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Discussion Starter · #1 · (Edited)
Welcome!
One thing I've noticed in common with those of us who want more than what the stock car offers, is that picking the right turbo can be tough!
There's quite a few to choose from, and it can be a hard decision to pick the one that suits your goals and style.

Well, not anymore!
I too have been on this quest, and armed with the evils of mathematics, engineering, and Excel, I have put many turbos through the numbers!
I will show you how each turbo's compressor matches the engine under the same ideal conditions, discuss the turbine side and exhaust housing capabilities, and as an added bonus will apply my knowledge of the ST platform to each turbo to explain my thoughts on match.

Below you will find mostly compressor maps laid against a bunch of straight lines. Each line represents a set RPM, and it will show you how as the pressure rises at that RPM, just how much air the engine will ingest under its ideal operation. We plot these lines against the compressor maps to get an idea of how each turbo will respond, how much airflow we can get for a given RPM from that turbo, and more!

Remember, this is all idealized. Real world performance will vary with conditions greatly!
For the horsepower estimates, I built a model based on how much horsepower the 2.0 Ecoboost makes for the amount of fuel injected at a given airflow. It's a rough estimate, but will give you a good idea of potential power from each turbo. Optimal is projected from where efficiency is at, and maximum horsepower is if you're pushing the turbo to it's limit. (which also means that the engine is built to match it, which is not going to be the case if you just strap on one of the big turbos!)

Let me know if there's other turbos that you have compressor maps and data for and would like compared, and I'll try to get it on the list and discuss it.
Expect for this guy to be edited and updated for formatting and content purposes!

Test Conditions
Ambient Temperature: 85*F
Ambient Pressure: 14.70 psi
Volumetric Efficiency: Matched to an educated estimated calculation for each RPM for the 2.0 Ecoboost
Intercooler Efficiency: 100%

How conditions effect these charts:
ConitionIncreaseDecrease
Ambient TemperatureTighter grouped lines - Air is less denseExpanded lines - Air is more dense
Ambient PressureExpanded lines - More air for same pressureTighter grouped Lines - Less air for same pressure
Volumetric EfficiencyExpanded lines - More air for same workTighter grouped - Less air for same work
Turbine A/RWorse VE down low, Better VE up top - Line spacing gets larger as you move right on the chartBetter VE down low, Lower VE up top - Line spacing gets smaller as you move right on the chart
Backpressure (pre and post-turbo)Tighter grouped lines - Decreased VEExpanded lines - Increased VE
Intercooler EfficiencyExpanded lines - Cooler, denser airTighter grouped lines - Warmer, less dense air
Intercooler Pressure DropLess manifold pressure - Less airflowMore manifold pressure - More airflow

Garrett Turbos
GT2860RS
GT2860RS.png
Estimated Spool:
- 20psi @ 2600-2800RPM
Maximum Airflow @6500RPM of 36lb/min
Optimal WHP: 300
Maximum WHP: 335

This guy is nice and small, and is a classic turbo for 2.0L engines that want a solid 300whp. Spool should be quick, but it wont be quite as quick as the rotating mass is higher than a comparable GTX based wheel of similar size. This wheel isn't design to flow much more than about 23psi of boost, and you should be able to hit the choke region of the map up top. Would make an excellent AutoX turbo, as the response should be top notch with plenty of power for knocking over cones. No fueling upgrades will be required to max this turbo out.
If you look closely, the GTX2860R basically fits on top of this map, but the wheel on this guy is heavier and can't operate at as high of pressures, so you can't expect it to spool quite like the GTX. This guy is cheaper than the GTX however, and makes a great turbo for people wanting an easy path to 300whp.

GTX2860R
GTX2860.png
Estimated Spool:
- 20psi @ 2500RPM
- 25psi @ 2800RPM
Maximum Airflow @5500RPM of 40lb/min
Optimal WHP: 325
Maximum WHP: 375

Looking at the GTX2860R, we see it's a pretty good match for solid midrange. Spool would be quick, and efficiency through the 3-5k RPM range would be in it's prime in the 25psi range.
A noticeable downside is boost will have to taper off after 5.5k RPM to prevent choke and turbo overspeed conditions.
You could expect to get a solid 340whp out of this without issue, and a decent amount of torque down low would be available. This would work well with the stock fuel system and shouldn't require any fueling upgrades.

