2GR-FE Turbo Sizing (3.5-liter V6) - MR2 Owners Club Message Board
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post #1 of 49 (permalink) Old January 26th, 2018, 22:36 Thread Starter
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2GR-FE Turbo Sizing (3.5-liter V6)

This is a simplified system analysis to support selection of a turbo unit and other components with a 2GR-FE 3.5-liter V6. All of my previous FI experience is with superchargers, both positive displacement (Eaton) and centrifugal (Rotrex). Turbo stuff is new to me.

Basic requirements:
- Single turbo (because I can't see how to fit twin-turbo in the engine bay).
- Rear-mount turbo (to keep all that heat out of the engine bay, and re-use NA headers and y-pipe).
- Power output to safe limit of stock 2GR-FE engine - based on various discussions about 450whp.
- Pump gas (e85 not available in my area).

Analysis tool: The Borg-Warner Matchbot. This tool seems capable of automating the typical forced induction calculations that we're all intimately familiar with (wink), as found in reference works like Corky Bell's books and others. The tool is specific to equipment sold by Borg-Warner, however, as we shall see, it does provide useful guidelines for selecting equipment from other manufacturers too. Here's a link to the default view of the tool without any specific values populated in the data cells:
BorgWarner MatchBot

And this is a slightly re-arranged screen capture of the default view. There are three panes visible, and you should be able to enlarge the image for a better view. From left-to-right, (1) the data entry pane, where the system's desired operating info is entered. (2) The compressor map, to match up the operational points with the performance chart for a given compressor. (3) The turbine selection chart - more on this later.



Ok so let's see how does this work. Now we're gonna look at how we enter data and get our desired performance out of the calculations. The next image shows two panes: (1) the data entry pane, and (2) the calculated outputs. By trial and error, I've populated the cells with data to give me the kind of torque and HP curve that approaches what I want. Here's how it was done:
1. Make an assumption about the shape of the VE curve versus RPM (this is in GREEN). I'm sure this is not exactly accurate but it can be easily adjusted and it will not make a huge huge difference to the results. If I weren't lazy I would figure this out more precisely from the many published charts for NA motors. [Thanks to Marc the VE curve has been updated and I was completely wrong in saying that VE does not make a huge difference, it does.]
2. Adjust the boost pressure in psi (RED) at each RPM to get a desirable calculated result for torque (ORANGE) and HP (BLUE).
For now disregard the other outputs, we'll return to them later.



Here's a link where you can scroll through the details that I've presented above:
BorgWarner MatchBot
[this has been updated with improved VE curve and improved targets for HP]

And here's a HP-TQ chart based on the calculated outputs. I've color-coded the lines to match the data points in the previous image. The Boost/Pressure Ratio is yellow. The HP is blue. The TQ is orange. [This chart has been updated based on improved VE numbers, to give 500BHP or roughly 425-450whp].



Ok so now how do we get from this to selecting a turbo. Easy. We take the calculated points for mass flow rate and pressure ratio and plot them on the compressor charts provided by BW. The MatchBot makes it infinitely easy to do that, just by selecting a unit out of compressor drop down menu.

Let's say we select the EFR 6258. Then it is immediately apparent that our higher RPM operating points are out past the choke line - the turbo cannot support this.



So let's go bigger and select the S500SX - then our low and middle range is hopelessly inefficient and outside the surge line.



We can keep selecting different entries from the drop-down until we get a beauty contest winner, and to my mind it's the S300SX-E below that puts the most operating points right in the middle of "the island of efficiency." [This has been revised - the beauty contest winner is the EFR 9180].



I've done enough damage to my brain for one day, I will continue with more analysis of the turbine size, injector size, intercooler, and so on at a later date.
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Last edited by merryfrankster; June 27th, 2018 at 02:42.
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post #2 of 49 (permalink) Old January 26th, 2018, 22:37 Thread Starter
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To be continued here.
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post #3 of 49 (permalink) Old January 27th, 2018, 08:30
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Quote:
Originally Posted by merryfrankster View Post
This is a simplified system analysis to support selection of a turbo unit and other components with a 2GR-FE 3.5-liter V6.

