Too Many Turbo Options. T3/t4 Divided/undivided .63 .78 .82 .1.06 Please Help

[Unclerico]

OK guys I dont have much experience with RB26 being from the states so Im hoping my English speaking cousins from down under might be able to help me out. lol

Im coming from a single turbo 2J(GTX3582R) car over to my R32 Skyline. Ive been doing my research on turbo selection and Its hard to decifer the BS("I think" or "it should be") from the facts. Also a lot of different factors to consider will change the outcome.

After watching Motive's Single vs Twin video Ive pretty much decided on single. I like single turbo setups and working on the twins just sucks!

My choices are between GTX3076R or the GTX3582R. Then we got t3 or t4 and divided or undivided. Then to add even more options we have the A/R.

Thats 18 different combinations to choose from!!!

GTX3076R T3 GTX3076R T4

.63 Undivided only .63 Undivided only

.78 Undivided & Divided .82 Undivided only

1.06 Undivided & Divided 1.06 Undivided only

GTX3582R T3 GTX3582R T4

.78 T3 Undivided & Divided .63 Undivided only

.82 T3 Undivided & Divided .82 Undivided only

1.06 T3 Undivided & Divided 1.06 Undivided & Divided

I realize the GTX3076R is smaller than what most would consider. But I used a GTX3582R 1.06 Divided T4 on my 2JZ and though the lag wasnt bad I would like my Skyline to be a little more responsive.

So Im thinking a higher flowing(t4 big a/r) 3076 or lower flowing(t3 low a/r) 3582 might be the way to go?? If that makes any sense. But keep in mind I dont want to much back pressure and extra stress on the engine.

I will be using 91 octane pump gas. At around 20ish psi. I would like to run higher but California pump gas is terrible. And Im hoping to get around 330kw-370kw to the wheels. I will never be using race gas or E85, so I will probably never see anything over 20-22psi.

I think I should cross off all the 3076 T3 turbos along with the 3582 T4 turbos. Is that a good place to start?

[R31Nismoid]

Split pulse GT3076 with a .82 housing

Job done for a responsive 300rwkw on a 18-20 psi to account for your fuel.

Or you'll need a GT35 to get closer to 350rwkw with maybe a smidge more boost, obviously will come down to the tune

GTX Series from all accounts seem to prefer running more boost and thus means E85, certainly not an option if you are quality of fuel limited.

[hypergear]

I had issues with 76mm comp wheel not been able to keep up with set boost level after 5000RPM. That resulted in a fall in boost, power and torque. I've tried with a GTX 3076 equivalent wheel as well as standard. GTX made more power but still had that boost fall.

GT3582 will do it but quite laggy. I ended up building a customized turbo that managed to hold boost, made 400rwkws+ while not much laggier then the stock twins. My result is at RB26 dyno section, there is a comparison of it running against factory twin T25s also for references.

[R31Nismoid]

How much boost were you running though? I've never seen a GT3076 / GTX fall over @ 18-20psi.

25psi+, different story of course.

[sky30]

I had issues with 76mm comp wheel not been able to keep up with set boost level after 5000RPM. That resulted in a fall in boost, power and torque. I've tried with a GTX 3076 equivalent wheel as well as standard. GTX made more power but still had the boost fall.

GT3582 will do it but quite laggy. I ended up building a customized turbo that managed to hold boost, made 400rwkws+ while not much laggier then the stock twins. My result is at RB26 dyno section, there is a comparison of it running against factory twin T25s also for references.

Sounds good. U have a link to comparison?

[hypergear]

Details are below:

http://www.sau.com.au/forums/topic/261613-hypergear-hiflow-service-continued/page-533#entry7483378

With the GTX 3076 equivalent wheel. The maximum It managed to hold 20.2psi maximum and that did 374awkws on E85 fuel. My goal was responsive 400awkws, It was abit short to my goal.

[Unclerico]

I had issues with 76mm comp wheel not been able to keep up with set boost level after 5000RPM. That resulted in a fall in boost, power and torque. I've tried with a GTX 3076 equivalent wheel as well as standard. GTX made more power but still had that boost fall.

GT3582 will do it but quite laggy. I ended up building a customized turbo that managed to hold boost, made 400rwkws+ while not much laggier then the stock twins. My result is at RB26 dyno section, there is a comparison of it running against factory twin T25s also for references.

You said the GT3582 will be laggy. Not exactly sure which configuration you were talking about. How would a T3 divided with .82 a/r be in your opinion?

[Unclerico]

Split pulse GT3076 with a .82 housing

Job done for a responsive 300rwkw on a 18-20 psi to account for your fuel.

Or you'll need a GT35 to get closer to 350rwkw with maybe a smidge more boost, obviously will come down to the tune

GTX Series from all accounts seem to prefer running more boost and thus means E85, certainly not an option if you are quality of fuel limited.

