Garrett Gt3540r - Modified ?

[discopotato03]

Hi all , I've been looking at Garretts GT3540R for a while now with the idea of using one on an RB2631DET low mounted .

Peoples experience with these things seems to show that the 82mm GT40 compressor in 56 trim is often a bit over the top for realistic power goals so what to do ?

I don't like the idea of the GT3040R's , either 50T (HKS) or 56T (Garrett) though the 50T is the better of the two . I believe the GT30 turbine is a little small for a 3L anyway so it wouldn't matter what compressor you hung off it , a reasonable alternative may have been the GT32 turbine but Garrett don't offer it in any ball bearing cartridge I know of . I think HKS had Garrett crop their GT35 68mm turbine down to ~ 64mm 84 trim for the GT3240 - so had a "sort of" BB GT32 turbine . That turbo had a 54 trim GT40 comp but more on that later . Essentially the GT3240 is a bit like a GT3540R with an in between sized turbine (between GT30 and GT35) and a slightly smaller trim compressor of the same family . It seems to have been an effort to have more wind than their GT3040 and a bit more exhaust flow for a bit more squirt . They are being used in single form on high performance fours such as Evo Lancers the odd Toyota 3SGTE and in twin form on Nissan RB26 drag specials .

Back to my situation . I think when HKS were having their GT BB turbos developed there was less in the way of wheels around than there is today and anyhow it was 90's thinking .

More very soon , cheers A .

[discopotato03]

In more recent times some turbos have been optioned with turbines closer to the compressors major diameter or if thats not possible smaller trim compressors . I think this is done to minimise exhaust restriction and concentrate on moving lots of air but not at high boost pressures .

There are lots of examples of HKS optioned GT BB turbos with mid trim compressors while Garrets nearest equals have the big trim comp . Many say HKS turbos are optimised to work at higher boost than their Garrett cousins but I reckon they are simply optimised to be a good balance when loaded up rather than a hell fired attempt to find a couple of pounds of boost at cranking revs .

So from some of their examples we can learn that lag and response can be moved around in a couple of different ways . The old standby if a turbo was a bit lazy was to throw on a smaller a/r turbine housing to wake it up earlier . I think the better way to do it is to reduce the compressor trim which takes some load off the turbine and for same exhaust energy input can spin up earlier in the scheme of things . This is all fine and well as long as the smaller trim compressor still has the pumping capacity required .

To the GT3540R , finally they say ...

These turbos use the 82mm GT40 compressor of the BCCW18C family in 56 trim . From some sniffing around I found 50 , 52 and 54 trim wheels of the same family as well . The HKS GT3040 uses a GT40 50 trim as does the bush bearing GT4082 . The bush bearing GT3782 uses a 52 trim and finally HKS's GT3240 uses a 54 trim version . Interestingly the HKS's use a .60 a/r TO4S comp cover except for the GT3040 optioned with the largest 1.12 a/r turbine housing (thanks Fantasy) while Garrett plugs on with the larger .70 a/r TO4S cover .

What I have in mind is to use a 50 or 52 trim GT40 compressor on a GT3540R to optimise whats probably a Diesel cartridge for a petrol engine . I don't need 650Hp's worth of airflow when 500's worth will do nicely . Now Brett from GCG tells me that the 52T wheel is available though from over seas and would require machining operations so it could fit . The comp cover is also around but as a new component is a tidy sum . So it seems that the only "easy" way out is to somehow obtain a "cheap" or damaged HKS GT3040 and rat it for the compressor and comp cover . Even then the wheels centre hole would need to be drilled as the GT30 turbine shaft is smaller than the GT35's . If anyone has one of these for reasonable money can you let me know - remember its just the wheel and housing I need .

It it eventuates it could be called the GT35RS . How much better it would work than a std GT35R is hard to say but I'm sure it would suit my purposes and close the gap between GT30R and GT35R enough while having no less exhaust restriction .

Opinions ? Cheers A .

[Bl4cK32]

ive been following this for a while too. GT30r too small and the gt35r is too big for what i want.

I have seen the gt32's and wondered if bush bearing would make that much difference to a ball bearing turbo. Roy says his td-06 spools faster than smaller turbos, so it makes me wonder...

I always like reading your opinions disco, let us know how the gt35rs goes

Edited February 15, 2006 by Bl4cK32

[R31Nismoid]

What power are you wanting out of is Disco exactly?

