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Location:
Lismore, NSW
Registered:
February 2003
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Port & Polishing Turbo motor heads?
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Tue, 17 June 2003 06:22
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What are the advantages and disadvantages of port and polishing heads of turbo motors? is it worth the $200 +
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Location:
Eskilstuna, Sweden
Registered:
May 2002
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Re: Port & Polishing Turbo motor heads?
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Tue, 17 June 2003 06:40
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Probably worth the 200 bucks on the exhaust side, inlet side would probably make no difference.
Cheers
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Port & Polishing Turbo motor heads?
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Tue, 17 June 2003 07:54
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tell me where you can get a proper port and polish for $200
thats wayyy to cheap for any reasonable modification.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Port & Polishing Turbo motor heads?
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Wed, 18 June 2003 04:12
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Heya,
I'll polish your ports for $200  and blend valve seats and polish combustion chamber and blend your valve guides......
most port and polish jobs i've seen have just been a quick polish to make it look nicer. few have had any major reworking... fwiw, the exhaust ports on my K motor took me many hours to do properly... something like 30+ hours of work? if i charged myself $50a n hour i'd be laughing
seriously tho, if you are in sydney and want to make a trip to newtown/alexandria, i'll give you my opinion on your ports and what you need to do with them.
you can see some of the work i did to mine at:
http://www.materials.unsw.edu.au/~sford/headpics.h tml
but the combustion chambers aren;t polished or properly unshrouded in those pics..
Cya, Stewart
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Club President
I supported Toymods
Location:
Sydney
Registered:
May 2002
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 Re: Port & Polishing Turbo motor heads?
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Wed, 18 June 2003 04:24
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Stewart this is no reflection on you at all its just the post after yours.
Porting a head is a skill leared over MANY hours of work and understanding. Sure you can get a place that will give a quick Debure and clean up of your ports and its called porting but really getting an improvement is not an easy thing to acheive.
I have spent HOur after hour on a flow bench and have seen first hand the effects on airflow a nick or grind here and there can do... And I'll be buggered if I am porting anything I own lol
What may seem like an obvious flow restriction may well be there intentionally to increase low lift and or rpm performance. So if you are considering a port and polish of any sort make sure you get it done by someone who knows what they are doing and if you can insist on head flow figures at the appropriate lift points for before and after the work !
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Port & Polishing Turbo motor heads?
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Wed, 18 June 2003 04:44
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LOL  no reflection taken...
i definitely agree with you 100%.
the reason that porting is called a 'black art' is because most people have no idea what they are doing.. sometimes it works, sometimes it doesn't...
ideally you will want your head ported by someone with extensive porting experience in developing your head in particular.. but that's hard to come by sometimes..
the flow bench is also not the best way to determine flow figures, but it's the best way most ppl have access to.
the problem is that a port, by it's very nature, has a pulsed flow, so by putting a fixed pressure drop across it, you are nowhere near approximating the actual conditions of an engine. the only real way to get proper flow numbers is by running the head on a motor, or motor test bench, with valves operating, to get numbers that actually mean something..
finally, it also depends a lot on your application.. since auto motors have to be very flexible compared to say plane or boat or drag motors, it's impossible to port for efficiency at all rpm ranges... to get the head to flow well up high can destroy the part throttle characteristics...
also some heads are shocking and almost anything you do will help (like the K head exhaust ports, and particularly mazda 1300/1400 heads!!!!) but some i would barely touch..
for another example, i had a look at Juzzos 2TG head, and that thing is awesome from factory. only some minor machining and casting marks to clean up, and removal of a couple of sharp edges..
in general, the newer the head, or the better the original design, the less there is to do on them apart from general clean ups.. and it is vry hard to compare port to port when so many other things on a motor have such an influence...
i like porting, because it is fun, and ppl throw away K heads, so it doesn't hurt to practice and try new things , but if a new head is a few $$, then be careful about what you do to it...
Cya, Stewart
Ps, Rod, you wouldn't have a flowbench at home would you? would be interesting to do some flow data on my head when i pull it off for the EFI....
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Port & Polishing Turbo motor heads?
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Wed, 18 June 2003 04:47
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oh, and remember that piston speed and flow velocity are highest around mid valve lift, so this is where you will get most benefit from any port work.... there's no point having huge flow at 15mm lift if you spend 2 degrees there....
Cya, Stewart
have a look at the porting pics at http://www.theoldone.com/articles/ some interesting tips there...
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Location:
Darwin
Registered:
April 2003
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Re: Port & Polishing Turbo motor heads?
