GT2871R Anti-Surge Option???

[MadScientist]

So yes... I am looking at getting the GT2871R and have been searching around to several places. And Yes... I have done alot of searching on this forum (not a newb)!!

I like the response of the .64 trim but I believe the .86 is more of what I am looking for.

While searching I ran across this... Anti-Surge Machined Inlet!!!
http://www.atpturbo.com
http://www.atpturbo.com/Merchant2/graphics/00000001/Catalog%20Images/Turbochargers/anti-surge-option.jpg
This may be a mistake on the site... it looks like the GT2876R inlet... but its not an option for the GT2876R...!?!

This option alone is what is going to seal the deal on this or any of the similar sizes.

Are any of you GT2871R guys using this option??
Thoughts???

-Drew

[McRussellPants]

Nah thats a 71 E Frame cover.

2871 doesn't surge on SR20s unless something is severely wrong in your tune, like exhaust glowing red at 2k wrong in the tune. (no its not so you don't have to run a blow off valve)

all it would do is make your turbo come up about 200rpm later.

2871 .86 is pretty dumpster dive. I'd run a 3071WG with a .63 before a 2871 .86

[MadScientist]

hrmmmm...
So this is a True option.... nice.
.86 is about 200rpm loss + the Anti Surge would add another 200rpm loss?? ouch!!

I have a Tomei Mani so I am trying to stick with T2 Flanged Turbos... Im not liking the uber small wheel on the T2 3071..

I may just go with the Anti Surge on the GT2871R .64!
still not 100%
I do want a reliable 400+whp
and would like to keep the RPMs below the 4000 mark.
also the clutch is not stock... its an OS Giken STR Twin... its about 33lbs.
Considering Rotaional Mass and other goodies... Im not sure if 400 is going to be possable on the GT2871R (for me)...

-Drew

[Def]

Why do you want an anti-surge housing? It is not needed in the slightest for an SR20 on any of these turbos.

[McRussellPants]

We're getting precision to do a pair of 2871 3in inlet ported covers for a guys RB26.

But the only reason to buy these is they're louder, they're total rice points

[S14DB]

http://www.atpturbo.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=GRT-TBO-036&Category_Code=VSR2

[idahotuner]

just get an HKS SSQ bov. and you will have no worries about surge on your turbo.

[MadScientist]

WOAAAAHHHH!!

You guys have taken a simple question and took it as a slap in the face.

I understand I dont need a Surge Ported Turbo for the SR20.... Thank you McRussellPants.
However... the reason I am looking to lag the RPM is to prevent it form running out at 8000rpm. Also Surge Porting is not JUST for Surge... it prevents turbulance in front of the compressor wheel.... so I really dont see how it would have extra lag. I know the turbos I am about to list are bigger but that doesn't matter, right... the HKS GT2835 Pro is Surge Ported and I have always loved it, Its also used on the HKS D1 S15. Yashio Factory uses a Surge Ported GT3037 Pro on on their S15. So what am I missing... because I really doubt its just for rice points!!!

everyone else :wtf:
You totally missed the part where I am Not 100% Sold on ANY Turbo YET!!!
Its just a question... I know that Zilvians would rather flame and bash.. then be intelectual and answser the question.

idahotuner - I have a Blitz DD

-Drew

[chaseSR86]

I have a 2871r .64 with the 3" inlet design not the t28 nissan compressor design. I have a 50mm tial BOV it surges some beacuse I have a super stiff spring in the BOV.
I think if you were looking for RELIABLE 400whp you'd want an externally gated 3071r .63.

Your power really comes from your turbine. I think that 4" anti surge compressor would be beneficial for a larger engine in compared to a sr. I dont know however I dont think you'd see much response added with the anti surge compressor on an SR. especially if you went with a .86 housing.

[MadScientist]

I have a 2871r .64 with the 3" inlet design not the t28 nissan compressor design. I have a 50mm tial BOV it surges some beacuse I have a super stiff spring in the BOV.
I think if you were looking for RELIABLE 400whp you'd want an externally gated 3071r .63.

Your power really comes from your turbine. I think that 4" anti surge compressor would be beneficial for a larger engine in compared to a sr. I dont know however I dont think you'd see much response added with the anti surge compressor on an SR. especially if you went with a .86 housing.

