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Thread: CA18DET 8 Port Cylinder Head Questions

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    CA18DET 8 Port Cylinder Head Questions

    Hi guys I'm in the middle of re-building my CA and have 4 port and 8 port cylinder heads that I can use, is there any advantages to using the 8 port head?

    I've got all the vacuum actuators and bits ready for fitting the 8 port head but if there's not gain in using it I'll just keep it as a spare or sell it

    Thanks guys


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    Guest norfy's Avatar
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    i heard the butterfly system on the 8 port head is meant to give slightly better low down torque. but then again there must be a reason they havent used the same setup on other engines

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    Can't tell the difference cleanhands's Avatar
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    Supposed to give slightly more low-mid torque, but modern boost control/ management would make a greater difference. Depends how much you want to spend really.

    Apparently becomes restrictive above 300 bhp, but never seen any direct comparison. Be interested if anyone else has (power numbers not flow bench). Tuners are coming around to the fact that flow bench numbers aren't everything.

    There's probably a few people on here who really know this stuff, but they work for manufacturers and can't really share.
    Last edited by cleanhands; 01-01-2014 at 16:12.

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    8 port has throttle rod running though all the ports. That causes a restriction.

    8 port needs a JDM ECU, solenoid and all the vac valves, tank etc to work properly.

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    Guest ANDY black s13's Avatar
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    Keep it as a spare,4 port flows better,turn it into a coffee table either a very low one or a unstable dangerous thing

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    Can't tell the difference cleanhands's Avatar
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    Obviously not in this case, but I wonder if it would actually work slightly better on a basic "up to Stage 3" set up.

    Lack of JDM ECU is not insurmountable. PM me if you ever want to sell.

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    Member alanjuggler's Avatar
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    Quote Originally Posted by ANDY black s13 View Post
    Keep it as a spare,4 port flows better,turn it into a coffee table either a very low one or a unstable dangerous thing
    saying it flows better isn't really saying much though - flows better at maximum valve lift I'll go for, the 4 port is what you're looking for if you're after peak power.

    there isn't a massive amount of knowledge about tuning the 8 port, so it's going to be a more difficult road. the US forums have done more work in that area, since most of the CAs they get are JDM.
    white '94 s13 200sx scrapped - mapped to 1.45bar. OS giken box, garrett GT2876R, 950cc injectors, ORC twin plate, nistune. 349bhp/325lbft @ 1.3bar CA18DET
    white '96 s13 180sx - type g with more kouki bits - RB25DET, GTR steel twin turbo conversion, RB26 crank & rods. 2.6L VVT twin turbo, SR20 OSG box, OSG STR twin plate clutch.

    current status: poor but nearly twin turbo.

  8. #8
    Guest ANDY black s13's Avatar
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    I had read last night on this and the 8 port is not as bad as it seems,if you can get it to work as it should the 8 port is good for lower stages of tuning
    the 4 port is better for an engine with cams and higher rev limit,I found a flow chart last night but can't find it now
    edit: it was for stock 8 port v's 8 port modified butterflys removed showing the butterflys didn't cause that much flow loss
    , didn't find a 4 port v's 8 port comparison
    stock 8 port v's modified 8 port http://forums.nicoclub.com/ca18det-h...n-t436432.html

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    Member alanjuggler's Avatar
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    you have to remember that flow figures don't tell the full story - the 8 port, in theory, causes a better burn lower down given the additional swirl etc, so both better cruising mpg & better off boost response.

    that's never really been directly comparable though, given the difference in octane between the original maps.
    white '94 s13 200sx scrapped - mapped to 1.45bar. OS giken box, garrett GT2876R, 950cc injectors, ORC twin plate, nistune. 349bhp/325lbft @ 1.3bar CA18DET
    white '96 s13 180sx - type g with more kouki bits - RB25DET, GTR steel twin turbo conversion, RB26 crank & rods. 2.6L VVT twin turbo, SR20 OSG box, OSG STR twin plate clutch.

    current status: poor but nearly twin turbo.

  10. #10
    Can't tell the difference cleanhands's Avatar
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    Must admit I only started looking after seeing this thread and I'll be honest I'm quite intrigued. Smoothing out the division and creating a "long port" head could be worth a go.
    If the injector is only firing down 1 port per cylinder it could give good mixing as it hits the "pure" air, coming down the other one, in the combustion chamber, conversely it could be too much and cause the fuel to drop out at low rev gas speeds. Does the "dry" ports valve run hot causing det? How about an 8 injector set up using the 370s that everyone has floating around? Who knows, it seems worth a try.