GTX2863R
GTX2863.png
Estimated Spool:
- 20psi @ 2800RPM
- 25psi @ 3000RPM
Maximum Airflow @6500RPM of 43lb/min
Optimal WHP: 340
Maximum WHP: 400

First thing you should notice, is a good majority of the lines lie within the compressor map. That means this turbo is a great fit for the engine! I'd expect this to drive very similar to the GTX2860 with just a slight spool penalty. Things to note: the efficiency is excellent on this turbo in the midrange, and that means great mid range torque and power. And for the operating conditions above, this guy hits its peak right at red-line! It shouldn't be too difficult to get a solid 355-360 out of this, and if you really pushed it hard and had good supplementary fuel and supporting mods, you could get darn close to 400whp. On the stock fuel system, this guy will push it right up to the edge in its optimal range.

GTX2867R
GTX2867.png
Estimated Spool:
- 20psi @ 2950RPM
- 25psi @ 3300RPM
Maximum Airflow @7000RPM of 47lb/min
Optimal WHP: 370
Maximum WHP: 430

The bread and butter turbo for this car. This turbo is really a mid-high range kind of turbo. This would be an excellent street turbo, with decently quick spool, and plenty of airflow up top. One thing to note is this guy will really be on the limits of stock fueling with pump gas, and to really push it, you'll want some supplemental fueling to take full advantage of the setup. If you're not pushing it, this compressor wheel is very efficient, and as such will do a great job at generating torque from 3k RPM as high as the stock air flow will go. Up top (on the right of the graph) you can probably expect the lines to squeeze together more than I'm demonstrating as the integrated exhaust manifold could start to become a bottleneck in that area.

Honorable Mention: GTX3067R

This guy has the same compressor map as above, but it has a larger turbine side. This means less back pressure which will help high end flow, but you'll lose spool off the bottom end. On a stock head car, this turbo will probably not garner you any benefit up top to make up for the spool loss, and as such, it takes a backseat to it's little brother, the 2867.

GTX3071R
GTX3071.png
Estimated Spool:
- 20psi @ 3600RPM
- 25psi @ 4000RPM
- 30psi @ 4500RPM
Maximum Airflow @7000RPM: 55lb/min
Optimal WHP: 420
Maximum WHP: 515

Now we're jumping up into the realm of large turbos for a 2.0! Spool is obviously slower now, and you definitely will have a narrower powerband. If you're after power though, you've come to a good place! If you decide to cap it at about 25psi, it'll hold it all the way as high as you want to go, but don't expect to get much past 40 lb/min and 400hp. To really benefit from this turbo you'll definitely want all the supporting mods that go with it, and you'll want to crank that boost up to 11. At 32psi and 7000RPM, you could expect 500whp out of this turbo if you have the fueling to match. The stock headifold will definitely be holding back your top end when you start raising the boost. While I've plotted the lines straight here for simplicity, they really should start curving up as you go higher in boost as the stock head will simply be too restrictive for this. Definitely plan to be making use of extra fueling, getting some good headwork and possible upgrades to increase your red-line capabilities if you really want to take full advantage of this turbo. Do not pick this turbo if you LIKE how the stock car responds and drives. This will definitely have a more traditional high HP, low displacement turbo feel, and simply can't have the response the stock car does down low.

GTX3076R
GTX3076.png
Estimated Spool:
- 20psi @ 3900RPM
- 25psi @ 4500RPM
- 30psi @ 5100RPM
- 35psi @ 5300RPM
- 40psi @ 5500RPM
Maximum Airflow: 63lb/min @ 7000RPM
Optimal WHP: 520
Maximum WHP: 620

There's a reason this is currently the largest kit offered turbo you'll see. It's big. It'll spool slow. You'll definitely want fueling upgrades, all the bolt-ons, and everything else that comes with it. Yes, it'll take time to spool, but once it does, engage VT 3rd gear mode and hold on tight. You will need to plan for some work to really take advantage of this turbo, as you'll want to push it up into the high 30s low 40s PSI to use it with stock red-line. Hence, I'd actually recommend planning to rev higher and to try to build for it, so you can run a lower pressure to get the same power output. Do not pick this turbo if you want great torque down low. It's the complete opposite of that. This guy is all about downshifting, flooring it, holding on tight, and commencing lift off. Be prepared to upgrade to take advantage of this bad boy.