^^^ good info but I already have a Tomei Mani (T2 twin scroll)
I have considered the GT3071R but many of the JDM T3 manis dont work on LHD and the Full Race Twin Scroll T3 doesn't work with AC... I live in New Orleans... need I say more! I really reall really dont feel like dealing with a custom fab.

IF I went with the E-Frame I would deffinatly get the .64!!

-Drew

[McRussellPants]

You Guys,

jesus.

Antisurge is a controlled boost leak to keep the turbo from spooling fast enough to run into surge.

SRs WILL NEVER HAVE THIS PROBLEM EVER.

it doesn't help response

it has nothing to do with closed throttle surge.

On an SR the only thing it does is hurt spool and sound cool as fuck.

you don't need it, you can get 4in covers without it.

4in inlet on a bottom mount would be a hooker. Just get the OEM replacement 2871 52Trim, the compressor map is better on the 52 Trim anyway.

[Def]

Anti-surge reduces turbulence on the compressor face? I find that VERY hard to believe. If anything it will increase turbulence by disturbing streamlines about 1-1.5 diameters upstream of the wheel face.

Like McPanties said, it's just a fixed area boost leak at a PR somewhere between the actual inlet/outlet PR of the compressor since you're part of the way down the wheel in most cases.

[Z U L8R]

if ur turbo's runs out of steam before redline then your turbine housing is too small. however if you go with the bigger housing then you're going to effect spool. nitrous always helps spool time tho @[email protected] haha

stock bottom end sr /w bc 264 cams gt28/71r .84 made [email protected] on our mustang dyno last month. we told him not to go over 14psi unless he used race gas since it's cheaper than a bottom end. he wouldn't listen (they never do). he really wished he had the smaller housing, but fwiw at 15psi he was making 372rwhp. it hit hard at 4k /w power fc.

what are your hp goals?

i agree with russel on the no need for anti-surge on that small of a turbo.

on a side note russel i'm still doing the math to plot out the beast for the ka-t

gt40/88 has a good graph but i heard precision offers a gt40/76r rendition lol, not trying to thread jack, hope that helps OPer

Dave =]

[chaseSR86]

^^^ good info but I already have a Tomei Mani (T2 twin scroll)
I have considered the GT3071R but many of the JDM T3 manis dont work on LHD and the Full Race Twin Scroll T3 doesn't work with AC... I live in New Orleans... need I say more! I really reall really dont feel like dealing with a custom fab.

IF I went with the E-Frame I would deffinatly get the .64!!

-Drew


The tomei manifold is not twin scroll dude, it has the runners backwards.... Its just a stock manifold thats chromed for bling. its crap. Its not even flow engineering like a FR mani. Look at the runner design.

I think you should reconsider your HP goals with the 2871R. You only have 2 options with that turbo.

.64 faster spool less top end. 380HP reliably.

.84 less spoolage, less response. more top end 400HP.


Your compressor housing isn't going to give you more HP. Its going to give you or take away response.

[steve shadows]

I would go .63 3071R Hands down.

[GabeS14]

hrmmmm...
I do want a reliable 400+whp
and would like to keep the RPMs below the 4000 mark.
also the clutch is not stock... its an OS Giken STR Twin... its about 33lbs.
Considering Rotaional Mass and other goodies... Im not sure if 400 is going to be possable on the GT2871R (for me)...

-Drew

Yea I dont think the 2871 R is gonna gie you 400hp under 4000 rpm, I have the same one,
2871R-(11)with 64 trim,
850cc inj
greddy intake mani
megan exhaust
3" straiht pipe
jim wolfe tune
HKS ssq bov
fmic
and most of the power comes withing 4800-6k rpm mark..
it jumps all of a sudden when reaches 4800rpm
so i dont thing 400 hp is possible..i would def get the hks 2835

[steve shadows]

I have a 3076R TUNED ON A DYNO PROPERLY by me of course

I get 18 psi by 4k, Torque starts to come up hard at 4500 rpms (320-340ft lbs at the wheels on 91 octane)

Thats with a larger plenum, T04 S housing and 264 STEP 2 cams.

It's all in the tuning.

[idahotuner]

i am suprised cody ace asnt stepped in and given his words on this topic.

i basically copied his set up. which got him to 400 reliable RWHP on the gt2871 .64. i only havea few things different. lieka tubular manifold. and a enthalpy tune instead of a JWT tune.

