What Is The Best Way To Reach 320 - 360 Rwkw For My Rb25det ?

[Behind Horizon]

Hello guys,

as Gary is on holidays for 5 weeks i do not have somebody other to ask then you. So i would appreciate it if only really qualified members would answer my questions.

Alright, lets come to the matter im currently building my RB25DET up for drifting (70%) and circuit racing (30%). I do want to run this engine with 100 octan fuel all the time, also the engine won't see street action, this engine is for circuit use only.

Thats why i dont care how hard the turbo is coming, it just need to match its purpose, drifting + circuit racing.

My questions:

1. Ok, one big question for me is if i should go for a Garrett GT3076R or Gt3540R, which one would you recommend for the stated above power figure and which Ex A/R should i choose ?

I think these are some interesting turbochargers for my needs:

Garrett GT3076R .82 A/R

Garrett GT3076R 1.06 A/R

Garrett GT3582R .63 A/R

Garrett GT3582R .82 A/R

2. The next thing would be which kind of metal head gasket should i use, i have 86.5 wiseco pistons and i think a 1.2mm Greddy one would be enough as i dont want to run more then 1.4 bar of boost. What thickness would you recommend for my power goal / boost pressure ?

3. What kind of cams would you suggest me, i do already have the Tomei Poncams 256 in/ex and would swap them for 260 Poncams if they would match the new turbo better.

4. What kind of oil pump would you recommend me ? The engine will have a hard abuse all the time. Nissan OEM ? N1 ? Jun ?

5. What do you think of an High Energy PRO CIRCUIT LARGER CAPACITY SUMP as i will drive with semis on the circuit ? Would you suggest this oil pan or would be the standart one good enough ?

6. What kind of intercooler piping would you suggest me ? Complete 3" or 2.5" or 2.5" on the hot side and 3" on the cold side ?

7. How long would the transmission last with the stated above power figures and hard abuse ? Would you recommend me to completly overhaul the transmission and put the complete OS Giken 5 Speed set + input shaft in it ?

8. Which head studs are good enough for the power i am aiming for, standart ones or do i need ARP studs ?

9. Are the Nismo 555cc injectors big enough for my power goal or are do i need bigger ones ?

10. What size of wastegate would you choose ? 48mm or 52mm ?

11. Would you port your head ? Is it really worth the money for the ~ 0.2 bar overall less boost i need for the same amount of power ?

12. Will the Z32 AFM hold up to his job, how much hp will it support ?

Alright i think that are all of my questions, please do not forget that this engine is for a race car not a daily or weekend driver. Do not worry about suspension and brakes everything is upgraded to hold this amount of power and a lot of more.

I would be very thankful if you guys could help me.

Spec List:

Plan to buy additionaly to the stated above parts:

- GReddy Core 24R-HG R-SPEC Intercooler Kit

- RB26DET single throttle bodies + plenum with Blitz adaptor

- Eagle H-Rods

- Balance the crankshaft + underdrive pulley

- Exedy twin plate clutch

- 6-Boost exh. manifold

- Tial Wastegate

- ACL Race main and big end bearings.

Already bought:

- RB25DET S1

- Wiseco forged Pistons

- Tomei 256 cams in/out

- Walbro 255lph fuel pump

- Z32 AFM

- Apexi AVCR

- Apexi PFC + Commander

- Apexi Air filter

- HKS Exh. Cam pulley

- HKS cam Belt

- Sard Fuel Pressure Regulator

- Nismo 555cc injectors

- Greddy oil filter relocation kit w/thermostat plate and 19 row oil cooler

- Splitfire Coil Package

- Cusco oil catch tank

- Kaaz 2-Way LSD

- DSS 1-Piece alloy driveshaf rated to 700hp

Edited August 12, 2007 by Behind Horizon

[Guilt-Toy]

your going to have to replace the walbro pump and the 555cc injectors. they wont cut it.

You should be going for the T04Z or the GT3582r

For track / drift you will need the JUN pump with the crank collar.