[discopotato03]

Its hard to put a number to it so if I had to guess probably around 450 , more interested in average power . The car will almost certainly be 2WD and have to live with production gearbox ratios , also don't know what I'm doing with rods yet so maybe SK's 475Hp may be the ceiling . Its doubtful if a road driven R32 with street rubber on sane rims could harness even this . So a free reving torquey engine with good throttle control is the aim . I want to use a reasonably tall ie 3.7 final drive with 16" wheels and tune the thing to make best mean part throttle torque because I think that feels good and pays off at the bowser .

I don't think making good power with this kind of engine will be difficult but getting a smooth transition from cubic inch power to forced induced power may be interesting .

Cheers A .

Edited February 19, 2006 by discopotato03

[R31Nismoid]

with a 26/30 it'll make up for the gap by using the GT35 IMO.

GT35 works well on the 2.6 as it is...

Plus if you use cams...

very meaty power range indeed i would imagine, and it shouldnt be too "twitchy" really when you think about it if your not going the tiny rear housings, should be very progressive

[Roy]

ive been following this for a while too.   Roy says his td-06 spools faster than smaller turbos, so it makes me wonder...

<{POST_SNAPBACK}>

Mine doesnt spool quicker then smaller turbos. Thats for sure. But the way the thing drives when comapred to similar sized ball bearing turbos, then well the combination of the manifold and everything else suggests that there is more in the wheel sizing then the fact that its plain bearing or ball bearing.

I have compared it to a few 2535s etc on Rb20s, and from memory it spools about the same /better. I understand the 2535 is rated less the TD06 and is BB...so ?????????????????

The bearing type probably plays a part in the power delivery. Where a BB turbo has better transient response, so mine is a bit duller when i open the gates...which is ok by me as it seems to help traction.

Ppl always say Trust turbos hit hard, mine doesnt really seem to. It doesnt really ramp hard onto boost and terrorise passengers, i actually like how it gets its power down. Perhaps thats the cam gear settings,...lol i got no idea

LOL...im confused, yeh BB turbos. No doubt are better, but the wheel sizing and matchin it to exhaust flow would seem more important...how thats done i got no idea

...but with all the cool BB turbos floating around at a steal...id only consider a plain bearing turbo if all avenues hit a dead end...though i did see an animal Hybrid turbo once gettign tuned on a friends car. It used the Trust TD06SH turbine, with a big Garrett front wheel, still using the Mitsubishi cartridge...the thing was very impressive and was marching easily past 300rwks on an RB25. It was very surprising how responsive it was and it was with something like 18psi at less then 4,000rpm...it was near maxing out the 550 injectors so was making good power...so perhaps look at the TD06SH turbines...???

[Bl4cK32]

thanks remebered you said something like that. I spose the 3lt wont have any problems with the power coming on a little less if it had a plain bearing....

Im keen to hear how disco's version goes;)

[s13rb26]

Can you mix and match Garrett and Mitsu wheels from the trust range?

Do you know if the trust wheel trims are differnt/ or you can actually buy garrett "similar" trust spec'd wheels?

[Roy]

I have no idea whats involved...but the Yanks with their FWD Mitsus etc have been funky things with Mitsubishis turbos with Garret wheels for years

[Cubes]

I want to use a reasonably tall ie 3.7 final drive with 16" wheels and tune the thing to make best mean part throttle torque because I think that feels good and pays off at the bowser .

I don't think making good power with this kind of engine will be difficult but getting a smooth transition from cubic inch power to forced induced power may be interesting .

Cheers  A .

<{POST_SNAPBACK}>

I recently drove a friends VLT that made 187rwkw running a 2.5" exhaust, fmic and 14psi, it had a compression test resulting in @ 150psi in all 6. A little high for 7.8:1 comp I thought.

It was rather impressive to drive. To be honest I didn't notice any lack of down low torque despite the high 3.45:1 ratio at part throttle, it did feel a little slower getting up in the rev's where boost would build but once boost was in it really hauled arse.

To cut a long story short don't for one minute be worried about the 3.7:1.

It will work fine and be a much nicer easier car to drive.

Darren... I shiet you not it felt as if it pulled as hard if not a little harder than yours through the mid range, it did however feel as if it died a little past 4.5k, due to the head I assume.

The longer ratio felt as if it allowed you to use the torque of the motor.

Much much nicer and quicker feeling to drive than the 4.363:1 ratio.

For a streeter Sky30 expressed his concern with regards to how savage the gt35r is on the rb30det. Do remember its making ~550nm of tractive effort torque in order to make ~300rwkw where as an rb25 on the same dyno requires around 390nm of torque to make ~313rwkw.