[MadScientist]

You have all Failed to produce Fact based info to validate your claims.

I understand and agree that the SR20 doesn't produce high HP # with the GT2871R to create damaging surge.
BUT... what else does the surge porting do to/for the GT2871R??

http://www.turbobygarrett.com/turbobygarrett/images/tech_center/tech_103/enlarged_Images/tech103_enlarges.gif
◊ Mass Flow Rate
Mass Flow Rate is the mass of air flowing through a compressor (and engine!) over a given period of time and is commonly expressed as lb/min (pounds per minute). Mass flow can be physically measured, but in many cases it is sufficient to estimate the mass flow for choosing the proper turbo.
Many people use Volumetric Flow Rate (expressed in cubic feet per minute, CFM or ft3/min) instead of mass flow rate. Volumetric flow rate can be converted to mass flow by multiplying by the air density. Air density at sea level is 0.076lb/ft3
What is my mass flow rate? As a very general rule, turbocharged gasoline engines will generate 9.5-10.5 horsepower (as measured at the flywheel) for each lb/min of airflow. So, an engine with a target peak horsepower of 400 Hp will require 36-44 lb/min of airflow to achieve that target. This is just a rough first approximation to help narrow the turbo selection options.
◊ Surge Line
Surge is the left hand boundary of the compressor map. Operation to the left of this line represents a region of flow instability. This region is characterized by mild flutter to wildly fluctuating boost and “barking” from the compressor. Continued operation within this region can lead to premature turbo failure due to heavy thrust loading.
Surge is most commonly experienced when one of two situations exist. The first and most damaging is surge under load. It can be an indication that your compressor is too large. Surge is also commonly experienced when the throttle is quickly closed after boosting. This occurs because mass flow is drastically reduced as the throttle is closed, but the turbo is still spinning and generating boost. This immediately drives the operating point to the far left of the compressor map, right into surge.

Surge will decay once the turbo speed finally slows enough to reduce the boost and move the operating point back into the stable region. This situation is commonly addressed by using a Blow-Off Valves (BOV) or bypass valve. A BOV functions to vent intake pressure to atmosphere so that the mass flow ramps down smoothly, keeping the compressor out of surge. In the case of a recirculating bypass valve, the airflow is recirculated back to the compressor inlet.

◊ The Choke Line is the right hand boundary of the compressor map. For Garrett maps, the choke line is typically defined by the point where the efficiency drops below 58%. In addition to the rapid drop of compressor efficiency past this point, the turbo speed will also be approaching or exceeding the allowable limit. If your actual or predicted operation is beyond this limit, a larger compressor is necessary.

◊ Turbo Speed Lines are lines of constant turbo speed. Turbo speed for points between these lines can be estimated by interpolation. As turbo speed increases, the pressure ratio increases and/or mass flow increases. As indicated above in the choke line description, the turbo speed lines are very close together at the far right edge of the map. Once a compressor is operating past the choke limit, turbo speed increases very quickly and a turbo over-speed condition is very likely.

◊ Efficiency Islands are concentric regions on the maps that represent the compressor efficiency at any point on the map. The smallest island near the center of the map is the highest or peak efficiency island. As the rings move out from there, the efficiency drops by the indicated amount until the surge and choke limits are reached.

http://www.turbobygarrett.com/turbobygarrett/images/tech_center/tech_103/enlarged_Images/Fig2_enlarges.gif
A Ported Shroud compressor (see Fig. 2) is a feature that is incorporated into the compressor housing. It functions to move the surge line further to the left (see Fig. 3) by allowing some airflow to exit the wheel through the port to keep surge from occurring. This provides additional useable range and allows a larger compressor to be used for higher flow requirements without risking running the compressor into a dangerous surge condition. The presence of the ported shroud usually has a minor negative impact on compressor efficiency.
http://www.turbobygarrett.com/turbobygarrett/images/tech_center/tech_103/enlarged_Images/fig3_enlarged.gif

I know this is off a GT45... not a GT2871R!!!
But I am using this to provide info for better FACTS!! not Opinions!!

Your compressor housing isn't going to give you more HP. Its going to give you or take away response.

Exactly!!!! Does it Give... or Take!!??!!
Does this Option produce a Middle Ground between the .64 and the .86??

