Kentetsu

Hey guys. This spring I will be rebuilding and porting my spare motor. Next year I'll try to add a turbo to it. So, what is the best porting option for someone who later plans on going turbo?

Directfreak

iTrader: (2)

Streetport.

Kentetsu

Just the man I was hoping to hear from. lol. But, are we talking mild or major streetport? From what I've read, it sounds like you can be pretty aggressive on the intakes but have to leave the exhuast ports pretty much as they are. Correct?

REVHED

That's incorrect. You should give the exhaust ports just as much attention as the intake.

The level of porting depends on the application. If you're going for a big turbo and a serious power figure nothing beats a bridgeport. Most of the time a streetport will be enough though.

Kentetsu

I believe that this issue they were discussing in refference to the exhaust ports was "boost creep". If that helps... Thanks. Not looking for 800 horse or anything, 300 would do me just fine.

razorback

when i build my 12a motor ill be looking at a streetport, i never knew how small the 12a exhaust ports are til i saw them the other day. i would go with half bridge, but i dont want to worry about other mods. and a street port is all id need now.

REVHED

I think you'll find most people talk about restricting the actual exhaust system to reduce boost creep. Regardless, the cause of boost creep is a poorly flowing wasegate system. Restricting the exhaust will only rob power instead of fixing the root of the problem.

razorback

people port wastegates to reduce boost creep, i did it on my old t2 turbo and my friends fd twins.

z-beater

Personally if you are looking for 300rwhp I would do a small street port. What kind of psi are you planning on running?

You can always just get a little bit larger of a turbo to compensate for smaller ports. There are also downsides of this as well.

Small streetport allows reliability while still adding a little hp increase.

WackyRotary

I have tried a couple variations of streetporting and a stockport engine. My experience only(not backed up) for the s4 turbo I have- with matched twin scrolls and the dynamic flapper removed, and finally a ported wastegate- found that larger exhuast ports is better then a slightly ported exhuast ports. BUT- when it came to low end response, the stockport wins, but obviously suffered at high revs.

diabolical1

iTrader: (3)

if you know that ALL you want is ~300 WHP, then i wouldn't go crazy with the port-work. as stated before, a mild streetport (intake and exhaust) will get the job done. increase your oil pressure, get a cooling system that's more than merely capable and address fuel supply - and you should have a solid, reliable setup.

again, just to reiterate, boost creep is mostly a wastegate issue.

Kentetsu

Okay, thinking more on this I remember it a little better. Larger exhaust ports flow better but have lower velocity, which means longer spool up time for the turbo (lag).

I'd like to get as much power as I can with the porting so I can enjoy it this year, but without messing up the turbo option for next year. Plans for now are to get some track time at a local road course, and maybe some autoX.

Also, I don't want to have to get to 4,000 rpms before I see any HP. So I figure a BP or 1/2 Bridge might be more than I'm looking for.

Thanks a bunch for the input guys!

diabolical1

iTrader: (3)

obviously, the choice is ultimately yours, but all i'll say is this: take some caution when porting exhausts for a turbo application. you can actually start to hurt N/A performance.

Directfreak

iTrader: (2)

Listen to Revhead and Diabolical1.

I would add, that if you only want 300hp on a TII engine, then don't port it at all. I have seen 687rwhp Streetported engines, so a bridge isn't necessary.

Bridge-Turbos are nice when running large boost (25+). Anything less and it will be a lazy car.

Kentetsu

Thanks DF. I still want to do some porting while I have it apart, so I can get some gains for this summer. I just want to make sure that I can still turbo it next year and get really nice results... Your videos have inspired me.

84gsNC

Somone correct me if im wrong, but porting the exhaust side wont cause lag, it should spool faster. My next turbo 12a motor, I was going w/ a large sp on exhaust and prolly a medium on the intake. What kinda turbo were you thinking of using?

Kentetsu

Making the exhaust ports larger will allow more airflow, but at lower velocities than stock. It is the lower velocity that adds to the turbo lag from what I've read.

I have no idea what turbo I'll be getting, that will come next year (unless I win the Lottery before then).

slayerx7

iTrader: (4)

Im in a similiar prediciment. I was hoping for 300rwhp, but was told that with a 60-1 Turbo, (turbonetics seem to be the best for this Ive seen so far) and a good extend port, 450 hp should be reachable with about 20lbs boost. So 10-15lbs boost should hit the target power range nicely. I dont know what the lag will feel like, but was told that with a proper turbo, you should have power on tap from like 2500-3000rpm on up.

However, I should wait till later before even thinking about a turbo, as Ive got a holley to put on it, and my SDJ header should be coming in the mail soon. These together on a stockport, Im hoping for 130HP 150 if it can possibly be squeezed. Drive it till the oil leaks get REALLY bad, then thatll be a good time to take it apart. I have my eye set on an extend port, but with the lag issue, maybe be a little more reserved with the exhaust porting, cause these rotories hurt for low end torque as is.

RXDad

iTrader: (2)

Way back in ancient history when we were playing with Corvair turbos, the thinking then was to avoid lots of overlap on the cam. We thought that with high intake pressure and long overlap between intake and exhaust, lots of unburnt fuel would be pushed into the turbo, causing cooling of the exhaust, and not much extra horsepower for lots more fuel.

Is this still the thinking or with the newer turbine materials and water cooled turbos, burn some fuel in the exhaust manifold before the turbo? If you want to avoid lots of overlap, would the approach be to avoid early opening of the intake (bridgeport) and port the exhaust to open earlier?

RXDad

REVHED

Bridge-ports and turbos are fine. You just need to use a big turbine housing to minimize backpressure. Restrictive exhausts and ported engines don't mix.

diabolical1

iTrader: (3)

you've got it half right ... if you get a chance, look at the exhaust ports that many of the Gen II and Gen III guys use for their high output, large turbo setups. they are set to open earlier than comparably sized ports on an N/A motor.

as Revhed said, bridges and turbos work together just fine.

Kentetsu

Yeah, a bridgey would be great if this was going to be mostly a track or weekender car. And I'm not too finicky when it comes to drivability either, if it runs I can drive it.

The only thing is, I don't want to have to wait until 4,000 before I get into the power band (tends to draw cops). It would be different if I didn't live in the city.

Autocross, road course, and a few fast runs to work each week is what I'm looking at. Long term goal is to humiliate my buddy (spoiled rich bstrd, but a great guy) by thrashing his STI on the track... I figure he's got 300 hp, but his car weighs nearly twice as much as mine, so as long as I can get over 230 hp or so it should be doable... I can't wait!

Rotary7s

good topic here.

Im shooting for 400-500 rwhp
My first plans was to do street port,then I thought about Soul Assasins set up,and I think he was half bridge,around 620?

So im tring to find dyno sheets,or just hear what people think about bridge on turbo,will it totally kill low end power under 2k?

trochoid

iTrader: (6)

Check out BDC's bridgeport turbos, here and over on NP. 2nd gen section here and Engine Building and Porting there. He has made believers of quite a few people, does beautiful port work too.