Mine made 390nm of torque to make 180rwkw. :S

We can see why traction is such a problem on a rb30det making decent power.

Interesting torque figures, get the transition as linear as possible and it will be a very quick car.

Back on topic... discopotato03 do you mind being my guineapig.. lol

No thats not a question.

Your goals are the same as I and you do understand turbo matching just a little (lot) better than I.

[S3_Girl]

I just went back from 4.11 to VL turbo 3.45's and really noticed no difference in

normal driving, But obviously was a lot nicer on the freeway. Actually feels a lot

faster

on boost aswell, i think bigger capacity turbo motors like gearing, IMHO,

4.11 and 4,44 are to short for a RB30 motor, they don't rev hard enough .

If you are using a twin cam Rb30 the 3540 .82 is quite linear in it's delivery

with poncams, compared to the single cam motor, i would just use that.

cheers

darren

[Cubes]

As Nathan said when he drove mine with its 4.363:1.

It feels as if it doesn't get time to 'use' the torque from the motor to accelerate the car.

Darren, how do you now find throttle control/traction?

[discopotato03]

Yeah Cubes LOL I was sort of wondering if I should get someone to host the "GT35RS" if it was a practical proposition . Seriously though the car should come before the turbo otherwise the economics of the project get all out of hand .

I'm pleased it was noted that the VLT's gearing works out ok and think its a combination of the box and final drive ratios that suit the RB30 and I spose the approximate weight of a VL or R32GTST . When I crunched the numbers the all up gearing of the VLT looks better than the 33 box and taller diff . Its most likely a case of Nissan wanting that short 1st ratio so an R32/RB20DET combination or R33/RB25DET could idle around in Japans bumper to bumper without being snatchy or needing to ride the clutch . I'm probably starting a war here but either of the above would not be the most torquey things given what they have to haul around at low revs in std tune .

The RB30 with its longer stroke and rods I'd say makes better use of its capacity than the 20 or 25 so its capable of significantly more torque at lowish revs . The difference between 1st - 2nd is better (closer) in the VL so this makes a big difference in how a car launches from start . One of the most infuriating things I find with Nissan transmissions is the big 1-2 gap , kills baulk rings and makes motors bog down . The VL has the wider gap 2 - 3 where it is better off because winding up 2nd is more likely to get most where they want to be and anyhow the 2-3 change across the gates takes a little longer and gives the syncro hub a short spell before it takes up . Also 3 litres would be less fussed pulling the taller 3rd gear . I should really try and locate a VL box before they dry up though I suspect the Navara V6 version of this box may have the same ratios - may even have the Skyline style shift and clutch slave mounting point too .

Anyhow the combination of appropriate gearing and engine torque characteristics makes or breaks these conversions , I dont need upper end turbo torque because mid range pull makes the arguably tall gearing work - well on the road anyway .

Latest thinking for "GT35RS" is maybe reprofiling the 56 trim GT40 compressor for 54 or 52 trim . Doing it this way means its (maybe) possible to use the original wheel which you have and its guaranteed to bolt back on . If this mod gained a following it would be nice to keep costs minimal on an already expensive bit of gear . Not sure what to do about the comp cover as there are a few options . We could use a TO4E cover like Ford did with the XR6T in .50/.60/.70 a/r or machine/press/stake a new section of aluminium into the original .70 a/r TO4S cover and profile it to suit . Thinking about it this gives the opportunity to play with port shrouding like HKS tends to do at times and could bolt in like their version of the TO4Z . The .60 a/r TO4S cover like HKS used on their GT3040/GT3240 is available os but in the mid 400's .

Av a good weekend cheers A .

Cheers A .

[S3_Girl]

As Nathan said when he drove mine with its 4.363:1.

It feels as if it doesn't get time to 'use' the torque from the motor to accelerate the car.

Darren, how do you now find throttle control/traction?

<{POST_SNAPBACK}>

That's exactly what i was going to write but didn't know if it would read write,

At 100km i only went back to second and bang into stop to stop wheelspin,

but it felt like it stopped pulling hard at 160km

I had exactly the same problem with our 1.5L turbo rolla years ago with 4.44, then

went to 3.9 and it was a weapon, the problem there also was worse, revs would rise faster than boost in 1st gear as it woudn't load the motor up enough, It feels exactly

the same with the RB30 even though i can see it has fullboost at 4250rpm in first.

