Turbo Selection Help

[ClintH]

@Enki, specifically, but any other help is welcome, too.

Longtime lurker, first time poster, but I'm wondering if I could get opinions or help pointed in the right direction for what to use when comparing turbos?

I'm trying to narrow down turbo options and it's my first time weeding through all the charts, sizes, A/Rs, features, etc.

Working on a gen2 MS3 project, and the goal is a 500hp street car, so spool, response time, and room under the curve is more important to me than high top-end numbers.

The options on my short list are:
Xona 5557
BW EFR 7163
Turbosmart 5862
G30-660

I'm just not sure what to look for when comparing all the compressor charts, exhaust charts, etc to know what fits my goal best.

Any advice would be appreciated if it's not too much to ask.

Thanks!

 

[Enki]

IMO the 7163 with the SXE comp housing will be top of the list, probably followed by the G30-660. Unfortunately, I don't know much bout the other turbos, but if you have compressor maps and lists of available hotside ARs, that will help.

Also, hotside sizing is a bit of a dark art, with no real info to go off of other than AR and wheel sizes.

G30-660: ~500 WHP

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VashExe made ~500-550 WHP on a standard EFR 7163, and the SXE should flow about 40HP more on the top end as well as nudge spool a touch earlier. Plus the SXE housing has a built in T51R mod:
https://www.youtube.com/shorts/htHJ9hsTYEA

 

[ClintH]

but if you have compressor maps and lists of available hotside ARs, that will help.

Thanks! That's right in the ballpark for what I'm after power-wise.

Here's the compressor maps for the Xona 5557
Available A/Rs: .63, .82, 1.05



And for the Turbosmart 5862:
Available A/Rs: .63, .82,

 

[Enki]

Well the Turbosmart one is going in the bin if you don't want punch and 40+ PSI. Look for wide, not tall turbo maps (compare at flow rates; bottom of graph) and a good rough estimate is 10 HP per Lbs/min of flow (70 = 700). Ideally for response and curve reasons you want your turbo to max out just above your goals, but not too far out as larger turbos with more flow tend to have more mass and thus inertia, slowing spool.

Behold the majesty of the (base, not SXE) 7163:


A pressure ratio of 2.0 is roughly 15 PSI of boost, with 3.0 being 30. An "unreasonable" way to compare maps for curve area is to draw a line from the 2.0 to 3.0 pressure ratios only from within the 70% or higher islands and see how many lbs-flow of lines you get (by 10s).

EFR goes from roughly 22.5 lbs flow to ~51 lbs flow.

The Turbosmart has more area (from ~25 lbs flow to ~72 lbs flow) but take a close look at where the maps start on both the pressure ratio and flow scales and you should see why it's a bad choice.

And the G30-660, who's compressor map is so crushed it's even harder to read than the Turbosmart:

Looking like ~22 lbs-flow to ~58 lbs flow, which means more meat up top, however looking down low it seems spool will be sacrificed but better than the turbosmart.


While you *could* compensate the lack of spool with a smaller AR hotside to force it to spool, it's going to flow choke the engine after it spools, making most of the upper end of the power band unreachable due to dropoff. You can only force so much energy through the hotside, and the rest *must* be vented through the wastegate. Ultimately, the longer you can keep the wastegate closed (or at least, more closed) without overboosting or losing boost at higher RPMs is more ideal than bleeding it off or having flow choke happen.

Inversely, putting a higher AR hotside will generally sacrifice spool, but this is sometimes made up for with the smaller and lighter wheels wanting to spin up faster. Higher AR hotsides also allow for more exhaust flow at higher RPMs and boost/intake flow rates, and allow for a flatter, more controllable powerband once you're at max boost.

That said, this is why I'd go EFR 7163 for a daily driver or higher speed autox car, or the Xona with a 1.0+ AR hotside for high RPM road racing, even if your power goals are lower than what the Xona would be capable of.

It really is hard to beat the black magic Gamma-Ti bullshit that the 7163 uses, others are getting close, but this specific turbo is basically the sweet spot (and made better with the SXE housing).