...

Let's say we select the EFR 6258. Then it is immediately apparent that our higher RPM operating points are out past the choke line - the turbo cannot support this.

...

So let's go bigger and select the S500SX - then our low and middle range is hopelessly inefficient and outside the surge line.

...

We can keep selecting different entries from the drop-down until we get a beauty contest winner, and to my mind it's the S300SX-E below that puts the most operating points right in the middle of "the island of efficiency."

Interesting data... keep up the research. I was looking at a GT3582, wondering now if that will be inefficient...
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post #4 of 49 (permalink) Old January 27th, 2018, 13:47 Thread Starter
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Quote:
Originally Posted by TEKSMRT View Post
Interesting data... keep up the research. I was looking at a GT3582, wondering now if that will be inefficient...
Easy peasy to answer this question. Take the calculated ouputs that I've shown above for pressure ratio (y-axis) and mass flow rate (x-axis), and put them on the compressor chart for the GT3582r provided by Garrett. This would have to be done manually.

I was planning to get to a comparison of the GT3582r and the GTX3576r eventually.

PS. The calculation would have to be adjusted for your target levels of boost, torque and power...
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post #5 of 49 (permalink) Old January 27th, 2018, 17:07 Thread Starter
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Here we go... I've compared side-by-side the GTX3582r and the GTX3576r. I did this by copying the images of the charts into OpenOffice, then plotting the calculated output points and superposing the calculated output chart with the grid in each image. I also re-scaled the 82 image slightly so it would be in the same scale x and y as the 76 image. [These charts have been revised for improved VE numbers and an HP target of 500BHP or 425-450whp].



For purposes of comparison with the Borg Warner unit, the trim of the S300sx-E (above) is 100*(66.1/91.4)^2 or 52.

There are some caveats... we'll get into those later.

Last edited by merryfrankster; June 27th, 2018 at 02:43.
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post #6 of 49 (permalink) Old January 27th, 2018, 19:16 Thread Starter
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Quote:
Originally Posted by TEKSMRT View Post
Interesting data... keep up the research. I was looking at a GT3582, wondering now if that will be inefficient...
I just added an update - the comparison of the operating compressor charts for the Garrett GTX3582r and the Garrett GTX3576r turbo, with calculated outputs for the 2GR-FE 3.5-liter V6 as shown above.

I'm stuffing this with keywords so it turns up in Google.
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post #7 of 49 (permalink) Old January 28th, 2018, 05:26
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12 psi seems like a lot given the compression ration and pump gas assuming it's 91 octane unless this is on Marc's TRD tune. If it's is going to be tracked it is asking for trouble. My plan was 4-5 psi on Marc's Rav4 tune and hope the ecu can deal with light knock if there is any. What kind of boost have people run with the super chargers or turbo?
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post #8 of 49 (permalink) Old January 28th, 2018, 20:03
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Frank, matchbot is pretty fantastic but using it i come up to a pretty different conclusion than you. First i disagree with how early you can bring that boost on. In theory you can but your wastegate percentage is so low at the bottom that it would take forever to spool that. Also, for setting your initial VE percentages just set your boost to zero and match your power output in the calculated output to a dyno chart. keep in mind of course this is the NA VE numbers which will change for a turbo application but it's a start.

Here's the setup i would go with for a ~450hp: BorgWarner MatchBot

keep in mind i would not actually limit the boost down low but that's where i would expect it to land under actual use unless the motor was artifically loaded high (like a steep climb in a high gear)
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post #9 of 49 (permalink) Old January 28th, 2018, 23:16 Thread Starter
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Originally Posted by Gouky View Post
Frank, matchbot is pretty fantastic...
I realized today that I did a big boo-boo in stating that the VE does not make a huge huge difference. There's actually a big difference that comes from the VE numbers at the top end. Thanks for providing that. When we talk about 20% or even just 10% of 400HP that's... a big number. I was just in the process of "eyeballing" a NA torque curve on a grid using about 105% as the peak torque VE to set scale... but your method is far more better. I'm gonna revise my calculations and charts with this updated VE.

