Cold air intake tips for S30Zs - the CRX solution... | The Z Club of Great Britain
  1. The Z Club relies on the support of it's paid members - join the club or renew your membership here.

Cold air intake tips for S30Zs - the CRX solution...

Discussion in 'Tuning & upgrades' started by richiep, Mar 5, 2019.

  1. richiep

    richiep
    Z Club Member

    Rather than put this in an update on the “what did you do this week” thread where I’ve documented the first few steps with this mod, I thought I’d create a “how to” post to cover some info that people might find useful should they want to go down the same route with adding a cold air box intake system to their L6-engined S30Z.

    The cold air box I’m using is the fibreglass one sold by Mr.F, which is based on the carbon fibre ones developed and sold by Steve Kiddell and Pmac a bunch of years back.

    Why a cold air box? Because power! It’s more nuanced than that really but, as Steve himself proved via dyno testing, this airbox design is good for up to 15HP extra. The design firstly allows for a ducted intake arrangement that delivers cold air from outside the engine bay directly to the carbs/ITBs. Like other engines, L6s love cold air, with greater density increasing flow. The standard Z engine bay gets hot, so the typical carb setup (triples or SUs) is drawing hot air in with less efficiency.

    There is also an inherent challenge associated with reflected pulses generated between the carbs and the inner wing; I’m not an expert on the science here, but Steve’s extensive dyno testing revealed these pulses to be a source of power loss and dead spot creation. The airbox design negates this. It’s been discussed on previous occasions.

    Anyway - the installation and why I’ve mentioned a Honda CRX in the title...

    Firstly, these airbox installations aren’t a super easy plug and play thing. You need to cut and drill the backplate to suit your carb/manifold spacing and affix the hinges yourself. Also, whether you can fit one is dependent on your intake manifold dimensions. Specifically, if you have a Cannon brand triple carb intake manifold, you will need to change it! The Cannon has runners an inch longer than most other options, leaving no room for the airbox between carbs and inner wing. As detailed in the other thread, I ditched my Cannon for a Japanese Harada/Kameari 40-45mm intake, which is a great quality, well designed and proven option that comes equipped for both rod and cable linkage options. It is also great value for money versus the extortionate U.K.-made options.

    Beyond that, it becomes a case of what components you want to use to filter and feed cold air from in front of the radiator support. This can be done non-invasively. In my case, I have used:

    Ramair 76mm/3” i.d. output air induction filter

    A 90deg bend stainless tube 76mm o.d. (This was trimmed at one end to allow for tucking the filter away from the bonnet hinge rods that run across the car in that area)

    A Ramair silicon hump hose joiner 76mm i.d. (fits through the top hole in the radiator support where the air vent tube normally goes; the hump locates it nicely between the skins of that opening)

    A silicon straight reducer hose 89mm-76mm (this fits on the inlet of the airbox and steps it down for the next rest of the intake)

    Beyond that, people have used things like the flexible wired induction tubing stuff to connect from the airbox to the rad support. However, years ago, someone on this forum made a discovery I filed away to use now - the cheap generic induction kits available on eBay for 1988-1991 Honda CRXs come with a long 76mm/3” polished aluminium pipe with multiple mandrel bends on more than one plane in it. It is possible to cut a section out of that tube that is exactly right to connect the airbox to the hump joiner hose through the rad support. Not as flexible as a floppy wired hose, but the silicon sections should give adequate flexibility for engine movement. And it looks the part too.
    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]

    Obviously you end up with a few superfluous bits from the induction kit, although one could use the filter as opposed to what I did. Here’s a link to an example. Mine only cost £25 including postage:

    https://www.ebay.co.uk/itm/Air-Indu...764266&hash=item1a3fa42b54:g:HPMAAOSwZltb7pWd

    Hose clamps were good quality stainless ones.

    All parts other than the airbox were bought from eBay.

    Anyway, hope that helps as a tech thread. There are other things that could be done obviously; I wanted to create a quality looking setup that looked professional. Something that might be worth adding is some sort of securing bracket or something for the air filter, along with maybe a shield to help it avoid muck/direct exposure to water should one find oneself driving in a rainstorm!
     
    tyroguru, AliK, toopy and 4 others like this.
  2. Nik

    Nik
    Z Club Member

    That looks brilliant, thanks for writing it up. I've put one of the K&N filter kits on my 280, it came with a bracket that slots into where the stock unit would have been. When I have switched over to carbs (SU's) I am planning to get one of those air boxes and create something similar. Using the Honda pipes is a really good idea, think I will do the same thing.
     