GTX3582 - The "Why Don't They Make Kits For Bigger Turbos?" turbo
GTX3582.png
Estimated Spool:
- Eventually. (5000 RPM)
Maximum Airflow: More than you can handle guy.
Optimal WHP: ?
Maximum WHP: 750

This guy is a bad match for the engine in the car. There really comes a time when you simply need more displacement. There is no replacement. A larger engine pulls more air in, and spreads the lines out, and we need it bad here.
To run this turbo you have basically two choices: Increase your displacement or increase your red-line. Your response will suck low end. Your spool will be measured in minutes. You'll be competing with jet engines for who can take off first. But like a jet engine, if you were built to rev higher (which would mean more lines onto the right side!) you could hit 750ish WHP with this bad boy. That's a fast freaking car. It's also going to be near impossible to really enjoy driving it on the street.
So, small market (basically just drag strip people!), small demand = No kits for this guy, or anything bigger.

BorgWarner Turbos
EFR6258
EFR6258.png
Estimated Spool:
- 20psi @ 2400RPM
- 25psi @ 2600RPM
Maximum Airflow: 44lb/min @ 6500RPM
Optimal WHP: 340
Maximum WHP: 400

This guy can spool! The response on this turbo will basically be almost stock like, but the torque and power potentials are much, much greater. In comparison to the GTX turbos, we win in spool and airflow range, but we lose in efficiency and price. The 6258 is not as efficient, which is probably why it has a greater range of flows, but if you have a good intercooler up front, it shouldn't make too much difference. This guy can flow extremely well up top, and if you really push the speeds up, you could get close to the 400whp mark. Like the GTX2860 though, it's clear that this guy would be happiest in the midrange, and would make for an excellent driving car or track car.

EFR6758
EFR6758.png
Estimated Spool:
- 20psi @ 2800RPM
- 25psi @ 3300RPM
Maximum Airflow: 48lb/min @ 6500RPM
Optimal WHP: 380
Maximum WHP: 450

Definite competition for the GTX2867! Spool is better, and top end flow should be better as well. Yet again though, it comes at the cost of efficiency, which this turbo is comparatively poor on compared to the GTX2867. It's still not something I'd consider "bad" at all though, and again, I think just having an upgraded intercooler will handle any loss in compressor efficiency. This is another excellent choice for someone who wants a driveable car, but wants to pack a punch.

EFR7163
EFR7163.png
Estimated Spool
- 20 psi @ 3000-3100RPM
- 25 psi @ 4000RPM
Maximum Airflow: 61lb/min @7000RPM
Optimal WHP: 450
Maximum WHP: 575

Now we're flowing! The first thing you should notice is this compressor map has a nice fat range of airflows. Combined with its lightweight turbine side, this guy can spool quicker than the comparative GTX30 series turbo, while giving airflow in the similar neighborhood. The efficiency ranges are perfect for high RPM power, and it will definitely outflow the stock fuel system. Another benefit is the compressor matches the engine a bit better than the GTX's as well, so you shouldn't need to increase the redline drastically to use its full potential flow.
A great competitor to the GTX30 series, but like other BW vs Garrett setups, the difference is in price and in peak efficiency numbers.
 

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Edit: I swear there was a post asking about turbos from dsm's and evos. Lmao. I think the 16g from the dsm's flows about the same as our stock turbo, but I do remember it holding boost to redline when I had that turbo. I even remember people having trouble with boost creep with the internal wastegate lol.

I made 275whp with the 16g.


Bugasu, thanks for putting that together. I'm sure it'll help people (including myself) choose the proper turbo for our own application.
 
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holy **** this is probably the greatest thread ever. now, none of those graphs mean anything to me since I dont understand what I am looking at, but the explanations below put it perfectly. nice thread and thanks for the hard work sir!
 