The lower lower RPM region 2000-3000 rpm it seems like there would have to be a compromise with almost any sized turbo and realistically nothing starts to happen until 3500-4000rpm.

You've selected a twin turbo in matchbot! This would be "the dream" solution. A. Would it fit in our engine bay. And B. is there any known source for twin turbo manifolds? Or C. Would you just bolt turbos onto the NA headers?

Thanks for your input, I really appreciate it.
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post #10 of 49 (permalink) Old January 29th, 2018, 06:10
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Sorry, I pulled up an old link as a starting point and i did not realize it was on twin turbo, that explains why it took so long to bring the boost on. here's a single turbo setup that i meant to put show: BorgWarner MatchBot note how high the wastegated flow is, the higher this the more responsive the turbo is because you generally have a bunch of excess exhaust energy for what you're looking to do with it. You can manually sweep through the boost pressure curve to check that you have high wastegate at all intermediate boost settings to make sure of this but at a 9psi setup you can generally be sure that this won't be a problem. when you're doing 15psi plus that's when you can easily have dead spots that prevent you from building boost that high.

I did have to bump up to the 6758 but the 6758 is about the same price and significantly cheaper than the bigger ones. but the airwerks turbos are much cheaper also but they use journal center sections so they don't tend to spool quite as quickly.

With the 2GR i would run the normal headers and put it under the trunk floor. it does complicate oil return plumbing but it greatly simplifies the exhaust and reduces the heat in the engine bay.

Fitting twins in the MR2 engine bay would be doable with more of a log style manifold on each end. there is plenty of room in the rear and the front is tight but doable especially with the small size turbo you'd need for the 1.73L of displacement up there. but keep in mind parallel twins really only help plumbing sometimes and when you need so much boost that a large enough turbo isn't available at a reasonable cost. Sequential twins is where you gain a bunch from twin turbos and those simply aren't needed for this boost level with modern turbos.
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post #11 of 49 (permalink) Old March 8th, 2018, 16:38
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Twins?

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Originally Posted by Gouky View Post
Sorry, I pulled up an old link as a starting point and i did not realize it was on twin turbo, that explains why it took so long to bring the boost on.
Not gonna lie, i'm having a hard time understanding all that info... what size WOULD you pick if you were doing twins?

Smaller turbos with a compressor Wheel outer diameter of 72mm and a Turbine Wheel outer diameter of 60mm ?

Last edited by TEKSMRT; March 8th, 2018 at 16:41. Reason: wrong compressor and turbine wheel sizes..
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post #12 of 49 (permalink) Old March 8th, 2018, 17:30
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TEKSMRT, i'd love to help with a better answer but I'll need to know what your goals are to answer that accurately.

Why are you wanting twins? exhaust routing? ultimate power? bragging rights?
what is your ultimate power goal? what is your initial power goal?
What do you plan on doing with the car? drag race? road race? street use? dyno queen?
What kind of fuel are you going to use?
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post #13 of 49 (permalink) Old March 8th, 2018, 19:04 Thread Starter
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To help you get started here's a link to a twin turbo calculation with the EFR 6258 which is the smallest turbo in the range with a 58mm .63a/r turbine wheel which is also the smallest wheel.

BorgWarner MatchBot

And here's what the projected HP and TQ would look like with this calculation:



I've included the calculated wastegate percentage on the secondary axis. As Marc pointed out previously this is an important indicator of how well the turbo is operating and how quickly it will spool.

There's some wiggle room in the assumptions that could affect the results. There's also room to up the boost and gain some more power at the top end but I've capped it at 500 brake or flywheel horsepower which I don't know if you want to go that high but maybe you could and this would be like maybe 425rwhp.

