I have now budded my head with several people who insist that EVO 16G can benefit from a 34mm flapper upgrade. Well, I will give them the fact that this turbo can definitely use a wastegate upgrade, but it is my contention that 34mm flapper is NOT the way to go!

I am not sure if you can see from the photo, but the machined area (on which flapper sits) is raised ~ ½” above the main casting body. You can also see just how close the stock flapper (30mm) comes to that edge!

A 34mm valve completely covers that machined area! In order to fully utilize that valve you leave a wall thickness of less than 1mm! I am sure that this turbine housing is made from a superior material than the good old 16Gs, but I can not possibly imagine that it would last without cracking for anything more than a few thousand miles, if you make it that thin!

I would not be very comfortable opening this opening much past 30mm. Which brings me to my original point: this turbine housing does not allow you to use 34mm upgrade!

So at that rate, I would only recommend porting it to maximize the stock WG (29-29.5mm). This would be slightly smaller than the largest I would recommend to port out on a 34mm valve (30-30.5mm). But then, you are not going to have a huge obstruction in the way of your exhaust gases. And if this mild porting does not work, I would recommend converting to the exhaust WG, over going to the 34mm upgrade.

Has anyone racked on some serious miles on EVO16G with a 34mm WG AND had a chance to look it over? Can you report on how it is holding up?

good post...also wondering the same. I might buy a used evo 16g w/o the flapper mod and it'd be great to know whether I should do it or not.

I have the e3b16g with the 34mm flapper mod. Slowboy did the work and it all looks good still. I only have about 3k miles on it. But I am having trouble with it blowing open under high boost (anything above 19psi), so I am going external soon. Unless you want to run 15psi on this turbo I would stay with the stock flapper and if need be later get an external.

Just my .02

Stoner said:

I have the e3b16g with the 34mm flapper mod. Slowboy did the work and it all looks good still.

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Mine too and I've got about 6500 miles on it. I had it at 19psi, but am only running 17 now. I have not had problems with it blowing open.

GPTourer said:

Mine too and I've got about 6500 miles on it. I had it at 19psi, but am only running 17 now. I have not had problems with it blowing open.

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Turn the boost up to 22psi and once you hit 22 it will drop back to 18-19psi, I bet.

Perhaps, but I only run 93 and am still on the stock side mount, so 17 is where I live, and it works fine.

I got mine from Slowboy with the 34mm flapper, I ran 20psi daily and it would hold that fine.

Sometimes it would creep up to like 24ish but I never really tried to run that much boost so I'm not sure if it would fall off or not.

Have you guys actually taken the O2 off and looked at the WG port though? I don't think he's saying they won't work, but that the sliver of a "wall" before the flapper will eventually crack or break completly off. Then you would probably run into problems like longer spool time due to the gap.

Stoner said:

Turn the boost up to 22psi and once you hit 22 it will drop back to 18-19psi, I bet.

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I have run everywhere between 12-26 psi and have never had a drop in boost. I have experienced 1-2 psi of creep when running 12psi, but never worse than that. I am running a FP EvoIII and have the 34mm flapper done by AMS, and have no complaints so far. I only have about 1500 miles on the turbo, but this makes me curious, as you brought up a good point GRNDSM.

I think one of the biggest reason for a 34mm flapper is that its the only size that I know of thats available. Its the only size flapper door we have at least.

If you are using the stock actuator, its weak and is why you can not hold boost. The PTE turbos use a 14psi spring with an adjustable rod and hold & spool much better.

I would first smooth out the inside of the wastegate hole with a dremel. That should help out a lot but if thats not enough, your options are limited to thin housing and 34mm/new PTE turbo or external WG.

I have a little over 6000 on my evo III and just took it off the other to get it retapped were i broke a bolt where it connects to the manifold. The wg passage looked fine and showed no signs of excess or any wear to be honest. The 34mm flapper doesn't help me much though because i still can't hold steady boost and have to set it about 3-4 psi below my target boost because the creep is so bad. I purchased it from SBR and they did all the porting and installed the flapper, just for comparisons sake.

I'm actually about to replace it and the manifold with a 50 trim garrett and tubular manifold with a 38mm tial because i am getting tired of trying to fix its boost creep syndrome.

superflyjmysnk said:

I have a little over 6000 on my evo III and just took it off the other to get it retapped were i broke a bolt where it connects to the manifold. The wg passage looked fine and showed no signs of excess or any wear to be honest. The 34mm flapper doesn't help me much though because i still can't hold steady boost and have to set it about 3-4 psi below my target boost because the creep is so bad. I purchased it from SBR and they did all the porting and installed the flapper, just for comparisons sake.

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We've had problems with turbos like yours that have been "ported" many times. Even if you install a 34mm flapper door, if the porting in the inlet of the turbine housing isnt done properly it will creep. You have to understand the dynamics of airflow and port in such a way that you channel air toward the flapper door for it to even be able to waste much air out.

I've many times removed exhaust housings that creep past 18 psi, done another 30 minutes worth of porting work, and put them back on and have them hold a rock solid 14 psi or less, even in sub freezing weather here in Chicago.

I read somewhere awhile back about "stepping" the material between the wg passage and the turbine area to create more backpressure at the turbine wheel but i'm just going to switch to another turbo. I was just going to weld the tial onto the stock manifold and weld the internal wg shut but i have a little more disposable income here lately and i've heard a lot of good things about the 50 trim. If anyone want's my evo III turbo i should be getting the other turbo installed in about two weeks or so.

superflyjmysnk said:

I read somewhere awhile back about "stepping" the material between the wg passage and the turbine area to create more backpressure at the turbine wheel but i'm just going to switch to another turbo. I was just going to weld the tial onto the stock manifold and weld the internal wg shut but i have a little more disposable income here lately and i've heard a lot of good things about the 50 trim. If anyone want's my evo III turbo i should be getting the other turbo installed in about two weeks or so.

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When you have it off the car and ready to go, send me a PM. I usually know a few people looking for them. Ill try to get ya hooked up with someone.
Eric

>I don't think he's saying they won't work, but that the sliver of a "wall" before the flapper
>will eventually crack or break completly off. Then you would probably run into
>problems like longer spool time due to the gap.

You are correct, I am not getting into the effectiveness of 34mm valve, peoples results seem to vary a great deal! The performance of 34mm flapper valve modification will depend on many other factors:

- restriction presented by your exhaust system (less “back pressure” = more tendency to boost creep)
- Pre-load on the valve (more pre-load = less tendency to “blow open” and more tendency to creep)
- O2 houisng design and/modifications (there are countless variations of those).
- Type of WG actuator (though, most people use only one type)

I am simply approaching it from the perspective of how much material is in that housing available for removal.

If someone shows me a 20-30k miles EVO16G housing with <.05” wall thickens in the WG passage which hasn’t cracked, I will be the first to admit that I am wrong (as well giving a big THUMBS UP to Mitsu engineers!). But unfortunately, those turbos haven’t been on the market long enough. So at this point all we can do is speculate based on previous experience.

Leon