Evo III 16g... Ported or Unported??

[spoolin_upTSi]

Ok... I have researched this on and off for weeks, and have asked in threads already but can't seem to get a solid answer. I seem to keep getting pulled back and forth.

First off I will say I am looking to make between 300 and 350 whp on my new setup. This car will be used for street, track, and auto-x racing. I chose the Evo III 16g for the quick spool up that i will need on the auto-x course.

After Christmas my mods are going to look exactly like this:

Evo III 16g
660 Denso injectors
FMIC and hard intercooler piping
Walbro 190lph fuel pump
SAFC-2
3 inch turbo-back exhaust with high-flow cat welded in
Some type of datalogger
Greddy Type S BOV
Manual Boost controller
Aftermarket boost gauge
HKS Turbo Timer
ACT 2100 clutch

I think that's everything.

My question is:

With only the mods listed above, would i be better off getting my turbo unmolested (unported with standard flapper), ported with standard flapper, or ported with enlarged flapper? I keep getting swayed back and forth because different people say different things. I'd like to get some answers all in one place so I can analyze them easier. Remember that I will be using this for street, track, and auto-x.

I appreciate the help guys!!!

 

[kenamond]

I started porting my Big 16g tonight. I was concerned about the wastegate area. I ported it about as much as you did and I saw little cracks leading to the wastegate flapper. Sound I be concerned. Should I weld it and grind a little off? I think Im done with porting that area.

Honestly, I'm not sure. From what I've read, cracks around the WG passage are very common, and many folks ignore them. I'm not sure if welding them will do the trick in the long term unless you had the whole housing heat treated, because the added stress from welding might just initiate cracks around the welds...book stuff for what it's worth (when you weld, the material melts (duh), but when it cools, it contracts and stresses the material at the edges of the weld. But heat treating it brings the temps up so that the material "almost melts" and the stresses are relieved).

Part of me says just go for it and hope the cracks don't grow, but the other half says, "What if this guy's housing cracks just the right (wrong?) way and drops a fragment through the turbine wheel and destroys it and he blames me?" The first half of me is winning, though. So considering that, I'd say go for it, but if those cracks grow, you could develop pre-turbo exhaust leaks. Or a couple of cracks could merge and form the "perfect storm", and let a big chunk of metal come off and run through the turbine wheel. You've been warned.

 

[pj91gsx]

ok. well the cracks are very tiny. This is a big 16g off of my jdm swap galant engine. So it does have very little miles. Before I knew what I was doing, I bought the motor put it in and left out a vacuum line off of the wastegate. The 16g boosted to 35 lbs. I thought this was a lot of fun. . But then I relized I probably had done a lot of damage to my engine. So now for a peace of mind I am rebuilding my engine because of the boost problems, the motor was skipping, and there was gas in the oil from no spark. The bearings were more scored in my jdm swap with about 200 miles that I put on it than my brothers 167,000 mile motor. The block was scored as well.

 

[DSMunknown]

I don't completely agree with porting, nor do I like it very much. Unported IMHO, regardless of what Bruce and Mack recommend. I'm probably one of the few who will say that, though.

 

[pj91gsx]

I wonder if I port it farther if the cracks would disappear. Im not going to try it though.

 

[DSMunknown]

I wonder if I port it farther if the cracks would disappear. Im not going to try it though.

Sure, they'll go away... until it goes through heat cycles. Making the walls thinner when you already have issues with cracking will definitely increase this problem.

 

[pj91gsx]

thanks for the encouragement. jk. Ill look into welding it and asking around before I put it back on. I wonder why it crack there though. Maybe its the hotest part of the turbo. Or it changes from hot and cold very fast.

 

[CTP]

Destroying turbine efficiency in the name of preventing boost creep FTL. Internal wastegate passages are shrouded for a reason. Everyone thinks that boring out and unshrouding the wastegate passage prevents creep by letting more exhaust flow out the wastegate. News flash, MHI turbos creep because the flapper barely opens 45*. All the porting in the world isn't going to make the wastegate flow any more when the opening of the flapper is the restricting point. "But wait," you say, "porting is proven to prevent creep." Sure it does, it prevents creep by ruining turbine efficiency. Thus making it take a higher pressure differential to make the same boost which in turn stops your boost creep. Yay! It also kills power and hurts spool. Yay! But no boost creep. Yay!