[GabeS14]

Well you asked for opinions, from the guys who have or have used the same turbo, and you got that.
I think even though it wasn't factual most of the info you got here was very true.
the 2871R as a few here have stated is not that big of a turbo for you to have to worry about all this surge.. its not that much..

some guys dont even run bov..

[MadScientist]

Well you asked for opinions, from the guys who have or have used the same turbo, and you got that.
I think even though it wasn't factual most of the info you got here was very true.
the 2871R as a few here have stated is not that big of a turbo for you to have to worry about all this surge.. its not that much..

some guys dont even run bov..

SURGE SURGE SURGE..... un-wrap your heads from around that.

what else does the surge porting do to/for the GT2871R??
Does it Give... or Take!!??!!
Does this Option produce a Middle Ground between the .64 and the .86??

I believe those are the questions that are not being answered!
:bigok:

[GabeS14]

SURGE SURGE SURGE..... un-wrap your heads from around that.

what else does the surge porting do to/for the GT2871R??
Does it Give... or Take!!??!!
Does this Option produce a Middle Ground between the .64 and the .86??

I believe those are the questions that are not being answered!
:bigok:

I see..
but I dont think many people on here, bothered to get that option, since it isnt extremely necessary..
thats why you havent gotten the exact answers you were looking for..
just try it out man, cant hurt..
i would love to know your personal opinion on it after trying it..

[slider2828]

Also besides looking at the HKS GT PRO line, please also look at Power Enterprise IHI turbines. IHI is the premier line of turbos as most of the drifters and racers use this turbo. Its cheaper and has great characteristics. Power Enterprise kits all come with IHI turbines....

[McRussellPants]

Exactly!!!! Does it Give... or Take!!??!!
Does this Option produce a Middle Ground between the .64 and the .86??

What

The

Fuck

Are

You

Talking

About.

I told you 5 fucking times it moves boost threshold back about 200rpm. doesn't affect surge at all because the SR won't run in that part of the map and the only effect it has will be making your intake louder.

do you even realize that some engines will spool fast enough to get across the surge line? do you realize thats all anti surge is for and its completely worthless for closed throttle surge.

If you want to fucking buy it do it, but thats how its gonna be. It won't make more power over a 4in cover and it will spool later.

Louisiana, bad at cars, now and forever. fuck.

[McRussellPants]

some guys dont even run bov..

Thats

Not

What

Anti

Surge

Is

For.

[MadScientist]

McRussellPants - You Failed to produce Fact based info to validate your claims... I found info and posted it so it can be reviewed BY ALL... that is the purpose of a Public Forum.

I looked on this forum and FA about this... nether had Any info at all.
Now... everything is posted in one place and if there is any other questions... its easy to find!!!

I did make this personal when speaking about My HP Goals.. I see how that got off track a bit.

Thought Steve Shadows would have gave more input... but Yes... I am more interested in the GT3071R-WG

-Drew

[GabeS14]

McRussel has an online "attitude" dont you think?
respect is appreciated..
just make sure you have that attitude when you tak to people face to face,..you will live a long life!

[McRussellPants]

just make sure you have that attitude when you tak to people face to face,..you will live a long life!


You guys are gonna beat me up because you don't know how turbos work?


sounds cool, whats it all about?

[GabeS14]

You guys are gonna beat me up because you don't know how turbos work?


sounds cool, whats it all about?

I dint say anyone would beat anyone up..lol..for all i know you could be Chuck liddell!

I am saying treat people online just like you woudl treat them in person,
I highley doubt you would walkup to a random guy, who just said something wrong, and treat him like he was a little kid..or an idiot..It probably wouldnt work out to well.

its all good man, just keep the convo going without turning it into a bickering session you know?:ughd:

[Z U L8R]

in turbobygarretts explanation it talks about crossing the surge threshold when a turbo's too big for the application. obviously a t2 frame turbo is not too big for an sr20. it does not cross the surge threshold. therefore that is the FACT on a anti-surge housing for a gt28r. it's not needed. the anti-surge housing is to a gt28r as the big H sticker is to an old honda accord.

u just posted up the answer to your own question. go to the website you posted (turbobygarret) and do the equations in "turbo 103" and plot how much absolute pressure you'll need to reach your horsepower goals at your volumetric engine's efficiency. then plot it just like they do at lower rpms and see if you're passed the surge line of ANY of the gt28/71r's. then you will have all the evidence in which you seek.