Last edited by merryfrankster; June 27th, 2018 at 02:44.
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post #14 of 49 (permalink) Old March 8th, 2018, 19:56
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2GR-FE Turbo Sizing (3.5-liter V6)

Quote:
Originally Posted by Gouky View Post
TEKSMRT, i'd love to help with a better answer but I'll need to know what your goals are to answer that accurately.



Why are you wanting twins? exhaust routing? ultimate power? bragging rights?

what is your ultimate power goal? what is your initial power goal?

What do you plan on doing with the car? drag race? road race? street use? dyno queen?

What kind of fuel are you going to use?


Thanks for the reply Gouky!! Single would be easier, but I was hoping for quicker spoil with twins. With low boost (less than 12psi) I would like to be at 400bhp - currently on a mustang dyno with my U151F transmission I put down 243whp (whether or not it will handle 400bhp - idk). I will be daily driving the car so driveability is essential with occasional road/street/time trial race. For fuel, initially I will use 93 but at some point E85.

Quote:
Originally Posted by merryfrankster View Post
To help you get started here's a link to a twin turbo calculation with the EFR 6258 which is the smallest turbo in the range with a 58mm .63a/r turbine wheel which is also the smallest wheel.



BorgWarner MatchBot



And here's what the projected HP and TQ would look like with this calculation:







I've included the calculated wastegate percentage on the secondary axis. As Marc pointed out previously this is an important indicator of how well the turbo is operating and how quickly it will spool.



There's some wiggle room in the assumptions that could affect the results. There's also room to up the boost and gain some more power at the top end but I've capped it at 500 brake or flywheel horsepower which I don't know if you want to go that high but maybe you could and this would be like maybe 425rwhp.

Thanks! Assuming my U151F transmission has a higher power loss than an E153, would twin 6258s get me to my target hp? Would I benefit from doing the single 6758 instead? I mentioned before I was looking at something like a GTX3582R/6266 or some some gt25/28 variant.

Last edited by TEKSMRT; March 8th, 2018 at 20:01.
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post #15 of 49 (permalink) Old March 8th, 2018, 22:37 Thread Starter
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Let's do a quick backward calculation if our MR2's NA are at 275rwhp with 15% drivetrain loss this means 323 flywheel (this is 275/0.85). And if you're at 243 whp then in relation to the same 323 flywheel you have a 25% loss (323x0.75=243). Some of the loss could be transmission some of it could be exhaust.

So if your goal is 400bhp that same percentage loss would translate to 300whp which is not much gain from your current 243 for the amount of money and effort it will take.

Anyway if you play around with the calculator's boost levels and wastegate percentages you will see that any of the larger single turbos (EFR 6758, 7064, 7163) will spool quicker and hit maximum boost at lower rpm than the twin EFR6258. This is because in relation to the displacement of one bank (1.75liter) the 6258 is actually bigger than the others in relation to both banks combined (3.5liter).
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post #16 of 49 (permalink) Old March 8th, 2018, 22:59
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2GR-FE Turbo Sizing (3.5-liter V6)

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Originally Posted by merryfrankster View Post
Let's do a quick backward calculation if our MR2's NA are at 275rwhp with 15% drivetrain loss this means 323 flywheel (this is 275/0.85). And if you're at 243 whp then in relation to the same 323 flywheel you have a 25% loss (323x0.75=243). Some of the loss could be transmission some of it could be exhaust.



So if your goal is 400bhp that same percentage loss would translate to 300whp which is not much gain from your current 243 for the amount of money and effort it will take.



Anyway if you play around with the calculator's boost levels and wastegate percentages you will see that any of the larger single turbos (EFR 6758, 7064, 7163) will spool quicker and hit maximum boost at lower rpm than the twin EFR6258. This is because in relation to the displacement of one bank (1.75liter) the 6258 is actually bigger than the others in relation to both banks combined (3.5liter).

275rwhp, isnít that with gookys headers and not cats right? Currently Iím still running oem catted headers, with everything back replaced with 2.25Ē custom full dual exhaust. If anyone made headers for the AWD Rav4, I could probably come closer to that 275 from my 243... but I definitely think the AWD tranny is more parasitic on the hp.

