Garrett Gt3071r

[BHDave]

I assume you have a .63 housing? I also fitted the 38mm flapper which didn't completely fix the creep issue (though it did stabilize at 1.4 afterwards) and introduced a new issue of back pressure blowing open the flap above 5k and so not being able to hold more than 1bar.

You have the same issues that i did before modding the IW.

I had decided to go a 44mm external gate.

[MR.E]

Another update, I've disconnected the actuator rod and im still getting at least 1b of boost so not good. I've emailed GCG who said they hadnt had any reports of boost problems, so I asked if it could be down to the split dump pipe and their last email reply was....

I do know for a fact that our RB25DET high flows we do will boost creep if the car doesn't have a cat, but I can't see why a further open flow dump pipe would have a problem (such as the D2 picture you sent). Apart from trying that flying dump pipe, I cannot suggest anything else as the flapper/porting we do is as big as you can possibly go in that exhaust housing, so there is no more room for porting.

Regards,

MICHAEL RAMSAY

So basically I've paid for a turbo with no way of controlling the boost

[discopotato03]

From what I hear about these real IW GT3071Rs they sound like they are if anying too responsive in the Garrett GT30 0.63 A/R turbine housing . Has anyone here used one with the next size up (0.82 A/R) IW turbine housing ?

With IW turbine housings the exhaust can only go out past the turbine or turbine and waste gates vent path . If the wastegate cannot bypass enough of the overall exhaust gas volume then you cant't control the speed of the turbine or boost pressure . The waste gate valve can only get so big and after that the only way to get more gas though the housing is to use one with a larger internal passage - larger A/R .

The closest Garrett turbo I know of (concept wise) is the smaller GT2860RS and it uses reasonably big housings for a GT28BB turbo . It has a 0.86 A/R turbine housing (largest in GT28 range) and its compressor housing is a 0.60 A/R T04B one - usually found on turbos with 70-71mm comp wheels rather than 60mm ones .

The 3071R already has the upsized T04E comp housing (usually used with 76mm comps 3071R's is ~ 71mm) .

I can't say for certain how much response you'd lose with a 0.82 A/R GT30 housing compared to the 0.63 version on a GT3071R but I can say that you'd get more gass through the turbine before the gate opened with the 82 size - if the exhaust system could support it .

Until its tried we won't know for sure , cheers A .

[RS500]

isn't skylinecouple using the GT3071R with A/R .82 exhaust housing?

it looks like if the .63 is required, external wastegate is the best way to control boost.

Edited August 1, 2008 by RS500

[BHDave]

isn't skylinecouple using the GT3071R with A/R .82 exhaust housing?

it looks like if the .63 is required, external wastegate is the only way to control boost.

edited

Yep gary is running the .82 housing and surge modded compressor housing.

[RS500]

edited

Yep gary is running the .82 housing and surge modded compressor housing.

hehe, yeah sorry that's what i meant.

that's how i ran my GT3040R (with A/R .63) on my cossie a few years ago and no problems causing boost, even given the massive 82mm comp wheel.

although, it's restrictive and mismatched turbine combinations that usually cause boost control problems.

i would've thought the better matched GT3071R (with smaller comp wheel) would alleviate these problems given the much smaller amount of restriction/backpressure with the larger 60mm GT30 exhaust wheel.

maybe there's a flaw in the housing design??

[BHDave]

The issue is through the midrange, it stabilizes at the top end as the compressor starts to run out of puff and the amount of exhaust that needs to be vented via the wastegate is reduced.

I'll happily state it here after playing guinea pig, DO NOT buy a 3071 in .63 IW housing for an rb25. It will not work. We now have 3 people with boost control issues, me, MR.E and -33-. I've spent the extra money on the 38mm wastegate flap which didn't entirely solve the original issue and added a new one. It sounds like MR.E has as well.

I would only recommend the .63 if you were to go the ex gate route.

[RS500]

out of curiosity, how much are you guys paying for the real GT3071R?

[discopotato03]

If someone is running a Garrett GT30 0.82 A/R IW turbine housing on their 3071R/RB25DET I'd like to hear what they think of this combination .

A problem that exists in IW turbine housings is that exhaust gas at high speeds has momentum and is not real keen on changing direction and going out through a hole in the side of the main passage .

It seems that there is the usual juggle here of trying to get an early boost threshold whilst not having the hot side choke when its all up and happening .

A larger AR housing will mean higher gas flow capacity but the compressor speed will be a little down so you may not get that "vertical" boost pressure rise - if thats what you are looking for .

I reckon the thought that goes into turbos which favour the hot side (like GT2860RS's and these real GT3071R's) is low exhaust restriction , it sort of fits in with the not so much high boost but high air flow rates at modest boost pressure and low (lower than usual) exhaust manifold pressure . It probably means the engine needs to be set up to make reasonable low end torque ie good head/mild cams/bit higher CR/bit more advance . Having the larger rear housing in these circumstances should be less of a problem if the engine can stand on its own two feet in a pre supercharged state .

Basically same circumstances as say a GCG RB25 Hi Flow with the RB25 or VG30 turbine housing , its what the factory wanted from the later R34 spec RB25DET . They just went about it with better cams and more effective variable cam control .