Standard head studs are okay but if your going to be tracking and drifting get ARP studs if you do use standard studs then buy brand new ones from nissan. the ones i got cost me $80 or so.

2.5 hot and 3 inch cold does my car fine

Z32 AFM will be the one for the task. the V8 AFM will just start to run out of resolution.

Playing with the head will never hurt... but i dont think its really needed

The crazy japs have put 500rwkw through a rb25det box.. just dont smash the gears when changing and they can last a while. (Just Jap have BRAND NEW RB25det gearbox's for sale and quoted me $2,800) cheap as!!

thats all i can really help with... i dont want to suggest cams or head gasket etc as mine are all standard except for the acl cometic 3 layer head gasket.

Edited August 12, 2007 by Guilt-Toy

[Adriano]

1. .82 gt3582r

2. 1.2 Greddy one will be more then adequate, just make sure the comp ratio doesnt go too low, and the squish doesnt end up too big.

3. The cams you have wont limit you getting the power, unless you really feel the need to spend more money

(and have some left over)

4. If your building a serious car, dont waste your time, get an external pump and never have to worry about it breaking

5. Upgrading the sump will be the cheapest part of building this, why skimp there

6. 2.5 -3"will be fine

7. Hard abuse, probably not long, to handle this power with hard abuse, a holinger is the only thing up to the task, abuse wont be necessary though.

8. Once again, they are cheap enough, the stockers arent studs, they are bolts, by the time you buy new bolts your 1/3rd way to the upgrade

9. 555's with the sard reg will come close depending on what pressure you run, although you will definately need a better pump.

10. There is a formula on here to figure out the optimal size, need to search

11. I would certainly get the head cleaned up, best $1000 spent on the motor.

12. I think th z32 may max out, but not sure

[Behind Horizon]

Thanks for the reply so far Guilt-Toy and Adriano , are there any other opinions ? I think the turbo choice will be the key for choosing other components, however i'm favouring the Garrett GT3582R .82 A/R by myself for a long time now.

Edited August 13, 2007 by Behind Horizon

[Dale FZ1]

Examine every part as working together in an inter-related system. That will get you closest to the “ideal” specification.

As briefed, you intend this to be a track-only machine. This means little/no need for a smooth stable idle of a road car engine, and the useable engine speed range is likely to be up somewhere between 4500-8000rpm. More aggressive camshafts, allied with at least some tidy-up work in the head would assist hit the target with efficient airflow. Accurate and reliable valve control at extended high engine speeds and boost should dictate upgraded valve springs and collets. Not sure why not go the route of a 26 or Neo head and get the benefit of solid lifters? Using a 26 head would automatically permit easy fitment of the multiple throttles.

Run with a GT3582, and be prepared to try both a 0.82 and 1.06 housing. The smaller size may meet your needs but you should consult with your supplier.

550cc injectors would be running out of puff, and raised fuel pressure is really a band-aid fix. Get the next size up. Nothing intrinsically wrong with Walbro pumps, you just need the correct spec. PM The Mafia for further detail on which one is good if you really want that brand.

If you have the option of AFM, go for the physically larger Q45. More voltage headroom, and the physically larger body size will be a closer match to the inlet trunking required for your turbo. It’s a balance between fine control and the sheer ability to measure what mass-flow is going through without maxing out.

Given you have new pistons (assuming different crowns to OE?), you really need to determine the desired compression ratio, and do a dummy fitup then cc the chamber. Slightly decreased static compression will not overly hinder performance, given you’re going to pump a good slug of boost into it. But until you’ve done some measuring you won’t be entirely sure which head gasket is the one you want.

Rather than merely looking at the durability of the stock gearbox, suggest you look at the effective speed ranges of the gearing against the power and expected delivery of the engine. The final drive should be considered in this equation, but you may require a closer spread of gears to meet your needs. Hollinger or Albans could help.

Bottom line for me is you will need to take the time (or pay for someone’s time) to assemble all the good bits properly. eg. just balancing the crank is of limited value unless you consider the rotating assembly of pistons and rods, and check for cracks in your crank.