    If a standard 4 port head has the potential for say 600 bhp and your only after 350ish then that's almost like putting a 3071 on and running it at 5psi actuator pressure and having to put up with no torque below 5000rpm. I do think sometimes there's too much emphasis on chasing numbers. I've done it myself, got cams that gave me 6% more power over 7000rpm, but lost 13% torque at 4000. Driven normally I occasionally used 7k, but I always used 4k. Found some pictures;




    Port dividers cut back creating a "short port power head"

    Last edited by cleanhands; 02-01-2014 at 16:15.

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    Quote Originally Posted by cleanhands View Post
    Must admit I only started looking after seeing this thread and I'll be honest I'm quite intrigued. Smoothing out the division and creating a "long port" head could be worth a go.
    If the injector is only firing down 1 port per cylinder it could give good mixing as it hits the "pure" air, coming down the other one, in the combustion chamber, conversely it could be too much and cause the fuel to drop out at low rev gas speeds. Does the "dry" ports valve run hot causing det? How about an 8 injector set up using the 370s that everyone has floating around? Who knows, it seems worth a try.
    Top end with all the fuel in one air steam it has to mix after going into the cylinder. Not likely to be as good for even fuel distribution as 4 port.

    Have to hope it doesn't behave like the Suzuki TSCC is supposed to with a nicely separate tumble.


    The whole idea is that low revs the non fuelled port is shut so air flow is faster though the single open port. Better turbulence from air speed and offset port giving better fuel mixing.

    The 2nd port butterflies are open under all conditions that give rise to det so valve has air flow though it. Valve head loses most heat though the seat and inlet valves stay seated for the whole power stroke and nearly to TDC exhaust, they don't get dangled out into the exhaust flow like exhaust valves do. Inlet valves without fuel cooling aren't a source of det - Ford ecoboost direct injection would be in trouble if it was.

    Quote Originally Posted by cleanhands View Post
    Port dividers cut back creating a "short port power head"
    Thats a conversion of a 8 port to a 4 port. Don't they know they can just import them direct from Europe? Gotta be much cheaper than all that work.

    Oooo the 8 port throttle bodies are dowelled to the head - ensures the linkage between the front and rear sections lines up.

    I fail to comprehend how removing the inlet butterflies affects the exhaust flow to give the gain they show. As the exhaust should be just the same on both tests, flow should be within testing repeatability errors.
    WHAT ELSE DID THEY DO?
    Or if they could get that so utterly wrong, can the inlet results be believed?


    What it proves is that the 10% gain that for a N/A engine would be huge and people would pay 1000's for aren't worth a damn on a turbo when you can just wind up the boost 2-3psi and blast the air past the obstruction.

  12. #12
    Can't tell the difference cleanhands's Avatar
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    I did post the picture of the modded 8 port to show what to me is not a good idea. As you say firing all the fuel down one port wouldn't be great for top end, just wondering what the trade off would be, that's why I mentioned an 8 injector set up. Do you know of any engines that run 2 ports of unequal cross section?

    On your last point this was my thinking behind putting more effort into the exhaust side when having a go at porting. Thinking that the inlet will take care of itself at the power level I was aiming for I just sharpened the port division and smoothed some casting marks. The back side of the exhaust port just above the valve seat (looking down the down the exhaust port) was really bad so I cleaned this up along with very slightly raising the port roof. Unfortunately a direct comparison to how it was before the work was done was impossible due to the turbo being knackered, so I just bought a 2560r. I was seeing boost below 2000rpm in 3rd gear, but never finished the work because another car got in the way.

    To be honest I'm just having a play about because it's cheap, don't think porting the head cost me more than 15 in materials, and easy to do and I want to see what works and what doesn't. I'm not after selling my ideas for a 20 year old engine that's getting rarer by the day.
    Last edited by cleanhands; 02-01-2014 at 21:46. Reason: Added a question

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    Member alanjuggler's Avatar
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    skyshack - that post isn't like for like comparison, they cover it later, it has been ported in the mean time between the comparisons.

    the 8 injector idea is probably a good way of handling even fuel distribution later but at that point you're into aftermarket ECU territory to get the functionality you need to make it work well.

    cleanhands - I've done the exact same thing in tuning, sacrifice driveability for peak power. my extreme answer to that was the RB swap I'm doing because that made the most sense obviously
    white '94 s13 200sx scrapped - mapped to 1.45bar. OS giken box, garrett GT2876R, 950cc injectors, ORC twin plate, nistune. 349bhp/325lbft @ 1.3bar CA18DET
    white '96 s13 180sx - type g with more kouki bits - RB25DET, GTR steel twin turbo conversion, RB26 crank & rods. 2.6L VVT twin turbo, SR20 OSG box, OSG STR twin plate clutch.

    current status: poor but nearly twin turbo.

