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Discussion Starter #1 (Edited)
This is a turbo-matching analysis using my powerband goals only as an example, but others may find the process helpful in reaching their own goals, or to refine them based on the results. Please feel free to comment on the process outlined, my goals, or your own.

I've considered going single to improve durability and performance on the road course. The twin/BPU setup runs great at 17 psi, but power does fall off a lot at redline, necessitating earlier upshifts that throw away the torque multiplication effect of the lower gear ratio. I know the twins will only last so long at 17 psi. The challenge for me has always been to find the single setup that I felt would retain the throttle response and strong bottom end (from 3000 rpm if possible) and a stronger top end to redline. I want to continue to run 17 psi or less and have as flat a torque curve as possible. I'd also like to retain the stock fuel system, MAF, and intercooler.

Single turbos eliminate the restrictions of the twins exhaust plumbing, and that improves the engine's airflow abilities (volumetric efficiency) at higher rpm. The larger the single's turbine housing, the less restriction and the greater the VE and flow. More flow...more power. But the larger turbos are less efficient at lower flow rates, and this compromises throttle response, ability to spool early, and low rpm power. The use of larger cams in conjunction with a slightly smaller turbo housing would provide the improved VE of a large turbo, and the lower rpm performance of a smaller turbo.

I've used a turbo calculator to calculate the airflow requirements at various rpm so they could be plotted on various turbo compressor maps that I'm considering. The difficulty is in estimating the VE at these different levels, and the calculated flows will only be as good as our inputs. I've used a process called "scaling" to estimate these VE values. Basically torque curves mirror the engine's VE curve when boost level and tuning is kept constant. By examining the torque curves on various dyno plots you can take the torque at any rpm and divide it by the peak torque to calculate its percentage of peak torque. It's generally accepted that 4 stroke turbos have a peak VE of 95-99%, and with flow improvements from cams, catless exhausts and freer flowing turbine housings and plumbing I don't think it's a stretch to say peak VE on a 2JZ is probably around 100%. If torque curves of singles with cams at 7000 rpm are 93%, or expected to be ~ 93% if cams were used, then VE @ 7K is 93%. If in sequential mode the twins can make 87% of peak at 3 k then VE is 87%. I examined a number of dynos to predict engine VE at the various rpms that the calculator requires, and you will see them displayed in the tables of calculations.

Other info I inputed into the calculator were my goal whp of 475, 3.0L displacement, .47 BSFC (see their table), 12.0:1 AFR, 1.7 psi IC pressure drop, and the intake air temps as shown. I've compared this calculators results with actual dyno results and found them to be quite close. In the end, all we're trying to do is approximate the engine's airflow requirements and then plot those on the compressor maps of various tubos. I've plotted these results on three Garrett turbos that also have published turbine maps, and from these I know they will offer excellent performance within their various power ranges. They are the GT3076R, GT3582R and GT4088R.

The complete table of inputed values, calculated results, and plotting on all three maps can be seen here :

http://www.squirrelpf.com/turbocalc/index.php?version=4&target_peak_power=475&engine_disp=3.0&engine_disp_factor=0&target_af=12&bfsc=0.47&max_ic_loss=1.7&rpm_redline=7000&rpm_peak_power=6500&rpm_max_boost=3000&rpm_min_boost=2500&vol_1=80&vol_2=85&vol_3=95&vol_4=93&vol_1=80&vol_2=85&vol_3=95&vol_4=93&intake_temp_1=90&intake_temp_2=120&intake_temp_3=135&intake_temp_4=140&turbo_n=1&map_sel0=109&map_sel1=42&map_sel2=47

Here's the GT3076R plot for easy reference:



The objective is to be able to plot all of your requirements on the compressor map. If a point can't be plotted it means that requirement can't be met. If it plots very close to the edge of the map then it may not be completely achievable, and the accuracy of our calculator inputs become very important. The plotting strategy for a drag setup would be to plot the peak airflow requirement within the highest efficiency islands (circles) as possible. The highest efficiencies mean that the air temperature from the turbo will have been increased the least amount possible, and the cooler air will be denser to make more power. A street, autox, or road race strategy would be to fit hopefully all the points on the map, with mid range flows passing through the highest efficiency islands, and the peak requirement being to the right. 70% is still a very high efficiency, and for comparison the stock twins would be likely closer to 60% or less. Garrett maps show efficiency only down to 65% I believe.