I hope you’ll post up your final specs and the results of the final build? This should be one potent machine!!

[Behind Horizon]

Thanks for the information so far guys. However are there some 260° Type B Poncams out for the RB25DET S1 ?

Highoctaneracing is offering these but on tomei's official site 260° are only listed for the NEO RB25DET out of the R34 ?!

So are there 260° Poncams available or not for the Series 1 Rb25DET i have ?

[Guilt-Toy]

The Q45 AFM has less voltage resolution then the Z32. My car has maxed the AFM out at around 350rwkw where a z32 can go a fair bit further

Examine every part as working together in an inter-related system. That will get you closest to the “ideal” specification.

As briefed, you intend this to be a track-only machine. This means little/no need for a smooth stable idle of a road car engine, and the useable engine speed range is likely to be up somewhere between 4500-8000rpm. More aggressive camshafts, allied with at least some tidy-up work in the head would assist hit the target with efficient airflow. Accurate and reliable valve control at extended high engine speeds and boost should dictate upgraded valve springs and collets. Not sure why not go the route of a 26 or Neo head and get the benefit of solid lifters? Using a 26 head would automatically permit easy fitment of the multiple throttles.

Run with a GT3582, and be prepared to try both a 0.82 and 1.06 housing. The smaller size may meet your needs but you should consult with your supplier.

550cc injectors would be running out of puff, and raised fuel pressure is really a band-aid fix. Get the next size up. Nothing intrinsically wrong with Walbro pumps, you just need the correct spec. PM The Mafia for further detail on which one is good if you really want that brand.

If you have the option of AFM, go for the physically larger Q45. More voltage headroom, and the physically larger body size will be a closer match to the inlet trunking required for your turbo. It’s a balance between fine control and the sheer ability to measure what mass-flow is going through without maxing out.

Given you have new pistons (assuming different crowns to OE?), you really need to determine the desired compression ratio, and do a dummy fitup then cc the chamber. Slightly decreased static compression will not overly hinder performance, given you’re going to pump a good slug of boost into it. But until you’ve done some measuring you won’t be entirely sure which head gasket is the one you want.

Rather than merely looking at the durability of the stock gearbox, suggest you look at the effective speed ranges of the gearing against the power and expected delivery of the engine. The final drive should be considered in this equation, but you may require a closer spread of gears to meet your needs. Hollinger or Albans could help.

Bottom line for me is you will need to take the time (or pay for someone’s time) to assemble all the good bits properly. eg. just balancing the crank is of limited value unless you consider the rotating assembly of pistons and rods, and check for cracks in your crank.

I hope you’ll post up your final specs and the results of the final build? This should be one potent machine!!

[Dale FZ1]

Assuming you were prepared to upgrade valve springs while doing head work, why limit yourself to Poncams which are advertised as the "drop-in" upgrade? You have the ability at that stage to increase the relief areas to accomodate higher lift cam specs.

Other manufacturers are also out there, and there are different spec cams available. For higher rpm work, why not look at something in the 260-264 deg duration, and around 9.0mm lift?

R33racer should have some valuable experience in this area, with a fairly serious build or two under his belt.

And I will stand corrected by Guilt Toy re: the AFM.

Edited August 13, 2007 by Dale FZ1

[Behind Horizon]

Assuming you were prepared to upgrade valve springs while doing head work, why limit yourself to Poncams which are advertised as the "drop-in" upgrade? You have the ability at that stage to increase the relief areas to accomodate higher lift cam specs.

Other manufacturers are also out there, and there are different spec cams available. For higher rpm work, why not look at something in the 260-264 deg duration, and around 9.0mm lift?

R33racer should have some valuable experience in this area, with a fairly serious build or two under his belt.

And I will stand corrected by Guilt Toy re: the AFM.

The thing is that i'll need solid lifters, other springs and all of that for more aggresive cams, i wouldn't hesitate buying these parts but i think solid lifter are not necessary as i dont want to rev over ~ 8200 (redline) as i think the GT35R with A/R 0.86 will start loosing power beyond 8000 rpm.