Hks Gt-rs - Rb25det

[Al]

So who did it then?

No idea, as i bought it second hand.

There were only a very few w/shops that offered rb25 hi-flows to this rating and GCG was one. I am not saying that mine was done by GCG, as i really have no idea. Just that GCG have dropped this combo as they were having the same occational surge problem, with this setup.

PS: ATP never offered this combo, as Kyp was aware of the possibility of surge problem occuring.

PS: You can not compare the $'s HKS put into their turbos, to the $'s any Australian turbo "manufacturer" puts into hi-flowing a std turbo.

[Al]

So ya wanna fight?!!!! hehe.

You certainly do have some serious lag there and I'm wondering whether you have cams or not. Your engine or associated hardware may have a restriction on the inlet side causing the compressor surge. Perhaps some cams or adjustment of the cam gears would bring the boost on earlier if you can get some more overlap.

By way of comparison here is my dyno sheet from the SAU Dyno Day last saturday.

I can get 1 bar by 3200. Also my car hasn't been tuned for this setup. My AFR's a very rich and all over the shop so more power to be had without requiring more boost.

BTW Disco - Did you realise you were agreeing with me there? :confused:

No fight, just my experience/opinion

Just answering your questions, in the hope that you may have an idea to improve my response.

- cams: Tomei Poncams (R33 S1) D=256, L=8.5

- Head has been "race ported" and reco'ed

- Adjustable Ex. gear set to "0", as i think Tomei designed the gears for the factor setting

PS: Your response is exactly what i want!! 14psi by 3200rpm would be great.........

What combo are you running?

[discopotato03]

sarahB the problem is that the turbine is a bit small in diametre - blades/vanes are not long enough radiating out of the turbines hub to generate sufficient leverage or shaft torque to power the 71.1mm compressor esp in its mid and large trim .

[paulr33]

hi disco,

it was me that posted that, i was logged in incorrectly as my gf.

out of the gt28rs,gt2860,gt2871 range is there an equivalent that doesnt suffer this problem. ie: has the correctly sized turbine to match its housing and compressor wheel. im still learning to read compressor maps and turbine maps but would like your thoughts?

[discopotato03]

All things considered the GT2835 Pro S would probably come the closest off the shelf . This is not a cheap option but you can at least ask others on this site who've got them what they think . Actually do a search , lots of old threads on the HKS GT2835 Pro S .

It is possible to change turbines from GT28 to GT30 because the shafts have the same dimensions . I would do it this way because I prefer the full sized GT30 turbine to the cropped one in the 2835 series .

BUT I would use the smallest trim 71mm compressor that gave me the airflow I needed . I should add that modifying a Garrett cartridge would be a cheaper basis than a HKS !

I was told recently that its difficult to get much more than 300Kw (400Hp) to the ground with reasonable street rubber (2WD) . If you work on ~ 10-11Hp per pound of airflow the 48T 71mm GT35 comp is good for 390-430 Hp .

So either GT30 turbine into 2871R ( 48 or 52T) or 56T down to 48 / 52T comp in the real GT3071R . One way will be cheaper than the other but both give the same end combination . I really hope Garrett is doing their new T3 flanged integral gate exhaust housings in .63 as well as .82 a/r as it would make a responsive unit . The 2835 Pro S uses the slightly cropped GT30 turbine (56.6 vs 59.9mm) in a .67 a/r housing . I reckon the 59.9 in a .63 housing would be pretty passable particularly with the smaller 48T compressor .

Talk to Brett if your serious , nite all ...

[Iceduck312]

It'd be interesting to compare the actual weights of the 48T, 52T and 56T 71mm compressors.

Edit. Nuts Iceduck312 forgot to log outta my PC (busky2k)

Edited March 14, 2006 by Iceduck312

[180bfj20det]

Tell me, what is the "real life " advantage of using lets say the hks 2835 turbine instead of the 53mm turbine from the GTRS if we use the 71 compressor? Are we talking less lag or just more top end? Cause Id rather have less lag, less top end power and the 250rwkw the gtrs can deliver in the small 0.64 housing than using the 2835. Explain this.