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    Guest ANDY black s13's Avatar
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    That graph I posted was a bit confusing ,It was to show the butterflys and shaft assembly didn't cause that much restriction as some internet myths were saying they did
    ,another thing is people having the shaft seals leaking air/vacume as far back as year 2000 I read,
    so add 14 years and most will need new seals if 'Neesarn' still do them ? or find something else that will work
    They have their good points for off boost driving and some say faster/lower rpm spool and even better mpg so say
    (but that maybe people stuck with the 8 port bigging it up?) I don't know never used one
    but I'm not tempted all that vac lines and tank gubbins and hoping it all still works properly with out Vac leaks? + the ECU etc to run it ,
    I got a nice 4 port head tested and working sweet on my old now dead CA,
    ported lots with cut back and knife edged bridges and injector ports opened up in the manifold and matched to head
    No pics as did it 5/6 years ago will be pulling head off soon give it a fettle/clean up seals etc
    and re-using it on forged CA going back in soonish (he says)
    Last edited by ANDY black s13; 03-01-2014 at 14:46. Reason: Mongo likes Cigars! yes Mongo now kill the Sheriff

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    Can't tell the difference cleanhands's Avatar
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    Alan, that seems a fine response to the lack of mid range, commendable.

    Andy, it'd be interesting to see that head if you'd put some pictures up. While I'm rebuilding mine I may do another head with more extreme porting, but not remove the squish area this time. Pick up even more mid range, although if I do go for the baby Holset I'll probably remove it again, but still see 2 bar really early. Don't think any of this will happen this year.

    The only way I'd be interested in trying an 8 port is to remove the butterflies and all the other stuff and if the cross sectional area of the two ports is less than the standard 4 port, but I'm prattling about a head I've only seen in pictures. The 8 injector idea could be cheap by using old MX5 270s/330s or 370s and firing both from one signal, then expensive with the custom parts to get it to work. Worth a try, think 8 injector set ups pretty much disappeared once ECUs became sophisticated enough to get engines to idle with 'big' injectors. The mythical "Greys" from back in the days of "500" bhp Cossies are only 403s

    Glad you mentioned Ecoboost, Skyshack, so I can moan about it. Emperor's New Clothes is what springs to mind. My mother has had her Fiesta 125 for three months now, it's averaging 33mpg, because she has to hammer it in 2nd and 3rd everywhere, even though it has more power and torque than the 1600 Micra that she's sold to me, which averaged 38-40 all the 7 years she owned it. Oh and she started it the other day while I was holding the door open talking to her. Damn nearly took my face of it vibrates so much. Even so they're apparently tunable to 220 bhp so I'll want to buy it in a few years. Rant over.

    One thing I will say, the interior of the Fiesta is a million times better (quality and tech) than the Micra considering they are comparable cars with only 7 years difference.
    Last edited by cleanhands; 03-01-2014 at 21:54. Reason: Keep on talking crap.

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    Thanks for all the advice guys, it sounds like selling it or keeping it as a spare sounds the best route to go, given the spec
    of engine I'm building and the fact I'll have to track down a JDM ECU as well

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    Can't tell the difference cleanhands's Avatar
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    I'll have it off you at the end of Feb if you want to sell. I'll pm nearer time.

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    Member arry's Avatar
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    Quote Originally Posted by cleanhands View Post
    Glad you mentioned Ecoboost, Skyshack, so I can moan about it. Emperor's New Clothes is what springs to mind. My mother has had her Fiesta 125 for three months now, it's averaging 33mpg, because she has to hammer it in 2nd and 3rd everywhere
    I think Danielle is finding the same. TBF I've found that with every small engined car I drive - I need to rag it to go anywhere as quickly as driving moderately in a 'decent' car so the fuel economy just plummets

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    If you have replaced a small car with an Ecoboost you will be getting there quicker.
    98-01 Clio 1.2RT 5d 60bhp, 0-60 14.5sec, 100mph. 45mpg.
    98-01 Clio 1.4RT 5d 75bhp, 0-60 11.6sec, 106mph. 41mpg.
    98-01 Clio 1.4 16V Etoile 5d 98bhp, 0-60 10.2sec, 116mph. 43mpg.
    Ford Fiesta 1.0 EcoBoost (125bhp) Titanium X 5d, 0-60 9.1sec, 122mph. 65mpg.

  20. #20
    Can't tell the difference cleanhands's Avatar
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    Where on earth does 65mpg come from? Whoever said that is a liar and should not be allowed to publish it. I'm talking about a 62 year old woman who drives 30-40 miles a couple of times a week, not constant speed around a test track with 90psi in the tyres. Actual real world use of a car. I'm comparing it to a Micra 160 SR.

    Is there any truth in the story that manufacturers have an economy ECU map that the car is sold with to be able to publish the lies, then at the first service it is "remapped" for real world use and is passed off as "it just needed running in"? I've heard this particularly about BMWs since they started down the turbo route.
    Last edited by cleanhands; 07-01-2014 at 12:55.

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