Eug

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

176 posts in this topic

hey,

it's been a long time coming, thought i'd get the ball rolling on to get this into a sticky to stop all these threads popping up. i'll need your help on this guys (yes i'm looking at you; jarrod, cris, nick, ashley, rachael, scathing, skit, etc).

we need to elaborate on each section and your input on what errors i've made (if any ;) ), and add to a general wikipedia type of thing. if anyone can write up a quick section we can all contribute to expand it.

updated links, search results, etc. would be helpful

cheers

eug

points to address:

- rb30de

- rb25de into an r32

- brake upgrades for na skylines

- individual throttle bodies

-----------------------------------------------------------------------------------------------------------

How to get more power from a naturally aspirated engine?

There are many ways to get more power; it all comes down to budget and application.

Power is defined by the rate at which work is performed over a unit of time. Used in our context, power will represent the maximum kilowatts (kW) a vehicle produces as measured on the dyno. However, the key factor in the above equation to take into consideration here is 'time', which is essential for 'response'.

Being a naturally aspirated, the motor is neither turbocharged nor supercharged. This means that the motor relies on vacuum created by the cylinders and natural atmospheric pressures to draw in ambient air for combustion.

In order to get more power you will have to rely on the basic principal of: letting the motor breath/work better, so to speak. This is done by removing the restrictions within the system and thus creating more efficiency.

Here is a basic list of what can be done, we shall elaborate on them at a later stage:

  • Intake (pod filter, panel filter, larger throttle body, cold air feed)

    [*]Exhaust (extractors, cat converter, cat back exhaust)

    [*]Motor (shave the head and/or block to increase compression)

    • Head

      • Port and polish (remove restrictions in the head)

    • Oversized valves (allow more air to flow)
    • Cams (regrind, intake and exhaust side to improve breathing)

    • Gasket (thinner gasket to increase compression ratio)
    • Block
      • Pistons (increase compression, light weight)
      • Crank (light weight)
      • Rods (increase compression)

  • Electronic Control Unit (ECU)
    • Piggyback systems (SAFC, E-Manage, GTS-Link, allow modifications of engine parameters; air:fuel ratios, timing, etc.)

  • Drivetrain
    • Flywheel (lightened to decrease unsprung mass)
    • Tailshaft (one piece, carbon fibre; lightened to decrease unsprung mass)
    • Rims (lightened, forged)

  • RB25/30DE and RB26/30DE Hybrids
    • A good and useful NA motor has larger power band, this means the car is able to put down significant amounts of power through a large rev range. This is achieved by an increase in cc's -as in an RB30DE and the compression ratio*. High performance NA motors run high compression ratios (CR) to give more torque and power through in the low rpm range, this will see the motor rev faster. In the RB30DE hybrid a significant amount of the extra power being made is gained via the head, so particular attention to this area is ideal.
    • Block: RB30E NA block (Found in R31s and Holden VLs)
      • Capacity: 2982 cc
      • Bore: 86.0 mm
      • Stroke: 85.0 mm

      • The RB30 crank is nitrited standard and is strong enough to withstand a mild increase in kW.
      • The RB30 rods are suitable for simple low - mid range and mild CR motors. However aftermarket items are required for motors looking to do beyond 6500RPM, as the standard items will snap and/or crack.
      • RB30 or RB25DE pistons are able to be used. **yet to be confirmed & CR using RB25DE pistons** Using the stock RB30E pistons will give you a CR of ~8.2:1. This can easily be increased to 9.5 - 10:1 (by shaving the head, ~2mm shaved) depending on fuel availability for regular street use. It is possible to run up to 12:1 CR before you need to switch to race fuel to prevent pre-detonation (aka pinging).
      • Cam belt tensioners 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 tooth 20kg timing belt must be used.
      • All RB26, RB20, 25 and 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 are prone to cracking if used at revs over 6500rpm without a crank collar. A good supply of oil is required for high rpm applications.
      • Whilst the RB30 does have a strong bottom end it may need a freshen up as many of these engines have done over 200,000km. If you're chasing big power out of an RB30DE you will also need to think about:
        • Bearings: ACL race bearings
        • Rings: Molly ring sets or stock alternatives
        • Balancing: Best done with the harmonic balance, clutch and flywheel attached.
        • An oil cooler, oil pressure and oil temperature gauge may be required for high rpm applications.

      [*]Head

      • R32 RB25DE, R33 RB25DE, RB25DET, RB26DETT (NVCS and Non-NVCS)
      • Rb20DE/T heads will work with modification. (Link to RB30 PDF)
      • RB26DETT heads have the best flow. They also run multiple throttle bodies which are ideal for NA motors. An adaptor plate is required to attach Rb26DETT throttle bodies to the RB25 head.
      • RB25/26 heads have cc capacity of around 62-64cc's, in comparison to the RB30 55-58cc's
      • All coolant/oil galleries line up between the block and the head without any issues.
      • An oil feed from the block to the head using a T-piece is required to maintain NVCS.
      • Upgraded valve springs may be required for high power applications (See section x.x).
      • Standard camshafts, reground or aftermarket items are available (See section x.x).
        • The max regrindable standard cam profile is 8.3mm & 255º. Remembering that Lift = torque and duration = power.
        • GTR camshafts can also be reground to use hydraulic lifters. They are a recommended budget upgrade. (See section x.x) *to confirm

        [*]Adjustable cam gears/pulleys are recommended if using modified/aftermarket camshafts.

        [*]Port and polishing is recommended if looking for both power and response.

