Has anyone put in the 34mm flapper on their EvoIII Turbo? If i'm going to port my ( EvoIII turbo, EvoIII manifold and EvoIII O2 housing ), do i still need to have this34mm flapper mod done? Do u guys thing i'll be fine without it concerning boost creep? Would the 34mm mod ruin the potential of this turbo? What are the advantages/disadvantages of having the 34mm flapper put in? Should i get it done or not? Thanks.

Definatly do the mod. It is a lot easier to do it now than put it togeather and have to take it back off again. You are almost certain to get creep if you dont have the 34mm flapper. Why do you say it will ruin the potential of the turbo?? It will have no ill affects on the turbos preformance besides extending the life of it and your motor. I have the 34mm flapper with a heavily ported turbo and O2 housing with a 2.5"-3" downpipe and I can keep boost at 15 psi. I still get a little creep at 6K+ rpm but nothing major, 2 to 3psi.

Corman12345 said:

Definatly do the mod. It is a lot easier to do it now than put it togeather and have to take it back off again. You are almost certain to get creep if you dont have the 34mm flapper. Why do you say it will ruin the potential of the turbo?? It will have no ill affects on the turbos preformance besides extending the life of it and your motor. I have the 34mm flapper with a heavily ported turbo and O2 housing with a 2.5"-3" downpipe and I can keep boost at 15 psi. I still get a little creep at 6K+ rpm but nothing major, 2 to 3psi.

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A larger flapper will keep you from running high boost with the turbo at high RPMs. Force on the flapper increases with the square of the radius of the flapper. It will blow open at high RPMs and lower your boost. I ran my best mph with this turbo at 26psi with race gas in the tank. If you have a larger flapper, I doubt you would be able to hit 26psi at redline.

It is a great way to ruin a perfectly good exhaust housing, IMO.

An external gate would be ideal. However, the 34mm flapper itself is only $20-30 and is an easy fix for boost creep.

anyone else????

Last I knew putting the 34mm flapper on the EVOIII 16G was not even possible. Has anyone done this?

I put one on. Slowboy racing has them for $20. Installation was simple and straitforward. It cured all of my creep problems and had no affect on performance whatsoever besides being able to lower my boost when I want to.

http://www.dsmtuners.com/forums/showthread.php?s=&threadid=87247&highlight=mad+boost+creep

Look Here

Corman12345 said:

I put one on. Slowboy racing has them for $20. Installation was simple and straitforward. It cured all of my creep problems and had no affect on performance whatsoever

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Unless you want to run higher boost.

Kinetic racing up in BC Canada offers a 38mm flapper. It's the best thing I've done but I still creep just a little bit every so often. Without it, it's supposedly hell.

I don't have boost creep with my Evo III 16G, and I have the stock flapper valve. A larger valve just makes it harder for the exhaust to make it around the valve. 38mm is too big.

I do have a 122performance.com 2.5" tubular O2 housing though. Internal dump. That is what did it for me.

If the concern is for running high boost ( 23-25+psi ) then you should not be running any 16G variant. Get the 34mm flapper mod, it is necessary to fix the flaws in the design from our good friends at MHI.

-Groomz

Groomz said:

If the concern is for running high boost ( 23-25+psi ) then you should not be running any 16G variant. Get the 34mm flapper mod, it is necessary to fix the flaws in the design from our good friends at MHI.

-Groomz

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Uhh, why? It works. 26psi got me 44.1lbs/min out of the Evo III 16G. A 50-trim would probably see that airflow rate at what, 24psi on a well modded car? A turbo that spools like this Evo III and can put out that airflow at high boost is the best of both worlds.

The flaw isn't in the wastegate flapper, it is in the O2 housings that people are putting on this turbo. Another way to get rid of creep with this turbo is to port the inlet area above the wastegate to give exhaust a clearer path to the wastegate.

But with a larger flapper, you are crippling the turbo and ruining a perfectly good 7cm exhaust housing. I'm just telling you that I wouldn't do it, and it wasn't even needed to get rid of creep in my case.

ShapeGSX said:

Uhh, why? It works. 26psi got me 44.1lbs/min out of the Evo III 16G. A 50-trim would probably see that airflow rate at what, 24psi on a well modded car? A turbo that spools like this Evo III and can put out that airflow at high boost is the best of both worlds.

The flaw isn't in the wastegate flapper, it is in the O2 housings that people are putting on this turbo. Another way to get rid of creep with this turbo is to port the inlet area above the wastegate to give exhaust a clearer path to the wastegate.

But with a larger flapper, you are crippling the turbo and ruining a perfectly good 7cm exhaust housing. I'm just telling you that I wouldn't do it, and it wasn't even needed to get rid of creep in my case.

