GT3071 or GT2871 on rb20

[quincy777]

Hi all,

I have had mixed response on which turbo to get, details are as follows.

Car is r32 sedan. I have good support mods - apexi PowerFC, apexi FMIC, fuel pump, GTR injectors, full exhaust, pod with cold air box and feed.

I have not upgraded turbo on rb20 before only on rb25 and SR20. Ben (racepace) is tuning the car I am aiming for good street performance but occasional track day performance. I do drive the car 500-800km per week. Turbo options are all interally gated and low mount. Which one???

1. GT2871 (390hp) 71mm comp wheel, 48 trim, .68/.86 housing.

2. Gt2871 (440hp) 71mm comp wheel, 56 trim, 68/.86 housing.

3. Gt3071 (450hp) GT30 turbine wheel, 71mm comp wheel, 56 trim, 68/.86 housing.

Just want to keep rb20 and make it quick, responsive, and reliable.

Cheers

Cam

[Bl4cK32]

Ben (racepace) is tuning the car

ask him what he'd recommend for :

good street performance but occasional track day performance

[Waldo]

just get the biggest one GT3071, they are all dual ballbearing, it shouldnt be to laggy with the .68 exhaust side

[Busky2k]

I'd go for the Gt2871R with a 0.86 housing (to make the most of the high flowing compressor). However I'm not sure of the streetable differences between the 2 trims. My guess is alot more lag with the larger trim. Maybe discopotato03 can chime in...

The GT3037 is just too big for a street RB20 IMO.

[Waldo]

just get a set of cams and dial them in and the 3071 should be pretty good.

[R31Nismoid]

ask him what he'd recommend for :

Exactly what i was going to say.

[Cubes]

I wouldn't recommend any of them for street use.

Expect 4.5k+ boost with any of the above.

I would personally look at a Roy setup. The TD06-20G appears to work damn well. Lots of average power from 4k onwards.

[discopotato03]

The 2000cc six is a bit harder as it needs to work over a such a wide rev range . I would look at the GT28RS as well if the T28 flange was being adapted to the T3 pattern manifold . Basically the GT28RS's 60mm compressor is against the wall at something up to 33-34 lbs of airflow . The rough rule of thumb puts its power potential at 340-350hp . The GT2871R in 56 trim is supposed to flow 44 lbs/min or 440-450 hp potential for the compressor , not sure if the turbine can pass the required exhaust gas flow for power claimed though .

Trying to guess what feels good for you is the hard part , for me the broad flat torque curve is what its all about . I personally don't need a power number from my car to make life livable . I already own a GT28RS so thats what I'd try first , it was a ball tearer on an FJ20 (for road) though it had quite reasonable off boost torque from aftermarket management . I would not use either of these turbos without the .86 turbine housing , the 28RS doesn't know what lag is with it anyway .

The GT3071R is a factory hybrid , the $64 question is can you get sufficient exhaust gas speed through it for good boost response on a daily driver . The smallest ARR turbine housing is the HKS T28 flanged .61 and their next is the .73 which the SR20 brigade like on the HKS GT3037 52 trim . Garrett now do a .63 version in T3 flange but where to start ? If you use this turbo make sure you get the propper full sized GT30 turbine version as the "3071R Wastegated" version has the cropped turbine and GT28 exhaust housing resulting in woeful turbine efficiency - lag .

So for a mild upgrade a GT28RS or for more and higher rpm urge a GT3071R and fiddle with the small medium GT30 turbine housings . The only surefire way is to drive some modified cars and copy the result you like best .

Nite all ................

[Roy]

If you use this turbo make sure you get the propper full sized GT30 turbine version as the "3071R Wastegated" version has the cropped turbine and GT28 exhaust housing resulting in woeful turbine efficiency - lag .  

But reading all the hoo-haa, how do you ascertain the rake on the turbine. If the thing is bassically flat it will flow plenty but be laggy as hell. Is this where you fish around and look at effeciency islands of turbines?

