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Why .82 A/r On Gt35?

T-Rex

By T-Rex,
in Engines & Forced Induction

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snozzle Mentor

snozzle

Posted
Posted
I and a friend are seeing a similar issue with a pair of 2510s on a 32R. Half a bar before 3000 is a piece of piss but it wont start building serious boost till close to 5000.

T-Rex do you have cam gears in yours or no gears? What cams too etc? I find it very strange the two cars suffer from the same problem.

I am also (semi) encouraging my mate to swap to a single, while I dont want him to fork the cash I also think the twin setup is easily flawed by the smallest of issues. In this case its only going 302rwkw where as he could attain the same figure from a 3076 and possibly have a lot of action a lot sooner.

Personally I am also tossing up now between a 35R and a 3076, I have previously run a 3076 for a brief period of time on my RB25 which was not laggy at all. Best description for delivery was like a big T28 on an SR20. Now I am contemplating how to get above 350rwkw without the sacrifice of too much response. The 35R IS the go but just how much response will be sacrificed I dont know.. As mentioned above a thought would be a 3040 with TS 1.06 rear housing. I have considered this setup put together with a high rev limit and a goal of 350rwkw MAX. Yet as stated.. the ATP housings leave some to be desired, a cast that could use some work and the fact its only really a T3 flange despite being TS.

All in all it seems difficult to track down the right info on these housings, I would want to see if the 35R is available in a good T4 TS housing as that may be the key to getting the power AND the delivery out of a sub 3L motor.

If i do find any setups on here with a rb26 running any trim or form of a gt3076 ill post it up here for discussion and compare it with a gt35r. See if the extra lag is worth it.

Wait.. didnt NYTSKY go from a gt3076 to a gt3582r and only 20-30kw more but a heap of more lag?

discopotato03 Grand Master

discopotato03

Posted
Posted

The interesting one Garrett does is the 0.94 A/R one for the Evo X specific GT3076R , twin scroll twin integral wastegate but with the mirror imaged Evo X mount flange . If you were going to ave a manifold made it could be worth a look .

I though I mentioned it before but GCG reckon Garrett make a GT ball bearing GT3576R turbo for the later XR6 engines , that would get you a larger turbine compared to a GT3076R and possibly do the trick for a torquey street RB30 .

IMO the issue with both GT30 and GT35 UHP turbines is the trim size - 84 trim . I think its too big and Garrett should do what they did to their GT37 and GT40 ball bearing turbines , bring the trim back to 78T to gain better response on petrol engines .

Harey Veteran

Harey

Posted
Posted

What are the advantages of a twin scroll single turbo to a set of twins?

I find it hard to believe that a single scroll single turbo has more smooth power delivery than twin turbos! As R31Nismoid mentioned those -5s are simply not in their efficiency range at 330rwkw.

Make sure you get a fair representation of each before you make the decision.

DR 32R Rising Star

DR 32R

Posted
Posted
What are the advantages of a twin scroll single turbo to a set of twins?

I find it hard to believe that a single scroll single turbo has more smooth power delivery than twin turbos! As R31Nismoid mentioned those -5s are simply not in their efficiency range at 330rwkw.

Make sure you get a fair representation of each before you make the decision.

A single Twin scroll has less plumbing than the twins. May spool earlier by design. Opportunity to high mount (debatable benefit). Either option depends on the turbo engine, entire set up, what you want etc.

hypergear Grand Master

hypergear

Posted
Posted
A single Twin scroll has less plumbing than the twins. May spool earlier by design. Opportunity to high mount (debatable benefit). Either option depends on the turbo engine, entire set up, what you want etc.

But on the same time the divider is also reducing the snail size, I would consider the twinscroll housing is touch bit smaller then what they are rated to. I persinally didn't notice any difference running a twin scroll or a single with the same CHRA.

DR 32R Rising Star

DR 32R

Posted
Posted
But on the same time the divider is also reducing the snail size, I would consider the twinscroll housing is touch bit smaller then what they are rated to. I persinally didn't notice any difference running a twin scroll or a single with the same CHRA.

Always interesting to hear practice over theory. I'm still interested in twil scroll, as an experiment at my cost. BMW and SAAB are running it lately, but that certainly doesn't make it any better!

R31Nismoid Grand Master

R31Nismoid

Posted
Posted
But on the same time the divider is also reducing the snail size, I would consider the twinscroll housing is touch bit smaller then what they are rated to. I persinally didn't notice any difference running a twin scroll or a single with the same CHRA.

Did you use a proper twin scroll manifold with the twin scroll housing?

Lithium Grand Master

Lithium

Posted
Posted
But on the same time the divider is also reducing the snail size, I would consider the twinscroll housing is touch bit smaller then what they are rated to. I persinally didn't notice any difference running a twin scroll or a single with the same CHRA.

Agreed on the first half, but everyone I know who has changed to twin scroll with the same (sometimes another "same" CHRA but with different housings, sometimes the exact same turbo but with the turbine housing swapped) CHRA and manifold modifications to suit have improved spool by a few hundred rpm, increased midrange torque by HEAPS and ended up with similar peak power.

discopotato03 Grand Master

discopotato03

Posted
Posted

The usual idea is to go larger in A/R when converting a given turbocharger to twin scroll , the reason is that you give the cylinders a larger volume and therefore area of lower pressure to blow down into/through .

The whole idea is to increase low and mid range torque by reducing the overlapping exhaust events in a common scroll or volute .

Why big TS housings work is that you reduce the turbine inlet pressure in the two scrolls so you need larger paths to easily vent the gas at the lower pressure . Its a win win for the engine and turbo in all respects except cost and waste gate convenience .

A .

GTScotT Grand Master

GTScotT

Posted
Posted
Its a win win for the engine and turbo in all respects except cost and waste gate convenience .

I have been seeing a lot of TS manifolds out with only one wastegate, some of the big jap brands and even 6boost.

I always wonder, when I see known big brand manifolds using one gate on a split manifold, just how much benefit there is to be had in TWO gates.

Reference:

http://image.nengun.com/catalogue/original...oyota_supra.png

Running one gate obviously makes the TS experience a negligible amount more difficult than a regular open housing setup.

wolverine Grand Master

wolverine

Posted
Posted

the HKS cast manifold would do much the same thing but the wastegate sits directly on top of the manifold with a thin divider. I can't imagine there being too much reversion back into the other bank of cylinders with this.

Completely divorcing them would be the Rolls Royce version but the above version should do the job and save a few dollars.

DR 32R Rising Star

DR 32R

Posted
Posted
The usual idea is to go larger in A/R when converting a given turbocharger to twin scroll , the reason is that you give the cylinders a larger volume and therefore area of lower pressure to blow down into/through .

The whole idea is to increase low and mid range torque by reducing the overlapping exhaust events in a common scroll or volute .

Why big TS housings work is that you reduce the turbine inlet pressure in the two scrolls so you need larger paths to easily vent the gas at the lower pressure . Its a win win for the engine and turbo in all respects except cost and waste gate convenience .

A .

Why I'm persevearing with the twin scroll idea, for a while for my set up.

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