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Excellent write up as always. This should be a sticky! If I may add a few things from personal experience and to help people with the power output expectations.

The above is excellent at comparing turbos. However when choosing a turbo and expecting a power output there are two other important variables other than what the turbo can flow.

1. Fuel octane. This will greatly affect how much power you can safely make. On 91 octane California fuel the turbos on the smaller end of that scale will struggle with 300whp and the bigger ones will get you 320whp or so before knock becomes an issue. With 93 octane a 2867 will sit around 350-360whp before most setups become knock limited. Use of e85 can push this further but plan on fuel system upgrades as the turbos will quickly outflow the oem system. WMI is also a great option and it adds to cooling, octane, and fueling.

2. The flow efficiencies of the motor and intake and exhaust will start to play a role in what a turbo can do. Bugasu touched on this but just to give you an idea the GTX3076 is not a 600whp turbo on this car in most setups. It is much closer to 500whp when pushed to the limit because the inefficiencies of the motor start to have a larger effect on the overall power output.

One more thing to keep in mind which is mentioned about is that compressors are very sensitive to temperatures and barometric pressure. The graphs above are charted at a standard temperature and pressure. Going hotter and at higher altitudes will drop the efficiencies and flow capacities down. The opposite will increase them. This is why you see the bigger dyno numbers being made in the dead of winter at sea level.
 

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Also Bugasu if you get the chance throw the EFR 7163 up on there as well. It's a good on the larger side turbo but the lightweight turbine can make it a faster spooler than a GTX3076.
It would be interesting to run an ST with the same build as mine but with the EFR.

I also agree with your statement about actual whp capabilities when compared to the stock head. I picked the GTX3076r based off a quick calculation and ended up on the 71% island. Of course we will be using a higher redline and my PI-WMI setup, not to mention once SP63 finishes their prototype G-PI setup we will see where that can take me without an aggressive w/m mixture
 

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Thanks Bugasu for this great write-up, it is very helpful. Please consider adding the stock K03 for comparison as I think that would also be helpful to see differences.
 
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Discussion Starter · #11 ·
Excellent write up as always. This should be a sticky! If I may add a few things from personal experience and to help people with the power output expectations.

The above is excellent at comparing turbos. However when choosing a turbo and expecting a power output there are two other important variables other than what the turbo can flow.

1. Fuel octane. This will greatly affect how much power you can safely make. On 91 octane California fuel the turbos on the smaller end of that scale will struggle with 300whp and the bigger ones will get you 320whp or so before knock becomes an issue. With 93 octane a 2867 will sit around 350-360whp before most setups become knock limited. Use of e85 can push this further but plan on fuel system upgrades as the turbos will quickly outflow the oem system. WMI is also a great option and it adds to cooling, octane, and fueling.

2. The flow efficiencies of the motor and intake and exhaust will start to play a role in what a turbo can do. Bugasu touched on this but just to give you an idea the GTX3076 is not a 600whp turbo on this car in most setups. It is much closer to 500whp when pushed to the limit because the inefficiencies of the motor start to have a larger effect on the overall power output.

One more thing to keep in mind which is mentioned about is that compressors are very sensitive to temperatures and barometric pressure. The graphs above are charted at a standard temperature and pressure. Going hotter and at higher altitudes will drop the efficiencies and flow capacities down. The opposite will increase them. This is why you see the bigger dyno numbers being made in the dead of winter at sea level.
I will try to get that added in more. I realize right now everything sits in idealist land, so I will try to bring some realism back in. I have a lot of these saved off in separate sheets. I really should stress the fueling limitations to power better!
I'll try to get some supplementary charts made :)

Also Bugasu if you get the chance throw the EFR 7163 up on there as well. It's a good on the larger side turbo but the lightweight turbine can make it a faster spooler than a GTX3076.
Will do! I'll also try to get some turbine information included, as it's very important to discuss how it contributes!
 

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@Bugasu even the GT2860 spools a little slower than some of your calculations. It hits 20 psi @ 3000 rpm. @[email protected] this is a basline dyno on 91 piss gas temp was 70 degrees and at 980ft above sea level. As you can see in the dyno graph it started pulling timing after 5500 rpm but over 300 whp.

