Rb25 + Gt3076r

[R31Nismoid]

The 52trim in the GT30307 & GT3037S are both different yes, but they are using different turbine housings as well?

Either that or I think I'm missing where the port vs non-port is listed on that link?

[juggernaut1]

Without checking I'm pretty sure they use the same turbine housings - just check that previous link.

I believe the 70mm comp inlet of the 3037 is not port shrouded..... and I definately know the the 100mm comp inlet of the 3037S is port shrouded as I have this compressor ready to go on.

Edited February 18, 2010 by juggernaut1

[GTScotT]

while i agree with you on the comparability of the maps due to AR differences Juggernaut1, the point you have mentioned has pushed the 52T further in favor.

thinking logically, the bigger housing will broaden both ends of the map, making the centre islands larger also. its a simplistic theory, the larger housing being harder to fill will obviously surge less, just as top end will also increase as flow capabilities do. being no rocket scientist it would be hard for me to back this up, but id also be quick to assume the larger housing would also see higher shaft speeds at the same exhaust gas flow (this is ONLY a personal theory).

Ash, id say the hardest compressor maps to get are for OEM turbos. considering where we usually see turbos fall off the map with our 'rough maths' i think you would be hard pressed to find an OEM turbo staying within the top 60% by redline, let alone once were boosting and often revving them harder than the manufacturer planned. id say the key to the difference between the map and actual results is in the tuning. while the turbos trying hardest in the middle of the map, shaft speed acceleration slows as you reach redline rather than being exponential which would see charge temps plateau rather than rise stupendously, coupled with EGTs topping out at a certain point due to timing and fueling changes in the tune, i think that side of the map is more than managable. one thing to take note is in the factory evo ecu's, the top end of the tune see's target AFRs hit 9:1 and timing slamming rock bottom of 1s 2s and zeros, compare that to where you get the maximum ZING from the turbo and you can see why it might be like that.

i always find it hard to put thought process to words, so hopefully im making sense..

[R31Nismoid]

Factory EVO's also drop boost heavily in the upper RPM in factory conditions on purpose. One could perhaps suspect that to be more about other issues like...

1. Emissions

2. Mechanical lifespan

I say this as opposed to turbo comp maps perhaps running out of flow as with decent boost control though they will hold 20-24psi to redline no drama.

I would tend to see what you mean overall, the spoolup/midrange would seem to be the more crucial part of turbo selection. The top end/off chart stuff does seem to occur a fair bit when you dig into various setups.

Although one thing RE: larger housing. Not sure about the higher shaft speed with the same exhaust flow.

[GTScotT]

agreed on the boost control, while mine (E4) in factory trim held 1 bar to redline from the 2xxx it made it, a 'friend' using a factory E9 turbo and eboost2 pushes 27 flat to redline (on the stock 10pound actuator). yet the E9 has a revised comp cover, where as i later had issues seeing more than 1.2 to redline on my E4 turbo, yet it had no issue of 2+ in the midrange (altho i still want to burn that HKS EVC5).

As for the shaft speed vs exhaust flow, thats more of a personal theory im still toying with... hard to describe at this stage.

[Simon-S14]

Good stuff, i'd prefer to call myself skeptic though, but each to their own.

I'm happy knowing that I've highlighted your factually incorrect statement.

Nothing worse than misleading users of this forum with blatantly wrong information and claims... Claims like Hub dynos are in RWKW - which are wrong.

lol prove to me that wheels and tyres take 30 rwkw to turn....

[Birds]

[soturi]

TAFE DRAWINGS FTW

[bR33nt]

i just finished tuning a std R33 (PFC, FMIC and EXHAUST), i put it on the dyno and tuned it, then fitted cams and cam gears (vct removed) and lost no power anywhere (on identical boost), here are the graphs. Lots of Cam gear dialing but it was worth the effort. Next mod turbo.

hehe i have same name as the guy whos car u did the cams too

[discopotato03]

Really a GT3776 is a long way from a GT3076R//GT3037 52T . From the compressors point of view those use a 0.54 A/R GT40 compressor housing where the BB one uses a 0.60 A/R T04E housing .

Near as I can find the 52T GT3076R/GT3037's compressor map is similar to the 56T version but moves everything about 3-4 pounds to the left of the map . The center island is about 78% and is wider that the 56T's one .

Not rare anymore , Bretts decided to keep a small stock of these 52T cartridges and their port shrouded compressor housings at GCG .

A .

[discopotato03]

I forgot to add that when a turbo manufacturer makes a range of compressor wheel trims often the mid sized one is the best match for the turbine wheel , larger and smaller trims can be used to tune the maximum airflow either side of the middle one depending on whats needed .