Also, you say you dont beleive it (53mmp turbine) could drive the 71mm properly...hey, Im on the ball park with you, remember the thread I posted about the 15 percent rule where the 2871r is turns out the be the worst....but beliefs and reality are different. Like I said, NS.com houses many a dyno curve from CAs and SRs getting full boost at 4krpm and making 250rwkw on 15-20psi. Now theory/on paper is one thing, but reality maybe different and clearly here the 2871r is a success regardless of the "inefficient turbine".

Fact is, this turbo is very good and I dont believe its "just" a substitute for the 2540.

In the end, Id really like to know whats best and "off the shelf" available as hybrids...as someone has said, no-one in australia nor in any other country spends the money on R and D like HKS do. Garrett obviously spend loads too and have decided to bring out the 52 trim GT2871r. Dyno results prove its a good thing.

Its all very confusing.

This topic is about the GT-RS and my opinion is for it , have less time for the 56T version .

What I said about the 48T version I stand behind for these reasons .

Everyone at the time (me included) wanted to know what was the next small step up from the GT28RS (GT2860RS) in Garretts GTBB range . The GT28RS is good for ~ 35-36lbs compressor flow and the 48T GT2871R is good for ~ 39 . From memory the 52 and 56T versions do about 44lbs - the energy required to power a 44lb capacity air pump is significantly greater than a 39 or 35 lb one . ALL of these turbos use THE same 53.85mm 76T turbine . Because the GT28RS's compressor is a very good match for this turbine it works very well - in a .86 a/r turbine housing - on a 2L four .

I would not take this turbine past the 48T GT35 71mm compressor because I don't believe it can drive it properly read efficiently . The GT2835R starts to look much better than the 2871R because it has more turbine to drive the 71mm or GT35 compressors with . The modified turbine in the GT2835R is larger at ~ 56.6mm in 84 or 90 trim and developes more shaft torque for the same exhaust gas energy .

The GT-RS was the answer to the ultra lag HKS GT2540R , that doesn't make it perfect just less of a compromise . You people really should be testing the turbine inlet pressure and comparing it to boost pressure downstream of the throttle/s . You also should go to the maps for compressors AND turbines to get an idea how efficient the turbines are or are not . A turbine with an appropriate compressor is always going to be more efficient than the same turbine with a bad ie huge comp hanging off its shaft . Don't believe me ? Go back to turbobygarrett and have a look at the turbine map for the GT2860RS . Now flick over to the turbine map for the 52T GT2871R . This is the exact same turbine but its efficiency is pathetic don't you think ? The reason for this is 1) the diametre mismatch 2) its lack of gas flow capacity particularly in a .64 a/r turbine housing .

It is critical when specing turbochargers to compare the turbine/housing combinations corrected flow capacity and compare it to the compressor/housing's choke flow capacity . Now somewhere in the 55- 65% region of turbine to compressor flow seems to be ok , its a hell of a juggle with wheel trims and housing's a/r's but that's as broad a generalisation as I can work out . The best compromises seem to be 60%+ but you start to trade boost threshold for efficiency under full load full boost .

If I was going to work with FJ20's again (not) I would use a GT30 turbine or better still the 60mm NS111 turbine from Champ Car type turbos . In a perfect world my GT30 turbine would be 76 or 78 trim not the Diesel 84 trim and the compressor a GT35 71mm 48 or 52 trim . With a bit of stuffing around it would have more grunt than mine did with the GT28RS and no more chance of choking on its exhaust and melting down .

Custom GT BB turbos can be had if you know where to look but they are expensive and the success of them depends on your understanding of what makes a good one tick .

Out of time cheers A .

[discopotato03]

I reckon Garrett will sell it because there is sufficient market to make it worth their while .

The modified 56.6mm GT30 turbine is manufactured by Garrett and found in some of the turbos they sell too .

GT-RS vs GT2540 , try buying a 2540 that isn't old stock . Read the comparison article (Zoom or HPI) .

Development costs don't have to be high for a product to work well , just need to be close or right the first time .

Now you want 250Kw for your FJ20ET . 250Kw = 333.33Hp , working off 11Hp per pount of air = 30.303lbs . I add 10% so as not to fall off the RHS of the compressor map so 33.3333lbs air . Working off my theoretical 55-65% of compressor end flow to get turbine end corrected flow , I'll use 65% this time = 21.66lbs .

Now to the maps . As I think I said to you before I thought the GT28RS (GT2860RS) would be very close . I'll show you the maps and you can see for yourself , by the way I am not playing games by working the numbers backwards either .