 

[Mr Peepers]

Destroying turbine efficiency in the name of preventing boost creep FTL. Internal wastegate passages are shrouded for a reason. Everyone thinks that boring out and unshrouding the wastegate passage prevents creep by letting more exhaust flow out the wastegate. News flash, MHI turbos creep because the flapper barely opens 45*. All the porting in the world isn't going to make the wastegate flow any more when the opening of the flapper is the restricting point. "But wait," you say, "porting is proven to prevent creep." Sure it does, it prevents creep by ruining turbine efficiency. Thus making it take a higher pressure differential to make the same boost which in turn stops your boost creep. Yay! It also kills power and hurts spool. Yay! But no boost creep. Yay!

You're right, it does reduce turbine efficiency, but to what degree? I highly doubt that it stops creep solely by reducing turbine efficiency. There would be a very noticeable drop in power if that were the case. Think about this, adding restriction such as a stock exhaust will often stop creep by affecting the pressure differential. Now compare a free flowing exhaust with a boost creep ported turbine housing to a stock exhaust with no porting. Who wants to bet the free flowing exhaust with the boost creep ported turbine housing will flow more at the same psi? IMHO it's a much better alternative. A good boost creep port will sacrifice the least turbulence possible, but there are ways to obviously overdo it.

The stock WGA opens about 30* and is a big factor in boost creep, I agree as well, but in the cases where its creeping well over 20 psi -even having the flapper open all the way often won't get it to stay below 15 psi. It works both ways, and there are always exceptions, I'm just stating what I've seen personally.

I am however interested in how much is too much as far as directing the exhaust into the wastegate passage, but saying it's not worth it is a little overboard.

 

[CTP]

You're right, it does reduce turbine efficiency, but to what degree? I highly doubt that it stops creep solely by reducing turbine efficiency. There would be a very noticeable drop in power if that were the case. Think about this, adding restriction such as a stock exhaust will often stop creep by affecting the pressure differential. Now compare a free flowing exhaust with a boost creep ported turbine housing to a stock exhaust with no porting. Who wants to bet the free flowing exhaust with the boost creep ported turbine housing will flow more at the same psi? IMHO it's a much better alternative. A good boost creep port will sacrifice the least turbulence possible, but there are ways to obviously overdo it.

The stock WGA opens about 30* and is a big factor in boost creep, I agree as well, but in the cases where its creeping well over 20 psi -even having the flapper open all the way often won't get it to stay below 15 psi. It works both ways, and there are always exceptions, I'm just stating what I've seen personally.

I am however interested in how much is too much as far as directing the exhaust into the wastegate passage, but saying it's not worth it is a little overboard.

You're absolutely right. A ported turbine housing will cost you less power than running a more restrictive exhaust. That one is a no brainer. However, IMO the alternative would not be a more restrictive exhaust (because that's ridiculous), but a proper external wastegate.

There would be an easy way to test whether the flapper is as much of a restriction as I suggested it was, simply unhook the actuator arm and wire the flapper open. Unfortunately, I never bothered to try that on my 16g, but maybe you could give it a try on your car (if you have an internally gated MHI turbo). If the boost no longer creeps or creeps very little, the flapper is clearly the entire (or vast majority) of the restriction and therefore porting does in fact stop creep by killing efficiency. However, if the boost still does creep, then you obviously have an issue with the passage itself and then port work does in fact reduce creep by improving wastegate flow. Simple test, easy to read results.

Also, keep in mind that just a single digit percent change in turbine efficiency has very large and noticable effect on turbine performance and P/R requirements. It wouldn't take much to hurt the efficiency enough to keep the boost lower with the same P/R.

 

[kenamond]

There would be an easy way to test whether the flapper is as much of a restriction as I suggested it was, simply unhook the actuator arm and wire the flapper open. Unfortunately, I never bothered to try that on my 16g, but maybe you could give it a try on your car (if you have an internally gated MHI turbo). If the boost no longer creeps or creeps very little, the flapper is clearly the entire (or vast majority) of the restriction and therefore porting does in fact stop creep by killing efficiency. However, if the boost still does creep, then you obviously have an issue with the passage itself and then port work does in fact reduce creep by improving wastegate flow. Simple test, easy to read results.

The "Peepers mod" that Mr Peepers does extends WGA throw without compromising preload on the flapper, but everyone is given the above advice as a prerequisite so that they can determine if it will even help them.

