2JZ JDM twins waste gate

[Johnysupra]

Ok here is my current Issue, read it over and see what you think.

Ok so its pretty common knowladge that the Internal waste gate on Jdm 2JZ twin turbos is to small. Meaning that if you go to a large open exhaust your boost becomes uncontrollable.. The common fix is a Restriction in the exhaust, but this increases spool time (well more soo then just and open exhaust.) So In order to keep the JDM twins and have the fastest spool possible these are my current two options.

#1 Remove the expansion pipe in the Exhaust manifold and weld in a flang for an external Wastegate. Which requires heating the cast iron and a special torch attachment so you dont crack the cast iron, and probably still not 100% reliable. (has been done before)

#2 Porting the Turbine housing and wastegate of the #1 turbo.. I just happen to have a turbo housing from a Broken JDM turbo next to me, and was takin a look see at it. From the looks of it the Wastegate could be opened up another 1/4inch pretty safely and still seal. plus i was noticing the inlet is on a direct 90 from the exhaust flow with square right angles.. So basicly my idea is to port the waste gate and smooth out the entrance to the hold whole leaving atleast 1/4 inch thick castiron left..

I am thinking that option 2 may be the most simple and reliable of the options.. I don't know if it has been done before.. i've only read of people mentioning "porting the turbo" which i would assume to be this idea.. Also i dont know if it would completly fix the problem.. however i can only imagine that if a restiction in the exhaust is enough to remedy boost spikes then having a 1/4inch larger wastegate would do the same ...

Looking for some thoughts from you guys. Im pretty certain i will do one or the other, atleast in the future if not right away. Or if anyone has any other ideas feel free to share. Pictures suck.. taken with web cam (The scratch marks are inside of the edge of the flap)

 

[tissimo]

#3 just enjoy the free extra boost




I choose 3

 

[Johnysupra]

More Boost= good

Turbocharger Damage resulting in no boost= Baaad.

 

[tissimo]

More Boost= good

Turbocharger Damage resulting in no boost= Baaad.

Just buy usdm twins then. I ran mine for a year @ 18 psi wiht 0 problems. They're still going fine now (sold the car 2 years ago).

 

[SupraMario]

Just buy usdm twins then. I ran mine for a year @ 18 psi wiht 0 problems. They're still going fine now (sold the car 2 years ago).

Yep, this is what I will be doing, buying a rebuilt set of USDM twins, and boosting away with 3" pipe all the way to the exhaust.

 

[Johnysupra]

Yeah I know thats an option but everyone does that. I think he JDMs with a modifed wastegate would compete with USDMs

 

[tturnpaw]

You could always remove the downpipe assy altogether and build your own with wg flange on it and remove the old ones.

 

[tissimo]

Yeah I know thats an option but everyone does that. I think he JDMs with a modifed wastegate would compete with USDMs

No, you're worried about running 16 psi on them, why would you turn them up to 18 to compete with the usdms? So they dont compete.

The biggest benifit of the USDM twins is the y pipe setup imo. Its a MUCH better design not to mention the DP flange is a 3" hole vs the JDMs 2.5" hole.

 

[Johnysupra]

No, you're worried about running 16 psi on them, why would you turn them up to 18 to compete with the usdms? So they dont compete.

The biggest benifit of the USDM twins is the y pipe setup imo. Its a MUCH better design not to mention the DP flange is a 3" hole vs the JDMs 2.5" hole.

I wasn't worried about running 16 PSI on them.. And this has gone way off subject. No one has even responded to my post, other then to say use USDM twins.. Next post will surely be "Just go single".

 

[Dylan JZ]

just go single..

 

[tissimo]

I wasn't worried about running 16 PSI on them.. And this has gone way off subject. No one has even responded to my post, other then to say use USDM twins.. Next post will surely be "Just go single".