Now from memory you've said in the real world you don't reckon its enough . I have said to you here and elswhere that the GT2871R 48T is the next small step up - compressor flow only not turbine flow , actually turbine flow drops because of the reduction in a/r housing from .86 to .64 as you can see on the turbine maps . If you know how to make more air in for more restriction on the way out make better torque and turbine response for equal thermal load you are a rich man . I have also thrown in the turbine maps from Garretts GT3071R "waste gated" turbos because they use the cropped GT30 turbine . Pay no attention to the efficiency number because these use the bored out and butchered GT28 turbine housings . They are a GT30 based turbine that needs a GT30 based turbine housing like what HKS has made . Also those 3071R WG's use again the larger 56T 71mm GT35 compressor wheel .

I've not mentioned this here before but its important to realise that the jump from GT28 to GT30 turbine involves a jump to a very different style of turbine . The GT28 (NS111) is a 9 blade 76 trim where the GT30 is a 10 blade 84 trim UHP (Ultra High Pressure ratio) . The blade forms are different , the GT28 is a higher exhaust temp petrol engine turbine while the GT30UHP was designed with cooler exhaust temp Diesels that work over narrower rev ranges hence the large trim . This is why at times people make the GT28 to GT30 jump and find the thing laggy . HKS knew that ages ago and opted for smaller trim compressors to get around it . What Garrett could have done is make a 76 or 78 trim version but then its not so good for Diesels which are the bulk of their sales . The cropped GT30 turbine has no GT30 based housing from Garrett , is still in 84 or 90 trim . HKS had to get their own housings made which cost a lot more that buying an off the shelf item if it existed which it doesn't .

So 180BFJ you are going to have to fit something to get a result and from that work out which way to go from there . Could be wrong here but seem to remember you saying you had one of the GT30 based TO4S turbos . These are hopeless because the arguably very free flowing GT30 diesel turbine does not have the trapping efficiency at the low revs that the dinosaur TO4S compressor starts to pump and load the turbine at .

What you do is up to you , asking 20 different people will probably get you 20 different answers so you take one of their opinions or form your own otherwise you will ponder for ever .

Cheers A .

GT2871R_Turbine_Map_..bmp

84_Trim_56.6_mm_turbine_1_..bmp

HKS_GT2835_84_T_2_..bmp

Edited March 15, 2006 by discopotato03

[Al]

Hey Abo Bob,

Thanks for your e-mail, i appreciate your input.

Just one question:

Between 2k-5krpm how much timing are you running?

You also mentioned an issue with porting, but the example you used related to an rb26. I personally would not touch the head of a 26, as they were engineered for race purposes, apart from port/manifold matching as stated. The rb25 on the other hand is totally different and i still believe gains are had from porting, provided it is done by a profesional porter.

I run stock R33 S1, rb25det, compession. (i think it is 8.5:1 or 9:1??????)

[justin911]

ive ended up buying a gtrs

i shall hopefully hold it in my pretty little hands in 10 days

thanks for everyones input on the issue most of it was over my head hehe but still good

[Al]

ive ended up buying a gtrs

i shall hopefully hold it in my pretty little hands in 10 days

thanks for everyones input on the issue most of it was over my head hehe but still good

I want details!

From where?

How much?

etc..

Did you buy the kit, or just the turbo?

[paulr33]

also what a/r version

[justin911]

yeah its the kit with all the bits and pieces..

i got it off this trader guy on ns.com.. got my pfc off him so i trust him

cost $2700 delivered $22 less than nengun..... alltho i swear last night was only $8 differance..

dunno about the a/r / technical details.. i just got the rb25det version

[paulr33]

the 0.84/ar would have been nice to see how it performed.

what injectors are you going to use?

[Al]

That's a good price, i got quoted $2780 from a Melbourne dealer.

[paulr33]

the gt2871 can be had for around 1800 trade from garrett

[justin911]

i got me some nismo 550 ones as well.. just need to find a z32 afm now.. but ill buy one localy here.. support the economy and all that

[justin911]

yes, yes it can

the gt2871 can be had for around 1800 trade from garrett

[Al]

the gt2871 can be had for around 1800 trade from garrett

When did you get that quote? I have just been informed that Garrett have raised their prices. Can you please confirm the price.

[paulr33]

now all u gotta sort out is traction