You can see from this analysis that all points plot on the GT3076R, they barely fit on the GT3582R, and the GT4088R missing the lower ones. If I were to be completely accurate I'd adjust the VE inputs for use of the larger turbined GT3582R and GT4088R as they would improve high rpm VE even more, and restrict it more at lower rpm. I haven't done that as I can see that would only show them to be less suitable for my requirements, but would certainly make them the clear choice if higher boost or flow mods were ever to be used. It should be pointed out that when requirements plot close to the edge of the compressor map they may not be attainable. If any of our assumptions are off, or if the turbine doesn't have enough efficiency in that flow range, then we'll likely miss achieving the desired boost level and/or flow rate. As a rule of thumb, I recommend using a lower AR turbine housing to help ensure that the lower flow points plotted on the left side of the map may be achievable.

You can change any parameter that you feel will make the results more accurate for your setup and plot your way to the turbo of your dreams. It's interesting to note that the GT3076R is the turbo used on the Amuse Supra, and the turbo Toyota North America finally approved on the modified Supra they had Full Race build.

Bruce
 

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Very interesting and well thought out, Bruce. But I knew you had it in you ;)

I'll give your analysis a study to see where mine fits in...probably my PHR1 setup is more on the chart than the GT4088 but less than the GT3076R. For my first attempt at a single setup, so far I'm quite satisfied with what I have now...though some tweaking and tuning and testing may point me toward a new and better setup one of these days.
 

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What about these new Precision turbos coming out that supposedly spool the same, yet offer much better efficiencies and, in effect, more power at the same boost levels. One would be the PT6262a. Precisions site is pretty worthless as far as finding any info for these turbos though. I don't even see where to look at a compressor map for these turbos either.

I tried to plot points on a compressor like you did a year ago, albeit a bit more vaguely than you, and it helped me understand turbo selection a bit. It sure was a PITA to get to the point to where you can start plotting points though. :)

Alex
 

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So Bruce, what Turbo are you getting then?

I can't yet follow your numbers and graphs but I would like to know what turbo you are gettng.

Have you looked at Bulls Eye Power's Borg Warner S362 and S366 turbines? The S362 is comparable to a GT35 but gives more flow / power.
 

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Discussion Starter #5 (Edited)
Very interesting and well thought out, Bruce. But I knew you had it in you ;)

I'll give your analysis a study to see where mine fits in...probably my PHR1 setup is more on the chart than the GT4088 but less than the GT3076R. For my first attempt at a single setup, so far I'm quite satisfied with what I have now...though some tweaking and tuning and testing may point me toward a new and better setup one of these days.
Hi Nick,

You already have one of the best popular Supra RR setups for sure. But like every other Supra kit it has the large T4 divided turbine housing. The Supra community has been generally so single focused on peak hp that the less restrictive T4 was the answer to improve high rpm VE and flow. The problem is that the T4 housings have poor turbine efficiency at the lower exhaust flow rates (lower rpm), and this means they aren't able to extract enough energy to power the compressor to provide the flow that their compressor maps indicate is possible.

The smaller T3 non-divided housings have much higher turbine efficiency at lower exhaust flow rates, and in the MR2 community we see them flowing up to 560 whp or more on our 2L. Unfortunately there aren't any Supra exhaust manifolds with a T3 flange. This means using a T4 to T3 adapter, which some may not like to use, or that might even cause fitment issues I suppose. A year or two ago I contacted some vendors regarding this and found no interest in finding a T3 solution.

The GT3582R with T3 turbine housing is one of the best designed turbos on the market, and perfect for the needs of the vast majority of Supra owners power goals. Its compressor and turbine wheels and housings are perfectly matched, and their efficiencies are unmatched in the industry. This gem hasn't gone unnoticed in by Supra owners craving a stronger bottom end, but since we don't have a T3 manifold we order it from ATP with their "custom" T4 divided housing (with no turbine efficiency map!). Unfortunately that T4 housing seriously compromises the stellar spool characteristics of the GT3582R, and I suspect it doesn't spool much better than some other T4 divided setups. I haven't looked in the last while, but there's never been a dyno posted for this turbo on a Supra in N.A. to my knowledge.

So that's my little rant, and sums up why we don't see Supras with full boost at 3k with incredible throttle response...and why I'm still on the twins.

