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Daz was saying this is on a Hubber. Anyone care to have a guess at what the difference is between a hub and roller dyno?

My last figures were 375 kw at 4500, 425 kw at 5000 and 470 (6500) odd up top. Boost was 27 tapering back to 25 top end.

Interestingly was the difference between setting "2" and "3" on my controller. Setting 2 is 23 PSI (give or take) and the midrange was 50 KW less than setting 3.

It would be interesting to have both cars there, get out of one and into the other.

They're 63's IIRC.

Damn stout effort. I'm too wonder if the standard compact housing is/will hamper the GTX's. Power wise it seems up there but it's the apparent surge that might be an issue.

I'm fairly sure that chequered tunings dyno is setup so it's spot on with local roller dynos.

Gav made 500 on less boost, guess we won't really know without similar spec engines

Yeh, Trents is a RWD hub dyno, still he shouldn't need to justify his figures, it is on par with most of the other local tuners machines, but obviously dispenses with the wheelspin and over strapping required at that sort of power.

If you ran it on a roller I would expect to see minimal losses, although I still haven't been on Trents to compare my figures. As you say though, same dyno same day, or take them to the drags together is the only way to know.

Yeh, Trents is a RWD hub dyno, still he shouldn't need to justify his figures, it is on par with most of the other local tuners machines, but obviously dispenses with the wheelspin and over strapping required at that sort of power.

If you ran it on a roller I would expect to see minimal losses, although I still haven't been on Trents to compare my figures. As you say though, same dyno same day, or take them to the drags together is the only way to know.

Yeah, I was soley referencing to real gtx2863 compared to 2.5" gtx2863 with similar spec engines.

At a guess, the GTX stuffed into the stock housings will flow more air in the midrange compared to the anti-surge ones, which is why I heard what I assume was surge. (unless it was a cooler pipe or gasket, but it was only as it hit boost)

I would prefer the real housings myself, the slot is there for a good reason. Garrett wouldn't have added the complexity to the casting and machine work otherwise. But this was a stealth stock setup.

At a guess, the GTX stuffed into the stock housings will flow more air in the midrange compared to the anti-surge ones, which is why I heard what I assume was surge. (unless it was a cooler pipe or gasket, but it was only as it hit boost)

I would prefer the real housings myself, the slot is there for a good reason. Garrett wouldn't have added the complexity to the casting and machine work otherwise. But this was a stealth stock setup.

Thats right, 500kw, stock. even 450kw, stock is a good outcome. considering not many people crack 400 with -5's.

At a guess, the GTX stuffed into the stock housings will flow more air in the midrange compared to the anti-surge ones, which is why I heard what I assume was surge. (unless it was a cooler pipe or gasket, but it was only as it hit boost)

I would prefer the real housings myself, the slot is there for a good reason. Garrett wouldn't have added the complexity to the casting and machine work otherwise. But this was a stealth stock setup.

Okay so with all the GTX talk lately, here is my experience:

Put them on late last year when I built my engine. GTX2860's and keep in mind these are 400hp per turbo rating.

Used the anti surge compressor housings and added flanges to outlets etc to bolt to original pipework.

The good:

They are quiet,

They don't surge

After 4800RPM they really take off

Dynoed around the 480hp+ on Godzilla motorsports dyno

The bad:

Anti surge housings are not bolt in for GTR's

Don't come with turbine housing but you just use your busted -5, -10 bits that probably shit their bearings out from crap plastic bearing cages.

Laggy/lazy coming on, after a gear change due to anti surge ports.

Not suited to pump 98 as you really gotta pump some psi (25+) to take advantage of the stronger billet compressor wheel.

So the gun setup to get some sort of lower response with surge as a trade off would be the GTX's with a -5 front housing. Or run E85 or put em on a 3+litre engine.

I have some -5's ready to go onto my car, but still contemplating whether to give the GTX another chance with a different front from the -5's or just put the -5's in and enjoy. Ahh the joys...

Hey Sean,

After talking to you earlier in the year I also decided to stick with -5s as I'm gonna stick with 98 pump and I wanted a bolt on solution. I've had my fair share of headaches when I did my 3ltr a few years back.

pump some psi (25+) to take advantage of the stronger billet compressor wheel.

So the gun setup to get some sort of lower response with surge as a trade off would be the GTX's with a -5 front housing. Or run E85 or put em on a 3+litre engine.

I'm trying all of the above.

  • Like 1

Hey Sean,

After talking to you earlier in the year I also decided to stick with -5s as I'm gonna stick with 98 pump and I wanted a bolt on solution. I've had my fair share of headaches when I did my 3ltr a few years back.

Yep :) -5 are one of the best 'bolt on' setups if you want 330-470kw at the wheels depending on fuel and setup ;)

  • Like 1

Yep :) -5 are one of the best 'bolt on' setups if you want 330-470kw at the wheels depending on fuel and setup ;)

Did you use the -5 before on the non-built engine?

Or how do you come to the conclusion the GTX are laggier than the -5?

I have used HKS GT2530, GT-RS and now GTX2860 (all in their genuine housings) on a RB30 with stock cams, and the GT-RS were the only one which were REALLY laggy.

As they have been on the car inbetween I can´t really compare the 2530 to the GTX side-by-side, but my impression still is that the GTX are way better spooling etc. than the 2530...am I really that wrong?

BTW all turbos were running with about 1.5 bar / 22psi.

With my -5s converted into GTX 2863's it has really made a big difference to mine, and the lag Sean is talking of is a bit of a mystery, because I actually decreased lag and found a little bit more low down, and heaps from mid range to the top. Even with the cams on my -5s I found my cams to be a bit big 272/9.7 but now with the GTX turbos, the cams really seem to be more efficient, especially the mid range. I was going to take my cams back to a 260 but I don't think I need to as much now, the power delivery from these GTX's is fantastic IMO.

Hey Sean, maybe it's worth giving your 2860's another go, and get it tuned at NextUp, John really got the benefits out of mine quite nicely. And considering you have the same 2.8 as me, it doesn't make sense really that I have decreased lag with the 63's while you saw a decrease?

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