3071 Garrett

[skylinecouple]

Your a gentleman Dave. How different is the dump you have compared to mine which is to suit a Garrett five bolt pattern as per the ATP U.S. site ? In other words what would have to be modified as I'm pretty handy with a welder. I am looking for a 3" dump and 2" wastegate pipe or a 4" bellmouth and from memory I think your was the former with wastegate pipe. I believe this is where my restriction may be as mine is a bellmouth with the wastegate feeding into the main pipe within 8". I have a splitter welded in but I just know there isn't enough gentle transition so has to be causing turbulance and not enough flow.

Only by maximizing exhaust efficiency can I be sure of any shortcomings with the turbo.

[BHDave]

It's a 3 inch main pipe and a 2 inch gate pipe that joins about 12 inches down the pipe. The flange of the gate section has been ground out to match the back of the turbo.

My exhaust is all custom and has been evolving over time to the point where it doesn't really follow the factory line any more or use the factory type flanges. Plus the rear half of the front pipe is a bit rough to be honest.

You would possibly lop it off just past the join and flare it out to 3.5 or 4 inches and redo the rest.

[discopotato03]

Well the engine has to be able to breathe in and out effectively meaning the ports/valve sizes/cam profiles/manifolds and exhaust all have to be up to it .

If you can , measure exhaust manifold pressure under load and compare it to compressor outlet pressure . If the hot side pressure is two to three times the compressor side then I'd say exhaust gas restriction is the problem .

The compressor/housing combination (71.1mm GT35 in 56T/ 0.50 A/R T04E) can pump enough air to make ~ 450 Hp/335 Kw , that doesn't mean a production engine can necessarily do it easily .

People have talked about R33 RB25 heads being a bit short on exhaust valve and port side size and the one example I know of that fixed these problems made more power/torque everywhere , could take more ignition advance I think everywhere as well . It's Tomei camshafts are the icing on the cake and it still didn't lose anything anywhere - all gains .

Personally I don't think you can lose with decent camshafts , it's the next best thing to reworking the head and they're a bolt in .

A .

[Cubes]

I think Garrett are pretty much on the mark with their ratings on 98RON PUMP fuel.

The GT3071r they claim 480hp ~358rwkw minus the usual 70rwkw drive train loss and you have 288rwkw.

Which is pretty much where the GT3071r's max out with a set of cams or ~260-270rwkw with standard cams.

The GT3076r they claim 525hp ~391rwkw minus the usual 75rwkw drive train loss and you have 321rwkw.

When I was running std cams it was a struggle over 280rwkw.

[skylinecouple]

Dave: Sounds like I could modify it to suit if you really want to pass it over for a small fee. Are you sure it will fit my turbine housing ? Trouble is the pipe is still 3" and I really need to go 3.5" all the way with 4" off the housing. Let me know if you want to get it gone and maybe I could use the first 8". ( sounds like my wife).

Disco: So exhaust cam may be the answer and I'm thinking to add a little overlap with cam gear and see what happens. If absolutely nothing, and I doubt it, then try inlet and exhaust cams just to free up the whole shooting match. Hey, if nothing else I should be able to add some timing.

Cubes: 280rwkws sounds very good to me. Though I doubt the end numbers would tell the whole story. I would expect torque to be stronger from 2,500rpm til redline. Should be a little crisper to.

Looks like some fine tuning is needed so might as well roll up the sleaves and get it done.

[Cubes]

Mid range.. punch 19psi in to it. Its a strange sensation powering on in third with fairly low rpm yet it having so so much pull.

I think I've said this before but the cams did wonders for over all power seat of the pants, low load gears come on stronger and with less throttle required. SimonR32 who did cams with his GT3071r .7 said the turbo was fairly laggy before the cams after it was an animal. Having been for a spin in it the setup was quite impressive. Near perfect. It really didn't feel laggy, grab the next gear and it had power.

I've just come back from fiddling with mine.

When it was tuned it was making 19psi through the mid and tailing off to 17psi with similar ambient temps to now. EBC on ~3mm preload on the actuator.

Before fiddling over 5000rpm it quickly drops to 16.6psi.

EBC off and boost is mega lazy. 11psi at 3000rpm 15.5psi at 4500rpm which it holds to 7000rpm. EBC on and it makes 19psi at pretty much flat 3100rpm rolling on the throttle in third from 60km/h.

EBC off.. I wound in close to 15mm preload. I figured it will be hot so go extreme the first time.

Interestingly mid range peaks at 20.9psi (it was tuned to 22psi) and still the bastard tails off but now to 16.8psi. The same as when it was running ~3mm preload but EBC turned on.

I noticed also the actuator feels quite soft/soggy to lift off its seat which it didn't when it was new. Now I can easily do it with one hand.

I remember my old std RB20DET actuator was harder to lift off its seat.

Definitely time for a new actuator.

[EVL-R33]

where can I get custom dump/intake pipes to suit GT3076R with external wastegate? Does anyone know a good place to get them made?

[Cubes]

A turbo exhaust place.

Head down to your local import workshop and they can sort it for you.

---

On a side note...

I disconnected/BROKE!! the actuator and it makes next to no boost until 5000rpm where by 6000rpm its making around 6psi.

[BHDave]

Dave: Sounds like I could modify it to suit if you really want to pass it over for a small fee. Are you sure it will fit my turbine housing ? Trouble is the pipe is still 3" and I really need to go 3.5" all the way with 4" off the housing. Let me know if you want to get it gone and maybe I could use the first 8". ( sounds like my wife).

Should fit. I doubt you'd gain much by making it 3.5 inch straight off the housing if you have a split dump but will probably make gains going 3.5 where they merge.

In progress pics of the important bits which i have posted before but can't be stuffed looking for

Wander round on the weekend, I'm only in eagle vale so not much of a hike. Worst case you save a heap of money by reusing the flange and bends for something