i can see if the people that responded to your thread were morons with red reps, but if you think i waste my time to respond to your post so i can talk out of my ass with no clue to what i'm talking about then you're insulting me @ OPer

i am kind of frustrated like mcrussell with this. you ask the question, you get the answer, then you ask why is why, then more people answer....then you post up a website that you and all the rest of us knows has that tiny atom of the EXACT INFORMATION YOU WON'T STOP UNTIL YOU GET, but we're still all idiots who don't know wtf we're talking about.

not sure if anyone's said this...but for the record OPer.... you know that when they're offering the turbo in a .63 or .84 a/r , that they're talking about the turbine housing aka hot side, not the compressor side, which is where the anti-surge is...right?

but....anti surge is great, you should get it.

Dave

[GabeS14]

Lol, I guess I misread, a bit in the biginning, i understood he was asking about compressor surge,
kinda stupid I know!
kinda threw me off with the 86vs 64 ar too!
got me confused..
:rolleyes:

[S14DB]

You guys are gonna beat me up because you don't know how turbos work?

Yeah, what MRP has said 3 times doesn't change. You have to understand what compressor surge is to know why you don't need anti-surge. It's like asking a someone about Particle Physics when you have never taken a class in any form of Physics.

Surge line

The slightly kinked diagonal line on the main (i.e. lower) part of the map is known as the surge (or stall) line. Above this line is a region of unstable flow, which is an area best avoided.

A compressor surge, typically, causes an abrupt reversal of the airflow through the unit, as the pumping action of the aerofoils stalls (akin to an aircraft wing stalling).

When the turbo is to big for the motor. It flows more air then the intake system can handle. This air has no were to go except for to back flow out the intake of the turbo. Usually stalling out the turbo and damaging the compressor wheel. Turbo won't spool up, Just try to then "chuff chuff chuff" as it stalls out.

The GT2871R is no were near big enough to outflow even a stock SR. A surge housing is a band-aid to bleed off air before the surge. Like he said earlier a controlled boost leak. You loose compressor efficiency with the housing.



It has NOTHING TO DO WITH HP. It's all about the airflow of the turbo being to big for the intake to handle and the turbo can't spool cause of the imbalance. If you try to cram 10 lbs of crap in a 1lb bag it doesn't matter how big the stick is(turbo), shit's still gonna leak out(surge).



If you like ATP, get the turbo they recommend for the SR.
http://www.atpturbo.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=GRT-TBO-036&Category_Code=VSR2

[GabeS14]

I loved the explanation ..thx S14db.

easier than understanding the chart.
but I have a question, I mentioned before using a BOV, was I wrong?
I though BOV allowed the excess air to flow out, without returning to the intake in a backwards flow..causing comp surge?
pls correct me, I am also still learning. this is just what i have understood so far!

[Def]

When the turbo is to big for the motor. It flows more air then the intake system can handle. This air has no were to go except for to back flow out the intake of the turbo. Usually stalling out the turbo and damaging the compressor wheel. Turbo won't spool up, Just try to then "chuff chuff chuff" as it stalls out.



I guess that's a very rough way of looking at it, but for those that are interested, the technical explanation behind surging is that at high pressure ratios and low mass flows(i.e. spooled up a large turbo early on a small engine) you can actually have the flow go so slowly through the compressor that it detaches from the compressor wheel/blades. This essentially drops compressor flow to almost zero, thus air starts leaking backwards through the compressor wheel. This drops the pressure ratio enough so that flow can reestablish itself through the compressor wheel(reattach to the blades), which builds the PR up slightly, and it all happens again until the engine can accelerate enough to get a high enough massflow where it stops. This all happens really quickly, and it's hell on CHRA bearings.

In a nutshell, it's the aerodynamic stalling of the compressor wheel which prevents a centrifugal compressor from generating pressure/flow.

Note that this is a different process than when you close the throttle and get slight partial throttle surge.

[GabeS14]

I In a nutshell, it's the aerodynamic stalling of the compressor wheel which prevents a centrifugal compressor from generating pressure/flow.

Note that this is a different process than when you close the throttle and get slight partial throttle surge.
Baammm..thanks, thats what I have been asking!

[chaseSR86]

Glad this thread finally got covered correctly.