Basic 16v head porting

Discussion in 'JMRacing' started by mr hillclimber, May 5, 2011.

  1. mr hillclimber Club GTI Supporter and Sponsor

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    As the title, and as promised "aaaage's" ago.. getting basic flow increases for little effort for the 6A / 9A / ABF based 16v.

    I'll jump in and out of this thread to update figures as I write it and ad pics etc, so for those interested in having a go you'll have to check back here for missing info, but if I dont start at some point it'll never get done.

    The basic process is the same as in the 8v guide (see the sticky in the 8v section), so for now refer to that for tools, safety & basic feel & finish.

    The std heads I've tested to date are 9A & ABF based. The 9A I tested in std form made a peak of 104.0cfm @ .470 thou, and the ABF made 110.9 at the same lift. The ABF also had better flow straight off the seat & right through the lift range, but the 1st round of mods will take a 9A past a std ABF, and I'd suspect, tho I've not tested it, the final result will be the same on the ABF...i.e the same final figure not the same numerical increase... so either 9A or ABF based heads will (I believe) come out to a very similar, if not much the same, final flow figure.

    So, what's the first magical ingredient?

    It's quite simple... if the std guides & stems are in exellent condition, all that's needed is a trip to you local machine shop and have 3-angle seats cut in the head, the valve head back cut to 30 degree's from the new seat (on the valve), and the new lower seat angle in the head now needs blending into the throat/bowl area, with the lower angle opening to a throat size of 27mm, and with the top angle fethered into the chamber to remove both sharp-ish edges from the seat cutting process.

    If the guides are at all worn then obviously they must be replaced, and the valves stems need to be checked for wear, and again, any exessive wear found should render the valve scrap. But apart from the above thats it... no porting, not even tapering of the valve guide, though if new ones are fitted then it would'nt hurt to have that done, though the flow increase at this level will be very small for the cost involved... the idea of this exercise is to produce the maximum result for the minimum outlay.

    So what is the result?... well.. it's this... new figures in bold

    9A... .050 20.2-23.9, .100 40.5-48.8, .150 59.5-71.1, .200 78.6-88.7, .250 90.4-102.4, .300 98.1-109.6, .350 99.9-110.5, .400 101.0-113.1, .450 102.0-114.3, .470 104.0-113.7.

    So far so good.

    For comparrison, the std ABF came out at...

    .050 21.3, .100 45.0, .150 66.4, .200 82.2, .250 91.4, .300 102.1, .350 106.1, .400 108.0, .450 110.3, .470 110.9.

    As can be seen, the std ABF is better than the std 9A in this case, and like I said earlier, I'd expect the ABF to come up to similar to the 9A with the same seat cutting as I'd say the advantage the ABF has in this particular case at least is a better base casting in the seat area.

    So... what are you waiting for!

    If you only ever do the above you'll end up with flow up to the mid lift point more or less as good as anything you can buy, and you wont be lacking much at the top end, as you'll see with the next round of mods, which will get you to within a couple of cfm of many off the shelf pro heads.
     
  2. TrackCab16v Forum Member

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    just a small point is that i found it much easier to navigate around around the ports with the valve guids removed, much easier to get a better finish even for a novice , plus you do need some a basic . rotating equipment capable of spinning a small cutter and a flap wheel .
     
  3. mr hillclimber Club GTI Supporter and Sponsor

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    Very true indeed... if the guides need to come out and a full porting/throat job is being undertaken... guess what's coming in the next instalment! :lol:

    If no further work is needed/required other than the seat mods and/or the guides are in good nick then the guide boss can be left alone.
     
  4. mec82 Forum Member

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    Since you've done all the hard work I thought I'd help out :) I need to see graphs really to take things in so here we go...

    Lift (in) std 9A modified 9A std ABF
    0.05 20.2 23.9 21.3
    0.1 40.5 48.8 45
    0.15 59.5 71.1 66.4
    0.2 78.6 88.7 82.2
    0.25 90.4 102.4 91.4
    0.3 98.1 109.6 102.1
    0.35 99.9 110.5 106.1
    0.4 101 113.1 108
    0.45 102 114.3 110.3
    0.47 104 113.7 110.9

    [​IMG]

    Keep up the good work, its rare you get to see hard data to back up modifications so thanks!
     
    Last edited by a moderator: Dec 21, 2013
  5. mr hillclimber Club GTI Supporter and Sponsor

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    Good man..many thanks.

    I was hopeing someone would do that..saves me scanning in since the graph off the flowbench at the end.

    Yr welcome. .There's more come..;)
     
  6. milesmk2 Forum Member

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    I've noticed there is a slight gap between the inlet port on the head and the gasket, so would there be a benefit from opening the port and the inlet manifold to fit to the gasket?
     
  7. mr hillclimber Club GTI Supporter and Sponsor

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    No not at all..the port mouth area is plenty big enough. Gains come in this order. . .Seats, throat at either side of the guide, throat bowl, ports either side of the divider.

    Seats with light port work will give you what you can mostly buy...simple and straightforward.

    More advanced work comes from more throat and bowl work.
     
  8. milesmk2 Forum Member

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    There any way of doing this yourself in an accurate manner?
     
  9. Ben S

    Ben S Forum Junkie

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    How does the flow data translate into actual engine output?

    For example: Get two vehicles running same engine (e.g. mk2 KR), optimise them to same level, dyno them to show they are comparable. Fit the flowed head to one car re optimise, then take both back to dyno & run again, then show the differences.

    Not impossible to get that info for a company trying to promote head work

    Often, before and after head work dyno comparisons also feature different cams, increased compression etc. Meaning the effect of the worked cylinder head is still unknown.