 

[ClintH]

Thank you a ton! That kind of analysis is exactly what I was missing trying to compare all these. I tried reading some of the articles on Garrett's site, but it seemed really arbitrary. Like, "just make sure the flow rate and pressure you pick are on the map." It wasn't really clicking how to compare two different maps to find the better one.

Just for clarification, though, when you mentioned:

.....take a close look at where the maps start on both the pressure ratio and flow scales and you should see why it's a bad choice.

Are you talking about this point (circled) and the fact the 7163 is starting to work at such low pressure ratio and flow compared to the others?

 

[Enki]

Correct. If my understanding is correct, that corner is basically where the turbo starts to really try to spool, and at a pressure ratio of 1.2, that's basically like 3 psi and about 75 HP worth of flow. Lol

Makes sense that the pressure required drops off a little bit as the airflow increases, as the overall exhaust mass would increase substantially as flow increases. Again though, there are ways around these kinds of things and way too many variables to actually math it out compared to the more reliable (but vastly more expensive) method of "buy it, install it, test it."

Comparing spool via compressor maps and turbine wheel sizes/AR is much deeper into the art of turdblow selection vs the science. Can it be done? Sure. Do you want to do it that way? Probably not.

 

[ClintH]

No doubt it would be impressive to spool that low. If I'm reading @VashEXE 's thread right, the EFR was hitting full boost numbers at 3500rpm, which would pretty much match the boost threshold of the BNR S3 that's on the car now.

Would altitude change any of the calculus at all? I'm at 5,000' in CO. A local speed shop kinda downplayed the EFR for not flowing enough on the top end for this altitude, but I'm wondering if that SX-E option would resolve some of that.

 

[Enki]

Yeah altitude kind of changes things a bit. VashExe was basically at sea level. You could hit up Matchbot and see what your boost levels and pressure ratios would look like on the map though, then add about 40 hp on the top end, give or take, with the SXE housing.

 

[ClintH]

So, might not be doing it right, but looks like the most I could expect is ~26psi at 60lbs/min at 5000ft? That works out to 508hp on their calculator. Adding the 40hp for the SX-E, that's still right in the ballpark for what I'm after.

 

[Enki]

Compressor efficiency should be dropped to 58, and the HP figure is at the crank but yeah.

Figure 500 CHP would be roughly 440 WHP, plus another 40 for about 480 WHP. That's still not bad for 5k elevation.

 

[ClintH]

Yeah, sucks living at altitude sometimes.

What do think of @andale927 's results with the 5558? I think he switched from the 7163, but couldn't really tell from the charts how much slower the Precision spooled.

 

[andale927]

Yeah, sucks living at altitude sometimes.

What do think of @andale927 's results with the 5558? I think he switched from the 7163, but couldn't really tell from the charts how much slower the Precision spooled.

Honestly they were pretty similar, but the 5558 was spooling a little faster by about 200rpm. I think the 7163 gate was opening a little early though and some improvement was possible.

 

[andale927]

I should mention my 7163 kit is actually up for sale haha, I only got around to listing it a couple months ago. Should still be up in the FS section

 

[ClintH]

I should mention my 7163 kit is actually up for sale haha, I only got around to listing it a couple months ago. Should still be up in the FS section

Sweet. I'll take a look. Thanks!
Edit: Is it V-band EWG?

 

[Enki]

I don't know of any EFR kits for these cars that aren't IWG. Don't let that dissuade you though; the IWG on these things is pretty phenomenal flow wise, and will work just as good at max grunt at sea level as it will 5k ASL.

Aside from a bit more preload on the WGA, there's some tuning shit that can be done to force spool earlier, like WGDC sculpting, AFR and timing shenanigans, etc.

 

[andale927]

Sweet. I'll take a look. Thanks!
Edit: Is it V-band EWG?

No its an IWG setup with the high boost cannister

 

[ClintH]

I don't know of any EFR kits for these cars that aren't IWG. Don't let that dissuade you though.

Oh, I'm in the process of doing something stupid that will require a custom downpipe and probably the CS manifold, so I was figuring EWG would be in the cards.

I'm trying to do an AWD swap following Barett's kit, so pretty much the entire exhaust has to be reworked anyway.

Edit: that's also why I'm wanting to up the power and focus on quick spool. Take advantage of the traction if I'm going to go to all the trouble to swap it