1991 Supra

[HKS1991]

Hello all. First timer here hoping to find some other owners alike. I own a 1991 7MGTE and I need some input. I reubuilt the top end of my motor (almost every seal is brand new) I got the head a comp. valve job and polished the ports. Got a other couple mods lika a larger FMI, intake, exhaust and a BOV. I am interested in changing the wastegate along with the exhuast manifold. I have a greddy boost controller not hooked up as well. Does anyone have any suggestions.

[MkIII_Driver]

First did you put a metal head gasket in it?

second if you really want the power and have the MHG in you could go t4 headers as well as new turbo. however! this can be very costly. now im not aware of any non-custom headers that apply to the stock turbo, or atleast i havent taken the time to look them up because i am in the process crafting a stock header. Im not sure if its gonna work though. hopefully someone else will post on here so i can get the info as well.

THIRD! the greddy boost controller that you have should be put in, but dont over boost it of course. im currently running 12s on my ct-26(turbo)

[Wolfie]

I have a MA71 1991 mkIII

Also a MHG is only required for high boost...I havnt put one in because i'm getting a LARGE turbo conversion or possibly swapping to a 1JZ or 2JZ. i didnt before because of money flow...but when i do i'm installing an APEXI PowerFC after market ECU, which is the best for the mkIII's IMO because of the simplicity of plug and tune, and they make them for the MkIII soups, 5 high power dyno runs and its tuned, unlike the other ECU's on the market.

Jeeves will prolly chime in but he mentioned to me about a new turbo elbow on the exhaust as the stock one is rather constrictive. a 3" ehaust, pod filter,and if not done go for a MHG and arp studs on the head.

got any pix of your soup? I'm also getting in a Bomex body kit for my mkIII

[HKS1991]

Originally Posted by MkIII_Driver

First did you put a metal head gasket in it?

second if you really want the power and have the MHG in you could go t4 headers as well as new turbo. however! this can be very costly. now im not aware of any non-custom headers that apply to the stock turbo, or atleast i havent taken the time to look them up because i am in the process crafting a stock header. Im not sure if its gonna work though. hopefully someone else will post on here so i can get the info as well.

THIRD! the greddy boost controller that you have should be put in, but dont over boost it of course. im currently running 12s on my ct-26(turbo)

I did not put a metal MHG in because of money and time constraints. I put in a composite one that was better than factory. What i am ultimatley trying to do is uprade as mush as possible before I replace the turbo and ECU. I am waiting to hook up the boost controller because I want to know if an aftermarket wastegate can be put on the with the stock turbo manifold. Or should I wait until I have everything before going big?

[Wolfie]

If you go big do it all in one hit., so it can all be tuned for a new ECU and such. For ECU i recommend APEXI, the best for a mkIII IMHO.

[Jeeves]

Originally Posted by HKS1991

I did not put a metal MHG in because of money and time constraints. I put in a composite one that was better than factory. What i am ultimatley trying to do is uprade as mush as possible before I replace the turbo and ECU. I am waiting to hook up the boost controller because I want to know if an aftermarket wastegate can be put on the with the stock turbo manifold. Or should I wait until I have everything before going big?

You can't quite do it this way.

The reason being is that the stock turbo is internally gated. While you could pull the line to the stock wastegate (forcing it permanently closed) and hackjob a wastegate onto the manifold, it would do you no good. The stock wastegate is a limitation of the turbo. It takes internal room, and is rather limiting. Besides that, to upgrade, you would [probably] swap to a newer manifold and a different turbo, hence making all your hard work useless.

If you're going to upgrade it, do it all at once. Do Headgasket + all machining, New Turbo, External Wastegate, Manifold, Boost Controller.

[HKS1991]

Originally Posted by Jeeves

You can't quite do it this way.

The reason being is that the stock turbo is internally gated. While you could pull the line to the stock wastegate (forcing it permanently closed) and hackjob a wastegate onto the manifold, it would do you no good. The stock wastegate is a limitation of the turbo. It takes internal room, and is rather limiting. Besides that, to upgrade, you would [probably] swap to a newer manifold and a different turbo, hence making all your hard work useless.

If you're going to upgrade it, do it all at once. Do Headgasket + all machining, New Turbo, External Wastegate, Manifold, Boost Controller.

I figured that would be the case because I did notice the lacking of an external wastegate when I had the top end pulled apart. Now will the Greddy boost controller hook up to this wastegate? If so what is the min/max I would wnat to push through the CT-26?

[Jeeves]

As long as a turbocharged system has a wastegate a boost controller will work fine in the system.
The minimum is the stock setting, which depends on your altitude but should be set at 6.8psi. The maximum is 12psi, you WILL hit fuel cut at that point. That means the fuel system cannot supply enough fuel for the boost level.

However, detonation in stock form is quite prevailant at 12psi and this is the cause of blown head gaskets.