Cheers A .

[dangerman4]

would it be possible to port drill a exhaust housing like a comp cover to elieviate (spelling) some of the back pressure?

if you were to drill say 5 x 1.5 mm holes around the ex wheel would this help?

the 10 beers ive had are making me think out side the square

[discopotato03]

Not really , you want the exhaust gas to go through the turbine to drive the compressor . If you want less pressure you need a larger volute passage inside the housing - less restriction=lower gas speed=lower pressure .

The problem with regulationg turbine speed (with a waste gate bypass) referencing off compressor outlet pressure is that exhaust manifold pressure gets ignored . An external gate doesn't fare any better but it can be placed so that exhause gas will flow through it rather than past it - if the manifold is properly designed .

Cheers A .

[Cubes]

Simonr32 went the .7 cast rb housing; dropped a larger flapper in it that pretty much resolved issues.

Give me some boost creep mine tails off to 17psi.

[skylineboy84]

my hks turbo just died a few days ago, and im getting one of these turbo put on next week cant wait to see how it gos

[BHDave]

Simonr32 went the .7 cast rb housing; dropped a larger flapper in it that pretty much resolved issues.

Give me some boost creep mine tails off to 17psi.

his used the cropped turbine so no real comparison. Great result though.

mine has boost creep and tails off to 1 bar

[skylinecouple]

I can say I am very happy with my combination and would go so far as to say it is perfect for every day driving. Put your boot into it and go, any time any place. Even under 3,500rpm there seems to be enough air flow to bring you onto boost very quickly. The point I'm trying to make here is I have no boost control issues at all. If anything I have to wind a bit more tension onto the actuator to get my 14lb actuator to actually BE 14lbs instead of the 13lb it is. I am dropping boost from 19lbs to 16lbs, not good. Ideally I would like 18lbs across the board but I'll fix that this week. As I have mentioned elsewhere in these forums, The RB25 needs a .82 housing. Deciding on 3076 or 3071 is really about if you want 300kws or 260-270kws. I decided I would like 260 and be happy with that. Trouble is, I want more. Should I have taken delivery of the 3076 I ordered as well ? I am kind of glad I didn't, if more power is needed then cams will go in. I have found the .82 gives me bucket loads of torque at low revs but doesn't break into wheel spin yet just loves to rev so freely in the top end. If I had a .63 I know it would light the tires at low speeds and then choke when the revs get serious, not to mention the very real problem of boost control. The RB25 cannot swollow a lot of air at low revs, ok, I know your going to say what about the standard turbo but that doesn't push anywhere near the air a 71mm wheel does. The .82 even handles the 76mm comp wheel no problems from what we have seen.

[robots]

So to summ it up. GT3071R with 63AR is not a good combo with rb25det ?

[BHDave]

Nope.

the internal gate .63 is rubbish, the .63 with decent boost control would be fantastic, which is why i never considered a swap to a .82. While i respect Gary's opinion, i disagree, as i have watched my car see 20+ psi below 3k with no hint of surge and i have close to 50rwkw more between 3 and 3.5k before it evens up by 5k

It's not for everyone, but it works for me. My car was track driven so it only really saw WOT. The .82 is actually showing worse response than my old plain bearing T300's (T3/4) and makes less power as well but i'm sure at light throttle it would be chalk and cheese.

horse's for courses i guess

[Cubes]

his used the cropped turbine so no real comparison. Great result though.

mine has boost creep and tails off to 1 bar

If anything a cropped turbine will place a greater requirement on the wastegate.

As with the XR6T turbo's.. When they slap a larger flapper in there they have to go a tougher actuator and even still its a fine balance between going to big resulting in blowing the flapper open and creep.

You also went with a good bell mount dump didn't you?

In your case I would simply shove an 18psi actuator on it and be done with it. It will spool well and hold 18psi up top.

[discopotato03]

Skylinecouple my experience with the smaller GT2860RS on the old FJ20ET was pretty good , what I liked about it was the way it made positive pressure at quite low engine revs . The term I've used is the "windmill" effect where there is not a great deal of positive inlet manifold pressure but it makes for good low down easy lazy drivable torque .

I'd reckon the positive but low manifold pressure would allow the engine to run closer to best mean torque ignition timing , especially since the exhaust manifold pressure should be low as well . Methinks that with good tuning and reasonable pump fuel the consumption figures should look pretty good too .

The trade off was always going to be the compressors ability to have enough pumping capacity to maintain higher boost pressure at higher engine revs .

To me having lots of mid range punch is what road cars are about because I believe thats what works with production gearbox ratios .

As I said turbos biased a bit more towards the turbine side are not going to be top end screamers , not enough compressor to do that . The trade off is (sounds like with the 0.82 A/R 3071R on RB25DET) the lower end and what happens down there at less than wide open throttle .

I guess once you throw ported heads and mild cams into the equation it should make more torque everywhere .

I think torque numbers are more interestiing than boost numbers so maybe need to see a dyno printout of this combination of parts .

Cheers A .

[robots]

So if I run external wastegate with gt3071r ar63, it should work, right ? I'm thinking about putting ext. wastegate on stock exhaust manifold. Something like 38mm TIAL. what do you think guys ?