Don't port your 16g.

[dsm-onster]

Here's a few pics of how I avoid hours of porting yet still eliminate that terrible "down-step" going from a 2g manifold to any 7cm^2 turbine housing (16g, 18g, 20g). It involves a piece of 2" galvanized pipe from Lowe's or home depot.

A 2g manifold has a step in it. The outermost inside diameter is about the same size as the innermost inside diameter of a 7cm^2 turbine housing. You can port, which will open up the collector volume even more. I consider the inlet of the turbine housing part of the collector. Having a small runner open into a larger collector volume slows velocity. Instead, you can use an evo3 manifold and actually use the sealing ring. Or you can do this and keep the 2g manifold. The step in the 2g manifold does not create nearly the turbulence since you're going from a smaller diameter to a larger one. One little thing to note is that many ebay manifolds have a outlet port diameter about equal to the outermost diameter of the 2g manifold step. And there is no step . Add the below to this, and you have a great transition that sacrifices as little velocity as possible to get the gases into the turbine housing.

2" galvanized pipe from the hardware store is pretty much a perfect fit into the step footprint of the 7cm^2 turbine housing.

Simply scribe out the height necessary for a piece of pipe to set flush in the housing. ****EDIT: Put the gasket flat on the turbine housing when you're doing this so that you will accomodate the difference in the gasket thickness. This will give you the best transition and seal the exhaust gases from the gasket, taking some stress off the gasket.

Now cut it.

Fits nice, but be sure to clean up the cut.

Now you have saved a few hours porting that turbulent down-step with a smooth transition from to 2g outer diameter and haven't opened up your collector volume any more.

As I mentioned and re-mentioned for emphasis, the ebay manifold we are using doesn't even have a step in it's outlet. Just a diameter equal to the outer diameter of the 2g manifold. This makes for a very nice transition. No hours of porting. And the manifold has held up for about a year before this "re"-build with a terrible knocking tune (lots of exhaust heat from timing retard).

Smooth transition. Good "angle of attack" to the turbine housing. ROUND ports. Equalish length (good for preventing back flow during overlap). All the main bullets for a fast spooling hot-side

 

[Mr Peepers]

I remember you telling me about this a while back! I also did something similar(I'd have pics but I don't have a camera anymore).

I used some 1/8-3/16 thick or so sheet metal, cut a strip slightly wider than the step is deep, then bent it into a circle and "file to fit" the ends so it was snug in the step. I decked it with a file to make it perfectly flush with the flange. I couldn't find any pipe that fit how I wanted it to I didn't think to look at threaded pipe.

I didn't like opening the turbine housing more than it has to be, or porting the manifold farther than the step and remembered you saying a ported 2g mani is the same diameter as the inside of the step on a 7cm^2 turbine housing

 

[dsm-onster]

/\ /\ /\ /\That's a great idea too. The tricky part is fabbing up a piece that will fit with the evo3 manifold, since it needs to go above the plane of the turbine housing inlet for the seal since the evo3 manifold is designed for the 7cm^2 housing, of course. In this case, I think it would be worth it to hunt down a sealing ring.

It did well with my small 16g. . . Which now my brother has inherited. It spooled faster than with no piece inserted with a 2g manifold, and faster than no piece inserted with the evo3 manifold. . . I'd say about 100-200rpms sooner. Hey, every little bit helps.

Which is what he's looking for. We sat down and talked about his build and what he's looking for. We have a SMIM and a tubular manifold. And he's really into a autoX car. He wants great traction, instant hit. But still a red line that isn't dead. So we opted to keep the 1g head\intakemanifold with the 6-bolt but run the equal length header. He had a td05h 18g that needs a rebuild. But for his goal, which is 13s all day ling and the potential for a 12 if he pushes it, the small 16g fits the bill better. It spools SO very fast for it's flow with respect to the other td05h turbos. It has 38 lb/min in it. We opted for the stock 1g manifold. It is a great upgrade to the manifold that comes on the car. It has shorter runners than the 2g manifold with a larger average radius to counter. The diameter being larger actually helps low end (see helmholtz theory) an d the larger plenum gives a larger mass to vibrate, slowing the period and helping low end (also proven by helmholtz). So the 1g manifold accept more flow because it is larger, and it's plenum is harder to 'exhaust', which is the true reason why larger plenums still help up top. Yet it doesn't lose that mid range resonance for which all stock manifolds are designed. . . It fits like a glove to the small 16g with a stock stroke 4g63. . . I really think the small 16g is the turbo that the 1g SHOULD have had. It was about 5 years later that it was developed.

The tubular helps spool because it keeps exhaust gases going in the right direction: pushing the turbine wheel. It also helps overall VE, because it keeps exhaust gases from filling cylinders that are in overlap. Better VE through out the rpm range helps spool too. And it helps flow up top as well of course, helping the motor try to 'exhaust' that larger 1g plenum.

He's running in blowthrough, which will increase spool becasue of the lower resistance to the flow intake. And also increases peak flow because the resistance isn't there to create a pressure drop: this is IDENTICAL to speed density with respect to flow efficiency. I was very hesitant to do this, because of the headaches I've had tuning a maft in blowthrough with my car. I REALLY learned how to diagnose a log. But I thought that with his car, we would be limited using an obdII live data scanner. But apparently, there is a CAN bus on the 2g cars, which means the ideal Dash Hawk can be used. The dash hawk shows live data and logs graph to the computer at a fast rate. Which is imperative to see if there is knock since a 2g ECU doesn't spit out a knock sum. The Dash Hawk also spits out an accurate 0-60 time and a1/4 mile time and speed. Since, I'm 99% sure the Dash Hawk works, I'll be better equipped to tackle the juggling act that is the maft in blowthrough.

I've also routed the intake pipe outside the engine bay. It will guarantee cold air since the filter element is now in the wheel well. Colder intake temps help spool speed, from my experience. And of course peak flow. The piping is consistant in diameter with only 3 sweeping 90s: up, over, and out the bay. I don't want to lose the gains from no maf to bad intake design.

I really think this car is going to do well. I've run a setup VERY similar to this for a few years. And it was a little "seasonal", but his BOV is mounted out side the engine bay in the bumper skin . It should be plenty of fun.

 

[Mr Peepers]

Finally got a pic, 3 months later...