Exaust and backpressure

[Belgianwaffler]

Hi VanKronenburg... well I referring to flywheel figure yes it would be hard but not impossible ...40 mm valves -> +/- 30hp in street trim per cylinder.With minor porting you should be able to get around 34hp

41 mm valves -> 33hp street trim

41 mm valves would'nt be hard to fit .... okay in the end it's the cost.

[Belgianwaffler]

Hi again for those who are interested and have the cash to play ....
I have just been searching for ways to improve power without force induction.
I'm in the process of finishing a 16v head with a valve swap;
33 mm intakes with 6mm stems, std 28mm exaust valves. the head is a 2.0l head which is reported to flow well on the exaust side.
There is no porting on the head except for the seat work which had to be done to accomodate the larger valves. ("radiussing" of the seats as well).

the valves (intake) are from a 2000 ford focus "zetec" engine and are the oversize option. at 97.5 mm long they are 2mm longer than std vw intake valves... the seats in my head were not recessed and I was able to check lifter clearance which was around 1.5mm... of course I had to get some valve guides made up as 6mm would be quite loose in the old ones..

VanKronenburg how good are the std 16v springs ???

[VanKronenburg]

Hi,

The stock 16v valve springs are safe >7500rpm and to 11.5mm of valve lift. They should be replaced with new VW items with any mild camshaft upgrade or head rebuild. With a cam that needs more than 7,500rpm, one shouldn't use the standard springs.

The largest cam we recommend with the standard springs is the 268/11.5mm by Schrick.

The ONLY aftermarket valve springs worth using are made by CAT CAM, Dbilas, Schrick and our own in-house items. The rest are no better than a stock VW item.

Regarding the work you have just done to the 16v, I don't want to sound as though I am telling you what to do as it's good for people to try different things, but the modifications you describe won't aid the flow in any way.

The blockage in the 1.8/2.0 16v head is in the exhaust side, due to the near 90 degree exit bend. This needs reshaping without enlarging it much more and is where the majority of work needs to take place on this head. There is no point enlarging the valves on any cylinder head without first impoving the casting itself.

There are 6 major problems that should be adressed in a well modified stage 1 16v head. Further than this, stage 2 and 3, port shape can be considered more carefully, as can multiple-angled valve seats. Next, a valve upgrade to 34mm/28.5mm is the best option. Obviously there is much more involved than this, though!!!

I am first to admit that this is not a well designed head. The OPEL 20XE is a far better head and much easier and less expensive to modify well.

Hi again for those who are interested and have the cash to play ....
I have just been searching for ways to improve power without force induction.
I'm in the process of finishing a 16v head with a valve swap;
33 mm intakes with 6mm stems, std 28mm exaust valves. the head is a 2.0l head which is reported to flow well on the exaust side.
There is no porting on the head except for the seat work which had to be done to accomodate the larger valves. ("radiussing" of the seats as well).

the valves (intake) are from a 2000 ford focus "zetec" engine and are the oversize option. at 97.5 mm long they are 2mm longer than std vw intake valves... the seats in my head were not recessed and I was able to check lifter clearance which was around 1.5mm... of course I had to get some valve guides made up as 6mm would be quite loose in the old ones..

VanKronenburg how good are the std 16v springs ???

[20v kit car]

hanse it good to see another member giving good advice based upon experience and not rule of thumb stuff..i agree with all the principals you just outlined.Most of my experience is via a family owned vag shop and Oettinger for which we are the australian agents past 10 years.the research and development gained by oettinger in their early days was great..today these developments are less..more suited to chip tuning.I learnt alot about head porting via oettinger and its a art that must be taken seriously..the lehman cyl head from the kit car is very unique along with the 7 cut to the surface.VWM 265hp 16v is so close to the edge every time its revs your in heaven...i've been informed by VWM that the bosch ecu in the kit car should have a battery change every year..you heard of this or is it a revenue raiser....also believe an upgrade due to intake port size variation and mapping is altered to suit any thoughts,as you may expect trying to get this info in our country is non existant..thanks for any info you can put my way cheers steve muller

[VanKronenburg]

i've been informed by VWM that the bosch ecu in the kit car should have a battery change every year..you heard of this or is it a revenue raiser....also believe an upgrade due to intake port size variation and mapping is altered to suit any thoughts,as you may expect trying to get this info in our country is non existant..thanks for any info you can put my way cheers steve muller

If they say to do it, then I would be. They earn enough money to mean they needn't revenue raise!!

It does seem a strange thing to do, however. I can find the answer to this quite easily if you'd like? I don't know off the top of my head so will have to check it in one of the tech manuals.

Either way, given that good VW parts seem so rare in Australia, I wouldn't be taking any risks with anything!!

With your other question, do you mean if you change the inlet port size/shape on the head, should you alter the ECU map?

[Belgianwaffler]

point taken VanKronenburg ... my personal favorite is the BP-ZE mazda head ... not to sure if we get the "Opel" 20XE around here ..note however that the local market "Holden" 4 cyl s are rebadged Opel cars

[GoLfMan]

that would prob be the holden astra engine yes>?

[el_foolio]

yep they are, we have a holden barina, thats rebadged as opel, it has an opel engine, at least its european

[Golf Loon]

Was searching for extractor info, but this is a good post about 16v head porting.

[gtimk5]

This is very interesting stuff on the 16v heads indeed but the topic started out on extractors for an 8v. Maybe we would all benefit from a new topic on modifying 16v motors and tuning such. I am very interested and you guys obviously know your stuff and have a lot of experience with them.
(Me???) I know how to snap exhaust cams on them!!!!