  3. SeanDezart

    SeanDezart
    Z Club Member
    Official Trader

    It's great but for LHD cars, it eliminates the fresh air to the drivers' feet.
     
  4. franky

    franky Well-Known Forum User

    Thats a really neat setup. The airbox looks a 'carbon' copy of the old R-factory(IIRC) one?
     
  5. richiep

    richiep
    Z Club Member

    Aww, bless!

    :p

    TBH, if that’s a genuine consideration for someone, then the airbox is wasted on them. Their concerns are elsewhere than maximising performance. Of course, there are other holes in the rad support, but the top one is the only one that can be used without cutting to enlarge it.
     
  6. richiep

    richiep
    Z Club Member

    If I remember rightly, Steve’s design was based on/inspired by the ones produced by Top End Performance in the US but incorporated design improvements over those pieces.
     
  7. SeanDezart

    SeanDezart
    Z Club Member
    Official Trader

    I don't agree with your first statement but do with the others.
     

    Attached Files:

  8. jonbills

    jonbills
    ZClub Administrator
    Staff Member Moderator

    Great write up Richie.
     
  9. johnymd

    johnymd
    Z Club Member

    A subject that very much interests me and I'll be looking into improving the filtration on my current project. I have calculated that my existing setup will only filter particles that are over 23mm in size with the butterfly shaft providing most of this.
     

    Attached Files:

    peter_s and Mr.G like this.
  10. johnymd

    johnymd
    Z Club Member

    This is one of my favourite air boxes that was filled to my mates Anglia. This company made it for him as a one off. I look at it nearly everyday as it's sitting on the bench in the workshop next to mine and it is a work of art. The plan is to take a basic mould from it and extend it for a triple setup. Then turn the inlet to face the other way. The inlet is a very large opening with a reversed cone filter built into it to enable the ram air effect.
     

    Attached Files:

  11. SeanDezart

    SeanDezart
    Z Club Member
    Official Trader

    So, look out for and avoid bird-strikes !
     
  12. strugrat

    strugrat
    Z Club Member

    Good work Richie. I have something similar but have used flexible ducting rather than Aluminium tubing, and incorporated a filter shield mounted under the front radiator panel support (to protect from debris and or water ingress if its raining). Have to admit I prefer the Aluminium tubing you have used :thumbs:

    IMG_20180915_142120.jpg
     
    AliK and johnymd like this.
  13. uk66fastback

    uk66fastback
    Z Club Member

    Great work Rich. Really neat and tidy.
     
  14. STEVE BURNS

    STEVE BURNS
    Z Club Member

    I wish that I had had a filter shield on mine when I went on tour of Ireland Trip and coming back to Dublin we hit one of the worst storms they had had for years and had to get the car recovered back to England and put Pauline on a plane to fly home
     
  15. johnymd

    johnymd
    Z Club Member

    Would this be classed as a bird strike?
     

    Attached Files:

  16. atomman

    atomman
    Z Club Member

    Great work Richie ,

    Are you still running trumpets inside the airbox ?

    From the dyno work I have done in the past this helps more than just running a airbox straight into the carbs.
     
  17. Nik

    Nik
    Z Club Member

    I was wondering the same thing. Does it matter if they are short ones or long ones?
     
  18. strugrat

    strugrat
    Z Club Member

    I don't know how effective it is yet but hopefully better than nothing!
     
  19. richiep

    richiep
    Z Club Member

    Yes, the trumpets are still there, inside the airbox.

    Trumpet length affects performance. You can actually get variable length ones, like those from Emerald/Dave Walker, allowing for tuning of the optimum trumpet length depending on target for the engine. Short story - EDITED FOR BEING A DUMBASS AND GETTING IT BACKWARDS- see Pmac’s post below!

    I’ll be interested to see if I perceive a difference given I’ve taken 1 inch out the total inlet tract length swapping to the Harada manifold, but have added horsepower via the airbox. Will conduct seat-of-pants dyno testing on Cheshire A roads in a few weeks...
     
    Last edited: Mar 7, 2019
    atomman likes this.
  20. pmac

    pmac Well-Known Forum User

    "Short story - shorter trumpets/inlet tract length equals less top end but more response across the range/lower down; long trumpets - maximises top end but less low end performance."

    Wrong way round!!!!
    Correct answer is.......
    "The very short answer to the final question is that short, wide inlet runners move the torque curve up the rev range whereas long, narrow runners move the curve down the rev range. BUT - there is a whole lot more to it than that. The effect is caused by 'pulse waves', waves of relatively high and low pressure in the runner."

    For more info see Dave Walkers article on the development of his adjustable length trumpets......
     
    AliK and richiep like this.

Share This Page