I can get my hands on a P.D. cylinder head, will havving it ported and polished give any advantage, i know on a petrol it will give a small gain, but how do diesels respond?

Ported I would have thought would help (done by some one who knows what they are doing and able to check flow rates) Polishing as far as I know is a waste of time petrol or diesel.

Simon

forget about polishing. My head is ported, as is my inlet manifold. True gains are yet to be realised as it needs mapping again.

Jason, why aren't you running yours at full power at the moment?

agreed, polishing is a waste of time, in fact in can lead to a decrease in performance in petrols caused by the fuel condesing in the ports, i'm not 100% sure how this would affect a diesel as the fuel is injected directly into the clyinders

Sorry to drag up old threads, but im wondering about a P&P job.

I can get my hands on a AWX or AVF cylinder head.

Am I right in saying any 130PD head will fit a 130PD engine??

(head from a '01 130bhp PD VW passat, going on a '53 Fabia vRS).

I have done a fair bit of porting and polishing myself (A-series heads, mk1+2 golf and new beetle).

Will be fitting bigger valves (not much bigger, but gotta try right??).

About porting...

For those that dont know, porting is inlarging the ports (the tunnel type bit that goes threw the head) that go from the inlet manifold to the cylinder chamber.

The idea is to get more air to the combustion chamber, so you can up the fuel.

(like when you suck through a straw, and then suck through 2.... 2 is easyer 'cos theres a bigger area to suck through).

However, if you port your head, you must make sure your inlet manifold have the same size holes, and match up perfect. Otherwise you will have a lip and flow will be poor.

You can also port your inlet manifold so you can match the head.

About polishing...

Again, for those that dont know, polishing is as its called really.

The idea is to polish the inside of your head so air can flow easyer, again to up the fuel a little more and get a little more power.

You can also polish the inlet manifold and even the boost tubes if there stainless / alloy.

However, with polishing, you can polish to a shine all the way through the head... upto the point where fuel is injected (the vRS PD head injects into the cylinder, so you can shine all the way through).

The reason for this is that fuel can condense on the side of the ports, and you will end up with fuel starvation, quickly followed by a drip of fuel!! Not good.

Some engines, usually petrol, inject into the inlet manifold, so you cant polish past there.

What i usually do is to polish all the way. Then get a fine bit of wet and dry and finly buff the shine off.

HTH.

I will try and upload some photos if i can fit this head.

Dave

Edited 11 November, 200817 yr by Lofty86

agreed, polishing is a waste of time, in fact in can lead to a decrease in performance in petrols caused by the fuel condesing in the ports, i'm not 100% sure how this would affect a diesel as the fuel is injected directly into the clyinders

Just noticed your comment.

Polishing isnt a waist of time... on some heads.

Your quite right about the condensing and loosing power.

On any engine where the fuel is injected into the clyinders, you can polish all the way through the head...

Appart from if your running Water Meths Injection type cooling, as the water will condense in the ports, which would not be healthy.

Best bet if your modding a TDi head is not to polish, as if your going to the lengths of P&P type stuff, youve probably already got W/I.

HTH.

Dave

I have a fabia vRS stock PD130 head if you want to remove any doubt about compatability.

oh my this is an oldie:O

About porting...

For those that dont know, porting is inlarging the ports (the tunnel type bit that goes threw the head) that go from the inlet manifold to the cylinder chamber.

not quite no, but your almost there, in almost all cases this is where modifiers and boy racers go wrong, yes fact, a larger port can theoretically have a higher maximum flow rating, but it's a case of swings and roundabouts, opening out the ports would shift your max ve higher up the rev range and if you go too far it's at an rpm your engine can't even reach.. you are more likely to gain more by smoothing out the valve pocket and trying to make the valve seats flow better, another common mistake i see is where the throat behind the valve seat is hogged out with the old carbide burrs or similar and this in fact leads to a decline in performance due to the loss of the venturi effect at the most restrictive place (valve).

The idea is to get more air to the combustion chamber, so you can up the fuel.

(like when you suck through a straw, and then suck through 2.... 2 is easyer 'cos theres a bigger area to suck through).

excellent point, BUT, having 2 straws means you need to suck twice as hard, and the same applies to your engine, i don't expect everybody to understand this.. forget about flow for a moment and consider the speed at which the air is moving in the port... if you have a large port, the volume of air is high but the speed at which it travels is much lower (think of your finger on the end of a hose pipe), and likewise a small port has less volume available but the air is moving much more quickly, and it is the port speed which is the most important factor in cylinder filling

However, if you port your head, you must make sure your inlet manifold have the same size holes, and match up perfect. Otherwise you will have a lip and flow will be poor.

You can also port your inlet manifold so you can match the head.

this is a matter of debate amongst many, your thoughts on this differ somewhat to mine however, it depends largely on how big the lip is, the important thing to remember about how an engine breaths is that the air does not always flow in the same direction, there's a nasty thing called reversion which is caused mainly by the camshaft allowing a cylinder to push a little back out of the intake port before the intake valve closes, this effect is reduced on diesels because a diesel has no valve overlap (but i don't want to go into cam timing:O), ok so this lip kind of prevents air flow from reversing out of the intake manifold, on the flip side of this argument is the lip caused turbulance, as with all things a compromise must be struck..

I can get my hands on a P.D. cylinder head, will havving it ported and polished give any advantage, i know on a petrol it will give a small gain, but how do diesels respond?

IMO a mere P&P will generate efficiency gains of the order of power gains available on petrol motors. That may mean you get 5-7% better fuel consumption. Maybe better torque on WOT through the mid-range.

However, the main restrictions to flow seem to be the exducer diameter of the standard turbo and the cat in the downpipe. If you go decat and at least a GT1749VB turbo, things start to change. At that point, then MAYBE! and it's only a maybe.... oversize exhaust valves and porting the exhaust from the cylinder through to the turbo is worthwhile. It really depends on whether you can do the work yourself or if you've got to buy it in.

Someone I know of ported his own heads for his Impreza P1... Though he had a big head start as he ported heads for Superbike teams!

J.

:orb_big_g Think you need to have PHD to read this thread lol

Any translators around ? lol

Jason:

How much do you want for it.

PandP cost? , PM me, cash waiting.

LittleBull: PHD. lol. Dont think so mate.

Im self taught.

TeflonTom: When Im refurring to a lip, i was talking about a big one.

You can end up getting low pressure spots in the little nook where the lip is.

I get what your saying about too big is cr@p, but was trying to explain it simply for those who might wana try and understand.

A good idea is to YouTube it if you want to find out more.