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Wed, 18 June 2003 04:59
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So in all your experience and wisdom, Are there reasonable gains to be made on turbocharged motors through porting/polishing?
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Port & Polishing Turbo motor heads?
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Wed, 18 June 2003 05:20
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what motor? what are the stock ports like? what size are they? what port velocity are you after (to determine port diameter)? are there any restriction in the port? are they there for a reason?
how much boost are you going to run, how often will it be boosting, what rpm range are you using the motor in, at maximum, and also, most often.
what will be connected to the ports? what size manifolds/length of manifolds etc?
there are a milion and one things you need to know before porting, as it is part of a total package.
if there was an easy answer, then everyone would know it..
for zample, compare the big and small port 4AG heads, small port is good for NA because of higher port velocity, big port is better for high boost, because it has imilar port velocity with that extra boost, but will not be great off boost...
all depends, and then it is only an educated guess until various combinations go on the engine dyno.
[Updated on: Wed, 18 June 2003 05:21]
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Location:
Lost in the K hole
Registered:
May 2002
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Club President
I supported Toymods
Location:
Sydney
Registered:
May 2002
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Re: Port & Polishing Turbo motor heads?
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Wed, 18 June 2003 05:49
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Stewart,
Mate I wish I had a flow bench ! I am lucky enough to have limited access to one (although it is in another state !)
My experience is with the T series only (mainly 2TG and a bit of 3TGTE) I still have ALOT to learn.
I actually had a play with one of my spare 2TG heads, I just removed the burrs and gave it a clean. Bottom 3 lift points dropped to the Bullshit !  Also showed very little improvement up top.
And your right about where the flow improvement is needed most.
Most people forget that. You have to consider how long the lift point is in use for.
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Port & Polishing Turbo motor heads?
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Wed, 18 June 2003 05:59
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in an ideal flow situation along a straight tube, that's totally correct (ignoring wall friction differences in higher pressure)
i take back what i said about the 4AG heads.. i think i was referring to the big ports extra potential when it comes to boosting 
this is where we get into the art of handwaving cos it's so damn difficult to quantitatively or even qualitatively model what's happening.
when the valve opens, and the piston goes down, there is a pressure difference between the cylinder and the plenum, which causes the air to rush into the cylinder (wether boosted or not).
a higher pressure differential will cause more air to go into the cylinder, but will be slowed down by the friction on the port walls, friction past the valve head and seat, and also friction from any restrictions in the port. as boost increases, the friction from all of these components increases (i can't remember if the relationship is linear or not). you can think of a port having an effective diameter, which is the diameter of the port minus the effective restrictions. as you increase the friction, you decrease the effective size of the port, and at some (high) boost level, increasing the pressure differential will not cause any more air to go into the cylinder as the port is restricting any more flow.
what gets even trickier when analysing this stuff is that the pressure measured at the plenum of an unboosted motor is a measure of the air that _didn't_ get into the cylinder. so just because a motor has more boost, doesn't mean it has higher volumtric efficiency and is getting more air into the cylinder.
i think the idea of having bigger ports for a boosted motor comes from increasing the total diameter so that the effective size when boost is present doesn't decrease as much. there will be an ideal size that nets the most gain for certain levls of boost, but i think it is beyond anyone to predict that size accurately without extensive real world testing (like with single cylinder testing they do for formula 1 motors)
i apologise for hijacking the thread a bit, just wanted to share what my thoughts are on the subject, and have you guys pick holes in my knowledge , only way to learn.
oh yeah, there will be a difference in velocity for the same size port and different boost levels. because the boost is a pressure differential, there is a pressure gradient acros the entire manifold/port/valveseat/cylinder, and the velocity at any point is a product of the acceleration of the air across this differential. the way to solve this is to quantify the pressure differential (at a given moment in time), and then do finite difference calculations to determine the velocity at each point.... and then do this for each moment in time across the whole pot event  a bit beyond my knowledge atm....
anyhoo, i'll shut up now
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Location:
Gold Coast
Registered:
May 2002
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Re: Port & Polishing Turbo motor heads?
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Wed, 18 June 2003 06:58
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Don't polish in a Turbo app.
Same principle as a golf ball.
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Location:
Canberra
Registered:
May 2002
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Re: Port & Polishing Turbo motor heads?
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Wed, 18 June 2003 22:35
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| wastegate wrote on Wed, 18 June 2003 16:58 |
Don't polish in a Turbo app.
Same principle as a golf ball.
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A golf ball is dimpled so that air flow doesn't seperate from the surface of the ball (which is slightly more aerodynamic than a brick) and leave a vacuum behind it. How does this apply to a well shaped port?
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