a line up from 2PR and over from 16 lb/min and see where you end up.
Why don't you just do it for me since I'm your bitch. Let me know if you need help with flood insurance, lol.

So, wtf do I need to do since you are an engineer and I'm a beuracrat? Switch to a 2560, or get a smaller turbine housing? I'd still like to get an answer from the DP owners here. I just want to drive my ******* car, not the rental G6.
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Old 12-03-2008, 11:11 AM   #14
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I have the same turbo and turbine size. I have full spool by 4400 or so?
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Old 12-03-2008, 11:11 AM   #15
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all i was saying is that you posted the turbine efficiency plot without knowing how to read it. And im not an engineer, just an artist.


Was this just with a line from the turbo to the wastegate can?
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Old 12-03-2008, 11:12 AM   #16
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Quote:
Originally Posted by Splitime View Post
I have the same turbo and turbine size. I have full spool by 4400 or so?
on a 1.6L no less.
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Old 12-03-2008, 11:14 AM   #17
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Quote:
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I have the same turbo and turbine size. I have full spool by 4400 or so?
you have the .86 turbine housing? My motor is something like 1871cc now, but lower compression, but considering the motor is stronger than the 1.6 off-boost, even with the turbo on the side, I think it should get the turbo spinning.

If yes, then my pants are getting tight and I can rest easy with less work to do on my car.
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Old 12-03-2008, 11:18 AM   #18
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Quote:
Originally Posted by hustler View Post
you have the .86 turbine housing?

If yes, then my pants are getting tight and I can rest easy with less work to do on my car.

yes, he has a 2860 .86 on a stock 1.6L.





this was with his chewed up wheel too.
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Old 12-03-2008, 11:22 AM   #19
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I have the Gt2860Rs .86AR and I'm at 12 psi by a tick after 3,500rpm. S4 manifold through.

The spark map will help out tremendously.
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Old 12-03-2008, 11:26 AM   #20
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thanks brain. I guess I need to get the car tuned, then cry like a ------. I'm going to snug up the wastegate.

Is there any chance that adding a little 3psi wastegate would help spool, and not overboost?

Quote:
Originally Posted by pschmidt View Post
I have the Gt2860Rs .86AR and I'm at 12 psi by a tick after 3,500rpm. S4 manifold through.

The spark map will help out tremendously.
cool. This motor should be blowing the tires off then.


Time to get the miata and drop it off at the dyno. Damn business travel job, lol.
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