My bad, I meant 400whp, not bhp, a ~160hp increase over my 243.

What if I didnít use the BW turbos and went with something smaller, something they donít offer? The 3.5L ecoboost engine runs a small GT1548 turbos...
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post #17 of 49 (permalink) Old March 9th, 2018, 00:44 Thread Starter
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For 400whp with 25% loss we'll say your target is 533 flywheel.

The GT1548 compressor map (google) shows a maximum airflow about 20lb/min which translates to 200HP so with two of those you get 400HP flywheel max.



If we look through the Garrett compressor maps you should be able to get 533 from twin GT2560R maybe without going crazy with the boost level but I don't know what the operating characteristics would be like for wastegate % or rpm for max boost/boost profile. Here's the compressor chart:

https://www.turbobygarrett.com/turbo...argers/gt2560r

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Last edited by merryfrankster; March 9th, 2018 at 00:49.
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post #18 of 49 (permalink) Old March 9th, 2018, 05:39
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You're probably not anywhere near 25% drivetrain loss. These modern automatic transmissions aren't like the old slushboxes from back in the day. As much as i'm a solid fan of manual transmissions and would never want to own an automatic i can't say that efficiency is the reason for that anymore.

The AWD does add two hypoid gear losses to the drivetrain which is something but not that much.


As for turbos, a twin scroll single will always spool faster than twins. Also, with your AWD drivetrain you'll notice you have no room at all behind the motor. it's all transfer case back there so you'd have to mount the rear turbo over the transmission anyways. at that point you may as well go for a single turbo. it'll save you a ton of money over two good turbos or cost you about the same as two mediocre turbos which would spool even slower.

You mentioned the ecoboost turbo, are you looking to be able to buy a second hand turbo for this task? the big issue there is generally turbo map availability.
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post #19 of 49 (permalink) Old March 9th, 2018, 06:59
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2GR-FE Turbo Sizing (3.5-liter V6)

Thanks for all the info, sounds like a twin scroll single would be best. Thatís what DDPR used to get +600whp on 93 in their MR2. Iíll keep my eyes open for a good deal. Something I suppose with a ceramic dual ball bearing and billet wheel? I only mentioned the ecoboost for the 3.5L size of engine and the relatively small gt15 turbos.

Your right tho, trying to do twins with that rear transfer case will be difficult - making any budget build out of the question. I even considered a rear mount setup somewhere near where the factory muffler was mid-vehicle as I have the extra clearance with the Rav4.


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Last edited by TEKSMRT; March 9th, 2018 at 07:35.
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post #20 of 49 (permalink) Old March 9th, 2018, 07:55
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The twin scroll just helps the spool, if you're trying to stay on a budget build there are still options out there. Here's a quick one i can think of for $150: https://www.ebay.com/itm/2006-Ford-P...o/142715195743

of course that is not a twin scroll and it isn't a ball bearing turbo but it would spool up relatively quickly and would get you pretty close to your power goal. the variable turbine nozzle bits on there will help you spool quicker if you hook it up (effectively giving you a smaller A/R at low boost and then larger at high boost)

A quick search says this is the compressor map for it:


I can find a turbine map for the fixed turbine but not for the variable nozzle version.

Certainly don't think that the only way to do this is with a $1500 turbo. going the budget route can be nice and then when you outgrow that turbo there's a bunch of upgrades available for that stock application that will bolt-in.

as for putting the turbo underneath the car i would advise against it to avoid needing to pump the oil back to the oil pan. electric hot oil pumps that are reliable are not cheap so make sure you consider the total cost when figuring your price.

You'll also need a recirculating blow off valve as most stock application turbos do not have them built in. There's also sometimes potential wastegate issues depending on the turbo you go with. some stock ones aren't big enough when you start pushing more power and you get boost creep. the subaru WRX/STI applications are a good example of this.
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