Gt3076r

[ls1ben]

Hello,

I am just wondering if someone could tell me if a GT3076 with .63 exhaust on it will pull all the way to 7500rpm on a rb25 or will it run out of legs in the top end?

Custom manifold and all bolt ons will be used. running around 16-17psi and external tial 44mm gate.

Also - anyone that actually has a gt3076 in .82 could you please tell me when u have full boost by?

Note - i have already done a search and read all the threads about the gt30, but didnt really find the answers to my questions.

Thank you.

[R31Nismoid]

It shouldnt loose "too much" in the top end.

Obvsiously is not going to have what a .82 would.

Although i would be using a smaller gate personally. t-smart 38 would be my pick

[lwboosted]

the .82 housing i have heard will give you full boost by around 3700 to 4000 rpm depending on cams, exhaust, tune, etc... it is different for every car, i think the .82 is the best suited for an rb25..

[ls1ben]

the .82 housing i have heard will give you full boost by around 3700 to 4000 rpm depending on cams, exhaust, tune, etc... it is different for every car, i think the .82 is the best suited for an rb25..

That being the case i think the .82 sounds like the go. would i be better off with the 38mm waste gate for that setup or 44mm?

[tridentt150v]

Do a search, sydney kid has a neat little formula for figuring out your wastegate size.

[STATUS]

what happened to the setup that was on it? all it needed was a TD06sh-25g and it would run high 10's or low 11's......

[2rismo]

Gate size isn't determined by turbo size. If you have a large turbo that you want to run at low boost, the gate has to work harder to bypass more gas - i.e. you'd need a big gate.

[Lithium]

Gate size isn't determined by turbo size. If you have a large turbo that you want to run at low boost, the gate has to work harder to bypass more gas - i.e. you'd need a big gate.

How does that work? All a wastegate does is relieve pressure from the turbine housing effectively - isn't it? I'd have thought it'd be fair to say that a large turbo, especially with a large turbine housing on a comparatively small motor running low boost wouldn't need much of a wastegate at all. Back in the day didn't turbos not even have wastegates, and the sizing was basically done such that they just free boosted - you lived with whatever you reached if you gave it the beans.

For what its worth, my car has issues with boost creep (still ) with a .63a/r GT3076R and the thing falling over high in the revs is DEFINITELY not an issue I have. Running a .6bar spring it has hit 20psi by 6500rpm and was still climbing.... hmm...

[2rismo]

How does that work? All a wastegate does is relieve pressure from the turbine housing effectively - isn't it? I'd have thought it'd be fair to say that a large turbo, especially with a large turbine housing on a comparatively small motor running low boost wouldn't need much of a wastegate at all. Back in the day didn't turbos not even have wastegates, and the sizing was basically done such that they just free boosted - you lived with whatever you reached if you gave it the beans.

For what its worth, my car has issues with boost creep (still ) with a .63a/r GT3076R and the thing falling over high in the revs is DEFINITELY not an issue I have. Running a .6bar spring it has hit 20psi by 6500rpm and was still climbing.... hmm...

Too small a gate and it won't be able to bypass enough gas to control boost. Simple.

[MBS206]

The wastegate allows the exhaust gasses to go AROUND the turbo, instead of through.

Run a small wastegate, won't be able to bypass much gas, meaning, you end up with a higher boost/creep.

[Lithium]

Too small a gate and it won't be able to bypass enough gas to control boost. Simple.

Well no kidding, but how do you define what too small a gate is?

That rule you said seems a bit too much of a blanket one. If you ran a T51R on a 4k I doubt you'd have issues with overboost, even with no wastegate.

[2rismo]

Well no kidding, but how do you define what too small a gate is?

That rule you said seems a bit too much of a blanket one. If you ran a T51R on a 4k I doubt you'd have issues with overboost, even with no wastegate.

Smartarse. I was speaking generally because your question was a general one. Manifold design has as much if not more to do with controlling boost levels effectively. Without talking about this and other aspects, I can't be more specific than I was. Don't be a f'wit for no reason.

[Lithium]

Smartarse. I was speaking generally because your question was a general one. Manifold design has as much if not more to do with controlling boost levels effectively. Without talking about this and other aspects, I can't be more specific than I was. Don't be a f'wit for no reason.