      [*]Flywheel

      • All of the RB20 and Rb25 flywheels are interchangeable.

      [*]Engine Mounts

      • The RB30DE block is approximately 38mm taller than the other RB blocks.
      • Engine mounts will need to be modified to lower the motor by 15mm on the driver's side and 12mm on the passenger's side to allow for bonnet clearance if maintaining the standard RB25 intake plenum.
      • The lower lip of the radiator may need modification to allow for fan clearance.
      • Gearbox and center bearing mounts may also need modification to reduce driveline angles.

      [*]ECU

      • RB25DE stock ECUs may restrictively be used, they are not mappable
      • If utilizing NVCS an appropriate ECU is required.
      • RB20 ECU is able to be chipped for RB30 use. *to confirm?
      • NA Z32 (300ZX 3L V6) ECUs are mappable and can be found with VCT variants and are more appropriate. *confirm?
      • Apexi SAFC can be used to tune air/fuel mixtures
      • Aftermarket stand alone ECU's (MoTec, GTS Link, Apexi's Power FC etc.) will be needed for high power applications

      [*]Results (http://www.skylinesaustralia.com/forums/Na-Power-Results-N-a-E-t138169.html)

      • 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 144kmphR

    [*]Forced Induction (not considered naturally aspirated, although nitrous is debated)

    • Nitrous Oxide (NOS or N2O, injected into the intake to increase oxygen content during combustion.
    • Turbocharging (exhaust gases used to create intake vacuum to compress and increase oxygen content for combustion)
    • Supercharging (crankshaft energy used to create intake vacuum to compress and increase oxygen content for combustion)

*RB30 data collated from information gathered from the RB30 thread (http://www.skylinesaustralia.com/forums/R33-RB30-Conversion-t15420.html) and Cubes's RB30 PDF.

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Thats awesome Eug!.. We REALLY REALLY NEED THIS!..

What will we be helping you with?.. because at the moment its pretty spot on!.. =]

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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.

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! ;)

Edited by GTS4WD

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hmm.. its a little hard to read..

But I dont know how to format on the forums

;)

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www.photobucket.com/albums/y133/brentmcd12

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www.photobucket.com/albums/y133/brentmcd12

LOL @ horns!

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Hey guys,

I am new to this site and live in the Campbelltown area. Just wanted to say that this seems like a really promising thread and I look forward to get to knowing you all..

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updated.

parts in red require clean up or more attention.

i would also like to cite references.

cris, i've re-worded some of your sentences and removed some parts otherwise it was just going to be way too big. some parts such as camshafts, etc. can be referred back to one section. especially with the rb30 section it will sometimes double up.

the costs and stuff are quite variable - as long as we're able to provide the core details it should be starting point.

thanks for contributing, hope you can add some more - any section you're not happy please let me know and we'll fix it.

wonder if we can get a wikipedia board put into this section? would be a lot easier.

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Im going to have a tackel at some of the intake mods.

Items to address. Pod filters, panel filters, cold air induction, larger throttle bodies, air flow meters.

The aim with an na engine is to make it breath as much cold air as possible, the more air that the car can suck the more power you can make.

Upgrading Panel filters are good because they still use the standard cold air intake whilst providing extra flow. they are good for a starting mod as their easy no mod instalation but when looking for huge power figures the standard air box/cold air feed will not provide enough air

Upgrading to a pod style filter can be the best sucktion upgrade you can do or the worst. Theres been lots of tests done to which pod filter suck's and filters best heres one example of higher end filters. http://www.mkiv.com/techarticles/filters_test/2/index.html. Now if these filters are just tacked onto your intake after the a/f meter they suck in lots of hot air and can actually loose power. The only effective way to run a pod filter is to run it with some type of heat sheilding.

There are sevral different ways to run your heat sheiding, you can just run some sheilding over the section of the pod which is most exposed to heat, the other way to do it is to run some sort of separation box or compleatly inclosed box.

On top of heat sheilding to run a good intake you will need some sort of cold air intake, the more cold air the better. There are so many options to how to run your cold air pretty much you need to run some sort of pipeing from the front bar up to your pod or panel filter. You can go over the headlight like the standard one but try and run a wider mouth or you can feed it up from the bottom, you could do this effectivly by cutting a hole where the standard turbo intercooler piping normally goes. There are provisions for the holes already there and this will not take from the strutural integrity of the chasis.

Larger throttle bodys. Best option most people go for is the xf throttle body. it either65 or 68mm cant remmeber. there are other options but the xf one seems to be the best size and ease to fit. Throttle body mods wont normally give you much of a power increase but they increase responce as the car can only breath as much as the capacity of the engine when on full throttle. there was some disscussion into 90mm Q45 throttle body but they are too big.

its best when putting a bigger throttle body on to increase all piping size to suit including the a/f meter otherwise you will create air flow restrictions.

This link is a guide on how to fit an XF throttle body to an rb30 but can be applied to all rb's.

http://wiki.r31skylineclub.com/index.php?t...F_Throttle_body

This is a guide and disscsion on twin throttle bodies/a/f meters

http://www.skylinesaustralia.com/forums/2-...throttle+bodies

Not best wording but the links will be usefull :glare:

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nice work jarrod, i may have to condense that a bit though.

keep in mind guys to keep it relatively formal - and not so much conversation forum style.

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where abouts is the intercooler piping spot where you can cut through to make a cold air intake? i havnt really looked at this on a turbo r33 can someone point it out on a pic or something? might have a look at this tomorrow.

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u got to cut the hole out but underneath the air box theres two indented circles

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