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Gtx45R Rear Housing Choice On Rb32

Tyranus

By Tyranus,
in Engines & Forced Induction

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Tyranus Proficient

Tyranus

Posted
Posted

Ive tried using searching before anyone starts crying at me, but couldnt find a definitive answer.

My heads are heavily ported and its filled with Ferrea stuff and Supertech bronze valve guides. Im running Kelford 288 11.35 cams.

I have set my heart on getting a GTX45R i just need some information from people who have driven a RB30 or RB32 powered GT-R with this turbo. Im trying to decide inbetween the 1.01 and 1.02 rear housing. Yes iam after 1000hp atw but i do not want my power band to start at 7000rpm. How would drivability be at with the 1.02 rear housing? How laggy? My car is going to be street driven (mainly on the weekends). I know of someone who gets fullboost at 4400rpm with a GTX42R (RB32) how much further off would the 45 be from that?

Your input will be appreciated cheers.

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GTRPSI Mentor

GTRPSI

Posted
Posted

I think (not 100% sure) your cams are 288 degrees and 10.6 or 10.8 lift cant remember. (the cam spec sheet is with your head at barrys)

The issue your going to have is a big enough rear housing to flow where you want to but small enough to come on early.

Our precision 7175 has the .96 housing.... http://www.precisionturbo.net/Street-and-Race/ss/800-1-000HP/details/Street-and-Race-Turbocharger---PT7175-CEA%C2%AE/273

Why dont you go with the same turbo in GT42 Style, many good/better RB results with them..... http://www.precisionturbo.net/Street-and-Race/ss/800-1-000HP/details/Street-and-Race-Turbocharger---PT7175-GT42-Style/274

GT45 will be a lag monster man.....

Tyranus Proficient

Tyranus

Posted
  • Author
Posted

Let me rephase the original question.

Engine is a 26/32 nitto, fuel will be E85, heads are heavily ported, cams are 288 degrees, hypertune V2 single throttle body, 6 boost exhaust manifold.

My goal is 750Kw at the wheels.

Which turbo would be the quickest to come on boost, or area under the curve taking into consideration the cams, engine capacity and fuel etc.

bigmikespec Veteran

bigmikespec

Posted
Posted

Im trying to crack 1000hp @ the wheels

Ok, so over 1100hp at the engine, well if that is the case then the GTX4508R will do it.

The GTX4202R might do it, to be honest, if it was me I would go the GTX4202R and push as much as you can out of it. Go the biggest turbine housing, keep upping the boost until the compressor makes no more power; on the limit it will flow110lbs/min which is roughly 1100hp.

Tyranus Proficient

Tyranus

Posted
  • Author
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Ok, so over 1100hp at the engine, well if that is the case then the GTX4508R will do it.

The GTX4202R might do it, to be honest, if it was me I would go the GTX4202R and push as much as you can out of it. Go the biggest turbine housing, keep upping the boost until the compressor makes no more power; on the limit it will flow110lbs/min which is roughly 1100hp.

Sounds like a good idea.. But wouldnt a gtx42 with its biggest housing be almost or as much laggy as a gtx45 with its smallest rear (1.01) ?

bigmikespec Veteran

bigmikespec

Posted
Posted

The wheels on the GT45 are both bigger so more inertia required to move them. Again, I would go a smaller set of wheels and larger housing, I think the smaller wheels will offset the larger housing in terms of boost threshold.

bigmikespec Veteran

bigmikespec

Posted
Posted

What do you think of the 7175 GT42 style with 1.12 a/r

??? What does the compressor flow? And at what pressure ratio? Unanswerable questions as Precision don't publish compressor maps.

GTRPSI Mentor

GTRPSI

Posted
Posted (edited)

The precision range are well known to be under rated in terms of stated power, many builders have gone over stated rating easily, add e85 to the equation and its do able IMHO.

Have a look at the size of this custom made JPC turbo, its tiny, and on a single cam 2 valve head......

Remember you want to be quick streetable, that means coming on early and lineraly (ish).

Otherwise the other end of the scale is GTX47. :D

Take close note of the work throughout the car to support this thing, dont expect it to last forever.....

I think that asking for 750Kw at the wheels without a billet mains (as we discussed) will be a very short lived motor and slow on the actual street, purely drag strip 1/4 mile only and a pig to drive around.

750kW is pointless on the street, you cannot/will not lay the power down what so ever, while your fighting traction, the other guys gone.

Just my 2 cents.....the dyno number will sound good though. :)

Edited by GTRPSI
Mick_o Grand Master

Mick_o

Posted
Posted

Why not wait for the new PTE 6870? Spools like a 6766 but makes 7175 power?

Check out the Precision turbo thread. Results were on a 2J so should give you a pretty good idea of spool and power on your motor being similarly sized. (Yes i know alot of other variables involved for a direct comparison)

Can't agree more with Pete though This will be a nugget on the street ;)

Whats the intended use of the car mate?

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GTRPSI Mentor

GTRPSI

Posted
Posted (edited)

Whats the intended use of the car mate?

750Kw street......(join the dots). ;)

As ive tried to tell Sedat when he came over, a GTR with a 6766 will be quicker on the street A to B, a 7175 like ours will come alive and be quicker again after 80-100Kmh onwards, what he wants wont come on song till everyones pulled into McDonnalds, ordered and started planning the next run.

To win a run he would need to reach what is down right suicidal street speeds, the others with smaller turbos would be ahead of him the whole way as he fights traction and plays catch up, by the time he gets there they are on the brake pedal slowing.

Remember most runs are only to 120-140 max? Maybe the old 160-180 serious run? Street surface, not a dedicated drag strip? Street Drag radials?

Sedat, you need the smallest turbo to reach where you want to go, you need it to come on early (3.2 will help) and you need linear power delivery, nothing, nothing bang is only good at the drag strip with Nos to bring the turbo up on launch, its a diffrent game to the street.

Its not about the total power figure, its the way its delivered......

However running at GTR Challenge or SM1000 is again another thing to rolling starts at bypass.

Maybe if you want to run those 2 events, take the word street out of your turbo choise.......then go big turbo, big power and learn to live with it, even at those 2 events traction is a issue, ask Barry and James about the start line at SM1000, listen to the launches, its like gravel there on the start line, ive heard the GTR challenge is not much better.

Edited by GTRPSI
KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

Most of the big power (1000kw) engines that Rips build are for drags - often with 2 speed drag auto and are useless for street or track. The engines he builds for road cars and track cars generally get by with half that much power.

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