GTX 3071 .63 v KKK26/27 # 6

[A80Avant]

I have to say it again. GTX has the same spool and lag as the GT series. They just produce more power. So 0.82ar will not be like an rs2 turbo in spooling.

My 3071R when on 0.63ar was giving on 3d gear 2bar at 3500-3600rpm on adu cams. The 0.82 would take it 300rpm later. But surely more powerful and longer boost levels to the top of the rev range. But you will like it anyway!

[Ross]

I personally didn't get on with the surge on my old gt3071, i'd be very interested to have a ride in the newer gtx 3076 variety...

The extra lag in the K26/7 hybrid doesn't bother me, it makes similar torque at 3k with 0.5bar as a stock K24 with 1bar anyway thanks to the headwork... so round town it's just as driveable and responsive although yes, as PRJ says taking off in 2nd at 10mph you will not be outdragging the TDI brigade. Only when you hit the 30mph speed limit will you surge ahead and you'll be doing 70mph and losing your license about 2.5 seconds later...

I do love the instant torque of the RS6. It's planted and i feel like the improvement in handling over the RS2 hides the extra weight. I love the luxuries; it eats miles and kills everything on the road without feeling tiring. But I miss the RS2 like hell, it's alot more fun to drive and 'raw' in every way. It takes more to drive it fast but it's more rewarding. and it's the one I would never get rid of. Although I'm torn between the non-res miltek V8 sound and I5...

Yes - I am scared to try and RS4 as I suspect it would be 'best of both' - but my RS2 is going nowhere, although it is now a 3k annual garage queen and the RS6 is my daily. The RS6 will be replaced with something more economical as soon as my mileage goes up from 300 a month!

Oh - I can get my 3 kids in the RS6, can just squeeze them in the RS2, however with the RS4 / B5 A4 platform there's not enough room until all the kids are front facing, else I'd have had one over the RS6.

[A80Avant]

Nice post Ross but this is more about the above gtx setup.

As mentioned before the headwork is something that I would say is best to have on these power levels. That in conjunction to fine tuning you don't have the surge problems with the small hotsides on garrett. Been there with 3 different garrett options now and I cannot say I have surge problems.

[prj]

I have to say it again. GTX has the same spool and lag as the GT series. They just produce more power. So 0.82ar will not be like an rs2 turbo in spooling.

My 3071R when on 0.63ar was giving on 3d gear 2bar at 3500-3600rpm on adu cams. The 0.82 would take it 300rpm later. But surely more powerful and longer boost levels to the top of the rev range. But you will like it anyway!

GTX3071R/0.82 should be much better than GT3076/0.63.
Similar spoolup to a GT3071/0.82 without surge I hope. I don't know if the GTX compressors extend the surge line or not in real life, but from graphs it looks like it will be a little bit worse.

These cars really need headwork, I have seen surge with smaller housings on everything now. KKK, Holset and so on. Garrett is definitely the worst for it, but it's because the ramp rate on a ball bearing turbo is so good, I don't think it's a wheel design problem.

[A80Avant]

I'm comparing GTX to GT equivalents. Not gtx 3071 to gt3076. Lots of variables there to make anything out it it

[macspring]

JP did the head, he may be able to comment.

Thanks for people's interest.

[prj]

I'm comparing GTX to GT equivalents. Not gtx 3071 to gt3076. Lots of variables there to make anything out it it

Well the OP got what he got, so here's to hoping that it is a GT3076R with spool of 0.63 and top end of 0.82.

[A80Avant]

Well the OP got what he got, so here's to hoping that it is a GT3076R with spool of 0.63 and top end of 0.82.

It will be interesting to see if it hits the spot. To my experience it seems that the AR of the hotsides on the Garrett's plays a larger role than the overall weight of the compressor wheel. So in this case the compressor wheel of the GTX is lighter than the GT3076 and the turbine wheels are the same. The GTX being completely new design will reach and outperform the old GT3076 at least on paper and in this case the 0.82AR will surely do vs the 0.63AR of the GT.

The most interesting bit of the whole equation is the lag. Personally from GT3071 0.82 that you have tuned and mentioned in the past, I get the impression that those tended to kick at 4000rpm on 3d gear anyway. So my bet is that the GTX will do the same, give or take 100rpm.

Given the fact that the GT3076 0.63AR was somewhere around 3800ish but with different engine bits and cams presumambly it will be somewhere there.

My main reason for being pro 0.63ar is the fact that the turbos build up the boost quicker from 3000rpm or sooner on higher gears whereas the 0.82ar tends to be completely dead till 3500rpm until it wake up even if the absolute overboost rpm point is equivocal. That was one of the reasons why my 0.82ar hotside is still tucked in a box.

[george21]

Well the OP got what he got, so here's to hoping that it is a GT3076R with spool of 0.63 and top end of 0.82.

