Ported exhaust manifold or 4branch?

Which would be best for my engine? finding it hard to find a 4branch RHD with cat flange thats not for a tall block, should i get the standard manifold ported?

If yes, who can do it?

I beleive JMR has had good results from porting his exhaust manifold on his 16v G60. I'd give him a call

Otherwise, do Dubpower do an exhaust mani for the 16v?

A ported cast mani is capable of good results providing it is done correctly. A correctly fabricated 4-2-1 will however yield more torque and better top end power. As to whether the difference is noticeable that's another story. As the exhaust mani may not be the restriction in the chain of events.

Remember an engine and it's components have to gel together.

for example no point putting on a better induction setup if you can't get rid of the extra air you are putting into the engine.
No point putting a 4 branch on if the real restriction is the rest of the exhaust system.
etc...

I have a complete 2.5inch bore system with 2 boxes,no cat, And a BBM screw charger wacking in 18psi of boost so just thought the mani would be the restriction if any.

Exhaust ports on the head flow less than the manifold in standard form so if no headwork has been done you'll benefit from running a flapper wheel down the mani to smooth of some of the casting (especially on the inside radius of the bends) on the initial transition into the manifold from the head but that's about all that will be necessary. If the head has been reworked then the runners on the mani will need to be altered accordingly.

I could only make 1.1 bar on the 50mm pulley so it also does sound like there is a restriction in the head itself and mine was the 8 valve.

Out of interest, and I know it's completely off topic, but would I be better flowing my stock vr manifold to my head (ported and polished head) than buying a raceland 6 branch?

Reading between the lines i would say you would be better off with the 6 branch if its designed properly and then if you wanted to port match that too for a proper free flowing system.

Toad wrote:Out of interest, and I know it's completely off topic, but would I be better flowing my stock vr manifold to my head (ported and polished head) than buying a raceland 6 branch?

I think the Dubpower 6-branch would be better...

junkie wrote:Reading between the lines i would say you would be better off with the 6 branch if its designed properly and then if you wanted to port match that too for a proper free flowing system.

yep

JNLRacing wrote:

junkie wrote:Reading between the lines i would say you would be better off with the 6 branch if its designed properly and then if you wanted to port match that too for a proper free flowing system.

yep

Hust make the 10% commission payments to the usual please

Head is standard 16v head, boost gauge only ever shows max 9psi with 55mm pulley

JNLRacing wrote:

junkie wrote:Reading between the lines i would say you would be better off with the 6 branch if its designed properly and then if you wanted to port match that too for a proper free flowing system.

yep

I've always read and believed that a step from the head exhaust ports to the exhaust manifold was beneficial to exhaust gas flow and also helped to prevent reversion of the gasses.

Yes and no a step needs to be interpreted correctly. For example you can put a step at the first harmonic (tuned length) and that will improve midrange torque. Again putting a stepfrom the head to the manifold will help prevent flow reversion and help flow. However this is where the step needs to be carefully interpreted as what it means is a step up in internal diameter. i.e the id of the exhaust mani should be greater than the exhaust port. This does not mean create a ledge that causes turbulance. Either on the very last couple of mm of the exhaust port or the first couple of mm of the exhaust mani it can be beneficial to match the two for smooth transition of airflow providing the id of the mani is greater than the exhaust port.
Similar prinicpal to a 2 stroke exhaust. The sudden expansion in the exhausthelps scavenge air out the cylinder but it's a gradual transition not an accumulation of stepped cylinders.

OK I see! After the New Year I'll be sending over a head to G-Werks for you to do one of your special porting jobs to it, I run a G-Werks exhaust manifold will you be able to perform the above port match without my exhaust manifold? Or does the above not apply to Supercharged motors or the gwerks mani as the runners are so big there will be a large step anyway within the manifold itself between the flange and the primary runners.

Ive just obtained a mk3 2l 8V 4branch, my mate has given it to me but im waiting for him to drop it over so i dont know if ist 4-1 or 4-2-1.
Il weld it to a 16v head flange and measure it up on the car first

ctwg60 If you're going stage3 or above it wont make a difference as the port is opened up as far as it can go which is the gasket. Any runner smaller than that ends up as a restriction anyway.

So for a DIYist such as myself, if I check the head against the exhaust manifold gasket (I think my new head is opened up to the same size as the gasket) then use the gasket as a template for opening the manifold up to match the size and shape whilst maintaining a smooth transition between the pipe and the flange, I should be ok?

If I understand correctly, you'd want to have the manifold with a larger internal diameter than the head, but not with a step change, but rather a smooth, but rapid increase in internal diameter?

With turbos in particular, I don't see a gain in gasket matching the head ports since the pistons will be pushing the exhaust gases straight into a turbine scroll and wheel, which is a massive restriction.
Keeping the exhaust flow from turbine to tail pipe as restriction free as possibe is where the exhaust gains come from.....i.e. big bore and straight through silencer/s.

The only time I've seen BIG gains from manifold / front pipe improvements on a turbo engine is the Subaru lump. They fitted VERY restricted down pipes (30% blocked off!) and fitting a full bore downpipe saw up to 50hp with a remap.

It'll work with Superchargers though since the boost is already made and burned before leaving the head ports.

On a personal level I don't like taking metal out of heads anyway. It's a heatsink as much as it is the air / exhaust router, so I don't like to compromise heat dissipation. Plus I like a little restriction in the intake side of things to keep gas speeds up at low rpms.

kevhaywire wrote:Plus I like a little restriction in the intake side of things to keep gas speeds up at low rpms.

That's what I'm a little concerned about. But I hope that the porting work will improve throttle response, hopefully negating the reducton in torque low down, plus it'll have the schimmel cams, and a shrick manifold.

Still not sure as to whether I should guff around with it or not.

I suppose you could guff around with a spare head and try it? Only an afternoon's work swapping heads

Personally I'd leave the head, perhaps just gasket match to remove any steps.

To improve torque and power together, you need to burn more air / fuel, so that means bigger pistons and valves, plus cams You'll get noticable gains that way. Hogging out the intake ports alone won't really achieve much tbh and on a cross flow head like the VRs, which feels kind of lethargic low down anyway, you'd be making matters worse

kevhaywire wrote:I suppose you could guff around with a spare head and try it? Only an afternoon's work swapping heads

Ok i dont know what kind of "head swapping" your doing but it takes a lot longer than that, 6 months for me and i have less valves.

I just need a set of standard valves, springs etc and I can have the new head cleaned up and rebuilt. Then I could swap it around I suppose. Dunno If I can really afford a set of head bolts for an experiment though.

Would be an interesting day, try to find a local rolling road and actually find out what differences there are.

Toad wrote:I just need a set of standard valves, springs etc and I can have the new head cleaned up and rebuilt. Then I could swap it around I suppose. Dunno If I can really afford a set of head bolts for an experiment though.

Would be an interesting day, try to find a local rolling road and actually find out what differences there are.

Why not get some ARP head bolts Tom, then you could swap the head over as many times as you liked