Which turbine size for gtx3071r?

[diss7]

So I was fairly well getting settled on a gtx2867r 0.86 a/r until I had a closer look at its compressor map, compared with a gtx3071r. The 3071r at 14psi and 40lbs airflow sits in a much better efficiency island.

What I want to know, is how to go about choosing the turbine size for the 3071r? There are three different sizes in v band housings. .63, .86, and 1.02.

I had pretty much decided on the 2867r with the .86, but I understand that its a ratio not necessarily a size/rating, so a .86 turbine in a 3071r is not the same?

Any help/tips on turbine sizing would be great. Cheers

[cruizin01]

You would want a .63 imo. I would think the larger ones will spool too slowly.

[DeBiase]

It's a diference in the housing. Not the turbine itself. The 30 in the GTX3071R is the number signifying the actual size of the turbine. The second number (71) is the compressor wheel size. The 30 has a 60mm turbine and I am not sure about the 28 but I believe it's around 54mm turbine. So essentially the difference between the GTX2867R and the GTX3067R is 6 mm in the turbine wheel while the compressor is the same (I know the actual turbo in question is a GTX3071R) I too have been wondering if I will end up getting the GTX2867R or the GTX3071R. I have even considered the GT3071R as its nap seems to be between the two though a bit narrower tan the others. Btw I'd it in an island for redline RPM or midrange RPM? And sorry for the rant. As far as the A/R it depends I'm not sure how the .63 will inhibit top end power as it can restrict it and how much it matters to you but it will most definitely spool faster. I am also trying to figure out the A/R myself for what I want out if it. Hope this has helped!

[Sportsguy83]

I was in the same predicament between .63 and .86 backhousings and went with .86. Why? I wanted to have room to grow in the future and know the .63 housing will choke up a bit at higher RPM's.

[DeBiase]

Did you go with the GTX3071? Would you recommend the GTX2867 or the GTX3071 for a powerful midrange as well. Not just top end power. I want to be somewhere in the 325-350whp range.

[Sportsguy83]

Originally Posted by DeBiase

Did you go with the GTX3071? Would you recommend the GTX2867 or the GTX3071 for a powerful midrange as well. Not just top end power. I want to be somewhere in the 325-350whp range.

I went with GTX3076R. I was looking for an efficient turbo that would not taper off at higher RPMs. I owned the AVO turbo and hated how it peaked and just tapered off when running 16 psi of boost.

If your goal is 325-350, I would just stay with the 2867 or 2871

Ptuning is using a GTX3076R on their kit, you can check their dyno plot for power curve.

[mrk1]

When I pick turbos I also consider my driving style and how I will realistically use the car. My garrett is very different so it's hard to compare numbers but I know that I really don't push into the highest rpms that often so having a turbo that needs those rpms isn't the best choice for me.

I don't know how you use your car but that's my example.

[nelsmar]

Originally Posted by DeBiase

Did you go with the GTX3071? Would you recommend the GTX2867 or the GTX3071 for a powerful midrange as well. Not just top end power. I want to be somewhere in the 325-350whp range.

GTX2867 would be just fine for that power level. That was what I personally was going to go with but i ended up going with a supercharger.

[diss7]

Seems there's a few of us that recognised these two turbos.

My issue with the compressor map of the gtx2867r is that you start passing the efficiency sweet point past 30ftlbs (270whp), push it to 40ftlbs (350whp) and it's fallen away off the efficiency map a fair way, but still on the map.

The gt3071r does not have this problem.

I understand the comments so far about turbine a/r. From reading others threads, reviews, talking to people, I had decided on the 0.86 exh housing on the gtx2867r. However now I'm leaning more towards the gtx3071r. I realise that this has a larger turbine. So, it's not just a case of choosing the same a/r, because it's not the same.

For example, would a gtx3071r 0.63a/r be a better choice for my goals of 300-320whp, but with headroom to push to 350whp, as the compressor maps indicate it would, and would you expect the gtx3071r 0.63 to have similar spool/choke performance as the gtx2867r 0.86. Even though it has the smaller a/r, this is based on a larger frame/turbine wheel.

[diss7]

Regarding car usage, car is street driven, but want the turbo for track performance. This doesn't mean that I want a lag monster, or 600hp. Rather I am looking at these parameters.
Peak power of 300whp - 350whp.
Efficiency range of turbo being centred around 6000rpm. I have chosen this point as it's the mid point of the rev range that I use on the track. (4800-7400)
So as I'm in that rev range I want to have the most average turbo efficiency.
The gtx3071r fits this bill nicely, it climbs the efficiency hill, gets to the middle of the peak efficiency island at what I am thinking will be around 6000-6500 revs, and then slightly tapers to redline.
Any bigger, and it won't taper at the top, but at the expense of the efficiency of the next gear, when the revs drop to 5000rpm.

This is why I'm where I am with the gtx3071r.

Obviously, although my operating rev range is higher, response is a big thing on the track. You're not 100% throttle, so rolling on throttle even at higher revs is going to happen, so response is still a concern.

I'm really trying to work out which turbine offers the best efficiency match to the way I have chosen the compressor.

As I said car is street'd, but I don't need boost to daily it. That said, I don't want go too big on the turbine a/r at the expense of 4500rpm on / off throttle response. Something that is very hard to determine from dyno graphs that are obviously only ever at WOT. I don't want to just choose a turbine a/r that makes a mininal/insignificant difference to the 6000-redline range, but at the expense of 500/800/1000rpm of turbo spool, which makes a massive difference to daily drive experience, for minimal track performance gain.

Maybe I'm asking questions that cannot be answered until I just do it myself.

I jus don't like the feeling of having to guess the turbine a/r off comparatively little information, compared to information/method of choosing compressor.

[Sellout]

Don't chase an efficiency number. If all you need is 300-350 whp, pick the smallest turbo that can make 350whp.

Seriously.

[asher187]

Originally Posted by Sellout

Don't chase an efficiency number. If all you need is 300-350 whp, pick the smallest turbo that can make 350whp.

Seriously.

I'm not trying to be a jerk, but why not?
He's going to spend a small fortune making his car run 'just right' imo spend lots of time researching planning and picking your parts, not just through anything 'good enough' on my car like a base avo kit

[Sellout]

Originally Posted by asher187

I'm not trying to be a jerk, but why not?
He's going to spend a small fortune making his car run 'just right' imo spend lots of time researching planning and picking your parts, not just through anything 'good enough' on my car like a base avo kit

Because all you get when you do that is more lag and a slower car.

If a 2867 is perfectly capable of hitting 350whp, what do you think you'll gain by using a larger, heavier compressor wheel than you need to get to 350whp?

Hell, you're already bringing a rifle to a fist fight by using a 2867 to reach a power number that's easy to hit with a smaller turbo. Why make your powerband even more unnecessarily narrow?

This is coming from someone who has owned both laggy and responsive turbo cars.

[diss7]

Originally Posted by Sellout

If a 2867 is perfectly capable of hitting 350whp, what do you think you'll gain by using a larger, heavier compressor wheel than you need to get to 350whp?

A compressor working more efficiently, so it is outputing the air cooler.

The more inefficient a turbo is (eg as you fall away from the efficency islands) the heat in the air it is outputting gets higher.

Thats at least my understanding. I could be mistaken.