The production engineers at Garrett in the US I used to be able to speak to always liked the mid or 52T GT3037 , possibly the overall response was what they liked and power/airflow was more than adequate . Really there's only about 3-4 pounds odd airflow difference between the 52 and 56 trim GT37 so maybe 30-40 maximum Hp potential .

I try to remember that not every RB25DET out there has had breathing improvements eg better porting/valve sizes/cams/manifolds so the limitations may not actually be caused by the turbocharger itself .

People have said that the OE exhaust manifold becomes a limitation at ~ 300 Kw and the std porting and cams probably needs the boost to be reasonably high to get to 300 Kw .

Many will probably disagree but I reckon sizing turbos to work within the gas flow parameters of the head and manifolds makes sense , having a turbo with the capacity to go beyond these flow limits I think means you can't use a lot of the big turbos potential so why bother . Often the larger turbos don't boost till higher up the rev range and then the flow limitations are reached befor the capacity of the turbocharger is .

IMO to have a wide power range the turbo needs to have just a bit more flow capacity than the engine does on boost . If you take turbos to the bleeding edge airflow wise they blow pretty hot which is not what you want at the rev ceiling .

It also makes sense to try to aim to have the engines torque peak correspond with the middle of the island of highest (coolest) pumping efficiency - coolest charge temp and highest volumetric efficiency should make for highest torque numbers if tuned properly .

A .

[Don Dada]

So are u saying if using a std rb25 head the 56 trim might be the better way to go for 300rwkw to get the extra flow without winding the boost too high???

[soturi]

rb25 + 56 trim = filfy loops and who doesnt like them?

[Don Dada]

I forgot to add that when a turbo manufacturer makes a range of compressor wheel trims often the mid sized one is the best match for the turbine wheel , larger and smaller trims can be used to tune the maximum airflow either side of the middle one depending on whats needed .

The production engineers at Garrett in the US I used to be able to speak to always liked the mid or 52T GT3037 , possibly the overall response was what they liked and power/airflow was more than adequate . Really there's only about 3-4 pounds odd airflow difference between the 52 and 56 trim GT37 so maybe 30-40 maximum Hp potential .

I try to remember that not every RB25DET out there has had breathing improvements eg better porting/valve sizes/cams/manifolds so the limitations may not actually be caused by the turbocharger itself .

People have said that the OE exhaust manifold becomes a limitation at ~ 300 Kw and the std porting and cams probably needs the boost to be reasonably high to get to 300 Kw .

Many will probably disagree but I reckon sizing turbos to work within the gas flow parameters of the head and manifolds makes sense , having a turbo with the capacity to go beyond these flow limits I think means you can't use a lot of the big turbos potential so why bother . Often the larger turbos don't boost till higher up the rev range and then the flow limitations are reached befor the capacity of the turbocharger is .

IMO to have a wide power range the turbo needs to have just a bit more flow capacity than the engine does on boost . If you take turbos to the bleeding edge airflow wise they blow pretty hot which is not what you want at the rev ceiling .

It also makes sense to try to aim to have the engines torque peak correspond with the middle of the island of highest (coolest) pumping efficiency - coolest charge temp and highest volumetric efficiency should make for highest torque numbers if tuned properly .

A .

Would like to hear your opinion on my previous statement Disco

Thanks

[discopotato03]

I don't see any reason why the 56 compressor trim version of this GT3037/GT3076R would do it any easier than the 52 trim one . From memory , airflow wise , the 52T is good for around 49 pounds (by mass) of air and the 56T ~ 54 pounds . The rule of thumb is 11 Hp per 10 pounds of air though I work off 10 (hp) not to be on the hot bleeding edges of the comp maps .

So in theory 490 and 540 Hp potential (367 and 405 Kw) based on compressor airflow maps .

If you input the bleeding edge numbers you get 539 and 572 (404 and 429 Kw) potential Hp's worth of air .

A .

[Don Dada]

Those figures you posted seems kinda high

Hks rate theirs at 450 for the 52trim and 480 for the 56trim.

Using these numbers, wouldn't the 52trim be pumping near its max to make 300rwkw on a std rb25

[JonnoHR31]

450 is about 280rwkw

[Harey]

450 is about 280rwkw

Plus I thought HKS rate their turbos at only 15psi.

[discopotato03]

The Garrett numbers I posted are based on what the compressor sections can do airflow wise , and a formula of what quantity (by mass) of air and the power potential that quantity has .

Not all RB25's are created equal , with mods some flow more gas in/out far more easily than others .

Because a turbocharger has a set capacity doesn't mean an engine can run it to its limits .

A .

[rad100]

well i had to scrap the hks manifold as there was literally no room! so now im back to the stock manifold and still there is bearly any room.. turbos housing hits power steering lines etc running down the chassis..

has anyone had any issues fitting one to a rb25 R32?

y do they not fit as easy?

ahhhh ready to dump it all...