Bruce
 

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Discussion Starter #6
What about these new Precision turbos coming out that supposedly spool the same, yet offer much better efficiencies and, in effect, more power at the same boost levels. One would be the PT6262a. Precisions site is pretty worthless as far as finding any info for these turbos though. I don't even see where to look at a compressor map for these turbos either.

I tried to plot points on a compressor like you did a year ago, albeit a bit more vaguely than you, and it helped me understand turbo selection a bit. It sure was a PITA to get to the point to where you can start plotting points though. :)

Alex
Sounds like wonderful marketing, but the proof is in the turbine engineer's maps. Compressor maps show the airflow that they are capable of moving, but the turbine map is really much more important because it's what the compressor relies on to make anything flow. It's also what determines whether overall engine VE will be improved, and where in the powerband it will have the most impact. This is how I identified the GT3076R, GT3582R and GT4088R as being the top picks from Garrett (they provide both maps).

PITA is right! Before I found this calculator I also used to calculate all the flows the long way, right down to calculating air density mass airflow at different intake air temps. It did however lead to identifying two excellent turbos for the MR2 (GT2860RS and GT3071R).

Bruce
 

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Discussion Starter #7
So Bruce, what Turbo are you getting then?

I can't yet follow your numbers and graphs but I would like to know what turbo you are gettng.

Have you looked at Bulls Eye Power's Borg Warner S362 and S366 turbines? The S362 is comparable to a GT35 but gives more flow / power.
My goal is to create the strongest, flattest, and broadest powerband while not exceeding 475 whp. This will enable me to retain the stock fuel system, ECU and MAF I'm hoping. I will also be able to retain the stock intercooler, thus avoiding a wide range of cooling issues. I'm a strong believer in running low boost and water injection to lower intake air temps. Where the original calculations were done using a BSFC of .47 for pump gas, I am considering water/methanol injection for reduced intake air temps and an improved BSFC to .43 (through more advanced timing made possible by the methanol). If I was able to find a truly safe methanol/failsafe solution I could make my powerband goals with around only 13 psi. At some point I'd likely need an EMS with the methanol. Running low boost like that with the GT3076R would have many benefits, and provide a very flat torque curve from 3k until the cows come home with a little valve train upgrade.

Here's how that would look:
http://www.squirrelpf.com/turbocalc/index.php?version=4&target_peak_power=475&engine_disp=3.0&engine_disp_factor=0&target_af=12&bfsc=0.43&max_ic_loss=1.7&rpm_redline=7000&rpm_peak_power=6500&rpm_max_boost=3000&rpm_min_boost=2500&vol_1=80&vol_2=85&vol_3=95&vol_4=93&vol_1=80&vol_2=85&vol_3=95&vol_4=93&intake_temp_1=85&intake_temp_2=90&intake_temp_3=110&intake_temp_4=110&turbo_n=1&map_sel0=109.

I haven't seen maps for those Bullseye turbos. Can you post them?

Bruce
 

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Bruce,

This is great info. I agree that nobody seems to do proper research when it comes to sizing a turbo for their goals. "Bigger is better" seems to be the motto around here, and this is why you only need to go to the Supras for Sale section of this site to see why there are always high-hp fully-built Supras for sale. People that have never driven or ridden in a 700hp single decide that they're going to call MVP and place an order for big single kit with all the goodies (built motor, head, agressive cams, huge turbo, fuel system). Unfortunately after spending a hefty amount of cash and plenty of downtime, they realize that the car sucks for anything other than WOT pulls on the highway late at night. After riding in a BPU car, they realize they had more fun after all.

I love having power down low with the stock twins. My ex-mkiv was a 67mm single and it was quite laggy in my opinion for daily driving, even with a 0.68 exhaust.

I'm looking to swap my twins again, but this time I'm really focusing on having the response and torque as close as possible to the twins. I bought a meth kit that I'll be using as I'd like to make more HP on high boost than your goals, but I want to maintain very good low-end as well. 600whp would be nice with meth (25-26psi), so if you have any advice, I'd love to hear your suggestions as well.
 

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Bruce,
your comments about the benefits of smaller T3 housings reminded me of small flanged twin turbos...so not to go too far off topic in this thread, but I wonder how the turbine & compressor maps for a couple of little Garrett GT2560R (aka GT28R) T25 flanged turbos....even internally gated ones like some pretty nice ones from ATP...how they look compared to what you're describing above. There is a relatively recent thread here about twin turbos for road racing that shows some of "us" are still thinking about alternative solutions.
 