 

[Mr Peepers]

I see what you're saying CTP about the turbine efficiency. Not to discredit your theory, it's something I've been curious about for a while too, but I haven't seen any noticeable flow difference in actual use between a turbine housing ported for boost creep and a plain jane ported one(step removed, which is still questionable, I saw your post on another thread and agree to a point depending on the application). Back to back testing would be interesting, I like to keep an open mind.

Personally, I can't justify an external setup for a turbo such as a 16g if it's just to cure boost creep. Most people wouldn't want to spend the time messing with an internal gate to keep it from blowing open at higher boost pressures or even from creeping, but I like to work with what I've got

 

[kmoore]

Here's a thread that I started a while back. It might help you out. I had some similiar questions that you had:

http://www.dsmtuners.com/forums/turbo-system-tech/275021-oldman-could-you-grade-my-porting.html

 

[Calan]

There would be an easy way to test whether the flapper is as much of a restriction as I suggested it was, simply unhook the actuator arm and wire the flapper open.

This has been tested numerous times by several people (myself included). In my case, with the flapper disconnected and tied open, I was seeing 10-15 psi of creep. With a normal connection and any setting on the MBC, boost would always rise to 22-23psi. This is with an E316g.

I started out by running from boost source straight to stock actuator, and saw "immediate" spool to around 10-11psi.... then a slow climb until 23 psi; where it would stay until falling off a bit at 6500rpm.

I then tried an actuator with the "Peepers mod" (extended throw and adjustable spring preload) and had the same issues.

After creep porting, my boost is now rock solid at 15psi with no creep at all, using the modified actuator.

BUT...

It did seem to slow down the spool somewhat, although I may be having MBC issues now (another story), and might be able to tune it out. As for where I'm at with efficiency now, I don't really know because I was never able to run at 15psi to see how much air I was flowing. After the porting I'm flowing 32lbs/min @ 15psi... but again, that doesn't tell me anything as I have no "before porting" reference.

I would be very interested to see some actual numbers as to what creep porting does to flow and efficiency. Later this week I'll try to run a couple pulls at 23 and see how it looks compared to before.

EDIT:

I would like to make two points:

1. I hogged the living s__t out of a standard 16g housing this last time to completely eliminate the creep issues, and

2. I don't see how creep porting could NOT affect turbine flow and efficiency. The entire 16G wastegate passage design just looks like an air clusterf--- waiting to happen to me , and intuition tells me that porting it to guide air toward the WG just causes a bunch of turbulence as it bangs up against that back wall leading toward the turbine convolute when the WG is closed.

It seems like someone should have come up with a flapper that sits in the "wall" of the turbine feed, and is contoured to match it. And then open downwards and into the air flow to divert it...

 

[CTP]

It seems like someone should have come up with a flapper that sits in the "wall" of the turbine feed, and is contoured to match it. And then open downwards and into the air flow to divert it...

There's something to be said for wastegate priority manifolds, especially when you're diverting the majority of your exhaust out the wastegate (like you would be at low boost on a small turbo). Obviously, your idea would be pretty much impossible for any normal person to do, but I don't see why it wouldn't work very well at controlling boost. The only problem is that the idea is to drop pre-turbo pressure with as little effect on flow into the turbine as possible. That setup would obviously have a huge effect on flow into the turbine.
Interesting idea though. Too bad we'll probably never get to see it tested.


On a side note, how are you managing to flow 32lbs/min on only 15psi on a 16g? EDIT: never mind, I see you have a GM MAF and cams.

 

[Calan]

That setup would obviously have a huge effect on flow into the turbine.

The way I'm seeing it, the flapper would have virtually no impact on turbine flow at all... almost as if there was no WG ... just a smooth cylindrical entrance to the turbine scroll. Then when the WG opened, it would interrupt flow into the scroll, and divert a majority of the air into the WG dump.

I picture it like this:

Looking into the housing from the ex mani (with the WG at the bottom)... move the flapper door up and contour it into the "cone". Then hinge it on the turbine side, opening upwards into the air flow. You could even go a step farther and put a concave contour on the back side of the flapper door

I wish I had access to a foundry, unlimited R&D funds, and lots of time on my hands

On a side note, how are you managing to flow 32lbs/min on only 15psi on a 16g? EDIT: never mind, I see you have a GM MAF and cams.

And some other little unmentioned mods that I think help a bit