Sorry - hard to be light hearted on forums... It wasn't meant to be as snarky as it looks. Its a bit hard to get a hard fast rule on wastegate sizing, something I've been struggling with myself. There is another guy aside from myself using a 38mm on a GT3076R who has boost creep on this forum. He has a .82a/r turbine housing but is using an XSPower manifold. I am using a factory exhaust manifold and an internal gate style turbine housing with my wastegate mounted off the 38mm internal port. I've definitely not ruled out that there isn't enough flow getting to the wastegate, but I considered it worth noting.

[R31Nismoid]

XSPower... *sigh*. You'd be better off with the stock one IMO.

[2rismo]

It's equally important IMHO, to consider the direction of flow and the route the exhaust gas has to take to even get to the gate. I only know this in hindsight.

[Cubes]

What is also very important is dump design.

Besure to run a split style dump and 2" pipe from the wastegate which doesn't merge on a bend.

[KID18T]

Yeah I see and hear of the GT30R on Rb25det but what about the rb26 motor?

tossing up between the 35/40r and 3076r (def dont want a TO4z)

[The Mafia]

have a look at my dyno graphs. GT3037 (3076) iwht a .63IW garret rear.

http://www.skylinesaustralia.com/forums/in...p;#entry3100546

[discopotato03]

As I'm sure Gary would tell you the issue with large wastegates is how much gas they initially bypass when they first crack open . If the valve area is large for the application it bypasses lots , in fact so much that the exhaust gas velocity drops throught the turbine/housing enough to cost turbine/compressor speed so boost falls and so does the pressure signal to the wastegates diaphram . The result is cycling boost pressure and all sorts of tuning and power delivery antics .

Turbine housing A/R . The want to have an early boost threshold is easy to understand but you must remember that at anything below the actuators reaction pressure you still get more exhaust restriction than would be ideal . So basically the turbine housing size has most of the say whilever the wastegate is sealed shut and if the exhaust gas flow is too great for the combined housing and wastgate to handle , the boost and very importantly turbine inlet or backpressure rises . The system is trying to tell you that it can't regulate itself and efforts to force the gate shut only worsten the situation .

Take this to the grave and BTW this is not an attack on anyone just the facts . A wastegate is a "throttled" alternate exhaust gas path solely regulated by turbo boost air pressure . The aim is to throttle the exhaust gas velocity into the housing so that the speed of the turbine/compressor combination can be regulated .

The greatest downfall of this system is that its totally exhaust gas pressure insensitive . You don't usually get boost creep in an OEM application because they are put together by engineers that look at it as a complete package and everything is sized to suit that package .

IMO the 0.63 A/R GT30 turbine housing is not the best thing for a 56 comp trim GT3076R turbo - on any engine . To work well on boost the exhaust mass flow capacity is too low for its compressors air pumping abilities . To correct it either the turbine housing A/R needs to be increased to bring the exhaust flow capacity up , or the compressor capacity reduced to bring the airflow capacity down to match the lower exhaust flow abilities . As a side note my lists for HKS turbos show the 56T GT3037 (same cartridge as GT3076R 56T) was offered with 0.87 or 1.12 A/R turbine housings so they obviously didn't intend people to think these are a wide ranging response from low down turbocharger . I think I bashed at a post not long ago about the various GT3037 compressor trim options and their matching turbine housing A/R sizes .

So from std off the shelf available turbos either a smaller compressor trim GT3076R ie 52T or the real GT3071R with its 56 trim 71mm compressor would be worth a look . Cheapest sloution ? Fit the 0.82 A/R Garrett housing and curse HKS for not making their 0.73A/R turbine housing with a T3 flange .

The bottom line is your priorites of cost vs the result and only you can know that .

Food for thought , cheers A .

[Cubes]

Disco.

If one were aiming for close to 300rwkw would the GT3071r get there? I've never seen one run near those numbers on the dyno that I run on. They always top out around the 250-260rwkw mark.

As for the 52t, availability is the problem.

As I've said a few times before; an old mate of mine Steve initially received his HKS3037S with the .6 ext gate housing.

That made around 250rwkw on 1bar, spooled early but came on light a light switch.

He bought the .87 from the US.

He was running a decent plenum, exhaust manifold, cams and a loud open exhaust. That went on to make 320 something rwkw on a shade over 20psi.