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Discussion Starter #10
I love having power down low with the stock twins. My ex-mkiv was a 67mm single and it was quite laggy in my opinion for daily driving, even with a 0.68 exhaust.

I'm looking to swap my twins again, but this time I'm really focusing on having the response and torque as close as possible to the twins. I bought a meth kit that I'll be using as I'd like to make more HP on high boost than your goals, but I want to maintain very good low-end as well. 600whp would be nice with meth (25-26psi), so if you have any advice, I'd love to hear your suggestions as well.
Yes...pray for a miracle! BPU sequential throttle response and very good low end are inconsistent with making 600 whp from a 3L. I did help a friend choose between a GT3582R and GT4088R on a similar build. I leaned toward the GT3582R because I'm into spool and grunt, and he to the GT4088R for his 1/4 mile hobby.

He made 592 whp uncorrected and 582 whp std. corr. @ 25 psi with methanol and stock cams. The table below shows I adjusted the BSFC to .43 to account for tuning on meth, IC temps as shown, and a 81% VE at peak hp with stock cams and big turbo. I plotted them on both turbo maps, and you can see they both plot very well in the 78% efficiency region at peak power, and it'd be hard to identify the best one based on these plots. The difference can only be seen in the turbine maps where the GT3582R has maximum efficiency at a much lower exhaust flow (rpm) rate.

If you want the spool monster of your dreams it's the GT3582R with .63 AR. It'll make a few ponies less because it doesn't have quite as gaping a turbine, but the improvement in low end will be significant.

http://www.squirrelpf.com/turbocalc/index.php?version=4&target_peak_power=592&engine_disp=3.0&engine_disp_factor=0&target_af=12.0&bfsc=0.43&max_ic_loss=1.2&rpm_redline=6800&rpm_peak_power=6500&rpm_max_boost=4200&rpm_min_boost=3500&vol_1=80&vol_2=87&vol_3=81&vol_4=79&vol_1=80&vol_2=87&vol_3=81&vol_4=79&intake_temp_1=90&intake_temp_2=100&intake_temp_3=110&intake_temp_4=110&turbo_n=1&map_sel0=42&map_sel1=46.

The GT4088R on meth made 300 ft-lbs at 3700 rpm for reference, and that's pretty good for close to 600 whp. ..and about equal to a BPU in TTC mode, and that may be just close enough for your goals!
 

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Discussion Starter #11
Bruce,
your comments about the benefits of smaller T3 housings reminded me of small flanged twin turbos...so not to go too far off topic in this thread, but I wonder how the turbine & compressor maps for a couple of little Garrett GT2560R (aka GT28R) T25 flanged turbos....even internally gated ones like some pretty nice ones from ATP...how they look compared to what you're describing above. There is a relatively recent thread here about twin turbos for road racing that shows some of "us" are still thinking about alternative solutions.
The GT28R is actually a GT2860R, and the GT2560R is a GT25R. At 68 and 65% turbine efficiency, they have a little less than what would be ideal. The GT2860RS by comparison has 72%, as do the three larger models I've identified in this thread. Lower turbine eff. means slower spool and lower engine VE. The twin GT2860R's are dyno'd, and their stealth appearance and performance should definitely appeal to many.

It's important to realize that once you've plotted your way to the best match, that ultimate spool and low end will be determined completely by the pressure differential across the turbine wheel. You want as close to 0 pressure/resistance from turbine housing(s) to exhaust tip, and the more complex the exhaust plumbing, the more resistance, and the slower the spool.

Making high top end power at low boost requires high VE, which means low resistance from the compressor outlet(s) to turbine inlet(s), and complex plumbing hurt you there, and the pressure losses that result also cause the turbo(s) to work at a higher pressure ratios in order to meet the desired boost level as controlled by a signal way down the line in the intake manifold. These losses effectively move all of the plot points higher on the compressor maps into lower efficiency and higher shaft speed areas...and that's not ideal.

There's an awful lot that goes into designing a good turbo setup. Btw, the GT2860RS makes the most power (area under the torque curve) of any turbo on the stock VE MR2...and I just love to track mine (hehehe)!

