Built Rb25/30 Power Figure ?

[bokee]

Hi guys just wondering if this is sort of normal power figure for a built RB25/30 neo head

car r33 gtst

mods are built engine rb25/30 with neo head cr 8.5:1

cams are 270 9.11mm

garrett gt3788 0.89 exhaust housing

turbosmart hypergate 45mm wastegate

haltech platinum pro plug in

PE 850cc injectors

nismo adj fuel reg

044 external/surge tank, 2x walbro internal pumps

3.5 catback, 3 inch dump, no cat

trust intercooler 600x300x76mm thick

now the question is that i only made 320rwkw on 19psi, i was expecting of somewhere of 350-370rwkw

is this sort of normal power figure or should be a bit higher

i had a look on forums here all dyno results and guys with my sort of mods are making in excess of 350ish with a gt35r

any ideas thoughts

much appreciated

[WARLORD]

check for intercooler leeks and joiner leeks under pressure.

[bokee]

yeah its been checked with pressurised smoke machine there was a small leak but a new hose clamp fixed it

[BMYHOE]

most prople making that power have a bit higher compression ratio maybe.. im at 9.5:1

needs more boost

Edited May 23, 2012 by BMYHOE

[bokee]

yeah thats what i was thinking about, yeah more boost it will be i reckon lol

[BMYHOE]

also how did you come up with the 8.5:1?

usually big profile cams like you have lowers compression so if it wasnt calculated correctly the compression could even be lower then you think.

just anther thought.

[bokee]

i didnt have cams when the engine was built, the builder told me that compression is going to be 8.5;1 so just going by what he said

[XKLABA]

so static comp ratio is 8.5-1, to low for big duration cams, to late just add boost and play with cam timing to reduce over lap which will increase your dynamic comp ratio

[bokee]

thanks bud ill have to book it in for another tune but i really dont feel like runing more than 25psi of boost i know the engine is built and all but i do want to keep the car for a bit longer and reliability is my no1

[GTRNUR]

Post up a dyno sheet.

How does the boost curve look in top end. Is it dropping off and your boost controller is having to compensate a lot more in top end or are you using a flat rate duty cycle and it holds boost well across the entire rev range?

[Walk510]

I'd point at the rear housing !! 1.06 is the housing of choice for the 25/30

[bokee]

here is one of the dyno pulls, we ended up printing this one, the boost controller am using is elect. HDI, high boost is set at 20 it just drops off to about 19 but holds steady

Edited May 25, 2012 by bokee

[bokee]

I'd point at the rear housing !! 1.06 is the housing of choice for the 25/30

way to big for street use and my liking

[MRHD66]

most prople making that power have a bit higher compression ratio maybe.. im at 9.5:1

needs more boost

what fuel cams and boost you runnin with that static CP

[TiTAN]

have you tripple checked the basics first? drop the exhaust at the dump, check the cam timing is 100% right, just because the timing marks line up on the timing belt with an RB30 doesnt mean its right if you are running the relocated idler/tensioner

[discopotato03]

The GT37xx turbos are bigish turbos - based on the BB GT4088R . Basically all Garrett did was fit a smaller lower temp spec diesel turbine into a GT4088R and use alternative housings . If you were going to race a 3 litre either of these could be good things for I'm guessing a 4-8000 rev range .

IMO road driven engines need to have good torque down low but even an RB30 I reckon would have felt better with 9-9.5 static CR and particularly with bigish camshafts .

The first thing bigger cams lose is cylinder trapping efficiency at lowish revs , if the combustion pressure was already low with the lower statcic CR and the cams lose even more then it probably feels pretty doughey down low .

I tink the trap people sometimes fall into is trying to build something that can run higher cylinder pressures without detonating - but forget where you can drive like that on public roads . I believe a good road engine has a good spread of power and I don't think you can have that and have it pulling well at 8000 revs .

Anyway your call but I think you went a bit big in the cams and turbo and a bit low in the CR . I doubt a GT37 would do much at part throttle anywhere and take its time winding up at full throttle . I think you could have made the same if not better power with a std GT3582R (maybe the port shrouded version) but even these are hardly responsive things in 1.06 AR form . Surely a GTX3076R could do 320 on a 1.06 housing and be "reasonably" responsive . If memory serves me correctly Mafia had someting like 320 Kw from a plane Jane GT3076R using the smallest 0.63 turbine housing . With the 0.82 you could probably ditch the WMI if you didn't want it .

To me power at revs is a bit like owning a Penthouse , fine if you spend all your time there but a bit pointless if you only go there occasionally .

A .

[bokee]

have you tripple checked the basics first? drop the exhaust at the dump, check the cam timing is 100% right, just because the timing marks line up on the timing belt with an RB30 doesnt mean its right if you are running the relocated idler/tensioner

yep timing is 100% correct now, it was off before the tune but we corrected it as sometimes its a bit harder to get the timing positions right with the relocated idler/tensioner, all lines up ok now

[bokee]

The GT37xx turbos are bigish turbos - based on the BB GT4088R . Basically all Garrett did was fit a smaller lower temp spec diesel turbine into a GT4088R and use alternative housings . If you were going to race a 3 litre either of these could be good things for I'm guessing a 4-8000 rev range .

IMO road driven engines need to have good torque down low but even an RB30 I reckon would have felt better with 9-9.5 static CR and particularly with bigish camshafts .

The first thing bigger cams lose is cylinder trapping efficiency at lowish revs , if the combustion pressure was already low with the lower statcic CR and the cams lose even more then it probably feels pretty doughey down low .

I tink the trap people sometimes fall into is trying to build something that can run higher cylinder pressures without detonating - but forget where you can drive like that on public roads . I believe a good road engine has a good spread of power and I don't think you can have that and have it pulling well at 8000 revs .

Anyway your call but I think you went a bit big in the cams and turbo and a bit low in the CR . I doubt a GT37 would do much at part throttle anywhere and take its time winding up at full throttle . I think you could have made the same if not better power with a std GT3582R (maybe the port shrouded version) but even these are hardly responsive things in 1.06 AR form . Surely a GTX3076R could do 320 on a 1.06 housing and be "reasonably" responsive . If memory serves me correctly Mafia had someting like 320 Kw from a plane Jane GT3076R using the smallest 0.63 turbine housing . With the 0.82 you could probably ditch the WMI if you didn't want it .

To me power at revs is a bit like owning a Penthouse , fine if you spend all your time there but a bit pointless if you only go there occasionally .

A .

point well made, yep its exactly how u described it you do lose cylinder trapping efficiency at lowish revs and it does feel like a lil daggy down low and i probably would have made the same power with d 3076 using a bigger exhaust housing.

Being a 3 L- it still is drivable but sometimes when you just want that lil extra pull at lower revs it just lacks it, but it doesnt bother me as much as i dont drive the car everyday, its just a weekend car.

Power wise i wanted a bit more, maybe i shouldve done my homework a bit better but too late now, or just simply run 25psi

i can still drop the head gasket thickness down a bit to bump up static CR, not sure what it is at the moment, have to find out.

thank you for your imput

[BMYHOE]

I'd point at the rear housing !! 1.06 is the housing of choice for the 25/30

ive made 396rwkw on a GT35 with .82 t3 rear housing.

[BMYHOE]

what fuel cams and boost you runnin with that static CP

im using 264 11.5mm intake & 272 11.5mm exhaust solid conversion

and of course E85