Thanks for the great info. What exactly does it need more boost for? Are you saying it takes more boost to make the same response and max power than on a GT?

And not that I dont believe you, Im sure your way more qualified than I am on this subject. It just seems backwards to buy a GT over the GTX haha. All you hear about these days are how good the GTX's are.

[R31Nismoid]

You need to look at the compressor maps etc. They flow more air at higher boost levels.

Well yeah it might seem to be a bit backwards but you've actually done more than what most people do - given a decent amount of requirements. The fact you are not going E85 is the biggest one. The GTX Turbos perform well, you just need to put boost into them to really make the most of them. Most people singing their praises will be running big boost (20psi, and above 20-22psi is where they really do shine). I challenge you to find a result of a GTX3076 running under 20psi - I honestly don't recall seeing one

[hypergear]

Here are my results: GT3582 equivalent . 82 rear. I'm aware ATR45SAT is running more boost.

3582 equivalent in .78 rear

GTX3076 equivalent in . 82 rear. (I could not boost it any higher then 20.5psi up top with external gate fully shut).

Results were collected from a unopened Rb26dett engine using stock cams and E85.

Other thing I've noticed but unsure of is my Rb26 seems to be making slightly less power on same boost then my RB25det. But is happier taking more boost and work with larger turbos.

[Unclerico]

You need to look at the compressor maps etc. They flow more air at higher boost levels.

Well yeah it might seem to be a bit backwards but you've actually done more than what most people do - given a decent amount of requirements. The fact you are not going E85 is the biggest one. The GTX Turbos perform well, you just need to put boost into them to really make the most of them. Most people singing their praises will be running big boost (20psi, and above 20-22psi is where they really do shine). I challenge you to find a result of a GTX3076 running under 20psi - I honestly don't recall seeing one

Well unfortunately I can only look at the maps that Garrett provide. And for the gt3076 they only use a .60 and the gtx3076 they only use a .70. Which I dont think I would use either of those rears. And for the 3582 they only show a .70 as well. Is there a general rule of thumb to calculate using a different a/r?

Edited July 22, 2015 by Unclerico

[R31Nismoid]

That's the front housing... Not the rear housing. Why would you change the front housing? A minor A/R change front housing it's really going to alter things too massively. The turbine housing is listed on the other graphs.

https://www.turbobygarrett.com/turbobygarrett/turbocharger#GTX3076R

If you just go to the main site and plug "3076" in you can then click both tickboxes and compare. You'll see they are quite different...

The bulk of GTX results on RBs are E85 and higher boost than you'll be able to run due to the fuel restrictions. A GTX might well perform quite well at 20psi or below, but not many people are doing it so do you know it really "will" work? GTXs were promised to give "better response" but they kinda didn't... So it's hard to say it's gonna be worth it on a $$ scale for the lower boost levels you are after. The maps suggest they are more efficient at the same points as a GT3076 but the real world hasn't really seen anyone do it on PULP and 18psi say. The real differences people have noticed are when feeding the GTX the boost it isn't scared of.

[AngryRB]

I ran a GTX3076 on ULP98 , made 280kw at 16psi which is bang on same as GT, on E85 it made 320kw on 16psi and 20psi made by 3800, so in my case they are equal..

But, on 98 it was a bit boring to drive, havnt driven others cars to compare but with GTX it didn't really wake up til 4500rpm on 98 so bit all or nothing type thing.

Also driven a R33 with a Hypergear SS2, drove just as good as the GT and GTX even on 11psi it was giving a good push in the seat, so that's a winner on a budget.

Edited July 22, 2015 by AngryRB

[Unclerico]

That's the front housing... Not the rear housing. Why would you change the front housing? A minor A/R change front housing it's really going to alter things too massively. The turbine housing is listed on the other graphs.

https://www.turbobygarrett.com/turbobygarrett/turbocharger#GTX3076R

If you just go to the main site and plug "3076" in you can then click both tickboxes and compare. You'll see they are quite different...

The bulk of GTX results on RBs are E85 and higher boost than you'll be able to run due to the fuel restrictions. A GTX might well perform quite well at 20psi or below, but not many people are doing it so do you know it really "will" work? GTXs were promised to give "better response" but they kinda didn't... So it's hard to say it's gonna be worth it on a $$ scale for the lower boost levels you are after. The maps suggest they are more efficient at the same points as a GT3076 but the real world hasn't really seen anyone do it on PULP and 18psi say. The real differences people have noticed are when feeding the GTX the boost it isn't scared of.

OMG this whole time I thought the a/r on the maps was exhaust housing a/r. Damn I wish we had more e85 pumps here. lol