Jump to content
SAU Community

mwboom

Members
 View Profile  See their activity

  • Posts

    13

  • Joined

  • Last visited

  • Feedback

    100%

 Content Type 

Posts posted by mwboom

    How To Get More Power From A Naturally Aspirated (na) Engine

    in Naturally Aspirated Performance

    Posted

    The power of an NA engine is larger power band. This is achieved by an increase in cc's -as in an RB30DE and the compression ratio. High performance NA engines run high CR's as this gives you better low down torque and will push your engine in high RPM faster. Much of the power being made will be gained via the head. So pay much attention to this aspect of the engine.

    fit the turbs boys

    RB30DE (3L Double over-head cam):

    Made by using an RB30E and an RB25DE head

    Block

    - RB30E (2982 cc, bore: 86.0 mm, stroke: 85.0 mm) NA block (found in R31's and Holden VL's)

    - The Rb30 crank is nitered and is strong enough to cop a fair few KW

    - Rb30 rods are ok for a simple low - mid power/CR engine but will need to be replaced with aftermarket items once you get cams as the engine will be reving to far beyond what the rods were designed for. Stock rods wont take much more than 6500RPM. Aftermarket rods will stop you from throwing a con rod/snapping/cracking at these high rpm's.

    - You can use RB30 or RB25DE pistons. - **yet to be confirmed & CR using RB25DE pistons** Using stock RB30E pistons will give you a CR of ~8.2:1. This could easily be bumped up to 9.5 - 10:1 (~2mm shaved) CR for regular street use. It is possible to run up to 12:1 CR before you need to switch to ethanol fuel where high CR's can be achieved.

    - Cam belt tensioner needs to re-positioned. Using a tensioner and idler the timing belt tension to be greater than the factory recommended spec of 20kg's. You can use a second tensioner in place of the idler bearing in order to bring the belt tension down to the factory recommended spec of 20kg's. It is possible to use the factory tensioner and idler locations however, you will be required to use two tensioners to get the correct belt tension. Some do not recommend this method as the belt comes too close together.

    - A 152 teeth 20kg timing belt must be used.

    - All GTR, R32 RB20/25 & VL/R31 RB30 water pumps and thermostats are interchangeable.

    - It is best to use an oil pump from a twin cam motor as these provide more flow and pressure. All RB oil pumps are interchangeable. The RB pumps do have a reliability issue and crack if used at 6500rpm+ without a crank collar. Therefore, for a high revving NA engine where much of the power is found in NA head a crank collar is a MUST!

    **Note** While the RB30 does have a strong bottom end it may need a freshen up as many of these engines have done +200,000km's. If you're chasing big power out of an RB30DE you will also need to think about:

    - Bearings - ACL have race bearings

    - New rings - Molly ring sets or stock alternatives

    - Once the bottom end is back together the engine will also have to be balanced. It is best if this is done with the clutch and flywheel attached.

    - During track work and high temp conditions people have had problems with oil temperatures. An Oil gauge is recommended and oil cooler accordingly if needed.

    A cheap and low power 3L bottom end can be had for ~$500

    A high power/high comp bottom end will need (excluding previous work) ~$1500 - ~$2000

    Hardcore Race engine ~$3000 +

    Head:

    Rb25DE/RB25DET/RB26DETT VCT/NON- VCT

    - Rb20DE/T heads will work but with much machining which is expensive and will also have smaller ports making this an unfeasible option.

    - Rb26DETT heads are best flowing. The intake manifold also has more than one throttle body. An adaptor plate is needed to attach Rb26DETT manifold to RB25 head.

    - Rb25/26 heads have cc capacity of around 62-64cc's. Compared to the RB30 55-58cc's

    - All coolant/oil galleries line up without a problem

    - If your using a VCT head and wish to keep VCT you need to run an oil feed to the head using a T junction from somewhere in the block/sump.

    - R32 Rb25DE head studs will work without a problem

    - If your chasing higher power will need RB25DET valve springs as they are stiffer than the Rb25DE

    - Stock cams will work fine or you can buy aftermarket cams or get your stock cams re-grinded. The max regrindiable stock cam profile is 8.3mm & 255deg. Remembering that Lift if torque, duration is power. Adjustable Cam gears are recommended if using modified cams. GTR cams can also be regrinded to not use lifters **need to confirm** and are a cheap up-grade.

    - Port and polish is recommended if looking for power/response. Polish can be done with Brevil style drill and can be done in the backyard. Same with porting, yet for optimum performance, professional work is required.

    - Rb25 Exhaust manifold/headers can also be used in this application.

    A cheap stock Rb25 head could set you back ~$750 - $1000 (cost of head)

    A mildly modified head (excluding head) ~$700 - $1000

    A heavily worked head (excluding previous work) ***(?????)***

    Flywheel:

    - All of the RB20 & 25 Flywheels are interchangeable.

    Engine Mounts:

    - The RB30DE block is approximately 38mm taller than any of the other RB blocks.

    - If you want to run the stock RB25 inlet manifold/plenum you will have to lower the engine by 15mm on the driver's side and 12mm on the passenger's side. You will then be required to remove the lower lip of the radiators shroud otherwise the fan will munch it up. It is worthwhile to relieve the gearbox and centre bearing mount slightly. In an attempt to reduce driveline angles to an absolute minimum.

    ECU:

    - Once headwork is done and to extract more power a re-tune is required.

    - Rb25DE stock ECU's can be used but power will be limited. These ECU's are not mappable

    - If utilizing VCT an appropriate ECU is needed.

    - NA Z32 (300ZX 3L V6) ECU's are mappable, can be found with VCT variants and are more appropriate.

    - Apexi SAFC can be used to tune air/fuel mixtures

    - Aftermarkety stand alone ECU's (MoTec - Apexi's Power FC etc.) will be needed for high power applications

    Results"

    **taken from power results stickie thread**

    GTS_143

    Model: R31 GTS2

    Engine: Rb30DE

    Modifications: VCT, mild cams, ported head, lightened & balanced bottom end, big extractors & full 3" exhaust, 12:1 compression, twin XF TB's (throttle bodies), pod & CAI, twin thermos, spitfire coils, Link ECU.

    Power:149RWKW

    SKiT_R31

    Model: 1987 R31 Skyline Ti

    Engine: RB30DE with VVT

    Modifications: Extractors, exhaust, twin tb, safc untuned, billet f/wheel, reground surecams, 10.5 compression, 18 degrees timing, 98ron ultimate

    Power: 150.9RWKW @ 172kmph an 507nm (374FtLb) torque at 144kmph

    Did I miss anything?

    Comments/Abuse/flame/Advise is all welcome! :laugh:

    Insurance

    in Car Audio & Electrical

    Posted

    this thread needs to be in General Auto..

    the A to your Q is a YES

    it shouldn't affect your premium one bit, unless they're much more valuable - & even then the premium only goes up a little

    yes on all counts

×
×
  • Create New...