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I prefer to see you as an exemption to the rule. Not many other DSM'ers are flowing that amount on the Evo III. Excellent results no doubt, but any turbo can be pushed past its designed flow rating. Better have one hell of an intercooler at those outlet temps too.

-Groomz

I don't see why my results should be special. Others have pushed over 40lb/min with the Evo III. At the moment, I'm just the "exception" because I was a relatively early adopter of the turbo. Give others a chance to catch up, and I bet they will.

A local guy ran 112mph in his 92 GSX with an Evo III16G, BR FMIC, 550s, a SAFC and a 2.5" turbo-back on his first time at the track with the setup.

It took me 3 years to get to that point with my small 16G (with a larger flapper and boost drop in the upper RPMs I might add), and he got there on his 3rd run with the Evo III. He has a lot more in that car. He hasn't even upgraded his cams yet!

And my "one hell of an intercooler" is an 18" wide RRE top/bottom flow Griffen IC with spearco end tanks. Whoohoo! It's the best! It's huge! Wanna buy it?

For the sake of clear information:

ShapeGSX is right, Groomz is wrong.

1. You don't want to do the bigger flapper mod on any turbo besides a 14b. It will generally limit you to around 18-20 psi, which is pretty crappy even on a small 16g. On a big 16g or an EvoIII, it totally eliminates any chance of good performance that you had.

2. There is no reason not to run 25 psi on that turbo. It's not even really a 16g. Think about it this way, if the regular 16g is happy at 22 psi and the 20g is happy at 28, then why the heck wouldn't the EvoIII 16g, which is about halfway between those two in size, be happy halfway between those boost pressures? Oversimplified, yes, but think about it. It loves the 24-25 psi.

3. The 1992 GSX that Josh is talking about ran 112 mph his first time racing in about a year. Not only that, but he wasn't tuning. He didn't even have his datalogger with him!

Not always the case, I can still run 26+ psi easy at redline with the 34mm flapper and the wastegate hole ported to 31mm. I also ported the hot side housing outlet and did tons of porting on the evo o2 housing. no clip either

ShapeGSX said:

I don't see why my results should be special. Others have pushed over 40lb/min with the Evo III. At the moment, I'm just the "exception" because I was a relatively early adopter of the turbo. Give others a chance to catch up, and I bet they will.

A local guy ran 112mph in his 92 GSX with an Evo III16G, BR FMIC, 550s, a SAFC and a 2.5" turbo-back on his first time at the track with the setup.

It took me 3 years to get to that point with my small 16G (with a larger flapper and boost drop in the upper RPMs I might add), and he got there on his 3rd run with the Evo III. He has a lot more in that car. He hasn't even upgraded his cams yet!

And my "one hell of an intercooler" is an 18" wide RRE top/bottom flow Griffen IC with spearco end tanks. Whoohoo! It's the best! It's huge! Wanna buy it?

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Exception may be a poor word choice, how about pioneer? I have certainly regained faith in MHI and the 16G's from your results. Most people slap on a 16G and say they are disappointed after a few days. The turbo is only one part, you have to build a complete setup! An important part, but not the only part. Now why won't MHI release a flow map? Hmmm...

-Groomz

kpt4321 said:

For the sake of clear information:

ShapeGSX is right, Groomz is wrong.

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The 34mm flapper would not be necessary if the porting were done correctly. Most DIY jobs are poorly done and some shops selling them are just giving them a one over with a 180 grit sander. Wrong is such a strong word.

-Groomz

Corman12345 said:

Not always the case, I can still run 26+ psi easy at redline with the 34mm flapper and the wastegate hole ported to 31mm. I also ported the hot side housing outlet and did tons of porting on the evo o2 housing. no clip either

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kpt4321 said:

1. You don't want to do the bigger flapper mod on any turbo besides a 14b. It will generally limit you to around 18-20 psi,

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Interesting indeed....

-Groomz

Ok, so i'm not going to do the 34mm flapper mod, now which is a good place to get a good port job?? I"m going to have all 3 pieces ported (EvoIII turbo, manifold & O2 housing). Is slowboyracing good shop to have the port job done at? Buschur Racing ???

Romogst said:

Ok, so i'm not going to do the 34mm flapper mod, now which is a good place to get a good port job?? I"m going to have all 3 pieces ported (EvoIII turbo, manifold & O2 housing). Is slowboyracing good shop to have the port job done at? Buschur Racing ???

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I would recommend Forced Performance. Buschur is also a reputable shop. Not to knock on SBR, but many people who order their 16G's with porting experience some degree of creep, while all of the FP 16G owners I have asked experience zero creep. You get what you pay for basically. I only know this from searching.

-Groomz