NoPistons!

iTrader: (3)

I know in a piston engine that's n/a, some backpressure is good. 2.5" piping has always been my rule of thumb n/a and 3" for turbo. However, rotary exhaust pulses are ALOT stronger than a piston engine. I experienced this first hand yesterday starting my car with the y pipe off. I could feel the idle exhaust pulses from 3 feet behind the car! Would a 3" full exhaust be a smart thing to build for midrange to top end power or would i be better off making a catback or doing a full 2.5" system? My system will either use a single hks super dragger or hks high power muffler with stainless v-band piping. I wanted to tig it but my buddy jeff lives quite a ways away. My mom's bf has a shop and a mig welder so i'll just get some stainless wire and have at it.

If i choose not to sell my non running sixport, i'm going to port it.

I've been told by people outside the forum that build rotaries that a bridge port will be too agressive for street driving and gas mileage will be terrible compared to a stock port. They say the same about p-ports as well.

If this is indeed true then i guess my quest for a bump in power is a large street port, yes?

Any power estimates for these two mods? I'm not looking to set the world on fire, i just want some more power and torque.

diabolical1

iTrader: (3)

streetport. definitely streetport.

as far as the exhaust issue is concerned, since you're going with a single exit, the diameter is totally up to you. i'm sure you'll hear the bigger is best argument, but honestly i doubt if you'll notice any significant torque [which is what matters on the street] difference between 2.5 and 3 on a streetport. however, you will notice a sound difference. so again, it's your choice.

Falken

I'm not going to say for sure because I'm no expert, but I've been told that this is a very common misconception and you want a little backpressure as possible.

rotarygod

iTrader: (1)

^Correct. You NEVER want backpressure. It is always a bad thing and never helps at all ever! What you do want is exhaust velocity though and in a perfect world your exhaust at peak power would be right at the threshold of no backpressure vs having some. This would keep velocity up as high as it could be and still not suffer the negative effects of backpressure. Of course backpressure is rpm dependent as it's all based on flow. You could have a setup that has no backpressure at 2000 rpm but tons of it at 7000 rpm. This would yield great low end but not because of added backpressure. It would have good exhaust velocity down low which would mean better scavenging and hence better power down low. Low backpressure at higher rpms mean that you also don't have any down low but you also lose much of the exhaust velocity through a larger pipe down there. This translates into less scavenging and hence less low end power.

Rotary pulses are stronger for the sheer fact that the peripheral exhaust ports open very fast by comparison to a piston engine's exhaust valve or even a side exhaust port Renesis.

As a general rule the more aggressive your porting, the worse your mileage will be and the worse the vehicle will drive at low loads. While a bridgeport or peripheral port engine may make great low end power, they need to have the load levels up meaning more throttle to do so. At light loads such as gentle driving or cruising on the freeway, they aren't as happy. Remember this sentence as it applies to nearly everything. The more you want, the more you compromise in some way once you get it. This could mean more porting means drivability sacrifices or it could mean a turbo system that drives wonderfully but the compromise was the price you paid to get it. You get the point. Staying naturally aspirated and making power means you'll pay quite a bit for the amount of power you are trying to get. The more you try to get the more and more you'll pay. There comes a certain point where it's just cheaper to keep a stock motor but add a light amount of boost. The problem is that no one can keep boost low for long and eventually they'll turn it up more and more. Power is addictive. With an n/a, you'll hit the power brick wall pretty early by comparison to forced induction.

If you would be happy with 200 hp or so max and still need good drivability/livability on the street, I'd do a streetported 6 port engine. Don't go to a 3" exhaust. You don't need it. 2-1/2" is fine. Don't even port it any more aggressive than a Racing Beat template. They are mild in some people's opinions but I've never seen anyone go larger and actually make more power. It doesn't happen as it's not needed. If you want more power than this, I'd really strongly consider a small turbo. At this point, leave the engine stock as stock ports are easily capable of 400+ hp and just turbo it. You wouldn't even need much boost. Stay low at 6-8 psi. You wouldn't really need much to accomplish this safely. If you want more you'd really need to start looking at other options for fuel and ignition control but low boost could be done pretty easily with nothing more than an additional injector controller or a rising rate fuel pressure regulator. This may scare many people but it's only applicable at low boost levels. More requires much more attention. This is a fairly cheap and easy option that would need minimal work or fabrication. It would also leave the door wide open for future upgrades for more power.

This is all just my opinion though. Others may disagree.

ultimatejay

iTrader: (1)

^ +1

j9fd3s

iTrader: (3)

nope that all makes a lot of sense.

from a tuning perspective, its enough of a challenge to truly max out even a stock port engine, let alone some weird giant port engine. the average setup i see is pretty crappy, and the car ends up slow and unreliable. they always think a bigger port will fix it, when all it really does is add another set of problems on top of the ones you already had.

to the turbo route, with an FC the rtek ecu's have enough tuning window to do a small turbo.

HeyITZthatFC

I'm looking for a good (single)exhaust on my NA fc right now actually, what do you recommend?

justinpace

hmm well, theres corksport, or i was thinkin u could buy a universal muffler from racing beat have custom pipe from header to the muffler and also have them weld in a nice tip becuase the universal one has no tip, would be a good price i think if u have a good shop