Jump to content
SAU Community

Recommended Posts

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.

Link to comment
https://www.sau.com.au/forums/topic/161904-gt3076r/
Share on other sites

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?

Link to comment
https://www.sau.com.au/forums/topic/161904-gt3076r/#findComment-3008991
Share on other sites

  • 2 months later...
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...

Link to comment
https://www.sau.com.au/forums/topic/161904-gt3076r/#findComment-3177099
Share on other sites

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.

Link to comment
https://www.sau.com.au/forums/topic/161904-gt3076r/#findComment-3177115
Share on other sites

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.

Link to comment
https://www.sau.com.au/forums/topic/161904-gt3076r/#findComment-3177143
Share on other sites

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.

Link to comment
https://www.sau.com.au/forums/topic/161904-gt3076r/#findComment-3177168
Share on other sites

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.

Link to comment
https://www.sau.com.au/forums/topic/161904-gt3076r/#findComment-3177210
Share on other sites

  • 2 weeks later...

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 .

Link to comment
https://www.sau.com.au/forums/topic/161904-gt3076r/#findComment-3201804
Share on other sites

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.

Link to comment
https://www.sau.com.au/forums/topic/161904-gt3076r/#findComment-3201915
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Latest Posts

    • Nah - but you won't find anything on dismantling the seats in any such thing anyway.
    • Could be. Could also be that they sit around broken more. To be fair, you almost never see one driving around. I see more R chassis GTRs than the Renault ones.
    • Yeah. Nah. This is why I said My bold for my double emphasis. We're not talking about cars tuned to the edge of det here. We're talking about normal cars. Flame propagation speed and the amount of energy required to ignite the fuel are not significant factors when running at 1500-4000 rpm, and medium to light loads, like nearly every car on the road (except twin cab utes which are driven at 6k and 100% load all the time). There is no shortage of ignition energy available in any petrol engine. If there was, we'd all be in deep shit. The calorific value, on a volume basis, is significantly different, between 98 and 91, and that turns up immediately in consumption numbers. You can see the signal easily if you control for the other variables well enough, and/or collect enough stats. As to not seeing any benefit - we had a couple of EF and EL Falcons in the company fleet back in the late 90s and early 2000s. The EEC IV ECU in those things was particularly good at adding in timing as soon as knock headroom improved, which typically came from putting in some 95 or 98. The responsiveness and power improved noticeably, and the fuel consumption dropped considerably, just from going to 95. Less delta from there to 98 - almost not noticeable, compared to the big differences seen between 91 and 95. Way back in the day, when supermarkets first started selling fuel from their own stations, I did thousands of km in FNQ in a small Toyota. I can't remember if it was a Starlet or an early Yaris. Anyway - the supermarket servos were bringing in cheap fuel from Indonesia, and the other servos were still using locally refined gear. The fuel consumption was typically at least 5%, often as much as 8% worse on the Indo shit, presumably because they had a lot more oxygenated component in the brew, and were probably barely meeting the octane spec. Around the same time or maybe a bit later (like 25 years ago), I could tell the difference between Shell 98 and BP 98, and typically preferred to only use Shell then because the Skyline ran so much better on it. Years later I found the realtionship between them had swapped, as a consequence of yet more refinery closures. So I've only used BP 98 since. Although, I must say that I could not fault the odd tank of United 98 that I've run. It's probably the same stuff. It is also very important to remember that these findings are often dependent on region. With most of the refineries in Oz now dead, there's less variability in local stuff, and he majority of our fuels are not even refined here any more anyway. It probably depends more on which SE Asian refinery is currently cheapest to operate.
    • You don't have an R34 service manual for the body do you? Have found plenty for the engine and drivetrain but nothing else
    • If they can dyno them, get them dyno'd, make sure they're not leaking, and if they look okay on the dyno and are performing relatively well, put them in the car.   If they're leaking oil etc, and you feel so inclined, open them up yourself and see what you can do to fix it. The main thing you're trying to do is replace the parts that perish, like seals. You're not attempting to change the valving. You might even be able to find somewhere that has the Tein parts/rebuild kit if you dig hard.
×
×
  • Create New...