001.jpg
 

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Also Bugasu if you get the chance throw the EFR 7163 up on there as well. It's a good on the larger side turbo but the lightweight turbine can make it a faster spooler than a GTX3076.
I too was looking for that, I recently purchased a 6758 and right after I started reading about the 7163, and it's been stirring in my head since.

Edit- @Bugasu Awesome write up by the way :)
 

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Discussion Starter · #14 · (Edited)
@Bugasu even the GT2860 spools a little slower than some of your calculations. It hits 20 psi @ 3000 rpm. @[email protected] this is a basline dyno on 91 piss gas temp was 70 degrees and at 980ft above sea level. As you can see in the dyno graph it started pulling timing after 5500 rpm but over 300 whp.

View attachment 78747
My estimate is for the GTX, which has the newer compressor wheel, and a nice turbine side. I havent yet done any of the GT wheeled items.
I've already had a request for that guy, so I'll get her plotted up!

My estimates also take into account that the turbine side can actually push what the compressor can do.
This may require VE tweaking and some work.

For example, most people on the 2867 dont see 20psi until 3500, but @[email protected] has shown it to be capable at 3000RPM.

I will try to add more turbine side discussion in to help clear this up!
 

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My estimate is for the GTX, which has the newer compressor wheel, and a nice turbine side. I havent yet done any of the GT wheeled items.
I've already had a request for that guy, so I'll get her plotted up!

My estimates also take into account that the turbine side can actually push what the compressor can do.
This may require VE tweaking and some work.

For example, most people on the 2867 dont see 20psi until 3500, but @[email protected] has shown it to be capable at 3000RPM.

I will try to add more turbine side discussion in to help clear this up!
The exhaust configuration, temperature, gear, and when you went WOT have a big effect on spool. In 40*F temperatures I can get my GTX2867 to hit 20psi right at 3000 RPM with spool optimizations on the tune in 4th gear going WOT at 2500 RPM on a catted downpipe.
On a catless setup this can be dropped to 2900 RPM with the same variables as above.

In 6th gear this can be further decreased - I estimate we can get it down to around 2800 RPM for 20psi.

There are many variables to consider and I think @Bugasu's synopsis in this thread is spot on. It is meant to compare the turbos in a normalized fashion (keeping variables the same) with the knowledge that car setup, fuel, and environmental variables can shift the results around for a particular car.
 

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Discussion Starter · #16 ·
@Bugasu even the GT2860 spools a little slower than some of your calculations. It hits 20 psi @ 3000 rpm. @[email protected] this is a basline dyno on 91 piss gas temp was 70 degrees and at 980ft above sea level. As you can see in the dyno graph it started pulling timing after 5500 rpm but over 300 whp.

View attachment 78747
I'm just finishing up my estimates for this turbo setup.
I'm really at a loss for why your spool is so late. Even with the heavier wheel in the GT series, I'd expect this guy to spool much more rapidly than what you are seeing. 3000RPM is well within the map. You should be able to spool around 2200-2500 RPM with that turbo.

Do you have ambient pressure and temp or some logs for your setup? Using the test conditions I listed previous, that boost you're running up top pushes the turbo well into the choke region, so I'd expect you to be spinning the turbo quicker than recommend. I'd be interested in RPM vs Boost & Airflow, as well as Baro and Temperature at the time.
 

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Discussion Starter · #17 · (Edited)
Also Bugasu if you get the chance throw the EFR 7163 up on there as well. It's a good on the larger side turbo but the lightweight turbine can make it a faster spooler than a GTX3076.
Okay have you plotted this one out? I think I scaled the map correctly but almost can't believe the range this turbo has...
20psi would be right near the surge line @2500RPM, (so with a small A/R housing you could probably hit it at 3000RPM with ease) but it can flow 60lb/min?

I must've screwed up... Cause that's awesome and way better than the the 6758 in my opinion.
 

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The nicest part about the Focus is that you have a decent set of choices. Any FWD car I have built I always wanted full spool higher. The only reason for this was to limit blowing the tires off at the low end. Some of you I am sure have built many cars and experinced this. But that was my preference. At that track it was not a issue. But if your building a car to roll race top end is your best friend.

Thanks
John
 
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