Okay, I have been searching, researching, and podering porting on the NA S4 6PI. Now, from what I can gather, birdging is absolutely pointless as you would be losing power since the intake timing closes extremely late as it is, but advantages can be made from street porting and polishing. Check.

My question is, where can I find a good streetport template for the irons and what sort of power/efficiency (fuel burned > power used) gain could I expect to see? I have watched Aaroncake's porting video on his cosmo, but those were GSL-SE irons... I am confident in myself being able to port well, but I just need a little guidance as to what template and tools I should use, and all of this AFTER I know if it is worth it or not to port the intake. Porting the exhaust on the housings would be dumb because of the diffusers in the port itself...

Thanks guys!

 

Mazdatrix has what I consider to be the only reasonable 6 port porting template. It is far less aggressive than the others, but then the reduction in low end and midrange you get with the Mazdatrix template is inconsequential. Those "monster" street ports you see on 6 port engines just make the car slower below 7000 RPM.

If you are porting the intake, you really need to port the exhaust as well. the diffusers aren't that big of a deal. You can sort of port around them, or just grind them out.

 

That's what I was afraid of.. I didn't want to sacrifice the midrange for top end as much as I wanted to smooth the transitions and have a little more power available. However, even though the buzzer comes on at 7k, can't you rev to 8 and be okay? I also want to replace the sleeves with atkins sleeves, but only if I'm going to notice the power.

 

Wait, I think I misunderstood what you meant, so youre saying the mazdatrix template will increase power but sacrifice anything below 7k? Or it will increase power and generally keep the power of the midrange

 

i have dealt with the diffusers and they are in fact a huge restriction on the engines. after tuning an S5 for many hours we couldn't get much more power out of the engine because it simply couldn't flow anymore even with radical timing, split and leaner AFRs. we went as far as wiring open all the ports to be sure but no more gains could be made even with a fair amount removed around the port wings and moderate intake iron porting.

he swapped that engine with another that had turbo sleeves installed, the dyno instantly went up almost 20 horsepower with the same aggressive tune which had to be backed off some.

there isn't much gains from having the diffusers in the exhaust, pitch them and you'll instantly notice improvements.

i did however notice that the powerband on the replacement engine without the diffusers had a shorter power band that peaked at ~7500 RPMs where my engine peaked nearly 1k higher at 8400 RPMs. but the cause of that i imagine was that the intake was not ported on the replacement engine just the exhaust sleeves were replaced, i do not even think the exhausts were ported. if the replacement non diffused exhaust engine could maintain producing power up to 8500 it would be very close to 200 wheel horsepower, there was simply no way we could hope to even get close to that figure with the diffused exhaust ports.

with these engines it is all about how easily air can get in and out of the engine, having an exhaust blocker inhibits the upper power range, while it makes the car more street friendly it certainly will hinder true performance by a noticable degree.

so in summary i'd have to say that to get the most out of an n/a you need to focus on opening the exhaust quite a bit(without retarding the port timing, only advance it slightly) and only slightly rework the intake to increase it's velocity, the volume on the n/a is not an issue as the ports are already quite massive.

this example engine has had many configurations done to verify that the most was being done in order to make power, it has had 3 exhaust systems on it, several intakes including a CAI box, no filter, stock ECU and Rtek 2.1 with hours of on and off dyno tuning.

i used to think it was ok to leave the wings in and port around them, but after dealing with the example car i now know that i was taking money for a service that gained very little aside from broadening the RPM range of the engine but making very little more power.

 

You can rev to 8000 RPM all day. However the manifolds themselves start to become a restriction around there. Make some huge ports that want to make power above 7K and you'll end up having to replace the intake manifold.

Mazdatrix says that their template is good for a "20%" power increase, without killing bottom end and midrange. They run very conservative timings as compared to most massive street ports and don't enlarge the ports much, to keep velocity up. As compared to many NA street ports where people just hog the ports out as much as they can.

Here's the thing though: You'll make more power with a properly tuned standalone than you will with a ported NA on the stock ECU.

By "not a big deal" I meant "not a big deal to grind away".

 

ah ok, just wanted to be sure.

easiest method i have found to eliminate them versus swap to turbo sleeves is to cut straight across the end and rock the big chunk off the opening. then take long needle nose and bend the wings several times until they snap off. you can then go over what remains with a grinder, taking it all out just with the grinder takes quite some time.

 

Thanks for all the feedback guys. So best bet would be the Atikins sleeves, mazdatrix port templates, RB 2-1 header, standalone(?), and grind the diffusers out? It will be daily driven so noise is almost an issue, but i do still have the silencer for the exhaust should it be "too loud" for my neighborhood. *the disadvantage of a gated neighborhood*

 

if it's a RB or greddy PE catback you should be ok, if it's a generic single 3" it will be annoyingly too loud for the burbs as a daily. duals sound better and quiet the exhaust better, unfortunately most aftermarkets are single exhaust.

 

Yea, I've got a corksport stock cat flange to 80mm tip. I'll try and do a trade with someone plus a little extra for a RB dual. The only reason I still have cats is because I have to test emissions in my county and have nobody around me to register out of county. It's a twin cat system w/ air pickup instead of the Oem twin pre cat to main cat w/ air pickup