Prj, what about holset hx35/26 hybrid. What you can expect on standard aby with 7a cams, bigger injectors. Full boost, bhp, nm?? Is that good setup on budget?

[Rocco]

Vas,I have never tried 0.63AR turbos, but i am very happy with the 0.82AR lag

nice overall street driving and if i want boost and i am in the wrong gear just downshift and 2.2bar

did you try well the 0.82 version?

i know is not comparable but i have the same lag with my race engine an GT3076R than K26/27 6# and 3b engine with some porting job done

[prj]

It will be interesting to see if it hits the spot. To my experience it seems that the AR of the hotsides on the Garrett's plays a larger role than the overall weight of the compressor wheel. So in this case the compressor wheel of the GTX is lighter than the GT3076 and the turbine wheels are the same. The GTX being completely new design will reach and outperform the old GT3076 at least on paper and in this case the 0.82AR will surely do vs the 0.63AR of the GT.

I did some quick photoshopping, and lined up the GT3076R vs the GTX3071R.

The most interesting bit of the whole equation is the lag. Personally from GT3071 0.82 that you have tuned and mentioned in the past, I get the impression that those tended to kick at 4000rpm on 3d gear anyway. So my bet is that the GTX will do the same, give or take 100rpm.

3800 on a 3071R/0.82, not 4000. 4100-4200 is where a 3076R/0.82 is.

My main reason for being pro 0.63ar is the fact that the turbos build up the boost quicker from 3000rpm or sooner on higher gears whereas the 0.82ar tends to be completely dead till 3500rpm until it wake up even if the absolute overboost rpm point is equivocal. That was one of the reasons why my 0.82ar hotside is still tucked in a box.

This is true if you are comparing the same turbo, but boost ramp rate is going to be roughly the same if the full boost is at the same RPM.

Anyway from the picture, it looks like the GTX3071R performs roughly the same at the top end (we are going to slam into the right side at a PR of about 2.2-2.3), maybe flows a tiny bit less.

What I like is, that at about 2.3-2.4 PR the surge line is already quite a bit better on the GTX3071R, that's where usually the surge problems are...
So at least on paper, the GTX3071R/0.82 should spool more or less the same as the the GT3076R/0.63 and GT3071R/0.82, however it should make about the same power as a GT3076R/0.82 and also there should not be any surge issues with this turbo at all.

This is on paper - let's see how it is in practice.
Although I think with JP's head porting, a 0.63 A/R turbo would not have too many surge issues either, maybe in top gear if going WOT early in rev range.
But for me it looks like a winner. Probably the best GTX compressor with the GT30 turbine...

[prj]

Prj, what about holset hx35/26 hybrid. What you can expect on standard aby with 7a cams, bigger injectors. Full boost, bhp, nm?? Is that good setup on budget?

This is kinda off topic of you barging in here, but...

The benefits of that turbo are:
1. Really cheap.
2. Really reliable.
3. If you manage to screw it up, replacement parts are again really cheap and you can assemble and disassemble it yourself, because everything is individually balanced, so no need to balance the turbo.

I wouldn't fit 7A cams with this turbo, too laggy for me. 7A cams are better with a HX40
Full boost @ 4000, and since the turbine wheel on the HX35 is bigger than the GT30, the top end power is between GT3076/0.82 and GT3076/0.63 somewhere. Transient response is less snappy though.
I've run 2.2 bar and 1.8 to redline on that turbo. Power depends on supporting mods, I'd say between 450 and 490 hp.

[george21]

This is kinda off topic of you barging in here, but...

The benefits of that turbo are:
1. Really cheap.
2. Really reliable.
3. If you manage to screw it up, replacement parts are again really cheap and you can assemble and disassemble it yourself, because everything is individually balanced, so no need to balance the turbo.

I wouldn't fit 7A cams with this turbo, too laggy for me. 7A cams are better with a HX40
Full boost @ 4000, and since the turbine wheel on the HX35 is bigger than the GT30, the top end power is between GT3076/0.82 and GT3076/0.63 somewhere. Transient response is less snappy though.
I've run 2.2 bar and 1.8 to redline on that turbo. Power depends on supporting mods, I'd say between 450 and 490 hp.

Sorry for hacking in guys !
And thank you for info Prj. So is it worth to spend 1k. On Gtx turbo when you can have holset for less then half? That is why i have asked

[A80Avant]

Sorry for hacking in guys !
And thank you for info Prj. So is it worth to spend 1k. On Gtx turbo when you can have holset for less then half? That is why i have asked

A lot of people have asked that question and a few that tried this option were not that excited with the result. Others were. The fact that eventually more garrett's are sold than holsets on these engines proves a point. I tried for a short while the HX40 super and didn't like the way boost was building up no matter how much hp it made

[macspring]

No worries with the slight topic creep, I've done it enough times myself.