The other thing that i cant get my head around, no matter how much i consider the flow of compressor wheels, the trim/diameters, combined with turbines and housing sizes....i cant understand how ppl can just say throw a smaller A/R exhaust housing on it if its too laggy.

The A/R doesnt tell you anything about the exducer size, turbine size etc, so how can you ssay just keep throwing smaller A/R housings at the thing???

[R31Nismoid]

it doesnt work like that troy i agree.

If you chuck on a smaller comp wheel, with the same exh wheel it will come on sooner as the front is spinning up faster than what it was before... incresing the rear wheels speed sooner

top end high boost output would be less but for the most part it would be fine

[discopotato03]

Hi Roy , all the turbine flow maps I've seen are a graph with graduations of corrected flow (in lbs/min) up the LHS and pressure ratio across the bottom .

Some turbo combinations , such as the GT3071R , are a bit more biased toward extra exhaust gas flow than others . If you consider that both the 3071R and the 2871R can use the same 56 trim GT35 compressor the effects of using a 54 vs a 60mm turbine can be considerable .

I had a look at the turbine map for the GT3071R and the GT28RS (same turbine map as the GT2871R) to see the differences . Using Garretts smallest .63ARR GT30 housing on the 3071R the graph is very similar to the larger .86ARR housing option for the GT28 turbine used in the GT28RS and GT2871R . So using a larger diametre turbine for the same gas flow capacity pays off in terms of turbine power . Doing it the other way with the larger ARR GT28 housing/turbine combination puts you at a maximum as there are no larger housings than .86 .

Area Radius Ratio has nothing to do with the exducer diametre of an exhaust housing . The exducer size is dictated by the turbines trim because the exducer side of the turbine varies but the major or inducer diametre stays the same . Turbine flow maps clearly show the flow of the housing rising with the ARR even though the exducer size stays the same . Its not possible to rate a housing or turbines flow by itys exducer for that reason . The GT turbines have much wider inducer tips and the housings wider nozzles and thats why they have much higher flow ratings size for size than T3/T31/TA34/T04 types that they replaced .

Cheers A .

[RS500]

maybe the first question to be asked is 'how much horsepower does quincy want/need'?

[quincy777]

maybe the first question to be asked is 'how much horsepower does quincy want/need'?

<{POST_SNAPBACK}>

Thanks for input everyone. I am chasing mid 200 rwkw. So have taken a punt with the 3071. Putting it on this weekend so will keep you updated.

cheers

[discopotato03]

Thanks for input everyone.  I am chasing mid 200 rwkw.  So have taken a punt with the 3071.  Putting it on this weekend so will keep you updated.

cheers

<{POST_SNAPBACK}>

Fair enough , the GT28RS would do that but be at the end of the compressors flow capacity . Let us know the part numbers on the plate riveted to the turbos bearing housing so it can be identified .

Cheers A .

[RS500]

Thanks for input everyone.  I am chasing mid 200 rwkw.  So have taken a punt with the 3071.  Putting it on this weekend so will keep you updated.

cheers

<{POST_SNAPBACK}>

quincy777,

i see you already made your decision and bought the GT3071 - which one did u go for, GT3071R (with 60mm turbine wheel) or GT3071 (with smaller 90 trim turbine wheel)?

good luck anyways, let us know how u go.

[Dale FZ1]

The exact turbo specs you chose would be appreciated/enlightening.

After viewing the Garrett catalogue, and then speaking with a Garrett distributor, it seems that there is a little confusion (for me at least) as to what is actually available.

The information I received then was that the GT3071R was externally gated (???) which is not consistent with the Garrett cat. I was advised that they could build an internally gated unit, giving the required T3 turbine inlet flange not available with the GT28 series housing.

I came away from the inquiry trying to establish whether the web-based Garrett cat. was more comprehensive than what he had in hard-copy, or whether there was a mix-up (me not fully understanding something), or a wind-up (him chasing more $$ on the basis of having to do a special build rather than sell a manufactured unit).

