Porting

Anyone here know anything about porting? I'm after a quick lesson...

unless you can flow bench the head or get info from someone who has, the best thing to do is clean up the ports and give em a polish...
get it wrong and it can be messy...

Porting ..a quick lesson Jase...???
geeezers
ppl write whole books on it
but
briefly
its a method of improving the airflow in and out of an engine

note- ppl typically look at it in terms of getting MORE air/fuel mix into an engine but the topic should also include exhaust gas flows.

Porting looks at ways of smoothing the airflow, removing impediments
to the airflow and speeding up airflow (note-the BIGGER the port method is not always best)

to do porting properly, you need the specialised machining stuff but also a mercury vac gauge setup or a flowbench because unlesss you know what you are doing, porting efforts can actually REDUCE airflow

what do you do when you port?
you take (typically) a hand grinder (although thats going to CNC milling equip these days) and smooth out the walls of the inlet passage ..inlet manifold and cylinder head passage..to get rid of casting dags sharp corners (which cause airflow speeds to reduce) and also smooth out around the valve area (the valve stem typically runs thru the middle of the inlet or outlet tract)

you also port or match the inlet manifold to the cylinder head... ditto with your exhaust headers..the whole in the cylinder head should match exactly the hole in the exhaust or inlet manifold. why?
If not exactly matched....
the air/fuel mixture or exhaust gases have to move sideways and you get turbulance or eddies in the airflow...which slows it down, which means less power.

bearing in mind that an engine is really a big air pump...
the more air/fuel you can get in (which is why turbo or superchargers increase power) and the quicker you can get it out (which is why port matched extractors are a hot ticket).... the more power an engine makes!


thats a very quick lesson

am happy to elucidate further
as I have done quite a bit over the years (on a variety of car engines)


ciao

I know that square holed headers don't go with round port holes! Even if they do fit...kinda...

I know that square holed headers don't go with round port holes! Even if they do fit...kinda...

yep

said the man trying to fit Holden zorst extractors (square hole) to a...
FORD cylinder head (round hole)

Here's the deal.

The first photo is of the exhaust outlet. The plan was to just get in there and clean up that lip and the shitty surface. Nothing too major.

The second photo is the inlet port. About 2/3rds of the way in, there is a lip, which is supposed to be there. The problem is, it get's in the way of my reed block. The port itself is about half a mm too small on either side, so the reed block doesn't actually fit.

What I intend to do is grind out some of that lip, and widen the sides of the port by about a mm.

Shouldn't be too dangerous if I do that myself. Should it?

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you could always practice on the work bike

oh and smitty. just out of curiosity, what sort of hp gains are you looking at?

I dunno how much trouble you want to go to but if you really keen or serious, there are programes called "decktop dyno" which allow you to approximate results of any mods you do to any engine.

The programes are amazingly accurate if the data you punch in is accurate.

I have a friend who used one on a go kart engine (reed valve) and when they actually got it on the dyno the "expert" dudes there couldn't believe the power so they said it was a cheater (so they striped it down to check and found it was fully legal...which was fun because they lughed at him when he first brought it in and said he had built the motor and wanted to run it up). The guys then took all the measurements from the engine...lol....so they could do the same thing.

What I do know and can tell you about porting is that it's best to let a person who 1) knows exactly what to do to that particular engine and 2) who has either the reputation or the results to prove it.

Too many times have I heard crap about porting about quoted flow bench rates and seeing huge ports in heads only to find that it does nothing for performance at all.

For example, the ford Escort 2 litre head. It's a overhead cam, 2 valve per cylinder cast iron very heavy stupid thing but used extensively in rallying and circuit racing.

The thing is that this head can be ported so that it flows sooooo much air its not funny. The ports can be made that big that flow bench figures for this head can be compared to a Nascar engine. But this type of porting does nothing for performance. The truth is that this head has to be filled!

The inlet has a very shallow angle to the valve with a nasty right angle right near the valve head. To get power you fill the bottom half of the port and straighten out the inlet angle which by doing so creates less turbulence, plus by doing so, you increase air/fuel velocity.

Talking about 2 litre heads may not be what you want to know for this engine but it just an example of an engine where there are heaps of people who will tell you they know what they are doing. Interestingly enough Craig Lowndes father, Frank, is one person who knew all about that engine and who "knew" what to do.

....
oh and smitty. just out of curiosity, what sort of hp gains are you looking at?

nikos....depends on what else you do

you have to bear in mind that most automotive engineering (I am talking cars here, not so much bikes) is a compromise......
between reliability, ease of manufacture, cost...and performance.
Car engine parts are manufactured separately..and then bolted together but never matched in the way i describe above.
And for Joe Public, he wants a car that causes no problems, so a rough cast inlet manifold, cast iron exhaust manifold and small engine valves are what the car companies give him.