Then why do you want to run lower boost? 3" exhaust on the JDM twins will creep to like 14-16 psi. Just like the USDM2j twins, 1jz stock twins or CT26 on a 7m with a free flowing exhaust, you'll get a few psi increase in boost over stock. Its not like itll boost 20+ psi or anything.

 

[Johnysupra]

I wanna Run like 18-20 Through a 3" electric cut out, or 3" exhaust.
Everything i've read on the "Other forum" Says the JDM's will continue to boost, well past 20psi without a restrictor. I've heard of several people running over 18 psi on JDM's and them lasting awhile if their in good shape, but they all used restrictor rings that i know of.

 

[tissimo]

I wanna Run like 18-20 Through a 3" electric cut out, or 3" exhaust.
Everything i've read on the "Other forum" Says the JDM's will continue to boost, well past 20psi without a restrictor. I've heard of several people running over 18 psi on JDM's and them lasting awhile if their in good shape, but they all used restrictor rings that i know of.

I've never heard that, and I have seen a few JDM twin cars.

 

[Johnysupra]

I've never heard that, and I have seen a few JDM twin cars.

Which part ? The 18psi on JDMs or the boost issue ??

I'm not trying to discount you Opinion Tissimo you've obviously spent alot more time on the boards then me. Its just that I like doing some things different that everyone else. I may just end up going with the US turbos. I swing back and forth on which i want all the time. I just like trying new things ya know?

Do you have something to remove fuel cut ?? and if so what type? (BCC/FCD etc)

 

[tissimo]

overboosting issue (20+ psi)

You can port the wastegates if you wish, it just seems like a waste of time imo.

Aristo fuel cut is ~ 15 psi. A FCD/BCC will get rid of it (sw20 one, same as the MKIV supra/1jz). Just make sure to watch you're A/Fs when using a fcd and not overboost. IMO best way to move boost cut around is a SAFC or the like. It wont remove it completely but you can tune the car and will give you a little head room. When you hit fuel cut you know you're out of fuel and need to upgrade your injectors.

 

[NewGen]

Aristo fuel cut is ~ 15 psi. A FCD/BCC will get rid of it (sw20 one, same as the MKIV supra/1jz). Just make sure to watch you're A/Fs when using a fcd and not overboost. IMO best way to move boost cut around is a SAFC or the like. It wont remove it completely but you can tune the car and will give you a little head room. When you hit fuel cut you know you're out of fuel and need to upgrade your injectors.

I know this is getting alittle off topic but If you run an emanage ultimate can you get around fuel cut or do you have to run a FCD with it?

Also if your getting enough air flow to cause the turbos to over boost why would you run a cut out? Its not like you need more airflow.

 

[staticpage]

personally I would try and port the internal wastegate. It seems to me that it would allow a lot more gas to travel thou the hole even opening it up just 1/4 in. If this is done I would take care in rounding the hole edge. also maybe the wastegate flapper arm can be cut off and a new larger one welded on? I don't know how much room is in there to work with but I would try it. Then you could open the hole even greater.

looking at pic of the turbo i think it would be very time consuming to weld a larger flapper on. the housing would need to be enlarged on the outside edge. but its something i could have done for a lot of money or one could just spend all week with a die grinder and a welder.

 

[Big Rob]

Jump on Toymods and the supraforums.com.AU. Toymods there was a topic where one guy ported and smoothed the waste gate, supraforums there was a discussion where a person enlarged the wastegate and high flowed a set of JDM's.

 

[Wills7MGTE]

I find it ironic the JZ's for japan were crap compared to the USDM, the 1jz twins destroy themselves and the 2JZ's twins cant flow as well reliably as the USDM's kinda funny you'd think we'd get the shaft, LOL

 

[tturnpaw]

I find it ironic the JZ's for japan were crap compared to the USDM, the 1jz twins destroy themselves and the 2JZ's twins cant flow as well reliably as the USDM's kinda funny you'd think we'd get the shaft, LOL

We did. We got 7ms instead of 1js. Haha.