Also the Garrett cat. seems to indicate that the GT3071R options are basically two different A/R turbine housings. I note some comment about "turbine stage" compatibility with GT2554, and GT2560. Am I now to interpret this as being that they will fit smaller turbine wheels from those units also? Is it by this means that they can provide such a wide power rating ability for the GT3071R ?

Just looking to improve my understanding of these particular products and achieving a good match.

cheers

[quincy777]

These are the specs of the one I have. Looks great and is a heavy brute. I am just using adaptor flanges.

This unit has a T25 type base flange and GT25 type rear flange for the exhaust. Features huge GT30 Turbine wheel, and a 71mm 56 trim comp wheel, a .50 comp cover with smooth machined 4" bellmouth inlet and or a 2.750" inlet. This unit has a .86 exhaust housing in the 450hp form . The comp wheel actually flows 44 LBs/Min and itself is rated near 450hp.

[discopotato03]

I was bashing out a long reply and lost it to cyber space - DOH !

Take 2 .

The original Garrett GT3071R is shown in an earlier catalogue at -

Garrett_Catalogue%207%2017%2013.pdf .

I can't make it work in a search it's just on my desktop .

The turbo dosen't have an assembly number only a cartridge (CHRA)

number which is 700177-0023 . This is the real one with the 59.9mm UHP GT30 turbine . A contact in the US had an early one from ATP Turbo and its ID Tag had 755270-1 top line and 89004-27 underneath .

ATP and Garrett are also selling a GT3071R "Wastegated" version which HKS call their GT2835 series turbos . These use a ground down (cropped) UHP GT30 turbine at 56.6mm in 84 and 90 trim . The cartridge numbers are as follows :

1) 84 trim turbine CHRA No 700177-0003

Turbo assembly No's 700382-0003 , -0007 , -0019 . -0024 .

2) 90 trim turbine CHRA No 700177-0004

Turbo assembly No's 700382-0004 , -0020 , -0021

The turbo assembly numbers are different because of variations in housing style and ARR .

I was talking to a Garrett production engineer a couple of years ago and he believed that the cropped turbine and bored out T28 exhaust housing was a desperate because Garrett didn't have a GT turbine in between the T28 (NS111) and the GT30 UHP . The want to have a bit more exhaust flow and mounting convienence (integral gate T28 flange) ended up being an inefficient laggy dog . Have a look at the turbine maps in the current Turbobygarrett catalogue for the 3076R (real GT30 turbine) and compare with the two GT3071R's . Not too flash eh . Also that catalogue has nothing like the full GT30 based range , the count so far is 18 CHRA's and 33 complete units . Also have a look in Turbomaster-Catalogue-garrett-GT30 , and Turbomaster-Aplications-Racing turbochargers-Ball bearing turbos . This is not the whole picture but covers most so don't let the local dealers tell you "na mate no such thing" .

Cheers A .

[Dale FZ1]

Ah, this makes much more sense, and is something of a better explanantion of an earlier thread about the GT3071R and its variants. I will look at the suggested linked areas to become more conversant with the specs.

I did speak again with the dealer today, and he was only aware of the availability of an internally gated GT30 housing, but it is not a regular stock item.

Their stock catalogues were also at quite some variance with what is indicated as available on the TurbobyGarrett site, so making sense of what is actually available was difficult.

Addressing the possibility of a "build your own" hybrid, I also asked about selecting a mix-match combination of a GT2871R using a 52 trim compressor, and fitting a GT30 housing. This does give the possibility of a spec the same as the HKS GT-RS (400ps), which incidentally has the same turbine assembly as the Garrett Discopotato (320ps) but the bigger 71mm compressor to generate the power capabilities.

It ended up being a case of why try to recreate what is already available through a HKS dealer, and IF the GT30 housing can be machined to cater for the smaller wheel, costs aren't going to be favourable.

Apologies for moving the thread off-track.

cheers

[discopotato03]

Dale unfortunatly exhaust housings cant be machined smaller and this is why the problem exists . Neither Garrett or HKS offer an integral gate T3 flanged GT28 exhaust housing for the 76 trim NS111 turbine . Out of time .

Cheers A .