Bruce
 

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Discussion Starter #13
Bruce, what about a GT3582r with a .82 t3 rear housing instead of the 0.63 you mentioned? How will that be for low end?
That's very difficult to say. The only comparison I've seen, and it was done in a flawless manner, was with a GT2860RS with .64 and .82 housings. The .82 only made 7 whp more, and lost a whack of low end torque. Everyone agreed it was a poor choice. I always recommend the lower AR, and then cams if you need to up your top end VE/flow.

Bruce
 

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That's very difficult to say. The only comparison I've seen, and it was done in a flawless manner, was with a GT2860RS with .64 and .82 housings. The .82 only made 7 whp more, and lost a whack of low end torque. Everyone agreed it was a poor choice. I always recommend the lower AR, and then cams if you need to up your top end VE/flow.

Bruce
Ok great. I'll have to retract my offer on one that someone was selling.

Do you know a good place to buy the GT3582R with .63 AR for a good price? The US dollar sucks right now and JRP wants $2k cdn and a 30-60 day wait time.
 

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Discussion Starter #15
I really don't know who has them or pricing. Are you planning to get one with the T3 turbine housing, or the T4, and if T3 how will you mount it? I saw in another thread reference to an XSPower T3 manifold for the Supra.

Bruce
 

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Bruce,

Awhile ago when I ordered my setup from FullRace I was talking to Geoff on the phone about the Toyota North America Supra that they built. That car had more than just a T3 flange welded on their manifold, it had smaller runners. Geoff was saying that for my choice of turbo (GT3582R with the twin scroll 1.06a/r housing) that I was on the lower end (power wise) that their T4 twinscroll manifold was designed for. I'm still not done with the project, but everything that I have read about the 35R has been great. It seems like this is the choice turbo for somebody wanting streetable spool characteristics as well as plenty of power for the street/road course.

Hind-sight being 20/20, and had I talked to Geoff first instead of Eric, I would have commissioned them to make another T3 manifold and then I could have run anything from a 28R to a 35R. Instead I'm limited to the smallest available turbo being the 35R, which leaves room for more power down the road, however I doubt that I will be needing/wanting it.
 

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Bruce you were so helpfull in my thread asking for roadracer/autocross advice for my set-up that i have researched a T3 2jz-gte manifold made in australia that may work for you in terms of having your T3 flange . N*Power is the name of the company, PM me your e-mail adresse and i will send you a link if you would like ...also its an open flange not twin scroll . LMk ...
 

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Discussion Starter #18
Bruce,

Awhile ago when I ordered my setup from FullRace I was talking to Geoff on the phone about the Toyota North America Supra that they built. That car had more than just a T3 flange welded on their manifold, it had smaller runners. Geoff was saying that for my choice of turbo (GT3582R with the twin scroll 1.06a/r housing) that I was on the lower end (power wise) that their T4 twinscroll manifold was designed for. I'm still not done with the project, but everything that I have read about the 35R has been great. It seems like this is the choice turbo for somebody wanting streetable spool characteristics as well as plenty of power for the street/road course.
Hi Mark,

Have you heard anything about the specific T4 twin scroll version you purchased? 1.06 is a massive AR, and there's no turbine efficiency maps available AFAIK. The MR2 experience so far has been that the twin scroll doesn't perform as well (GT3071R-SS vs. GT3071R-TS). I have heard it claimed though that the twin scroll's advantage kicks in at higher flow levels than what's used on the MR2. Hopefully Full Race, or something else you've found, shows it to perform to your expectations.

Bruce
 

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Discussion Starter #19
Bruce you were so helpfull in my thread asking for roadracer/autocross advice for my set-up that i have researched a T3 2jz-gte manifold made in australia that may work for you in terms of having your T3 flange . N*Power is the name of the company, PM me your e-mail adresse and i will send you a link if you would like ...also its an open flange not twin scroll . LMk ...
Thanks for the tip...found it with google. I'd prefer to use a cast manifold for my spool goals, and that should be fine for my power levels. The GT4088R with 592 whp was on a cast mani as well...who'd have thought it!

Bruce
 

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I really don't know who has them or pricing. Are you planning to get one with the T3 turbine housing, or the T4, and if T3 how will you mount it? I saw in another thread reference to an XSPower T3 manifold for the Supra.

Bruce
T3 housing for sure. I already bought a cast Toyomotive T4 manifold that I'll have a T3 flange fitted and welded to.
 
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