I guess with 4.11's it fells revvy, but with 3.45 it pulls/feels torquey wheel spin is tamed down a fair bit, still spins all the way through second on low boost

but you can also feather the throttle which you coudn't do with the 4.11's, the whole car

felt like you were pushing/pulling it, highly annoying.

If i had a R32 i would putting the tallest ratio i could get with a RB30 in it.

Changes the car, defibitly for the better

So bang a 3540 .82 on it and gets some diff gears:)

Oh yeah totally agree with disco on the torque of the Rb25/20, i might

upset people aswell, but i can not stand them, they both feel like 4cyl to me

compared to the 30, and a big turbo makes them worse, and i have driven plenty

stock and with big turbos

cheers

darren

Edited February 19, 2006 by S3_Girl

[discopotato03]

Been thinking about compressors and housings again for the mythical perfect GT35R turbine based turbo for an RB26/31DET . After much research into small ie 50 trim GT40 compressors it turns out that the larger trim ie 56T GT37 76mm wheel from the real GT30R and 3037 56T has similar pumping capacity in a more compact TO4E type compressor cover . I need to go back and compare the maps specifically the speed lines of the maps to see if they're similar enough to work at same-ish shaft speeds . If so I then need to ask Brett if a GT35R turbine can fit up the guts of A GT30R turbo with its heat shield so that the cartridge seals in the front of the turbine housing . If it worked it technically makes it a GT3537R or GT3576R . I also need to find out if the 50mm outlet is large enough to feed a 3L up to 300Kw and if not are their .60 or .70 a/r versions with the larger 60mm outlet . Does anyone know if the XR6's turbo will go 300Kw + because this would answer some of these questions . I really would like to see its comp map but being a local development probably unlikely .

Cheers A .

[DoughBoy]

Check out the XR6 forums, iirc the highest from a "stock" XR6 GT35R w/ported wastegate orifice is around the 400rwkw mark.

[discopotato03]

Thanks Chris , its good to know the integral gate and housing can pass the exhaust gas at 400Kw on an angry 4L 6 , the torque must be pretty good .

Latest information is that the GT35R's turbine shaft will fit in the GT30R cartridge , apparently the GT25 through to GT35 BB turbos all use the GT25 BB centre section/bearing cartridge/shaft BUT the journal where the compressor mounts is different/larger on the GT35R turbine shaft . So this means it can work but the GT30R's compressor bore needs to be enlarged to suit the shaft .

Cheers A .

[R31Nismoid]

Thanks Chris , its good to know the integral gate and housing can pass the exhaust gas at 400Kw on an angry 4L 6 , the torque must be pretty good

But how much is it passing is the question.

Most of it would be going down the dump you'd think to get the boost required to get to 400rwkw

[BezerkR32]

Hi all , I've been looking at Garretts GT3540R for a while now with the idea of using one on an RB2631DET low mounted .

Peoples experience with these things seems to show that the 82mm GT40 compressor in 56 trim is often a bit over the top for realistic power goals so what to do ?

I don't like the idea of the GT3040R's , either 50T (HKS) or 56T (Garrett) though the 50T is the better of the two . I believe the GT30 turbine is a little small for a 3L anyway so it wouldn't matter what compressor you hung off it , a reasonable alternative may have been the GT32 turbine but Garrett don't offer it in any ball bearing cartridge I know of . I think HKS had Garrett crop their GT35 68mm turbine down to ~ 64mm 84 trim for the GT3240 - so had a "sort of" BB GT32 turbine . That turbo had a 54 trim GT40 comp but more on that later . Essentially the GT3240 is a bit like a GT3540R with an in between sized turbine (between GT30 and GT35) and a slightly smaller trim compressor of the same family . It seems to have been an effort to have more wind than their GT3040 and a bit more exhaust flow for a bit more squirt . They are being used in single form on high performance fours such as Evo Lancers the odd Toyota 3SGTE and in twin form on Nissan RB26 drag specials .

Back to my situation . I think when HKS were having their GT BB turbos developed there was less in the way of wheels around than there is today and anyhow it was 90's thinking .

More very soon , cheers A .

We run Gt 30/40 on a couple of customer cars, very streetable and make 285kw at the tyres. would be ample. If you are looking for something a little different you could go a GT35/66R-SPL. Its got a

0.8ar front cover, 66mm comp wheel and the choice of .63, .82 & 1.06 exhaust housings. This is a single upgrade for RB26. Im installing this setup in a GTR next week, let you no how it goes.