If you go all out, port and match the manifolds, change the camshaft, stick on extra carbies, shave the head etc etc, you can double the horsepower.
Just cylinder head porting by itself and port matching the manifolds would see an increase ....maybe 5% max 7-8% increase in power (leaving all else stock standard)

hth


cheers

Last edited by Smitty on Fri Jan 13, 2006 9:23 pm, edited 1 time in total.

Here's the deal.

The first photo is of the exhaust outlet. The plan was to just get in there and clean up that lip and the shitty surface. Nothing too major.

The second photo is the inlet port. About 2/3rds of the way in, there is a lip, which is supposed to be there. The problem is, it get's in the way of my reed block. The port itself is about half a mm too small on either side, so the reed block doesn't actually fit.

What I intend to do is grind out some of that lip, and widen the sides of the port by about a mm.

Shouldn't be too dangerous if I do that myself. Should it?

Jase
I guess from your comments...we are 2stroke
1st question..water or aircooled?
2nd..is the engine apart?
coz porting the zorst port will have crap back into the bore
(which will need to be got out)

3rd question.... are you wanting a larger inlet port?
or just trying to fit on oversize reed valve?

4th question...with the zorst port, it looks like the port actually gets bigger
as it moves away from the cylinder edge (out to where the exhaust bolts on)
..or is that an optical illusion?

the reason I ask is.... if the zorst port actually gets larger as it moves away from the cylinder bore,
then I would only smooth out the surface. I would not touch the lip, coz I think its meant to be there
...and without a flowbench or vac gauge, you can't measure the airflow to see whether removing the lip helps airflow.
Otherwise, I would get rid of any sharp edge on the lip, smooth it out
but not remove the lip entirely



cheers

Last edited by Smitty on Fri Jan 13, 2006 9:26 pm, edited 2 times in total.

....
oh and smitty. just out of curiosity, what sort of hp gains are you looking at?

maybe 5% max 7-8% increase in power (leaving all else stock standard)

Although, I'm told by reliable sources, that the H100 motor can give an increase from 8hp to 16hp by getting someone who knows what they are doing to take care of your ports!!

....
oh and smitty. just out of curiosity, what sort of hp gains are you looking at?

maybe 5% max 7-8% increase in power (leaving all else stock standard)

Although, I'm told by reliable sources, that the H100 motor can give an increase from 8hp to 16hp by getting someone who knows what they are doing to take care of your ports!!

Jase
my comments where based on car engines

you are correct when it comes to 2 stroke engines
they are much more receptive to porting
and power gains can be large, if done by someone
who knows what they are doing

cheers

Well, I decided to start hacking away at it. The worse that happens is I have to by a new barrel.

Well, I decided to start hacking away at it. The worse that happens is I have to by a new barrel.

thats the kinda enthusiasm i wanna hear..thata boy, got get em

Jase - couple of tips to help you out

* you can definitely remove that ridge in the exhaust port. Of course, the barrel will need to be off the bike when you do this;

* After you have removed the lip ( the best dremel tip for this is the cone-shaped one), then you need to ensure that you *radius* the port opening.
You do not want any sharp edges on the edge of the port, this will reduce ring life to buggery.

The best way to radius the port edge ( you are looking for a neat radius of around .5 to 1mm), is by hand, using a small strip of emery cloth. Just work the emery cloth around the port opening, back and forth, as evenly as possible, until you have obtained a neat, smooth edge.

The best accessory when porting is a 'magnifying table light', the kind with a 6" magnifying glass inside a fluoro tube - they allow you to check out the ported surfaces much easier than the naked eye.

As far as the inlet port mods are concerned, once again, you can port out those protruding lips no problem. The reed valves themselves dictate how much inlet mixture is allowed into the motor, and the most important thing on the inlet side is to ensure that the manifolds, reed-valve cage etc, are sealed air-tight. So any minor modification to the inlet passage is OK. As Yoda pointed out, matching gasket surfaces, etc, is the crucial aspect, due to the high speeds of gas flow.

Mate, that reed-valve block looks like you are still using reed-stops ?? Ditch them, and use c/f 2-stage reeds. They don't need stops, and will open further without breaking.....slightly more intake mixture is the result.

Take care when opening out the 'side' of either the inlet and/or exhaust ports - you need to check where the piston rings are 'pegged', so that you don't have a ring 'pop out' into a wider port opening....

Most HP gains in porting 2-strokes are made by lifting the exhaust port. It is important that you don't lift it too high, you can also put a 1mm spacer between the barrel and crankcase ( but this requires further modifications to the transfer ports.....).

NEVER polish the inlet port - this is the biggest mistake most punters make. Polishing the exhaust port is fine, not for HP, but to reduce carbon build-up.

You can double your HP from 8 to 16, you can even go past 16 , but this will need much care and attention to detail.......

Good luck mate !! Keep us posted........I love playing with the ringadingers