    :)
     
  10. mr hillclimber Club GTI Supporter and Sponsor

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    All the seat cutting needs to be done by a machine shop..the blending is done with a flap wheel..details in the 8v porting thread.
     
  11. mr hillclimber Club GTI Supporter and Sponsor

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    Not at all impossible. .If someone wants to pay the labour and dyno bill, and find 2 identical 16v's.

    I do plan on doing an engine dyno session at some point, though a 16v head has just left me today destined for a very prominent car on this very forum...and there's a full race/hillclimb spec engine under construction. .That'll prob be running later in the year...if they don't make the power it wont be because of a lack of airflow that's for sure.

    In general terms, a ported std valve head of most types should make around a 10% power gain. .There are some exceptions...some of the newer generation engines have fantastic airflow as std, and ported versions arnt showing massive gains.
     
  12. Hotgolf

    Hotgolf Paid Member Paid Member

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    You can cut your own seats, with something like a Neway seat cutting set. But, and its a big but, they are difficult to keep concentric, having found out myself.
    The only disadvantage with pressing in new guides with bosses removed is that they tend to get 'pushed' away from the highest edge supporting it, even when pressed in very carefully, meaning cutting the seat that much much deeper to square things up. Not too bad as long as you deshroud the valve after. Again, learnt this the hard way.
    Serdi machines are the daddy!
     
  13. Toyotec

    Toyotec CGTI Committee - Happy helper at large Admin

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    The second hypothetical car does not have to "identical". It must just be capable of a consistant result on the same rolls compared the the car with stepped changes. This car will be the reference or correlation vehicle.

    If a flowed head generally shows a delta of 10% in power this should be reflected in torque somewhere in the rev range with gradual or overall separation in torque from one plot to the other from low speed to high speed and not just a peak point.

    Depending on your relation with the dyno owner, information like this is very tidious to arrange and control but is the sort of work that seperates the effect of cylinder air path reprofiling from other bolt ons making up the airpath which ulitmatley affects your mixture preperation, burn, cylinder pressure, torque and eventually vehicle forward force.

    Later heads have this air path modelled to take into account what you do on older engines to make the above process of combustion more efficient. These days crappy burning engines of pre mandatory EURO legistration and pollution control days are a thing of the past and customers demand almost modified Pinto engine power and torque to drag around their long geared tanks while Brussels is kept happy!

    I digress.

    I will pm regarding an experiment which I am about to embark on on said 16v 051103373D unit. Your guidance will be appriciated.
     
  14. milesmk2 Forum Member

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    Im a dab hand with a flap wheel. I'll take the head to where i normaly have them skimmed and ask if they can do the valve seats into a three angle seat. Do i need to take the vales with me and have the 30 degree angle cut into them?
     
  15. Ben S

    Ben S Forum Junkie

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    From the examples you listed it seems even then it will be very difficult to say what effect the head changes had on their own. The full race spec engine, all that you will know is that this compression with these cams with these throttles and this head = this, but not what each bit does individually. Would the race engine perform just as good without the flowed head?

    10% is very general yes. If that was proven I would be saving up to purchase headwork right now. 10% average? 10% gain @ peak? 10% over entire rpm range? 10% gain @ peak but with a 15% loss everywhere else?

    Would the ABF fall into the newer generation you mentioned?

    I'm purely coming from point of a potential customer, great that head B flows better than head A, but I want to see if the improved flow improves the torque. We could show that a paper air filter flows x amount and some super typhoon turbo extreme cold intake flows 40% more in lab conditions.. but when bolted to the vehicle it makes 0.5 Nm more @ 6000rpm and the dyno operator isn't sure if it's genuine or just noise. Until evidence is shown otherwise, a similar view could be taken to flowed head vs. standard :)
     
  16. mr hillclimber Club GTI Supporter and Sponsor

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    That's true to a point...a decent flowing modded head should provide an increase on its own, plus extra when cams with more lift are used to take advantage of any extra flow at the top of the lift curve...so that alone makes estimating the heads contribution difficult. .If swapping from a modded head to a std one for instance you'd be taking away some of the cams effectiveness.

    The race engine would never perform the same with a std head. If that was the case, an 8v head could be dropped onto a 16v block and it would still make 140hp...compression ratio aside.

    Nope...the ABF is'nt new generation...Manufactures appear to be going for improved efficiency with much better head flow...Honda have been at it for a long time...some Ford/Mazda units are excellent in std form.

    The percentage gain again can be difficult to ascertain exactly. .engine spec, condition, testing equipment, processes. ..Take yr pick. There should be no substantial loss at the low end, or anywhere for that matter unless the set-up is wrong after fitting...insufficient fueling etc.

    The engine that the head has just gone out for has been tested before so we will soon see how it works on that application.
     
  17. milesmk2 Forum Member

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    Can you do that then? Put a 8v head ona 16v block and see a power increase? Or am i just not reading this right?
     
  18. mr hillclimber Club GTI Supporter and Sponsor

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    Err..nope. The point I was making was that less airflow wont result in the power staying the same.

    I'll get some pics up to go with the basic mods described at the start of this thread along with some flowtest graphs as soon as I can spend some spare time on the flowbench.
     
  19. milesmk2 Forum Member

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    Thought as much.

    Ive found a place that can do the three angle seats and grind the valves to suit the new seats.

    Is this the limit of what you can do with a 16v head? There dosnt seem to be much else you can do from looking down the ports.
     
  20. mr hillclimber Club GTI Supporter and Sponsor

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    Ah good.

    No not at all!...

    Depending how far you want to go, a lot more flow can be gained, but it's not so easy as the initial mods. Cutting the seats & back cutting the valves, plus a small port increase will give a decent gain, plus a throat increase and yout getting into the same gains as some of the heads available. After that, more throat and port work will bring the gains up again... but thats past the scope of this thread.
     

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