CKit

Comparing Reapur's dyno and ours confirms why you'd want a GTX3071R over a GT3076R, IMHO.

Compare average power and torque from 5000-8000 rpms and you'll see the marked difference in usable power.

CKit

Again, that's silly unless you know a road racer than plans on driving an S2000 under 5000 rpms. No mountain, just plateau at those rpms. Isn't a stock S2000 designed to be driven between 6000-9000 rpms anyway?

That's the only rpm range you really care about if you are on track. I know that the OP was talking about street driving, but some people (who obviously don't road race) brought in track driving discussion.

CKit

Taking the 17 psi numbers compared to your 10 psi numbers:

At 5000 rpms: You = 240 hp, Me = 310 hp.
At 6000 rpms: You = 310 hp, Me = 420 hp.
At 7000 rpms: You = 380 hp, Me = 440 hp.

So just to put it in perspective, it's not about the peak hp. It's about area under the curve. We're spooled and running 1000 rpm sooner, making 100 hp more at the same speed / rpm assuming that gearing is the same. That's a huge difference.

If your GT 3076R would be in the 500s at 17 psi, would it only get there at the very top of the rev range? What good is that?
I agree with others, if you're going to only push 10 psi, you'd be better off with a 28 series turbo and get more usable power early rather than way late.

Our torque and hp curves are a little different than what you would normally find. That's why we make so much torque compared to others in the same hp range.

The GTX3071R is just a better turbo all around than the GT3076R. And I've driven both on our car on road courses. Will post some video when we get back from Circuit of the Americas in a few weeks. And I guarantee that I'll never be below 5000 rpms unless the engine blows...

hybrdthry911

Please share that info with us, all the research I've done shows that the GTX spools 300rpm faster and has better flow than a GT equivalent.
[/quote]

Thanks for the help sofar guys!

Check this link and scroll down
https://www.s2ki.com/...-turbo-for-s2k/

I also run a us 93 octane fuel and have the option to go e85 in the future...

I dont mind getting some recommendations to go gt35, as long as there is some feedback why i should go to a bigger size. I only drove my own greddy turbo s2k and a vortech 400whp sc s2k once. That was great from 6-9 but was lacking low/mid range...

I do alot of road racing in canyons and the setup needs to be non laggy and responsive. I dont like a turbo setup that gains like 100whp in less than 1K rpm ( those gt35 setups tend to do nothing dow low and suddeny BAM 100whp extra from 5k to 6k.. That would not be any usefull unless im on the highway....

Can anyone tell me if the gtx3071r will outperform a gt3076r at around 14 psi?

Thanks for helping!
[/quote]

It won't, the GTX series of turbos give extra headroom for power, they dont put out the same power at equivalent psi. I'm at 10psi and pushing 444whp in comparison CKit at 17psi is only pushing 473.5whp using a GTX3071. my GT3076r would be well into the 500s @ 17psi.


If youre referring to Metros post of the Ptuning dyno graph, Id like to point out that they are two different cars on different days. Look at the information box lower right side. There are a number of variables that could change spool so we cant say for sure using your example. They are also not at same boost levels.
[/quote]

Garrett seems to disagree with you. They show the GTX3071r flowing equal or more air at all boost levels when compared to the GT3076r. Go check out their compressor maps for yourself.

Thunder-rush

Read this article:


http://www.motoiq.com/magazine_artic...p-details.aspx



The maps above show the 71mm diameter compressor wheel of the GTX3071 flowing about the same as the 76mm compressor wheel of the older GT3076. As mentioned earlier, the smaller diameter wheel must spin faster to achieve the same mass flow rate and pressure ratio. At the point of 50 lbs/min and 2.5 PR, the 71mm wheel spins about 125,000rpm versus about 120,000rpm for the 76mm wheel.

Though the GTX3071 compressor flows about the same as the regular GT3076, it requires a higher compressor speed to do so. In general, many turbos have a value of U/Co that is lower than the ideal 0.7. In this case, replacing the 76mm compressor wheel with the equal flowing 71mm GTX wheel increases the turbine tip speed. The increased turbine speed increases the U in Blade Speed Ratio, U/Co, bringing it closer to the ideal and improving turbine efficiency. The increased turbine efficiency combined with the lower mass and inertia 71mm GTX wheel makes the GTX3071 more responsive than the regular GT3076.

Compressor and turbine maps have many details that go into them. They have to use corrected values in order to be comparable much like how engine dyno results are all corrected to a SAE standard. A full turbine map shows very important information relating turbine mass flow rate, pressure ratio, and efficiency to each speed line of the compressor. These three characteristics of a turbine can be affected by a number of variables with turbine housing A/R sizing being the primary variable that an end-user can alter; different A/R sizes can be tested to find the best combination of power and drivability for a particular application. The other parameter that a user can decide on is the compressor to turbine wheel sizing. Altering the size of the compressor wheel versus the turbine wheel alters the blade speed ratio affecting turbine efficiency and responsiveness of the turbocharger. All this information from turbine maps really aids the selection of the proper turbocharger for an application. Hopefully, the turbine map is now a bit less mysterious and the concepts of A/R size selection and wheel matching is clearer.

Thunder-rush

Please share that info with us, all the research I've done shows that the GTX spools 300rpm faster and has better flow than a GT equivalent.
[/quote]

Thanks for the help sofar guys!

Check this link and scroll down
https://www.s2ki.com/...-turbo-for-s2k/

I also run a us 93 octane fuel and have the option to go e85 in the future...

I dont mind getting some recommendations to go gt35, as long as there is some feedback why i should go to a bigger size. I only drove my own greddy turbo s2k and a vortech 400whp sc s2k once. That was great from 6-9 but was lacking low/mid range...

I do alot of road racing in canyons and the setup needs to be non laggy and responsive. I dont like a turbo setup that gains like 100whp in less than 1K rpm ( those gt35 setups tend to do nothing dow low and suddeny BAM 100whp extra from 5k to 6k.. That would not be any usefull unless im on the highway....

Can anyone tell me if the gtx3071r will outperform a gt3076r at around 14 psi?

Thanks for helping!
[/quote]

It won't, the GTX series of turbos give extra headroom for power, they dont put out the same power at equivalent psi. I'm at 10psi and pushing 444whp in comparison CKit at 17psi is only pushing 473.5whp using a GTX3071. my GT3076r would be well into the 500s @ 17psi.


If youre referring to Metros post of the Ptuning dyno graph, Id like to point out that they are two different cars on different days. Look at the information box lower right side. There are a number of variables that could change spool so we cant say for sure using your example. They are also not at same boost levels.
[/quote]

Garrett seems to disagree with you. They show the GTX3071r flowing equal or more air at all boost levels when compared to the GT3076r. Go check out their compressor maps for yourself.
[/quote]

I agree with you. The gtx3071r flow map looks better than the regular gt3076 turbo and they flow about the same. By looking at the maps given all else equal the smaller gtx71r model will spool faster and be more efficient at up to 500whp range.

CKit

Thank you both. That's exactly why we switched to the new turbo. Science doesn't lie.

And from a personal standpoint, I can tell you the GTX spools noticeably faster.

Take home points, IMHO:
1. Only get as much turbo as you're going to need, running a mongo turbo with a small displacement engine at low boost is a recipe for lag and inefficiency.
2. Using data from a compressor map, gear / speed calculator, plus the appropriate rpms from a dyno plot you can get a good idea of how much turbo you need.

CKit

To the OP, one other thing that helped us decide on a turbo was watching videos of the GT3076R and GTX3071R spool.

These are both the GTX3071R at 17 psi:
Straight line spool at max rpm shifts (speed run at 64 seconds into video).
[media]http://www.youtube.com/watch?v=ATdo_5mbDwk?t[/media]


Usability in part throttle and "4000-6000" range (2nd gear, aftermarket gear ratios).
[media]http://www.youtube.com/watch?v=qlTJxZvR6Hg[/media]

I can tell you that you WANT a nice flat torque curve, but 4000-9000 (really 5000-8000) is the part of the dyno curve that you care about. If you're under that rpm, shift to a lower gear. If you're above that rpm, you're going to need to shift up anyway. You'd never start an acceleration zone at redline, right? That last 1000 rpms isn't going to be used nearly as much as your 5000-8000 rpm range. So look at your dyno graphs in that section.

CKit

Also, for people unfamiliar regarding motorsport application:

WRC = World Rally Championship.

Small engines, turbos, need for throttle response, peak hp restriction.

Notice anything about their torque and hp curves?

http://www.motorsportforums.com/wrc/...-part-2-a.html




Want to argue with the WRC about their "mountains" of torque and hp?
Note that "S2000" is the rally class and not Honda S2000....

It's the nature of the beast. In motorsport, you ignore the lower rev range. Get it spooled fast and once it's spooled, keep it spooled.

For their application, they want even quicker spool (note they're fully spooled by 3000-3500 rpms). The mountain isn't an issue, it's having the skill to keep it on the plateau.

Another plot, higher hp class:

CKit

Here's what those "mountains" look like in real world use.

Skoda:

[media]http://www.youtube.com/watch?v=QcbyK10P9vk[/media]

If the OP is doing "Touge" or mountain driving, rally is probably the closest thing to it.